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1.
Clint R. Bellenger John B. Arnold Jonathan D. Buckley Dominic Thewlis Joel T. Fuller 《Journal of Science and Medicine in Sport》2019,22(3):294-299
Objectives
To investigate whether functional overreaching affects locomotor system behaviour when running at fixed relative intensities and if any effects were associated with changes in running performance.Design
Prospective intervention study.Methods
Ten trained male runners completed three training blocks in a fixed order. Training consisted of one week of light training (baseline), two weeks of heavy training designed to induce functional overreaching, and ten days of light taper training designed to allow athletes to recover from, and adapt to, the heavy training. Locomotor behaviour, 5-km time trial performance, and subjective reports of training status (Daily Analysis of Life Demands for Athletes (DALDA) questionnaire) were assessed at the completion of each training block. Locomotor behaviour was assessed using detrended fluctuation analysis of stride intervals during running at speeds corresponding to 65% and 85% of maximum heart rate (HRmax) at baseline.Results
Time trial performance (effect size ±95% confidence interval (ES): 0.16 ± 0.06; p < 0.001), locomotor behaviour at 65% HRmax (ES: ?1.12 ± 0.95; p = 0.026), and DALDA (ES: 2.55 ± 0.80; p < 0.001) were all detrimentally affected by the heavy training. Time trial performance improved relative to baseline after the taper (ES: ?0.16 ± 0.10; p = 0.003) but locomotor behaviour at 65% HRmax (ES: ?1.18 ± 1.17; p = 0.048) and DALDA (ES: 0.92 ± 0.90; p = 0.045) remained impaired.Conclusions
Locomotor behaviour during running at 65% HRmax was impaired by functional overreaching and remained impaired after a 10-day taper, despite improved running performance. Locomotor changes may increase injury risk and should be considered within athlete monitoring programs independently of performance changes. 相似文献2.
Fu-Wei Wang Yu-Wen Chiu Ming-Shium Tu Ming-Yueh Chou Chao-Ling Wang Hung-Yi Chuang 《International archives of occupational and environmental health》2009,82(7):819-825
Purpose There has been increasing interest in the occupational health of workers in small enterprises, especially in developing countries.
This study examines the association between psychosocial job characteristics and fatigue, and attempts to identify risk factors
for fatigue among workers of small enterprises in southern Taiwan.
Methods A structured questionnaire was administered to workers receiving regular health examinations between August 2005 and January
2006. The questionnaire collected demographic information and data on working conditions, personal health status and life
styles. It also collected information on psychosocial job characteristics, fatigue and psychological distress using three
instruments.
Results A total of 647 workers with mean age of 43.7 were completed. Probable fatigue was found in 34.6% of the sample. Fatigue was
found by multiple logistic regressions to be associated with the lack of exercise, working in shifts, depression score and
lack of social support at workplace.
Conclusions This study found associations between life style, psychosocial job characteristics and fatigue. Because the high prevalence
of probable fatigue was found in such small enterprises, the authors suggest that a short interview with some quick questionnaires
in health checkup for these small enterprise workers are helpful to early detect psychosocial and fatigue problems. 相似文献
3.
4.
R. ROLLER W. GIRSCH L. HUBER M. RAB‡ H. G. STÖHR† H. SCHIMA U. M. LOSERT† E. WOLNER H. THOMA§ 《Artificial organs》1994,18(7):523-528
Abstract: This study was undertaken to survey the changes in force and fatigue of the latissimus dorsi muscle during transformation into a fatigue–resistant muscle by indirect or nervous multichannel stimulation. In sheep, a silicone chamber connected to a pressure–transducing system was implanted under the left latissimus dorsi muscle. Muscle conditioning was performed by multichannel (carousel) stimulation of the thoracodorsal nerve. The program was started with active periods of 10 min/h producing 10 tetanic contractions/min. It was increased until 70 contractions/min could be performed during 24 h. The changes of muscle force and fatigue were monitored by the silicone balloon system. After a mean period of 22 weeks, fatigue resistance was reached. The fatigueresistant muscle was able to produce a pressure of about 100 mm Hg in the balloon. After finishing the conditioning procedure, muscle forces and the fatigue resistance of the conditioned muscle were evaluated. The conditioned muscle showed only a minimal decrease of force during 20 min. Under a preload of 20 N, it exhibited a maximum tetanic tension of 95 N. 相似文献
5.
