首页 | 本学科首页   官方微博 | 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   747154篇
  免费   51760篇
  国内免费   1443篇
耳鼻咽喉   9611篇
儿科学   24581篇
妇产科学   18739篇
基础医学   116060篇
口腔科学   20436篇
临床医学   69823篇
内科学   142203篇
皮肤病学   16859篇
神经病学   53653篇
特种医学   26515篇
外国民族医学   77篇
外科学   107754篇
综合类   15563篇
现状与发展   2篇
一般理论   202篇
预防医学   56206篇
眼科学   17181篇
药学   56825篇
  3篇
中国医学   2425篇
肿瘤学   45639篇
  2021年   6252篇
  2019年   6196篇
  2018年   8757篇
  2017年   6802篇
  2016年   7596篇
  2015年   8476篇
  2014年   11518篇
  2013年   17270篇
  2012年   23357篇
  2011年   24535篇
  2010年   14269篇
  2009年   13426篇
  2008年   22733篇
  2007年   24466篇
  2006年   24945篇
  2005年   23439篇
  2004年   22900篇
  2003年   21674篇
  2002年   20982篇
  2001年   36687篇
  2000年   37152篇
  1999年   30736篇
  1998年   8342篇
  1997年   7061篇
  1996年   7333篇
  1995年   6975篇
  1994年   6355篇
  1993年   5876篇
  1992年   23162篇
  1991年   23116篇
  1990年   22481篇
  1989年   22242篇
  1988年   20215篇
  1987年   19561篇
  1986年   18594篇
  1985年   17450篇
  1984年   12876篇
  1983年   10917篇
  1982年   6146篇
  1979年   11623篇
  1978年   8233篇
  1977年   6941篇
  1976年   6680篇
  1975年   7338篇
  1974年   8571篇
  1973年   8201篇
  1972年   7708篇
  1971年   7153篇
  1970年   6908篇
  1969年   6335篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
44.
45.
46.
OBJECTIVE: To evaluate the reproducibility of sonographic measurement of the lower uterine segment in pregnant women at term. METHODS: Two independent observers performed transabdominal sonography on 129 women between 36 and 38 weeks of gestation who had had a previous Cesarean section. Sonography was performed when the patients had a full and a half-full bladder; in 100 patients, the measurements were also performed transvaginally, with the patients having an empty bladder. Agreement was quantified by the intraclass correlation coefficient and, using a cut-off of 3.5 mm, by the kappa coefficient. RESULTS: The intraobserver agreement was generally high (intraclass correlation coefficient > 0.90). The interobserver agreement was higher on transvaginal (intraclass correlation coefficient, 0.94) compared with transabdominal (0.70 and 0.84, with full and half-full bladder, respectively) ultrasound. The kappa coefficient was 0.75 transvaginally, compared with 0.34 and 0.54 using the transabdominal approach, with full and half-full bladder, respectively. CONCLUSION: The agreement between two observers for sonographic transvaginal measurement of the lower uterine segment can be considered good, compared with poor to moderate agreement using the transabdominal approach.  相似文献   
47.
Mucosal trypsin, a protease-activated receptor (PAR) stimulant, may have an endogenous bronchoprotective role on airway smooth muscle. To test this possibility the effects of lumenal trypsin on airway tone in segments of pig bronchus were tested. Bronchial segments from pigs were mounted in an organ chamber containing Kreb's solution. Contractions were assessed from isovolumetric lumen pressure induced by acetylcholine (ACh) or carbachol added to the adventitia. Trypsin, added to the airway lumen (300 microg x mL(-1)), had no immediate effect on smooth muscle tone but suppressed ACh-induced contractions after 60 min, for at least 3 h. Synthetic activating peptides (AP) for PAR1, PAR2 or PAR3 were without effect, but PAR4 AP caused rapid, weak suppression of contractions. Lumenal thrombin was without effect and did not prevent the effects of trypsin. Effects of trypsin were reduced by N(omega)-nitro-L-arginine methyl ester but not indomethacin. Trypsin, thrombin and PAR4 AP released prostaglandin E2. Adventitially, trypsin, thrombin and PAR4 AP (but not PAR2 AP) relaxed carbachol-toned airways after <3 min. The findings of this study show that trypsin causes delayed and persistent bronchoprotection by interacting with airway cells accessible from the lumen. The signalling mechanism may involve nitric oxide synthase but not prostanoids or protease-activated receptors.  相似文献   
48.
The incidence of asthma has been reported to be associated with obesity. An alternative analysis, of net change in prevalence, does not require exclusion of those with asthma at baseline. Follow-up data were obtained from 9,552 participants in the European Community Respiratory Health Survey and the Swiss cohort Study on Air Pollution and Lung Disease in Adults. Incidence of asthma was analysed by proportional hazards regression, and net changes in symptoms and asthma status by generalised estimating equations, by obesity group. Incidence and net change in ever having had asthma were greater in females than in males, and in participants who remained obese compared with those who were never obese (hazard ratio 2.00, 95% confidence interval 1.25-3.20; excess net change 2.8%, 0.4-5.3% per 10 yrs). The effect of being obese on net change in diagnosed asthma was greater in females than in males, but for net change in wheeze without a cold it was greater in males. The present results are consistent with asthma being more frequently diagnosed in females, especially obese females. These findings may help to explain the reports of a stronger association between asthma and obesity in females than in males.  相似文献   
49.
A rapid procedure for determining angiotensin II in the blood by inverse voltammetry using a TA-2 device (Tekhnoanalit Company, Tomsk) with a graphite electrode has been developed. The results of analyses using the proposed technique agree with the clinical data. The rapid analytical procedure favors optimization of cardiotropic drug therapy. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 12, pp. 54–56, December, 2006.  相似文献   
50.
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