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   281419篇
  免费   21023篇
  国内免费   976篇
耳鼻咽喉   3095篇
儿科学   7387篇
妇产科学   5300篇
基础医学   36936篇
口腔科学   5305篇
临床医学   27612篇
内科学   59898篇
皮肤病学   3716篇
神经病学   27206篇
特种医学   9755篇
外国民族医学   13篇
外科学   44459篇
综合类   4211篇
现状与发展   2篇
一般理论   378篇
预防医学   24474篇
眼科学   6184篇
药学   19282篇
  1篇
中国医学   456篇
肿瘤学   17748篇
  2023年   1304篇
  2022年   2006篇
  2021年   5628篇
  2020年   3341篇
  2019年   5391篇
  2018年   6283篇
  2017年   4845篇
  2016年   5147篇
  2015年   6073篇
  2014年   8991篇
  2013年   12543篇
  2012年   18987篇
  2011年   20396篇
  2010年   11441篇
  2009年   10240篇
  2008年   18450篇
  2007年   19427篇
  2006年   18555篇
  2005年   18970篇
  2004年   17981篇
  2003年   16695篇
  2002年   15863篇
  2001年   2449篇
  2000年   1835篇
  1999年   2568篇
  1998年   3551篇
  1997年   2959篇
  1996年   2639篇
  1995年   2337篇
  1994年   2117篇
  1993年   2017篇
  1992年   1446篇
  1991年   1334篇
  1990年   1228篇
  1989年   1105篇
  1988年   1174篇
  1987年   1141篇
  1986年   1125篇
  1985年   1227篇
  1984年   1648篇
  1983年   1598篇
  1982年   2032篇
  1981年   1850篇
  1980年   1711篇
  1979年   914篇
  1978年   1070篇
  1977年   1031篇
  1976年   897篇
  1975年   736篇
  1974年   711篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
Hepatitis C virus (HCV)-specific impairments in host immunity have been described at multiple levels of the innate and adaptive response, which may lead to viral persistence in the majority of infections. Understanding of HCV-associated immune defects could lead to novel therapeutic advances. Natural killer (NK) cells, the major effector cells of the innate immune system, are functionally impaired in chronic HCV infection. It has been suggested that this phenotype is a result of virus-specific defects in antigen-presenting cells (APCs) that regulate NK cell activity, as normal NK function is restored when they are stimulated ex vivo. In this study, we used human NK cell cytotoxicity assays to evaluate the activation-induced effects of NK cells on the HCV replicon-containing hepatic cells. We found that cytokine-activated NK cells were capable of inducing an HCV-associated, perforin/granzyme-dependent lysis of human hepatoma cells and that this required direct cellular contact and was independent of MHC class I expression levels. In contrast, on removal of cytokine stimulation, NK cells failed to exert any direct cytolytic effect on replicon targets. These findings suggest an important underlying mechanism by which NK cells control HCV infection and, with appropriate understanding of HCV-associated immune defects, could lead to novel therapeutic advances.  相似文献   
142.
Vascular malformation (AVM) in the gastrointestinal tract is an uncommon, but not rare, cause of bleeding and iron deficiency anemia, especially in an aging population. While endoscopic coagulative therapy is the method of choice for controlling bleeding, a substantial number of cases require additional therapy. Adjunctive or even primary phamacotherapy may be indicated in recurrent bleeding. However, there is little evidence-based proof of efficacy for any agent. The bulk of support is derived from anecdotal reports or case series. The present review compares the outcome of AVM after no intervention, coagulative therapy or focus on pharmacological agents. Most of the literature encompasses two common AVMs, angiodysplasia and hereditary hemorrhagic telangiectasia. Similarly, the bulk of information evaluates two therapies, hormones (estrogen and progesterone) and the somatostatin analogue octreotide. Of these, the former is the only therapy evaluated in randomized trials, and the results are conflicting without clear guidelines. The latter therapy has been reported only as case reports and case series without prospective trials. In addition, other anecdotally used medications are discussed.  相似文献   
143.
144.
145.
