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   1276615篇
  免费   92933篇
  国内免费   1991篇
耳鼻咽喉   18198篇
儿科学   42262篇
妇产科学   37812篇
基础医学   187004篇
口腔科学   35382篇
临床医学   108128篇
内科学   251545篇
皮肤病学   26502篇
神经病学   99190篇
特种医学   49993篇
外国民族医学   366篇
外科学   197602篇
综合类   26519篇
现状与发展   1篇
一般理论   300篇
预防医学   92596篇
眼科学   29063篇
药学   97781篇
  1篇
中国医学   2497篇
肿瘤学   68797篇
  2018年   11811篇
  2015年   11610篇
  2014年   15995篇
  2013年   24346篇
  2012年   33545篇
  2011年   35940篇
  2010年   21207篇
  2009年   20015篇
  2008年   34975篇
  2007年   37944篇
  2006年   38499篇
  2005年   37795篇
  2004年   36379篇
  2003年   35368篇
  2002年   34916篇
  2001年   58094篇
  2000年   59585篇
  1999年   50687篇
  1998年   14232篇
  1997年   12810篇
  1996年   13071篇
  1995年   12345篇
  1994年   11757篇
  1993年   10860篇
  1992年   40984篇
  1991年   40360篇
  1990年   39885篇
  1989年   38706篇
  1988年   36109篇
  1987年   35349篇
  1986年   33723篇
  1985年   32134篇
  1984年   23922篇
  1983年   20818篇
  1982年   12377篇
  1981年   10927篇
  1980年   10204篇
  1979年   22635篇
  1978年   15877篇
  1977年   13729篇
  1976年   12970篇
  1975年   14201篇
  1974年   16683篇
  1973年   16076篇
  1972年   15320篇
  1971年   14229篇
  1970年   13214篇
  1969年   12731篇
  1968年   11978篇
  1967年   10478篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The interaction of trolox with ammonia, alkylamines of different classes, and amino derivatives of heterocyclic compounds, including nitroxyl radicals and alkaloids, led to the production of ammonium salts called ion conjugates (ICs). Five ICs were characterised by X-ray diffraction. This is the first time a wide range of ICs were made from trolox with amines, and ESI-MS data demonstrated they have the potential to generate pseudomolecular [(A?B+)?+?H]+ ions. For all obtained trolox ICs, a significant increase (1–3 orders of magnitude) in water solubility was achieved while retaining high antioxidant activity. ICs synthesised from two biologically active fragments may be used to create polyfunctional agents with varying solubility and bioavailability.  相似文献   
83.
Extracellular vesicles (EV) are secreted signaling entities that enhance various pathological processes when released in response to cellular stresses. Respiratory exposures such as cigarette smoke and air pollution exert cellular stresses and are associated with an increased risk of several chronic diseases. The aim of this review was to examine the evidence that modifications in EV contribute to respiratory exposure-associated diseases. Publications were searched using PubMed and Google Scholar with the search terms (cigarette smoke OR tobacco smoke OR air pollution OR particulate matter) AND (extracellular vesicles OR exosomes OR microvesicles OR microparticles OR ectosomes). All original research articles were included and reviewed. Fifty articles were identified, most of which investigated the effect of respiratory exposures on EV release in vitro (25) and/or on circulating EV in human plasma (24). The majority of studies based their main observations on the relatively insensitive scatter-based flow cytometry of EV (29). EV induced by respiratory exposures were found to modulate inflammation (19), thrombosis (13), endothelial dysfunction (11), tissue remodeling (6), and angiogenesis (3). By influencing these processes, EV may play a key role in the development of cardiovascular diseases and chronic obstructive pulmonary disease and possibly lung cancer and allergic asthma. The current findings warrant additional research with improved methodologies to evaluate the contribution of respiratory exposure-induced EV to disease etiology, as well as their potential as biomarkers of exposure or risk and as novel targets for preventive or therapeutic strategies.  相似文献   
84.
Background: The perioperative use of immunomodulatory nutrition formulas in patients with head and neck cancer reduces the number of postoperative infections and the length of hospital stay. Objective: An exploratory, randomized, controlled, blind, clinical trial was designed to examine the effect of the preoperative consumption of a new, immunomodulatory, oral nutrition formula in patients with head and neck cancer. Methods: Thirty‐eight patients were randomized to receive either 400 mL/d of either the new immunomodulatory formula (IF) or that commonly used in clinical practice (CF) over 10 days prior to surgery. Thirty‐three patients completed the study. Compliance, tolerance, the length of hospital stay, the incidence of infections and noninfectious complications before discharge, and the same up to 15 and 30 days after discharge were recorded. Results: The percentage of patients who developed infections before discharge was significantly lower in the IF than in the CF group (P = .013), as was the number of infections/100 patients/d (P = .035). The length of hospital stay was significantly shorter in the IF group (P = .001). Both formulas were safe and well tolerated. No other differences were detected. These results suggest preoperative consumption of the new formula to be beneficial for patients with neck and head cancer. Further trials are needed to confirm these results and to test the efficacy of the formula in patients with other conditions. Conclusion: The new formula can be safely prescribed as part of the preoperative treatment of patients with head and neck cancer and might reduce the problem of postoperative infection.  相似文献   
85.
Historically, no black fly (Diptera: Simuliidae) nuisance has been reported in the Murcia Region. Back in September 2016 the Ojós City Council has contacted the Regional Public Health General Directorate for help regarding a local insect nuisance, most probably based on mosquitoes. After sampling with a BG-sentinel 2 trap, collecting adult specimens with an entomological aspirator, and collect larvae and pupae on submerged giant cane stalks at the river, it turned out that Simulium sergenti was the insect species causing the nuisance. This species is not considered particularly anthropophilic; therefore, a low vector risk for human health was considered. However, the high fly density impaired the life quality of the people at the village. A management plan was recommended, treating the river with Bacillus thuringiensis var israelensis.  相似文献   
86.
87.
88.
89.
90.
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