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   2420篇
  免费   130篇
  国内免费   11篇
耳鼻咽喉   34篇
儿科学   133篇
妇产科学   28篇
基础医学   260篇
口腔科学   95篇
临床医学   185篇
内科学   490篇
皮肤病学   41篇
神经病学   99篇
特种医学   88篇
外科学   334篇
综合类   40篇
一般理论   1篇
预防医学   163篇
眼科学   146篇
药学   202篇
中国医学   9篇
肿瘤学   213篇
  2023年   22篇
  2022年   56篇
  2021年   89篇
  2020年   41篇
  2019年   59篇
  2018年   73篇
  2017年   40篇
  2016年   54篇
  2015年   85篇
  2014年   87篇
  2013年   94篇
  2012年   168篇
  2011年   152篇
  2010年   95篇
  2009年   96篇
  2008年   130篇
  2007年   154篇
  2006年   114篇
  2005年   99篇
  2004年   99篇
  2003年   89篇
  2002年   76篇
  2001年   50篇
  2000年   60篇
  1999年   50篇
  1998年   24篇
  1997年   20篇
  1996年   24篇
  1995年   12篇
  1994年   11篇
  1993年   15篇
  1992年   46篇
  1991年   27篇
  1990年   27篇
  1989年   15篇
  1988年   17篇
  1987年   13篇
  1986年   12篇
  1985年   17篇
  1984年   15篇
  1983年   12篇
  1982年   9篇
  1981年   7篇
  1980年   11篇
  1979年   7篇
  1975年   9篇
  1974年   7篇
  1972年   12篇
  1971年   6篇
  1966年   5篇
排序方式: 共有2561条查询结果,搜索用时 31 毫秒
91.

Background

Abdominal epilepsy (AE) is an infrequent cause of recurrent abdominal pain in children. It is characterized by paroxysmal episodes of abdominal pain, a variety of other abdominal complaints, electroencephalogram abnormalities, and response to anti-epileptic agents. We described the clinical profile of six patients with AE.

Methods

We conducted a retrospective survey of AE in children from the records of the hospital. The diagnosis of AE was dependent on recurrent abdominal symptoms, subtle central nervous system abnormalities, electroencephalogram abnormalities and response to anticonvulsant agents.

Results

The six patients were diagnosed with AE. The incidence of the disease was 0.07% in all admissions to the pediatric ward. Recurrent pain was common in all patients except two who had additional recurrent vomiting. In this series, the boy to girl ratio (1:2) was unequal.

