首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   565篇
  免费   70篇
  国内免费   68篇
生物科学   703篇
  2024年   4篇
  2023年   13篇
  2022年   23篇
  2021年   24篇
  2020年   24篇
  2019年   22篇
  2018年   19篇
  2017年   23篇
  2016年   20篇
  2015年   30篇
  2014年   27篇
  2013年   48篇
  2012年   33篇
  2011年   36篇
  2010年   37篇
  2009年   34篇
  2008年   27篇
  2007年   32篇
  2006年   21篇
  2005年   26篇
  2004年   17篇
  2003年   15篇
  2002年   21篇
  2001年   16篇
  2000年   10篇
  1999年   6篇
  1998年   6篇
  1997年   17篇
  1996年   6篇
  1995年   8篇
  1994年   7篇
  1993年   10篇
  1992年   5篇
  1991年   5篇
  1990年   4篇
  1989年   5篇
  1988年   4篇
  1987年   2篇
  1986年   1篇
  1985年   2篇
  1984年   4篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1979年   2篇
  1975年   1篇
  1974年   1篇
排序方式: 共有703条查询结果,搜索用时 15 毫秒
1.
The energetics of middle-distance running   总被引:2,自引:0,他引:2  
In order to assess the relative contribution of aerobic processes to running velocity (v), 27 male athletes were selected on the basis of their middle-distance performances over 800, 1500, 3000 or 5000 m, during the 1987 track season. To be selected for study, the average running velocity (v) corresponding to their performances had to be superior to 90% of the best French v of the season. Maximum O2 consumption (VO2max) and energy cost of running (C) had been measured within the 2 months preceding the track season, which, together with oxygen consumption at rest (VO2rest) allowed us to calculate the maximal v that could be sustained under aerobic conditions: vamax = (VO2max - VO2rest) x C-1. The treadmill running v corresponding to a blood lactate of 4 mmol.l-1 (vla4), was also calculated. In the whole group, C was significantly related to height (r = -0.43; P less than 0.03). Neither C nor VO2max (with, in this case, the exception of the 3000 m athletes) were correlated to v. On the other hand, vamax was significantly correlated to v over distances longer than 800 m. These v were also correlated to vla4. However vla4 occurred at 87.5% SD 3.3% of vamax, this relationship was interpreted as being an expression of the correlation between vamax and v. Calculation of vamax provided a useful means of analysing the performances. At the level of achievement studied, v sustained over 3000 m corresponded to vamax.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
2.
The purpose of the current study was to investigate whether or not the FABP2 gene polymorphism modulated obesity indices, hemodynamic factor, blood lipid factor, and insulin resistance markers through 12-week aerobic exercise training in abdominal obesity group of Korean mid-life women. A total of 243 abdominally obese subjects of Korean mid-life women voluntarily participated in aerobic exercise training program for 12 weeks. Polymerase Chain Reaction with Restriction Fragment Length Polymorphism (PCR-RFLP) assay was used to assess the FABP2 genotype of the participants (117 of AA homozygotes, 100 of AT heterozygotes, 26 of TT homozygotes). Prior to the participation of the exercise training program, baseline obesity indices, hemodynamic factor, blood lipid factor, and insulin resistance markers were measured. All the measurements were replicated following the 12-week aerobic exercise training program, and then the following results were found. After 12-week aerobic exercise training program, wild type (Ala54Ala) and mutant type (Ala54Thr+Thr54Thr) significantly decreased weight (P > .001), BMI (P > .001), %bf (P > .001), waist circumference (P > .001), WHR (P > .001), muscle mass (wild type p < .022; mutant type P > .001), RHR (P > .001), viseceral adipose area (wild type p < .005; mutant type P > .001), subcutaneous area (P > .001), insulin (wild type p < .005; mutant type P > .001) and significantly increased VO2max (P > .001). And wild type significantly decresed NEFA (P > .05), glucose (P > .05), OGTT 120min glucose (P > .05) and significantly increased HDLC (p > .005). Mutant type significantly decreased SBP (P > .001), DBP (P > .01), TC (P > .01), LPL (P > .05), LDL (P > .001), HOMA index (P > .01). The result of the present study represents that regular aerobic exercise training may beneficially prevent obesity index, blood pressure, blood lipids and insulin resistance markers independent of FABP Ala54Thr wild type and mutant type.  相似文献   
3.