A comparison of surgeons' posture during laparoscopic and open surgical procedures 总被引:17,自引:11,他引:6
Background: There is increasing recognition of surgeons' physical fatigue in the new ergonomic environment of laparoscopic surgery. The
purpose of this study was to determine what the differences are in the movement of the surgeon's axial skeleton between laparoscopic
and open operations.
Methods: Surgeons' body positions were recorded on videotape during four laparoscopic (LAP) and six open (OP) operations. The percent
of time the head and back were in a normal, bent, or twisted position as well as the number of changes in head and back position
were tabulated using a computer program. A separate laboratory study was performed on four surgeons ``walking' a 0.5-inch
polyethylene tubing forward and backward using laparoscopic and open techniques. The movements of the surgeons' head, trunk,
and pelvis were measured using a three-camera kinematic system (Kin). The center of pressure was recorded using a floor-mounted
forceplate (Fp).
Results: In the operating room surgeons' head and back positions were more often straight in laparoscopic procedures and more often
bent in open operations. The number of changes in back position per minute were significantly decreased when the laparoscopic-only
part of surgery was analyzed. In the laboratory the subjects' head position was significantly (p= 0.02) more upright and the anteroposterior (AP) and rotational range of motion of the head was significantly reduced during
laparoscopy. Subjects' CP was more anterior and there was a significant reduction in the AP range of motion of the CP during
laparoscopy.
Conclusions: Our study suggests that surgeons exhibit decreased mobility of the head and back and less anteroposterior weight shifting
during laparoscopic manipulations despite a more upright posture. This more restricted posture during laparoscopic surgery
may induce fatigue by limiting the natural changes in body posture that occur during open surgery.
Received: 3 March 1996/Accepted: 2 July 1996 相似文献
6.
Summary Muscle force recovery from short term intense exercise was examined in 16 physically active men. They performed 50 consecutive
maximal voluntary knee extensions. Following a 40-s rest period five additional maximal contractions were executed. The decrease
in torque during the 50 contractions and the peak torque during the five contractions relative to initial torque were used
as indices for fatigue and recovery, respectively. Venous blood samples were collected repeatedly up to 8 min post exercise
for subsequent lactate analyses. Muscle biopsies were obtained from m. vastus lateralis and analysed for fiber type composition,
fiber area, and capillary density.
Peak torque decreased 67 (range 47–82%) as a result of the repeated contractions. Following recovery, peak torque averaged
70 (47–86%) of the initial value.
Lactate concentration after the 50 contractions was 2.9±1.3 mmol·l−1 and the peak post exercise value averaged 8.7±2.1 mmol·l−1. Fatigue and recovery respectively were correlated with capillary density (r=−0.71 and 0.69) but not with fiber type distribution. A relationship was demonstrated between capillary density and post
exercise/peak post exercise blood lactate concentration (r=0.64). Based on the present findings it is suggested that lactate elimination from the exercising muscle is partly dependent
upon the capillary supply and subsequently influences the rate of muscle force recovery.
Dr. Tesch was on leave from Department of Clinical Physiology, Karolinska Hospital, Stockholm, Sweden 相似文献
7.
The purposes of this study were to apply the linear power versus inverse of time relationship to high-intensity upper-body
exercise and to assess the repeatability of the parameters critical power (CP) and anaerobic working capacity (AWC), using
limits of agreement (Bland and Altman 1986). Sixteen active male subjects (aged 20–34 years), performed two sets of five constant-power
exercises on an adapted cycle ergometer. There were no significant differences between mean estimates of CP [96 (16) W and
95 (17) W] and AWC [7457 (2011) J and 7608 (1684) J] from the first and second sets of bouts. Despite the lack of systematic
bias, there was evidence of large random error. Ratio limits of agreement for time to exhaustion during constant-power exercises
suggested that a repeat measurement might be expected in 95% of cases to be between 0.64 and 1.59 times the original measurement.
The 95% limits of agreement for CP were –15 W to +17 W. The ratio limits of agreement for AWC suggest that in 95% of cases
a repeat measurement might be between 0.57 and 1.67 times the original estimate. The results of this study suggest a poor
repeatability of constant-power upper-body exercises to exhaustion, which may contribute to a poor repeatability of CP and
AWC determined from the linear power versus inverse of time model.
Electronic Publication 相似文献
8.
