全文获取类型
收费全文 | 166381篇 |
免费 | 2651篇 |
国内免费 | 680篇 |
专业分类
电工技术 | 3279篇 |
综合类 | 229篇 |
化学工业 | 27199篇 |
金属工艺 | 6070篇 |
机械仪表 | 5230篇 |
建筑科学 | 5048篇 |
矿业工程 | 422篇 |
能源动力 | 4400篇 |
轻工业 | 18470篇 |
水利工程 | 1254篇 |
石油天然气 | 669篇 |
武器工业 | 5篇 |
无线电 | 21537篇 |
一般工业技术 | 31579篇 |
冶金工业 | 25804篇 |
原子能技术 | 2451篇 |
自动化技术 | 16066篇 |
出版年
2021年 | 1330篇 |
2019年 | 1189篇 |
2018年 | 1551篇 |
2017年 | 1574篇 |
2016年 | 1775篇 |
2015年 | 1500篇 |
2014年 | 2349篇 |
2013年 | 7591篇 |
2012年 | 4110篇 |
2011年 | 5690篇 |
2010年 | 4347篇 |
2009年 | 4855篇 |
2008年 | 5380篇 |
2007年 | 5627篇 |
2006年 | 4887篇 |
2005年 | 4568篇 |
2004年 | 4342篇 |
2003年 | 4247篇 |
2002年 | 4243篇 |
2001年 | 4180篇 |
2000年 | 3908篇 |
1999年 | 3880篇 |
1998年 | 6838篇 |
1997年 | 5400篇 |
1996年 | 4626篇 |
1995年 | 3878篇 |
1994年 | 3493篇 |
1993年 | 3312篇 |
1992年 | 2896篇 |
1991年 | 2756篇 |
1990年 | 2736篇 |
1989年 | 2723篇 |
1988年 | 2523篇 |
1987年 | 2248篇 |
1986年 | 2209篇 |
1985年 | 2651篇 |
1984年 | 2396篇 |
1983年 | 2266篇 |
1982年 | 2162篇 |
1981年 | 2066篇 |
1980年 | 1921篇 |
1979年 | 1935篇 |
1978年 | 1827篇 |
1977年 | 2152篇 |
1976年 | 2618篇 |
1975年 | 1626篇 |
1974年 | 1470篇 |
1973年 | 1483篇 |
1972年 | 1222篇 |
1971年 | 1130篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
41.
John C. Hart Gordon W. Lescinsky Daniel J. Sandin Thomas A. DeFanti Louis H. Kauffman 《The Visual computer》1993,9(7):346-355
The pipelined architecture and parallel organization of the AT&T Pixel Machine image computer are described and demonstrated with applications for the visualization of multidimensional fractals, particularly linear fractals and quaternion/ stacked Julia sets. Techniques for pushing the Pixel Machine to its peak abilities are described and apply to more recent parallel image computers as well. 相似文献
42.
I. S. W. B. Prasetya 《Formal Aspects of Computing》1994,6(4):466-470
UNITY, introduced by Chandy and Misra [ChM88], is a programming logic intended to reason about temporal properties of distributed programs. Despite the fact that UNITY does not have the full power of, for example, linear temporal logic, it enjoys popularity due to its simplicity.There was however a serious problem with the Substitution Rule. The logic is incomplete without the rule, and with the rule it is inconsistent. 相似文献
43.
Several variations of cache-based checkpointing for rollback error recovery from transient errors in shared-memory multiprocessors have been recently developed. By modifying the cache replacement policy, these techniques use the inherent redundancy in the memory hierarchy to periodically checkpoint the computation state. Three schemes, different in the manner in which they avoid rollback propagation, are evaluated in this paper. By simulation with address traces from parallel applications running on an Encore Multimax shared-memory multiprocessor, we evaluate the performance effect of integrating the recovery schemes in the cache coherence protocol. Our results indicate that the cache-based schemes can provide checkpointing capability with low performance overhead, but with uncontrollable high variability in the checkpoint interval 相似文献
44.
