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   1100912篇
  免费   67250篇
  国内免费   1342篇
耳鼻咽喉   14072篇
儿科学   30784篇
妇产科学   26157篇
基础医学   148758篇
口腔科学   29768篇
临床医学   92394篇
内科学   212927篇
皮肤病学   19884篇
神经病学   88003篇
特种医学   45388篇
外国民族医学   79篇
外科学   179835篇
综合类   20315篇
现状与发展   1篇
一般理论   234篇
预防医学   79097篇
眼科学   24005篇
药学   81677篇
  3篇
中国医学   2786篇
肿瘤学   73337篇
  2018年   30064篇
  2017年   23695篇
  2016年   26571篇
  2015年   9734篇
  2014年   12735篇
  2013年   18214篇
  2012年   30764篇
  2011年   45281篇
  2010年   32891篇
  2009年   25402篇
  2008年   43352篇
  2007年   46623篇
  2006年   26955篇
  2005年   27487篇
  2004年   27808篇
  2003年   27806篇
  2002年   25520篇
  2001年   55001篇
  2000年   56942篇
  1999年   47121篇
  1998年   10932篇
  1997年   9659篇
  1996年   9669篇
  1995年   9028篇
  1994年   8374篇
  1993年   7652篇
  1992年   35518篇
  1991年   34005篇
  1990年   32857篇
  1989年   31952篇
  1988年   29042篇
  1987年   28293篇
  1986年   26313篇
  1985年   25180篇
  1984年   17866篇
  1983年   15166篇
  1982年   7822篇
  1981年   6780篇
  1979年   15812篇
  1978年   10618篇
  1977年   9062篇
  1976年   7888篇
  1975年   8650篇
  1974年   10504篇
  1973年   9878篇
  1972年   9374篇
  1971年   8865篇
  1970年   8460篇
  1969年   7964篇
  1968年   7236篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
The VanA ligase encoded by the vancomycin resistance plasmid pIP816 of Enterococcus faecium BM4147 condenses D-alanine with various D-2-hydroxy and D-2-amino acids in vitro. D-Lactate added to the culture medium restored the vancomycin resistance of a strain that does not produce the VanH dehydrogenase and therefore appears to be a substrate of VanA in vivo.  相似文献   
942.
A modified enzyme immunoassay based on adsorption of antihepatitis A virus (HAV) IgG-HRPO conjugate and monoclonal antibodies to HAV were used to investigate antigenic differences between mature HAV virions and subviral particles with different buoyant densities in CsCl produced in HAV-infected cells. The mature virions (1.34 g/cm3) appeared to have common antigenic determinants with subviral particles (1.20, 1.27, and 1.30 g/cm3) and possess some additional determinants. Nevertheless, both subviral particles and mature virions induced antibodies capable of neutralizing HAV infectivity in tissue culture.  相似文献   
943.
944.
This study investigated the relationship between the development of diabetic retinopathy and pubertal status at onset of diabetes in 521 Type 1 diabetic patients diagnosed between 1950 and 1985. Pubertal status was based on age at onset (girls ≧ 11 years and boys ≧ 12 years). Retinopathy (all forms) developed in 112 patients (21.5%; 65 background and 47 proliferative retinopathy). For subjects diagnosed in either the prepubertal or postpuberal period, a similar proportion survived without developing retinopathy for any given duration of diabetes (X2 = 0.3822, p = 0.54). However, if only the postpubertal duration of diabetes is considered, then the proportion of patients surviving without retinopathy was significantly less for those diagnosed in the prepubertal period (X2 = 14.2, p = 0.002). This study suggests that the prepubertal duration of diabetes is an important phase and that the years prior to puberty do contribute to the risk of developing microvascular injury.  相似文献   
945.
The utilization of medical services by patients is an important determinant of doctor productivity, but this factor does not appear to have been given much attention in previous studies. In order to answer the question of why is there a wide variation in doctor output at low level medical facilities in China, an analytical framework of doctor productivity and utilization is developed. The simulation model is used to produce data that can be analyzed by such a framework. Great uncertainty about patient flows is one reason for the average lower and varying doctor productivity in lower level health facilities. Until uncertainty can be reduced, more flexibility is needed at the lower level to cope with changing utilization patterns and patient characteristics. The management by doctors of non-patient care activities (preventive programmes, medical research, teaching, and administration) is crucial to any approach to using doctor resources more effectively and efficiently.  相似文献   
946.
947.
Serum level of sex hormone-binding globulin (SHBG) was measured by immunoradiometric assay in fifty two breast cancer patients and twenty nine healthy female volunteers. The results are as follows: 1) Although the serum SHBG concentration showed no significant difference between the breast cancer group and the healthy control group, the serum SHBG concentration in postmenopause was significantly higher in the breast cancer group (63.8 +/- 31.2nmol/ml/ml; mean +/- S.D.) than in the healthy control group (40.1 +/- 15.4nmol/ml). 2) Subsequently in the postmenopausal breast cancer group, the serum SHBG concentration was significantly higher in the estrogen receptor (ER)-negative cancer group (97.8 +/- 12.7nmol/ml) than in the ER-positive cancer group (55.8 +/- 32.1nol/ml). 3) No significant relationships were showed between the serum SHBG concentration and obesity or serum estradiol concentration in postmenopausal patients. 4) The serum SHBG concentration showed significant decrease 3 months after radical operation for breast cancer in postmenopausal patients. These results suggest the possibility of the SHBG synthesis in breast cancer tissue.  相似文献   
948.
Transrectal ultrasonotomography is useful in following patients with benign prostatic hypertrophy, because prostatic shape and weight are precisely assumed. We studied the effect of chlormadinone acetate (CMA) on benign prostatic hypertrophy. CMA (50 mg/day) was administered to 30 patients with benign prostatic hypertrophy. Weight reduction over 10% of the gland was noticed in 24 cases (80%). Mictional conditions were improved in 70% subjectively and in 71.4% objectively. However, the number of nocturia decreased in only 18.9%. Reduction rate of the weight was unrelated with the weight of prostate before administration of CMA. Duration of administration of CMA and the reduction rate were estimated. There was no definite difference in reduction rate for the first 15 months, but there was a slightly high reduction rate after administration of CMA for more than 24 months. In 3 cases, the shape and weight of prostate were studied after discontinuation of CMA. The size of prostate showed a tendency to increase gradually.  相似文献   
949.
O-beta-D-Galactopyranosyl-(1----4)-O-beta-D-galactopyranosyl-(1----4)-D- glucopyranose (designated as 4'GL) is produced from lactose by Cryptococcus laurentii. The influence of chronic ingestion of 4'GL on body weight gain, organ weight, serum lipids, and liver lipids was investigated in rats. The body weight gains of the 5% and 10% 4'GL-diet groups were higher than that of the control group. Food intake and fecal dry weight were significantly increased (p less than 0.05) by 4'GL feeding. The 4'GL diet produced a significant increase (p less than 0.01) in the wet weight and contents of both the cecum and the colon. However, no significant increase was observed in the weight of the stomach, small intestine, liver, or other organs. The effects of 4'GL on serum and liver lipid levels were not observed in this experiment. The digestion of 4'GL was measured in vitro using the artificial gastric juice, alpha-amylase of human saliva, alpha-amylase of hog pancreas, and mucosa of rat intestine. 4'GL was not hydrolyzed by these enzymes. Long-term ingestion of 4'GL did not cause any induction of 4'GL hydrolyzing enzyme activity in the rat small intestine.  相似文献   
950.
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