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   2584篇
  免费   227篇
  国内免费   9篇
耳鼻咽喉   3篇
儿科学   71篇
妇产科学   58篇
基础医学   404篇
口腔科学   29篇
临床医学   337篇
内科学   400篇
皮肤病学   19篇
神经病学   290篇
特种医学   169篇
外科学   400篇
综合类   138篇
一般理论   1篇
预防医学   228篇
眼科学   18篇
药学   163篇
肿瘤学   92篇
  2021年   27篇
  2020年   27篇
  2019年   41篇
  2018年   34篇
  2017年   26篇
  2016年   29篇
  2015年   28篇
  2014年   43篇
  2013年   76篇
  2012年   115篇
  2011年   100篇
  2010年   97篇
  2009年   84篇
  2008年   126篇
  2007年   119篇
  2006年   123篇
  2005年   114篇
  2004年   116篇
  2003年   100篇
  2002年   93篇
  2001年   67篇
  2000年   70篇
  1999年   48篇
  1998年   39篇
  1997年   33篇
  1996年   41篇
  1995年   41篇
  1994年   27篇
  1993年   31篇
  1992年   55篇
  1991年   32篇
  1990年   53篇
  1989年   65篇
  1988年   51篇
  1987年   43篇
  1986年   65篇
  1985年   62篇
  1984年   48篇
  1983年   36篇
  1982年   18篇
  1981年   19篇
  1980年   21篇
  1979年   42篇
  1978年   20篇
  1977年   22篇
  1976年   28篇
  1975年   25篇
  1974年   22篇
  1973年   21篇
  1968年   19篇
排序方式: 共有2820条查询结果,搜索用时 0 毫秒
41.
42.
43.
We investigated the utility of three manual planimetric methods to quantify carotid plaque volume. A single observer measured 15 individual plaques from 15 three-dimensional (3D) ultrasound (3D US) images of patients ten times each using three different planimetric approaches. Individual plaque volumes were measured (range: 32.6-597.1 mm3) using a standard planimetric approach (M1) whereby a plaque end was identified and sequential contours were measured. The same plaques were measured using a second approach (M2), whereby plaque ends were first identified and the 3D US image of the plaque was then subdivided into equal intervals. A third method (M3) was used to measure total plaque burden (range: 165.1-1080.0 mm3) in a region (+/- 1.5 cm) relative to the carotid bifurcation. M1 systematically underestimated individual plaque volume compared to M2 (V2 = V1 + 14.0 mm3, r = 0.99, p = 0.006) due to a difference in the mean plaque length measured. Coefficients of variance (CV) for M1 and M2 decrease with increasing plaque volume, with M2 results less than M1. Root mean square difference between experimental and theoretical CV for M2 was 3.2%. The standard deviation in the identification of the transverse location of the carotid bifurcation was 0.56 mm. CVs for plaque burden measured using M3 ranged from 1.2% to 7.6% and were less than CVs determined for individual plaque volumes of the same volume. The utility of M3 was demonstrated by measuring carotid plaque burden and volume change over a period of 3 months in three patients. In conclusion, M2 was determined to be a more superior measurement technique than M1 to measure individual plaque volume. Furthermore, we demonstrated the utility of M3 to quantify regional plaque burden and to quantify change in plaque volume.  相似文献   
44.
45.
46.
47.
In December, 1993, we initiated a pilot project in which DNA fragile X (fraX) testing was offered during routine prenatal or genetic counseling to all pregnant women seen at the Genetics & IVF Institute, most of whom were referred for the indication of advanced maternal age. A brochure on fragile X syndrome was sent to each patient prior to her appointment and was reviewed by a counselor or physician during the counseling session. As of June 1995, 3,345 patients were offered testing; 474 women with no identified family history of mental retardation or learning disability and 214 women with a positive family history accepted the test on a self-pay basis. The second population screened was 271 potential donors in our anonymous egg donor program. DNA from blood was tested by Southern blot using EcoRI/EagI and StB12.3. If an expansion was detected, CGG repeat number was determined by PCR-based analysis. Among the 474 patients with unremarkable family histories, three fraX carriers were identified (repeat sizes = 60+), whereas none were found in the 214 patients with a positive family history. Among the potential egg donors, two high borderline patients were identified (repeat sizes = between 50 and 59). Our ongoing study indicates that screening of pregnant or preconceptual populations for fraX carrier status using DNA testing is accepted by many patients and is an important addition to current medical practice. © 1996 Wiley-Liss, Inc.  相似文献   
48.
