全文获取类型
收费全文 | 37546篇 |
免费 | 3188篇 |
国内免费 | 3160篇 |
专业分类
电工技术 | 3160篇 |
技术理论 | 5篇 |
综合类 | 2454篇 |
化学工业 | 2419篇 |
金属工艺 | 298篇 |
机械仪表 | 1404篇 |
建筑科学 | 1323篇 |
矿业工程 | 185篇 |
能源动力 | 1352篇 |
轻工业 | 451篇 |
水利工程 | 272篇 |
石油天然气 | 231篇 |
武器工业 | 171篇 |
无线电 | 2666篇 |
一般工业技术 | 2951篇 |
冶金工业 | 874篇 |
原子能技术 | 150篇 |
自动化技术 | 23528篇 |
出版年
2024年 | 37篇 |
2023年 | 590篇 |
2022年 | 404篇 |
2021年 | 725篇 |
2020年 | 1005篇 |
2019年 | 1078篇 |
2018年 | 1004篇 |
2017年 | 1367篇 |
2016年 | 1471篇 |
2015年 | 1317篇 |
2014年 | 2246篇 |
2013年 | 3465篇 |
2012年 | 1804篇 |
2011年 | 2296篇 |
2010年 | 1661篇 |
2009年 | 2169篇 |
2008年 | 2162篇 |
2007年 | 2159篇 |
2006年 | 1883篇 |
2005年 | 1690篇 |
2004年 | 1420篇 |
2003年 | 1349篇 |
2002年 | 1234篇 |
2001年 | 990篇 |
2000年 | 978篇 |
1999年 | 898篇 |
1998年 | 797篇 |
1997年 | 714篇 |
1996年 | 596篇 |
1995年 | 557篇 |
1994年 | 499篇 |
1993年 | 480篇 |
1992年 | 368篇 |
1991年 | 350篇 |
1990年 | 279篇 |
1989年 | 216篇 |
1988年 | 186篇 |
1987年 | 164篇 |
1986年 | 137篇 |
1985年 | 180篇 |
1984年 | 187篇 |
1983年 | 167篇 |
1982年 | 147篇 |
1981年 | 97篇 |
1980年 | 71篇 |
1979年 | 85篇 |
1978年 | 61篇 |
1977年 | 67篇 |
1976年 | 19篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
121.
An advanced learning system for interactive simulation of patient cases (ISP) is described. The system was designed to meet specific pedagogical needs where student activation and problem orientation were two of the key issues. The system includes features such as video based illness history-taking function using free text input, highly interactive physiological examination procedures, extensive laboratory tests and detailed user feedback. The system was constructed mainly in Authorware Professional, starting more than 10 years ago, and it is now available in refined versions in different languages. Twelve pedagogical and three technical features were initially defined for the project. All of these aims were fulfilled. The ISP system has been successfully used in education, and in international collaboration, including three applicability field tests. The system is also a powerful research tool for studying for instance medical decision-making. 相似文献
122.
Common sense sometimes predicts events to be likely or unlikely rather than merely possible. We extend methods of qualitative reasoning to predict the relative likelihoods of possible qualitative behaviors by viewing the dynamics of a system as a Markov chain over its transition graph. This involves adding qualitative or quantitative estimates of transition probabilities to each of the transitions and applying the standard theory of Markov chains to distinguish persistent states from transient states and to calculate recurrence times, settling times, and probabilities for ending up in each state. Much of the analysis depends solely on qualitative estimates of transition probabilities, which follow directly from theoretical considerations and which lead to qualitative predictions about entire classes of systems. Quantitative estimates for specific systems are derived empirically and lead to qualitative and quantitative conclusions, most of which are insensitive to small perturbations in the estimated transition probabilities. The algorithms are straightforward and efficient. 相似文献
123.
