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   21843篇
  免费   1318篇
  国内免费   94篇
耳鼻咽喉   341篇
儿科学   403篇
妇产科学   451篇
基础医学   3238篇
口腔科学   1964篇
临床医学   1703篇
内科学   4520篇
皮肤病学   480篇
神经病学   1430篇
特种医学   405篇
外科学   2666篇
综合类   56篇
一般理论   8篇
预防医学   2668篇
眼科学   308篇
药学   1664篇
中国医学   258篇
肿瘤学   692篇
  2024年   25篇
  2023年   226篇
  2022年   422篇
  2021年   787篇
  2020年   534篇
  2019年   685篇
  2018年   910篇
  2017年   606篇
  2016年   684篇
  2015年   738篇
  2014年   959篇
  2013年   1199篇
  2012年   1797篇
  2011年   2185篇
  2010年   1046篇
  2009年   721篇
  2008年   1324篇
  2007年   1354篇
  2006年   1142篇
  2005年   1019篇
  2004年   845篇
  2003年   713篇
  2002年   689篇
  2001年   397篇
  2000年   445篇
  1999年   311篇
  1998年   83篇
  1997年   82篇
  1996年   52篇
  1995年   55篇
  1994年   55篇
  1993年   43篇
  1992年   134篇
  1991年   104篇
  1990年   88篇
  1989年   96篇
  1988年   59篇
  1987年   57篇
  1986年   60篇
  1985年   52篇
  1984年   38篇
  1983年   23篇
  1980年   26篇
  1979年   26篇
  1978年   31篇
  1976年   23篇
  1973年   28篇
  1971年   23篇
  1969年   26篇
  1967年   23篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Melatonin, the main hormone produced by the pineal gland, is secreted in a circadian manner (24‐hr period), and its oscillation influences several circadian biological rhythms, such as the regulation of clock genes expression (chronobiotic effect) and the modulation of several endocrine functions in peripheral tissues. Assuming that the circadian synchronization of clock genes can play a role in the regulation of energy metabolism and it is influenced by melatonin, our study was designed to assess possible alterations as a consequence of melatonin absence on the circadian expression of clock genes in the epididymal adipose tissue of male Wistar rats and the possible metabolic repercussions to this tissue. Our data show that pinealectomy indeed has impacts on molecular events: it abolishes the daily pattern of the expression of Clock, Per2, and Cry1 clock genes and Pparγ expression, significantly increases the amplitude of daily expression of Rev‐erbα, and affects the pattern of and impairs adipokine production, leading to a decrease in leptin levels. However, regarding some metabolic aspects of adipocyte functions, such as its ability to synthesize triacylglycerols from glucose along 24 hr, was not compromised by pinealectomy, although the daily profile of the lipogenic enzymes expression (ATP‐citrate lyase, malic enzyme, fatty acid synthase, and glucose‐6‐phosphate dehydrogenase) was abolished in pinealectomized animals.  相似文献   
6.
Objective: To assess the quality of images and video clips of fetal central nervous (CNS) structures obtained by ultrasound and transmitted via tele-ultrasound from Brazil to Australia.

Methods: In this cross-sectional study, 15 normal singleton pregnant women between 20 and 26 weeks were selected. Fetal CNS structures were obtained by images and video clips. The exams were transmitted in real-time using a broadband internet and an inexpensive video streaming device. Four blinded examiners evaluated the quality of the exams using the Likert scale. We calculated the mean, standard deviation, mean difference, and p values were obtained from paired t tests.

Results: The quality of the original video clips was slightly better than that observed by the transmitted video clips; mean difference considering all observers = 0.23 points. In 47/60 comparisons (78.3%; 95% CI?=?66.4–86.9%) the quality of the video clips were judged to be the same. In 182/240 still images (75.8%; 95% CI?=?70.0–80.8%) the scores of transmitted image were considered the same as the original.

Conclusion: We demonstrated that long distance tele-ultrasound transmission of fetal CNS structures using an inexpensive video streaming device provided images of subjective good quality.  相似文献   
7.
The spatial distribution of enteroparasitosis in an indigenous village from Paraná was evaluated to identify areas of risk for these infections. A cross-sectional study (from November 2010 to June 2011) was performed using Three Faecal Test® and Kato &; Katz method and a questionnaire on housing and hygiene conditions was administered. Local geostatistical analyses were performed to determine the spatial distribution of intestinal parasitic infections. The overall prevalence of enteroparasites was 67.2?% (457/680), and the most prevalent taxa were Ascaris lumbricoides (48.8?%) and Trichuris trichiura (44.7?%). The prevalence of heavy infection by soil-transmitted helminths was 3.6?% and the families lived in houses with an average of 5.1 residents and < 2 bedrooms per household. The average number of species per individual present spatial heterogeneity with the highest values (≥0.8) in areas with high clustering of residences. The visualization of the spatial distribution of intestinal parasites in this indigenous village is an important contribution to determining health risk areas and planning decisions and services.  相似文献   
8.
9.
10.
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