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   45734篇
  免费   4352篇
  国内免费   1723篇
耳鼻咽喉   304篇
儿科学   847篇
妇产科学   1337篇
基础医学   9493篇
口腔科学   1688篇
临床医学   3696篇
内科学   4986篇
皮肤病学   1253篇
神经病学   2874篇
特种医学   993篇
外国民族医学   20篇
外科学   3135篇
综合类   6965篇
现状与发展   13篇
一般理论   12篇
预防医学   3286篇
眼科学   948篇
药学   5514篇
  19篇
中国医学   1143篇
肿瘤学   3283篇
  2023年   474篇
  2022年   601篇
  2021年   1350篇
  2020年   1292篇
  2019年   1344篇
  2018年   1307篇
  2017年   1439篇
  2016年   1518篇
  2015年   1556篇
  2014年   2456篇
  2013年   3414篇
  2012年   2453篇
  2011年   2698篇
  2010年   2314篇
  2009年   2151篇
  2008年   2088篇
  2007年   2251篇
  2006年   2118篇
  2005年   1931篇
  2004年   1782篇
  2003年   1618篇
  2002年   1379篇
  2001年   1202篇
  2000年   1031篇
  1999年   873篇
  1998年   743篇
  1997年   700篇
  1996年   699篇
  1995年   777篇
  1994年   675篇
  1993年   645篇
  1992年   570篇
  1991年   513篇
  1990年   398篇
  1989年   408篇
  1988年   343篇
  1987年   263篇
  1986年   249篇
  1985年   424篇
  1984年   364篇
  1983年   250篇
  1982年   280篇
  1981年   221篇
  1980年   180篇
  1979年   106篇
  1978年   109篇
  1977年   66篇
  1976年   62篇
  1975年   33篇
  1974年   27篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
991.
背景 目前我国流感疫苗覆盖率较低,一旦暴发将加剧医疗压力。目的 总结预防和控制流感在养老院暴发的最佳证据,以强化养老院管理者以及工作人员对流感的重视。方法 计算机检索万方数据知识服务平台(Wanfang Data)、维普网(VIP)、中国知网(CNKI)、中国生物医学文献数据库(CBM)、中华人民共和国民政部官网、Cochrane Library、PubMed、Medline、Joanna Briggs Institute(JBI)循证卫生保健中心图书馆、Up to Date、Ovid数据库及美国疾病控制与预防中心(CDC)官网关于预防和控制养老院流感暴发的临床指南、系统评价、专家共识、队列研究、随机对照试验、横断面研究。检索时间为建库至2020-02-12。分别采用AGREE Ⅱ、AMSTAR、JBI循证卫生保健中心专家共识评价标准(2017年澳大利亚版本)、2016版JBI循证卫生保健中心队列研究评价标准、Jadad评分量表、2017版JBI循证卫生保健中心横断面研究质量评价工具进行质量评价。最后采用2014年澳大利亚版本JBI循证卫生保健中心证据分级及证据推荐级别系统进行证据汇总、评价和等级划分。结果 本研究最终纳入文献17篇,其中临床指南5篇、系统评价2篇、专家共识3篇、队列研究2篇、随机对照试验4篇、横断面研究1篇。5篇临床指南中各领域≥60%的数目为6的有3篇,推荐级别为A级的有5篇。2篇系统评价的质量评价结果均为准予纳入。3篇专家共识的质量评价结果均为准予纳入。2篇队列研究的质量评价结果显示文献质量均较高,允许纳入。4篇随机对照试验的质量评价结果均为准予纳入。1篇横断面研究的质量评价结果为文献属于高质量文献,允许纳入。证据汇总最终得出27条预防和控制养老院流感暴发的最佳证据,包含环境、人员管理、预防措施以及疫苗接种影响因素4个方面。结论 总结和分析国内外养老院流感暴发预防与控制的相关文献得出接种流感疫苗仍是目前控制流感的最佳方法,养老院管理者及工作人员应当提高对流感重视程度,优化流感预防管理模式。  相似文献   
992.
