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   1326篇
  免费   75篇
  国内免费   29篇
耳鼻咽喉   7篇
儿科学   36篇
妇产科学   69篇
基础医学   142篇
口腔科学   25篇
临床医学   157篇
内科学   226篇
皮肤病学   26篇
神经病学   69篇
特种医学   179篇
外科学   101篇
综合类   130篇
预防医学   101篇
眼科学   1篇
药学   99篇
  1篇
中国医学   2篇
肿瘤学   59篇
  2021年   18篇
  2020年   12篇
  2018年   17篇
  2017年   14篇
  2016年   9篇
  2015年   13篇
  2014年   20篇
  2013年   39篇
  2012年   51篇
  2011年   42篇
  2010年   43篇
  2009年   42篇
  2008年   56篇
  2007年   57篇
  2006年   40篇
  2005年   45篇
  2004年   45篇
  2003年   32篇
  2002年   34篇
  2001年   34篇
  2000年   36篇
  1999年   35篇
  1998年   52篇
  1997年   45篇
  1996年   50篇
  1995年   29篇
  1994年   25篇
  1993年   23篇
  1992年   22篇
  1991年   21篇
  1990年   22篇
  1989年   31篇
  1988年   34篇
  1987年   21篇
  1986年   31篇
  1985年   31篇
  1984年   11篇
  1983年   12篇
  1982年   18篇
  1981年   13篇
  1980年   16篇
  1979年   8篇
  1978年   11篇
  1977年   11篇
  1976年   14篇
  1975年   13篇
  1970年   9篇
  1967年   7篇
  1942年   13篇
  1941年   20篇
排序方式: 共有1430条查询结果,搜索用时 15 毫秒
21.
22.
AIDS and Behavior - Evidence-based adherence counseling interventions must be delivered with fidelity to ensure that their effectiveness is retained, but little is known regarding how counselors in...  相似文献   
23.
Mexico has long been recognized as one of the world's cradles of domestication with evidence for squash (Cucurbita pepo) cultivation appearing as early as 8,000 cal B.C. followed by many other plants, such as maize (Zea mays), peppers (Capsicum annuum), common beans (Phaseolus vulgaris), and cotton (Gossypium hirsutum). We present archaeological, linguistic, ethnographic, and ethnohistoric data demonstrating that sunflower (Helianthus annuus) had entered the repertoire of Mexican domesticates by ca. 2600 cal B.C., that its cultivation was widespread in Mexico and extended as far south as El Salvador by the first millennium B.C., that it was well known to the Aztecs, and that it is still in use by traditional Mesoamerican cultures today. The sunflower's association with indigenous solar religion and warfare in Mexico may have led to its suppression after the Spanish Conquest. The discovery of ancient sunflower in Mexico refines our knowledge of domesticated Mesoamerican plants and adds complexity to our understanding of cultural evolution.  相似文献   
24.
25.
26.
The access to water and the engineered landscapes accommodating its collection and allocation are pivotal issues for assessing sustainability. Recent mapping, sediment coring, and formal excavation at Tikal, Guatemala, have markedly expanded our understanding of ancient Maya water and land use. Among the landscape and engineering feats identified are the largest ancient dam identified in the Maya area of Central America; the posited manner by which reservoir waters were released; construction of a cofferdam for dredging the largest reservoir at Tikal; the presence of ancient springs linked to the initial colonization of Tikal; the use of sand filtration to cleanse water entering reservoirs; a switching station that facilitated seasonal filling and release; and the deepest rock-cut canal segment in the Maya Lowlands. These engineering achievements were integrated into a system that sustained the urban complex through deep time, and they have implications for sustainable construction and use of water management systems in tropical forest settings worldwide.  相似文献   
27.

Background

The ethnic usage of exotics and indigenous problem plants is a highly debated topic, as legislative requirements over-shadow their potential medicinal value, particularly to treat sexually transmitted infections (STIs). Limited information exists regarding their medicinal value among the Bapedi.

Objectives

To ascertain the importance of exotics and indigenous problem plants in the treatment of STIs, a major global primary health care challenge.

Methods

A field observation and semi-structured questionnaire focussing on species diversity, types of STIs treated and medicinal preparation as well as application was used to collect data from 34 traditional healers.

Results

Seven exotics and three indigenous problem species were identified. These species were used to treat four STIs; with Catharanthus roseus illustrating its dominance in the treatment of gonorrhoea. Some medicinal species used by Bapedi traditional healers have been validated through scientific research or through their extensive use by various cultures in South Africa and other parts of Africa. To the best of our knowledge Alternanthera pungens, Caesalpinia decapetala, Cinnamomum verum, and Citrullus lanatus are reported for the first time in the treatment of the investigated STIs.

