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   2810篇
  免费   264篇
  国内免费   12篇
耳鼻咽喉   25篇
儿科学   91篇
妇产科学   49篇
基础医学   453篇
口腔科学   36篇
临床医学   301篇
内科学   535篇
皮肤病学   56篇
神经病学   160篇
特种医学   171篇
外科学   345篇
综合类   172篇
一般理论   2篇
预防医学   392篇
眼科学   31篇
药学   134篇
肿瘤学   133篇
  2021年   48篇
  2020年   24篇
  2019年   29篇
  2018年   45篇
  2017年   28篇
  2016年   37篇
  2015年   52篇
  2014年   65篇
  2013年   96篇
  2012年   116篇
  2011年   98篇
  2010年   62篇
  2009年   87篇
  2008年   120篇
  2007年   119篇
  2006年   117篇
  2005年   95篇
  2004年   96篇
  2003年   102篇
  2002年   96篇
  2001年   93篇
  2000年   108篇
  1999年   89篇
  1998年   69篇
  1997年   62篇
  1996年   82篇
  1995年   36篇
  1994年   51篇
  1993年   33篇
  1992年   63篇
  1991年   70篇
  1990年   54篇
  1989年   62篇
  1988年   68篇
  1987年   61篇
  1986年   45篇
  1985年   53篇
  1984年   31篇
  1983年   27篇
  1981年   21篇
  1980年   20篇
  1979年   32篇
  1977年   28篇
  1976年   25篇
  1975年   26篇
  1974年   19篇
  1972年   22篇
  1971年   24篇
  1970年   21篇
  1969年   21篇
排序方式: 共有3086条查询结果,搜索用时 15 毫秒
41.
42.
43.
Slowly mounting interest in the provider community in delivery system reform badly underestimates the extent to which major reconfiguration is already being engineered by aggressive purchasers. The once widely held view that provider-sponsored integrated firms represent the ideal health care system is being challenged by purchasers who are crafting, through short- and long-term selective contracting, provider networks that offer many of the same advantages ascribed to integrated firms. Three alternative approaches to restructuring delivery systems are examined and appraised in terms of how each may or may not be able to satisfy purchaser demands. The relentless pursuit of better cost management will have profound consequences for health care providers and their managers. Major redeployment of resources will occur as the industry converts from a hospital-centered to a continuum of care-centered management philosophy.  相似文献   
44.
Acute porphyria is rare in orientals. We describe a Chinese woman with recurrent generalised tonic-clonic seizures and abdominal pain. Genomic DNA studies identified a heterozygous base substitution from guanine to adenine at nucleotide position 503, resulting in substitution of arginine by histidine at position 168 of the protein (R168H). This genetic abnormality is similar to the mutation reported in Caucasians with variegate porphyria. To the best of our knowledge, this is the first report in the English literature a Chinese patient with variegate porphyria with an identifiable mutation. A brief review of porphyria is presented.  相似文献   
45.
When a time-limited day treatment program was reconfigured to serve individuals with long-standing psychotic disorders, the number of treatment episodes exceeding six months rose to 70%. To justify this concentration of resources, the program needed methods to identify individuals for whom sustained treatment was appropriate. This report describes development of utilization review methods adapted to publicly funded day treatment of individuals with serious mental illness and training of clinicians in new documentation skills. Data from three years of operation suggest that symptom severity is not a reliable indicator of medical necessity in day treatment. As expected with a clinically based system, a composite measure of benefit and medical necessity indicators weighted toward functioning in living, learning, working, and socializing environments predicted physician reviewer denial of continued day treatment, but length of stay did not.  相似文献   
46.
The Dietary Risk Assessment (DRA) is a brief dietary assessment tool used to identify dietary behaviors associated with cardiovascular disease. Intended for use by physicians and other nondietitians, the DRA identifies healthful and problematic dietary behaviors and alerts the physician to patients who require further nutrition counseling. To determine the relative validity of this tool, we compared it to the 7-Day Dietary Recall (an instrument developed to assess intake of dietary fat) and to the average of 7 telephone-administered 24-hour dietary recalls. Forty-two free-living subjects were recruited into the study. The 7-Day Dietary Recall and DRA were administered to each subject twice, at the beginning and the end of the study period, and the 24-hour recalls were conducted during the intervening time period. Correlation coefficients were computed to compare the food scores derived from the 3 assessment methods. Correlations between the DRA and 7-Day Dietary Recall data were moderate (r = .47, on average, for postmeasures); correlations between the DRA and 24-hour recalls were lower. The ability of the DRA to assess dietary fat consumption and ease of administration make it a clinically useful screening instrument for the physician when counseling patients about dietary fat reduction.  相似文献   
47.
Screening methods for thyroid hormone disruptors   总被引:15,自引:0,他引:15  
The U.S. Congress has passed legislation requiring the EPA to implement screening tests for identifying endocrine-disrupting chemicals. A series of workshops was sponsored by the EPA, the Chemical Manufacturers Association, and the World Wildlife Fund; one workshop focused on screens for chemicals that alter thyroid hormone function and homeostasis. Participants at this meeting identified and examined methods to detect alterations in thyroid hormone synthesis, transport, and catabolism. In addition, some methods to detect chemicals that bind to the thyroid hormone receptors acting as either agonists or antagonists were also identified. Screening methods used in mammals as well as other vertebrate classes were examined. There was a general consensus that all known chemicals which interfere with thyroid hormone function and homeostasis act by either inhibiting synthesis, altering serum transport proteins, or by increasing catabolism of thyroid hormones. There are no direct data to support the assertion that certain environmental chemicals bind and activate the thyroid hormone receptors; further research is indicated. In light of this, screening methods should reflect known mechanisms of action. Most methods examined, albeit useful for mechanistic studies, were thought to be too specific and therefore would not be applicable for broad-based screening. Determination of serum thyroid hormone concentrations following chemical exposure in rodents was thought to be a reasonable initial screen. Concurrent histologic evaluation of the thyroid would strengthen this screen. Similar methods in teleosts may be useful as screens, but would require indicators of tissue production of thyroid hormones. The use of tadpole metamorphosis as a screen may also be useful; however, this method requires validation and standardization prior to use as a broad-based screen.  相似文献   
48.
49.
50.
Metal ions and human sperm mannose receptors   总被引:5,自引:0,他引:5  
Zinc and lead concentrations were measured in seminal plasma from fertile donors, infertile men with varicocoele and men undergoing work-ups for in vitro fertilization. Ejaculated spermatozoa from these subjects were incubated in vitro with various metal ions and/or dibromoethane and dibromochloropropane. Mannose receptor expression was correlated with metal and toxicant levels. Sperm distributions of potassium channels were compared with lead ions and calcium channels with zinc ions. Mannose receptor expression by capacitated spermatozoa increased linearly with seminal plasma zinc levels, and correlated inversely with lead levels. Cobalt had no effect on mannose receptor expression, but nickel had a concentration-dependent biphasic effect. Mannose receptor expression was not affected by dibromoethane and dibromochloropropane if the cholesterol content of the sperm membrane was high, but mannose receptor expression was decreased in low cholesterol spermatozoa by exposures below estimated permissive exposure limits. Potassium channels and lead ions co-localized over the entire head of human spermatozoa, while both calcium channels and zinc ions were confined to the equatorial segment of the head. Mannose receptor expression on the external surface of the human sperm plasma membrane is a biomarker for the effects of transition and heavy metals and organic toxicants on sperm fertility potential.  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