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   2105篇
  免费   137篇
  国内免费   9篇
医药卫生   2251篇
  2023年   11篇
  2022年   11篇
  2021年   21篇
  2020年   20篇
  2019年   19篇
  2018年   35篇
  2017年   39篇
  2016年   31篇
  2015年   35篇
  2014年   61篇
  2013年   67篇
  2012年   104篇
  2011年   124篇
  2010年   72篇
  2009年   76篇
  2008年   121篇
  2007年   133篇
  2006年   146篇
  2005年   149篇
  2004年   138篇
  2003年   143篇
  2002年   151篇
  2001年   29篇
  2000年   35篇
  1999年   36篇
  1998年   39篇
  1997年   19篇
  1996年   28篇
  1995年   11篇
  1994年   12篇
  1993年   25篇
  1992年   20篇
  1991年   15篇
  1990年   13篇
  1989年   12篇
  1988年   13篇
  1987年   6篇
  1982年   15篇
  1981年   6篇
  1980年   9篇
  1975年   6篇
  1974年   8篇
  1941年   7篇
  1939年   10篇
  1938年   6篇
  1937年   5篇
  1932年   8篇
  1930年   5篇
  1928年   5篇
  1924年   5篇
排序方式: 共有2251条查询结果,搜索用时 0 毫秒
1.
OBJECTIVE: Conventional therapeutic approaches to correct ankylosed anterior teeth in infraposition require compromises involving esthetics and function. The combined approach of distraction and early orthodontic fine adjustment, not yet established as a routine, promises better results concerning the bone conditions and gingival development. CASE HISTORIES: Both female patients had suffered a trauma to the front teeth during early mixed dentition resulting in ankylosed central incisors in infraposition. At the ages of 14 years and 2 months and 15 years and 2 months, respectively, we carried out segment distraction by means of a bone-supported internal distractor followed by orthodontic fine adjustment after having shortened the consolidation phase. Both ankylosed front teeth could be successfully aligned, leading to an increase in bone and harmonization of the gingival margin in the dental arch. At ten and 14 months after the conclusion of treatment, we observed only few deviations in the dental situation compared to posttherapeutic findings. CONCLUSION: From a functional and esthetic point of view, therapy involving combined orthodontics and surgery is superior to conventional therapy. Orthodontic fine adjustment should be considered as a continuation of the distraction procedure.  相似文献   
2.
Cross sectional, M mode, and Doppler echocardiography, apexcardiography, and phonocardiography were used to characterise presystolic cardiovascular sounds in three patients with ventricular disease. Although the aetiology was different (dilated cardiomyopathy, primary pulmonary hypertension, and chronic pulmonary thromboembolic disease), in each case the presystolic sound was associated with a rapid change in acceleration of blood and with flow reversal in the superior vena cava, and could only be recorded at the right sternal edge or over the jugular veins. Such flow characteristics may be explained by a raised ventricular end diastolic pressure with reduced compliance. Use of these techniques helps to understand the cause of a previously described but little recognised heart sound, and adds weight to the interpretation of its presence in disease.  相似文献   
3.
Delay in presentation after myocardial infarction.   总被引:2,自引:0,他引:2       下载免费PDF全文
Thrombolytic therapy reduces mortality in acute myocardial infarction (AMI), giving maximal benefit with early treatment. In the UK delayed presentation after AMI may reduce the advantages of thrombolysis. To assess this, 103 patients presenting with AMI to two London Hospitals were interviewed to determine the length and cause of delay from onset of chest pain to arrival at hospital. Forty-nine per cent of patients took longer than 2 h to arrive at hospital, and 21% took longer than 4 h. Patients who contacted their general practitioner (GP) had a significantly prolonged time delay (160 mins; 65-730: median; range) compared to those who went directly to hospital by ambulance (82 mins; 15-395; P < 0.0005), or on their own (90 min; 15-855; P < 0.005). Patients calling their GP took a similar duration to decide to seek help [decision time (30 min versus 25 mins) P = NS], but significantly longer to reach hospital once the decision was made (110 min versus 56 min; P < 0.0001), than those proceeding directly to hospital. Believing the pain was cardiac in origin significantly shortened decision time (15 min versus 45 min; P < 0.05), as did knowledge of the existence of thrombolysis (15 min versus 50 min; P < 0.05) and lack of prior cardiac symptoms (18 min versus 42 min; P < 0.05). Only 14% were aware of thrombolysis. Rank correlation confirmed that decision and total delay time were age independent. Delays of this magnitude may compromise the efficiency of thrombolysis.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
4.
