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   1602164篇
  免费   131526篇
  国内免费   2583篇
耳鼻咽喉   21648篇
儿科学   52931篇
妇产科学   46227篇
基础医学   227850篇
口腔科学   47225篇
临床医学   140930篇
内科学   314826篇
皮肤病学   34096篇
神经病学   130281篇
特种医学   64733篇
外国民族医学   474篇
外科学   243820篇
综合类   39715篇
现状与发展   3篇
一般理论   544篇
预防医学   122884篇
眼科学   36515篇
药学   121301篇
  3篇
中国医学   2974篇
肿瘤学   87293篇
  2018年   14768篇
  2016年   12915篇
  2015年   15036篇
  2014年   20658篇
  2013年   31367篇
  2012年   42576篇
  2011年   44774篇
  2010年   26345篇
  2009年   25330篇
  2008年   43026篇
  2007年   45272篇
  2006年   46073篇
  2005年   44696篇
  2004年   44114篇
  2003年   42198篇
  2002年   41316篇
  2001年   75698篇
  2000年   78344篇
  1999年   66394篇
  1998年   17732篇
  1997年   16338篇
  1996年   16320篇
  1995年   16022篇
  1994年   15075篇
  1993年   14218篇
  1992年   55431篇
  1991年   53779篇
  1990年   52572篇
  1989年   50835篇
  1988年   47227篇
  1987年   46566篇
  1986年   44290篇
  1985年   42850篇
  1984年   32038篇
  1983年   27568篇
  1982年   16147篇
  1981年   14441篇
  1980年   13568篇
  1979年   30465篇
  1978年   21066篇
  1977年   17767篇
  1976年   16696篇
  1975年   17575篇
  1974年   21491篇
  1973年   20673篇
  1972年   18858篇
  1971年   17774篇
  1970年   16290篇
  1969年   15271篇
  1968年   13952篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Fetal B lymphocytes in mice and humans use a limited number of the available VH gene segments. Mouse fetal B cells primarily utilize 3' VH elements, suggesting that the localization of these elements determines their rearrangement frequency. The previously reported non-random usage of human VH genes has been more difficult to explain. In this study the authors analysed the expression of the most proximal 3' human VH element (VH6) using a monoclonal antibody (JE-6). VH6 expression was assessed in various B cell differentiation stages from fetal liver, bone marrow and spleen at 12–20 weeks of gestation. The authors demonstrate that the level of VH6 expression does not exceed a stochastic usage frequency. This suggests that the localization of VH6 does not significantly promote its expression during human fetal life, and that other factors must affect the usage of VH genes during human fetal development.  相似文献   
112.
113.
Three hundred and twenty samples of subgingival plaque were obtained from 80 caucasian girls, ranging from 10 to 13 years of age. The samples were analyzed to verify the influence of age upon colonization of the gingival sulcus by microorganisms potentially pathogenic to the periodontal tissues. The gingival and plaque status were evaluated through the gingival index (GI) and plaque index (PlI) and the microflora was assessed by the enzymatic method benzoyl-arginine-naphthylamide (BANA). The results of the BANA test were positive for 62.50% of the tested individuals and 40% of the examined sites. The influence of age was statistically significant on BANA reactivity, and the number of positive sites was greater at 11 (57.5%) than at 12 years (28.8%).  相似文献   
114.
115.
116.
117.
This study examined electromyogram (EMG) and skin conductance level (SCL) as mediators of neuropsychological test performance of alcoholics. Alcoholics and controls with high EMG performed less well than low EMG subjects on 12 measures of neuropsychological performance. For SCL, the alcoholics and controls in the Low Group did not differ from those in the High Group on any measure. Analyses that used information intake (Low EMG and High SCL) and rejection (High EMG and Low SCL) information postures (IPs) demonstrated that the intake group outperformed the rejection group on 10 neuropsychological measures. Subjects with intake IPs reported more stimulation, concentration, and interest during the tasks than did subjects with rejection IPs. Results suggest that IPs can be used to identify alcoholics with neuropsychological deficits.  相似文献   
118.
We tested the urine of 30 infants 6 weeks to 7 months of age after they received standard 10-micrograms (0.5-ml) doses of HbOC (HibTITER) Haemophilus influenzae b (Hib) conjugate vaccine for the presence of Hib antigenuria using a commercially available latex particle agglutination assay (Directigen). Urines were collected within 1 hour, from 1 to 3 hours, at 24 hours and at 3, 6 and 9 days after vaccine administration and reactions were quantitated from 0 to 3+. In contrast to previous studies in older children which showed little or no antigenuria following HbOC vaccination, our study shows that in infants intense Hib antigenuria is evident within 2 to 3 hours and persists 3 days after vaccine administration and that less intense antigenuria may be detected in some infants for several days. With efficacious vaccines now being used in 2- to 6-month-old infants, invasive Hib disease may soon be limited to infants of this age just before their seroconversion. It should be recognized that antigenuria occurs for several days after vaccination with Hib conjugate vaccines and that it could be erroneously interpreted as evidence of invasive Hib infection.  相似文献   
119.
Analysis of accident logs in child day care centers indicates that biting is common, especially among toddlers 13 to 30 months of age. Children of this age often lack appropriate verbal skills and resort to aggressive means to achieve their goals. Still awkward in gross-motor skills, toddlers can also suffer self-bites following accidental falls. According to medical reports, human bites sometimes are more virulent than animal bites and can cause severe trauma. Although the AIDS virus has been cultured from saliva, transmission from saliva alone has not been documented. Bite injuries in day care, however, usually are minor and can be treated by washing, applying cold compresses, and comforting the child. Suggested methods to diminish the frequency of biting in day care include physical changes within the room, behavior modification, and other classroom management techniques.  相似文献   
120.
Lipid metabolism and hyperandrogenism.   总被引:1,自引:0,他引:1  
Hyperandrogenism and lipid metabolism were shown to be related intimately. Any discussion of the nature of their relationship must include other clinical and metabolic variables such as hyperinsulinemia and UBO. Despite the many correlations among each of these factors, the appropriate sequence in the pathogenesis of these conditions has not been defined. Do conditions that result in insulin resistance (e.g., genetic defects, insulin receptor antibodies, and obesity) also lead to the development of hyperandrogenemia by direct or indirect ovarian stimulation by insulin? Does hyperandrogenism of ovarian or adrenal origin cause abnormal upper body fat distribution, in turn leading to lipid abnormalities and insulin resistance? Regardless of the issue of mechanism of causality, women with hyperandrogenism are thought to be at greater risk for cardiovascular morbidity and mortality than their normoandrogenic counterparts. These women often are obese, hypertensive, and sedentary; ingest diets high in saturated fats; and have glucose intolerance and/or insulin resistance. All these abnormalities are well known independent risk factors for the development of lipid abnormalities and cardiovascular disease. Whether hyperandrogenism is a secondary consequence of any of these or whether it is an independent contributor to lipid aberrations requires future study. Treatment strategies for hyperandrogenic women, however, should not only be directed toward alleviation of the cosmetic problem of hirsutism but also toward the prevention and treatment of cardiovascular morbidity using modalities aimed at eradicating hyperinsulinemia, hypertension, and dyslipidemia. These modalities should include modifications in diet, exercise, and weight in addition to pharmacologic and/or surgical manipulation. Weight reduction will reduce many cardiovascular risk factors. Obesity is easier to target because of the many risk factors that result in it.(ABSTRACT TRUNCATED AT 250 WORDS)  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