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   1695548篇
  免费   123335篇
  国内免费   3781篇
耳鼻咽喉   21730篇
儿科学   55634篇
妇产科学   46151篇
基础医学   241204篇
口腔科学   48741篇
临床医学   151304篇
内科学   333482篇
皮肤病学   38651篇
神经病学   131136篇
特种医学   63868篇
外国民族医学   242篇
外科学   257223篇
综合类   38946篇
现状与发展   4篇
一般理论   531篇
预防医学   124223篇
眼科学   40211篇
药学   123602篇
  7篇
中国医学   4475篇
肿瘤学   101299篇
  2021年   12785篇
  2019年   13521篇
  2018年   19950篇
  2017年   15213篇
  2016年   16613篇
  2015年   18957篇
  2014年   26212篇
  2013年   37940篇
  2012年   52724篇
  2011年   55415篇
  2010年   32769篇
  2009年   30691篇
  2008年   51514篇
  2007年   54793篇
  2006年   55252篇
  2005年   52535篇
  2004年   50737篇
  2003年   48147篇
  2002年   46366篇
  2001年   91782篇
  2000年   93605篇
  1999年   76959篇
  1998年   19717篇
  1997年   17267篇
  1996年   17391篇
  1995年   16742篇
  1994年   15289篇
  1993年   14071篇
  1992年   57381篇
  1991年   55270篇
  1990年   52970篇
  1989年   50747篇
  1988年   46131篇
  1987年   44937篇
  1986年   42226篇
  1985年   39987篇
  1984年   29348篇
  1983年   24908篇
  1982年   13898篇
  1979年   25529篇
  1978年   17574篇
  1977年   14907篇
  1976年   13874篇
  1975年   14563篇
  1974年   17630篇
  1973年   16944篇
  1972年   15673篇
  1971年   14453篇
  1970年   13431篇
  1969年   12517篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Quantitative studies of morbidity, food intake, and somatic growth were done prospectively during 14 mo for 70 children aged 5-18 mo in two Bangladeshi villages. When random-effect regression models were used, monthly changes in weight were inversely related to proportions of days in the month with fever and diarrhea and positively related to energy intake per kilogram body weight. Interestingly, weight changes did not vary with age in this interval. Estimates indicate that increasing energy intakes to the recommended World Health Organization level would have a significantly greater effect on weight gain than would the elimination of diarrhea and fever. With energy at recommended intake and diarrhea and fever prevalence as found in US children, weight gain is predicted to be near that of the international reference population. Therefore, interventions aimed at improving dietary intake may be as important as infection-control programs for improving growth of children in poor developing nations.  相似文献   
972.
We examined seven 1-d diet records kept during 1 y by 272 men and women instructed to follow a lipid-lowering diet while participating in a clinical trial of pravastatin, a new 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor. The mean percentage of calories from total fat and saturated, unsaturated, and monounsaturated fatty acids was similar throughout the year even though the patients knew they were taking an effective lipid-lowering agent. However, the diets of greater than 40% of women included less than two-thirds of the recommended dietary allowance (RDA) of folic acid, vitamins B-6 and D, and calcium and zinc; in men, folic acid and zinc intakes were low. We conclude that patients comply with lipid-lowering diets even when they know that they are receiving an effective serum lipid-lowering agent. However, for both men and women special attention should be given to the intake of several nutrients.  相似文献   
973.
DNR in the operating room. Not really a paradox   总被引:1,自引:0,他引:1  
S J Youngner  H F Cascorbi  J M Shuck 《JAMA》1991,266(17):2433-2434
  相似文献   
974.
OBJECTIVE.--To determine behavioral and demographic risk factors for human immunodeficiency virus (HIV) infection in central Africa. DESIGN.--Cross-sectional survey. SETTING.--Kigali, Rwanda. PARTICIPANTS.--A representative sample of 1458 childbearing women aged 19 to 37 years who were recruited from outpatient prenatal and pediatric clinics at the only community hospital in the city. MAIN OUTCOME MEASURE.--Antibodies to HIV assessed by enzyme immunoassay and confirmed by Western blot or indirect immunofluorescence. RESULTS.--The HIV seroprevalence was 32% overall. Infection rates were higher in women who were single, in those in steady relationships that began after 1981, and in the 33% of women reporting more than one lifetime sexual partner. Women in legal marriages or monogamous partnerships had lower rates of infection, but even low-risk women had prevalences on the order of 20%. History of venereal disease in the past 5 years, although the strongest risk factor in a multiple logistic analysis (odds ratio, 2.7; 95% confidence interval, 2.0 to 3.7), was reported by only 30% of those infected. Having a male sexual partner who drank alcohol or who had higher income were significant risk factors for HIV infection in the multivariate analysis, but use of oral contraceptives and having an uncircumcised partner were not. CONCLUSIONS.--The epidemic of the acquired immunodeficiency syndrome in Rwanda has spread beyond high-risk groups to the general population of women without known risk factors. For most of these women, a steady male partner is the source of their HIV risk and therefore a vital target for intervention efforts.  相似文献   
975.
Prevention of malaria   总被引:1,自引:0,他引:1  
S L Hoffman 《JAMA》1991,265(3):398-399
  相似文献   
976.
977.
