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   9536篇
  免费   526篇
  国内免费   60篇
耳鼻咽喉   89篇
儿科学   226篇
妇产科学   256篇
基础医学   1241篇
口腔科学   182篇
临床医学   849篇
内科学   2426篇
皮肤病学   128篇
神经病学   915篇
特种医学   267篇
外科学   1549篇
综合类   47篇
一般理论   3篇
预防医学   323篇
眼科学   116篇
药学   686篇
  1篇
中国医学   16篇
肿瘤学   802篇
  2023年   78篇
  2022年   123篇
  2021年   284篇
  2020年   161篇
  2019年   223篇
  2018年   226篇
  2017年   153篇
  2016年   217篇
  2015年   285篇
  2014年   403篇
  2013年   438篇
  2012年   665篇
  2011年   721篇
  2010年   404篇
  2009年   333篇
  2008年   624篇
  2007年   686篇
  2006年   590篇
  2005年   562篇
  2004年   533篇
  2003年   489篇
  2002年   403篇
  2001年   107篇
  2000年   100篇
  1999年   128篇
  1998年   90篇
  1997年   82篇
  1996年   69篇
  1995年   74篇
  1994年   62篇
  1993年   57篇
  1992年   68篇
  1991年   75篇
  1990年   64篇
  1989年   48篇
  1988年   34篇
  1987年   39篇
  1986年   61篇
  1985年   42篇
  1984年   34篇
  1983年   32篇
  1982年   23篇
  1981年   19篇
  1980年   20篇
  1979年   19篇
  1978年   12篇
  1977年   14篇
  1975年   21篇
  1974年   12篇
  1971年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Graefe's Archive for Clinical and Experimental Ophthalmology - To estimate the impact of delayed care during the coronavirus disease 2019 (COVID-19) pandemic on the outcomes of patients with...  相似文献   
3.
4.
5.
Cholangiocarcinoma(CCA) is a malignant tumor of the biliary system and includes, according to the anatomical classification, intra hepatic CCA(iCCA),hilar CCA(hCCA) and distal CCA(dCCA). Hilar CCA is the most challenging type in terms of diagnosis, treatment and prognosis. Surgery is the only treatment possibly providing long-term survival, but only few patients are considered resectable at the time of diagnosis. In fact, tumor's extension to segmentary or subsegmentary biliary ducts, along with large lymph node involvement or intrahepatic metastases, precludes the surgical approach. To achieve R0 margins is mandatory for the disease-free survival and overall survival. In case of unresectable locally advanced hCCA, radiochemotherapy(RCT) as neoadjuvant treatment demonstrated to be a therapeutic option before either hepatic resection or liver transplantation. Before liver surgery, RCT is believed to enhance the R0 margins rate. For patients meeting the Mayo Clinic criteria, RCT prior to orthotopic liver transplant(OLT) has proved to produce acceptable 5-years survivals. In this review, we analyze the current role of neoadjuvant RCT before resection as well as before OLT.  相似文献   
6.
BACKGROUND: The activity and isoenzyme composition of N-acetyl-beta-D-hexosaminidase (EC.3.2.1.52) in seminal plasma of fertile and infertile men have been evaluated. However, no data are available on the isoenzyme content in seminal plasma from patients with secretory azoospermia. METHODS: The activity and isoenzyme composition of seminal plasma from 15 normozoospermic controls and 18 patients with secretory azoospermia were determined by fluorimetric methods. 4-Methylumbelliferil-2-acetamido-2-deoxy-beta-D-glucopyranoside and 4-methylumbelliferil-2-acetamido-2-deoxy-beta-D-glucopyranoside-6-sulfate were used as fluorigenic substrates. Receiver-operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic efficiency of the assays. RESULTS: No significant difference was found in total enzyme activity between the two groups, while isoenzyme A activity was significantly lower (p=0.004) and the ratio between total enzyme activity and isoenzyme A activity was significantly higher (p=0.04) in azoospermic patients compared to controls. The diagnostic efficiency of these evaluations was low (< or =75.7%). CONCLUSIONS: Our findings show that the isoenzyme composition of N-acetyl-beta-D-hexosaminidase in seminal plasma from patients with secretory azoospermia is significantly different from controls, but this difference does not represent a useful marker of secretory azoospermia. The fluorimetric assays are simple and rapid methods for evaluating the isoenzyme composition.  相似文献   
7.
8.
The application of a circular dichroism (c.d.) detection system in HPLC using a chiral stationary phase is presented. The simultaneous measurement of the absorbance and c.d. signal allows the evaluation of the anisotropy factor (g = Δ/) and thus the determination of the enantiomeric excess (e.e.) of the eluates. When this detection system is used in preparative chiral chromatography the collection of the enantiomeric fractions can be readily optimized.  相似文献   
9.
BACKGROUND: Cardiac magnetic resonance (MR) images are often reviewed by non-cardiologists who are not trained in the interpretation of regional left ventricular (LV) function. We hypothesized that the use of still-frame parametric MR images of wall motion could aid in the assessment of regional LV function. METHODS: Dynamic, electrocardiogram-gated, steady-state free precession (FIESTA) short-axis images were obtained in 6 to 10 slices in 18 consecutive patients. Each loop was used to automatically generate a still-frame image, in which each pixel is assigned a value equal to the amplitude of cyclic variation in local intensity, resulting in higher intensity in pixels that change between blood and tissue during the cardiac cycle. The dynamic images were reviewed by an expert cardiologist who provided gold standard grades for regional wall motion and by four radiologists. Then the radiologists reviewed and graded the same MR images in combination with parametric images. Grades assigned to each segment in the two sessions were compared with the gold standard. RESULTS: According to expert interpretation, 6 patients had normal wall motion, and 12 had wall motion abnormalities. Parametric images showed a bright band in the area spanned by endocardial motion, with reduced brightness and thickness in areas of hypokinesis. The agreement between the radiologists' grades and the gold standard significantly improved by adding parametric images (from 77% to 81%), which also resulted in reduced interobserver variability (from 52% to 33%). CONCLUSIONS: Still-frame parametric images aid in the assessment of regional wall motion by non-cardiologists who are required to interpret cardiac images.  相似文献   
10.
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