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   1602679篇
  免费   131535篇
  国内免费   2584篇
耳鼻咽喉   21656篇
儿科学   52948篇
妇产科学   46233篇
基础医学   227867篇
口腔科学   47241篇
临床医学   140976篇
内科学   315023篇
皮肤病学   34100篇
神经病学   130150篇
特种医学   64782篇
外国民族医学   475篇
外科学   243923篇
综合类   39713篇
现状与发展   3篇
一般理论   544篇
预防医学   122919篇
眼科学   36474篇
药学   121304篇
  3篇
中国医学   2977篇
肿瘤学   87487篇
  2018年   14793篇
  2016年   12918篇
  2015年   15048篇
  2014年   20680篇
  2013年   31404篇
  2012年   42628篇
  2011年   44824篇
  2010年   26378篇
  2009年   25356篇
  2008年   43055篇
  2007年   45287篇
  2006年   46090篇
  2005年   44730篇
  2004年   44135篇
  2003年   42240篇
  2002年   41334篇
  2001年   75713篇
  2000年   78343篇
  1999年   66409篇
  1998年   17746篇
  1997年   16337篇
  1996年   16321篇
  1995年   16024篇
  1994年   15074篇
  1993年   14219篇
  1992年   55436篇
  1991年   53796篇
  1990年   52568篇
  1989年   50840篇
  1988年   47228篇
  1987年   46568篇
  1986年   44291篇
  1985年   42855篇
  1984年   32039篇
  1983年   27571篇
  1982年   16147篇
  1981年   14438篇
  1980年   13565篇
  1979年   30465篇
  1978年   21064篇
  1977年   17765篇
  1976年   16695篇
  1975年   17575篇
  1974年   21486篇
  1973年   20673篇
  1972年   18854篇
  1971年   17771篇
  1970年   16291篇
  1969年   15269篇
  1968年   13949篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
There is increasing evidence that the assessment of eosinophilic airway inflammation using induced sputum and measurement of airway hyperresponsiveness provides additional, clinically important information concerning asthma control. The aim of this study was to directly compare the effects of different treatments on these markers in patients with asthma and persistent symptoms, despite the use of low-dose inhaled corticosteroids. A double-blind four-way crossover study was performed, which compared a 1-month treatment with budesonide 400 mug b.i.d., additional formoterol, additional montelukast and placebo in 49 patients with uncontrolled asthma despite budesonide 100 mug b.i.d., with each treatment separated by a 4-week washout period. The change in sputum eosinophil count with formoterol (2.4 to 3.8% change, 0.6-fold reduction, 95% confidence interval (CI) 0.5-0.9) differed significantly from placebo (2.8 to 2.5% change, 1.1-fold reduction, 95% CI 0.7-1.6) and high-dose budesonide (2.7 to 1.6% change, 1.6-fold reduction, 95% CI 1.2-2.2). The effects of montelukast did not differ from placebo. The changes in methacholine airway responsiveness were small and did not differ between treatments. High-dose budesonide had the broadest range of beneficial effects on other outcomes, including symptom scores, morning peak expiratory flow and forced expiratory volume in one second. In conclusion, treatment given in addition to low-dose inhaled corticosteroids results in modest benefits. Formoterol and high-dose budesonide have contrasting effects on eosinophilic airway inflammation.  相似文献   
82.
83.
84.
Summary:  The immune system is capable of recognizing and eliminating an enormous array of pathogens due to the extremely diverse antigen receptor repertoire of T and B lymphocytes. However, the development of lymphocytes bearing receptors with unique specificities requires the generation of programmed double strand breaks (DSBs) coupled with bursts of proliferation, rendering lymphocytes susceptible to mutations contributing to oncogenic transformation. Consequently, mechanisms responsible for monitoring global genomic integrity must be activated during lymphocyte development to limit the oncogenic potential of antigen receptor locus recombination. Mutations in ATM (ataxia-telangiectasia mutated), a kinase that coordinates DSB monitoring and the response to DNA damage, result in impaired T-cell development and predispose to T-cell leukemia. Here, we review recent evidence providing insight into the mechanisms by which ATM promotes normal lymphocyte development and protects from neoplastic transformation.  相似文献   
85.
Abstract: Data from the National Education Longitudinal Study were combined with census data at the zip code level to examine the impact of neighborhood racial and ethnic diversity and consolidated inequality, in addition to individual, family, and school factors, on the likelihood of dropping out of high school. Results indicate that while the effects for diversity and consolidated inequality did not support the stated hypotheses, main effects for family risk and prior academic achievement were significant and in the stated direction. Also, when controlling for individual, family, school, and neighborhood characteristics, African Americans were less likely than White students to drop out of school. Implications for contextual effects research and educational outcomes are discussed.  相似文献   
86.
87.
Introduction Recent reviews found problem gamblers are heterogeneous and recommended subtyping gamblers in treatment studies. Objective Review factors (stage of change, preferred gambling activity, co-occurring disorder, and temporal instability of symptoms) for subtyping by evaluating the evidence for their effects on gambling treatment. Methods Literature review, evidence grading. Results Evidence is limited that any of the reviewed factors affects gambling treatment. Substantial evidence from prospective studies and other evidence from cross-sectional studies and the strong placebo response among pathological gamblers support the temporal instability of gambling symptoms. Conclusions Multiple studies are needed to develop the evidence base needed to subtype gamblers in treatment. Changes in the diagnostic criteria of pathological gambling may be necessary, especially to specify the persistence of gambling-related symptoms.  相似文献   
88.
OBJECTIVE: To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life. METHODS: This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers. RESULTS: In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted. CONCLUSIONS: RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.  相似文献   
89.
90.
BACKGROUND CONTEXT: Substantial variation exists regarding the use of sedation before interventional spine techniques. Patient preference should play an important role in decision making regarding the need for sedation. However, little is known about patients' anxiety levels before spinal injections and their perceptions about the necessity of sedation. PURPOSE: To determine patient perception for need for sedation before epidural steroid injections and zygapophyseal joint injections. STUDY DESIGN/SETTING: Survey of consecutive spinal injection patients in an outpatient spine center. PATIENT SAMPLE: 500 consecutive lumbar, thoracic, and cervical patients receiving spinal injections. OUTCOME MEASURES: A 12-item questionnaire assessing patients' perceived anxiety before to a spinal injection. METHODS: Subjects were given the questionnaire after their spinal injection. Percentages requesting sedation for a first and potential second procedure were assessed. Additionally, anxiety level and pain rating, location of injection, age, sex, and other medication use were analyzed to determine the effect on the request for sedation. RESULTS: 17% of patients questioned requested sedation before an injection, and 28% would request sedation if they were to have a second injection. CONCLUSIONS: Routine sedation before diagnostic and therapeutic injections is not necessary as the majority of patients would not request sedation before the procedure when given the option. However, in some patients sedation is indicated, and all patients would benefit from educational material on sedation before the injection.  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