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   53723篇
  免费   4148篇
  国内免费   135篇
耳鼻咽喉   400篇
儿科学   2171篇
妇产科学   1449篇
基础医学   7432篇
口腔科学   1367篇
临床医学   7127篇
内科学   10792篇
皮肤病学   975篇
神经病学   5481篇
特种医学   1295篇
外科学   4902篇
综合类   433篇
一般理论   64篇
预防医学   6028篇
眼科学   752篇
药学   3131篇
  2篇
中国医学   58篇
肿瘤学   4147篇
  2024年   66篇
  2023年   467篇
  2022年   648篇
  2021年   1401篇
  2020年   1014篇
  2019年   1508篇
  2018年   1681篇
  2017年   1331篇
  2016年   1446篇
  2015年   1540篇
  2014年   1983篇
  2013年   2856篇
  2012年   3992篇
  2011年   4140篇
  2010年   2280篇
  2009年   2010篇
  2008年   3405篇
  2007年   3532篇
  2006年   3433篇
  2005年   3238篇
  2004年   3096篇
  2003年   2850篇
  2002年   2578篇
  2001年   580篇
  2000年   488篇
  1999年   555篇
  1998年   594篇
  1997年   451篇
  1996年   398篇
  1995年   391篇
  1994年   298篇
  1993年   301篇
  1992年   322篇
  1991年   295篇
  1990年   264篇
  1989年   220篇
  1988年   215篇
  1987年   175篇
  1986年   174篇
  1985年   158篇
  1984年   157篇
  1983年   143篇
  1982年   148篇
  1981年   152篇
  1980年   126篇
  1979年   112篇
  1978年   89篇
  1977年   68篇
  1976年   70篇
  1974年   52篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Pregnancy has long been considered to have beneficial effects on endometriosis. We describe a patient who underwent emergency exploratory laparotomy at gestation week 35 for rupture of an ovarian endometrioma.  相似文献   
72.
73.
The tumor microenvironment consists of tumor, immune, stromal, and inflammatory cells which produce cytokines, growth factors, and adhesion molecules that promote tumor progression and metastasis. Of particular interest in this setting is interleukin-1 (IL-1), a pleiotropic cytokine with numerous roles in both physiological and pathological states. It is known to be up regulated in many tumor types and has been implicated as a factor in tumor progression via the expression of metastatic and angiogenic genes and growth factors. A number of studies have reported that high IL-1 concentrations within the tumor microenvironment are associated with a more virulent tumor phenotype. Solid tumors in which IL-1 has been shown to be up regulated include breast, colon, lung, head and neck cancers, and melanomas, and patients with IL-1 producing tumors have generally bad prognoses. The exact mechanisms by which IL-1 promotes tumor growth remain unclear, though the protein is believed to act via induction of pro-metastatic genes such as matrix metalloproteinases and through the stimulation of adjacent cells to produce angiogenic proteins and growth factors such as VEGF, IL-8, IL-6, TNFα, and TGFβ. The IL-1 receptor antagonist (IL-1ra) is a naturally occurring inhibitor to IL-1 and acts by binding to the IL-1 receptor without activating it. The protein has been shown to decrease tumor growth, angiogenesis, and metastases in murine xenograft models. Our focus in this review is to summarize the known data on the role of IL-1 in tumor progression and metastasis and the use of IL-1 inhibition as a novel therapeutic approach in the treatment of solid organ malignancies.  相似文献   
74.
75.
76.
77.
The choroid plexuses (CPs) form a protective interface between the blood and the ventricular cerebrospinal fluid (CSF). To probe into the pathways by which CPs provide brain protection, we sought to evaluate the efficiency of glutathione conjugation in this barrier as a mechanism to prevent the entry of blood-borne electrophilic, potentially toxic compounds into the CSF, and we investigated the fate of the resulting metabolites. Rat CPs, as well as human CPs from both fetal and adult brains, displayed high glutathione-S-transferase activities. Using an in vitro model of the blood-CSF barrier consisting of choroidal epithelial cells cultured in a two-chambered device, we showed that glutathione conjugation can efficiently prevent the entry of 1-chloro-2,4-dinitrobenzene (CDNB) into the CSF, a model for electrophilic compounds. The duration of this enzymatic protection was set by the concentration of CDNB to which the epithelium was exposed, and this barrier effect was impaired only on severe epithelial intracellular glutathione and cysteine depletion. The conjugate was excreted from the choroidal cells in a polarized manner, mostly at the blood-facing membrane, via a high-capacity transport process, which is not a rate-limiting step in this detoxification pathway, and which may involve transporters of the ATP-binding cassette c(Abcc) and/or solute carrier 21 (Slc21) families. Supplying the choroidal epithelium at the blood-facing membrane with a therapeutically relevant concentration of N-acetylcysteine sustained this neuroprotective effect. Thus, glutathione conjugation at the CP epithelium coupled with the basolateral efflux of the resulting metabolites form an efficient blood-CSF enzymatic barrier, which can be enhanced by pharmacologically increasing glutathione synthesis within the epithelial cells.  相似文献   
78.
79.
A lipolytic activity for beta-endorphin (beta EP) has been recently suggested both in vitro and in vivo. In our study we evaluated the relationship between beta EP and blood lipid pattern in Type 2 (non-insulin dependent) diabetic patients. Plasma beta EP, together with plasma beta-lipotropin (beta LPH), ACTH, cortisol and plasma insulin (IRI), was measured by RIA after silicic acid plasma extraction and Sephedex G-75 column chromatography. Although reduced beta EP (7.12 +/- 3.8 fmol/ml) and increased beta LPH (9.3 +/- 3.7 fmol/ml) levels were found in diabetic patients, compared to controls (8.53 +/- 3.3 fmol/ml, p less than 0.05 and 8.34 +/- 2.6 fmol/ml, p less than 0.05, respectively), higher plasma beta EP concentrations were demonstrated in hyperlipidemic diabetic patients (10.3 +/- 3.9 fmol/ml) than in patients with normal blood lipid pattern (4.85 +/- 1.45 fmol/ml, p less than 0.001). Several positive correlations between beta EP, plasma free fatty acids (r = 0.75, p less than 0.001), triglycerides (r = 0.84, p less than 0.001) and VLDL (r = 0.80, p less than 0.001) were found in our patients independently of overweight, hypoglycemic treatment, plasma IRI levels and of the degree of metabolic control. A higher prevalence of micro- and macrovascular complications was demonstrated in hyperlipidemic than in normolipidemic patients. Blood lipid disorders might therefore be associated with increased plasma beta EP levels in Type 2 diabetes.  相似文献   
80.
This study examined the relationship between psychological sense of community, social‐support networks, and care‐giver stress and satisfaction among firefighters. No significant gender differences were obtained, but zero‐order correlates demonstrated significant relationships among all four variables. In examining the mediating effects of social‐support satisfaction, partial mediation for psychological sense of community on care‐giver satisfaction was determined, as well as full mediation for psychological sense of community on care‐giver stress. Therefore, firefighters who are satisfied with the support they receive may experience less stress with their care giving than those who experience low levels of support satisfaction. Future studies should assess these relationships more extensively in other areas of civic responsibility among public‐service employees to delineate effective support avenues. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 121–126, 2004.  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