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   431852篇
  免费   13699篇
  国内免费   541篇
耳鼻咽喉   4474篇
儿科学   14560篇
妇产科学   8494篇
基础医学   53149篇
口腔科学   7532篇
临床医学   32531篇
内科学   88546篇
皮肤病学   7708篇
神经病学   39317篇
特种医学   16385篇
外国民族医学   101篇
外科学   60968篇
综合类   3531篇
现状与发展   1篇
一般理论   70篇
预防医学   41325篇
眼科学   7719篇
药学   27219篇
中国医学   1417篇
肿瘤学   31045篇
  2023年   1444篇
  2022年   1473篇
  2021年   4617篇
  2020年   2600篇
  2019年   4905篇
  2018年   29192篇
  2017年   21813篇
  2016年   23979篇
  2015年   6978篇
  2014年   7631篇
  2013年   11490篇
  2012年   24731篇
  2011年   38077篇
  2010年   27218篇
  2009年   18234篇
  2008年   34109篇
  2007年   37241篇
  2006年   15849篇
  2005年   17305篇
  2004年   17468篇
  2003年   17219篇
  2002年   14693篇
  2001年   6885篇
  2000年   7160篇
  1999年   6241篇
  1998年   1390篇
  1997年   1196篇
  1996年   987篇
  1995年   954篇
  1994年   852篇
  1992年   3441篇
  1991年   3106篇
  1990年   3017篇
  1989年   2697篇
  1988年   2523篇
  1987年   2361篇
  1986年   2211篇
  1985年   2008篇
  1984年   1496篇
  1983年   1256篇
  1979年   1273篇
  1978年   916篇
  1977年   849篇
  1975年   843篇
  1974年   1049篇
  1973年   1029篇
  1972年   980篇
  1971年   954篇
  1970年   903篇
  1969年   967篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We report the identification of a new transthyretin (TTR) gene mutation and variant protein, Glu61Gly, in a 55-year-old man with progressive cardiomyopathy, mild peripheral neuropathy and bilateral carpal tunnel syndrome. A diagnosis of TTR-associated familial amyloidosis (ATTR) was considered after an endomyocardial biopsy revealed amyloid deposits in the heart of a patient who had no family history of amyloidosis and no evidence of a plasma cell dyscrasia. Serum screening for a TTR variant by isoelectric focusing (IEF) was positive and prompted further studies to identify the genetic abnormality and to characterize the amyloidogenic protein. Direct DNA sequence analysis of all four coding regions in the TTR gene demonstrated heterozygosity in exon 3. Near equal amounts of guanine (G) and adenine (A) were observed at the second base position of codon 61. The wild-type (GAG) and mutated (GGG) sequences found in codon 61 correspond to glutamic acid (Glu) and glycine (Gly) residues, amino acids which differ in mass by -72 Da. Mass spectrometric analyses of TTR immunoprecipitated from serum showed the presence of both wild-type and variant proteins. The observed mass results for the wild-type and variant proteins were consistent with the predicted values calculated from the genetic analysis data.  相似文献   
92.
93.
The specific characteristics of genetic data lead to ethical-legal conflicts in the framework of genetic diagnosis. Several international organisations, including UNESCO and the Council of Europe, have enacted rules referring to the use of genetic information. This paper discusses possible legal and ethical criteria that could be used in genetic testing.  相似文献   
94.
Due to limited aqueous solubility of dorzolamide at physiologic pH, the pH of Trusopt eye drops (cont. 2% dorzolamide) has to be kept at about 5.65, and to increase the topical bioavailability of the drug from Trusopt the contact time of the drug with the eye surface is increased by increasing the viscosity of the eye drops to 100 cps. This low pH and high viscosity can lead to local irritation. In this study, dorzolamide hydrochloride was formulated as 2% and 4% low viscosity solutions (viscosity 3 to 5 cps) containing randomly methylated beta-cyclodextrin at pH 7.45. These formulations were evaluated in rabbits. The animals were sacrificed at various time points after topical administration of the drug and the dorzolamide concentration determined in the different parts of the eye. Trusopt was used as a reference standard. The topical availability of dorzolamide from the cyclodextrin-containing eye drops appeared to be comparable to that from Trusopt and the drug reached retina and optic nerve to give measurable concentrations for at least 8 h after administration of the eye drops.  相似文献   
95.
In the first experiment, 52 sows, each having raised one litter, were randomly assigned to the five following groups: control (nongravid) for pregnancy (CP), 110 d pregnancy (P110), control (nongravid) for lactation (CL), 4-wk lactation with 8 (L8) and with 12 (L12) piglets. In a second experiment, 36 sows, each having raised three litters, were randomly assigned to the following groups: control group (nongravid) fed a low-energy-density, 1% tallow diet (CLED) and two lactating groups, one fed the low-energy-density diet (LLED) and one fed a high-energy-density, 10% tallow diet (LHED). At slaughter, the stomach, small and large intestine and cecum were excised, emptied and freed from fat. Lengths and pre- and post-defatting weights were measured. Portions of tissues were homogenized and analyzed for protein, pepsin, maltase, RNA and DNA. Pregnancy had no effect on the weights of the different components of the gastrointestinal tract. Liver and small intestine weights were larger in lactating sows than in the CL group. Sows nursing 12 piglets had heavier livers than those nursing 8. The fundic mucosa of the latter had higher total pepsin activity and total protein and RNA contents than that of L12 sows. LHED sows had heavier small intestine and lower total pepsin content of the fundic mucosa than LLED sows.  相似文献   
96.
Gallibacterium anatis (previously named Pasteurella haemolytica-like) is considered a normal inhabitant of genital and upper respiratory tracts of healthy chickens, but it is also associated with different pathological conditions. Secreted metalloproteases from field and reference G. anatis cultures were obtained by methanol precipitation and were characterized. Proteins of molecular mass higher than 100 kDa showing proteolytic activity were observed in 10% polyacrylamide gels copolymerized with 1% bovine casein. They were active at alkaline pH, and inhibited by ethylenediamine tetraacetic acid. Their activity was stable at 50 degrees C, but partially inhibited at 60 degrees C, and totally inhibited at higher temperatures. Secreted proteins were able to degrade chicken IgG after 24 h of incubation, and cross-reacted with a polyclonal antibody against purified protease from Actinobacillus pleuropneumoniae. Secreted metalloproteases could play a role in infections caused by G. anatis.  相似文献   
97.
98.
99.

Introduction  

This paper presents the results of a study on the psychometric properties of an authorized Spanish version of the McMaster Family Assessment Device, a self-report measure of family functioning.  相似文献   
100.
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