Techniques for improving the reliability and maintainability of both nonrepairable and repairable items can be suggested by failure data analysis. It is shown that a given set of failure numbers leads to very different improvement strategies when the numbers are the times-between-successive-failures of one or more repairable items, rather than the times-to-failure of nonrepairable items. Since this should have been obvious more than 50 years ago, at the onset of formal reliability engineering activities, several reasons are proffered for the widespread and protracted misinterpretation of even the most basic—and simple!—conceptual and practical differences between nonrepairable and repairable items. 相似文献
124.
This paper deals with the time-optimal control problem for a class of control systems which includes controlled mechanical systems with possible dissipation terms. The Lie algebras associated with such mechanical systems have certain special properties. These properties are explored and used in conjunction with the Pontryagin maximum principle to determine the structure of singular extremals and, in particular, time-optimal trajectories. The theory is illustrated by an application to a time-optimal problem for a class of underwater vehicles. 相似文献
125.
126.
Emergency department status boards: user-evolved artefacts for inter- and intra-group coordination 总被引:1,自引:1,他引:0
Robert L. Wears Shawna J. Perry Stephanie Wilson Julia Galliers James Fone 《Cognition, Technology & Work》2007,9(3):163-170
Large, easily viewed status boards are commonly used in some healthcare settings such as emergency departments, operating
theaters, intensive care units, and inpatient wards. Because these artefacts were developed by front-line users, and have
little to no supervisory or regulatory control, they offer valuable insights into the theories of work and hazard held by
those users. Although the status boards case were locally developed over many years for within-group coordination, they have
also become useful for between-group coordination across organizational boundaries. In this paper, we compare and contrast
the use of such status boards in two disparate settings: a US emergency department, and a UK pediatric ward, and note striking
similarities in their form and usage, despite the large differences in setting. 相似文献
127.
In this article, we describe a knowledge-based controlled platform using program supervision techniques. This platform eases
the creation and the configuration of video surveillance systems. Several issues need to be addressed to provide a correct
system configuration: (1) to choose, among a library of programs, those which are best satisfying a given user request, (2)
to assign a correct value for each program parameter, (3) to evaluate performances and to guarantee a performance rate which
is satisfactory regarding end-user requirements. This platform is composed of three main components: the library of programs,
the knowledge base and the control component. The knowledge is either given by experts or learnt by the system. The control
is generic in the sense that it is independent of any application. To validate this platform, we have built and evaluated
six video surveillance systems which are featured with three properties: adaptability, reliability and real-time processing. 相似文献
128.
Jan Ramon Daan Fierens Fabián Güiza Geert Meyfroidt 《Advanced Engineering Informatics》2007,21(3):243-256
In this paper we describe the application of data mining methods for predicting the evolution of patients in an intensive care unit. We discuss the importance of such methods for health care and other application domains of engineering. We argue that this problem is an important but challenging one for the current state of the art data mining methods and explain what improvements on current methods would be useful. We present a promising study on a preliminary data set that demonstrates some of the possibilities in this area. 相似文献
129.
Nonlinear model predictive control with polytopic invariant sets 总被引:1,自引:0,他引:1
Ellipsoidal invariant sets have been widely used as target sets in model predictive control (MPC). These sets can be computed by constructing appropriate linear difference inclusions together with additional constraints to ensure that the ellipsoid lies within a given inclusion polytope. The choice of inclusion polytope has a significant effect on the size of the target ellipsoid, but the optimal inclusion polytope cannot in general be computed systematically. This paper shows that use of polytopic invariant sets overcomes this difficulty, allowing larger stabilizable sets without loss of performance. In the interests of online efficiency, consideration is focused on interpolation-based MPC. 相似文献
130.
Qing-Chang Zhong Author Vitae 《Automatica》2003,39(3):499-508
This paper generalizes the frequency-domain results on the delay-type Nehari problem in the stable case to the unstable case. The solvability condition of the delay-type Nehari problem is formulated in terms of the nonsingularity of three matrices. The optimal value γopt is the maximal γ∈(0,∞) such that one of the three matrices becomes singular. All sub-optimal compensators are parameterized in a transparent structure incorporating a modified Smith predictor. 相似文献