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   1529681篇
  免费   121378篇
  国内免费   3689篇
耳鼻咽喉   20106篇
儿科学   50067篇
妇产科学   43907篇
基础医学   217400篇
口腔科学   42622篇
临床医学   133978篇
内科学   313306篇
皮肤病学   37270篇
神经病学   126626篇
特种医学   56462篇
外国民族医学   464篇
外科学   224640篇
综合类   33385篇
现状与发展   3篇
一般理论   536篇
预防医学   122412篇
眼科学   34090篇
药学   107094篇
  1篇
中国医学   3967篇
肿瘤学   86412篇
  2021年   14095篇
  2019年   14893篇
  2018年   21590篇
  2017年   15648篇
  2016年   17029篇
  2015年   19201篇
  2014年   26316篇
  2013年   38916篇
  2012年   54732篇
  2011年   57954篇
  2010年   33245篇
  2009年   30737篇
  2008年   52048篇
  2007年   55023篇
  2006年   54784篇
  2005年   53036篇
  2004年   50131篇
  2003年   47538篇
  2002年   45709篇
  2001年   75533篇
  2000年   77493篇
  1999年   63773篇
  1998年   17468篇
  1997年   15769篇
  1996年   15880篇
  1995年   15016篇
  1994年   13585篇
  1993年   12745篇
  1992年   46712篇
  1991年   44209篇
  1990年   42209篇
  1989年   40126篇
  1988年   36662篇
  1987年   35828篇
  1986年   33361篇
  1985年   31691篇
  1984年   24132篇
  1983年   20270篇
  1982年   12336篇
  1981年   10889篇
  1979年   20986篇
  1978年   14758篇
  1977年   12257篇
  1976年   11537篇
  1975年   11853篇
  1974年   14254篇
  1973年   13838篇
  1972年   12889篇
  1971年   11746篇
  1970年   11170篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
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   
52.
53.
54.
55.
Obesity Surgery - Laparoscopic sleeve gastrectomy (LSG) is increasingly playing a key role in obesity management. Such operations, however, carry complications sometimes including leaks. The...  相似文献   
56.
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   
57.
58.
59.
60.
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