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   18077篇
  免费   1170篇
  国内免费   129篇
耳鼻咽喉   155篇
儿科学   412篇
妇产科学   351篇
基础医学   2116篇
口腔科学   727篇
临床医学   1627篇
内科学   3867篇
皮肤病学   391篇
神经病学   1136篇
特种医学   415篇
外国民族医学   5篇
外科学   2417篇
综合类   473篇
一般理论   14篇
预防医学   1511篇
眼科学   727篇
药学   1758篇
中国医学   204篇
肿瘤学   1070篇
  2024年   20篇
  2023年   218篇
  2022年   226篇
  2021年   1050篇
  2020年   705篇
  2019年   848篇
  2018年   1008篇
  2017年   713篇
  2016年   772篇
  2015年   781篇
  2014年   1046篇
  2013年   1205篇
  2012年   1642篇
  2011年   1690篇
  2010年   998篇
  2009年   762篇
  2008年   1108篇
  2007年   984篇
  2006年   828篇
  2005年   704篇
  2004年   554篇
  2003年   454篇
  2002年   389篇
  2001年   48篇
  2000年   58篇
  1999年   58篇
  1998年   50篇
  1997年   44篇
  1996年   43篇
  1995年   35篇
  1994年   18篇
  1993年   33篇
  1992年   23篇
  1991年   17篇
  1990年   19篇
  1989年   20篇
  1988年   17篇
  1987年   10篇
  1986年   13篇
  1985年   12篇
  1984年   19篇
  1983年   17篇
  1982年   16篇
  1981年   11篇
  1980年   12篇
  1979年   13篇
  1978年   10篇
  1976年   10篇
  1974年   8篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
53.
54.
STUDY OBJECTIVE: The presence of fimbrial pathology in advanced endometriosis is clearly understood. However, little is known about the prevalence of fimbrial pathology in early stages of endometriosis. The purpose of this study is to determine the prevalence of fimbrial pathology in patients with infertility with early stages of endometriosis. DESIGN: Historical cohort study (Canadian Task Force classification II/III). SETTING: Tertiary referral center. PATIENTS: The study group (Group 1) consisted of 315 infertile women who were found to have stage I or stage II endometriosis, and the control group (Group 2) consisted of 152 infertile women without endometriosis (Group 2). INTERVENTION: Laparoscopic evaluation for the presence and type of fimbrial pathology. MEASUREMENTS AND MAIN RESULTS: The prevalence of fimbrial pathology was significantly higher in infertile patients with early stages of endometriosis (50.2%) compared with infertile patients with no endometriosis (17.8%, p <.0001). CONCLUSION: These preliminary data suggest the presence of fimbrial pathology in many patients with early stages of endometriosis. Such pathology may act as a mechanical factor interfering with the ovum pick-up mechanism.  相似文献   
55.
The effects of tetracaine (10–50 M) and ryanodine (0.1–10 M) were tested on the slow outward K+ current (I so) and the mechanical tension of isolated frog muscle fibres in a voltage-clamp device (double mannitol-gap) connected to a mechanoelectric transducer. In the concentration range tested, both drugs induced a simultaneous inhibition of tension and current. In all cases the effect on tension was twice that on current. The tetracaine-induced current and tension blocks were fully reversible and dose-dependent. In contrast the ryanodine effects on current and tension were not reversible and did not exhibit a dose dependence except for the delay before the onset of the response, which was shortened when the concentration was raised. Linear regression analysis of the time-dependent and dose-dependent effects of both drugs indicated a strong correlation between the decreases in tension and current. It is concluded that the slow outward current is partly under the control of the Ca2+ release from sarcoplasmic reticulum during contraction.  相似文献   
56.
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   
57.

Background  

Maharishi Amrit Kalash (MAK) 5, one of the Ayurvedic food supplements, belongs to a group of substances known as Rasayana. MAK5 and other Rasayanas are believed to enhance the body's resistance to infections and disease, and enhance longevity. In this study, we determined the effects of administration of MAK5, one of the Ayurvedic food supplements on immune functions in young and old mice.  相似文献   
58.
Complete lecithin cholesterol acyltransferase (LCAT) deficiency is a rare genetic cause of extreme reduction in high density lipoproteins and there is a high prevalence of chronic renal dysfunction that may progress to renal failure. Previous in vitro studies suggest the vesicular lipoprotein X (LpX) particles commonly seen in LCAT-deficient plasmas may be causative. To test this hypothesis, we have generated a novel murine model that selectively accumulate LpX in the circulation by cross breeding the sterol regulatory element binding protein (SREBP) 1a transgenic mice (S+) with the LCAT knockout (lcat-/-) mice. Fast protein liquid chromatography fractionation of pooled plasma lipids revealed that virtually all cholesterol is concentrated in the very low density lipoprotein (VLDL)-sized fractions. These fractions are enriched in free cholesterol and phospholipid but extremely poor in triglyceride. Electron microscopy of the d <1.063 g/ml fraction of the S+lcat-/- mice revealed abnormal large vesicular particles, suggestive of LpX. The S+lcat-/- mice developed glomerular lesions spontaneously evident at 6 months with glomerular and tubulointerstitial lipid-deposits. Immunohistochemical staining with RhoA showed marked positive focal staining in glomeruli in the S+lcat-/- mice and undetectable in the S+/lcat+/+ control. By 10 months of age, the kidneys showed progressive glomerular injury including segmental foam cell infiltrates, mesangial expansion, and hyalinosis. Renal abnormalities are very similar to those seen in human LCAT deficiency. We conclude that the selective high-level accumulation of plasma LpX in the S+lcat-/- mice is strongly associated with a spontaneous glomerulopathy, providing in vivo evidence that LpX contributes to the LCAT deficiency-related nephropathy.  相似文献   
59.
Finite element analysis is a powerful tool for investigating the biomechanics of atherosclerosis and has thereby provided an improved understanding of acute myocardial infarction. Structural analysis of arterial walls is traditionally performed using geometry contours derived from histology. In this paper we demonstrate the first use of a new imaging technique, optical coherence tomography (OCT), as a basis for finite element analysis. There are two primary benefits of OCT relative to histology: 1) imaging is performed without excessive tissue handling, providing a more realistic geometry than histology and avoiding structural artifacts common to histologic processing, and 2) OCT imaging can be performed in vivo, making it possible to study disease progression and the effect of therapeutic treatments in animal models and living patients. Patterns of mechanical stress and strain distributions computed from finite element analysis based on OCT were compared with those from modeling based on "gold standard" histology. Our results indicate that vascular structure and composition determined by OCT provides an adequate basis for investigating the biomechanical factors relevant to atherosclerosis and acute myocardial infarction.  相似文献   
60.
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