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   1973608篇
  免费   147681篇
  国内免费   3550篇
耳鼻咽喉   29005篇
儿科学   62524篇
妇产科学   58136篇
基础医学   286771篇
口腔科学   56572篇
临床医学   170130篇
内科学   380746篇
皮肤病学   40421篇
神经病学   156113篇
特种医学   77616篇
外国民族医学   524篇
外科学   306540篇
综合类   47121篇
现状与发展   3篇
一般理论   539篇
预防医学   148738篇
眼科学   46258篇
药学   149857篇
  1篇
中国医学   3769篇
肿瘤学   103455篇
  2018年   17884篇
  2015年   17960篇
  2014年   25150篇
  2013年   38462篇
  2012年   52464篇
  2011年   55846篇
  2010年   32795篇
  2009年   30915篇
  2008年   53681篇
  2007年   58351篇
  2006年   58607篇
  2005年   57793篇
  2004年   55952篇
  2003年   54153篇
  2002年   52864篇
  2001年   85015篇
  2000年   87249篇
  1999年   74213篇
  1998年   21742篇
  1997年   19694篇
  1996年   19748篇
  1995年   18673篇
  1994年   17787篇
  1993年   16513篇
  1992年   61359篇
  1991年   60425篇
  1990年   59473篇
  1989年   57738篇
  1988年   53883篇
  1987年   52986篇
  1986年   50593篇
  1985年   48550篇
  1984年   36886篇
  1983年   31919篇
  1982年   19501篇
  1981年   17573篇
  1980年   16355篇
  1979年   35979篇
  1978年   25605篇
  1977年   21828篇
  1976年   20468篇
  1975年   22315篇
  1974年   26931篇
  1973年   26024篇
  1972年   24711篇
  1971年   22920篇
  1970年   21607篇
  1969年   20878篇
  1968年   19351篇
  1967年   17354篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
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   
993.
Smoking behavior among participants in the nurses' health study.   总被引:2,自引:1,他引:1       下载免费PDF全文
We analyzed smoking behavior of 91,651 married female nurses, aged 30-55 years in 1976. The prevalence of smoking was similar among all birth cohorts. The largest percentage increase in starting to smoke occurred between ages 15 and 25 years; by age 25, 50 per cent had started smoking. The cessation rate was lowest in earlier birth cohorts and among nurses starting to smoke at earlier ages. The cessation rate increased substantially between 1963-73 compared with the period 1948-58.  相似文献   
994.
995.
996.
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   
997.
The effects of danazol on calcium homeostasis in normal postmenopausal women was examined in a 14-day study utilizing a dosage of 800 mg per day. Danazol caused significant falls in plasma ionized calcium and in the fasting urinary calcium/creatinine ratio, indicating inhibition of bone resorption. Retention of phosphate was also observed as expected with this anabolic agent. The plasma total alkaline phosphatase was also depressed by the drug, which had no effect on hepatocellular function as measured by plasma AST. Certain effects induced by treatment with danazol were still apparent two weeks after cessation of treatment. The drug was well tolerated and androgenic side effects were not seen. It is suggested that the minimal dose regimen of danazol which exerts a calcium-sharing effect should be identified, and that this regimen should be considered for use in a prospective study of the effects of danazol on bone mineral content in the postmenopause.  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