全文获取类型
收费全文 | 690253篇 |
免费 | 7343篇 |
国内免费 | 1174篇 |
专业分类
电工技术 | 12317篇 |
综合类 | 525篇 |
化学工业 | 109526篇 |
金属工艺 | 30543篇 |
机械仪表 | 22505篇 |
建筑科学 | 15192篇 |
矿业工程 | 6005篇 |
能源动力 | 16887篇 |
轻工业 | 51731篇 |
水利工程 | 9034篇 |
石油天然气 | 20030篇 |
武器工业 | 48篇 |
无线电 | 70234篇 |
一般工业技术 | 146763篇 |
冶金工业 | 112422篇 |
原子能技术 | 18895篇 |
自动化技术 | 56113篇 |
出版年
2021年 | 6629篇 |
2019年 | 6299篇 |
2018年 | 11245篇 |
2017年 | 11417篇 |
2016年 | 11961篇 |
2015年 | 7328篇 |
2014年 | 12501篇 |
2013年 | 31252篇 |
2012年 | 19016篇 |
2011年 | 25302篇 |
2010年 | 20319篇 |
2009年 | 22713篇 |
2008年 | 23016篇 |
2007年 | 22579篇 |
2006年 | 19412篇 |
2005年 | 17505篇 |
2004年 | 16783篇 |
2003年 | 16450篇 |
2002年 | 15921篇 |
2001年 | 15381篇 |
2000年 | 14816篇 |
1999年 | 14336篇 |
1998年 | 32109篇 |
1997年 | 23528篇 |
1996年 | 18300篇 |
1995年 | 14148篇 |
1994年 | 12958篇 |
1993年 | 12689篇 |
1992年 | 9987篇 |
1991年 | 9816篇 |
1990年 | 9686篇 |
1989年 | 9380篇 |
1988年 | 9029篇 |
1987年 | 8335篇 |
1986年 | 8066篇 |
1985年 | 9024篇 |
1984年 | 8298篇 |
1983年 | 8027篇 |
1982年 | 7287篇 |
1981年 | 7440篇 |
1980年 | 7187篇 |
1979年 | 7406篇 |
1978年 | 7385篇 |
1977年 | 8045篇 |
1976年 | 9720篇 |
1975年 | 6669篇 |
1974年 | 6579篇 |
1973年 | 6646篇 |
1972年 | 5820篇 |
1971年 | 5399篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
The effects of a biquadratic exchange and an external magnetic field on the phase states of a twodimensional non-Heisenberg ferromagnet have been studied with allowance for magnetoelastic and magnetodipolar interactions. 相似文献
902.
R. A. Borzooei M. Bakhshi M. Mashinchi 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(8):739-749
In this paper, we study the lattice structure of some fuzzy algebraic systems such as (G-)fuzzy groups, some fuzzy ordered
algebras and fuzzy hyperstructures. We prove that under suitable conditions, these structures form a distributive or modular
lattice.
This research partially is supported by the “ Fuzzy Systems and its Applications Center of Excelence, Shahid Bahonar University
of Kerman, Iran”. 相似文献
903.
Isler V. Magdon-Ismail M. 《Automation Science and Engineering, IEEE Transactions on》2008,5(4):651-660
We address the sensor selection problem which arises in tracking and localization applications. In sensor selection, the goal is to select a small number of sensors whose measurements provide a good estimate of a target's state (such as location). We focus on the bounded uncertainty sensing model where the target is a point in the d -dimensional Euclidean space. Each sensor measurement corresponds to a convex polyhedral subset of the space. The measurements are merged by intersecting corresponding sets. We show that, on the plane, four sensors are sufficient (and sometimes necessary) to obtain an estimate whose area is at most twice the area of the best possible estimate (obtained by intersecting all measurements). We also extend this result to arbitrary dimensions and show that a constant number of sensors suffice for a constant factor approximation in arbitrary dimensions. Both constants depend on the dimensionality of the space but are independent of the total number of sensors in the network. 相似文献
904.
