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   10609篇
  免费   645篇
  国内免费   80篇
耳鼻咽喉   134篇
儿科学   279篇
妇产科学   338篇
基础医学   1264篇
口腔科学   290篇
临床医学   905篇
内科学   2450篇
皮肤病学   183篇
神经病学   453篇
特种医学   329篇
外国民族医学   1篇
外科学   1536篇
综合类   326篇
一般理论   8篇
预防医学   733篇
眼科学   356篇
药学   990篇
中国医学   105篇
肿瘤学   654篇
  2023年   141篇
  2022年   377篇
  2021年   506篇
  2020年   326篇
  2019年   425篇
  2018年   477篇
  2017年   330篇
  2016年   318篇
  2015年   290篇
  2014年   456篇
  2013年   549篇
  2012年   788篇
  2011年   793篇
  2010年   461篇
  2009年   369篇
  2008年   578篇
  2007年   584篇
  2006年   477篇
  2005年   453篇
  2004年   400篇
  2003年   335篇
  2002年   304篇
  2001年   150篇
  2000年   136篇
  1999年   140篇
  1998年   65篇
  1997年   41篇
  1996年   46篇
  1995年   47篇
  1994年   48篇
  1993年   32篇
  1992年   71篇
  1991年   66篇
  1990年   79篇
  1989年   63篇
  1988年   64篇
  1987年   62篇
  1986年   62篇
  1985年   46篇
  1984年   40篇
  1983年   24篇
  1982年   23篇
  1980年   24篇
  1979年   30篇
  1977年   27篇
  1976年   23篇
  1974年   15篇
  1973年   17篇
  1970年   19篇
  1969年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
A methodological approach to the classification of dermoscopy images.   总被引:2,自引:0,他引:2  
In this paper a methodological approach to the classification of pigmented skin lesions in dermoscopy images is presented. First, automatic border detection is performed to separate the lesion from the background skin. Shape features are then extracted from this border. For the extraction of color and texture related features, the image is divided into various clinically significant regions using the Euclidean distance transform. This feature data is fed into an optimization framework, which ranks the features using various feature selection algorithms and determines the optimal feature subset size according to the area under the ROC curve measure obtained from support vector machine classification. The issue of class imbalance is addressed using various sampling strategies, and the classifier generalization error is estimated using Monte Carlo cross validation. Experiments on a set of 564 images yielded a specificity of 92.34% and a sensitivity of 93.33%.  相似文献   
23.
This study reports an opinion survey of 211 nonpsychiatrist physicians in two general hospitals who estimated that 16.1% of their patients have psychiatric disorders and that they spent 13.8% of their time in treating the psychiatric components of their patients' illnesses. Physicians indicated that anxiety and psychosomatic and depressive illness were the most frequent psychiatric disorders and that one-third of them would personally treat such disorders without referral to psychiatric consultation. The findings also suggest that adequate undergraduate psychiatric education was associated with increased recognition of psychiatric disorders and more preference for their personal treatment. In addition, it provides a possible explanation for the discrepancy between the high prevalence of psychiatric disorders in general hospital patients and the low referral rate to psychiatric consultation.  相似文献   
24.
A 17-year-old male presented to a local hospital with symptoms of pneumonia and a hacking cough productive of yellow sputum. Direct examination of a bronchial lavage sample revealed organisms morphologically consistent with Blastomyces dermatitidis, which was confirmed by culture. The patient was placed on intravenous antifungal therapy and his condition improved dramatically. OBJECTIVES: to describe the gross and microscopic morphologies of both yeast and mold forms of B. dermatitidis; to identify B. dermatitidis given patient history, and microscopic and colony morphology; to describe the symptoms of primary pulmonary infections caused by B. dermatitidis, and to name additional tissues typically affected by the systemic pathogen.  相似文献   
25.
Geographical variations in the incidence of disease are of considerable theoretical and practical importance. It has been claimed that the distribution of acute lymphoblastic leukemia (ALL) phenotypes in Saudi Arabia is different from that recorded in the Western literature. One hundred and twelve (112) patients under 15 years of age, diagnosed as ALL between January 1992 and May 1994 had immunophenotypes performed on their blast cells. Common ALL (cALL) together with pre-B-ALL, formed 86.5% of the total; B-cell 3%, T-cell 6% and null cell 4.5%. These figures are not significantly different from the Western literature. A previous claim from this institution in 1990, that both null and B-cell ALL were significantly increased compared with elsewhere, is not supported by the present figures. Age and sex distribution, and FAB classification, L1 77%, L2 20% and L3 3%, were also of the same order as described elsewhere and, in particular, there was no increase in the frequency of L3 subtype.  相似文献   
26.
