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   212009篇
  免费   2832篇
  国内免费   179篇
耳鼻咽喉   1426篇
儿科学   7293篇
妇产科学   3603篇
基础医学   21211篇
口腔科学   2501篇
临床医学   14774篇
内科学   39821篇
皮肤病学   1250篇
神经病学   19098篇
特种医学   10170篇
外科学   35629篇
综合类   2480篇
预防医学   19253篇
眼科学   3159篇
药学   12174篇
中国医学   752篇
肿瘤学   20426篇
  2023年   191篇
  2022年   365篇
  2021年   676篇
  2020年   392篇
  2019年   542篇
  2018年   22486篇
  2017年   17777篇
  2016年   19991篇
  2015年   1558篇
  2014年   1646篇
  2013年   1742篇
  2012年   8481篇
  2011年   22537篇
  2010年   19673篇
  2009年   12211篇
  2008年   20831篇
  2007年   23121篇
  2006年   2094篇
  2005年   3773篇
  2004年   4976篇
  2003年   5865篇
  2002年   4048篇
  2001年   1915篇
  2000年   2004篇
  1999年   1689篇
  1998年   725篇
  1997年   633篇
  1996年   472篇
  1995年   435篇
  1994年   424篇
  1993年   347篇
  1992年   1025篇
  1991年   1008篇
  1990年   929篇
  1989年   971篇
  1988年   821篇
  1987年   735篇
  1986年   763篇
  1985年   705篇
  1984年   449篇
  1983年   394篇
  1982年   215篇
  1981年   185篇
  1979年   311篇
  1978年   247篇
  1977年   211篇
  1975年   214篇
  1974年   204篇
  1971年   176篇
  1969年   185篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The structural effect of polyanions on the binding type of methylene blue ( 1 ) was investigated spectrophotometrically. 1 was bound to poly(potassium styrenesulfonate) (PSS) and poly(sodium 4-vinylphenylsulfate) (SVS) in the dimeric or slightly aggregated form and to poly(sodium vinylsulfonate) (SVF) and poly(potassium vinyl sulfate) (PVS) in the highly aggregated (polymeric) form. It was found that the flexibility of polyanions plays an important rǒle in the aggregation of bound 1 and that the difference between ? SO and ? OSO as binding site is not a significant factor.  相似文献   
992.
This paper referred to primary Immunodeficiency diseases (PID)-malignancy association in autopsy cases in Japan. The occurrence of malignant neoplasms almost centered upon ataxia-telangiectasia among PID in Japan. It seems to be due to extremely shorter life span in Japanese patients with PID except for in those with ataxia-telangiectasia, compared with that in European and American patients. Most of the malignant neoplasms seen in Japanese patients with PID were epithelial and were seen mostly in older patients, while lymphoreticular tumors were rare. Gastric cancer was the most frequent of the epithelial tumors.  相似文献   
993.
We investigated the effects of the purified catalytic subunit (C subunit) of the cAMP-dependent protein kinase (A-kinase) on the cardiac Na+ channel currents. Single Na+ channel currents in guinea-pig ventricular myocytes were recorded using the patch clamp technique of the inside-out configuration. Application of C subunit decreased the peak average current and slowed the current decay, effects which were caused by decrease in the open probability of Na+ channels and increase in the first latency, whereas the unitary current amplitude and mean open times were not affected. We conclude that the cardiac Na+ channel is directly modulated by phosphorylation process through A-kinase.  相似文献   
994.
In the present study, small volumes of plasma were used for the measurement of bromvalerylurea (BVU), its metabolite, 3-methylbutyrylurea (MVU), and bromide in carbon tetrachloride (CCl4)-treated rats by HPLC-UV and energy dispersive X-ray spectrometry. A liquid-liquid extraction system was also investigated. BVU and MVU were extracted from 100 microl plasma samples in a single-step involving deproteination with 1 M hydrochloric acid using ethenzamide as internal standard. Samples were separated by HPLC in an acetonitrile-8 mM potassium dihydrogenphosphate buffer (35:65, v/v) mobile phase at a flow-rate of 0.4 ml/min on a 15 cm octadecylsilyl column at room temperature. Analytes were detected at a wavelength of 210 nm. The limits of quantitation for BVU, MVU and bromide are 0.1, 0.1 and 50 microg/ml, respectively. The intra-day accuracies over the range of concentrations were 95.8 to 121.1%, 97.2 to 119.7% and 96.2 to 105.8% for BVU, MVU and bromide, respectively. The inter-day accuracies were 97.7 to 115.1%, 98.3 to 111.6% and 98.3 to 102.9% for BVU, MVU and bromide, respectively. The absolute recoveries using tert.-butyl methyl ether are 96-98% for BVU and 95-98% for MVU. The decline in the plasma concentrations of BVU in olive oil-treated rats fitted a one-compartment model and the plasma MVU level reached a peak at around 1.5-2 h and then decreased gradually. The elimination of BVU in CCl4 (1 ml/kg)-treated rats was delayed and MVU production was less than that in the olive oil-treated group. However, there was no difference in the plasma levels of bromide between CCl4-treated rats and control rats. rights reserved.  相似文献   
995.
996.
BACKGROUND: Suplatast tosilate is an anti-allergic agent that suppresses cytokine production by human Th2 cells. OBJECTIVE: We investigated the effects of suplatast tosilate on the production of thymus- and activation-regulated chemokine (TARC) by T cells from allergic patients with asthma. METHODS: Purified protein derivative (PPD)-specific Th1 cell lines and Dermatophagoides farinae (Der f)-specific Th2 cell lines were established from nine patients with house dust mite-allergic asthma. The effects of suplatast tosilate on mRNA expression of TARC and protein production of TARC from antigen-specific Th1 or Th2 cell lines were investigated after stimulation with relevant antigens or phytohemagglutinin (PHA). In addition, the effects of IL-4, IL-10, and IFN-gamma on TARC production by Der f-specific Th2 cell lines in the presence or absence of suplatast tosilate were studied. RESULTS: Although PPD-specific Th1 cell lines did not produce TARC after stimulation with PPD antigen or PHA, stimulation of Der f-specific Th2 cell lines with Der f antigen or PHA increased production of TARC. Suplatast tosilate significantly and dose-dependently inhibited production of TARC by Der f-specific Th2 cell lines stimulated with either Der f antigen (76.5% inhibition at 100 microg/mL, P < 0.01) or PHA (81.9% inhibition at 100 microg/mL, P < 0.01). TARC production by Der f-specific Th2 cell lines was significantly increased only by activation with IL-4 but not with IL-10 or IFN-gamma; this increase in TARC production was significantly inhibited by suplatast tosilate (97.5% inhibition at 100 microg/mL, P < 0.01). CONCLUSION: Suplatast tosilate inhibits TARC production by human Th2 cells. Therefore, this agent inhibits both Th2 cytokine and Th2 chemokine and may be a useful anti-allergic agent.  相似文献   
997.
998.
999.
1000.
We found elevated levels of interleukin-8 in pleural fluid samples from patients with pleural effusion and with a sustained fibrotic change of the lung due to Mycoplasma pneumoniae infection. This result suggests a critical role of interleukin-8 in the pathogenesis of a certain type of pulmonary disease caused by M. pneumoniae.  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