全文获取类型
收费全文 | 20953篇 |
免费 | 570篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 278篇 |
综合类 | 16篇 |
化学工业 | 3899篇 |
金属工艺 | 314篇 |
机械仪表 | 378篇 |
建筑科学 | 1220篇 |
矿业工程 | 117篇 |
能源动力 | 585篇 |
轻工业 | 1597篇 |
水利工程 | 179篇 |
石油天然气 | 205篇 |
武器工业 | 1篇 |
无线电 | 1513篇 |
一般工业技术 | 3269篇 |
冶金工业 | 5137篇 |
原子能技术 | 194篇 |
自动化技术 | 2649篇 |
出版年
2022年 | 130篇 |
2021年 | 242篇 |
2020年 | 186篇 |
2019年 | 247篇 |
2018年 | 289篇 |
2017年 | 285篇 |
2016年 | 345篇 |
2015年 | 259篇 |
2014年 | 417篇 |
2013年 | 1229篇 |
2012年 | 739篇 |
2011年 | 961篇 |
2010年 | 748篇 |
2009年 | 737篇 |
2008年 | 948篇 |
2007年 | 958篇 |
2006年 | 776篇 |
2005年 | 790篇 |
2004年 | 635篇 |
2003年 | 634篇 |
2002年 | 575篇 |
2001年 | 405篇 |
2000年 | 351篇 |
1999年 | 379篇 |
1998年 | 590篇 |
1997年 | 464篇 |
1996年 | 436篇 |
1995年 | 411篇 |
1994年 | 334篇 |
1993年 | 379篇 |
1992年 | 312篇 |
1991年 | 205篇 |
1990年 | 277篇 |
1989年 | 319篇 |
1988年 | 231篇 |
1987年 | 256篇 |
1986年 | 260篇 |
1985年 | 316篇 |
1984年 | 308篇 |
1983年 | 262篇 |
1982年 | 256篇 |
1981年 | 242篇 |
1980年 | 200篇 |
1979年 | 207篇 |
1978年 | 199篇 |
1977年 | 219篇 |
1976年 | 217篇 |
1975年 | 195篇 |
1974年 | 176篇 |
1973年 | 157篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
The Intellectual Development of Science and Engineering Students. Part 2: Teaching to Promote Growth
As college students experience the challenges of their classes and extracurricular activities, they undergo a developmental progression in which they gradually relinquish their belief in the certainty of knowledge and the omniscience of authorities and take increasing responsibility for their own learning. At the highest developmental level normally seen in college students (which few attain before graduation), they display attitudes and thinking patterns resembling those of expert scientists and engineers, including habitually and skillfully gathering and analyzing evidence to support their judgments. This paper proposes an instructional model designed to provide a suitable balance of challenge and support to advance students to that level. The model components are (1) variety and choice of learning tasks; (2) explicit communication and explanation of expectations; (3) modeling, practice, and constructive feedback on high‐level tasks; (4) a student‐centered instructional environment; and (5) respect for students at all levels of development. 相似文献
22.
Life is pleasant--and memory helps to keep it that way! 总被引:1,自引:0,他引:1
Walker W. Richard; Skowronski John J.; Thompson Charles P. 《Canadian Metallurgical Quarterly》2003,7(2):203
People's recollections of the past are often positively biased. This bias has 2 causes. The 1st cause lies in people's perceptions of events. The authors review the results of several studies and present several new comparative analyses of these studies, all of which indicate that people perceive events in their lives to more often be pleasant than unpleasant. A 2nd cause is the fading affect bias: The affect associated with unpleasant events fades faster than the affect associated with pleasant events. The authors review the results of several studies documenting this bias and present evidence indicating that dysphoria (mild depression) disrupts such bias. Taken together, this evidence suggests that autobiographical memory represents an important exception to the theoretical claim that bad is stronger than good. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
24.
A key performance parameter of a manufacturing network or supply chain is its cycle time; the time that a typical item spends in the network. A previous simulation study on a semiconductor assembly and test facility showed that cycle times could be reduced by having smooth input and service rates. This suggested that there is a “cycle time principle” that, for a system with a specified throughput or input rate, the shortest cycle times are obtained when the input and service rates do not vary over time. We prove that this principle is true for the M/G/1 and M/M/s queueing systems and Jackson networks. The analysis involves establishing several results on the concavity of waiting time probabilities and the convexity of expected waiting times and queue lengths, as functions of input and service rates. These results also have natural uses in other optimization problems. 相似文献
25.
可重定位的基于事务的系统级验证 总被引:2,自引:0,他引:2
功能验证已经成为开发SoC的主要问题。随着一些复杂SoC的规模超过两千万门,以及对开发和集成嵌入式软件的需求持续增加,软件模拟器已经力所不及。在设计过程需要几百万个时钟周期来充分测试和验证软件功能的情况下,软件仿真器的性能下降到1-5Hz。按照这种速率,软件调试需要几年的时 相似文献
26.
Fertuck Eric A.; Bucci Wilma; Blatt Sidney J.; Ford Richard Q. 《Canadian Metallurgical Quarterly》2004,41(1):13
This study examined the relation between changes in clinical functioning and changes in verbal expression in 81 seriously disturbed and treatment-resistant young adults seen in a comprehensive, psychoanalytically oriented inpatient treatment. Clinical functioning was evaluated with a battery of clinical and social measures. Verbal representations were assessed using computer-assisted scoring of Thematic Apperception Test responses. Changes in the frequency of verbal content and style in the narratives of these patients covaried with changes in clinical functioning. Significantly different covariations of verbal and clinical change, particularly differences in covariates of referential activity, were found for patients with anaclitic versus introjective personality configurations. The implications of these findings for understanding and treating severe psychopathology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal 相似文献
28.
Test Case Generation as an AI Planning Problem 总被引:6,自引:0,他引:6
Adele E. Howe Anneliese von Mayrhauser Richard T. Mraz 《Automated Software Engineering》1997,4(1):77-106
While Artificial Intelligence techniques have been applied to a variety of software engineering applications, the area of automated software testing remains largely unexplored. Yet, test cases for certain types of systems (e.g., those with command language interfaces and transaction based systems) are similar to plans. We have exploited this similarity by constructing an automated test case generator with an AI planning system at its core. We compared the functionality and output of two systems, one based on Software Engineering techniques and the other on planning, for a real application: the StorageTek robot tape library command language. From this, we showed that AI planning is a viable technique for test case generation and that the two approaches are complementary in their capabilities. 相似文献
29.
Richard Ross 《Information Systems Management》1994,11(3):41-50
Management of distributed environments requires corporate IS managers to shift from being operators of a central utility to facilitators who can recognize the synergy among loosely related groups of users. Success depends on the development of new ways of visualizing and measuring the service delivery process. 相似文献
30.
F. Cioffi E. M. Cohen Richard Badick 《Drug development and industrial pharmacy》1993,19(14):1741-1746
Carstensen and Rhodes1 have suggested that when, in stability programs, assays cannot be performed immediately after the protocol-designated storage time, then freezing them until such a time when assays can be performed would be a reasonable manner to retain the protocol schedule. They caution, however, that such a procedure may not be valid for dissolution data. The article to follow deals with real-time data showing that such a process is feasible for Nalidixic Acid tablets (and presumably for other tablets as well), and that, furthermore, the dissolution pattern would seem to be “frozen” as well. 相似文献