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   107238篇
  免费   1859篇
  国内免费   438篇
电工技术   1080篇
综合类   2352篇
化学工业   16844篇
金属工艺   5120篇
机械仪表   3480篇
建筑科学   3428篇
矿业工程   656篇
能源动力   1712篇
轻工业   5418篇
水利工程   1490篇
石油天然气   412篇
无线电   10958篇
一般工业技术   20537篇
冶金工业   7109篇
原子能技术   448篇
自动化技术   28491篇
  2023年   214篇
  2022年   359篇
  2021年   567篇
  2020年   340篇
  2019年   434篇
  2018年   14822篇
  2017年   13714篇
  2016年   10466篇
  2015年   1152篇
  2014年   962篇
  2013年   1598篇
  2012年   4248篇
  2011年   10767篇
  2010年   9257篇
  2009年   6478篇
  2008年   7811篇
  2007年   8753篇
  2006年   1049篇
  2005年   1948篇
  2004年   1854篇
  2003年   1803篇
  2002年   1086篇
  2001年   521篇
  2000年   536篇
  1999年   456篇
  1998年   801篇
  1997年   579篇
  1996年   482篇
  1995年   419篇
  1994年   388篇
  1993年   370篇
  1992年   280篇
  1991年   217篇
  1990年   268篇
  1989年   260篇
  1988年   224篇
  1987年   224篇
  1986年   226篇
  1985年   265篇
  1984年   224篇
  1983年   223篇
  1982年   207篇
  1981年   194篇
  1980年   168篇
  1979年   193篇
  1978年   164篇
  1977年   185篇
  1976年   234篇
  1975年   160篇
  1974年   123篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Custom software development and maintenance is one of the key expenses associated with developing automated systems for mass customization. This paper presents a method for reducing the risk associated with this expense by developing a flexible environment for determining and executing dynamic workflow paths. Strategies for developing an autonomous agent-based framework and for identifying and creating web services for specific process tasks are presented. The proposed methods are outlined in two different case studies to illustrate the approach for both a generic process with complex workflow paths and a more specific sequential engineering process.  相似文献   
942.
For two propositional fuzzy logics, we present analytic proofcalculi, based on relational hypersequents. The logic consideredfirst, called M, is based on the finite ordinal sums of ukasiewiczt-norms. In addition to the usual connectives—the conjunction, the implication and the constant 0—we use a furtherunary connective interpreted by the function associating witheach truth value a the greatest -idempotent below a. M is aconservative extension of Basic Logic. The second logic, called M, is based on the finite ordinal sumsof the product t-norm on (0, 1]. Our connectives are in thiscase just the conjunction and the implication.  相似文献   
943.
Recent advances in microtechnology allow realization of planar microcoils. These components are integrated in MEMS as magnetic sensor or actuator. In the latter case, it is necessary to maximize the effective magnetic field which is proportional to the current passing through the copper track and depends on the distance to the generation microcoil. The aim of this work was to determine the optimal microcoil design configuration for magnetic field generation. The results were applied to magnetic actuation, taking into account technological constraints. In particular, we have considered different realistic configurations that involve a magnetically actuated device coupled to a microcoil. Calculations by a semi-analytical method using Matlab software were validated by experimental measurements. The copper planar microcoils are fabricated by UV micromoulding on different substrates: flexible polymer (Kapton®) and silicate on silicon. They are constituted by a spiral-like continuous track. Their total surface is about 1 mm2.  相似文献   
944.
There is an increasing use of computer media for negotiations. However, the use of computer-mediated channels increases the hostile expressions of emotion, termed flaming. Although researchers agree that flaming has important effects on negotiation, predictions concerning these effects are inconsistent, suggesting a need for further investigation. We address this need by extending current flaming and negotiation research in two ways. First, we identify two different types of flaming: that which is motivated by perceptions concerning the negotiating opponent (e.g., he/she is unfair) and that which is motivated by perceptions concerning the negotiating context (e.g., the communication channel is too slow). Second, we differentiate between the effects of flaming on the concession behaviors of the flame sender and the flame recipient, and the effects of these behaviors on negotiated agreement. Via a laboratory study, we demonstrate that flames directed at the negotiation opponent slightly decrease the likelihood of reaching an agreement, and when an agreement is reached, it result in outcomes significantly favoring the flame recipient rather than the flame sender. In contrast, flames directed at the negotiation context significantly increase the likelihood of agreement, although outcomes still favor the flame recipient over the flame sender. These results suggest that flame senders are generally worse off than flame recipients, which provides an important basis for the strategic use of flaming in negotiations.  相似文献   
945.
