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   17767篇
  免费   5724篇
  国内免费   38篇
耳鼻咽喉   521篇
儿科学   638篇
妇产科学   773篇
基础医学   110篇
口腔科学   1100篇
临床医学   3633篇
内科学   6577篇
皮肤病学   368篇
神经病学   966篇
特种医学   264篇
外科学   1929篇
综合类   16篇
现状与发展   2篇
预防医学   3489篇
眼科学   359篇
药学   192篇
肿瘤学   2592篇
  2024年   167篇
  2023年   1128篇
  2022年   369篇
  2021年   671篇
  2020年   1234篇
  2019年   415篇
  2018年   1175篇
  2017年   1262篇
  2016年   1507篇
  2015年   1440篇
  2014年   2035篇
  2013年   2203篇
  2012年   675篇
  2011年   588篇
  2010年   1158篇
  2009年   1604篇
  2008年   601篇
  2007年   375篇
  2006年   679篇
  2005年   294篇
  2004年   231篇
  2003年   157篇
  2002年   142篇
  2001年   299篇
  2000年   240篇
  1999年   265篇
  1998年   358篇
  1997年   287篇
  1996年   273篇
  1995年   232篇
  1994年   183篇
  1993年   134篇
  1992年   129篇
  1991年   113篇
  1990年   129篇
  1989年   153篇
  1988年   100篇
  1987年   53篇
  1986年   75篇
  1985年   58篇
  1984年   52篇
  1983年   53篇
  1982年   29篇
  1981年   18篇
  1980年   43篇
  1978年   17篇
  1977年   19篇
  1975年   18篇
  1973年   19篇
  1972年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
BACKGROUND: Coupled pacing (CP), which consists of delivering a premature electrical stimulation to the heart after the effective refractory period of ventricular activation, is a novel method for controlling ventricular rate during atrial fibrillation (AF). It also has been established that CP improves pump function by enhancing external cardiac work and myocardial efficiency. OBJECTIVE: The purpose of the present study was to determine if two time delays for CP (short and long) would result in similar improvements in ventricular function. METHODS: In a canine model, we applied CP at two time delays (CP-S and CP-L) during two stages: sinus rhythm (SR) and acute AF. The cardiac responses to CP during SR served as the nontachycardic and nondepressed control. During both rhythms, we shortened the coupling interval until we obtained maximal contractility, designated CP-S. Next, we increased the delay until we started to see a measurable secondary contraction (left ventricular pressure development of approximately 20 mmHg). These longer delays were designated CP-L. RESULTS: Our results showed that the ventricular rate of intrinsic activation (VRIA) remained decreased despite prolongation of the time delay of CP during both AF and SR. Also, both delays of CP increased left ventricular systolic pressure (LVSP) and dLVP/dt, which are indices of myocardial contractility. In contrast, CP increased external cardiac work only during AF. Prolonging this time delay did not markedly decrease the improvement in external cardiac work. Myocardial O(2) consumption (MVO(2)) did not significantly change as the result of CP during either SR or AF. Finally, myocardial efficiency improved during AF as the result of CP at both time delays. CONCLUSIONS: In conclusion, shorter time delays for CP increased contractile strength during both SR and AF. However, extending the time delay of CP had minimal effects on diminishing the improved ventricular pump function and energetics that resulted from CP during AF. Thus, the maximal enhancement of myocardial contractility via CP-S was not needed to maintain the improved ventricular function during acute AF when CP is applied.  相似文献   
52.
53.
This study was undertaken to examine the beliefs and practices of dietitians in relation to cancer risk reduction through nutrition. Respondents to the national survey (N=384, 70 percent) were similar in demographic, educational, and professional characteristics to the American Dietetic Association census data. They reported a strong preventive health orientation: mean performance on 10 preventive health behaviors was 77.5 on a 100 point scale. Half (53 percent) believed cancer would be serious if they developed it, 47 percent believed it was not likely that they would. About 20 percent of the respondents felt that the role of nutrition in cancer etiology was unclear. Dietitians believed strong research support existed for increasing whole grains, fruits and vegetables, and fiber to reduce cancer risk but that little evidence supported use of dietary supplements. Dietitians regularly practiced 75 percent of nutrition recommendations they believed to be effective in reducing cancer risk. Beliefs about the effectiveness of a recommendation accounted for the largest percentage of variance on nutritional practices. While dietitians reported many preventive health practices, including following nutrition recommendations, they seemed to be doing so for reasons other than preventing cancer.Nancie S. Merlino is Assistant Professor, Nutrition and Food Science, Wayne State University, Detroit, MI 48202 and James H. Price, Professor of Health Promotion, Department of Health Promotion, University of Toledo, Toledo, OH 43606.Acknowledgement goes to Stephen Jurs, PhD; Fredrick Andres, PhD; and John Kish, PhD for assistance in design and analysis.  相似文献   
54.
TOPIC. Nursing assessment of altered sexuality.
PURPOSE. To review salient factors affecting assessment and objective measures available for use in assessment.
SOURCE. Literature specific to nursing assessment of sexuality and to instruments measuring altered sexuality.
CONCLUSIONS. Many standards of care include the assessment of sexuality, and nurses believe it to be an important aspect of care. However, the assessment of altered sexuality does not often occur in actual practice. The use of an objective measure of sexuality is recommended for both initial and on-going assessments in acute-care and community-based settings.  相似文献   
55.
56.
