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   1408937篇
  免费   115762篇
  国内免费   3332篇
耳鼻咽喉   18376篇
儿科学   46563篇
妇产科学   41070篇
基础医学   200896篇
口腔科学   37716篇
临床医学   125976篇
内科学   284397篇
皮肤病学   33369篇
神经病学   116959篇
特种医学   53845篇
外国民族医学   464篇
外科学   210599篇
综合类   32753篇
现状与发展   3篇
一般理论   487篇
预防医学   110013篇
眼科学   31491篇
药学   98579篇
  1篇
中国医学   3347篇
肿瘤学   81127篇
  2021年   10857篇
  2019年   11667篇
  2018年   16571篇
  2017年   12668篇
  2016年   14265篇
  2015年   16011篇
  2014年   22577篇
  2013年   33413篇
  2012年   45416篇
  2011年   47964篇
  2010年   28175篇
  2009年   27062篇
  2008年   44361篇
  2007年   46868篇
  2006年   47424篇
  2005年   45906篇
  2004年   43778篇
  2003年   41725篇
  2002年   40215篇
  2001年   73030篇
  2000年   74561篇
  1999年   61582篇
  1998年   16996篇
  1997年   15440篇
  1996年   15589篇
  1995年   14795篇
  1994年   13400篇
  1993年   12585篇
  1992年   45852篇
  1991年   43504篇
  1990年   41502篇
  1989年   39573篇
  1988年   36192篇
  1987年   35368篇
  1986年   32872篇
  1985年   31296篇
  1984年   23839篇
  1983年   20032篇
  1982年   12218篇
  1981年   10794篇
  1979年   20714篇
  1978年   14582篇
  1977年   12094篇
  1976年   11369篇
  1975年   11624篇
  1974年   13998篇
  1973年   13539篇
  1972年   12640篇
  1971年   11477篇
  1970年   10919篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
43.
44.
BACKGROUND AND PURPOSE:Endovascular therapy for acute ischemic stroke is often performed with the patient under conscious sedation. Emergent conversion from conscious sedation to general anesthesia is sometimes necessary. The aim of this study was to assess the functional outcome in converted patients compared with patients who remained in conscious sedation and to identify predictors associated with the risk of conversion.MATERIALS AND METHODS:Data from 368 patients, included in 3 trials randomizing between conscious sedation and general anesthesia before endovascular therapy (SIESTA, ANSTROKE, and GOLIATH) constituted the study cohort. Twenty-one (11%) of 185 patients randomized to conscious sedation were emergently converted to general anesthesia.RESULTS:Absence of hyperlipidemia seemed to be the strongest predictor of conversion to general anesthesia, albeit a weak predictor (area under curve = 0.62). Sex, hypertension, diabetes, smoking status, atrial fibrillation, blood pressure, size of the infarct, and level and side of the occlusion were not significantly associated with conversion to general anesthesia. Neither age (mean age, 71.3   ± 13.8 years for conscious sedation versus 71.6  ± 12.3 years for converters, P = .58) nor severity of stroke (mean NIHSS score, 17 ± 4 versus 18 ± 4, respectively, P = .27) were significantly different between converters and those who tolerated conscious sedation. The converters had significantly worse outcome with a common odds ratio of 2.67 (P = .015) for a shift toward a higher mRS score compared with the patients remaining in the conscious sedation group.CONCLUSIONS:Patients undergoing conversion had significantly worse outcome compared with patients remaining in conscious sedation. No factor was identified that predicted conversion from conscious sedation to general anesthesia.

Five studies published in 2015 proved the efficacy of endovascular therapy (EVT) for acute ischemic stroke caused by a large-vessel occlusion.1 However, numerous questions remain regarding how to best deliver this treatment, including evaluation of the optimal thrombectomy technique,2 the most effective method of patient triage,3 or whether EVT should be performed with the patient under either general anesthesia (GA) or conscious sedation (CS).Observational studies have suggested that EVT with the patient under CS is associated with better neurologic outcome and lower mortality compared with GA.4 However, 3 randomized trials reported similar outcomes between CS and GA.5-7 Proposed benefits of CS include stable hemodynamics, clinical monitoring, and a potentially shorter procedure. The disadvantages are an unprotected airway and patient movement, which sometimes may require emergent conversion to GA. Patients who need conversion might be sicker (larger strokes, more medical complications), but the conversion procedure itself may also have a potentially deleterious influence on outcome due to the emergent anesthetic induction, associated hypotension, and added time delay before reperfusion.Although most patients can be treated under the less complex CS, it is of interest to identify factors that can predict the risk of conversion and hence the requirement for GA. We undertook a detailed analysis of the patients who were converted from CS to GA in our individual patient data base from the 3 randomized trials to examine the outcome of the converted patients compared with patients who remained in CS. We also aimed to identify possible predictors associated with a need for GA with EVT.  相似文献   
45.
46.
47.
48.
49.
Behçet disease is a complex, multisystem disease characterized by recurrent oral and genital ulcerations. It rarely occurs in infants or children. Neonatal Behçet disease has been reported in infants whose ulcers resolve at or before 9 weeks of age. Few cases of neonatal Behçet disease persisting into childhood have previously been reported. We report the case of a 1‐month‐old infant who presented with severe recurrent genital ulcerations and at 6 months developed recurrent oral ulcerations. Her orogenital ulcerations continue to recur. Human leukocyte antigen testing revealed HLA‐B51 and B44 positivity. This is a case of pediatric Behçet disease in the neonatal period. Behçet disease should be considered in the differential diagnosis of recurrent genital and oral ulcerations in infants and children.  相似文献   
50.
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