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   2802865篇
  免费   202720篇
  国内免费   9701篇
耳鼻咽喉   37758篇
儿科学   90207篇
妇产科学   77700篇
基础医学   394248篇
口腔科学   76978篇
临床医学   253090篇
内科学   557785篇
皮肤病学   67378篇
神经病学   229370篇
特种医学   107434篇
外国民族医学   791篇
外科学   421360篇
综合类   57557篇
现状与发展   6篇
一般理论   1019篇
预防医学   206629篇
眼科学   62950篇
药学   206413篇
  9篇
中国医学   6929篇
肿瘤学   159675篇
  2021年   21663篇
  2019年   22331篇
  2018年   31991篇
  2017年   24627篇
  2016年   28348篇
  2015年   31889篇
  2014年   43887篇
  2013年   64928篇
  2012年   86202篇
  2011年   90660篇
  2010年   54806篇
  2009年   52627篇
  2008年   84606篇
  2007年   90043篇
  2006年   91484篇
  2005年   87233篇
  2004年   83865篇
  2003年   81010篇
  2002年   78079篇
  2001年   142775篇
  2000年   145942篇
  1999年   122852篇
  1998年   34472篇
  1997年   30444篇
  1996年   30221篇
  1995年   29235篇
  1994年   26774篇
  1993年   24961篇
  1992年   93796篇
  1991年   89721篇
  1990年   86578篇
  1989年   83762篇
  1988年   76596篇
  1987年   74820篇
  1986年   69916篇
  1985年   66452篇
  1984年   49006篇
  1983年   41373篇
  1982年   24113篇
  1981年   21397篇
  1979年   42442篇
  1978年   29569篇
  1977年   25213篇
  1976年   23005篇
  1975年   24615篇
  1974年   28870篇
  1973年   27353篇
  1972年   25734篇
  1971年   23941篇
  1970年   22009篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
We tested the urine of 30 infants 6 weeks to 7 months of age after they received standard 10-micrograms (0.5-ml) doses of HbOC (HibTITER) Haemophilus influenzae b (Hib) conjugate vaccine for the presence of Hib antigenuria using a commercially available latex particle agglutination assay (Directigen). Urines were collected within 1 hour, from 1 to 3 hours, at 24 hours and at 3, 6 and 9 days after vaccine administration and reactions were quantitated from 0 to 3+. In contrast to previous studies in older children which showed little or no antigenuria following HbOC vaccination, our study shows that in infants intense Hib antigenuria is evident within 2 to 3 hours and persists 3 days after vaccine administration and that less intense antigenuria may be detected in some infants for several days. With efficacious vaccines now being used in 2- to 6-month-old infants, invasive Hib disease may soon be limited to infants of this age just before their seroconversion. It should be recognized that antigenuria occurs for several days after vaccination with Hib conjugate vaccines and that it could be erroneously interpreted as evidence of invasive Hib infection.  相似文献   
963.
We describe a familial case of Marfan's syndrome with associated intrathoracic stomach detected during the neonatal period. The patient developed a primitive leukemia at 3 months of age. Acute leukemia in a patient with Marfan's syndrome has not previously been reported.  相似文献   
964.
Background The appearance of eosinophils is a hallmark sign of the allergic late-phase response (LPR). Eosinophil cationic protein (ECP), a readily measurable product released from activated eosinophils, has so far not been evaluated in the ocular LPR. Objective Two sets of trials were performed in order to investigate changes of local and systemic eosinophil activity and their possible link with symptoms and hyper-reactivity in the allergic LPR in the eye. Methods In the first experiment, ECP was analysed in tears and serum and the clinical reaction was evaluated during a 72-h time–course after a single, high-dose allergen challenge out of season in one eye of 15 pollen-sensitized volunteers. In a second experiment, the hypothesis of an increased clinical response to an allergen challenge in an eye that had been provoked with allergen 48h previously was tested in nine sensitized individuals. Results In the first experiment, symptoms at 10 min and 2, 4, 6, 8 and 24 h significantly exceeded base line scores of the challenged eyes. Tear ECP was significantly elevated in challenged eyes compared to contralateral eyes at 6, 8 and 24 h. In addition, symptoms and ECP release correlated significantly at the 24-h evaluation. Serum ECP remained unchanged throughout the study period. In the second experiment, conjunctival hyperreactivity 48h after an allergen challenge was not confirmed. Conclusion ECP secretion occurs in the experimental ocular LPR and is in part associated with the magnitude of the clinical reaction, which suggests a truly pathogenic role of the activated eosinophil in pollen-induced allergic conjunctivitis.  相似文献   
965.
