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   209208篇
  免费   12222篇
  国内免费   752篇
耳鼻咽喉   2619篇
儿科学   6266篇
妇产科学   4749篇
基础医学   27817篇
口腔科学   8737篇
临床医学   15588篇
内科学   49053篇
皮肤病学   5133篇
神经病学   17799篇
特种医学   6368篇
外国民族医学   26篇
外科学   27104篇
综合类   1533篇
现状与发展   1篇
一般理论   68篇
预防医学   19726篇
眼科学   3828篇
药学   12507篇
中国医学   792篇
肿瘤学   12468篇
  2023年   1077篇
  2022年   2147篇
  2021年   4862篇
  2020年   3097篇
  2019年   4393篇
  2018年   6123篇
  2017年   4506篇
  2016年   4345篇
  2015年   5073篇
  2014年   6963篇
  2013年   8892篇
  2012年   13779篇
  2011年   14230篇
  2010年   7380篇
  2009年   6601篇
  2008年   11283篇
  2007年   11966篇
  2006年   11127篇
  2005年   11421篇
  2004年   10700篇
  2003年   9702篇
  2002年   7551篇
  2001年   5205篇
  2000年   5120篇
  1999年   4618篇
  1998年   1888篇
  1997年   1572篇
  1996年   1534篇
  1995年   1338篇
  1994年   1277篇
  1993年   1127篇
  1992年   2790篇
  1991年   2667篇
  1990年   2438篇
  1989年   2426篇
  1988年   2179篇
  1987年   2016篇
  1986年   1905篇
  1985年   1826篇
  1984年   1334篇
  1983年   1078篇
  1982年   665篇
  1981年   580篇
  1980年   566篇
  1979年   970篇
  1978年   654篇
  1977年   521篇
  1975年   571篇
  1974年   568篇
  1973年   567篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
The ban of lead in many electronic products and the expectation that, sooner or later, this ban will include the currently exempt piezoelectric ceramics based on Lead-Zirconate-Titanate has motivated many research groups to look for lead-free substitutes. After a short overview on different classes of lead-free piezoelectric ceramics with large strain, this review will focus on Bismuth-Sodium-Titanate and its solid solutions. These compounds exhibit extraordinarily high strain, due to a field induced phase transition, which makes them attractive for actuator applications. The structural features of these materials and the origin of the field-induced strain will be revised. Technologies for texturing, which increases the useable strain, will be introduced. Finally, the features that are relevant for the application of these materials in a multilayer design will be summarized.  相似文献   
93.
94.

Introduction

The nature of community pharmacy is changing, shifting from the preparation and distribution of medicines to the provision of cognitive pharmaceutical services (CPS); however, often the provision of traditional services leaves little time for innovative services. This study investigated the time community pharmacists spend on the tasks and activities of daily practice and to what extent they are able to implement CPS-related services in daily practice.

Methods

Self-reporting work sampling was used to register the activities of community pharmacists. A smartphone application, designed specifically for this purpose, alerted participants to register their current activity five times per working day for 6 weeks. Participants also completed an online survey about baseline characteristics.

Results

Ninety-one Dutch community pharmacists provided work-sampling data (7848 registered activities). Overall, 51.5% of their time was spent on professional activities, 35.4% on semi-professional activities, and 13.1% on non-professional activities. The proportion of time devoted to CPS decreased during the workweek, whereas the time spent on traditional task increased.

