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   72430篇
  免费   4896篇
  国内免费   223篇
耳鼻咽喉   530篇
儿科学   2129篇
妇产科学   1169篇
基础医学   9891篇
口腔科学   1514篇
临床医学   7572篇
内科学   15393篇
皮肤病学   983篇
神经病学   6827篇
特种医学   2539篇
外国民族医学   1篇
外科学   10059篇
综合类   890篇
一般理论   72篇
预防医学   6410篇
眼科学   1740篇
药学   4936篇
  1篇
中国医学   81篇
肿瘤学   4812篇
  2023年   377篇
  2022年   522篇
  2021年   1404篇
  2020年   840篇
  2019年   1364篇
  2018年   1665篇
  2017年   1238篇
  2016年   1357篇
  2015年   1588篇
  2014年   2370篇
  2013年   3216篇
  2012年   5238篇
  2011年   5371篇
  2010年   3011篇
  2009年   2681篇
  2008年   4878篇
  2007年   5352篇
  2006年   5244篇
  2005年   4976篇
  2004年   4768篇
  2003年   4312篇
  2002年   4211篇
  2001年   579篇
  2000年   406篇
  1999年   646篇
  1998年   945篇
  1997年   793篇
  1996年   691篇
  1995年   648篇
  1994年   523篇
  1993年   502篇
  1992年   356篇
  1991年   314篇
  1990年   266篇
  1989年   277篇
  1988年   296篇
  1987年   241篇
  1986年   256篇
  1985年   279篇
  1984年   328篇
  1983年   346篇
  1982年   410篇
  1981年   393篇
  1980年   355篇
  1979年   200篇
  1978年   244篇
  1977年   217篇
  1976年   151篇
  1975年   116篇
  1974年   105篇
排序方式: 共有10000条查询结果,搜索用时 33 毫秒
991.
992.
BackgroundAmphetamines have been reported to cause myocardial infarct, cerebral hemorrhage, aortic dissection, hypertension, vasculitis, aneurysms, and, occasionally, death from direct toxicity. To date, there have been no reports of coronary intimal hyperplasia in an amphetamine user.MethodsA 29-year-old male was found collapsed after jogging. He had been taking amphetamines for 11 years for attention deficit/hyperactivity disorder. Past medical history was positive for mild hypertension and migraine headaches. He underwent a complete autopsy and drug screen.ResultsAt gross autopsy his left anterior descending (LAD) coronary artery was occluded and he had an old myocardial infarct in the anterior wall of the left ventricle. Microscopic findings included occlusive intimal hyperplasia (positive for smooth muscle actin) in the LAD and an old left ventricular anterior wall infarct surrounded by acute infarct.ConclusionIn addition to other reported adverse effects, amphetamines can also cause occlusive intimal hyperplasia of the coronary arteries.  相似文献   
993.
994.
995.
Recent advances in technology have given rise to novel methods of delivering support to smokers wanting to quit. Mobile phone text messaging permits the delivery of quitting advice at any time, with little effort and at minimal cost. We examined smokers' attitudes toward text messaging as a tool to facilitate smoking cessation as well as preferences for message content and text delivery. Six focus groups were conducted from a total of 24 participants, with additional information obtained via paper questionnaire. Interaction with the text messaging system, tailoring message content and delivery, highlighting the positive effects of quitting, and offering encouragement by text were considered important features of a text support program. Future text messaging interventions may benefit from these findings.  相似文献   
996.
This research explores the feasibility of using motor electrical feedback to estimate temperature rise during a surgical bone grinding procedure. High-speed bone grinding is often used during skull base neurosurgery to remove cranial bone and approach skull base tumors through the nasal corridor. Grinding-induced heat could propagate and potentially injure surrounding nerves and arteries, and therefore, predicting the temperature in the grinding region would benefit neurosurgeons during the operation. High-speed electric motors are controlled by pulse-width-modulation (PWM) to alter the current input and thus maintain the rotational speed. Assuming full mechanical to thermal power conversion in the grinding process, PWM can be used as feedback for heat generation and temperature prediction. In this study, the conversion model was established from experiments under a variety of grinding conditions and an inverse heat transfer method to determine heat flux. Given a constant rotational speed, the heat conversion was represented by a linear function, and could predict temperature from the experimental data with less than 20% errors. Such results support the advance of this technology for practical application.  相似文献   
997.

Background

Most of the world’s women living with human immunodeficiency virus (HIV) reside in sub-Saharan Africa. Although efforts to reduce mother-to-child transmission are underway, obtaining complete and accurate data from rural clinical sites to track progress presents a major challenge.

Objective

To describe the acceptability and feasibility of mobile phones as a tool for clinic-based face-to-face data collection with pregnant women living with HIV in South Africa.

Methods

As part of a larger clinic-based trial, 16 interviewers were trained to conduct mobile phone–assisted personal interviews (MPAPI). These interviewers (participant group 1) completed the same short questionnaire based on items from the Technology Acceptance Model at 3 different time points. Questions were asked before training, after training, and 3 months after deployment to clinic facilities. In addition, before the start of the primary intervention trial in which this substudy was undertaken, 12 mothers living with HIV (MLH) took part in a focus group discussion exploring the acceptability of MPAPI (participant group 2). Finally, a sample of MLH (n=512) enrolled in the primary trial were asked to assess their experience of being interviewed by MPAPI (participant group 3).

Results

Acceptability of the method was found to be high among the 16 interviewers in group 1. Perceived usefulness was reported to be slightly higher than perceived ease of use across the 3 time points. After 3 months of field use, interviewer perceptions of both perceived ease of use and perceived usefulness were found to be higher than before training. The feasibility of conducting MPAPI interviews in this setting was found to be high. Network coverage was available in all clinics and hardware, software, cost, and secure transmission to the data center presented no significant challenges over the 21-month period. For the 12 MHL participants in group 2, anxiety about the multimedia capabilities of the phone was evident. Their concern centered on the possibility that their privacy may be invaded by interviewers using the mobile phone camera to photograph them. For participants in group 3, having the interviewer sit beside vs across from the interviewee during the MPAPI interview was received positively by 94.7% of MHL. Privacy (6.3%) and confidentiality (5.3%) concerns were low for group 3 MHL.

Conclusions

Mobile phones were found both to be acceptable and feasible in the collection of maternal and child health data from women living with HIV in South Africa.

Trial Registration

Clinicaltrials.gov NCT00972699; http://clinicaltrials.gov/ct2/show/NCT00972699 (Archived by WebCite at http://clinicaltrials.gov/ct2/show/NCT00972699)  相似文献   
998.
999.
1000.
This state-of-the-art review presents the latest evidence and the current status of autogenous soft tissue grafting for soft tissue augmentation and recession coverage at teeth and dental implant sites. The indications and predictability of the free gingival graft and connective tissue graft (CTG) techniques are highlighted, together with their expected clinical and esthetic outcomes. CTGs can be harvested from the maxillary tuberosity or from palate with different approaches that can have an impact on graft quality and patient morbidity. The influence of CTGs on soft tissue thickness and keratinized tissue width are also discussed.  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