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   15935篇
  免费   1470篇
  国内免费   33篇
耳鼻咽喉   164篇
儿科学   483篇
妇产科学   518篇
基础医学   2182篇
口腔科学   233篇
临床医学   2279篇
内科学   2881篇
皮肤病学   262篇
神经病学   1577篇
特种医学   417篇
外国民族医学   1篇
外科学   1884篇
综合类   315篇
一般理论   12篇
预防医学   1832篇
眼科学   345篇
药学   1038篇
中国医学   19篇
肿瘤学   996篇
  2022年   119篇
  2021年   271篇
  2020年   182篇
  2019年   260篇
  2018年   361篇
  2017年   284篇
  2016年   293篇
  2015年   311篇
  2014年   471篇
  2013年   662篇
  2012年   878篇
  2011年   865篇
  2010年   483篇
  2009年   464篇
  2008年   810篇
  2007年   788篇
  2006年   817篇
  2005年   822篇
  2004年   748篇
  2003年   694篇
  2002年   654篇
  2001年   378篇
  2000年   361篇
  1999年   339篇
  1998年   169篇
  1997年   158篇
  1996年   125篇
  1995年   125篇
  1994年   120篇
  1993年   99篇
  1992年   254篇
  1991年   252篇
  1990年   244篇
  1989年   206篇
  1988年   232篇
  1987年   221篇
  1986年   234篇
  1985年   203篇
  1984年   178篇
  1983年   177篇
  1982年   128篇
  1981年   127篇
  1980年   105篇
  1979年   184篇
  1978年   133篇
  1977年   98篇
  1976年   121篇
  1975年   119篇
  1974年   131篇
  1973年   95篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
A method is described for the chemical measurement of calcium oxalate and phosphate crystal formation in urine. The crystals were centrifuged, washed and the oxalate measured by an immobilised oxalate oxidase technique and the phosphate by a standard centrifugal analyser procedure. The methods proved precise and recoveries were good. Calcium oxalate crystal formation after evaporation is time-dependent and this parameter must therefore be standardised. Values for normal urinary calcium oxalate crystal concentration after concentration are given.  相似文献   
32.
33.
34.
Enantiomerically pure hexahydroquinolinones of the structural type 9 were prepared by a variation of the Hantzsch synthesis in which an optically active acetoacetate served as a chiral auxiliary reagent. Determinations of the de and ee values are described. The absolute configurations of the optically pure products were characterized by single-crystal X-ray analysis. The antipodes 9a and 9b exhibited calcium antagonistic activities on smooth musculature; the (S)-(-)-enantiomer 9b was the more potent compound with regard to the EC50 values which differed by a factor of 100; the intrinsic activity of 9b was 1.2, compared with a value of 0.54 for 9a. On the other hand, R-(+)-9a exerted positive inotropic effects on electrically stimulated atria. The cause of these effects is discussed.  相似文献   
35.
1.5 tesla magnetic resonance imaging of acute spinal trauma   总被引:2,自引:0,他引:2  
Fifty patients with spinal injury above L2 were studied with MRI; forty-two had initial and followup studies permitting correlation of MRI abnormalities with neurologic improvement. Two discrete patterns of MRI abnormality were identified, presumably representing cord hemorrhage and edema respectively. A third pattern appeared to represent a mixed type of injury. The correlation between the MRI patterns of cord injury and neurologic recovery was excellent. The ability of MRI to demonstrate and characterize acute cord injury appears to exceed that of other diagnostic techniques.  相似文献   
36.
Out of 29 patients with right-sided infective endocarditis 13 had associated congenital heart disease and none was a drug addict. Staphylococcus aureus was the commonest organism isolated. The tricuspid valve was infected twice as commonly as the pulmonary valve. Only 11 out of the 29 patients had valvular infection potentially amenable to surgical therapy at the time of death. Ring abscesses were present in 10 patients.  相似文献   
37.
Polyunsaturated fatty acids (PUFAs) are components of cell membranes and may play an immunomodulating role in the pathogenesis of atopic dermatitis (AD). The goal was to determine the impact of PUFAs on AD by dietary supplementation of infants. Based on the parents' decision on their babies' primary feeding, mothers and newborns were randomized to the supplementation with gamma-linolenic acid (GLA) or placebo for up to 6 months. Breastfed infants received GLA by supplementing their mothers. Formula diet was commercial whey hydrolysate unsupplemented with PUFAs. Of 131 eligible infants, 24 developed AD within the first year of life. Of these, nine belonged to the exclusively breastfed group (n = 58), 14 to the combined-fed group (n = 53), and one to the never breastfed group (n = 20). We could not find an influence of GLA on the development of AD. In subjects with AD, at 1 yr of age the serum-immunoglobulin E (IgE) was the lowest in the GLA-supplemented group A-subjects. In the GLA-supplemented group, GLA-levels in breast milk were similar in atopic and non-atopic infants. In the non-supplemented group the GLA-content of breast milk was 0.07% of total fatty acids in atopic infants vs. 0.17% in non-atopic infants (p < 0.01). Dietary GLA-supplementation could not prevent AD. Interestingly, the number of infants developing AD was the lowest in never breastfed children. In infants suffering from AD, GLA-supplementation seemed to reduce total IgE in the first year of life.  相似文献   
38.
39.
We studied a random sample of Japanese and compared both Japanese and German monocyte antigen frequencies and performed a segregation analysis in Japanese families. In Japanese, the following gene frequencies were established: 0.1033 for HMA-A1; 0.0299 for HMA-A3; 0.0033 for HMA-A6; 0.1521 for HMA-B2. Data on the gene frequency in Germans were presented by Rose. In this comparison, the frequency for HMA-B2 in Japanese is more than two times higher; for antigen HMA-A6, the Japanese is a fifth of the German quantity. The antigen HMA-B4 was not found in Japanese. The results we obtained from family analysis confirmed an unambiguous autosomal, codominant inheritance of the examined HMA antigens.  相似文献   
40.
Metabolic labeling and quantitative 2D gel autoradiography were used to assess changes in the synthesis and transport of GAP-43 in entorhinal cortex (EC) neurons and perforant pathway during lesion-induced sprouting and reactive synaptogenesis. In normal adult rats, there is a high constitutive level of GAP-43 synthesis and transport in EC neurons projecting to the hippocampus. Following unilateral EC lesions, there is a 2-fold (100%) increase in the transport of newly synthesized GAP-43 to the contralateral or 'sprouting' hippocampus. The timing of this upregulation (between 6 and 15 days) suggests that changes in GAP-43 expression occur in response to the growth of presynaptic terminals during sprouting.  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