全文获取类型
收费全文 | 2556篇 |
免费 | 229篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 106篇 |
妇产科学 | 26篇 |
基础医学 | 351篇 |
口腔科学 | 56篇 |
临床医学 | 363篇 |
内科学 | 613篇 |
皮肤病学 | 19篇 |
神经病学 | 200篇 |
特种医学 | 297篇 |
外国民族医学 | 1篇 |
外科学 | 223篇 |
综合类 | 48篇 |
一般理论 | 2篇 |
预防医学 | 211篇 |
眼科学 | 48篇 |
药学 | 144篇 |
中国医学 | 5篇 |
肿瘤学 | 74篇 |
出版年
2021年 | 24篇 |
2020年 | 21篇 |
2019年 | 30篇 |
2018年 | 39篇 |
2017年 | 27篇 |
2016年 | 42篇 |
2015年 | 39篇 |
2014年 | 65篇 |
2013年 | 60篇 |
2012年 | 89篇 |
2011年 | 77篇 |
2010年 | 65篇 |
2009年 | 92篇 |
2008年 | 85篇 |
2007年 | 88篇 |
2006年 | 78篇 |
2005年 | 82篇 |
2004年 | 92篇 |
2003年 | 85篇 |
2002年 | 79篇 |
2001年 | 66篇 |
2000年 | 63篇 |
1999年 | 61篇 |
1998年 | 62篇 |
1997年 | 62篇 |
1996年 | 78篇 |
1995年 | 58篇 |
1994年 | 48篇 |
1993年 | 56篇 |
1992年 | 66篇 |
1991年 | 51篇 |
1990年 | 59篇 |
1989年 | 68篇 |
1988年 | 72篇 |
1987年 | 70篇 |
1986年 | 76篇 |
1985年 | 42篇 |
1984年 | 30篇 |
1983年 | 31篇 |
1982年 | 35篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 23篇 |
1977年 | 29篇 |
1976年 | 28篇 |
1975年 | 30篇 |
1974年 | 21篇 |
1972年 | 21篇 |
1971年 | 23篇 |
1969年 | 16篇 |
排序方式: 共有2792条查询结果,搜索用时 0 毫秒
11.
A postal survey of 434 clinicians at four local hospitals was undertaken in order to identify the methods by which clinicians learn how to request permission for hospital autopsies and to assess the preferred techniques and timing of relevant communication skills training. The majority of 128 responding clinicians had learnt through personal experience with some assistance from senior colleagues and peers. Few clinicians appeared to have learnt through formal training. The preferred methods for the provision of communication skills training were training in small groups (such as seminars or tutorials) and observation of clinicians at work. The most desirable time for the provision of this training was considered to be between the beginning of the final undergraduate year and the end of the pre-registration house officer year. The communication skills training provided within medical education is in need of improvement. More emphasis should be given to clinical-task- or situation-specific applications such as requesting permission for autopsies. 相似文献
12.
Does altered biomechanics cause marrow edema? 总被引:21,自引:0,他引:21
13.
14.
Interaction of hyperthermia and metabolic inhibitors on the induction of chromosome damage in Chinese hamster ovary cells 总被引:1,自引:0,他引:1
We have examined the chromosomal effects of heating asynchronously growing Chinese hamster ovary (CHO K1) cells in the presence of actinomycin D or cycloheximide. Actinomycin D was found to strongly potentiate the chromosome damaging effects of heat shock, an effect correlated with a strong nonadditive reduction in cell survival. In contrast, cycloheximide treatment reduced heat shock induced chromosome damage and resulted in a significant nonadditive increase in cell survival following heat shock. The different effects of these two inhibitors on chromosomal damage and cell survival are correlated in part with their effects on the rate of DNA synthesis during heat shock. The results suggest that an important aspect of the interaction of heat and metabolic inhibitors involves changes in cell cycle phase distribution of and/or progression through the S phase of the cell cycle induced by drug treatment prior to and during heat shock. The data indicate that the protective effect of cycloheximide in heat shocked cells may involve altered cell cycle progression and/or phase distribution of cells during hyperthermia. 相似文献
15.
16.
Feasibility analysis is an important aspect of business planning. A feasibility study is a study of the impacts of revenues, cost, and returns on a decision. It helps answer the questions of "What share of total sales can be attained?" "What revenues will be generated?" "What costs will be incurred?" "What will be the return on investment?" The discipline of going through a systematic approach to analyze market demand, cost requirements, and return on investment will improve business decisions by eliminating risk and increasing the possibility of successful ventures. 相似文献
17.
Inst-Risk II: an approach to forecasting relative risk of future institutional placement. 总被引:2,自引:0,他引:2 下载免费PDF全文
This article describes a model development process that represents a useful step in classifying populations in terms of risk of institutionalization (Inst-Risk II). A four-category risk classification system--"High risk, Some risk, Low risk, and Very Low Risk"--was developed, based on combinations of measures of functional status, age, health status, demographics, and social supports. Our review of variables found by other researchers to be related to high risk of institutional placement, as well as our own research with Massachusetts elderly, confirmed functional impairment, diagnostic conditions, and advanced age to be major predictors of institutional placement. At the other extreme, Very Low risk status was indicated by combinations of functional independence, absence of health problems, and relatively younger age. Using baseline data of the kind that can be easily gathered and are often obtained in social agency screening interviews, our research indicates that this instrument differentiates among these risk status groups for two- to four-year periods. 相似文献
18.