Conclusion

High suspicion is required for the diagnosis of AE after exclusion of other possible causes.  相似文献   
92.
93.
The oral pathogen Aggregatibacter actinomycetemcomitans uses pga gene locus for the production of an exopolysaccharide made up of a linear homopolymer of β‐1,6‐N‐acetyl‐d ‐glucosamine (PGA). An enzyme encoded by the pgaB of the pga operon in A. actinomycetemcomitans is a de‐N‐acetylase, which is used to alter the PGA. The full length enzyme (AaPgaB) and the N‐terminal catalytic domain (residues 25–290, AaPgaBN) from A. actinomycetemcomitans were cloned, expressed and purified. The enzymatic activities of the AaPgaB enzymes were determined using 7‐acetoxycoumarin‐3‐carboxylic acid as the substrate. The AaPgaB enzymes displayed significantly lower de‐N‐acetylase activity compared with the activity of the deacetylase PdaA from Bacillus subtilis, a member of the CE4 family of enzymes. To delineate the differences in the activity and the active site architecture, the structure of AaPgaBN was determined. The AaPgaBN structure has two metal ions in the active site instead of one found in other CE4 enzymes. Based on the crystal structure comparisons among the various CE4 enzymes, two residues, Q51 and R271, were identified in AaPgaB, which could potentially affect the enzyme activity. Of the two mutants generated, Q51E and R271K, the variant Q51E showed enhanced activity compared with AaPgaB, validating the requirement that an activating aspartate residue in the active site is essential for higher activity. In summary, our study provides the first structural evidence for a di‐nuclear metal site at the active site of a member of the CE4 family of enzymes, evidence that AaPgaBN is catalytically active and that mutant Q51E exhibits higher de‐N‐acetylase activity.  相似文献   
94.
Objective The aim of this study was to characterize a successful approach for the management of infants with long-gap esophageal atresia (EA) with tracheoesophageal fistula (TEF). The goal was to preserve the native esophagus and minimize the incidence of esophageal anastomotic leaks using fibrin glue as a sealant over the esophageal anastomosis. Method A total of 52 patients were evaluated in this study. Only patients in whom, gap between the two ends of the esophagus was ≥ 2 cm were selected during January 2005 to January 2007. Patients were divided in two groups on the basis of block randomization. Group A comprised the patients in whom fibrin sealant was used as reinforcement on a primary end-to-end esophageal anastomosis; in group B, fibrin glue was not used. The two groups were compared in terms of esophageal anastomotic leak (EL), postoperative esophageal stricture (ES), and mortality. The statistical analysis was done using Fisher’s exact test and the chi-squared test. Result The number of anastomotic leaks in group A (glue group) was about one-fifth that in group B (no glue group). The incidence of ES was almost twice as high in group B as in group A. The mortality rate was almost threefold higher in group B (no-glue group). The higher incidence of EL and ES in group B compared to group A was statistically significant. Conclusion Thus, fibrin glue when used as an adjunct to esophageal anastomosis for primary repair of long-gap EA with TEF appears safe in the clinical setting and may lower the chances of esophageal leak and anastomosis-site strictures. Hence, it can diminish the mortality and morbidity of these patients.  相似文献   
95.
Utilizing a new echocardiographic system, intramyocardial coronary arteries could be demonstrated by color Doppler in a small number of open chest animals. Both intravenous and intracoronary injections of a contrast agent (Levovist) resulted in significant enhancement of color flow signals with an increase in the length, width, and the number of these vessels. Similar results were obtained with intravenous infusion and direct intracoronary injections of a vasodilator (adenosine).  相似文献   
96.
97.
98.
Pancreatic neoplasms have a wide range of pathology, from pancreatic adenocarcinoma to cystic mucinous neoplasms. Endoscopic ultrasound(EUS) with or without fine needle aspiration(FNA) is a helpful diagnostic tool in the work-up of pancreatic neoplasms. Its utility in pancreatic malignancy is well known. Over the last two decades EUS-FNA has become a procedure of choice for diagnosis of pancreatic adenocarcinoma. EUS-FNA is highly sensitive and specific for solid lesions, with sensitivities as high as 80%-95% for pancreatic masses and specificity as high as 75%-100%. Multiple aspects of the procedure have been studied to optimize the rate of diagnosis with EUS-FNA including cytopathologist involvement, needle size, suctioning and experience of endoscopist. Onsite pathology is one of the most important elements in increasing diagnostic yield rate in EUS-FNA. EUS-FNA is valuable in diagnosing rare and atypical pancreatic neoplasms including neuroendocrine, lymphoma and metastatic disease. As more and more patients undergo cross sectional imaging, cystic lesions of the pancreas are becoming a more common occurrence and EUS-FNA of these lesions can be helpful for differentiation. This review covers the technical aspects of optimizing pancreatic neoplasm diagnosis rate, highlight rare pancreatic neoplasms and role of EUS-FNA, and also outline the important factors in diagnosis of cystic lesions by EUS-FNA.  相似文献   
99.
Two DNA probes, 2R1 and 2R3, prepared from a region in the chromosome specific for the lipopolysaccharide O side chains of Vibrio cholerae O139 (M.K. Waldor and J.J. Mekalanos, Lancet 343:1366, 1994) were examined for their specificity and sensitivity. Both probes did not hybridize with any strain of V. cholerae belonging to serogroups other than O139 and to any of the other species examined belonging to the family Vibrionaceae. Among the 126 strains of V. cholerae O139 examined, probe 2R1 hybridized with 125 strains while probe 2R3 hybridized with all 126 strains. Both probes were found to be highly specific and sensitive and can be used for the specific identification of V. cholerae O139.  相似文献   
100.
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