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   33091篇
  免费   2137篇
  国内免费   138篇
耳鼻咽喉   363篇
儿科学   856篇
妇产科学   686篇
基础医学   4928篇
口腔科学   2979篇
临床医学   2662篇
内科学   6787篇
皮肤病学   735篇
神经病学   2643篇
特种医学   728篇
外国民族医学   1篇
外科学   3692篇
综合类   366篇
一般理论   8篇
预防医学   3599篇
眼科学   439篇
药学   2366篇
中国医学   319篇
肿瘤学   1209篇
  2023年   346篇
  2022年   753篇
  2021年   1259篇
  2020年   871篇
  2019年   1093篇
  2018年   1286篇
  2017年   954篇
  2016年   1004篇
  2015年   1168篇
  2014年   1515篇
  2013年   1793篇
  2012年   2642篇
  2011年   2849篇
  2010年   1499篇
  2009年   1167篇
  2008年   1893篇
  2007年   1824篇
  2006年   1639篇
  2005年   1346篇
  2004年   1172篇
  2003年   1047篇
  2002年   922篇
  2001年   619篇
  2000年   669篇
  1999年   534篇
  1998年   204篇
  1997年   140篇
  1996年   142篇
  1995年   132篇
  1994年   104篇
  1993年   83篇
  1992年   248篇
  1991年   230篇
  1990年   217篇
  1989年   205篇
  1988年   191篇
  1987年   140篇
  1986年   128篇
  1985年   133篇
  1984年   107篇
  1983年   87篇
  1979年   91篇
  1978年   76篇
  1977年   48篇
  1975年   54篇
  1974年   65篇
  1973年   65篇
  1970年   63篇
  1969年   52篇
  1967年   62篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
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   
4.
5.
6.
7.
We study the image formation of vibro-acoustography systems based on a concave sector array transducer taking into account depth-of-field effects. The system point-spread function (PSF) is defined in terms of the acoustic emission of a point-target in response to the dynamic radiation stress of ultrasound. The PSF on the focal plane and the axis of the transducer are presented. To extend the obtained PSF to the 3D-space, we assume it is a separable function in the axial direction and the focal plane of the transducer. In this model, an image is formed through the 3D convolution of the PSF with an object function. Experimental vibro-acoustography images of a breast phantom with lesion-like inclusions were compared with simulated images. Results show that the experimental images are in good agreement with the proposed model.  相似文献   
8.
9.
BACKGROUND: Oral hairy leukoplakia (OHL) may be an indicator of the progression of Human Immunodeficiency Virus (HIV)-induced immuno-depression, and the evaluation of risk factors leading to OHL is important in the management of these HIV-infected patients. However, there are few studies that analyze risk factors leading to OHL in the Brazilian population. The aim of this case-control study is to present data about prevalence rates and risk factors leading to OHL in a sample of HIV-infected adults in Brazil. METHODS: This case-control study included 111 HIV-infected patients treated at a clinic for sexually transmitted diseases and HIV. In the initial examinations with dentists, variables were collected from all patients. Diagnosis of OHL was performed in accordance with the International Classification System and cytological features. The Fisher and the chi-squared tests were used for statistical analysis. The proportional prevalence and odds ratio were estimated. RESULTS: Outcome presented a positive, statistically significant association among the presence of OHL and viral load of 3000 copies/mul or greater (P = 0.0001; odds ratio (OR) = 5.8), presence of oral candidiasis (P = 0.0000; OR = 11.1), previous use of fluconazole (P = 0.0000; OR = 24.6), and use of systemic acyclovir (P = 0.032; OR = 4.3). Antiretroviral medication presented a negative, statistically significant association with the presence of OHL (P = 0.002; OR = 8.4). CONCLUSIONS: Prevalence of OHL was 28.8%. Viral load, oral candidiasis, previous use of fluconazole, and systemic acyclovir were determined to be risk factors for OHL. Antiretroviral medication proved to be protective against the development of OHL.  相似文献   
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