Carol Smillie B.N. B.Ed. M.S.C. Katherine Coffin B.A. ME.D. Kathryn Porter B.A. Brenda Ryan B.A. M.B.A. 《Journal of community health》1988,13(3):156-170
The International Conference on Primary Health Care, meeting in Alma-Ata, in the Soviet Union, September 12, 1978, expressed the need for urgent action by all governments, all health and development workers and the world community, to protect and promote the health of all people of the world. The world was caught by the phrase which emerged from this conference, Health For All by the Year 2000 and many have examined the articles of the Alma-Ata declaration and tried to implement them in their corner of the world. This paper describes a community-based smoking-cessation program which was implemented in the province of Nova Scotia, Canada, during the years 1980–1984. Primary to this project was the belief that people have the right and the duty to participate individually and collectively in planning and implementing their health care. This paper describes one community's effort in putting this belief into practice.Carol Smillie, B.N. BE.d. M.S.c. is an Assistant Professor at the School of Nursing, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3J5, Katherine Coffin, BA, MEd is the Program Officer, Nova Scotia Office, Health Promotion Directorate Health and Welfare Canada, 5251 Duke Street, Halifax, Nova Scotia. Canada B3J 1P3. Kathryn Porter, B.A. (Gen)., is the Information and Education Coordinator, Nova Scotia Division Canadian Cancer Society. Brenda Ryan, B.A., M.B.A. is Program Evaluation Analysist, Nova Scotia Department of Health, 6088 Hollis Street, Halifax. Nova Scotia, Canada. This Project was funded by Health and Welfare Canada, Nova Scotia Department of Health, Nova Scotia Division Canadian Cancer Society, Requests for reprints should be addressed to: Professor Carol Smillie. 相似文献
19.
Siddiq T Patel VB Sherwood R Richardson PJ Preedy VR 《Experimental and molecular pathology》2001,70(1):19-30
Changes in tissue protein synthesis in hypertension have usually been measured in vitro in heart from acutely hypertensive rats without consideration of changes in atrial or pulmonary tissue or changes occurring in long-standing hypertension. The objective of the study was to investigate the in vivo changes in cardiopulmonary protein synthesis in three different rat models of chronic hypertension. Hypertension in aortic constriction, the Goldblatt model, and the bromoethylamine model were induced in rats for 30 days. At the end of the experimental period, in vivo rates of protein synthesis were measured with a flooding dose of [3H]phenylalanine (a method which effectively considers precursor pools). Concomitant measurements included quantification of contractile protein and RNA and DNA contents. Indices of protein breakdown were also assessed by selective measurement of protease activities. At the end of 30 days, aortic constriction induced marked increases in protein contents of the left ventricle, septum, left atria, and lungs. Accompanying changes included concomitant increases in RNA and DNA contents. Left ventricular myofibrillary, sarcoplasmic, and stromal protein contents increased in the aortic constriction model. Less marked changes occurred in the Goldblatt model, though the left atria were not significantly affected. In contrast, the bromoethylamine model had no effect on the protein or RNA contents of any region. In all cardiac regions of all three models, fractional rates of protein synthesis were not significantly affected. However, protein synthesis increased in the lungs of both the Goldblatt and bromoethylamine models at 30 days. Protease activities were decreased in the left ventricles of all three models at 30 days, with lysosomal protease activities declining in the aortic constriction model and cytoplasmic protease activities declining in the other two models. The failure of chronic hypertension to increase ventricular synthesis rates may represent inherent limitations in the time frame for measuring protein synthesis in vivo. However, at earlier time points (i.e., 10 days), the aortic constriction model was characterized by marked increases in left ventricular and atrial protein contents, RNA contents, and fractional rates of protein synthesis. This was consistent with the supposition that, in acute phases of hypertrophy, rates of protein synthesis increase, whereas in established hypertrophy, synthesis rates remain unchanged or decrease. The applicability of the aortic constriction model was investigated by examining the effects of the angiotensin converting enzyme inhibitor lisinopril (5 mg/kg/day). After 30 days treatment, lisinopril impeded the increase in left ventricular mixed and myofibrillar proteins. This effect was accompanied by an apparent increase in protein synthesis. In conclusion, although all three chronic models are able to induce hypertension, varying degrees of hypertrophy develop, which are more pronounced in the aortic constriction model. Accompanying changes include hypertrophy in the atria, reduced rates of ventricular proteolytic activity, and altered rates of protein metabolism in the lungs. 相似文献
20.
Rivara CB Sherwood CC Bouras C Hof PR 《The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology》2003,270(2):137-151
Betz cells are giant motoneurons located in layer Vb of the primate primary motor cortex. We conducted stereological analyses of Betz cells and neighboring pyramidal cells from the brains of six neurologically normal elderly humans to determine their volume, total number, and spatial distribution, and to relate these data to functional localization. The distribution of cellular volumes exhibits a bimodal pattern, delineating two different subpopulations. Betz cell volumes follow a mediolateral gradient, the largest Betz cells being located on the most medial part of the motor cortex. Additionally, the shape of Betz cells varies between the rostral and caudal parts of the primary motor cortex, supporting the notion that there are anatomically distinct zones in primary motor cortex. The total number of Betz cells per hemisphere accounts for about one-tenth of the total number of pyramidal cells in layer Vb. Analysis of spatial distribution using Voronoi tessellation revealed maximal clustering of Betz cells in a zone situated two-thirds from the midline along the mediolateral axis of the primary motor cortex. These data suggest that Betz cells have a discrete subregional distribution that may correspond to certain aspects of the functional parcellation of area 4. These results may offer a histological correlate of functional imaging studies and are relevant in the context of neurodegenerative diseases such as amyotrophic lateral sclerosis, progressive supranuclear palsy, and Guamanian amyotrophic lateral sclerosis/Parkinsonism-dementia, and in studies of normal brain aging. 相似文献