Little is known about oral health care behaviors of community-dwelling, cognitively impaired elderly (CIE) persons. Few studies have been conducted regarding the actual provision of oral care for CIE persons or the attitudes and concerns about oral health among their caregivers. The CIE person's ability to perform self-care decreases over time, and the role of the caregiver in daily oral care becomes increasingly important. The purpose of this pilot study was to explore the attitudes toward oral health and identify related concerns among caregivers who care for community-dwelling CIE persons. Caregivers were surveyed by means of a self-administered, mailed questionnaire. To maintain confidentiality, an intermediary was used for recruitment and data collection. Overall, 148 caregivers were invited by an intermediary to participate in the survey; only 21 (14%) consented to participate and returned the questionnaire. This paper discusses some of the numerous methodological challenges identified when an attempt was made to survey caregivers' attitudes toward and barriers to providing oral care for a dependent CIE.  相似文献   
57.
There have been few reports of relative rates of provision of dental health services in rural and urban settings, a comparative measure of access to care in these populations. One part of a statewide survey of active North Carolina general dentists (n=959, response rate=47%) was designed to quantify provision of prosthetic services. To determine contrasting rural and urban rates, responses were analyzed according to dentists'self-report of practice city size using analysis of covariance with percent of insured patients in the practice as the covariate. Mean per-patient-visit rates for crowns, fixed partial dentures, removable partial dentures, and extractions, as well as the distributions of treatment following tooth extraction, differed by city size, with practitioners in the smallest cities reporting treatment distributions reflecting more frequent loss of teeth and less frequent replacement. These differences in patterns of prosthetic care echo the limited existing information describing oral health status, provider supply, and receipt of care, all of which suggest that differential levels of access to care exist and lead to differences in oral health outcomes.  相似文献   
58.
The elderly (age >65 years) are more vulnerable to side-effects induced by non-steroidal anti-inflammatory drugs (NSAIDs). We therefore performed a double-blind comparative study of ketoprofen SR and sulindac in patients with active rheumatoid arthritis, 65 years of age or older. Sulindac was chosen because of its possible renal sparing effects, and ketoprofen SR because of its short half life and sustained release delivery system. Eighty patients were entered. More patients withdrew from the study due to side-effects in the sulindac group; both treatment groups had a high incidence of side-effects during this study and during previous exposure to other NSAIDs, demonstrating that the elderly are susceptible to side-effects from NSAIDs.  相似文献   
59.
Objective The effects of a computer-assisted instruction (CAI) tutorial program on learning clinical reasoning skills were compared in undergraduate dietetics students.Design A drill-and-practice program to control for time on task, a tutorial program, and a simulation program, as the test vehicle, were developed. The tutorial and simulation programs presented data on a patient with cardiovascular disease.Setting Subjects were tested in 30 undergraduate dietetics programs.Subjects Participants were 413 undergraduate diet therapy students enrolled in a coordinated program in dietetics (CPD) or a didactic program in dietetics (DPD).Intervention After completion of lectures on cardiovascular disease, subjects were given the drill-and-practice program plus a simulation test (group 1), the tutorial plus a simulation test (group 2), or the simulation test only (group 3).Main outcome measures Scores on the simulation test were compared. Variables included type of CAI, dietetics program, year in school, computer experience, and experience using a medical chart. Mastery of objectives related to lower- and higher-level clinical reasoning skills introduced in the tutorial program was compared.Statistical analysis One-way analysis of variance and Student-Newman Keuls tests were conducted to determine any differences among the three groups. Reliability was determined using the Kuder-Richardson Formula 20.Results The reliability coefficient of the simulation test was 0.93. Group 2 scored higher on the simulation test than group 1 or group 3. As a group, the CPD students scored higher than the DPD students. When CPD and DPD students were divided into the three experimental groups, there was no significant difference between the CPD and DPD student simulation scores. Group 2 mastered all objectives for lower-level reasoning skills and the higher-level decision-making objective better than groups 1 and 3.Applications/conclusions A computer tutorial program enhanced clinical reasoning skills in undergraduate dietetics students. This type of program could be used to supplement many topics taught in diet therapy and provide DPD students with experiential learning before their clinical intern practicums. J Am Diet Assoc. 1995; 95:868–873.  相似文献   
60.
Younger women smoke at disproportionately higher rates than other women and their smoking has a major impact on the health of their young children. To address this problem, a smoking cessation intervention combining minimal advice and assistance from a community health nurse and a tailored self-help guide was developed for low-income women with young children. The program evaluation results reported here were gathered from women using publicly funded pediatric services in four agencies with 32 clinic sites in central and eastern Pennsylvania. Unlike volunteers in formal cessation programs, the women varied widely in their readiness to quit smoking. Follow-up data were obtained from 1,230 female smokers, aged 18 to 39, after receiving brief, individualized smoking cessation advice and encouragement to read the self-help guide. One year later, 12.5 percent reported quitting smoking, and 20.2 percent reported having made a serious quit attempt that lasted at least 7 days. These results suggest that, even among smokers with low socioeconomic status and wide variation in their readiness to quit, minimal intervention programs requiring modest resources can promote cessation.This work was funded under contracts from the Cancer Control Program, Pennsylvania Department of Health (SPC-883141 and SPC-979425). The Quitting Times STOP IT quit smoking protocol was adapted from the Smoking Cessation Project, Maternal and Child Health, Massachusetts Department of Public Health. The authors also wish to express appreciation to the staff of the Division of Population Science, Fox Chase Cancer Center for their contributions to this project and especially those of Chris Jepson, Eunice King, C. Tracy Orleans, and Marjorie Utt.  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