Conclusions

Exotic and indigenous problem species constitute an important component of the STIs treatment protocol. Their utilization by Bapedi cautions against the narrow-minded approach of indiscriminate eradication, as these species can play a significant role in the primary health care needs of socio-economic vulnerable people.  相似文献   
28.

Introduction

The National Burn Repository (NBR) currently only contains inpatient data from participating United States burn centres. However, the majority of the patients treated in burn centres are managed as outpatients. Unfortunately, this significant demographic is not represented in the NBR annual report. The purpose of this study is to compare the difference in aetiology and demographics between inpatient and outpatient burn patients. In addition, the workload demands for data entry of inpatient and outpatient records in the burn registry will be compared.

Methods

Outpatient and inpatient burn data at an American Burn Association-Verified Burn Center were prospectively collected during fiscal year 2008. Data collected included age, burn size and aetiology of burn. Aetiology was also stratified by age group. Inpatient data were compared with outpatient data with Fisher's exact test. The amount of time taken to enter inpatients’ and outpatients’ data parameters in the TRACS v5.0 database was also recorded.

Results

Data were collected for 241 inpatients and for 543 outpatients during fiscal year 2008. No significant differences in gender or race were found between the two groups. When comparing demographics, outpatients tended to be younger (26 ± 19 years vs. 32 ± 22 years, p = 0.01) with a smaller burn size (2.5 ± 7% vs. 6.8 ± 12%, p < 0.001) and a lower frequency of full-thickness burns (17% vs. 41%, p < 0.001).Of the patients managed as an outpatient, a total 29.7% were eventually admitted to the hospital. Just over half of those (16.7%) initially managed in the outpatient setting were admitted for a planned surgical procedure. The other 13% were admitted for pain control and wound-care issues.Injury was more likely to be caused by flame in inpatients (p < 0.001). Scald injuries were more common in the outpatient setting (34% vs. 27%), but this difference did not reach statistical significance (p = 0.079). Outpatients were more likely to be injured with a contact burn (p < 0.0001). Outpatient injury was more likely to be work-related than inpatient injury (p = 0.0497), but less likely to be related to recreational activity (p = 0.006) or arson/abuse/assault (p = 0.0158). An experienced TRACSv5.0 user required 11 ± 0.6 min to enter an inpatient record and 6 ± 0.6 min to enter an outpatient record in the system (p = 0.002).

Conclusions

Inpatient injury is more likely to be caused by flame, whereas outpatient injury is more likely to be caused by scald and contact burns. Work-related burn is more likely to be treated in the outpatient setting. Outpatient burn data also take less time to enter. Since significant differences in aetiology exist, outpatient data should be reported separately from inpatient data in order to understand the full spectrum of burn aetiology. The NBR and other registries should be modified to track outpatient burn data and outcomes.  相似文献   
29.
30.
Electroconvulsive therapy (ECT) is a uniquely effective treatment for major depressive disorder. An increase in hippocampal neurogenesis is implicated in the recovery from depression. We used an inducible genetic mouse model in which only GFAP‐expressing stem‐like cells (type‐1 cells) and their progeny are selectively labeled with the reporter protein β‐galactosidase to track the process of neurogenesis in the dentate gyrus over 3 months following electroconvulsive seizures (ECS), the mouse equivalent of ECT. All ECS protocols tested induced a transient increase in type‐1 cell divisions. While this led to an expansion of the type‐1 cell pool after high‐frequency ECS sessions for 5 consecutive days (5‐ECS), asymmetric divisions drove neurogenesis by giving rise to Doublecortin (DCX)‐expressing neuroblasts that matured into NeuN+ neurons. Significantly, the increase in newly generated DCX+ and NeuN+ cells after 5‐ECS could be traced back to proliferating type‐1 cells. Low‐frequency continuation ECS (c‐ECS) consisting of five single ECS sessions administered every 2 weeks resulted in a similar increase in newborn neurons as the high‐frequency 5‐ECS protocol. Moreover, the combination of 5‐ECS and c‐ECS led to a further significant increase in newborn neurons, suggesting a cellular mechanism responsible for the propitious effects of high‐frequency ECT followed by continuation ECT in severely depressed patients. The ability of high‐ and low‐frequency ECS to induce normally quiescent type‐1 cells to proliferate and generate new neurons sets it apart from other antidepressant treatments and may underlie the superior clinical efficacy of ECT. © 2013 Wiley Periodicals, Inc.  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