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   1507篇
  免费   230篇
  国内免费   42篇
耳鼻咽喉   5篇
儿科学   17篇
妇产科学   3篇
基础医学   111篇
口腔科学   15篇
临床医学   152篇
内科学   116篇
皮肤病学   13篇
神经病学   47篇
特种医学   33篇
外科学   79篇
综合类   314篇
现状与发展   1篇
预防医学   116篇
眼科学   18篇
药学   199篇
  4篇
中国医学   520篇
肿瘤学   16篇
  2024年   64篇
  2023年   62篇
  2022年   122篇
  2021年   115篇
  2020年   128篇
  2019年   73篇
  2018年   63篇
  2017年   96篇
  2016年   75篇
  2015年   63篇
  2014年   84篇
  2013年   92篇
  2012年   73篇
  2011年   80篇
  2010年   73篇
  2009年   61篇
  2008年   70篇
  2007年   58篇
  2006年   56篇
  2005年   46篇
  2004年   24篇
  2003年   20篇
  2002年   23篇
  2001年   29篇
  2000年   15篇
  1999年   5篇
  1998年   6篇
  1997年   11篇
  1996年   10篇
  1995年   8篇
  1994年   8篇
  1993年   10篇
  1992年   4篇
  1991年   6篇
  1990年   5篇
  1989年   8篇
  1988年   4篇
  1987年   3篇
  1985年   1篇
  1984年   3篇
  1983年   1篇
  1982年   5篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1978年   3篇
  1975年   1篇
  1974年   1篇
  1973年   3篇
  1972年   1篇
排序方式: 共有1779条查询结果,搜索用时 15 毫秒
61.
目的:基于数据挖掘技术探讨中药注射液穴位注射治疗慢性肺系疾病的取穴规律。方法:以中国期刊全文数据库(CNKI)、万方、维普、中国生物医学文献数据库(CBM)为检索库,检索各个数据库自建库以来关于慢性肺系疾病的穴位注射相关文献,建立穴位注射治疗慢性肺系疾病的文献数据库,采用数据挖掘软件对取穴规律进行频数分析、聚类分析、关联分析等。结果:共纳入文献64篇,其中针刺穴位24个,以肺俞使用频率最高(22.66%);涉及经脉10条,主要归足太阳膀胱经和足阳明胃经;主要中药注射液25种,使用频率最多的是黄芪注射液(21.43%)。聚类分析结果并不理想,但由关联分析可见,腧穴配伍多以肺俞为主穴,配以定喘、肾俞、足三里、天突、丰隆等穴。结论:穴位注射治疗慢性肺系疾病在经脉循行上主要选取足太阳膀胱经和足阳明胃经,一般多选用肺俞、定喘、足三里、肾俞等穴位,采用多穴配伍治疗。  相似文献   
62.
田瑾  刘仁权 《中国中药杂志》2015,40(19):3873-3877
基于中医传承辅助系统软件,分析郭蓉娟教授治疗失眠的用药经验。收集郭蓉娟教授治疗失眠的中药方剂,采用关联规则apriori算法、改进的互信息算法、复杂系统熵聚类等无监督数据挖掘方法,确定处方中各种药物的使用频次及药物之间的关联规则,分析郭蓉娟教授治疗失眠的用药经验。对筛选出的3 084首处方进行分析,确定处方中药物的使用频次,药物之问的关联规则,挖掘出41个核心组合和7首新处方。结论符合郭教授对失眠病因病机的认识:以肝郁化火为核心病机,肝郁脾虚、久病及肾的特点,中医传承辅助系统对于挖掘名中医临床经验具有重要实用价值。  相似文献   
63.
The calculation of several common pharmacokinetic parameters requires estimates of both the area under the curve of the concentration of the drug in a sampled fluid vs. time, and also the first moment about t=0 of this area. It is proposed that the methods used to estimate these quantities should make consistent assumptions about the concentration of the drug. There appears to be an inconsistency in the standard published formulas in the case where concentration is interpolated linearly. A more consistent formula is derived.  相似文献   
64.
Index     
  相似文献   
65.
This paper incorporates the hypothesis of labour participation rate into the Ramsey model. It is shown that the economy can be dynamically inefficient if the average productivity of capital is greater than the sum of the rate of time preference, the population growth rate, the depreciation rate and the marginal rate of substitution between labour and consumption. The modified golden rule holds when the wage rate is equal to the marginal rate of substitution between labour and consumption. However, there is no guarantee that it will happen, since labour supply is driven by capital allocation decisions. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
66.
