首页 | 官方网站   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   12484篇
  免费   945篇
  国内免费   39篇
医药卫生   13468篇
  2024年   10篇
  2023年   139篇
  2022年   202篇
  2021年   573篇
  2020年   327篇
  2019年   487篇
  2018年   527篇
  2017年   369篇
  2016年   325篇
  2015年   369篇
  2014年   511篇
  2013年   739篇
  2012年   1046篇
  2011年   1055篇
  2010年   560篇
  2009年   497篇
  2008年   784篇
  2007年   832篇
  2006年   740篇
  2005年   692篇
  2004年   624篇
  2003年   583篇
  2002年   435篇
  2001年   81篇
  2000年   54篇
  1999年   82篇
  1998年   80篇
  1997年   61篇
  1996年   56篇
  1995年   58篇
  1994年   39篇
  1993年   45篇
  1992年   31篇
  1991年   30篇
  1990年   39篇
  1989年   30篇
  1988年   26篇
  1987年   26篇
  1986年   23篇
  1985年   26篇
  1984年   20篇
  1983年   26篇
  1982年   32篇
  1981年   19篇
  1980年   20篇
  1979年   13篇
  1978年   21篇
  1977年   13篇
  1973年   20篇
  1971年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Residential counselors are occasionally expected to be in contact with clients at risk for violent behavior. Client violence poses the obvious risk of physical harm, and there is evidence to suggest that it may have a potentially harmful psychological impact as well. As a result of the potential variability within training programs in didactic and clinical instruction, residential counselors may be neither adequately informed about the nature of violent behavior nor prepared for the potential effects of client violence. The purpose of this article is threefold: (a) To call attention to the potential crisis of client violence for counselors, (b) to propose a conceptual framework for counselor preparation and practice regarding client violence, and (e) to make recommendations for further research.  相似文献   
992.
993.
994.
Zalypsis® is a new synthetic alkaloid tetrahydroisoquinoline antibiotic that has a reactive carbinolamine group. This functionality can lead to the formation of a covalent bond with the amino group of selected guanines in the DNA double helix, both in the absence and in the presence of methylated cytosines. The resulting complex is additionally stabilized by the establishment of one or more hydrogen bonds with adjacent nucleotides in the opposite strand as well as by van der Waals interactions within the minor groove. Fluorescence-based thermal denaturation experiments demonstrated that the most favorable DNA triplets for covalent adduct formation are AGG, GGC, AGC, CGG and TGG, and these preferences could be rationalized on the basis of molecular modeling results. Zalypsis®-DNA adducts eventually give rise to double-strand breaks, triggering S-phase accumulation and apoptotic cell death. The potent cytotoxic activity of Zalypsis® was ascertained in a 24 cell line panel. The mean IC50 value was 7 nM and leukemia and stomach tumor cell lines were amongst the most sensitive. Zalypsis® administration in four murine xenograft models of human cancer demonstrates significant tumor growth inhibition that is highest in the Hs746t gastric cancer cell line with no weight loss of treated animals. Taken together, these results indicate that the potent antitumor activity of Zalypsis® supports its current development in the clinic as an anticancer agent.  相似文献   
995.
Respiratory health in the general population declines regardless of the presence of pulmonary diseases. Oxidative stress has been implicated as one of the mechanisms involved in respiratory dysfunction. This review was to evaluate studies that relate oxidative stress factors with pulmonary function among the general population without prior respiratory illnesses. The search yielded 54 citations. Twenty-one studies qualified for incorporation in this review. Owing to the heterogeneity of the review, studies were discussed based on identified oxidative stress factors responsible for pulmonary dysfunction. Oxidative stress biomarkers, including gene polymorphisms of nuclear factor erythroid 2-related factor 2, heme oxygenase 1, glutathione S transferase, superoxide dismutase, and lipid peroxidation products were involved in lung function decline. In addition, the antioxidant status of individuals in reference to dietary antioxidant intake and exposure to environmental pollutants affected oxidative stress and pulmonary function, as indicated by forced expired volume in one second, forced vital capacity, and forced expiratory flow at 25%–75%. This review indicated that oxidative stress is implicated in the gradual decline of lung function among the general population, and gene polymorphism along the antioxidant defense line and/or their interaction with air pollutants reduce lung function. Different polymorphic forms among individuals explain why the rate of lung function decline differs among people. Dietary antioxidants have respiratory health benefits in antioxidant gene polymorphic forms. Therefore, the genetic composition of an individual may be considered for monitoring and identifying people at risk of respiratory illnesses.  相似文献   
996.
997.
OBJECTIVE: To develop indices to quantitatively assess and understand the spatial usage patterns of health facilities in the Hlabisa district of South Africa. METHODOLOGY: We mapped and interviewed more than 23 000 homesteads (approximately 200 000 people) in Hlabisa district, South Africa and spatially analysed their modal primary health usage patterns using a geographical information system. We generated contour maps of health service use and quantified the relationship between clinic catchments and distance-defined catchments using inclusion and exclusion error. We propose the distance usage index (DUI) as an overall spatial measure of clinic usage. This index is the sum of the distances from clinic to all client homesteads divided by the sum of the distances from clinic to all homesteads within its distance-defined catchment. The index encompasses inclusion, exclusion, and strength of patient attraction for each clinic. RESULTS: Eighty-seven per cent of homesteads use the nearest clinic. Residents of homesteads travel an average Euclidean distance of 4.72 km to attend clinics. There is a significant logarithmic relationship between distance from clinic and their use by homesteads (r(2)=0.774, P < 0.0001). The DUI values range between 31 and 198% (mean=110%, SD=43.7) for 12 clinics and highlight clinic usage patterns across the district. CONCLUSIONS: The DUI is a powerful and informative composite measure of clinic usage. The results of the study have important implications for health care provision in developing countries.  相似文献   
998.
Activity of choline acetylase (ChAT) was measured in basal forebrain cholinergic nuclei and in projection sites of these cells in the hippocampus and cortex of young rats and of aged rats who showed impaired performance on the radial arm maze. Decreased ChAT activity was found in the vertical diagonal band nucleus, the dentate gyrus and striatum of aged rats.  相似文献   
999.
1000.
The health care system in the United States has a shortage of nurses. A careful planning of nurse resources is needed to ease the health care system from the burden of the nurse shortage and standardize nurse workload. An earlier research study developed a data-integrated simulation to evaluate nurse-patient assignments (SIMNA) at the beginning of a shift based on a real data set provided by a northeast Texas hospital. In this research, with the aid of the same SIMNA model, two policies are developed to make nurse-to-patient assignments when new patients are admitted during a shift. A heuristic (HEU) policy assigns a newly-admitted patient to the nurse who has performed the least assigned direct care among all the nurses. A partially-optimized (OPT) policy seeks to minimize the difference in workload among nurses for the entire shift by estimating the assigned direct care from SIMNA. Results comparing HEU and OPT policies are presented.  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-23

京公网安备 11010802026262号