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   583篇
  免费   44篇
  国内免费   1篇
耳鼻咽喉   1篇
儿科学   27篇
妇产科学   26篇
基础医学   73篇
口腔科学   33篇
临床医学   95篇
内科学   66篇
皮肤病学   15篇
神经病学   61篇
特种医学   24篇
外科学   40篇
预防医学   64篇
眼科学   9篇
药学   31篇
中国医学   1篇
肿瘤学   62篇
  2024年   4篇
  2023年   5篇
  2022年   4篇
  2021年   10篇
  2020年   18篇
  2019年   16篇
  2018年   22篇
  2017年   24篇
  2016年   21篇
  2015年   18篇
  2014年   16篇
  2013年   40篇
  2012年   47篇
  2011年   52篇
  2010年   22篇
  2009年   17篇
  2008年   35篇
  2007年   34篇
  2006年   44篇
  2005年   41篇
  2004年   19篇
  2003年   26篇
  2002年   27篇
  2001年   1篇
  2000年   2篇
  1999年   2篇
  1998年   6篇
  1997年   9篇
  1996年   4篇
  1995年   6篇
  1994年   2篇
  1993年   3篇
  1992年   2篇
  1991年   5篇
  1990年   5篇
  1989年   1篇
  1988年   3篇
  1987年   1篇
  1985年   1篇
  1984年   3篇
  1983年   1篇
  1981年   4篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1975年   1篇
排序方式: 共有628条查询结果,搜索用时 15 毫秒
1.
2.
Mutations in the C1-inhibitor (C1-INH) gene, leading to low functional levels of C1-inhibitor protein, cause hereditary angioedema (HAE). The disease is characterized by episodic edema in a number of organs. Typically, swellings occur in extremities and face, often accompanied by crampy abdominal pain. Laryngeal edema may lead to suffocation. Type II HAE patients have low functional C1-INH values stemming from only one normal allele. Antigenic C1-INH values, however, are normal or increased owing to the presence of a dysfunctional protein from the mutated allele. The mutations are usually found in exon 8 coding for the amino acids near the reactive centre (P1). Previously, no mutations in the C1-INH gene had been published from the Scandinavian countries. In this work, exon 8 of the C1-inhibitor gene was sequenced in members of two different kindreds, from western and northern Norway, who were suffering from HAE type II. A common point mutation was found within the bait region encoding the reactive centre. The codon CGC was converted to TGC at position 17 970, corresponding to an Arg → Cys replacement which reportedly is the second most frequent type II HAE mutation. This information was utilized to develop a mutation-specific polymerase chain reaction (PCR) for the identification of affected family members. The antisense 17-mer primer (5'-AAGACCAGCAGGGTGCA-3') was successfully applied and AmpliTaq Gold was used in the PCR.  相似文献   
3.
A longitudinal study of semen quality in pesticide spraying danish farmers   总被引:9,自引:0,他引:9  
It was hypothesized that occupational exposure to pesticides during a spraying season causes changes in semen quality that might be detected in a longitudinal study. We analyzed the within-person changes in semen quality and reproductive hormones across a spraying season in groups of farmers using and not using pesticides. A total of 248 men collected two semen samples (participation rate: 32%). The median sperm concentration declined significantly from the first to the second sample in both groups, but there was no statistical difference in the decline between the two groups, unadjusted or adjusted. Only minor changes were found in sperm morphology, vitality, motility, sperm chromatin denaturation (SCSA), and reproductive hormones, and the differences in changes between the two groups were nonsignificant, or, in the opposite direction to the expected. There was no relation between the changes in sperm parameters in relation to pesticide exposure variables. In conclusion, use of pesticides by Danish farmers is not a likely cause of short-term effects on semen quality and reproductive hormones.  相似文献   
4.
