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   2480篇
  免费   221篇
  国内免费   16篇
耳鼻咽喉   6篇
儿科学   46篇
妇产科学   42篇
基础医学   442篇
口腔科学   17篇
临床医学   251篇
内科学   665篇
皮肤病学   28篇
神经病学   205篇
特种医学   54篇
外国民族医学   1篇
外科学   308篇
综合类   61篇
一般理论   6篇
预防医学   209篇
眼科学   21篇
药学   157篇
中国医学   16篇
肿瘤学   182篇
  2023年   15篇
  2022年   31篇
  2021年   62篇
  2020年   32篇
  2019年   55篇
  2018年   55篇
  2017年   45篇
  2016年   41篇
  2015年   50篇
  2014年   53篇
  2013年   96篇
  2012年   167篇
  2011年   186篇
  2010年   103篇
  2009年   83篇
  2008年   117篇
  2007年   148篇
  2006年   129篇
  2005年   110篇
  2004年   122篇
  2003年   98篇
  2002年   95篇
  2001年   89篇
  2000年   97篇
  1999年   57篇
  1998年   35篇
  1997年   37篇
  1996年   30篇
  1995年   13篇
  1994年   15篇
  1993年   23篇
  1992年   52篇
  1991年   40篇
  1990年   43篇
  1989年   33篇
  1988年   39篇
  1987年   27篇
  1986年   25篇
  1985年   27篇
  1984年   16篇
  1983年   19篇
  1982年   13篇
  1981年   8篇
  1980年   10篇
  1979年   16篇
  1978年   9篇
  1976年   7篇
  1975年   5篇
  1974年   8篇
  1970年   5篇
排序方式: 共有2717条查询结果,搜索用时 15 毫秒
11.
Summary Serum intact parathyroid hormone (PTH), 25 hydroxyvitamin D(25OHD), 1,25 dihydroxyvitamin D (1,25(OH)2D), albumin, and ionized calcium were measured in 61 Chinese female patients with hip fracture and 61 control subjects. Hip fracture patients had low albumin, ionized calcium, and 250HD levels. Serum PTH and 1,25 (OH)2D values were not different between the two groups. We conclude that although 250HD level in hip fracture patients is low, there is no evidence of secondary hyperparathyroidism, suggesting that the low 250HD levels may be a secondary phenomenon in response to the fracture.  相似文献   
12.
We undertook an analysis of the hazard functions derived from results published by the Parkinson Study Group following their investigation of deprenyl. Our findings indicate that the action of deprenyl is transient rather than sustained. We also infer that this effect may be mediated through alleviation of symptoms rather than by neuroprotection.  相似文献   
13.
14.
Myocardial infarction is an important public health problemworldwide. Rapid restoration of flow remains as the foundationfor life-saving treatment of patients with ST-segment elevationmyocardial infarction (STEMI). In Europe, it is heartening tonote that the utilization of reperfusion therapies was increasingly,with the proportion rising from 55.8% in 2000–2001 to63.9% in 2004, based on the first and second Euro Heart Surveysof Acute Coronary Syndromes, respectively.1 Notably, patientswere more likely to receive primary percutaneous coronary intervention(increased from 37 to 59% over the same period),1 probably becauseof the favourable results derived from  相似文献   
15.
16.
Insulin and branched-chain amino acid (BCAA) metabolism was studied in 14 adolescents with uremia on hemodialysis. Glucose tolerance was measured by intravenous glucose tolerance tests. Insulin sensitivity was measured by the euglycemia clamp technique. Insulin secretion during constant hyperglycemia was measured by the hyperglycemic clamp technique. Fasting plasma BCAA concentrations were compared with data from 8 adolescent controls, whereas insulin indices were compared with 8 young adults controls and with published normal data in adolescents. The patients could be further sub-divided into two groups with respect to their growth velocity standard deviation score (GVSDS). Group 1 consisted of 7 patients with GVSDS less than −2. This group demonstrated insulin resistance, glucose intolerance, and low insulin secretion. This group also had low plasma valine, leucine, and isoleucine concentrations compared with control values. Group 2 consisted of 7 patients with GVSDS more than −2. This group demonstrated insulin resistance, but normal glucose tolerance and normal insulin secretion. Plasma valine, leucine, and isoleucine concentrations in group 2 were not different from control values. Total plasma BCAA correlated with glucose tolerance index and with insulin secretion, but not with insulin sensitivity. Growth failure in uremia is associated with glucose intolerance, hypoinsulinemia, and low plasma BCAA concentrations. Impaired utilization of conventional energy sources leading to preferential oxidation of BCAA may contribute to reduced anabolism and growth failure in uremia. Received October 8, 1997; received in revised form February 3, 1998; accepted February 6, 1998  相似文献   
17.
18.
PTEN is an important tumor suppressor gene. Hereditary mutation of PTEN causes tumor-susceptibility diseases such as Cowden disease. We used the Cre-loxP system to generate an endothelial cell-specific mutation of Pten (Tie2CrePten) in mice. Tie2CrePten(flox/+) mice displayed enhanced tumorigenesis due to an increase in angiogenesis driven by vascular growth factors. This effect was partially dependent on the PI3K subunits p85alpha and p110gamma. In vitro, Tie2CrePten(flox/+) endothelial cells showed enhanced proliferation/migration. Tie2CrePten(flox/flox) mice died before embryonic day 11.5 (E11.5) due to bleeding and cardiac failure caused by impaired recruitment of pericytes and vascular smooth muscle cells to blood vessels, and of cardiomyocytes to the endocardium. These phenotypes depend strongly on p110gamma rather than on p85alpha and were associated with decreased expression of Ang-1, VCAM-1, connexin 40, and ephrinB2 but increased expression of Ang-2, VEGF-A, VEGFR1, and VEGFR2. Pten is thus indispensable for normal cardiovascular morphogenesis and post-natal angiogenesis, including tumor angiogenesis.  相似文献   
19.
To determine the transacting genetic factors of NZW contributing to the development of autoimmune disease in (NZB X NZW)F1 (B/W F1) mice, we examined the relationship between the T cell receptor beta chain gene deletion and the severity of autoimmune manifestations in 76 B/W F1 X NZB backcross mice. Very high association between the T cell receptor beta chain gene deletion and the development of autoimmune manifestations including the production of IgG anti-DNA antibodies and circulating retroviral gp70 immune complexes was observed, indicating that a defect in the NZW T cell receptor beta chain gene or a locus closely linked to it contributes to the autoantibody formation in B/W F1.  相似文献   
20.
WSX-1 is a class I cytokine receptor with homology to the IL-12 receptors and is essential for resistance to Leishmania major infection. In the present study, we demonstrated that WSX-1 was also required for resistance to Trypanosoma cruzi. WSX-1-/- mice exhibited prolonged parasitemia, severe liver injury, and increased mortality over wild-type mice. WSX-1-/- splenocytes produced enhanced levels of Th2 cytokines, which were responsible for the prolonged parasitemia. Massive necroinflammatory lesions were observed in the liver of infected WSX-1-/- mice, and IFN-gamma that was overproduced in WSX-1-/- mice compared with wild-type mice was responsible for the lesions. In addition, vast amounts of various proinflammatory cytokines, including IL-6 and TNF-alpha, were produced by liver mononuclear cells in WSX-1-/- mice. Thus, during T. cruzi infection, WSX-1 suppresses liver injury by regulating production of proinflammatory cytokines, while controlling parasitemia by suppression of Th2 responses, demonstrating its novel role as an inhibitory regulator of cytokine production.  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