5.
6.
Ohne ZusammenfassungMit 7 TextabbildungenProf. Dr. Lothar Szidat, Investigador principal de Parasitologia.  相似文献   
7.
Infectious herpes simplex virus type 1 (HSV-1) recombinants were constructed by inserting the cDNA sequence of the human immunodeficiency virus type 1 (HIV-1)gag gene (from nucleotide position 675 [SacI] to 3859 [Asp 718] of the cDNA sequences of HIV-1 strain BH-10) within the DNA sequences of theBamHI DNA fragment B of the genome of an apathogenic HSV-1 strain HFEM. This HSV-1 strain possesses a 4.1-kbp deletion within theBamHI DNA fragment B between 0.762 and 0.789 map units of the viral genome, which allows the insertion of at least 4 kbp of foreign genetic material into this particular region. The DNA sequences of the immediate early promoter (IE4) of HSV-1 that were inserted upstream from thegag gene were used as a promoter. The screening of 205 virus stocks derived from individual plaques revealed that 46 recombinant viruses harbor HIV-1gag-specific DNA sequences. However, it was found that only six of the recombinant viruses are able to express thegag gene product of HIV-1. This indicates that the ratio of the positive recombination events is about 2.9%.  相似文献   
8.
9.
Summary Ten healthy sedentary subjects [age, 27.5 (SD 3.5) years; height, 180 (SD 5) cm; mass, 69.3 (SD 6.3) kg] performed two periods of maximal incremental graded cycle ergometer exercise in a supine position. Randomly ordered and using an open spirometric system, one exercise was carried out during normoxia [maximal oxygen consumption ( O2max)=38.6 (SD 3.5) ml·min–1·kg–1; maximal blood lactate concentration, 9.86 (SD 1.85) mmol·l–1; test duration, 22.6 (SD 2.7) min], the other during hypoxia [ O2max=33.2 (SD 3.2) ml·min–1· kg–1; maximal blood lactate concentration, 10.38 (SD 2.02) mmol·l–1; test duration, 19.7 (SD 2.8) min]. At rest, immediately (0 p) and 60 min (60 p) after exercise, counts of leucocyte subpopulations (flow cytometry), cortisol and catecholamine concentrations were determined. At 0 p in contrast to normoxia, during hypoxia there was no significant increase of granulocytes. There were no significant differences between normoxia and hypoxia in the increases from rest to 0 p in counts of monocytes, total lymphocytes and lymphocyte subpopulations [clusters of differentiation (CD), CD3+, CD4+CD45RO, CD4+CD45RO+, CD8+CD45RO, CD8+CD45RO+, CD3+HLA-DR+, CD3CD16/CD56+, CD3+CD16/CD56+, CD 19+] as well as adrenaline, noradrenaline and cortisol concentrations. The counts of CD3 CD16/CD56+-and CD8 +CD45RO+-cells increased most. At 60 p, CD3CD16/CD56+ and CD3+CD16/CD56+-cell counts were below pre-exercise levels and under hypoxia slightly but significantly lower than under normoxia. We concluded that the exercise-induced mobilization and redistribution of most leucocyte and lymphocyte subpopulations were unimpaired under acute hypoxia at sea level. Reduced increases of granulocyte counts during the study and reduced cell numbers of natural killer cells and cytotoxic, not major histocompatibility complex-restricted T-cells, only indicated marginal effects on the immune system.  相似文献   
10.
In this article we describe the preparation of poly[2,3,9,10,16,17,23,24-octakis(dodecyloxycarbonyl)phthalocyaninatogermoxane] by thermal polycondensation of 2,3,9,10,16,17,23,24-octakis(dodecyloxycarbonyl)phthalocyaninatogermanium dihydroxide, and its characterization. The average molar mass of the resulting polymer was determined. High molar masses are assessible, e.g., M?w = 360000 g/mol, M?n = 140000 g/mol, at moderate temperature for the polycondensation (200°C). The polymer shows a liquid-crystalline phase in an extremely large temperature range. Furthermore, Langmuir-Blodgett films (LB films) of the polymer and of the monomer were prepared and characterized. In LB films the phthalocyanine rings are preferentially oriented normal to the dipping direction.  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