Discussion and conclusion

This study shows it is feasible to collect work-sampling data using smartphone technology. Community pharmacists spent almost half of their time on semi-professional and non-professional activities, activities that could be delegated to other staff members. In practice, the transition to CPS is hampered by competing traditional tasks, which prevents community pharmacists from profiling themselves as pharmaceutical experts in daily practice.  相似文献   
95.
96.
Metabolomics may reveal novel insights into the etiology of prostate cancer, for which few risk factors are established. We investigated the association between patterns in baseline plasma metabolite profile and subsequent prostate cancer risk, using data from 3,057 matched case–control sets from the European Prospective Investigation into Cancer and Nutrition (EPIC). We measured 119 metabolite concentrations in plasma samples, collected on average 9.4 years before diagnosis, by mass spectrometry (AbsoluteIDQ p180 Kit, Biocrates Life Sciences AG). Metabolite patterns were identified using treelet transform, a statistical method for identification of groups of correlated metabolites. Associations of metabolite patterns with prostate cancer risk (OR1SD) were estimated by conditional logistic regression. Supplementary analyses were conducted for metabolite patterns derived using principal component analysis and for individual metabolites. Men with metabolite profiles characterized by higher concentrations of either phosphatidylcholines or hydroxysphingomyelins (OR1SD = 0.77, 95% confidence interval 0.66–0.89), acylcarnitines C18:1 and C18:2, glutamate, ornithine and taurine (OR1SD = 0.72, 0.57–0.90), or lysophosphatidylcholines (OR1SD = 0.81, 0.69–0.95) had lower risk of advanced stage prostate cancer at diagnosis, with no evidence of heterogeneity by follow-up time. Similar associations were observed for the two former patterns with aggressive disease risk (the more aggressive subset of advanced stage), while the latter pattern was inversely related to risk of prostate cancer death (OR1SD = 0.77, 0.61–0.96). No associations were observed for prostate cancer overall or less aggressive tumor subtypes. In conclusion, metabolite patterns may be related to lower risk of more aggressive prostate tumors and prostate cancer death, and might be relevant to etiology of advanced stage prostate cancer.  相似文献   
97.
98.
99.
The outbreaks of rabies in humans transmitted by Desmodus rotundus in 2004 and 2005, in the northeast of the Brazilian State of Para, eastern Amazon basin, made this a priority area for studies on this zoonosis. Given this, the present study provides data on this phenomenon in an urban context, in order to assess the possible circulation of the classic rabies virus (RABV) among bat species in Capanema, a town in the Amazon basin. Bats were collected, in 2011, with mist nets during the wet and dry seasons. Samples of brain tissue and blood were collected for virological and serological survey, respectively. None of the 153 brain tissue samples analyzed tested positive for RABV infection, but 50.34% (95% CI: 45.67-55.01%) of the serum samples analyzed were seropositive. Artibeus planirostris was the most common species, with a high percentage of seropositive individuals (52.46%, 95% CI: 52.31 52.60%). Statistically, equal proportions of seropositive results were obtained in the rainy and dry seasons (c2 = 0.057, d.f. = 1, p = 0.88). Significantly higher proportions of males (55.96%, 95% CI: 48.96-62.96%) and adults (52.37%, 95% CI: 47.35-57.39%) were seropositive. While none of the brain tissue samples tested positive for infection, the high proportion of seropositive specimens indicates that RABV may be widespread in this urban area.  相似文献   
100.
The aetiology of vitiligo has not been fully elucidated, and several hypotheses have been investigated; among them, the most explored assumes an autoimmune basis for the disease. Supporting this hypothesis is the frequent co-occurrence of autoimmune diseases with vitiligo. In addition, various genetic loci associated with vitiligo harbour key immune response genes. Our general hypothesis is that autoimmunity-associated genes participate in the control of vitiligo susceptibility. To investigate this hypothesis, we tested for association between vitiligo and genes CYP27B1, REL, TNFAIP3 and IL2/IL21, all previously related to autoimmune diseases associated with vitiligo. The study was performed using two independent population samples: a family-based discovery set (211 trios) and a replication set (131 cases/119 controls). Statistically significant association with vitiligo was detected between markers of the REL and IL2 gene in the family-based sample. Both association signals were concentrated among patients displaying autoimmune comorbidity and non-segmental vitiligo. Evidence for validation was detected for IL2 marker. Our findings suggest REL and IL2 as new vitiligo susceptibility genes and reinforce the hypothesis of a shared genetic mechanism controlling vitiligo and other autoimmune diseases.  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