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   1104466篇
  免费   73698篇
  国内免费   1456篇
耳鼻咽喉   15443篇
儿科学   35351篇
妇产科学   28961篇
基础医学   157175篇
口腔科学   30015篇
临床医学   97939篇
内科学   210347篇
皮肤病学   24592篇
神经病学   84464篇
特种医学   44272篇
外国民族医学   201篇
外科学   167951篇
综合类   21977篇
现状与发展   1篇
一般理论   333篇
预防医学   76754篇
眼科学   24922篇
药学   87947篇
  7篇
中国医学   2824篇
肿瘤学   68144篇
  2021年   8198篇
  2019年   8417篇
  2018年   12070篇
  2017年   9423篇
  2016年   10702篇
  2015年   11964篇
  2014年   16268篇
  2013年   23513篇
  2012年   32702篇
  2011年   34481篇
  2010年   20224篇
  2009年   18868篇
  2008年   31917篇
  2007年   34120篇
  2006年   34695篇
  2005年   33022篇
  2004年   31496篇
  2003年   30252篇
  2002年   29174篇
  2001年   60317篇
  2000年   61712篇
  1999年   51223篇
  1998年   12769篇
  1997年   11274篇
  1996年   11245篇
  1995年   10557篇
  1994年   9534篇
  1993年   9037篇
  1992年   37977篇
  1991年   36467篇
  1990年   35915篇
  1989年   34438篇
  1988年   30996篇
  1987年   30107篇
  1986年   28335篇
  1985年   26582篇
  1984年   19338篇
  1983年   16237篇
  1982年   8959篇
  1979年   17106篇
  1978年   11483篇
  1977年   10292篇
  1976年   8889篇
  1975年   10116篇
  1974年   11703篇
  1973年   11318篇
  1972年   10801篇
  1971年   10140篇
  1970年   9279篇
  1969年   8964篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Brain morphology was examined using magnetic resonance imaging in 30 first-episode patients with a schizophreniclike psychosis, 15 chronic schizophrenics, and 20 neurological controls. Statistical analyses of computer-generated measurements of regions of interest were controlled for gender, age, social class, and total brain volume. Lateral ventricular size was increased in both first-episode and chronic schizophrenic patients, with greater significance on the left than on the right side. Only the chronic patients, however, had reduced temporal lobe size, which also was greater on the left side. No major correlations of regional brain morphological measurements with cognitive functioning were found, although some measurements of verbal memory were correlated with parahippocampal size. This is a report of a preliminary study that suggests that some morphological brain changes may be present at the time of first treatment for a psychotic illness, whereas others may occur later in the course of illness. Future prospective studies may determine the clinical significance of these changes and whether they progress with the development of illness chronicity.  相似文献   
994.
Chronic actinic dermatitis responding to danazol   总被引:1,自引:0,他引:1  
We report an unusual case of chronic actinic dermatitis associated with α1-antitrypsin deficiency and who responded well to treatment with danazol.  相似文献   
995.
Cultured brain cells from rat fetuses of ethanol-treated mothers demonstrated more than 2-fold elevations in choline acetyltransferase (ChAT) activity relative to those of control (saline-exposed) fetal brain cells. When cells from control animals were incubated in vitro for 5 days with 0.1% ethanol, ChAT activity was found to increase more than 4-fold. Brain cells from in utero ethanol-treated animals further exposed to ethanol in vitro for 5 days demonstrated significantly higher ChAT activity compared to cells exposed to ethanol only in vivo. These levels were more than 6 times greater than those of central nervous system cells never exposed to ethanol. Acetylcholinesterase (AChE) activity was significantly elevated (greater than 4-fold) in fetal brain cells when ethanol was present both in vivo and in vitro, but neither treatment alone resulted in any significant changes in AChE. These effects of ethanol on enzymes involved in acetylcholine metabolism may contribute to the different developmental neurologic abnormalities associated with fetal alcohol exposure.  相似文献   
996.
Trace element status in multiple sclerosis   总被引:1,自引:0,他引:1  
We compared trace element status in multiple sclerosis (MS) patients (n = 27) with and without treatment with corticosteroids and groups of healthy subjects. Concentrations of plasma ceruloplasmin, selenium, and zinc and erythrocyte (RBC) glutathione peroxidase, Se, and Zn were similar in all groups. RBC copper concentrations were significantly lower in MS patients than in control subjects (mean +/- SEM: 0.048 +/- 0.005 vs 0.060 +/- 0.002 mumol/g Hb) because of decreased RBC Cu with steroid therapy. RBC Zn-Cu ratios were significantly higher (14.9 +/- 1.0 vs 10.1 +/- 0.3) in MS patients than in control subjects, differing in both groups of MS patients. In MS and control subjects, RBC Cu correlated significantly with RBC Zn (r = 0.56, 0.49). Disease acuity and disability had no effect on trace-mineral status. These data suggest that in MS there is altered Cu and Zn homeostasis that may cause or result from the disease and is influenced by corticosteroid therapy. Systemic trace element alterations might provide clinically useful markers of MS.  相似文献   
997.
998.
999.
1000.
This study was undertaken to determine whether the dose-dependent effect of glucagon on gluconeogenesis parallels its effect on hepatic glycogenolysis in conscious overnight-fasted dogs. Endogenous insulin and glucagon secretion were inhibited by somatostatin (0.8 micrograms X kg-1 X min-1), and intraportal replacement infusions of insulin (213 +/- 28 microU X kg-1 X min-1) and glucagon (0.65 ng X kg-1 X min-1) were given to maintain basal hormone concentrations for 2 h (12 +/- 2 microU/ml and 108 +/- 23 pg/ml, respectively). The glucagon infusion was then increased 2-, 4-, 8-, or 12-fold for 3 h, whereas the rate of insulin infusion was left unchanged. Glucose production (GP) was determined with 3-[3H]glucose, and gluconeogenesis (GNG) was assessed with tracer (U-[14C]alanine conversion to [14C]glucose) and arteriovenous difference (hepatic fractional extraction of alanine, FEA) techniques. Increases in plasma glucagon of 53 +/- 8, 199 +/- 48, 402 +/- 28, and 697 +/- 149 pg/ml resulted in initial (15-30 min) increases in GP of 1.1 +/- 0.4 (N = 4), 4.9 +/- 0.5 (N = 4), 6.5 +/- 0.6 (N = 6), and 7.7 +/- 1.4 (N = 4) mg X kg-1 X min-1, respectively; increases in GNG (approximately 3 h) of 48 +/- 19, 151 +/- 50, 161 +/- 25, and 157 +/- 7%, respectively; and increases in FEA (3 h) of 0.14 +/- 0.07, 0.37 +/- 0.05, 0.42 +/- 0.04, and 0.40 +/- 0.17, respectively. In conclusion, GNG and glycogenolysis were similarly sensitive to stimulation by glucagon in vivo, and the dose-response curves were markedly parallel.  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