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   68414篇
  免费   5836篇
  国内免费   148篇
耳鼻咽喉   602篇
儿科学   2640篇
妇产科学   1791篇
基础医学   9521篇
口腔科学   1347篇
临床医学   9009篇
内科学   13298篇
皮肤病学   1185篇
神经病学   6546篇
特种医学   1946篇
外国民族医学   1篇
外科学   6920篇
综合类   925篇
一般理论   73篇
预防医学   7965篇
眼科学   1510篇
药学   4112篇
  2篇
中国医学   73篇
肿瘤学   4932篇
  2023年   496篇
  2022年   524篇
  2021年   1637篇
  2020年   1149篇
  2019年   1771篇
  2018年   1967篇
  2017年   1531篇
  2016年   1674篇
  2015年   1828篇
  2014年   2355篇
  2013年   3415篇
  2012年   4826篇
  2011年   4961篇
  2010年   2721篇
  2009年   2482篇
  2008年   4155篇
  2007年   4284篇
  2006年   4197篇
  2005年   3938篇
  2004年   3869篇
  2003年   3558篇
  2002年   3272篇
  2001年   904篇
  2000年   831篇
  1999年   819篇
  1998年   760篇
  1997年   615篇
  1996年   533篇
  1995年   545篇
  1994年   459篇
  1993年   457篇
  1992年   582篇
  1991年   572篇
  1990年   533篇
  1989年   491篇
  1988年   451篇
  1987年   405篇
  1986年   418篇
  1985年   408篇
  1984年   341篇
  1983年   293篇
  1982年   281篇
  1981年   254篇
  1980年   236篇
  1979年   239篇
  1978年   207篇
  1977年   188篇
  1976年   161篇
  1974年   168篇
  1973年   170篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Postpartum fatigue is a normal condition that most women experience. Breastfeeding is often associated in women's minds as contributing to the feeling of overall perceived fatigue, and many women indicate that they have ceased breastfeeding because of fatigue. However, the relationship between feeding choice and perceived fatigue has never been established. Two hundred and fifty-three women participated in a study examining whether perceived fatigue differed for bottle-feeding and breastfeeding women at 3 different times during the postpartum period (2-4 days, 6 weeks, and 12 weeks postpartum). Results showed no significant differences for these 2 groups, suggesting that perceived fatigue during the postpartum period is not dependent on feeding choice. Additional analyses examining other variables with a potential effect were nonsignificant. Because perceived physical fatigue does not appear to be dependent on feeding choice, women should be prepared for the feeling of perceived fatigue during the postpartum period while at the same time be reassured that feeding choice is not correlated.  相似文献   
52.
BACKGROUND & AIMS: Many patients with chronic hepatitis C virus (HCV) have persistently normal serum alanine transaminase (ALT) levels. We compared characteristics of chronic hepatitis C patients with patients with normal and elevated ALT levels using data from 3 randomized phase III trials of peginterferon alfa-2a (40 kDa). METHODS: The characteristics of 480 patients with normal ALT values (on >or=3 occasions without any increases in ALT level over a 6- to 18-month period) and 1993 patients with elevated ALT levels were compared. Sixty-eight of the 480 patients with normal ALT levels were randomized to no treatment and monitored for 72 weeks. RESULTS: More patients with normal ALT levels than patients with elevated ALT levels were women (59% vs 32%; P<.01). The serum HCV RNA titer was significantly lower in patients with normal ALT levels (P<.01 vs in patients with elevated ALT levels). Patients with normal ALT levels had significantly lower inflammation and fibrosis scores on liver biopsy examination than patients with elevated ALT levels, but almost two-thirds had portal fibrosis and 10% had bridging fibrosis. No correlation between baseline ALT activity, HCV RNA level, and liver histology was observed in patients with normal ALT levels. During the 72-week follow-up period, ALT activity elevated above the upper limit of normal in 53% of the untreated patients with normal levels of ALT. None became HCV RNA undetectable. CONCLUSIONS: Chronic hepatitis C patients with normal ALT levels should be evaluated in a similar manner as patients with elevated ALT levels because they are at risk for developing significant liver disease. The decision to treat with peginterferon alfa and ribavirin should be based on multiple factors, rather than on ALT levels alone.  相似文献   
53.
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   
54.
55.
This paper presents a case for careful consideration of theory in planning to implement evidence-based practices into clinical care. As described, theory should be tightly linked to strategic planning through careful choice or creation of an implementation framework. Strategies should be linked to specific interventions and/or intervention components to be implemented, and the choice of tools should match the interventions and overall strategy, linking back to the original theory and framework. The thesis advanced is that in most studies where there is an attempt to implement planned change in clinical processes, theory is used loosely. An example of linking theory to intervention design is presented from a Mental Health Quality Enhancement Research Initiative effort to increase appropriate use of antipsychotic medication among patients with schizophrenia in the Veterans Health Administration.  相似文献   
56.
Intraoperative MRI has recently entered the operating room as a new imaging modality. Customized visualization systems might further facilitate the use of this imaging technology. A visualization system for use in the interventional MRI has been developed, providing a virtual environment for surgical navigation using real-time images and for controlling the scanner. The visualization system has customized features for certain clinical applications. A training and testing facility has also been established. The introduction of the visualization system in the interventional MRI overcame several ambiguities and inconsistencies that were previously present, and resulted in a more transparent man-machine interface approach. A pilot study using the software to place cryoprobes in an animal liver showed promising results. Augmentation of real-time MR images with 3D rendering and customized navigation features opens new possibilities in intraoperative MRI. The described system can also be extended to other intraoperative imaging modalities.  相似文献   
57.
A case illustrating the potentially fatal complication of endogenous Gram Negative Aerobic Bacillus (GNAB) septicaemia secondary to nosocomial pneumonia is presented along with current theories as to its aetiology. The technique of selective decontamination of the digestive tract is designed and advocated to prevent such occurrences; oral and maxillofacial surgeons should be aware of this approach. It may be, however, that by using much simpler manoeuvres such as changes in policy regarding gastric stress ulcer prophylaxis, the already small risk of such an occurrence will be further reduced. Awareness of this condition will allow a higher index of suspicion when presented with catastrophic septic complications on the ITU and aid in more rational planning of antimicrobial therapy.  相似文献   
58.
59.
60.
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