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   27740篇
  免费   5904篇
  国内免费   81篇
耳鼻咽喉   120篇
儿科学   845篇
妇产科学   1859篇
基础医学   1512篇
口腔科学   250篇
临床医学   16299篇
内科学   3727篇
皮肤病学   301篇
神经病学   1515篇
特种医学   353篇
外科学   1808篇
综合类   264篇
一般理论   21篇
预防医学   2777篇
眼科学   181篇
药学   674篇
中国医学   11篇
肿瘤学   1208篇
  2024年   66篇
  2023年   892篇
  2022年   272篇
  2021年   633篇
  2020年   866篇
  2019年   566篇
  2018年   1448篇
  2017年   1608篇
  2016年   1706篇
  2015年   1797篇
  2014年   1879篇
  2013年   2223篇
  2012年   1154篇
  2011年   1441篇
  2010年   1435篇
  2009年   1619篇
  2008年   1124篇
  2007年   1092篇
  2006年   1016篇
  2005年   950篇
  2004年   856篇
  2003年   707篇
  2002年   696篇
  2001年   520篇
  2000年   323篇
  1999年   479篇
  1998年   643篇
  1997年   724篇
  1996年   692篇
  1995年   607篇
  1994年   449篇
  1993年   375篇
  1992年   289篇
  1991年   269篇
  1990年   261篇
  1989年   201篇
  1988年   148篇
  1987年   152篇
  1986年   149篇
  1985年   177篇
  1984年   139篇
  1983年   126篇
  1982年   110篇
  1981年   106篇
  1980年   65篇
  1979年   90篇
  1978年   68篇
  1977年   72篇
  1976年   71篇
  1972年   91篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
This study attempted to identify factors associated with mortality among human immunodeficiency virus (HIV)-infected adults starting a protease inhibitor (PI)-containing therapy. Among 1155 patients consecutively enrolled in the APROCO study between May 1997 and June 1998, clinical characteristics were as follows: median age, 36 years; median baseline CD4 cell count, 288 cells/mm(3); and median baseline plasma HIV RNA load, 4.4 log(10) copies/mL. After a median follow-up of 27 months, 48 deaths had occurred, of which 44% were related to acquired immune deficiency syndrome. The mortality rate was 2.9% at 12 months. When both data at baseline and data at 4 months after the start of PI therapy were considered, factors independently associated with mortality were (Cox model) low baseline plasma creatinine level, low school education level, low CD4 cell count at 4 months, low hemoglobin level, and elevated hepatic transaminase levels. Thus, social context plus clinical and biologic data, including the 4-month response to treatment, must be considered in treatment of HIV-infected patients.  相似文献   
993.
OBJECTIVE: To evaluate whether hospital volume and surgeon volume of total hip replacements (THRs) are associated with patient-reported functional status and satisfaction with surgery 3 years postoperatively. METHODS: We performed a population-based cohort study of a stratified random sample of Medicare beneficiaries who underwent elective primary or revision THR in Ohio, Pennsylvania, or Colorado in 1995. The primary outcomes were the self-reported Harris hip score and a validated scale measuring satisfaction with the results of surgery. Both outcomes were assessed 3 years postoperatively. Hospital volume was defined as the aggregate number of elective primary and revision THRs performed on Medicare beneficiaries in the hospital in 1995. High-volume hospitals were defined as those in which >100 such procedures are performed annually, and low-volume centers were defined as those in which 12 procedures per year. CONCLUSION: Hospital volume and surgeon volume have little effect on 3-year functional outcome following THR, after adjusting for patient sociodemographic and select clinical characteristics. However, satisfaction with primary THR is greater among patients who underwent surgery in high-volume centers, and satisfaction with revisions is greater among patients whose operations were performed by higher-volume surgeons. Referring clinicians should incorporate these findings into their discussion of referral choices with patients considering THR. Conclusions regarding the effect of volume on longevity of the implants must await longer-term followup studies. Finally, further research is warranted to better understand the association between hospital and surgeon procedure volume and patient satisfaction with surgery.  相似文献   
994.
995.

Background

Cardiovagal baroreflex gain (cBRG) reflects an individual's ability to buffer swings in blood pressure. It is not well understood how this mechanism is influenced by physical activity in pregnancy. Because pregnant women tend to engage in low levels of moderate-to-vigorous physical activity (MVPA) and high levels of sedentary behaviour, we sought to determine the influence of MVPA and sedentary behaviour on cBRG and mean arterial pressure (MAP) in pregnancy.

Methods

Fifty-eight third trimester (31.9 ± 3.0 weeks) normotensive pregnant women (31.2 ± 2.8 years) were tested. Heart rate (electrocardiogram) and blood pressure (systolic blood pressure and MAP; finger photoplethysmography) were collected on a beat-by-beat basis, and averaged over 3 minutes of rest. Spontaneous cBRG was calculated as the slope of the relationship between fluctuations in systolic blood pressure and heart rate. Objective measures of MVPA and sedentary behaviour were collected over a 7-day period using an ActiGraph accelerometer (model wGTX3-BT; ActiGraph LLC, Pensacola, FL).

Results

Participants spent 67.5 ± 7.9% of waking hours engaged in sedentary behaviour, and performed 68.6 ± 91.9 minutes of MVPA per week. Sedentary behaviour was not related to cBRG (r = ?0.035; P = 0.793) or MAP (r = ?0.033; P = 0.803). However, MVPA was positively associated with cBRG (r = 0.315; P = 0.016), but not MAP (r = ?0.115; P = 0.389). The association between MVPA and cBRG remained significant after controlling for age, pre-pregnancy body mass index, gestational age, and wear time (r = 0.338; P = 0.013), indicating that women who engaged in greater amounts of MVPA showed increased cBRG.

Conclusions

Our data suggest that increased MVPA, but not necessarily reduced sedentary behaviour, might be beneficial for reflex control of blood pressure during pregnancy.  相似文献   
996.
This report describes different imaging techniques of the esophagus in four patients during radiofrequency catheter ablation of atrial fibrillation in the left atrium. A novel use of a mixture of barium cream and gadolinium diglutamate allowed esophageal imaging during magnetic resonance angiography of the left atrium and pulmonary veins. Barium cream used during computer tomography angiographic imaging of the left atrium and pulmonary veins allowed esophageal imaging. The esophagus was also imaged with an electroanatomic mapping system. Esophageal and left atrial imaging helped to avoid catheter ablation in left atrial tissue overlapping the esophagus.  相似文献   
997.
998.
999.
1000.
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