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   513263篇
  免费   33996篇
  国内免费   613篇
耳鼻咽喉   6892篇
儿科学   16833篇
妇产科学   13574篇
基础医学   85035篇
口腔科学   14471篇
临床医学   44307篇
内科学   93515篇
皮肤病学   12154篇
神经病学   36197篇
特种医学   18463篇
外国民族医学   63篇
外科学   77042篇
综合类   8467篇
一般理论   118篇
预防医学   38937篇
眼科学   12126篇
药学   40517篇
中国医学   1006篇
肿瘤学   28155篇
  2018年   4927篇
  2015年   4513篇
  2014年   6065篇
  2013年   9549篇
  2012年   12883篇
  2011年   14287篇
  2010年   8314篇
  2009年   7780篇
  2008年   13700篇
  2007年   14711篇
  2006年   14948篇
  2005年   14365篇
  2004年   14060篇
  2003年   13412篇
  2002年   13284篇
  2001年   24083篇
  2000年   25097篇
  1999年   20563篇
  1998年   5431篇
  1997年   4709篇
  1996年   5043篇
  1995年   4626篇
  1994年   4319篇
  1993年   4136篇
  1992年   15729篇
  1991年   16318篇
  1990年   16426篇
  1989年   15800篇
  1988年   14577篇
  1987年   14421篇
  1986年   13597篇
  1985年   12982篇
  1984年   9630篇
  1983年   8249篇
  1982年   4561篇
  1981年   4230篇
  1979年   9420篇
  1978年   6855篇
  1977年   5772篇
  1976年   5602篇
  1975年   6396篇
  1974年   7634篇
  1973年   7130篇
  1972年   6960篇
  1971年   6685篇
  1970年   6172篇
  1969年   5888篇
  1968年   5559篇
  1967年   5012篇
  1966年   4450篇
排序方式: 共有10000条查询结果,搜索用时 984 毫秒
891.
892.
893.
The content of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and norepinephrine (NE) was analysed in 71 human spinal cords obtained post-mortem. The highest content of 5-HT, 5-HIAA and NE was found in the lumbar enlargement of the spinal cord. 5-HT and 5-HIAA content increased from fetal to adult spinal cord whereas the content of NE decreased. Characteristic segmental distribution of measured monoamines was present in adult spinal cord only. In two patients spinal cord lesion led to the reduction in spinal cord content of 5-HT, 5-HIAA and NE and loss of characteristic segmental distribution of these substances. These results are in general agreement with observations on spinal cord of different animal species.  相似文献   
894.
895.
896.
Irradiation and choroidal melanoma.   总被引:2,自引:2,他引:0       下载免费PDF全文
  相似文献   
897.
Previous studies of respiratory disorders in workers exposed to pulverised fuel ash (PFA) have been confined to radiological effects that were found to be minimal. The present survey included 268 men (88% of the defined population) with a history of more than 10 years exposure to PFA in six power stations in the south east of England. Respiratory questionnaires with full occupational histories were obtained from all of these subjects, of whom 207 were actively employed and 61 had retired; 243 had lung function tests and 208 had chest x ray examinations. The men were grouped, using their occupational histories, into high, medium, and low exposure categories. Dust concentrations were obtained by personal sampling on a representative sample of men from the three exposure categories. Lung function tests showed that a modest effect on forced vital capacity, vital capacity, forced expiratory volume in one second, peak flow, and gas transfer (DCO) was associated with prolonged heavy exposure to PFA. The men with prolonged heavy exposure also showed higher prevalences of respiratory symptoms. No definite relation between exposure and x ray changes was established. The results of this cross sectional survey indicate that exposures to PFA should not exceed the limits recommended by the Health and Safety Executive for low toxicity dusts.  相似文献   
898.
Disorders in the postnatal nervous, immune, and endocrine regulation systems were revealed in the progeny of rats irradiated during the preimplantation period of embryogenesis. These disorders persist till adult age. The direction of disorders confirms the hypothesis about memorization of changed proliferative properties of embryonal cells during the development of the (pro)endocrine system of a new organism. Memorization results in distortion of postnatal nervous immunoendocrine regulation: hypertrophy of the endocrine component and coadaptive underdevelopment of the nervous and immune components. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 8, pp. 164–166, August, 1998  相似文献   
899.
OBJECTIVE: To provide Canadian physicians with comprehensive, evidence-based guidelines for the nonpharmacologic management and prevention of gestational hypertension and pre-existing hypertension during pregnancy. OPTIONS: Lifestyle modifications, dietary or nutrient interventions, plasma volume expansion and use of prostaglandin precursors or inhibitors. OUTCOMES: In gestational hypertension, prevention of complications and death related to either its occurrence (primary or secondary prevention) or its severity (tertiary prevention). In pre-existing hypertension, prevention of superimposed gestational hypertension and intrauterine growth retardation. EVIDENCE: Articles retrieved from the pregnancy and childbirth module of the Cochrane Database of Systematic Reviews; pertinent articles published from 1966 to 1996, retrieved through a MEDLINE search; and review of original randomized trials from 1942 to 1996. If evidence was unavailable, consensus was reached by the members of the consensus panel set up by the Canadian Hypertension Society. VALUES: High priority was given to prevention of adverse maternal and neonatal outcomes in pregnancies with established hypertension and in those at high risk of gestational hypertension through the provision of effective nonpharmacologic management. BENEFITS, HARMS AND COSTS: Reduction in rate of long-term hospital admissions among women with gestational hypertension, with establishment of safe home-care blood pressure monitoring and appropriate rest. Targeting prophylactic interventions in selected high-risk groups may avoid ineffective use in the general population. Cost was not considered. RECOMMENDATION: Nonpharmacologic management should be considered for pregnant women with a systolic blood pressure of 140-150 mm Hg or a diastolic pressure of 90-99 mm Hg, or both, measured in a clinical setting. A short-term hospital stay may be required for diagnosis and for ruling out severe gestational hypertension (preeclampsia). In the latter case, the only effective treatment is delivery. Palliative management, dependent on blood pressure, gestational age and presence of associated maternal and fetal risk factors, includes close supervision, limitation of activities and some bed rest. A normal diet without salt restriction is advised. Promising preventive interventions that may reduce the incidence of gestational hypertension, especially with proteinuria, include calcium supplementation (2 g/d), fish oil supplementation and low-dose acetylsalicylic acid therapy, particularly in women at high risk for early-onset gestational hypertension. Pre-existing hypertension should be managed the same way as before pregnancy. However, additional concerns are the effects on fetal well-being and the worsening of hypertension during the second half of pregnancy. There is, as yet, no treatment that will prevent exacerbation of the condition. VALIDATION: The guidelines share the principles in consensus reports from the US and Australia on the nonpharmacologic management of hypertension in pregnancy.  相似文献   
900.
Caring for elderly people at home: the consequences to caregivers   总被引:2,自引:1,他引:1       下载免费PDF全文
The emphasis on home-based care is one important aspect of health services restructuring initiatives in Canada. Fundamental to the preference for home-based care over institutional care is the expectation that family caregivers will be available in the home to support patients who would otherwise be in an institution. The authors explore the potential impact of this devolution of services from institutions to the home in 2 vulnerable patient populations--elderly patients with dementia and elderly patients with terminal illnesses. Community-based surveillance strategies are needed to determine the true health, quality-of-life and economic outcomes of these restructuring initiatives.  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