Reluctance to use kidneys from older donors (>50 years of age) is based on reports of inferior results. We reviewed our experience with 45 kidneys transplanted from older donors. Primary nonfunction, immediate graft function, and 1-, 2- and 3-year graft survival rates were similar to those obtained with kidneys transplanted from donors aged between 20 and 40 years. Renal function at 1 year (as measured by serum creatinine) was poorer in kidneys from older donors. No beneficial effect with respect to graft survival was noted with cyclosporin therapy compared to conventional immunosuppression; however, the numbers are small. We conclude that kidneys from older donors are a valuable source for transplantation.  相似文献   
966.
Background : The clinical course of chronic hepatitis B is variable. Patients with hepatic decompensation, bridging necrosis or an alpha-fetoprotein level greater than 100 ng/mL during an exacerbation of hepatitis have a high risk of developing cirrhosis. This study was conducted to evaluate the effect of colchicine in the prevention of cirrhosis in such patients.
Methods : Patients with risk factor(s) were randomized to receive either colchicine 5 mg/week or no specific treatment, the end point being development of cirrhosis.
Results : After a follow up period of 4 years, the treatment group had a marked reduction in exacerbations of acute hepatitis (32% vs. 63%/patient/year, P <0.005). Seven out of 38 patients in the treatment group and 10 out of 27 patients in the control group developed cirrhosis. The calculated cumulative incidence of cirrhosis by the end of first, second, third and fourth years in the treatment group was 8.7, 18.6, 32 and 32%, respectively. The corresponding figures in the control group were 30, 35.5, 46.3 and 73.2%, respectively, with a P -value of 0.057.
Conclusions : The results suggest that colchicine may prevent cirrhosis in chronic hepatitis B patients with risk factor(s), possibly by suppressing exacerbations of hepatitis through an anti-inflammatory effect.  相似文献   
967.
The present study explored the role of murine monocyte chemotactic protein (MCP) in the T cell-mediated hypersensitive granulomatous response to Schistosoma mansoni eggs. The study examined the time course of local production, contribution to cellular infiltration, and the role of T cells in endogenous regulation. Synchronized pulmonary granulomas were induced under conditions of primary and secondary states of immunity. Primer-directed polymerase chain reaction analysis showed increased MCP mRNA expression in granulomatous lungs, mainly in the secondary response. Levels of MCP were measured by enzyme-linked immunosorbent assay in cultures of intact granulomas. Spontaneous MCP production was modest in primary granuloma cultures, reaching a maximum of 5.7 +/- 0.9 ng/ml by 16 days. In contrast, the secondary response showed augmented and accelerated production, achieving 13 +/- 2.0 ng/ml by 2 days. Immunohistochemical staining revealed the strongest MCP expression within microvascular adventitial cells or pericytes as well as in scattered mononuclear cells associated with granulomas. Staining was not detected in normal lungs. Passive immunization with anti-MCP-1 antibodies caused a 40% reduction in the secondary granuloma area but did not significantly affect the primary response. With adoptive cell transfer and T cell subset depletion, it was shown that Thy-1+ and CD5+ cells augmented, whereas CD8+ cells appeared to impair, MCP production. This provides direct evidence that MCP is involved in secondary Th2-mediated response to schistosome eggs and is subject to regulation by T cells.  相似文献   
968.
969.
Mycobacteriosis due to Mycobacterium genavense in six pet birds.   总被引:11,自引:7,他引:4       下载免费PDF全文
Six cases of mycobacteriosis due to Mycobacterium genavense in three budgerigars (Melopsittacus undulatus), one orange-winged amazon (Amazona amazonica), one flycatcher (Cyanoptila cyanomelana), and one zebra finch (Taeniopygia guttata) are discussed. Gross lesions associated with the infection included a high degree of muscular wasting (five cases), hepatomegaly (four cases), and thickening of the wall of the small intestine (four cases). Granulomas were found in the lung (one case) and the subcutis (one case). Acid-fast bacilli were detected in the liver of all six birds. Only the use of acidic BACTEC mediums consistently led to growth, whereas the egg-based medium failed. These findings point to a possible role of the environment as a reservoir for M. genavense.  相似文献   
970.
The decoction of Sclerocarya birroea Hochst. shows hypoglycaemic effects, an increase in plasma IRI in normal rats and an incremented oral-glucose tolerance. The decoction is also active against diet-induced hypercholesterolaemia.  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