About 20 years ago, Markus and Robey noted that most research on IT impacts had been guided by deterministic perspectives and had neglected to use an emergent perspective, which could account for contradictory findings. They further observed that most research in this area had been carried out using variance theories at the expense of process theories. Finally, they suggested that more emphasis on multilevel theory building would likely improve empirical reliability. In this paper, we reiterate the observations and suggestions made by Markus and Robey on the causal structure of IT impact theories and carry out an analysis of empirical research published in four major IS journals, Management Information Systems Quarterly (MISQ), Information Systems Research (ISR), the European Journal of Information Systems (EJIS), and Information and Organization (I&O), to assess compliance with those recommendations. Our final sample consisted of 161 theory-driven articles, accounting for approximately 21% of all the empirical articles published in these journals. Our results first reveal that 91% of the studies in MISQ, ISR, and EJIS focused on deterministic theories, while 63% of those in I&O adopted an emergent perspective. Furthermore, 91% of the articles in MISQ, ISR, and EJIS adopted a variance model; this compares with 71% from I&O that applied a process model. Lastly, mixed levels of analysis were found in 14% of all the surveyed articles. Implications of these findings for future research are discussed.  相似文献   
946.
Since DeLone and McLean (D&M) developed their model of IS success, there has been much research on the topic of success as well as extensions and tests of their model. Using the technique of a qualitative literature review, this research reviews 180 papers found in the academic literature for the period 1992–2007 dealing with some aspect of IS success. Using the six dimensions of the D&M model – system quality, information quality, service quality, use, user satisfaction, and net benefits – 90 empirical studies were examined and the results summarized. Measures for the six success constructs are described and 15 pairwise associations between the success constructs are analyzed. This work builds on the prior research related to IS success by summarizing the measures applied to the evaluation of IS success and by examining the relationships that comprise the D&M IS success model in both individual and organizational contexts.  相似文献   
947.
In the 1990s, enrollments grew rapidly in information systems (IS) and computer science. Then, beginning in 2000 and 2001, enrollments declined precipitously. This paper looks at the enrollment bubble and the dotcom bubble that drove IT enrollments. Although the enrollment bubble occurred worldwide, this paper focuses primarily on U.S. data, which is widely available, and secondarily on Western Europe data. The paper notes that the dotcom bubble was an investment disaster but that U.S. IT employment fell surprisingly little and soon surpassed the bubble's peak IT employment. In addition, U.S. IT unemployment rose to almost the level of total unemployment in 2003, then fell to traditional low levels by 2005. Job prospects in the U.S. and most other countries are good for the short term, and the U.S. Bureau of Labor Statistics employment projections for 2006–2016 indicate that job prospects in the U.S. will continue to be good for most IT jobs. However, offshoring is a persistent concern for students in Western Europe and the United States. The data on offshoring are of poor quality, but several studies indicate that IT job losses from offshoring are small and may be counterbalanced by gains in IT inshoring jobs. At the same time, offshoring and productivity gains appear to be making low-level jobs such as programming and user support less attractive. This means that IS and computer science programs will have to focus on producing higher-level job skills among graduates. In addition, students may have to stop considering the undergraduate degree to be a terminal degree in IS and computer science.  相似文献   
948.
949.
Category Partition Method (CPM) is a general approach to specification-based program testing, where test frame reduction and refinement are two important issues. Test frame reduction is necessary since too many test frames may be produced, and test frame refinement is important since during CPM testing new information about test frame generation may be achieved and considered incrementally. Besides the information provided by testers or users, implementation related knowledge offers alternative information for reducing and refining CPM test frames. This paper explores the idea by proposing a call patterns semantics based test frame updating method for Prolog programs, in which a call patterns analysis is used to collect information about the way in which procedures are used in a program. The updated test frames will be represented as constraints. The effect of our test frame updating is two-fold. On one hand, it removes “uncared” data from the original set of test frames; on the other hand, it refines the test frames to which we should pay more attention. The first effect makes the input domain on which a procedure must be tested a subset of the procedure’s input domain, and the latter makes testers stand more chance to find out the faults that are more likely to show their presence in the use of the program under consideration. Our test frame updating method preserves the effectiveness of CPM testing with respect to the detection of faults we care. The test case generation from the updated set of test frames is also discussed. In order to show the applicability of our method an approximation call patterns semantics is proposed, and the test frame updating on the semantics is illustrated by an example.
Lingzhong ZhaoEmail:
  相似文献   
950.
Statistical process control (SPC) is a conventional means of monitoring software processes and detecting related problems, where the causes of detected problems can be identified using causal analysis. Determining the actual causes of reported problems requires significant effort due to the large number of possible causes. This study presents an approach to detect problems and identify the causes of problems using multivariate SPC. This proposed method can be applied to monitor multiple measures of software process simultaneously. The measures which are detected as the major impacts to the out-of-control signals can be used to identify the causes where the partial least squares (PLS) and statistical hypothesis testing are utilized to validate the identified causes of problems in this study. The main advantage of the proposed approach is that the correlated indices can be monitored simultaneously to facilitate the causal analysis of a software process.
Chih-Ping ChuEmail:

Ching-Pao Chang   is a PhD candidate in Computer Science & Information Engineering at the National Cheng-Kung University, Taiwan. He received his MA from the University of Southern California in 1998 in Computer Science. His current work deals with the software process improvement and defect prevention using machine learning techniques. Chih-Ping Chu   is Professor of Software Engineering in Department of Computer Science & Information Engineering at the National Cheng-Kung University (NCKU) in Taiwan. He received his MA in Computer Science from the University of California, Riverside in 1987, and his Doctorate in Computer Science from Louisiana State University in 1991. He is especially interested in parallel computing and software engineering.   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