The Gene Ontology (GO), a set of three sub-ontologies, is one of the most popular bio-ontologies used for describing gene product characteristics. GO annotation data containing terms from multiple sub-ontologies and at different levels in the ontologies is an important source of implicit relationships between terms from the three sub-ontologies. Data mining techniques such as association rule mining that are tailored to mine from multiple ontologies at multiple levels of abstraction are required for effective knowledge discovery from GO annotation data. We present a data mining approach, Multi-ontology data mining at All Levels (MOAL) that uses the structure and relationships of the GO to mine multi-ontology multi-level association rules. We introduce two interestingness measures: Multi-ontology Support (MOSupport) and Multi-ontology Confidence (MOConfidence) customized to evaluate multi-ontology multi-level association rules. We also describe a variety of post-processing strategies for pruning uninteresting rules. We use publicly available GO annotation data to demonstrate our methods with respect to two applications (1) the discovery of co-annotation suggestions and (2) the discovery of new cross-ontology relationships.  相似文献   
67.
We are reporting an esoteric method to determine the optical bandgap of direct gap materials by employing Urbach’s rule. The latter, which describes the slope of the band tail absorption in semiconductors, in its original version, cannot be employed to pinpoint the optical bandgap. Herein, however, we show that a modified form of Urbach’s rule defines the optical bandgap, and therefore, enables the accurate determination of the optical bandgap energy, which turns out to be identical with the threshold energy for the band tail absorption. The model further produces an explicit expression for the absorption coefficient at the optical bandgap energy.  相似文献   
68.
The ability to predict and interpret membrane permeation coefficients is of critical importance, particularly because passive transport is crucial for the effective delivery of many pharmaceutical agents to intracellular targets. We present a method for the quantitative measurement of the permeation coefficients of protonophores by using laser confocal scanning microscopy coupled to microelectrochemistry, which is amenable to precise modeling with the finite element method. The technique delivers well defined and high mass transport rates and allows rapid visualization of the entire pH distribution on both the cis and trans side of model bilayer lipid membranes (BLMs). A homologous series of carboxylic acids was investigated as probe molecules for BLMs composed of soybean phosphatidylcholine. Significantly, the permeation coefficient decreased with acyl tail length contrary to previous work and to Overton's rule. The reasons for this difference are considered, and we suggest that the applicability of Overton's rule requires re-evaluation.  相似文献   
69.
In recent years, several hierarchical extensions of well-known learning algorithms have been proposed. For example, when stimulus-action mappings vary across time or context, the brain may learn two or more stimulus-action mappings in separate modules, and additionally (at a hierarchically higher level) learn to appropriately switch between those modules. However, how the brain mechanistically coordinates neural communication to implement such hierarchical learning remains unknown. Therefore, the current study tests a recent computational model that proposed how midfrontal theta oscillations implement such hierarchical learning via the principle of binding by synchrony (Sync model). More specifically, the Sync model uses bursts at theta frequency to flexibly bind appropriate task modules by synchrony. The 64-channel EEG signal was recorded while 27 human subjects (female: 21, male: 6) performed a probabilistic reversal learning task. In line with the Sync model, postfeedback theta power showed a linear relationship with negative prediction errors, but not with positive prediction errors. This relationship was especially pronounced for subjects with better behavioral fit (measured via Akaike information criterion) of the Sync model. Also consistent with Sync model simulations, theta phase-coupling between midfrontal electrodes and temporoparietal electrodes was stronger after negative feedback. Our data suggest that the brain uses theta power and synchronization for flexibly switching between task rule modules, as is useful, for example, when multiple stimulus-action mappings must be retained and used.SIGNIFICANCE STATEMENT Everyday life requires flexibility in switching between several rules. A key question in understanding this ability is how the brain mechanistically coordinates such switches. The current study tests a recent computational framework (Sync model) that proposed how midfrontal theta oscillations coordinate activity in hierarchically lower task-related areas. In line with predictions of this Sync model, midfrontal theta power was stronger when rule switches were most likely (strong negative prediction error), especially in subjects who obtained a better model fit. Additionally, also theta phase connectivity between midfrontal and task-related areas was increased after negative feedback. Thus, the data provided support for the hypothesis that the brain uses theta power and synchronization for flexibly switching between rules.  相似文献   
70.
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