Abstract: Background: Identification of risk drinking in expectant fathers may be helpful as an important part of efforts to minimize maternal alcohol use, and as an opportunity to inform them about a problematic practice during a critical developmental stage for the couple. The purpose of this study was to evaluate the T‐ACE screening questionnaire, which asks about t olerance to alcohol, being a nnoyed by other's comments about drinking, attempts to c ut down, and having a drink first thing in the morning (“ e ye‐opener”), in the male partners of pregnant women who themselves were T‐ACE positive. Methods: Two hundred fifty‐four male partners were asked to complete the T‐ACE embedded in a health survey, the Alcohol Use Disorders Identification Test (AUDIT), and other questions about their alcohol use in the past 30 days when their pregnant partners had a median gestation of 11.5 weeks (T1). After delivery, male partners again completed the T‐ACE and quantity‐frequency questions (T2). The predictive ability of the T‐ACE and AUDIT was compared, using risk drinking (>4 drinks/day or >14 drinks/week) as the criterion standard. Results: A substantial minority of male partners had risk drinking, 31 percent at T1 and 25 percent at T2. Although the AUDIT was better than the T‐ACE as an independent predictor of risk drinking, the latter was most accurate when the tolerance threshold exceeded 2 drinks, the same established for pregnant women. The sensitivity (T1 = 84.6%, T2 = 82.8%) and specificity (T1 = 43.8%, T2 = 51.1%) of the T‐ACE at this threshold compared favorably with those of the AUDIT at the standard cut point of 8. Conclusions: The T‐ACE may be a practical way for clinicians to identify risk drinking in both pregnant women and expectant fathers. (BIRTH 33:2 June 2006)  相似文献   
146.
147.
The present study demonstrates that alcohol-induced memory impairment can be attenuated by pretreatment with an oral tryptophan supplementation. These results provide support for the role of a brain serotonin deficit in this impairment and highlight the impact a dietary manipulation can have on a complex behavioral process.  相似文献   
148.
Background.Computers that collect data from patients and provide both patients and practitioners with printed feedback on a range of health risks are a tool for assisting general practitioners with preventive care. This study assessed the impact of computer-generated printed feedback on cervical screening among women who were underscreened for cervical cancer.Method.Female attenders at two Australian general practices were randomly allocated to Experimental or Control groups. Women in both groups completed a health risk survey on a touch screen computer prior to their consultation. Those in the Experimental group received printed pages summarizing their results, including their eligibility for cervical screening and last Pap test, for themselves and their doctor. The number and proportion of underscreened women who had a Pap test in the 6 months after completing the computer survey, as determined by pathology records, were examined.Results.Of the 679 participants, 139 were classified as underscreened on the basis of self-report (74 Experimental, 65 Control) and 272 on the basis of their pathology records (148 Experimental, 124 Control). Overall about one-third of women had a test in the 6-month period, and the differences between the groups were not significant for women overall (18–70 years) or for women 18–49 years. Among women 50–70 who were underscreened based on self-report, those receiving the printout were more likely to have a Pap test in the next 6 months (P< 0.05). This pattern was also evident, but did not reach statistical significance, for older women who were underscreened based on pathology records.Conclusions.We are unable to draw conclusions regarding the effectiveness of the computer system due to the modest proportions of women screened, the small numbers, and the fact that the computer survey may have created an intervention effect in the Control group. As the study suggests the computer system is acceptable to women and may be effective for encouraging screening among older women, further exploration of the system is desirable.  相似文献   
149.
The effect of a newly developed patellar realignment brace was evaluated in 21 patellofemoral joints (19 patients) with patellar subluxation (13 joints with lateral subluxation and eight with medial subluxation) by using active-movement, loaded kinematic magnetic resonance (MR) imaging. Sixteen patellofemoral joints (76%) demonstrated a qualitative correction of or improvement in patellar subluxation (ie, centralization of the patella or a decrease in the displacement of the patella) after application of the brace. Four of the five “failures” occurred in patellofemoral joints that had patella alta and/or dysplastic bone anatomy. These results indicate that the patellar realignment brace was able to counteract patellar subluxation in the majority of patellofemoral joints studied, as shown by active-movement, loaded kinematic MR imaging. This brace appears to be useful for conservative treatment of patients with patellofemoral joint pain secondary to patellar malalignment and maltracking.  相似文献   
150.
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