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   1278421篇
  免费   92870篇
  国内免费   1992篇
耳鼻咽喉   18202篇
儿科学   42310篇
妇产科学   37894篇
基础医学   187275篇
口腔科学   35392篇
临床医学   108259篇
内科学   251763篇
皮肤病学   26503篇
神经病学   99497篇
特种医学   50050篇
外国民族医学   366篇
外科学   197805篇
综合类   26527篇
现状与发展   1篇
一般理论   300篇
预防医学   92736篇
眼科学   29070篇
药学   97898篇
  1篇
中国医学   2496篇
肿瘤学   68938篇
  2018年   11866篇
  2015年   11657篇
  2014年   16049篇
  2013年   24437篇
  2012年   33665篇
  2011年   36095篇
  2010年   21298篇
  2009年   20080篇
  2008年   35062篇
  2007年   38058篇
  2006年   38595篇
  2005年   37890篇
  2004年   36482篇
  2003年   35432篇
  2002年   34994篇
  2001年   58125篇
  2000年   59601篇
  1999年   50709篇
  1998年   14242篇
  1997年   12823篇
  1996年   13081篇
  1995年   12350篇
  1994年   11764篇
  1993年   10866篇
  1992年   41000篇
  1991年   40381篇
  1990年   39904篇
  1989年   38722篇
  1988年   36122篇
  1987年   35367篇
  1986年   33740篇
  1985年   32157篇
  1984年   23939篇
  1983年   20827篇
  1982年   12381篇
  1981年   10935篇
  1980年   10209篇
  1979年   22653篇
  1978年   15886篇
  1977年   13734篇
  1976年   12982篇
  1975年   14208篇
  1974年   16694篇
  1973年   16083篇
  1972年   15323篇
  1971年   14234篇
  1970年   13222篇
  1969年   12735篇
  1968年   11980篇
  1967年   10480篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
BMP-2 gene polymorphisms and osteoporosis: the Rotterdam Study.   总被引:7,自引:0,他引:7  
After reported associations of variations in the BMP-2 gene with osteoporosis in small populations, we studied the association of the BMP-2 gene polymorphisms Ser37Ala and Arg190Ser with osteoporosis in 6353 men and women from the Rotterdam Study. We did not observe an association of these variants with BMD, bone loss, hip structural analysis parameters, and fracture risk. INTRODUCTION: Bone morphogenetic protein 2 (BMP-2) plays a role in osteoblast differentiation. BMP-2 gene variation has previously been associated with osteoporosis in various small populations, but current evidence remains inconclusive about the exact association with osteoporosis. Therefore, we studied the association of two polymorphisms located in the BMP-2 gene (Ser37Ala and Arg190Ser) and haplotypes defined by these polymorphisms with BMD, rates of bone loss, parameters of hip structural analysis (HSA), and fractures in the Rotterdam Study, a large prospective cohort study of diseases in the elderly. MATERIALS AND METHODS: Databases were searched for polymorphisms and haplotype blocks in the BMP-2 gene region. Allele frequencies for Ser37Ala and Arg190Ser were determined in 60 blacks and 110 Chinese from Coriell panels. Genotype data on Ser37Ala and Arg190Ser were available for 6353 individuals from the Rotterdam Study population. Haplotype alleles defined by Ser37Ala and Arg190Ser were inferred using PHASE software. Genotype and haplotype analyses for BMD (measured at the lumbar spine and femoral neck), bone loss per year (measured at the femoral neck), and HSA were performed using AN(C)OVA. Fractures were analyzed using a Cox proportional-hazards model and logistic regression. All outcomes were adjusted for age, height, and weight. RESULTS: Allele frequencies were 2.5% for Ala37 and 40.2% for Ser190, whereas haplotype allele frequencies were 57.28% (Ser37Arg190), 40.19% (Ser37Ser190), 2.50% (Ala37Arg190), and 0.02% (Ala37Ser190). For BMD, bone loss, HSA outcomes, and (incident) fractures, no differences could be seen between genotype and haplotype groups. Conclusions: In this large population-based cohort of Dutch whites, we conclude that the BMP-2 Ser37Ala and Arg190Ser polymorphisms or haplotypes thereof are not associated with parameters of osteoporosis.  相似文献   
95.
96.
97.
98.
99.
Mucosal trypsin, a protease-activated receptor (PAR) stimulant, may have an endogenous bronchoprotective role on airway smooth muscle. To test this possibility the effects of lumenal trypsin on airway tone in segments of pig bronchus were tested. Bronchial segments from pigs were mounted in an organ chamber containing Kreb's solution. Contractions were assessed from isovolumetric lumen pressure induced by acetylcholine (ACh) or carbachol added to the adventitia. Trypsin, added to the airway lumen (300 microg x mL(-1)), had no immediate effect on smooth muscle tone but suppressed ACh-induced contractions after 60 min, for at least 3 h. Synthetic activating peptides (AP) for PAR1, PAR2 or PAR3 were without effect, but PAR4 AP caused rapid, weak suppression of contractions. Lumenal thrombin was without effect and did not prevent the effects of trypsin. Effects of trypsin were reduced by N(omega)-nitro-L-arginine methyl ester but not indomethacin. Trypsin, thrombin and PAR4 AP released prostaglandin E2. Adventitially, trypsin, thrombin and PAR4 AP (but not PAR2 AP) relaxed carbachol-toned airways after <3 min. The findings of this study show that trypsin causes delayed and persistent bronchoprotection by interacting with airway cells accessible from the lumen. The signalling mechanism may involve nitric oxide synthase but not prostanoids or protease-activated receptors.  相似文献   
100.
Abstract Migraine without aura is typically considered a female condition. The purpose of this study was to determine if there have been any changes in the female-to-male ratio of the disease over time. We included in the study all patients with migraine without aura (n=3457) referred to the Parma University Headache Centre between 1976 and 1995. They were divided into subgroups with respect to gender and year-range of onset of migraine (before 1960, in the 1960s, in the 1970s, in the 1980s, and between 1990 and 1995). Gender ratio ranged from 3.6:1 (in patients with onset before 1960) to 2.8:1 (in patients with onset in the 1980s), with no statistically significant changes during the observation period.  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