Ribosome-inactivating proteins (RIPs) are rRNA N-glycosylases from plants (EC 3.2.2.22) that inactivate ribosomes thus inhibiting protein synthesis. The antiviral properties of RIPs have been investigated for more than four decades. However, interest in these proteins is rising due to the emergence of infectious diseases caused by new viruses and the difficulty in treating viral infections. On the other hand, there is a growing need to control crop diseases without resorting to the use of phytosanitary products which are very harmful to the environment and in this respect, RIPs have been shown as a promising tool that can be used to obtain transgenic plants resistant to viruses. The way in which RIPs exert their antiviral effect continues to be the subject of intense research and several mechanisms of action have been proposed. The purpose of this review is to examine the research studies that deal with this matter, placing special emphasis on the most recent findings.  相似文献   
993.
Until recently, awareness of the sexually transmitted infection human papillomavirus—the virus that causes cervical cancer—was relatively low. The purpose of this study was to identify factors associated with human papillomavirus knowledge now that human papillomavirus vaccines have become widely available. Young adult women (n = 739; aged 18–26 years) attending Florida State University who had not yet initiated human papillomavirus vaccination completed a survey between March–August 2009. The survey assessed human papillomavirus awareness, human papillomavirus knowledge, demographics, socio-political variables, sexual history, and health history variables. Over 97% of participants were aware of human papillomavirus prior to study enrollment; however, knowledge of human papillomavirus was only moderate. A multivariate regression analysis examining factors related to human papillomavirus knowledge revealed five independent correlates: Latina ethnicity, premarital sex values, number of lifetime sexual partners, history of cervical dysplasia, and HIV testing. These variables accounted for 14% of the variance in human papillomavirus knowledge. Less knowledge was observed for Latinas and women opposed to premarital sex. Greater knowledge was observed for women who had been tested for HIV and women with more sexual partners or a history of cervical dysplasia. These findings can inform future human papillomavirus vaccination campaigns and may be particularly useful in developing interventions for individuals with the largest deficits in human papillomavirus knowledge.  相似文献   
994.
Despite a pressing need for adolescent HIV research in sub-Saharan Africa, ethical guidance for conducting research among minor adolescents is lacking. One ethical issue is the degree to which parents should be involved in the research process. The existing discourse is predominantly speculative and focuses on negative consequences of parental involvement. We use empirical data to describe the perspectives of Kenyan adolescents on parental involvement in consent and disclosure of HIV test results within a research study context. We conducted two rounds of focus group discussions with 40 adolescents in western Kenya to ask about minor adolescent participation in HIV research. We analysed data using codes and matrices. Kenyan adolescents were largely in favour of parental involvement during the research process. Half felt adolescent minors should solicit parental consent to participate, and nearly all said parents should learn the HIV test results of adolescent minors in order to provide necessary support. From their perspective, involvement of parents in research extends beyond obtaining their consent to providing essential support for youth, regardless of HIV status, both during and beyond the research study. Ethical guidelines that prioritise adolescent autonomy in research must consider reasons to involve parents considered important by adolescents themselves, particularly in low-resource settings.  相似文献   
995.
Vγ9Vδ2 T cells have the ability to produce inflammatory cytokines involved in protective immunity against intracellular pathogens and tumours and to display strong cytolytic as well as bactericidal activities. This suggests a direct involvement of Vγ9Vδ2 T lymphocytes in immune control of cancer and infections. These observations have recently aided development of novel immunotherapeutic approaches aimed at Vγ9Vδ2 T cell activation. Nitrogen-containing bisphosphonates (N-BPs) play a crucial role in Vγ9Vδ2 T lymphocyte activation and in the acquisition of effector functions. The preliminary results of these innovative strategies are encouraging. Moreover, compelling evidence in the literature supports the hypothesis that the antitumour effect of bisphosphonates is exerted through direct as well as indirect mechanisms. An additional and not yet well explored mechanism by which N-BPs may display antineoplastic effect is related to their immunomodulatory properties. It is fascinating that N-BPs influence the immune system in various but interrelated ways, being able to enhance the innate and to promote the adaptive immune responses. For all these reasons, Vγ9Vδ2 T lymphocytes represent a particularly interesting target for immunotherapeutic protocols based on N-BP administration. All these unexpected effects of N-BPs on the immune system have opened new and intriguing possibilities of therapeutic use for these drugs.  相似文献   
996.
