全文获取类型
收费全文 | 460742篇 |
免费 | 8109篇 |
国内免费 | 1414篇 |
专业分类
电工技术 | 7984篇 |
综合类 | 358篇 |
化学工业 | 70809篇 |
金属工艺 | 17446篇 |
机械仪表 | 14579篇 |
建筑科学 | 10130篇 |
矿业工程 | 2272篇 |
能源动力 | 12715篇 |
轻工业 | 36720篇 |
水利工程 | 4792篇 |
石油天然气 | 8134篇 |
武器工业 | 22篇 |
无线电 | 52063篇 |
一般工业技术 | 92734篇 |
冶金工业 | 88809篇 |
原子能技术 | 9428篇 |
自动化技术 | 41270篇 |
出版年
2022年 | 3134篇 |
2021年 | 5188篇 |
2020年 | 3984篇 |
2019年 | 4927篇 |
2018年 | 8621篇 |
2017年 | 8537篇 |
2016年 | 9131篇 |
2015年 | 5904篇 |
2014年 | 9147篇 |
2013年 | 24128篇 |
2012年 | 14676篇 |
2011年 | 18298篇 |
2010年 | 14663篇 |
2009年 | 15992篇 |
2008年 | 16492篇 |
2007年 | 15967篇 |
2006年 | 14006篇 |
2005年 | 12449篇 |
2004年 | 11766篇 |
2003年 | 11547篇 |
2002年 | 10835篇 |
2001年 | 10436篇 |
2000年 | 9824篇 |
1999年 | 10308篇 |
1998年 | 28414篇 |
1997年 | 19381篇 |
1996年 | 14525篇 |
1995年 | 10592篇 |
1994年 | 9249篇 |
1993年 | 9309篇 |
1992年 | 6377篇 |
1991年 | 6034篇 |
1990年 | 5980篇 |
1989年 | 5623篇 |
1988年 | 5331篇 |
1987年 | 4677篇 |
1986年 | 4566篇 |
1985年 | 5113篇 |
1984年 | 4683篇 |
1983年 | 4192篇 |
1982年 | 3903篇 |
1981年 | 4010篇 |
1980年 | 3692篇 |
1979年 | 3506篇 |
1978年 | 3499篇 |
1977年 | 4159篇 |
1976年 | 5737篇 |
1975年 | 2972篇 |
1974年 | 2774篇 |
1973年 | 2854篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Zhongde Wang Jullien G.A. Miller W.C. Jinghong Wang Bizzan S.S. 《Solid-State Circuits, IEEE Journal of》1997,32(2):206-214
Using an enhanced multiple output domino logic (EMODL) implementation of a carry lookahead adder (CLA), sums of several consecutive bits can be built in one nFET tree with a single carry-in. Based on this result, a new sparse carry chain architecture is proposed for the CLA adder. We demonstrate the design approach using a 32-b adder, and show that only four carries are sufficient for generating all sums, with a consequent reduction in the number of stage delays. Using a 1.2-μm CMOS technology, we verify our simulation procedures by fabrication and measurement of a 2.7 ns critical path 相似文献
992.
Bufferless distributed circuit (BDC) broadcasting is proposed as a technique for broadcasting high-speed chip input signals to a series of on-chip destination cells as needed in crosspoint switch, parallel multiplier, distributed amplifier, etc., chip designs. In contrast with conventional techniques that use an on-chip buffer to assist broadcasting, BDC broadcasting offers the advantage of lower signal delay and power dissipation. In an experimental GaAs heterojunction bipolar transistor (HBT) 8×4 crosspoint switch assembly, BDC broadcasting was found to achieve a 40% power savings with little or no penalty in jitter or bit error rate performance at a 10-Gb/s data rate 相似文献
993.
Jenghwa Chang Graber H.L. Ping Chen Koo Aronson R. Barbour S.-L.S. Barbour R.L. 《IEEE transactions on medical imaging》1997,16(1):68-77
Presents a model suitable for computing images of absorption cross sections of thick tissue structures illuminated at near infrared (NIR) wavelengths from tomographic projection data. Image reconstruction is accomplished by solving a system of linear equations derived from transport theory. Reconstruction results using different algebraic solvers are shown for anatomical maps of the breast, derived from magnetic resonance imaging data, containing two simulated pathologies, in which case qualitatively good reconstructions were obtained. Evaluation of magnetic resonance (MR) data to optimize NIR optical tomographic imaging methods and to assess the feasibility of a combined MR-optical measurement scheme is discussed 相似文献
994.
Whether in improving quality or productivity the impact of mechatronic systems such as robots in industry is unquestionable. One aspect of interest in robotics is planning the optimum path for a mobile robot or the optimum trajectory for link movements of a stationary robot in order to increase their efficiency. However, for a given set of points complete enumeration of all the possible paths to establish an optimal one is not feasible as the search space increases exponentially (explodes combinatorially) as the number of points increases. This problem, traditionally known as the “Traveling Salesman Problem” (TSP) has attracted a great deal of attention for a long time. Proven enumerative techniques such as “nearest neighbour algorithm”, “branch and bound”, “cutting planes”, and “dynamic programming” as well as approximation methods such as “tabu search”, “greedy algorithm”, “simulated annealing” and “genetic algorithm”, have had only a limited success in solving this problem. Recently “convex hull”, a minimum area and perimeter shape, has been used as an initial sub-tour along with enumerative techniques such as minimising insertion costs to solve the TSP problem. We present a system which uses heuristic rules to augment the convex hull initial sub-tour created by the Graham scan algorithm. The system is able to provide a solution in a polynomial time. 相似文献
995.
996.
997.
In this article, a new algorithm based on an artificial potential field and hierarchical cell decomposition technique is developed to solve the find-path problem for a mobile robot. The complete map of the workspace including obstacle locations is assumed to be known a priori. The basic cell structure used for decomposition is a hexagon. The artificial potential field is based on an attractive force from the goal position and repelling forces from the obstacles. Computer simulations of the algorithm for various obstacle scenarios are also presented. © 1994 John Wiley & Sons, Inc. 相似文献
998.
Triple-correlation-based neural networks are introduced and used in this paper for invariant classification of 2D gray scale images. Third-order correlations of an image are appropriately clustered, in spatial or spectral domain, to generate an equivalent image representation that is invariant with respect to translation, rotation, and dilation. An efficient implementation scheme is also proposed, which is robust to distortions, insensitive to additive noise, and classifies the original image using adequate neural network architectures applied directly to 2D image representations. Third-order neural networks are shown to be a specific category of triple-correlation-based networks, applied either to binary or gray-scale images. A simulation study is given, which illustrates the theoretical developments, using synthetic and real image data. 相似文献
999.
1000.
This ex post facto study investigated the relationship of social support from two workplace sources, unit managers and registered nurse (RNs) coworkers, to work-related stress among staff nurses. Sample participants included 51 full-time RNs from a variety of clinical specialties in one nursing organization. The three theoretical components--affect, affirmation, and aid--were measured by the Norbeck Social Support Questionnaire. The Nursing Stress Scale was used to quantify the levels of perceived work-related stress. Statistically significant negative correlations were found between affect from unit managers (r = -299; P = 0.15) and aid from coworkers (r = -.294; P = .036) on levels of perceived work-related stress. Additionally, the increased age of the subjects (r = -.342; P = .007), years of nursing experience (r = -252; P = .037), and length of employment (r = -329; P = .009) had a negative relationship with work stress. The results of this research demonstrated that two components of social support--affect (emotional support) from unit managers and aid (services, information, materials) from coworkers--were linked to lower stress scores in this sample of staff nurses. 相似文献