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   4935篇
  免费   563篇
  国内免费   3篇
耳鼻咽喉   51篇
儿科学   144篇
妇产科学   78篇
基础医学   842篇
口腔科学   77篇
临床医学   514篇
内科学   753篇
皮肤病学   31篇
神经病学   527篇
特种医学   251篇
外科学   1054篇
综合类   87篇
一般理论   2篇
预防医学   503篇
眼科学   112篇
药学   294篇
中国医学   3篇
肿瘤学   178篇
  2021年   65篇
  2019年   65篇
  2018年   71篇
  2017年   49篇
  2016年   49篇
  2015年   71篇
  2014年   89篇
  2013年   150篇
  2012年   185篇
  2011年   166篇
  2010年   115篇
  2009年   106篇
  2008年   181篇
  2007年   176篇
  2006年   220篇
  2005年   202篇
  2004年   181篇
  2003年   181篇
  2002年   198篇
  2001年   180篇
  2000年   160篇
  1999年   140篇
  1998年   65篇
  1997年   51篇
  1996年   53篇
  1995年   51篇
  1994年   53篇
  1993年   49篇
  1992年   124篇
  1991年   138篇
  1990年   153篇
  1989年   128篇
  1988年   124篇
  1987年   117篇
  1986年   93篇
  1985年   92篇
  1984年   77篇
  1983年   79篇
  1982年   55篇
  1981年   54篇
  1979年   63篇
  1978年   45篇
  1976年   48篇
  1975年   50篇
  1974年   57篇
  1972年   43篇
  1971年   57篇
  1970年   51篇
  1969年   56篇
  1968年   46篇
排序方式: 共有5501条查询结果,搜索用时 109 毫秒
11.
Narrowband irradiation of water protons with a surface coil yields significant nuclear Overhauser enhancement (nOe) of phosphocreatine (PCr) and some adenosine triphosphate (ATP) moieties in localized and unlocalized phosphorus (31P) NMR spectra from chest and heart muscle. In seven normal subjects at 1.5 T the nOe values were 0.6 +/- 0.3, 0.6 +/- 0.3, 0 +/- 0.3, and 0.3 +/- 0.2 for myocardial PCr, gamma-ATP, alpha-ATP, and beta-ATP, respectively, not significantly different from those in chest muscle. Distortion of the measured PCr/ATP ratios due to differences in the nOe may require accurate correction to realize the full benefit of the effect in studies involving quantitative intergroup comparisons.  相似文献   
12.
Dysplasia is the only marker for malignant potential in Barrett's esophagus. The histologic interpretation of dysplasia is sometimes difficult, particularly when attempting to distinguish dysplastic changes from those of a regenerating and inflammatory mucosa. In order to find an objective marker to identify patients with high risk of malignant transformation, the authors evaluated 497 biopsies from 66 patients with Barrett's esophagus with flow cytometry. The aim of the study was to correlate DNA content and proliferative abnormalities with histology. All biopsies classified histologically as negative for dysplasia had a diploid DNA content. The percentage of biopsies with an aneuploid DNA content increased with the histologic grade of dysplasia: 2 percent of indefinite dysplasia, 11 percent of low grade dysplasia, 44 percent of high grade dysplasia and 78 percent of biopsy specimens with cancer biopsies were aneuploid. Mean S and G2M fractions of diploid biopsy specimens increased with the severity of histologic changes. The S and G2M fraction threshold values that could differentiate patients that were negative for dysplasia from those with high grade dysplasia or cancer were 9 percent and 6 percent, respectively. Aneuploidy or G2M fraction greater than 6 percent was the best discriminating criteria between those two distinct groups of patients. All 6 patients with high grade dysplasia or cancer had aneuploid cell populations or increased G2M fraction, whereas none of the 35 patients whose biopsies were histologically negative for dysplasia had evidence of genomic instability or increased G2M fraction. Flow cytometric abnormalities were found in 10 out of 25 patients whose biopsies were classified as indefinite for dysplasia or low grade dysplasia.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
13.
14.
15.
16.
17.
Because of reduced health care funding it is becoming necessary for surgeons to take a greater interest in the costs of individual operations. This study reports costs directly measurable to the patient, and also the indirect costs of hospital overheads, an operating suite and teaching, which were 37, 10 and 15%, respectively (62%), of hospital budget. A scheme has been developed which could give surgeons a standard to report direct costs. Pre-admission, ward, operating room, recovery, intensive care and post-admission are defined as cost periods and the modalities of staff, equipment (capital, maintenance and replacement), imaging, laboratory and consumables apply to each. This strategy was applied to assess open cholecystectomy (OC) and laparoscopic cholecystectomy (LC) as an example. The direct costs for OC were $3706 and LC $2868, a difference of $838; the indirect and direct costs were OC $6004 and LC $4646, a difference of $1358. Thus indirect cost magnified the difference between the operations. Bed stay, density of nursing and use of disposable instruments were the major influences on direct costs. The individual cost advantage of a shorter bed stay may be countervailed by an increased hospital activity. The main patient benefit of new operations may be improved quality of life and more rapid return to work with prevention of salary losses. A method has been developed to define costs of a particular surgical operation with the purpose of stimulating surgeons' interest in this topic and developing a common style of reporting. This method should help clinicians dealing with hospital finances and waiting lists. Indirect costs are a hidden substantial cost of surgery. Considerably more attention needs to be paid to indirect costs in controlling surgical budgets.  相似文献   
18.
19.
Squamous cell carcinoma (SCC) of the temporal bone is a rare, aggressive and highly malignant tumour that requires specialised, multidisciplinary surgery for its treatment. Reconstruction of the defect is as crucial as the tumour ablation in terms of mortality and postoperative morbidity. METHODS: The experience of the East Anglian Skull Base Surgery Service from 1982 to 2004 in managing 42 consecutive patients (22 females; age range 37-80 years) undergoing extended and lateral temporal bone resection for SCC is presented. RESULTS: The overall 5-year survival was 31.0% (median follow up: 97 months) when both curative and palliative procedures were included. On multivariate analysis, the favourable prognostic factors were male sex, well-differentiated tumours and stage N(0) neck. The reconstructions in 38 patients were analysed. The majority (24/38) had free tissue transfer reconstructions and most of these were radial forearm free flaps. Later in the series, other free flap types such as anterolateral thigh flaps and lateral arm flaps were employed. Pedicled myocutaneous flaps and local flaps were also used. CONCLUSIONS: This paper analyses the outcomes of the various reconstructions and discusses the evolution of their care in our unit. The information obtained from the review of our data is extrapolated to offer guidance on the choice of reconstructive option in these patients.  相似文献   
20.
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