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   18017篇
  免费   795篇
  国内免费   21篇
电工技术   213篇
综合类   18篇
化学工业   3526篇
金属工艺   328篇
机械仪表   400篇
建筑科学   1008篇
矿业工程   49篇
能源动力   504篇
轻工业   1685篇
水利工程   120篇
石油天然气   52篇
武器工业   1篇
无线电   1619篇
一般工业技术   3123篇
冶金工业   3125篇
原子能技术   190篇
自动化技术   2872篇
  2023年   140篇
  2022年   100篇
  2021年   456篇
  2020年   347篇
  2019年   371篇
  2018年   430篇
  2017年   391篇
  2016年   498篇
  2015年   427篇
  2014年   527篇
  2013年   1094篇
  2012年   867篇
  2011年   1130篇
  2010年   778篇
  2009年   835篇
  2008年   871篇
  2007年   774篇
  2006年   708篇
  2005年   597篇
  2004年   501篇
  2003年   449篇
  2002年   424篇
  2001年   307篇
  2000年   323篇
  1999年   354篇
  1998年   762篇
  1997年   490篇
  1996年   394篇
  1995年   279篇
  1994年   262篇
  1993年   259篇
  1992年   174篇
  1991年   148篇
  1990年   140篇
  1989年   139篇
  1988年   122篇
  1987年   116篇
  1986年   111篇
  1985年   140篇
  1984年   127篇
  1983年   119篇
  1982年   86篇
  1981年   99篇
  1980年   84篇
  1979年   96篇
  1978年   85篇
  1977年   113篇
  1976年   140篇
  1975年   77篇
  1974年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
This article describes the development and validation of scales to measure clients' outcome optimism, perceived progress, and self-agency related to change in problems presented in therapy. In Study 1, initial confirmatory and subsequent exploratory factor analyses (N?=?257) identified effort and persistence as an additional unique factor and guided selection of items to measure the 4 constructs. In Study 2, confirmatory factor analysis of the revised scales with a new sample (N?=?93) confirmed the measurement model. Results of convergent and discriminant validity analyses generally were in the predicted directions. The Perceived Progress scale demonstrated criterion validity with changes in dyadic adjustment and family functioning. The Outcome Optimism and Self-Agency scales showed variability in their relationship to the Perceived Progress scale over the first 3 sessions of therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
The kinetics of cyclotrimerization and the thermal stability of bisphenol Abased cyanate ester resin systems were determined using Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetry. The bisphenol A dicyanate was cured with 4 phr nonylphenol and with the octoates of zinc and manganese, and cobalt acetylacetonate at concentrations ranging from 0 to 750 ppm metal. An empirical rate law was used to predict the cyanate concentration profiles. The observed reaction rate showed a first-order dependen?e on the initial metal concentration and a second-order dependence on the cyanate concentration in the kinetically controlled regime. For the uncatalyzed systems, the kinetics was described by a second-order autocatalytic model. The thermal stability of the network was found to be dependent on the catalyst concentration for the zinc catalysts. For the samples cured with manganese, no effect of concentration on the thermal stability was observed.  相似文献   
103.
The typical inventory routing problem deals with the repeated distribution of a single product from a single facility with an unlimited supply to a set of customers that can all be reached with out-and-back trips. Unfortunately, this is not always the reality. We introduce the inventory routing problem with continuous moves to study two important real-life complexities: limited product availabilities at facilities and customers that cannot be served using out-and-back tours. We need to design delivery tours spanning several days, covering huge geographic areas, and involving product pickups at different facilities. We develop an innovative randomized greedy algorithm, which includes linear programming based postprocessing technology, and we demonstrate its effectiveness in an extensive computational study.  相似文献   
104.
Potential applications of knowledge based expert systems in the area of construction project monitoring and control are described. Originally developed from research in artificial intelligence, these systems are computer programs that can undertake intelligent tasks currently performed by highly skilled people. While some project monitoring can be accomplished by algorithmic procedures, the capability of knowledge based expert systems to deal with illstructured problems and to be extensively modified over time make them desirable for application in this area. Sample applications and heuristic rules in scheduling and inventory control are provided.  相似文献   
105.
Datenschutzmanagement ist eine gesetzlich verankerte Aufgabe, muss sich aber unter Wirtschaftlichkeitsgesichtspunkten in der betrieblichen und zunehmend auch der behördlichen Praxis in andere, bereits etablierte Prozessmanagementstrukturen wie ITIL oder Informationssicherheits-management Systeme (ISMS) einordnen. In diesem Beitrag werden die Möglichkeiten untersucht, die IT-Grundschutz als ein zukünftiges, ISO 27001-kompatibles ISMS bietet. Unter dem Gesichtspunkt der Normierung scheint eine Aktualisierung des Bausteins 3.5 “Datenschutz” dringend.  相似文献   
106.
Publications on optimal control of irreversible thermodynamic processes are reviewed. Analogies between irreversible processes in thermodynamics and microeconomics are stated.  相似文献   
107.
108.
Outage in digital microwave radio systems during multipath fading is highly correlated with the channel amplitude dispersion. This characteristic is exploited in a new digital microwave radio system measurement technique which yields dispersion signatures. These dispersion signatures can be readily applied to assess the effects of time varying channels on digital radio equipment. Thus, dispersion signatures can be used for in-service monitoring of equipment operation during actual fading. Routine maintenance assessment and laboratory evaluation of digital microwave radio equipment can also be readily carried out. The laboratory evaluation results can be used for system design both with and without diversity.  相似文献   
109.
XML-Schema     
XML hat sich als Sprache zur Definition von Dokumenten für den universellen Datenaustausch etabliert. XML-Schema erm?glicht ausgefeilte Definitionen für XML-Dokumente und hat beste Chancen, die bisher eingesetzte DTD abzul?sen. Neben einer allgemeinen Einführung geht dieser Beitrag auch auf verfügbare Produkte und neue M?glichkeiten der objektorientierten Softwareentwicklung mit XML-Schema ein. Vorschl?ge an Prof. Dr. Frank Puppe <puppe@informatik.uni-wuerzburg.de> oder Dieter Steinbauer <dieter.steinbauer@schufa.de> Alle „Aktuellen Schlagw?rter” seit 1988 finden Sie unter: www.ai-wuerzburg.de/as  相似文献   
110.
The development and integration of available current methods and the development of new methods for an adaptive finite element analysis of metal forming processes are presented. The analysis includes large-strain, elastic–plastic, and thermal effects. Many numerical methods such as mesh generation, simulation of the contact between the workpiece and tool and die, and optimization of the finite element mesh are integrated and incorporated. In addition, an algorithm is developed which can detect certain severely distorted elements where the area of integration is approaching zero. The advantage of correcting these regions of locally distorted elements is demonstrated. These numerical methods are implemented in a finite element program developed for simulating metal forming processes, with the emphasis on automating the analysis. Examples include an axisymmetric stress simulation of a coldheading process, a plane strain simulation of an extrusion process and a plane strain simulation of orthogonal metal cutting, all with noticeable thermal effects. The orthogonal cutting forces and feed forces calculated are compared with two sets of experimental data, with good agreement.  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