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   4632篇
  免费   279篇
  国内免费   19篇
耳鼻咽喉   22篇
儿科学   135篇
妇产科学   110篇
基础医学   720篇
口腔科学   69篇
临床医学   463篇
内科学   899篇
皮肤病学   222篇
神经病学   559篇
特种医学   156篇
外科学   364篇
综合类   19篇
现状与发展   1篇
一般理论   1篇
预防医学   465篇
眼科学   74篇
药学   255篇
中国医学   17篇
肿瘤学   379篇
  2024年   10篇
  2023年   41篇
  2022年   87篇
  2021年   155篇
  2020年   101篇
  2019年   141篇
  2018年   153篇
  2017年   104篇
  2016年   142篇
  2015年   139篇
  2014年   216篇
  2013年   256篇
  2012年   380篇
  2011年   382篇
  2010年   229篇
  2009年   205篇
  2008年   291篇
  2007年   288篇
  2006年   311篇
  2005年   294篇
  2004年   256篇
  2003年   215篇
  2002年   176篇
  2001年   28篇
  2000年   23篇
  1999年   26篇
  1998年   32篇
  1997年   23篇
  1996年   29篇
  1995年   22篇
  1994年   17篇
  1993年   11篇
  1992年   9篇
  1991年   6篇
  1990年   5篇
  1988年   9篇
  1987年   11篇
  1986年   7篇
  1985年   11篇
  1984年   8篇
  1983年   4篇
  1981年   8篇
  1980年   4篇
  1975年   5篇
  1974年   5篇
  1973年   5篇
  1972年   4篇
  1971年   4篇
  1968年   4篇
  1963年   5篇
排序方式: 共有4930条查询结果,搜索用时 15 毫秒
81.
Upper limb function impairment is one of the most common sequelae of central nervous system in jury, especially in stroke patients and when spinal cord injury produces tetraplegia. Conventional assessment methods cannot provide objective evaluation of patient performance and the effec tiveness of therapies. The most common assessment tools are based on rating scales, which are inefficient when measuring small changes and can yield subjective bias. In this study, we designed an inertial sensorbased monitoring system composed of five sensors to measure and analyze the complex movements of the upper limbs, which are common in activities of daily living. We devel oped a kinematic model with nine degrees of freedom to analyze upper limb and head movements in three dimensions. This system was then validated using a commercial optoelectronic system. These findings suggest that an inertial sensorbased motion tracking system can be used in patients who have upper limb impairment through data integration with a virtual realitybased neurorehabili tation system.  相似文献   
82.
We developed microsatellite loci for the Julimes pupfish, Cyprinodon julimes. Twenty-five loci were screened across 19 individuals from Julimes Spring, Chihuahua, Mexico. The number of alleles per locus ranged from 2 to 14, observed heterozygosity ranged from 0.105 to 0.947, and the probability of identity values ranged from 0.022 to 0.588. We then tested for cross-amplification in the bighead pupfish, C. pachycephalus; twenty-three individuals from San Diego de Alcalá, Chihuahua, Mexico, were screened across the 20 loci that amplified cleanly. These new loci will be used for long-term genetic monitoring of these critically endangered species.  相似文献   
83.
84.
This study aims at investigating attention and impulsivity differences between borderline personality disorder and bipolar disorder, as both diseases may share neuropsychological deficits. Differential cognitive outcomes on the Continuous Performance Test-II were observed between disorders, and also when compared to healthy controls.  相似文献   
85.
Background: The psychosis phenotype appears to exist in the population as a continuum, but it is not clear if subclinical psychotic symptoms and psychotic disorders share the same neurobiology. We investigated whether the dopaminergic dysfunction seen in psychotic disorders is also present in healthy, well-functioning people with hallucinations. Methods: We compared dopamine synthesis capacity (using 6-[18F]fluoro-L-DOPA [[18F]-DOPA] positron emission tomography imaging) in 16 healthy individuals with frequent persistent auditory verbal hallucinations (hallucinating group) with that in 16 matched controls. Results: There was no significant difference in dopamine synthesis capacity in the striatum, or its functional subdivisions, between groups and no relationship between subclinical psychotic symptom severity or schizotypal traits and dopamine synthesis capacity in the hallucinating group. Conclusions: Altered dopamine synthesis capacity is unlikely to underlie subclinical hallucinations, suggesting that although there may be a phenomenological psychosis continuum, there are distinctions at the neurobiological level.  相似文献   
86.
87.
88.
89.
90.
Context: Traditionally, the content of total phenolics (flavonoid phenolics (FP) and non-flavonoid phenolics (NFP)) and flavonoids (flavone/flavonol and flavonone/dihydroflavonol) in propolis has been determined by different methodologies. Until now, the percentage of total phenolic (TP) compounds that corresponds to FP and NFP, expressed in the same units by a spectrophotometric method, has not been determined.

Objective: The current study proposes a quick and simple methodology that separates FP and NFP in propolis samples and determines TP, FP, and NFP by the same method.

Materials and methods: Propolis samples from five Argentine provinces (Tucumán, Santiago del Estero, Salta, Misiones, and Jujuy) were used. Extraction of TP from the propolis samples was carried out by maceration with 80% ethanol and quantified by Folin–Ciocalteu reagent (FC-R). Then, FP was precipitated with formaldehyde in acid medium. After centrifugation, NFP were determined in the supernatant using FC-R. FP content was calculated as the difference between the content of TP and NFP. The method was also validated using commercial flavonoids and chalcones.

Results: FP recovery in all experiments was between 85.95% and 98.29%. Propolis from Tucumán had significantly higher amounts of total phenols than propolis from other provinces. SE5 showed higher content of FP (81.52%) followed by SA1 (74.75%). The propolis from TUC4, SA4, SE3, and MI showed the lowest FP content and highest content of NFP.

Conclusions: This method provides a simple, reliable, and specific spectrophotometric assay to estimate the content of NFP, FP, and TP in propolis samples.  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