Reaction of 6-(acetoxymethyl)-2,4-dichloropyrido[3,2-d]pyrimidine (I) with some nucleophiles was investigated. When I reacted with sodium azide afforded 2,4-diazido derivative (II). Treatment of II with sodium hydroxide underwent cyclization of the 2-azido group to tetrazolo, replacement of 4-azido group by hydroxide ion, and hydrolysis of 6-acetoxy moiety to hydroxy methyl derivative (III). While, reaction of I with hydrazine hydrate resulted in the formation of 2,4-dihydrozino-6-hydroxymethyl derivative (IV).  相似文献   
27.
The Src-homology 2 domain-containing, leukocyte-specific phosphoprotein of 76 kDa (SLP-76) is a hematopoietic adaptor that plays a central role during immunoreceptor-mediated activation of T lymphocytes and mast cells and collagen receptor-induced activation of platelets. Despite similar levels of expression in macrophages, SLP-76 is not required for Fc receptor for immunoglobulin G (IgG; FcgammaR)-mediated activation. We hypothesized that the related adaptor SLP-65, which is also expressed in macrophages, may compensate for the loss of SLP-76 during FcgammaR-mediated signaling and functional events. To address this hypothesis, we examined bone marrow-derived macrophages (BMM) from wild-type (WT) mice or mice lacking both of these adaptors. Contrary to our expectations, SLP-76(-/-) SLP-65(-/-) BMM demonstrated normal FcgammaR-mediated activation, including internalization of Ig-coated sheep red blood cells and production of reactive oxygen intermediates. FcgammaR-induced biochemical events were normal in SLP-76(-/-) SLP-65(-/-) BMM, including phosphorylation of phospholipase C and the extracellular signaling-regulated kinases 1 and 2. To determine whether macrophages functioned normally in vivo, we infected WT and SLP-76(-/-) SLP-65(-/-) mice with sublethal doses of Listeria monocytogenes (LM), a bacterium against which the initial host defense is provided by activated macrophages. WT and SLP-76(-/-) SLP-65(-/-) mice survived acute, low-dose infection and showed no difference in the number of liver or spleen LM colony-forming units, a measure of the total body burden of this organism. Taken together, these data suggest that neither SLP-76 nor SLP-65 is required during FcgammaR-dependent signaling and functional events in macrophages.  相似文献   
28.
29.
The present study was designed to compare the anatomical parameters of the cardiopulmonary system in three different lines of chickens with different susceptibility to ascites syndrome. Eggs from three different genetic lines-commercial broiler and layer lines and one native to Iran--were incubated and hatched, and 1-day-old chicks used. The relative heart and lung weights, the volumes of the heart, lung and thorax cavity, the incidence of ascites, and the related physiological parameters in these chickens were followed. Lung weight as a percentage of body weight, the relative lung and heart volume, and the volumes of the thorax cavity, before and after removing heart and lung tissues, were lower in fast-growing broiler chickens compared with the layer and native chickens. Additionally, most of these parameters (e.g. relative lung weight, lung volume and thorax cavity) were significantly decreased with age in broiler chickens but were increased in layer and native chickens, which was concomitant with the incidence of ascites in broiler chickens. Our data indicate that all cardiopulmonary parameters investigated are extremely unfavourable to broiler chickens and suggest a reduction in gas exchange area in broilers, and therefore higher susceptibility to pulmonary hypertension and ascites.  相似文献   
30.

Background  

Osteoclasts (OCs) are involved in rheumatoid arthritis and in several pathologies associated with bone loss. Recent results support the concept that some medicinal plants and derived natural products are of great interest for developing therapeutic strategies against bone disorders, including rheumatoid arthritis and osteoporosis. In this study we determined whether extracts of Emblica officinalis fruits display activity of possible interest for the treatment of rheumatoid arthritis and osteoporosis by activating programmed cell death of human primary osteoclasts.  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