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   2488112篇
  免费   185995篇
  国内免费   4956篇
耳鼻咽喉   35013篇
儿科学   82574篇
妇产科学   71237篇
基础医学   359403篇
口腔科学   69649篇
临床医学   219509篇
内科学   486134篇
皮肤病学   56278篇
神经病学   201807篇
特种医学   96179篇
外国民族医学   793篇
外科学   376763篇
综合类   54488篇
现状与发展   4篇
一般理论   775篇
预防医学   189981篇
眼科学   57129篇
药学   181893篇
  2篇
中国医学   5330篇
肿瘤学   134122篇
  2018年   27335篇
  2017年   20903篇
  2016年   23934篇
  2015年   26476篇
  2014年   36486篇
  2013年   55498篇
  2012年   75324篇
  2011年   80572篇
  2010年   47409篇
  2009年   44071篇
  2008年   76352篇
  2007年   81572篇
  2006年   82276篇
  2005年   80114篇
  2004年   76915篇
  2003年   74043篇
  2002年   72336篇
  2001年   115918篇
  2000年   119439篇
  1999年   99385篇
  1998年   28689篇
  1997年   25781篇
  1996年   25737篇
  1995年   24353篇
  1994年   22440篇
  1993年   21102篇
  1992年   76231篇
  1991年   73848篇
  1990年   71972篇
  1989年   69406篇
  1988年   64074篇
  1987年   62854篇
  1986年   59278篇
  1985年   56744篇
  1984年   42904篇
  1983年   36854篇
  1982年   22344篇
  1981年   19884篇
  1979年   39234篇
  1978年   27850篇
  1977年   23593篇
  1976年   22371篇
  1975年   23878篇
  1974年   28364篇
  1973年   27289篇
  1972年   25759篇
  1971年   23726篇
  1970年   22351篇
  1969年   21142篇
  1968年   19888篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
In the first experiment, 52 sows, each having raised one litter, were randomly assigned to the five following groups: control (nongravid) for pregnancy (CP), 110 d pregnancy (P110), control (nongravid) for lactation (CL), 4-wk lactation with 8 (L8) and with 12 (L12) piglets. In a second experiment, 36 sows, each having raised three litters, were randomly assigned to the following groups: control group (nongravid) fed a low-energy-density, 1% tallow diet (CLED) and two lactating groups, one fed the low-energy-density diet (LLED) and one fed a high-energy-density, 10% tallow diet (LHED). At slaughter, the stomach, small and large intestine and cecum were excised, emptied and freed from fat. Lengths and pre- and post-defatting weights were measured. Portions of tissues were homogenized and analyzed for protein, pepsin, maltase, RNA and DNA. Pregnancy had no effect on the weights of the different components of the gastrointestinal tract. Liver and small intestine weights were larger in lactating sows than in the CL group. Sows nursing 12 piglets had heavier livers than those nursing 8. The fundic mucosa of the latter had higher total pepsin activity and total protein and RNA contents than that of L12 sows. LHED sows had heavier small intestine and lower total pepsin content of the fundic mucosa than LLED sows.  相似文献   
995.
Relatives of 22 schizotypal probands were evaluated for lifetime psychiatric diagnoses. Forty-four (N = 44) of the 97 available relatives were interviewed directly using the Diagnostic Interview Schedule. The rates of psychiatric diagnoses were compared with those of sixty-six (N = 66) of 140 relatives of 30 depressed patients. Family history of mental illness was ascertained by the informant method on the remainder of relatives of both proband groups. The rate of depression found in the relatives of schizotypal patients was 52% in those directly interviewed and 25.7% when informants' reports on unavailable relatives are pooled with direct interview data. These rates were not significantly higher than those found for the relatives of depressed probands (34.8% by direct interview and 21% including reports from informants). The high rates of depression in the relatives of schizotypal probands may indicate that schizotypal personality is associated with affective disorder and not only with schizophrenia. However, the high rates may be due to the presence of depressive character traits in relatives, which inflate the rates of dysthymic disorder and other chronic depressive disorders in the relatives of borderline patients.  相似文献   
996.
Numerous surveys at the national and regional level have demonstrated that large inequalities in infant health status exist in Southern Africa. Few studies have assessed infant mortality at the intra-urban scale of geographic analysis. Comparisons between infant mortality rates from different areas are made even more meaningful if the data are divided into two primary categories based on period-of-death; these being the neonatal and post-neonatal components. This study presents the results of a survey undertaken in Metropolitan Cape Town (population 1.6 million) during 1982. The aim was to determine the spatial variation of neonatal and post-neonatal mortality at the suburb (or community) level within the city. Overall, a total of 36,789 live births and 928 infant deaths were recorded; 53.4% in the neonatal period and 46.6% in the post-neonatal period. The mean infant mortality rate was 25.2 per 1000 live births; the neonatal mortality rate and post-neonatal mortality rate being 13.5/1000 and 11.7/1000, respectively. A marked range in death rates was evident for both components. For the neonatal category it was 0.0-49.9/1000 and 0.0-40.0/1000 for the post-neonatal period. The generally low post-neonatal mortality rate among the 69 suburbs studied has made the neonatal component the dominant contributor to the infant mortality rate. However, in the lowest socio-economic areas the post-neonatal mortality rate was responsible for over 60% of infant deaths.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
997.
Health risks among submarine personnel in the U.S. Navy, 1974-1979   总被引:1,自引:0,他引:1  
This study evaluated health risks associated with U.S. Navy submarine duty by comparing hospitalization rates of submariners with surface ship personnel. The groups were compared using age-adjusted hospitalization rates for 16 major diagnostic categories and several specific diagnoses postulated to be submarine associated. Submarine personnel did not have significantly higher hospitalization rates for any diagnostic categories nor for any of the submarine-associated illnesses. Submariner relative risk of hospital admissions was greater for a few selected diagnoses but statistical significance was not attained. Submarine personnel had lower hospitalization rates for nearly all of the diagnostic categories examined. Reasons for these lower rates may be stringent screening of submariners, higher levels of education among submariners, difficulty of evacuation from a submarine, and the healthy-worker effect. The health status of U.S. Navy personnel does not seem to be adversely affected by submarine duty.  相似文献   
998.
Results of an examination of 39 patients are described and critically assessed. An analysis of the resolving power of the method of ultrasonic angiography in pathological formations of major vessels of the neck is given.  相似文献   
999.
1000.
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