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   2587321篇
  免费   185065篇
  国内免费   7569篇
耳鼻咽喉   34272篇
儿科学   85198篇
妇产科学   71569篇
基础医学   363570篇
口腔科学   69658篇
临床医学   234496篇
内科学   515499篇
皮肤病学   62450篇
神经病学   213440篇
特种医学   99879篇
外国民族医学   736篇
外科学   386420篇
综合类   50391篇
现状与发展   5篇
一般理论   968篇
预防医学   196166篇
眼科学   56678篇
药学   187989篇
  8篇
中国医学   5332篇
肿瘤学   145231篇
  2021年   19980篇
  2019年   20621篇
  2018年   29285篇
  2017年   22592篇
  2016年   26224篇
  2015年   29501篇
  2014年   40439篇
  2013年   60421篇
  2012年   80221篇
  2011年   84482篇
  2010年   51000篇
  2009年   49145篇
  2008年   79024篇
  2007年   83829篇
  2006年   85565篇
  2005年   81725篇
  2004年   78720篇
  2003年   76038篇
  2002年   73329篇
  2001年   128407篇
  2000年   131329篇
  1999年   110497篇
  1998年   31252篇
  1997年   27921篇
  1996年   28218篇
  1995年   27383篇
  1994年   25067篇
  1993年   23420篇
  1992年   85160篇
  1991年   81564篇
  1990年   78787篇
  1989年   76063篇
  1988年   69469篇
  1987年   67998篇
  1986年   63543篇
  1985年   60511篇
  1984年   44941篇
  1983年   37944篇
  1982年   22456篇
  1981年   19984篇
  1979年   38962篇
  1978年   27439篇
  1977年   23252篇
  1976年   21495篇
  1975年   22814篇
  1974年   26787篇
  1973年   25371篇
  1972年   23750篇
  1971年   21955篇
  1970年   20185篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
BACKGROUND. Studies have documented the potential contributions of preventive health care programs. Yet little is known about which screening tests should be included in public health programs for older persons. This study offers recommendations regarding these tests. METHODS. The recommendations come from synthesizing the findings of the US Preventive Services Task Force, the literature, and the consensus of experts in geriatrics, gerontology, and health policy research. The literature was evaluated to identify methodologically sound studies of the prevalence of selected disorders and benefits and availability of screening procedures for those disorders. Experts from various fields specializing in the care of the elderly formed panels to assist in evaluating the literature and providing further information from gerontological and public health perspectives. RESULTS. We recommend vision testing for refractive error; inspection of the skin surface for fungal infection and skin cancer, drug eruptions, and xerosis; a history for symptoms of xerosis; audiometric testing for presbycusis; surveys for hearing loss; otoscopic inspection for cerumen impaction; dental examination for caries; measurement of blood pressure for hypertension; and breast examination and mammography for cancer. CONCLUSIONS. Our study suggests that these screening procedures are useful for public health screening programs. More information is needed on the effects of screening services on the health and functioning of older persons.  相似文献   
993.
Previous studies indicate that crude oil leads to increased pigmentation and erythema (sunburn) in response to sunlight in exposed individuals. However, no information is currently available concerning whether crude oil exposure might enhance the immunosuppressive effects of solar ultraviolet radiation (UVR) on the skin. In order to address this question, the back skin of shaved, female C3H/HeN mice was exposed to crude oil with or without subsequent treatment with medium-wavelength (UVB) (200 J/m2) or long-wavelength (UVA) (20,000 J/m2) UVR. Immune function was assessed in treated mice by measuring their ability to mount contact hypersensitivity responses to a hapten (2,4-dinitro-1-flyorobenzene, DNGFB) applied to the site of crude oil and UVR treatment as determined by ear swelling upon subsequent challenge. Since Langerhans cells represent an important component of immunity within the skin and because suppression of contact hypersensitivity following UVR treatment is often accompanied by disappearance of Langerhans cells from the epidermis, the impact of these agents on epidermal Langerhans cell density was also analyzed. This was accomplished by enumerating IA-positive cells within the epidermis of treated skin. In these studies, crude oil alone induced inhibition of contact hypersensitivity but had no effect on epidermal Langerhans cells. In contrast, combined treatment with crude oil and UVA led to suppression of contact hypersensitivity, which was accompanied by depletion of epidermal Langerhans cells.  相似文献   
994.
995.
In the processing of the waste products of phosphorus containing fertilizer production, several major health-related factors were identified depending on the industrial site's peculiarities: unfavourable microclimate conditions (both cold and heat), relative temperature differences, noise and vibration caused by the equipment, semi-product's, additives' and finished product's dusts, fluorine- and phosphorus-containing substances' affects and poor illumination. The proposed data were used for health-related improvements in the occupational conditions.  相似文献   
996.
997.
998.
999.
Chick nutritional encephalomalacia and prostanoid formation   总被引:2,自引:0,他引:2  
Nutritional encephalomalacia (NE) was induced in young chicks using a diet low in vitamin E and containing 8% ethyl esters derived from safflower oil fatty acids (S-E group). The same diet with added alpha-tocopheryl acetate (S+E) failed to produce the pathology, and chicks receiving aerated linseed oil--high in alpha-linolenic acid and low in alpha-tocopherol (L-E)--did not develop symptoms. Formation of metabolites from labeled arachidonic acid (AA) by thrombocytes was similar in the S+E and S-E groups, yielding thromboxane B2 (TXB2) and hydroxy fatty acids as the major products. Collagen-induced thrombocyte aggregation and TXB2 production were not significantly different in the S-E and S+E groups, but aggregation values and TXB2 synthesis were significantly less in the L-E group than in the ataxic S-E chicks. Prostaglandin E2 production by aortal rings was significantly influenced by the diet; S-E yielded the highest value and L-E the lowest. These results show that alpha-linolenic acid causes alterations in the AA metabolism and thrombocyte function in young chicks.  相似文献   
1000.
The digestive and metabolic effects of inulin (from chicory) were studied in rats adapted to semipurified diets containing 0, 5, 10 or 20% inulin (wt/wt). Moderate levels of inulin (5-10%) did not significantly affect food intake or body weight gain. Dietary inulin resulted in considerably greater cecal fermentation and a significantly greater intraluminal concentration of propionate (peaking at 58.4 mmol/L). A lower concentration of acetate (42.6 mmol/L) was observed in rats fed 20% inulin. Lactic fermentations were observed in rats fed the 10 or 20% inulin diets. The cecal pool of volatile fatty acids tended to reach a plateau in rats fed diets containing more than 10% inulin (up to 600-700 mumol), but volatile fatty acid absorption was a slightly hyperbolic function of the dietary inulin level. Butyrate absorption was proportionally lower than that of propionate. Inulin-containing diets induced an enlargement of the cecal pool of calcium, phosphate and (to a lesser extent) magnesium. There was also an enhanced absorption of these divalent cations. The cecal pool of bile acids was greater in rats fed inulin, and this oligosaccharide displayed a slight hypocholesterolemic effect, even in rats fed the 5% inulin diet. However, plasma triglycerides were depressed only in rats fed the 20% inulin diet. In conclusion, inulin seems very effective in promoting propionic fermentation and in enhancing the calcium content of the large intestine. However, high levels of inulin (greater than 10%) may affect growth in rats and lead to acidic (pH 5.65) cecal fermentation.  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