Exposure of young children to group day-care settings increases the risk of illness and may result in higher use of medical care. These observations raise concerns that the use of such settings for early intervention programs for low-birth-weight infants may increase the already high burden of medical care costs incurred by these children and their families. To address the question of medical care use associated with center-based care, we examined the hospital-based and ambulatory care reported for participants of the Infant Health and Development Program. This project is a multisite randomized trial of an early intervention program for preterm low-birth-weight infants with an intervention including 2 years of center-based care. The Intervention group did not differ in hospital-based care and averaged only two more physicians' visits over the 3-year observation period than the comparison group. We conclude that early intervention programs involving high-quality group care are not accompanied by substantial increases in health care use.  相似文献   
978.
Richard E. Clark in his widely published comprehensive studies and meta-analyses of the literature on computer assisted instruction (CAI) has decried the lack of carefully controlled research, challenging almost every study which shows the computer-based intervention to result in significant post-test proficiency gains over a non-computer-based intervention. We report on a randomized study in a medical school setting where the usual confounders found by Clark to plague most research, were carefully controlled. PlanAlyzer is a microcomputer-based, self-paced, case-based, event-driven system for medical education which was developed and used in carefully controlled trials in a second year medical school curriculum to test the hypothesis that students with access to the interactive programs could integrate their didactic knowledge more effectively and/or efficiently than with access only to traditional textual “nonintelligent” materials. PlanAlyzer presents cases, elicits and critiques a student's approach to the diagnosis of two common medical disorders: anemias and chest pain. PlanAlyzer uses text, hypertext, images and critiquing theory. Students were randomized, one half becoming the experimental group who received the interactive PlanAlyzer cases in anemia, the other half becoming the controls who received the exact same content material in a text format. Later in each year there was a crossover, the controls becoming the experimentals for a similar intervention with the cardiology PlanAlyzer cases. Preliminary results at the end of the first two full trials shows that the programs have achieved most of the proposed instructional objectives, plus some significant efficiency and economy gains. 96 faculty hours of classroom time were saved by using PlanAlyzer in their place, while maintaining high student achievement. In terms of student proficiency and efficiency, the 328 students in the trials over two years were able to accomplish the project's instructional objectives, and the experimentals accomplished this in 43% less time than the controls, achieving the same level of mastery. However, in spite of these significant efficiency findings, there have been no significant proficiency differences (as measured by current factual and higher order multiple choice post-tests) between the experimental and control groups. Very careful controls were used to avoid what Clark has found to be the most common confounders of CAI research. Accordingly, this research proved Clark's rival hypothesis, that the computer, in itself, does not appear to contribute to proficiency gains, at least as measured by our limited post-testing. Clark's position is that the computer is primarily a vehicle—as is either a pill or a hypodermic needle for delivering a drug. The hypodermic needle can deliver the drug more efficiently than can the pill, (as can the computer deliver the subject matter content more efficiently, as our research indicates), but the same content is delivered. At the same time, we proved our own hypothesis, as far as efficiency gains resulting from the computer are concerned. However, going beyond Clark's research, we may be teaching processes both more effectively and efficiently with the computer (experience in problem-solving or clinical reasoning and pattern recognition) which our current post-tests do not adequately measure. Our on-going research suggests additional inquiry in several areas: better evaluation instruments to measure the clinical reasoning skills PlanAlyzer was designed to teach; the addition of more advanced cases to determine if this might transform efficiency gains of the computer group into proficiency gains; the addition of enhanced graphic decision support tools and other pedagogical enhancements including cognitive feedback to strengthen PlanAlyzer's power to teach complex concepts of medical decision-making.  相似文献   
979.
Many hospitals today have implemented widely disparate information systems on mainframe and mini-computer hardware. The advent of network technology in hospitals has made it possible to access information in these systems. Unfortunately, the user interfaces to applications on these systems are unique and difficult to learn, which makes them unsuitable for use by clinical services. In this paper we describe the development of a Physician's Workstation which integrates information from multiple existing information systems and discuss how the workstation makes it possible to move from the departmental systems of the present to the computer-based medical record system of the future.  相似文献   
980.
OBJECTIVE: To assess the incidence and spectrum of complications associated with central venous catheter (CVC) placement in the critically ill infant. DESIGN: A prospective study of all babies hospitalized in a neonatal intensive care unit (NICU) from January 1989 to December 1989. Potential risk factors associated with infection were evaluated by a case-control comparison. SETTING: Conducted at a university-affiliated, tertiary care community hospital. PATIENTS: Neonates requiring intensive care and a central venous catheter. Controls consisted of noninfected babies. RESULTS: Of 263 critically ill neonates, only 13 (4.9%) required a CVC insertion. Seventeen CVCs were placed in these 13 neonates for a total duration of 600 days (median, 32 days/cannula). Fifteen (88%) of these cannulas had one or more complications during its catheter life including dislodgement or leakage (53%), occlusion or thrombosis (47%), infections (29%), or minor bleeding (12%). Five babies (29%) developed 6 episodes of bloodstream infection including 3 sporadic cases due to Staphylococcus epidermidis and a cluster of fungemia due to Malassezia furfur associated with lipid emulsion therapy. Infants with a CVC-associated infection were a younger gestational age (24 weeks versus 32 weeks, p = .04) and weighed less at birth (580 g versus 1285 g, p = .02). The overall rate of bloodstream infection was one episode per 100 days of catheter use. CONCLUSIONS: CVCs may be lifesaving to a critically ill neonate, but complications occur frequently. Use must be restricted to infants in whom alternate delivery routes of intravenous therapy or support are otherwise unavailable.  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