This article provides an overview of the major findings of psychotherapy research and discusses the possible implications of these findings for substance user treatment researchers and practitioners. While the centrality of relationship for human change processes was historically understood, twentieth century research tended to see relationship and person variables as secondary to operationalized “mechanisms of action” unique to particular psychotherapies. Interestingly, recent meta-analytic investigations have uncovered the weakness of randomized controlled trials (RCT) comparison investigations that have, until recently, represented the “gold standard” for the field. There has been a resurgent interest in the “common factors” that appear to be important across many effective psychotherapies. In addition, psychiatric anthropologists have contributed important information about the problems of client noncompliance with mental health treatment that parallel quantitative investigations. Substance misuse researchers have also found that client characteristics, especially clients' readiness to engage treatment, are important to investigate. The importance of the “therapeutic alliance” and the characteristics of clients and clinicians have become central areas for study, rather than variables to be controlled or excluded. Emphasis on these factors may represent the future for research in psychotherapy and substance user treatment, especially if researchers and community practitioners can join together to overcome methodological feasibility and dissemination problems that plague effectiveness research. However, the continued attractiveness of comparative studies and treatment efficacy studies may represent longstanding epistemological assumptions and responses to economic incentives that will be difficult to challenge.  相似文献   
997.
We studied the secretion of somatostatin and HO and the release of vasoactive intestinal polypeptide (VIP) and gastrin-releasing peptide (GRP) from isolated, vascularly perfused, porcine non-antral stomach. Electric vagus stimulation increased acid secretion and the release of VIP and GRP and inhibited somatostatin secretion as determined in the venous effluent. Atropine abolished the HC1 response and reversed the somatostatin inhibition to a three-fold increase, whereas GRP and VIP responses were unchanged. Both intra-arterial carbachol (10′6M) and GRP (10′8M) increased acid secretion and inhibited somatostatin secretion. VIP (10_8M) increased somatostatin secretion and had no effect on acid secretion. By immunohistochemistry, somatostatin was localized to both open-type and closed-type cells equally spread in the various parts of the gastric glands without particular relation to the parietal cells. Numerous GRP- and VIP-immunoreactive nerve fibers were seen between the glands. It is concluded that the fundic and antral secretion of somatostatin, investigated in a previous study, are differently regulated. The relation of fundic somatostatin release to acid secretion seems to be complex.  相似文献   
998.
The microbial communities found in the mammalian large intestine and rumen efficiently degrade many recalcitrant substrates that are resistant to the host’s digestive enzymes. These communities are known from molecular profiling to be highly diverse at the species and strain level, but it may be that only certain specialized organisms (“keystone species”) have the ability to initiate degradation of such substrates, thus releasing energy on which the rest of the community depends. We have recently reported that Ruminococcus bromii has a superior ability to degrade certain forms of particulate resistant starch (RS) when compared with other highly abundant species of amylolytic bacteria found in the human colon and have presented evidence that this bacterium provides an example of a keystone species within the microbial community with respect to RS fermentation. The concept of keystone species can be equally relevant to other activities, e.g., those involved in stabilizing the community.  相似文献   
999.
Background: The integrated central actions of hormones secreted from pancreatic islets, the gut and adipocytes regulate both energy homeostasis and body weight. Dysregulation in these neurohormonal pathways probably contributes to pathogenesis of obesity and type 2 diabetes. Objective: To examine hormone-based therapies targeting these interrelated pathways as potential treatments for obesity and diabetes. Methods: Preclinical and clinical data on therapies based on hormones secreted from the pancreas (glucagon, insulin, amylin and pancreatic polypeptide), gut (glucagon-like peptide-1, glucose dependent insulinotropic polypeptide, cholecystokinin and peptide YY) and adipose tissue (leptin and adiponectin) as potential treatments for diabetes and obesity are reviewed. Results/conclusions: In diabetes, hormone-based treatments have translated into new clinical platforms including insulin analogs, the GLP-1-like peptide receptor agonist exenatide and amylinomimetic pramlintide, which due to their complex interplay and the progressive nature of diabetes, can be utilized in different settings. Various peptide hormones and agonists/antagonists are currently under investigation as new approaches to treatment of obesity and diabetes.  相似文献   
1000.
We report a patient with barbiturate intoxication due to surreptitious ingestion of barbital buffer from a clinical laboratory. Although detected in the urine toxicology screening test using an immunologic technique, this agent was not recognized in the more specific serum analysis done by gas-liquid chromatography. Barbital buffer is an effective long-acting sedative-hypnotic and is widely available from the laboratory shelf. It may not be reported by very specific analytical methods.  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