Officially, AI was born in 1956. Since then, very impressive progress has been made in many areas - but not in the realm of human level machine intelligence. During much of its early history, AI "was rife "with exaggerated expectations. A headline in an article published in the late forties of last century was headlined, "Electric brain capable of translating foreign languages is being built". Today, more than half a century later, we do have translation software, but nothing that can approach the quality of human translation. Clearly, achievement of human level machine intelligence is a challenge that is hard to meet. A prerequisite to achievement of human level machine intelligence is mechanization of these capabilities and, in particular, mechanization of natural language understanding. To make significant progress toward achievement of human level machine intelligence, a paradigm shift is needed. More specifically, what is needed is an addition to the armamentarium of AI of two methodologies: (a) a nontraditional methodology of computing with words (CW) or more generally, NL-Computation; and (b) a countertraditional methodology "which involves a progression from computing with numbers to computing with words. The centerpiece of these methodologies is the concept of precisiation of meaning. Addition of these methodologies to AI would be an important step toward the achievement of human level machine intelligence and its applications in decision-making, pattern recognition, analysis of evidence, diagnosis, and assessment of causality. Such applications have a position of centrality in our infocentric society. 相似文献
905.
QoS assessment of 3G video-phone calls by tracing watermarking exploiting the new colour space `YST?
Tracing watermarking has been recently proposed as a technique to provide a blind measure of the quality of service of the communication link, focusing on multimedia communication scenarios. 3G communication scenarios, where each customer transmits both voice and MPEG-4 video sequences in real time, have been considered. Typical video-phone call consists of close shots of speakers, framing their face in the foreground. For such particular application, a novel colour space (YST) is adopted to minimise the perceptual distortions on face coding introduced by watermarking. In the YST space, the luminance component (Y) is the same as in conventional YUV space, whereas the vectors S and T lie within the chrominance (UV) plane. The S (skin) component is a linear combination of U and V obtained as the 'average' chrominance estimated from an assorted set human faces to achieve a reasonable generalisation. The third component, T, is defined as orthogonal to the YS plane. The results show the benefits obtained in digital watermarking by the new representation against the conventional approach. In fact, the sensitivity of the YST representation outperforms the conventional one in terms of objective (mean square error, peak signal-to-noise ratio) and subjective (video-quality metrics) indicators. 相似文献
906.
V. N. Fetisov 《Automation and Remote Control》2004,65(4):594-602
Studies are made of a problem of constructing a robust system according to an averaged performance criterion of a stochastic control system. Cases of the parametric and the structural uncertainty are considered. The relation of the notion of the stochastic robustness to the classical definition of deterministic systems is shown. A comparative analysis of the suggested method of developing a robust system and some other approaches is carried out. 相似文献
907.
908.
A. V. Adel'shin 《Automation and Remote Control》2004,65(3):388-395
Problems of the maximum and the minimum satisfiability on the basis of the integer linear programming and L-partition are studied. The L-structure of polyhedrons of the problems is investigated. Families are set up of unweighted problems of the maximum and the minimum satisfiability, the powers of L-coverings of which grow exponentially with an increase in the number of variables in a formula. 相似文献
909.
V. P. Shmerko 《Automation and Remote Control》2004,65(6):893-912
Theoretical results due to V. Malyugin on linearization of arithmetical models of logical functions are interpreted and refined from the viewpoint of modern techniques of logical design of integral circuits and nearest neighbor technologies. 相似文献
910.
A quantitative study of firewall configuration errors 总被引:1,自引:0,他引:1
The protection that firewalls provide is only as good as the policy they are configured to implement. Analysis of real configuration data show that corporate firewalls are often enforcing rule sets that violate well established security guidelines. Firewalls are the cornerstone of corporate intranet security. Once a company acquires a firewall, a systems administrator must configure and manage it according to a security policy that meets the company's needs. Configuration is a crucial task, probably the most important factor in the security a firewall provides. 相似文献