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   1275505篇
  免费   94212篇
  国内免费   1991篇
耳鼻咽喉   18185篇
儿科学   42266篇
妇产科学   37813篇
基础医学   187018篇
口腔科学   35382篇
临床医学   108161篇
内科学   251474篇
皮肤病学   26515篇
神经病学   99229篇
特种医学   49994篇
外国民族医学   366篇
外科学   197762篇
综合类   26516篇
现状与发展   1篇
一般理论   300篇
预防医学   92597篇
眼科学   29057篇
药学   97776篇
  1篇
中国医学   2496篇
肿瘤学   68799篇
  2018年   11819篇
  2015年   11629篇
  2014年   16011篇
  2013年   24356篇
  2012年   33570篇
  2011年   35963篇
  2010年   21226篇
  2009年   20026篇
  2008年   34998篇
  2007年   37962篇
  2006年   38518篇
  2005年   37799篇
  2004年   36391篇
  2003年   35371篇
  2002年   34921篇
  2001年   58102篇
  2000年   59598篇
  1999年   50698篇
  1998年   14236篇
  1997年   12810篇
  1996年   13072篇
  1995年   12346篇
  1994年   11758篇
  1993年   10861篇
  1992年   40987篇
  1991年   40360篇
  1990年   39889篇
  1989年   38709篇
  1988年   36109篇
  1987年   35354篇
  1986年   33727篇
  1985年   32136篇
  1984年   23927篇
  1983年   20823篇
  1982年   12377篇
  1981年   10929篇
  1980年   10208篇
  1979年   22642篇
  1978年   15879篇
  1977年   13735篇
  1976年   12982篇
  1975年   14205篇
  1974年   16688篇
  1973年   16080篇
  1972年   15319篇
  1971年   14229篇
  1970年   13218篇
  1969年   12734篇
  1968年   11981篇
  1967年   10479篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
The spread of Brucella infection in man in Italy during the last three years is briefly reviewed with reference to the Brucella strains collected and typed.The strains were tested by H2S production, dye-inhibition, agglutination by monospecific sera, and sensitivity to a phage set. From 108 tested strains, 91 have been identified by means of the traditional tests as Br. melitensis, sometimes with some irregularities, 10 as Br. abortus, while 7 were not typable.It was possible to recommend some phage sensitivity patterns of Br. melitensis for epidemiological purposes: one phagotype is much more frequent in the north, another in the south of Italy.However, the currently recommended phagotypes must be considered provisional and will be modified in the light of more extensive studies.Corresponding author.  相似文献   
995.
Atomic absorption spectrometry and x-ray fluorescence have been used to determine the lead content of metatarsal and tibia bone samples. For a range of bone lead levels from 6.5 to 83 micrograms g-1 of ashed bone there is no evidence of a systematic difference between the two techniques of more than 1 microgram g-1. There is, however, some evidence that random differences between the two in vitro analyses applied to the same bone sample are larger than can be accounted for by known measurement uncertainties. Variations in bone composition could account for these differences. Because the x-ray fluorescence technique is applied in an identical way to in vivo analysis, it is concluded that the uncertainties in in vivo measurements are small.  相似文献   
996.
An industrial hygiene and medical survey was conducted in an iron foundry to study the occurrence of silicosis. Breathing zone exposures to respirable crystalline silica had been very high in 1977 [1 045 micrograms/m3 (geometric mean) for coremakers and 198 micrograms/m3 for fettlers]; exposures in 1980 and 1982 were substantially lower. A radiographic evaluation of 188 workers revealed silicosis in 18 (9.6%). Eight had category 1 profusion of small rounded pulmonary lesions (by the 1980 classification of the International Labour Office); two had category 2; and eight had category 3. Two had progressive massive fibrosis. Four workers without silicosis in 1977 had developed lesions by 1980. The prevalence increased from 1.5% among workers employed less than 20 years to 53% among longer term workers. No association was found between the prevalence of silicosis and cigarette smoking. Chronic cough was more common in workers with heavy current dust exposure than in those with light exposure, more common in smokers than in nonsmokers, and more common in silicotics than in nonsilicotics. A multiplicative interaction existed between dust exposure and smoking in the etiology of cough. Silicosis continues to exist in American foundries. Cigarette smoking does not contribute to the causation of silicosis, but it aggravates the attendant respiratory symptoms.  相似文献   
997.
998.
A prospective study was performed on seven male and eight female patients with normal hepatobiliary findings to investigate the effect of 20 mg nifedipine on cholecystokinin-induced gallbladder contraction. Each patient received 1 IDU (Ivy dog unit) cholecystokinin per kg body weight intravenously on two consecutive days, with additional administration of 20 mg nifedipine sublingually on the second day. Gallbladder volumes were assessed by ultrasonography over a period of 25 minutes. Cholecystokinin induced a maximal reduction in the mean initial volume of 56.8 +/- 3.6%. After nifedipine, this volume change was significantly reduced to 30.9 +/- 5.1% (p less than 0.001). Thus our data suggest for the first time that the calcium-channel-blocking agent nifedipine can have an effect on human gallbladder kinetics.  相似文献   
999.
We compared two groups of patients with idiopathic epilepsy, 41 patients whose seizure frequency was not controlled by adequate therapy and 39 patients in good seizure control, in respect of hematology, kidney and liver function tests, serum IgG, IgA and IgM concentrations and drug concentrations. The only difference that emerged were in the serum immunoglobulins, which were raised in the drug refractory group, significantly (p less than 0.01) so in the case of IgG. Failure of seizure control did not depend on inadequacy of drug dose or of blood concentration. Although the serum Ig changes do not warrant the assumption of an immunological origin for drug resistance, they do suggest a useful research line.  相似文献   
1000.
Electrocardiograms were evaluated in 39 children and adolescents before and after the clinical use of imipramine and desipramine. The average increase in PR interval was 0.01 seconds. The PR interval increased by 0.02 seconds in 11 subjects, and a new first-degree atrioventricular block developed in two subjects. These changes were not related to the choice between imipramine and desipramine, the dose, or the method of administration. An increase in PR interval by 0.02 seconds or more did correlate with having an abnormality disclosed on a pretreatment electrocardiogram. The average increase in PR interval was 0.007 seconds for subjects with normal baseline electrocardiograms and 0.019 seconds for subjects with conduction and nonconduction abnormalities disclosed in baseline tracings. None of the electrocardiogram changes resulted in adverse clinical consequences.  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