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   6016篇
  免费   505篇
  国内免费   18篇
耳鼻咽喉   63篇
儿科学   286篇
妇产科学   91篇
基础医学   738篇
口腔科学   153篇
临床医学   742篇
内科学   1283篇
皮肤病学   69篇
神经病学   553篇
特种医学   349篇
外科学   717篇
综合类   291篇
一般理论   4篇
预防医学   508篇
眼科学   72篇
药学   349篇
中国医学   26篇
肿瘤学   245篇
  2021年   75篇
  2020年   60篇
  2019年   85篇
  2018年   94篇
  2017年   83篇
  2016年   76篇
  2015年   93篇
  2014年   146篇
  2013年   238篇
  2012年   335篇
  2011年   321篇
  2010年   193篇
  2009年   170篇
  2008年   274篇
  2007年   331篇
  2006年   248篇
  2005年   241篇
  2004年   243篇
  2003年   200篇
  2002年   207篇
  2001年   198篇
  2000年   207篇
  1999年   158篇
  1998年   96篇
  1997年   84篇
  1996年   77篇
  1995年   86篇
  1994年   87篇
  1993年   75篇
  1992年   110篇
  1991年   124篇
  1990年   98篇
  1989年   96篇
  1988年   113篇
  1987年   97篇
  1986年   104篇
  1985年   102篇
  1984年   65篇
  1983年   78篇
  1982年   63篇
  1981年   46篇
  1980年   38篇
  1979年   55篇
  1978年   55篇
  1977年   33篇
  1976年   35篇
  1975年   41篇
  1973年   32篇
  1971年   31篇
  1968年   32篇
排序方式: 共有6539条查询结果,搜索用时 890 毫秒
1.
For patients who receive a liver transplant (LTX) for alcoholic liver disease (ALD), investigators are focusing beyond survival to determine specific alcohol use outcomes. Studies suggest the use of alcohol ranges from 8 to 22% for the first post-transplant year with cumulative rates reaching 30 to 40% by 5 years following transplantation. Yet while investigators are interested in determining specific rates of alcohol use and predictors of use, only three studies since 1990 have been prospective. In 1998, we began a prospective study of post-LTX alcohol consumption in ALD recipients using multiple repeated measures of alcohol use. After 5 years of follow-up, we found that 22% had used any alcohol by the first year and 42% had a drink by 5 years. By 5 years, 26% drank at a heavier use (binge) pattern and 20% drank in a frequent pattern. In a univariate model, predictors of alcohol use included pre-transplant length of sobriety, a diagnosis of alcohol dependence, a history of other substance use, and prior alcohol rehabilitation.  相似文献   
2.
3.
IL2-PE40 is a chimeric protein composed of human interleukin-2 (IL2) genetically fused to a modified form of Pseudomonas exotoxin lacking the cell recognition domain. IL2-PE40 is cytotoxic for IL2 receptor-bearing lymphocytes in culture and can inhibit activation of T cells in vivo. IL2-PE40 can significantly diminish antigen-stimulated proliferation of lymphocytes sensitized to myelin basic protein. Intraperitoneal administration of IL2-PE40 not only markedly inhibits the clinical manifestations of adoptively transferred relapsing experimental allergic encephalomyelitis but also dramatically reduces both inflammation and demyelination characteristic of the disease.  相似文献   
4.
Ruggieri  PM; Laub  GA; Masaryk  TJ; Modic  MT 《Radiology》1989,171(3):785-791
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study.  相似文献   
5.
BACKGROUND: Although nationally recognized learning objectives for undergraduate surgical education exist, the extent to which Canadian medical schools follow these guidelines has never been established. METHODS: We distributed a survey to all program directors and clinical-teaching-unit coordinators for undergraduate surgery at Canada's 16 medical schools, and subsequently assessed the perceived emphasis placed on learning objectives and student performance, and the impact of instructional tools and teaching locations. RESULTS: Program directors in 15 medical schools responded to the survey. We identified a wide variation in the emphasis placed on basic learning objectives as well as specialty specific learning objectives. The length of rotations, methods of instruction and tools used to grade student performance also varied widely. CONCLUSIONS: Our findings suggest significant variation in the design and implementation of undergraduate surgical education in Canada. This study may serve as a basis for reassessing learning objectives in Canadian undergraduate surgical education.  相似文献   
6.
7.
8.
We tested the hypothesis that since the implementation of the prospective payment system (PPS), elderly patients hospitalized for hip fractures receive shorter, less care-intensive hospitalizations and are more frequently institutionalized. In blinded fashion, we reviewed the charts of elderly patients with hip fractures admitted to a municipal hospital from 1981 through 1985. Demographic and clinical characteristics of patients treated before implementation of the PPS were similar to patients treated thereafter. After implementation of the PPS, the mean length of hospitalization fell from 16.6 to 10.3 days, and the mean number of physical therapy sessions received decreased from 9.7 to 4.9. Concomitantly, the proportion of patients discharged to a nursing home increased (21% to 48%), as did the proportion receiving nursing home care at six months after discharge (13% to 39%). This increase in long-term nursing home placement suggests that the quality of care for elderly patients with hip fractures may have deteriorated.  相似文献   
9.
BACKGROUND: In general practice, acute sinusitis is frequently diagnosed and treated with antibiotics. OBJECTIVE: This study aimed to determine the evidence for the effectiveness of antibiotic treatment in acute maxillary sinusitis in adults by assessing the methodological quality of placebo-controlled double-blind randomized trials. METHOD: An evaluation by four raters through a 35-item scoring-scale for internal and external validity of all placebo-controlled double-blind randomized trials on acute sinusitis found between January 1966 and July 1996. RESULTS: Eighty-five trials were excluded because they were not placebo-controlled, double-blind, randomized, or were carried out in patients with chronic sinusitis or in children. The three remaining trials were performed in different populations (one in general practice) between 1973 and 1978. Only one study claimed superiority of antibiotic treatment. Different inclusion criteria and major outcome measures were used by the authors. The reliability of major outcome events was reported poorly or not at all and in two studies outcome measures were clinically inappropriate. The studies scored 30-62% of the maximum attainable score for internal validity and 10-20% for external validity. CONCLUSION: The effectiveness of antibiotic treatment in acute maxillary sinusitis in a general practice population is not based sufficiently on evidence.   相似文献   
10.
The authors describe 12 patients in whom feeding tubes were inadvertently placed in the bronchial tree a total of 14 times. All but four of the misplacements were complicated by pneumothorax. No deaths were directly attributable to the misplacements, although one cardiac arrest occurred as a late complication of intrapleural feeding. Careful, controlled insertion of feeding tubes and radiographic confirmation of their placement are essential to reduce morbidity and mortality.  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