Control law design for rotorcraft fly-by-wire systems normally attempts to decouple the angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds should be adopted. Moreover, because of the large changes that occur in the aircraft dynamics due to small changes about the nominal design condition, especially for near-hovering flight, the crossfeed design must be ‘robust’. A new low-order matching method is presented here to design robust crossfeed compensators for multi-input, multi-output (MIMO) systems. The technique minimizes cross-coupling given an anticipated set of parameter variations for the range of flight conditions of concern. Results are presented in this paper of an analysis of the pitch/roll coupling of the UH-60 Black Hawk helicopter in near-hovering flight. A robust crossfeed is designed that shows significant improvement in decoupling perfomance and robustness over the fixed-gain or single point dynamic compensators. The design method and results are presented in an easily used graphical format that lends significant physical insight to the design procedure. This plant precompensation technique is an appropriate preliminary step to the design of robust feedback control laws for rotorcraft. 相似文献
45.
Silicon nitride corrugated diaphragms of 2 mm×2 mm×1 μm have been fabricated with 8 circular corrugations, having depths of 4, 10, or 14 μm. The diaphragms with 4-μm-deep corrugations show a measured mechanical sensitivity (increase in the deflection over the increase in the applied pressure) which is 25 times larger than the mechanical sensitivity of flat diaphragms of equal size and thickness. Since this gain in sensitivity is due to reduction of the initial stress, the sensitivity can only increase in the case of diaphragms with initial stress. A simple analytical model has been proposed that takes the influence of initial tensile stress into account. The model predicts that the presence of corrugations increases the sensitivity of the diaphragms, because the initial diaphragm stress is reduced. The model also predicts that for corrugations with a larger depth the sensitivity decreases, because the bending stiffness of the corrugations then becomes dominant. These predictions have been confirmed by experiments. The application of corrugated diaphragms offers the possibility to control the sensitivity of thin diaphragms by geometrical parameters, thus eliminating the effect of variations in the initial stress, due to variations in the diaphragm deposition process and/or the influence of temperature changes and packaging stress 相似文献
46.
Industries in the US continue to lose ground in international competition. If IS is to help change that trend, it will have to become more creative. Creativity improvement programs are being introduced in other areas of the company— now is the time for IS organizations to follow suit. 相似文献
47.
In the editorial by J.C. Bezdek (ibid., p.1), an example is presented to demonstrate differences between fuzzy membership and probability. The authors argue that probability can be used in a way much more closely analogous to this use of fuzzy membership, weakening the argument for the latter 相似文献
48.
A generalized fuzzy Petri net model 总被引:14,自引:0,他引:14
The paper proposes a new model of Petri nets based on the use of logic based neurons. In contrast to the existing generalizations, this approach is aimed at neural-type modeling of the entire concept with a full exploitation of the learning capabilities of the processing units being used there. The places and transitions of the net are represented by OR and AND-type and DOMINANCE neurons, respectively. A correspondence between this model and the previous two-valued counterpart is also revealed. The learning aspects associated with the nets are investigated 相似文献
49.
Wesley W. Chu Ph.D. Ion T. leong Ph.D. Ricky K. Taira Ph.D. 《The VLDB Journal The International Journal on Very Large Data Bases》1994,3(4):445-477
We introduce a semantic data model to capture the hierarchical, spatial, temporal, and evolutionary semantics of images in pictorial databases. This model mimics the user's conceptual view of the image content, providing the framework and guidelines for preprocessing to extract image features. Based on the model constructs, a spatial evolutionary query language (SEQL), which provides direct image object manipulation capabilities, is presented. With semantic information captured in the model, spatial evolutionary queries are answered efficiently. Using an object-oriented platform, a prototype medical-image management system was implemented at UCLA to demonstrate the feasibility of the proposed approach. 相似文献
50.
Robotica is a computer aided design package for robotic manipulators developed in the Coordinated Science Laboratory at the University of Illinois at Urbana-Champaign. It encapsulates over 30 functions into a Mathematica package allowing efficient symbolic and numeric calculation of kinematic and dynamic equations for multi-degree-of-freedom manipulators. An X-Windows front end that utilizes the interprocess communication features of Mathematica 2.1 has also been created for ease of use. This paper describes the most important features of the package and how they are used 相似文献