The location of the dissimilatory nitrite reductase and orientation of its reducing site of the Grampositive denitrifier, Bacillus firmus NIAS 237 were examined. Approximately 90% of the total dissimilatory nitrite reductase activity with ascorbate-reduced phenazine methosulfate (PMS) as the electron donor was on the protoplast membrane. Nitrite induced with intact Bacillus cells an alkalinization in the external medium, followed by acidification. The electron transfer inhibitor, 2-heptyl-4-hydroxyquinoline-N-oxide, which blocked nitrite reduction with endogenous substrates, inhibited the acidification, but not the alkalinization. Alkalinization was not affected with ascorbate-reduced PMS as the artificial electron donor. This indicated that the alkalinization is not associated with proton consumption outside the cytoplasmic membrane by the extracellular nitrite reduction. The dissimilatory nitrite reductase of B. firmus NIAS 237 was located on the cytoplasmic membrane, and its reducing site is suggested to be on the inner side of this membrane.Abbreviations CCCP carbonylcyanide m-chlorophenylhydrazone - HOQNO 2-heptyl-4-hydroxyquinoline-N-oxide - PMS phenazine methosulfate - H+/NO inf2 sup- ratio number of consumed protons in the external medium per one ion of NO inf2 sup- reduced  相似文献   
4.
5.
We found a nuclear RA-binding activity by using a sucrose-density-gradient assay from rat liver and testis. From the sedimentation analysis, and the comparison with cloned RARs, it is likely that these binding activities represent endogenous RARs. Furthermore we showed that these binding activities were constant irrespective of the retinoid status in the rat.  相似文献   
6.
7.
8.
The aim of this study was to investigate the effect of 12 weeks of aerobic training on the serum levels of adiponectin and leptin and on inflammatory markers of coronary heart disease in obese men. Sixteen non-athlete obese men were randomly assigned to one of two experimental groups. The experimental group underwent aerobic training consisting of three sessions per week for 12 weeks, while the control group did not participate in the training programme during the study period. Five millilitres of venous blood was taken from each participant at the beginning of the study, during week six and at the end of week 12 to measure the levels of leptin, adiponectin, C-reactive protein, interleukin-6 and tumour necrosis factor-α. The findings showed that aerobic training led to decreases in the levels of CRP (P = 0.002), IL-6 (P = 0.001) and leptin (P = 0.003) and an increase in the level of adiponectin (P = 0.002) in the experimental group relative to the control group. In addition, the level of TNF-α decreased in the experimental group after the 12-week aerobic training period, although this change was not statistically significant. According to the results of this study, regular aerobic exercise decreases the potential risk of coronary heart disease by improving the plasma levels of IL-6, adiponectin, leptin and CRP. Additionally, aerobic exercise can be used as effective non-pharmacological treatment to prevent diseases.  相似文献   
9.
Exercise plays an important role to improve cardiovascular performance. The aim of this study was to compare the effect of aerobic continuous and interval training on the left ventricular structure and function. Twenty untrained healthy male students (aged 18-22 years) were randomly divided into two groups: continuous (C; n = 10) and interval (I; n = 10). The training programme consisted of countryside jogging for 45 min during 8 weeks three times a week at 70% of maximum heart rate (MHR). In each session group C was jogging for 45 min and in group I jogging was performed in 5 nine-minute stages with a four-minute inactive rest between them. M-mode, 2-dimensional, colour and Doppler transthoracic echocardiography were performed, during resting conditions, before and after the training period. After 8-week training the end diastolic diameter, systolic blood pressure and diastolic blood pressure in groups C and I, and the posterior wall thickness and the end systolic diameter in group I showed no significant difference (P > 0.05). On the other hand, the percentage of ejection fraction and shortening fraction in groups C and I, the end systolic diameter and the posterior wall thickness in group C and the interventricular septum thickness in group I demonstrated a significant difference (P ≤ 0.05). Comparing the two groups, only the value of the interventricular septum thickness was significant (P ≤ 0.05). In general, eight-week aerobic continuous and interval training can affect left ventricular structure and function.  相似文献   
10.
反硝化细菌在污水处理作用中的研究   总被引:9,自引:0,他引:9  
反硝化细菌在污水处理过程中起到十分重要的作用。传统理论认为反硝化细菌是异养厌氧的,20世纪80年代发现了好氧反硝化细菌。最近,自养反硝化细菌的发现,特别是脱氮硫杆菌的发现引起了人们的极大兴趣。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号