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   15392篇
  免费   1053篇
  国内免费   38篇
耳鼻咽喉   165篇
儿科学   614篇
妇产科学   471篇
基础医学   2235篇
口腔科学   260篇
临床医学   2097篇
内科学   2517篇
皮肤病学   288篇
神经病学   1714篇
特种医学   279篇
外科学   1116篇
综合类   155篇
现状与发展   1篇
一般理论   40篇
预防医学   2261篇
眼科学   207篇
药学   861篇
中国医学   11篇
肿瘤学   1191篇
  2023年   138篇
  2022年   160篇
  2021年   352篇
  2020年   265篇
  2019年   387篇
  2018年   387篇
  2017年   350篇
  2016年   310篇
  2015年   380篇
  2014年   543篇
  2013年   839篇
  2012年   1156篇
  2011年   1206篇
  2010年   603篇
  2009年   567篇
  2008年   1030篇
  2007年   1012篇
  2006年   1031篇
  2005年   1035篇
  2004年   929篇
  2003年   858篇
  2002年   846篇
  2001年   142篇
  2000年   84篇
  1999年   119篇
  1998年   196篇
  1997年   156篇
  1996年   110篇
  1995年   114篇
  1994年   96篇
  1993年   82篇
  1992年   86篇
  1991年   52篇
  1990年   53篇
  1989年   44篇
  1988年   43篇
  1987年   31篇
  1986年   52篇
  1985年   50篇
  1984年   54篇
  1983年   66篇
  1982年   83篇
  1981年   55篇
  1980年   54篇
  1979年   32篇
  1978年   35篇
  1977年   24篇
  1976年   19篇
  1974年   23篇
  1973年   15篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
41.
42.
ABSTRACT: Background: Hands‐and‐knees positioning during labor has been recommended on the theory that gravity and buoyancy may promote fetal head rotation to the anterior position and reduce persistent back pain. A Cochrane review found insufficient evidence to support the effectiveness of this intervention during labor. The purpose of this study was to evaluate the effect of maternal hands‐and‐knees positioning on fetal head rotation from occipitoposterior to occipitoanterior position, persistent back pain, and other perinatal outcomes. Methods: Thirteen labor units in university‐affiliated hospitals participated in this multicenter randomized, controlled trial. Study participants were 147 women laboring with a fetus at ≥37 weeks’ gestation and confirmed by ultrasound to be in occipitoposterior position. Seventy women were randomized to the intervention group (hands‐and‐knees positioning for at least 30 minutes over a 1‐hour period during labor) and 77 to the control group (no hands‐and‐knees positioning). The primary outcome was occipitoanterior position determined by ultrasound following the 1‐hour study period and the secondary outcome was persistent back pain. Other outcomes included operative delivery, fetal head position at delivery, perineal trauma, Apgar scores, length of labor, and women's views with respect to positioning. Results: Women randomized to the intervention group had significant reductions in persistent back pain. Eleven women (16%) allocated to use hands‐and‐knees positioning had fetal heads in occipitoanterior position following the 1‐hour study period compared with 5 (7%) in the control group (relative risk 2.4; 95% CI 0.88–6.62; number needed to treat 11). Trends toward benefit for the intervention group were seen for several other outcomes, including operative delivery, fetal head position at delivery, 1‐minute Apgar scores, and time to delivery. Conclusions: Maternal hands‐and‐knees positioning during labor with a fetus in occipitoposterior position reduces persistent back pain and is acceptable to laboring women. Given this evidence, hands‐and‐knees positioning should be offered to women laboring with a fetus in occipitoposterior position in the first stage of labor to reduce persistent back pain. Although this study demonstrates trends toward improved birth outcomes, further trials are needed to determine if hands‐and‐knees positioning promotes fetal head rotation to occipitoanterior and reduces operative delivery. (BIRTH 32:4 December 2005)  相似文献   
43.
44.
Brain function requires oxygen and maintenance of brain capillary oxygenation is important. We evaluated how faithfully frontal lobe near-infrared spectroscopy (NIRS) follows haemoglobin saturation (SCap) and how calculated mitochondrial oxygen tension (PMitoO2) influences motor performance. Twelve healthy subjects (20 to 29 years), supine and seated, inhaled O2 air-mixtures (10% to 100%) with and without added 5% carbon dioxide and during hyperventilation. Two measures of frontal lobe oxygenation by NIRS (NIRO-200 and INVOS) were compared with capillary oxygen saturation (SCap) as calculated from the O2 content of brachial arterial and right internal jugular venous blood. At control SCap (78%+/-4%; mean+/-s.d.) was halfway between the arterial (98%+/-1%) and jugular venous oxygenation (SvO2; 61%+/-6%). Both NIRS devices monitored SCap (P<0.001) within approximately 5% as SvO2 increased from 39%+/-5% to 79%+/-7% with an increase in the transcranial ultrasound Doppler determined middle cerebral artery flow velocity from 29+/-8 to 65+/-15 cm/sec. When SCap fell below approximately 70% with reduced flow and inspired oxygen tension, PMitoO2 decreased (P<0.001) and brain lactate release increased concomitantly (P<0.001). Handgrip strength correlated with the measured (NIRS) and calculated capillary oxygenation values as well as with PMitoO2 (r>0.74; P<0.05). These results show that NIRS is an adequate cerebral capillary-oxygenation-level-dependent (COLD) measure during manipulation of cerebral blood flow or inspired oxygen tension, or both, and suggest that motor performance correlates with the frontal lobe COLD signal.  相似文献   
45.
Objective  The objective of this study was to describe the perceived health status of the meat industry employees—i.e., working in the slaughtering, cutting, and boning of large animals and poultry—and its relation to their organisational and psychosocial constraints at work. Methods  This postal survey included all 3,000 employees of the meat industry (beef, pork and poultry) in four districts in Brittany, France, whose companies were affiliated with the agricultural branch of the national health insurance fund. The questionnaire asked for social and demographic data and information describing their job and the organisation of their work. The psychosocial factors at work were described according to Karasek’s questionnaire (demand, latitude and social support at work). Perceived health was measured with the Nottingham Health Profile perceived health indicator. Results  This study shows the high prevalence of poor health reported by the workers in this industry. This poor perceived health was worse in women and increased regularly with age. Among the psychosocial factors studied, high quantitative and qualitative demand at work, inadequate resources for good work and to a lesser extent, inadequate prospects for promotion appear especially associated with poor perceived health. Other factors often associated with poor perceived health included young age at the first job and work hours that disrupt sleep rhythms (especially for women). Conclusion  Our results show that this population of workers is especially vulnerable from the point of view of perceived physical and psychological health and is exposed to strong physical, organisational and psychosocial constraints at work. They also demonstrate that poor perceived health is associated with some psychosocial (such as high psychological demand and insufficient resources) and organisational factors at work. These results, in conjunction with those from other disciplines involved in studying this industry, may help the companies to develop preventive activities.  相似文献   
46.
47.
48.
49.
50.
To address a recurring shortage of nurses in the aboriginal communities of Northwestern Ontario, the First Nations and Inuit Health Branch, Health Canada, commissioned a study to explore the viability of establishing a relief pool among nurses from nearby small industrial towns. An open/close-ended survey completed by a random sample of 237 nurses from the target population documented levels of awareness, willingness, and preparedness for northern practice, as well as recruitment incentives and disincentives. Findings demonstrate an awareness of the overlap between the professional and personal dimensions characteristic of such practices, and suggest support for innovative rotations that would cut across federal/provincial/community jurisdictions. Although complex, given time and willingness, a regional relief system seems viable.  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