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   8549篇
  免费   338篇
  国内免费   52篇
耳鼻咽喉   94篇
儿科学   173篇
妇产科学   96篇
基础医学   1160篇
口腔科学   255篇
临床医学   440篇
内科学   2049篇
皮肤病学   165篇
神经病学   633篇
特种医学   369篇
外科学   1587篇
综合类   34篇
一般理论   1篇
预防医学   189篇
眼科学   80篇
药学   540篇
中国医学   14篇
肿瘤学   1060篇
  2023年   34篇
  2022年   46篇
  2021年   128篇
  2020年   62篇
  2019年   75篇
  2018年   120篇
  2017年   97篇
  2016年   144篇
  2015年   164篇
  2014年   224篇
  2013年   258篇
  2012年   410篇
  2011年   448篇
  2010年   265篇
  2009年   244篇
  2008年   454篇
  2007年   538篇
  2006年   504篇
  2005年   597篇
  2004年   580篇
  2003年   601篇
  2002年   556篇
  2001年   118篇
  2000年   80篇
  1999年   135篇
  1998年   164篇
  1997年   148篇
  1996年   136篇
  1995年   122篇
  1994年   128篇
  1993年   109篇
  1992年   102篇
  1991年   99篇
  1990年   95篇
  1989年   68篇
  1988年   86篇
  1987年   71篇
  1986年   72篇
  1985年   82篇
  1984年   72篇
  1983年   45篇
  1982年   43篇
  1981年   51篇
  1980年   46篇
  1979年   35篇
  1978年   38篇
  1977年   31篇
  1976年   31篇
  1975年   23篇
  1973年   17篇
排序方式: 共有8939条查询结果,搜索用时 15 毫秒
1.
2.
The effect of electric charge on the hepatic disposition of macromolecules was studied in the rat. Charged derivatives of dextran (T-70) and bovine serum albumin (BSA), mitomycin C–dextran conjugates (MMC-D), and lactosaminated BSA (Lac-BSA) were employed as model macromolecules. After intravenous injection, cationic macromolecules were rapidly eliminated from plasma because of their extensive hepatic uptake, while anionic and neutral macromolecules were slowly eliminated. Cationic macromolecules were recovered from parenchymal and nonparenchymal hepatic cells at a cellular uptake (per unit cell number) ratio of 1.4–3.2, while that of Lac-BSA was 14. During liver perfusion using a single-pass constant infusion mode, cationic macromolecules were continuously extracted by the liver, with extraction ratios at steady-state (E ss) ranging between 0.03 and 0.54, whereas anionic and neutral macromolecules were almost completely recovered in the outflow at steady state. The E ss for cationized BSA (Cat-BSA) and cationic MMC-Dcat were concentration dependent and decreased at low temperatures and in the presence of colchicine and cytochalasin B. The possible participation of the internalization process in the uptake of cationic macromolecules by hepatocytes was suggested.  相似文献   
3.
4.
5.
6.
A 78-year-old woman with diagnosis of acute myocardial infarction (AMI) in the anteroseptal area fell into cardiogenic shock suddenly just before starting percutaneous coronary intervention (PCI). Echocardiography showed left ventricular free wall rupture, then an emergent operation was performed by sutureless patch repair using collagen fleece with fibrinogen-based impregnation. Eight days later from the initial operation, the onset of ventricular septal perforation (VSP) was recognized. Fifteen days after, the infarct exclusion technique with endocardial patch was performed. She has been doing well 4 months after the operation without residual shunt. To our best knowledge, this is the first surgical case report that free wall rupture of left ventricle and VSP which are serious complications after myocardial infarction happened in succession.  相似文献   
7.
8.
A rare case of urinary bladder carcinoma with granulocyte colony stimulating factor (G-CSF) production was reported. In an 83-year-old female, marked neutrophilia in the peripheral blood decreased from 132,500/mm3 to 3,300/mm3 after tumour resection. The tumour was a transitional cell carcinoma. The serum G-CSF level reduced from 238 pg/ml pre-operatively to normal (60 pg/ml) after the operation. Immunohistochemical investigation of the resected tumour with monoclonal antibody specific for G-CSF revealed positive staining in the carcinoma cells, confirming G-CSF secretion.  相似文献   
9.
10.
The effect of (+)-5-oxo-D-prolinepiperidinamide monohydrate (NS-105), a novel cognition enhancer, on adenylate cyclase activity was investigated in cultured neurons of the mouse cerebral cortex. NS-105 (10–7 and 10–6 M) inhibited forskolin-stimulated cyclic AMP formation, an action that was dependent on pertussis toxin-sensitive G proteins. Conversely, in pertussis toxin-pretreated neurons, NS-105 (10–7 –10–5 M) significantly enhanced the forskolin-stimulated cyclic AMP formation, and this action was completely reversed by cholera toxin. A metabotropic glutamate receptor agonist (1S, 3R)-1-aminocyclopentane-1, 3-dicarboxylic acid (1S, 3R-ACPD) produced similar bi-directional actions on the cyclic AMP formation. Both of these inhibitory and facilitatory actions of NS-105 and 1S, 3R-ACPD were blocked by L(+)-2-amino-3-phosphopropinoic acid (L-AP3). NS-105 (10–6 M) and 1S, 3R-ACPD (10–4 M) significantly enhanced isoproterenol- and adenosine-stimulated cyclic AMP formation. The enhancement of such Gs-coupled receptor agonists-stimulated cyclic AMP formation was also produced by quisqualate but not by L(+)-2-amino-4-phosphonobutanoate (L-AP4). The phosphoinositides hydrolysis was enhanced by 1S, 3R-ACPD (10–4 M) but not by NS-105 (10–6 M), however, 1S, 3R-ACPD-induced increase in phosphoinositides turnover was attenuated by NS-105. These findings suggest that NS-105 stimulates metabotropic glutamate receptor subclasses that are coupled both negatively and positively to adenylate cyclase, but it acts as an antagonist at the receptor subclasses that are linked to phosphoinositides hydrolysis. Received: 3 February 1997 / Accepted: 25 April 1997  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