Post‐traumatic stress disorder (PTSD) is a debilitating condition that may develop after experiencing a traumatic event. Combat exposure increases an individual's chance of developing PTSD, making veterans especially susceptible to the disorder. PTSD is characterized by dysregulated emotional networks, memory deficits, and a hyperattentive response to perceived threatening stimuli. Recently, there have been a number of imaging studies that show structural and functional abnormalities associated with PTSD; however, there have been few studies utilizing electroencephalography (EEG). The goal of this study was to characterize **EEG brain dynamics in individuals with PTSD, in order to better understand the neurophysiological underpinnings of some of the salient features of PTSD, such as threat‐processing bias. Veterans of Operation Enduring Freedom/Iraqi Freedom completed an implicit visual threat semantic memory recognition task with stimuli that varied on both category (animals, items, nature, and people) and feature (threatening and nonthreatening) membership, including trauma‐related stimuli. Combat veterans with PTSD had slower reaction times for the threatening stimuli relative to the combat veterans without PTSD (VETC). There were trauma‐specific effects in frontal regions, with theta band EEG power reductions for the threatening combat scenes in the PTSD patients compared to the VETC group. Additionally, a moderate negative correlation was observed between trauma‐specific frontal theta power and hyperarousal symptoms as measured by clinically administered PTSD scale. These findings complement and extend current models of cortico‐limbic dysfunction in PTSD. The moderate negative correlation between frontal theta power and hyperarousal endorsements suggests the utility of these measures as therapeutic markers of symptomatology in PTSD patients.  相似文献   
49.
The aims of this systematic review are to determine the availability of healthy food and beverages in hospitals and identify interventions that positively influence the hospital food environment, thereby improving the dietary intake of employees and visitors. Embase, Medline, APA PsycInfo, Scopus, Google Scholar and Google were used to identify publications. Publications relating to the wider hospital food environment in the UK and USA were considered eligible, while those regarding food available to in-patients were excluded. Eligible publications (n = 40) were explored using a narrative synthesis. Risk of bias and research quality were assessed using the Quality Criteria Checklist for Primary Research. Although limited by the heterogeneity of study designs, this review concludes that the overall quality of hospital food environments varies. Educational, labelling, financial and choice architecture interventions were shown to improve the hospital food environment and/or dietary intake of consumers. Implementing pre-existing initiatives improved food environments, but multi-component interventions had some undesirable effects, such as reduced fruit and vegetable intake.  相似文献   
50.
OBJECTIVE: To test a theoretical model linking nurses' perceptions of workplace empowerment, magnet hospital characteristics, and job satisfaction in 3 independent studies of nurses in different work settings. BACKGROUND: Strategies proposed in Kanter's structural empowerment theory have the potential to result in work environments that are described in terms of magnet hospital characteristics. Identifying factors that contribute to work conditions that attract and retain highly qualified committed nurses, such as those found in magnet hospitals, that can be put in place by nursing administrators is extremely important for work redesign to promote professional nursing practice. METHODS: Secondary analyses of data from 3 studies were conducted--2 of staff nurses and 1 with acute care nurse practitioners working in Ontario, Canada. The Conditions of Work Effectiveness Questionnaire-II, the NWI-R, and measures of job satisfaction were used to measure the major study variables.RESULTS The results of all 3 studies support the hypothesized relationships between structural empowerment and the magnet hospital characteristics of autonomy, control over practice environment, and positive nurse-physician relationships. The combination of access to empowering work conditions and magnet hospital characteristics was significantly predictive of nurses' satisfaction with their jobs. CONCLUSIONS/IMPLICATIONS: These findings suggest that nursing leaders' efforts to create empowering work environments can influence nurses' ability to practice in a professional manner, ensuring excellent patient care quality and positive organizational outcomes.  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