The effects of isometric contraction (66% of maximal force) and recovery on glycogen synthase fractional activity (GSF) in human skeletal muscle have been studied. Biopsies were taken from the quadriceps femoris muscle at rest, at fatigue and 5 min postexercise on two occasions: after one of the contractions, the circulation to the thigh was occluded during the 5 min recovery (OCC), and after the other contraction, the circulation was intact (control, CON). During CON, GSF decreased from (mean ± SE) 0.34±0.05 at rest to 0.24±0.02 at fatigue and then increased to 0.74±0.04 at 5 min postexercise; corresponding values for OCC were 0.37±0.04, 0.25±0.04 and 0.48±0.05 (P<0.001 vs. CON for 5 min postexercise only). Compared with the value at fatigue, protein phosphatase activity (PP) increased by 79±16% during CON recovery (P<0.01), whereas no change was observed during OCC recovery. Uridine diphosphate glucose increased by approximately 2.5-fold at fatigue, remained elevated during OCC recovery, but reverted to the preexercise level during CON recovery (P<0.001 vs. OCC recovery). Glucose 6-P increased approximately 5-fold at fatigue and was higher at 5 min postexercise in OCC vs. CON recovery (8.6±1.5 vs. 4.1±0.9 mmol/kg dry wt; P<0.01). It is concluded that the rapid increase in GSF after intense exercise with an intact circulation may be at least partly attributed to an increase in the specific activity of PP. The increase in GSF during recovery in OCC may be at least partly attributed to the high glucose 6-P content in vivo, which enhances the substrate suitability of GS for PP. Thus, separate mechanisms exist for the activation of PP and GS during recovery from intense short term exercise. 相似文献
9.
It has been suggested that a critically high body core temperature may impair central neuromuscular activation and cause fatigue. We investigated the effects of passive hyperthermia on maximal isometric force production (MVC) and voluntary activation (VA) to determine the relative roles of skin (Tsk) and body core temperature (Tc) on these factors. Twenty-two males [O2max=64.2 (8.9) ml kg–1 min–1, body fat=8.2 (3.9)%] were seated in a knee-extension myograph, then passively heated from 37.4 to 39.4°C rectal temperature (Tre) and then cooled back to 37.4oC using a liquid conditioning garment. Voluntary strength and VA (interpolated twitch) were examined during an isometric 10-s MVC at 0.5°C intervals during both heating and cooling. Passive heating to a Tc of 39.4oC reduced VA by 11 (11)% and MVC by 13 (18)% (P<0.05), but rapid skin cooling, with a concomitant reduction in cardiovascular strain [percentage heart rate reserve decreased from 64 (11)% to 29 (11)%] and psychophysical strain did not restore either of these measures to baseline. Only when cooling lowered Tc back to normal did VA and MVC return to baseline (P<0.05). We conclude that an elevated Tc reduces VA during isometric MVC, and neither Tsk nor cardiovascular or psychophysical strain modulates this response. Results are given as mean (SD) unless otherwise stated. 相似文献
10.
The purpose of the present study was to investigate motor unit (MU) recruitment and firing rate, and the MU action potential
(MUAP) characteristics of the human supraspinatus muscle during prolonged static contraction and subsequent recovery. Eight
female subjects sustained a 30° shoulder abduction, requiring 11–12% of maximal voluntary contraction (MVC), for 30 min. At
10 and 30 min into the recovery period, the shoulder abduction was repeated for 1 min. The rating of perceived exertion for
the shoulder region increased to “close to exhaustion” during the prolonged contraction, and the surface electromyography
(EMG) recorded from the deltoid and trapezius muscles showed signs of local muscle fatigue. From the supraspinatus muscle,
a total of 23,830 MU firings from 265 MUs were identified using needle electrodes. Of the identified MUs, 95% were continuously
active during the 8-s recordings, indicating a low degree of MU rotation. The mean (range) MU firing rate was 11.2 (5.7–14.5) Hz,
indicating the relative force contribution of individual MUs to be larger than the overall mean shoulder muscle load. The
average MU firing rate remained stable throughout the prolonged abduction, although firing rate variability increased in response
to fatigue. The average concentric MUAP amplitude increased by 38% from the beginning (0–6 min) to the end (24–29 min) of
the contraction period, indicating recruitment of larger MUs in response to fatigue. In contrast, after 10 min of recovery
the average MU amplitude was smaller than seen initially in the prolonged contraction, but not different after 30 min, while
the MU firing rate was higher during both tests. In conclusion, MU recruitment plays a significant role during fatigue, whereas
rate coding has a major priority during recovery. Furthermore, a low degree of MU rotation in combination with a high relative
load at the MU level may imply a risk of overloading certain MUs during prolonged contractions.
Accepted: 6 June 2000 相似文献