The hepatocyte growth factor (HGF) has been crucially implicated in the development of proliferative retinal diseases; however, it is unclear whether retinal glial cells express or respond to HGF. Therefore, we examined the expression of HGF and of the receptor for HGF, c-Met, by immunohistochemical costaining with glial fibrillary acidic protein (GFAP) in epiretinal membranes of patients with proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR), respectively. Furthermore, it was determined whether cells of the human retinal glial cell line, MIO-M1, secrete HGF protein, and whether HGF stimulates proliferation and chemotaxis, and secretion of the vascular endothelial growth factor (VEGF). Neuroretinas of patients with PVR express elevated mRNA level for HGF in comparison to control retinas. In epiretinal membranes of patients with PVR or PDR, immunoreactivity for HGF and for c-Met, respectively, partially colocalized with immunoreactivity for GFAP. Fetal bovine serum and basic fibroblast growth factor, but not heparin-binding epidermal or platelet-derived growth factors, evoked HGF secretion by cultured retinal glial cells. HGF displayed only a marginal effect on cell proliferation while it stimulated chemotaxis. HGF promoted the secretion of VEGF, via activation of the phosphatidylinositol-3 kinase. It is concluded that glial cells in epiretinal membranes express both HGF protein and c-Met receptors. The results suggest an autocrine/paracrine role of HGF in glial cell responses during proliferative vitreoretinal disorders as well as in retinal neovascularization, by stimulating of VEGF release.  相似文献   
5.
6.
Summary Diazoxide significantly decreased the blood pressure and relaxed the uterine muscle in anaesthetized normotensive rats. A marked elevation of blood glucose followed the intravenous injection of diazoxide. The hyperglycemic and the uterine relaxing response could be significantly decreased by injection of propranolol prior to diazoxide. The hypotensive effect was not diminished by propranolol, however. In liver and uterus the content of cAMP was increased following diazoxide treatment in vivo. The rise in cAMP could be completely inhibited by propranolol, indicating a -receptor stimulation being the cause of the cAMP elevation.  相似文献   
7.
In this study, a specific monoclonal antibody was used to immunohistochemically investigate correlated expression of the cell cycle promoter cyclin E and the proliferation marker Ki-67 in benign extravillous trophoblast and gestational trophoblastic lesions. Our data show that cyclin E is expressed in the normal extravillous trophoblast, with strongest levels of expression in the cell columns of anchoring villi. Differences could be observed in expression of Ki-67 in both normal extravillous trophoblast and gestational trophoblastic lesions. In the extravillous trophoblast of the cell columns, expression of cyclin E started more distal compared with Ki-67 and was maintained (with less intensity) into the deeper layers of interstitial trophoblast. In the benign trophoblastic lesions (exaggerated placental site [EPS] and placental site nodule [PSN]) and in the trophoblast proliferations on the surface of hydropic villi of hydatidiform moles (HM), the percentage of cells expressing cyclin E was higher than of those expressing Ki-67. The same observation could be made for a case of placental site trophoblastic tumor (PSTT). In contrast, choriocarcinomas (N=8), which are definitely malignant tumors, showed an opposite pattern, with a much higher percentage of strongly Ki-67-positive cells compared with cyclin E-positive cells. We conclude that cyclin E is expressed in benign extravillous trophoblast and gestational trophoblastic lesions, where a ratio cyclin E/Ki-67<1 characterizes choriocarcinomas, whereas PSTT and the benign lesions (HM, EPS, PSN) show expression of cyclin E in a higher percentage of cells than Ki-67 (cyclin E/Ki-67 ratio >1).  相似文献   
8.
9.
10.
The purpose of this study was to determine the sensitivity, specificity, positive and negative predictive values for Corah's Dental Anxiety Scale (DAS) and two modified versions of it (MDAS; MDAS/4). A questionnaire was mailed to a simple random sample of 1,190 25-year-old residents in the west of Norway in 1997. Half the sample received DAS, the other half MDAS. The response rate after one reminder was 62%. The respondents completed the scales, gave demographic particulars and answered one question about dental visiting habits during the last 5 years plus an open-ended question about reasons for nonattendance. Using the answers to the latter question as validating criterion, it was found that, for all scales, sensitivity decreased while specificity improved when changing from a liberal to a stringent cut-off point. The scales gave low positive predictive values (≤0.26), but high negative predictive values (≥0.98). Since DAS and MDAS/4 gave almost identical findings, the two samples were combined. At a cut-off point ≥13 sensitivity was 0.83, specificity 0.84, positive predictive value 0.18 and negative predictive value 0.99. The corresponding estimates when the cut-off point was ≥15 were 0.67, 0.90, 0.22 and 0.98. It is concluded that, in this test, DAS and the two versions of MDAS gave acceptable, or near acceptable sensitivity, specificity and negative predictive values, but far too low positive predictive values to be useful for prediction at the individual level.  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