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   3213782篇
  免费   235532篇
  国内免费   8649篇
耳鼻咽喉   43399篇
儿科学   107549篇
妇产科学   88872篇
基础医学   454966篇
口腔科学   89515篇
临床医学   294599篇
内科学   629148篇
皮肤病学   75644篇
神经病学   262505篇
特种医学   123648篇
外国民族医学   1009篇
外科学   479245篇
综合类   67697篇
现状与发展   5篇
一般理论   1274篇
预防医学   249488篇
眼科学   72470篇
药学   234712篇
  11篇
中国医学   6602篇
肿瘤学   175605篇
  2019年   25126篇
  2018年   35583篇
  2017年   27354篇
  2016年   31447篇
  2015年   35444篇
  2014年   48806篇
  2013年   74048篇
  2012年   98104篇
  2011年   103875篇
  2010年   62473篇
  2009年   59570篇
  2008年   97104篇
  2007年   102987篇
  2006年   104946篇
  2005年   100595篇
  2004年   97241篇
  2003年   93931篇
  2002年   90526篇
  2001年   153147篇
  2000年   156924篇
  1999年   132430篇
  1998年   38118篇
  1997年   34016篇
  1996年   34074篇
  1995年   32995篇
  1994年   30422篇
  1993年   28327篇
  1992年   103751篇
  1991年   100255篇
  1990年   97453篇
  1989年   94120篇
  1988年   86040篇
  1987年   84842篇
  1986年   79434篇
  1985年   76093篇
  1984年   56748篇
  1983年   48116篇
  1982年   28631篇
  1981年   25657篇
  1979年   50587篇
  1978年   35971篇
  1977年   30512篇
  1976年   28431篇
  1975年   30153篇
  1974年   35923篇
  1973年   34243篇
  1972年   31853篇
  1971年   29656篇
  1970年   27337篇
  1969年   26080篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Malignancy larynx usually presents early, the common symptoms being hoarseness, pain thorat, cough and irritation of throat. An advanced malignancy is likely to be complicated by a pharyngo-cutaneous fistula. However it is an occurrence towards the end stage of the disease. Here we present a case of malignancy larynx primarily presenting as pharyngo-cutaneous fistula without any other symptoms.  相似文献   
992.
993.

Background  

Both diabetes and obesity syndromes are recognized to promote lumbar vertebral instability, premature osteodegeneration, exacerbate progressive osteoporosis and increase the propensity towards vertebral degeneration, instability and deformation in humans.  相似文献   
994.
995.
For many parents stopping life-sustaining medical treatment on their dying infant is psychologically impossible. Dostoevsky's insights into human behavior, particularly the fact that individuals do not want the anxiety and guilt associated with responsibility for making difficult decisions, might change the way physicians approach parents for permission to withdraw life-prolonging medical interventions on dying infants.  相似文献   
996.
To evaluate the main intake source of arsenic by the villagers from arsenic-affected families in Jalangi and Domkol blocks in Mushidabad district, West Bengal-India, we determined the concentrations of arsenic in tube-well water and in food composites, mainly including vegetables and cereals collected from the surveyed families which were cultivated in that region. The daily dietary intakes of arsenic by the villagers were estimated and the excretions of arsenic through urine and hair were determined. The arsenic concentrations in hair and urine of the studied population living in mild (2.78 microg/L), moderate (30.7 microg/L) and high (118 microg/L) arsenic-affected families were 133, 1,391 and 4,713 microg/kg and 43.1, 244 and 336 microg/L, respectively. The linear regressions show good correlations between arsenic concentrations in water vs hair (r(2)=0.928, p<0.001) and water vs urine (r(2)=0.464, p<0.01). Approximately 29.4%, 58.1% and 62.1% of adult population from mild, moderate and high arsenic-affected families were suffering from arsenical skin manifestations. The mean arsenic concentrations of food composites (vegetables and cereals) in high arsenic-affected families are not significantly different from mild arsenic-affected families. The daily dietary intakes of arsenic from water and food composites of the studied population, living in high, moderate and mild arsenic-affected families were 568, 228 and 137 microg, respectively. The linear regressions show good correlations between arsenic concentrations in hair vs daily dietary intake (r(2)=0.452, p<0.001) and urine vs daily dietary intake (r(2)=0.134, p<0.001). The water for drinking contributed 6.07%, 26.7% and 58.1% of total arsenic in our study from mild, moderate and high arsenic-affected families. The result suggested that the contaminated water from high arsenic-affected families should be the main source for intake of arsenic. On contrary, the contribution of arsenic-contaminated food composites from mild and moderate arsenic-affected families might be the main source for intake of arsenic. The Food and Agriculture Organization/World Health Organization (FAO/WHO) provisional tolerable weekly intake (PTWI) values of arsenic in our study were 3.32, 5.75 and 12.9 microg/kg body weight/day from mild, moderate and high arsenic-affected families, respectively, which is higher than the recommended PTWI value of arsenic (2.1 microg/kg body weight/day).  相似文献   
997.
A series of 1-alkyl-3,4-dihydroisoquinolines and the related 4-alkyl-1,2-dihydro-benzo[f]isoquinolines was synthesized using reactions of dialkylbenzylcarbinols and their naphthyl analogs with alkylcyanides. Experiments showed that 1-alkyl-6,7-dimethoxy-3,4-dihydroisoquinolines typically produce a hypotensive action, while the benzo-annelated structures usually exhibit a hypertensive effects. The most active compound decreases the arterial pressure in cats by 52 Torr and the effect lasts for about 4 hours. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 3, pp. 15–17, March, 2006.  相似文献   
998.
Extracts of the above-ground part of meadowsweet (Filipendula ulmaria L. Maxim.) demonstrate a pronounced antioxidant activity. It is established that 70% and 95% ethanol extracts contain the most active substances. Investigation of the chemical composition of the above-ground part of the plant and its 70% ethanol extract by means of qualitative reactions, thin-layer chromatography, and paper chromatography showed the presence of various phenolic compounds, including quercetin and its glycosides, dihydroquercetin, apigenin, rododendrol, esculetin, and m-hydroxybenzoic, salicylic, anisic, gallic, gentisic, ferulic, chlorogenic, and caffeic acids. __________ Translated From Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 12, Pp. 22–24, December, 2006.  相似文献   
999.

Background  

Patient falls in hospitals are common and may lead to negative outcomes such as injuries, prolonged hospitalization and legal liability. Consequently, various hospital falls prevention programs have been implemented in the last decades. However, most of the programs had no sustained effects on falls reduction over extended periods of time.  相似文献   
1000.
Molecular characterization of Wuchereria bancrofti is essential to develop suitable anti-filarial drugs and vaccines. We describe here isolation, sequence analysis and cloning of a partial cDNA of an enzyme superoxide dismutase from this parasite. The immunoscreening of a lambda zap W. bancrofti microfilarial (Mf) cDNA library with microfilaremic sera had resulted in the isolation of several seroreactive clones including, WbSOD. This clone contained a 309 bp insert and showed significant nucleotide and deduced amino acid sequence homologies to the superoxide dismutases of other nematode parasites. The antioxidant property of this enzyme may have important contribution in the defense mechanism of the parasite against host immune response.  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