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   1513152篇
  免费   113960篇
  国内免费   6415篇
耳鼻咽喉   17937篇
儿科学   49535篇
妇产科学   39638篇
基础医学   200500篇
口腔科学   38817篇
临床医学   132888篇
内科学   309361篇
皮肤病学   32837篇
神经病学   126516篇
特种医学   64227篇
外国民族医学   275篇
外科学   238515篇
综合类   33829篇
现状与发展   2篇
一般理论   419篇
预防医学   124607篇
眼科学   30936篇
药学   103296篇
  5篇
中国医学   2918篇
肿瘤学   86469篇
  2018年   34292篇
  2017年   27097篇
  2016年   31346篇
  2015年   15472篇
  2014年   21129篇
  2013年   30998篇
  2012年   43514篇
  2011年   59545篇
  2010年   42550篇
  2009年   35104篇
  2008年   55309篇
  2007年   59795篇
  2006年   40846篇
  2005年   40901篇
  2004年   40266篇
  2003年   40201篇
  2002年   36432篇
  2001年   66486篇
  2000年   68507篇
  1999年   56886篇
  1998年   16967篇
  1997年   15255篇
  1996年   16123篇
  1995年   16366篇
  1994年   15221篇
  1993年   14230篇
  1992年   47195篇
  1991年   45885篇
  1990年   44155篇
  1989年   41938篇
  1988年   38849篇
  1987年   38174篇
  1986年   35921篇
  1985年   34703篇
  1984年   26418篇
  1983年   22164篇
  1982年   13893篇
  1981年   12459篇
  1980年   11762篇
  1979年   23562篇
  1978年   17091篇
  1977年   14397篇
  1976年   13198篇
  1975年   13733篇
  1974年   16123篇
  1973年   15410篇
  1972年   14187篇
  1971年   13053篇
  1970年   11915篇
  1969年   11136篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Background : The clinical course of chronic hepatitis B is variable. Patients with hepatic decompensation, bridging necrosis or an alpha-fetoprotein level greater than 100 ng/mL during an exacerbation of hepatitis have a high risk of developing cirrhosis. This study was conducted to evaluate the effect of colchicine in the prevention of cirrhosis in such patients.
Methods : Patients with risk factor(s) were randomized to receive either colchicine 5 mg/week or no specific treatment, the end point being development of cirrhosis.
Results : After a follow up period of 4 years, the treatment group had a marked reduction in exacerbations of acute hepatitis (32% vs. 63%/patient/year, P <0.005). Seven out of 38 patients in the treatment group and 10 out of 27 patients in the control group developed cirrhosis. The calculated cumulative incidence of cirrhosis by the end of first, second, third and fourth years in the treatment group was 8.7, 18.6, 32 and 32%, respectively. The corresponding figures in the control group were 30, 35.5, 46.3 and 73.2%, respectively, with a P -value of 0.057.
Conclusions : The results suggest that colchicine may prevent cirrhosis in chronic hepatitis B patients with risk factor(s), possibly by suppressing exacerbations of hepatitis through an anti-inflammatory effect.  相似文献   
152.
153.
154.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.  相似文献   
155.
The medical world would seem to be one of increasing technology and shrinking financial resources. New tests and therapies constantly appear on the market. Most have been examined for efficacy and side effects. The real question is: where does the new test or therapy fit in with all previous products? Decision analysis is a mathematical tool adapted to assess the relative cost-effectiveness of complex diagnostic and therapeutic strategies.  相似文献   
156.
Mice killed shortly after receiving c. 2000 spores of a type E strain of Clostridium botulinum per os were incubated at one of five chosen temperatures together with bottles of cooked meat medium seeded with a similar inoculum. After incubation the rotting carcasses were homogenized. Sterile membrane filtrates of the homogenates (10%, w/v) and pure cultures were then titrated for toxicity. Some of the main findings were confirmed with two further type E strains. Toxicity produced at 37 degrees C was poor in both carcasses and cultures (200-20,000 mouse intraperitoneal LD/g or ml). It was good in both systems at 30 and 23 degrees C, usually reaching 20,000-200,000 LD/g or ml, and in carcasses occasionally more; at 30 degrees C maximal toxicity was reached more quickly in carcasses than in cultures. Prolonged incubation (36-118 days) at 30 or 23 degrees C resulted in complete loss of toxicity in virtually all carcasses but not in cultures. At 16 degrees C the development of toxicity in carcasses was strikingly greater than in cultures. At 9 degrees C neither system produced more than slight toxicity after prolonged incubation. Trypsinization increased the toxicity of cultures but not usually of carcasses. Unfiltered carcass homogenate (10%, w/v) with maximal intraperitoneal toxicity was harmless for mice by mouth in doses of 0.25 ml. These findings differed in important respects from those made earlier with a type C strain.  相似文献   
157.
Herpes zoster probably occurs more often than generally thought. Since it produces a radicular distribution of pain, it should be included in the differential diagnosis of radiculopathy. A case is presented in which evaluating the radicular low back pain before the characteristic rash appears was misleading. Careful history-taking concerning the exact nature of the pain and sensory changes is needed to differentiate between zoster and radiculopathy, if no rash is evident.  相似文献   
158.
159.
160.
Eledoisin has been tried as a possible treatment for dry eye based on the hypothesis that it pharmacologically stimulates tear secretion when topically applied to the eye. To determine if topically applied eledoisin pharmacologically stimulates orbital lacrimal secretion, the orbital lacrimal gland excretory duct of normal rabbits was cannulated, and eledoisin was applied topically with and without prior administration of proparacaine. To determine if topically applied eledoisin stimulated accessory lacrimal gland secretion, isotonic buffer with and without eledoisin was tested in a rabbit model with only accessory lacrimal tissue remaining after the administration of proparacaine. Topically applied eledoisin did not pharmacologically stimulate lacrimal secretion but rather increased lacrimal gland secretion only in non-anesthetized eyes through a sensory reflex mechanism that is blocked by proparacaine.  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