全文获取类型
收费全文 | 15905篇 |
免费 | 1184篇 |
国内免费 | 568篇 |
专业分类
电工技术 | 741篇 |
技术理论 | 1篇 |
综合类 | 901篇 |
化学工业 | 3340篇 |
金属工艺 | 759篇 |
机械仪表 | 905篇 |
建筑科学 | 969篇 |
矿业工程 | 372篇 |
能源动力 | 542篇 |
轻工业 | 1204篇 |
水利工程 | 260篇 |
石油天然气 | 694篇 |
武器工业 | 87篇 |
无线电 | 1812篇 |
一般工业技术 | 2218篇 |
冶金工业 | 719篇 |
原子能技术 | 177篇 |
自动化技术 | 1956篇 |
出版年
2024年 | 66篇 |
2023年 | 257篇 |
2022年 | 416篇 |
2021年 | 635篇 |
2020年 | 511篇 |
2019年 | 437篇 |
2018年 | 517篇 |
2017年 | 551篇 |
2016年 | 484篇 |
2015年 | 591篇 |
2014年 | 768篇 |
2013年 | 1055篇 |
2012年 | 932篇 |
2011年 | 907篇 |
2010年 | 868篇 |
2009年 | 799篇 |
2008年 | 742篇 |
2007年 | 772篇 |
2006年 | 777篇 |
2005年 | 606篇 |
2004年 | 468篇 |
2003年 | 493篇 |
2002年 | 575篇 |
2001年 | 468篇 |
2000年 | 392篇 |
1999年 | 405篇 |
1998年 | 365篇 |
1997年 | 324篇 |
1996年 | 276篇 |
1995年 | 218篇 |
1994年 | 177篇 |
1993年 | 124篇 |
1992年 | 121篇 |
1991年 | 95篇 |
1990年 | 72篇 |
1989年 | 56篇 |
1988年 | 51篇 |
1987年 | 33篇 |
1986年 | 40篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 27篇 |
1979年 | 13篇 |
1976年 | 20篇 |
1975年 | 6篇 |
1973年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Ye Wan Jun Tan Guangling Song Chuanwei Yan 《Metallurgical and Materials Transactions A》2006,37(7):2313-2316
The focused ion beam technique was employed to investigate the atmospheric corrosion morphology of AZ91D. It was found that
the α matrix of the alloy was preferentially corroded in the areas adjacent to intermetallic phases. The most interesting
finding was that the corrosion products in corrosion cavities were pelletlike, which has never been reported before. 相似文献
2.
Depending on whether bidirectional links or unidirectional links are used for communications, the network topology under a
given range assignment is either an undirected graph referred to as the bidirectional topology, or a directed graph referred
to as the unidirectional topology. The Min-Power Bidirectional (resp., Unidirectional) k-Node Connectivity problem seeks a range assignment of minimum total power subject to the constraint that the produced bidirectional
(resp. unidirectional) topology is k-vertex connected. Similarly, the Min-Power Bidirectional (resp., Unidirectional) k-Edge Connectivity problem seeks a range assignment of minimum total power subject to the constraint the produced bidirectional
(resp., unidirectional) topology is k-edge connected.
The Min-Power Bidirectional Biconnectivity problem and the Min-Power Bidirectional Edge-Biconnectivity problem have been studied
by Lloyd et al. [23]. They show that range assignment based the approximation algorithm of Khuller and Raghavachari [18],
which we refer to as Algorithm KR, has an approximation ratio of at most 2(2 – 2/n)(2 + 1/n) for Min-Power Bidirectional Biconnectivity, and range assignment based on the approximation algorithm of Khuller and Vishkin [19],
which we refer to as Algorithm KV, has an approximation ratio of at most 8(1 – 1/n) for Min-Power Bidirectional Edge-Biconnectivity.
In this paper, we first establish the NP-hardness of Min-Power Bidirectional (Edge-) Biconnectivity. Then we show that Algorithm KR has an approximation ratio of at most 4 for both Min-Power Bidirectional Biconnectivity and Min-Power Unidirectional Biconnectivity,
and Algorithm KV has an approximation ratio of at most 2k for both Min-Power Bidirectional k-Edge Connectivity and Min-Power Unidirectional k-Edge Connectivity. We also propose a new simple constant-approximation algorithm for both Min-Power Bidirectional Biconnectivity
and Min-Power Unidirectional Biconnectivity. This new algorithm applies only to Euclidean instances, but is best suited for
distributed implementation.
A preliminary version of this work appeared in the proceedings of the 2nd International Conference on AD-HOC Network and Wireless
(Adhoc-Now 2003).
Research performed in part while visiting the Max-Plank-Institut fur Informatik.
Gruia Calinescu is an Assistant Professor of Computer Science at the Illinois Institute of Technology since 2000. He held postdoc or visiting
researcher positions at DIMACS, University of Waterloo, and Max-Plank Institut fur Informatik. Gruia has a Diploma from University
of Bucharest and a Ph.D. from Georgia Insitute of Technology. His research interests are in the area of algorithms.
Peng-Jun Wan has joined the Computer Science Department at Illinois Institute of Technology in 1997 and has been an Associate Professor
since 2004. He received his Ph.D. in Computer Science from University of Minnesota in 1997, M.S. in Operations Research and
Control Theory from Chinese Academy of Science in 1993, and B.S. in Applied Mathematics from Tsinghua University in 1990.
His research interests include optical networks and wireless networks. 相似文献
3.
4.
5.
Bong Keun Kim Wan Kyun Chung 《Industrial Electronics, IEEE Transactions on》2003,50(6):1207-1216
Disturbance-observer (DOB)-based controller design is one of the most popular methods in the field of motion control. In this paper, the generalized disturbance compensation framework, named the robust internal-loop compensator (RIC) is introduced and an advanced design method of a DOB is proposed based on the RIC. The mixed sensitivity optimization problem, which is the main issue of DOB design, is also solved through the parametrization of the DOB in the RIC framework. Differently from conventional methods, the Q-filter is separated from the mixed sensitivity optimization problem and a systematic design law for the DOB is proposed. This guarantees the robustness and optimality of the DOB and enables the design for unstable plants. 相似文献
6.
On the magnetic-wall approximation for their slots, shielded coplanar waveguides (SCPWs) and semienclosed CPWs (SECPWs) are analyzed through an intensive use of elliptic function transformation. CAD-oriented formulas for the quasi-TEM parameters of SCPWs and SECPWs, including their coupled versions, are derived. The comparison of the results calculated here with previous ones show 2% accuracy for formulas in the practical situation where the slots are not too wide, e.g., s / (s + 2w) ≥ 0.2 for an SCPW. © 1994 John Wiley & Sons, Inc. 相似文献
7.
采用晶种技术,能有效地改善熟料的煅烧过程和熟料的质量。晶种和复合矿化剂的作用机理不同,在某些方面具有互补性。 相似文献
8.
9.
模袋混凝土护坡是一种新型的护面技术,具有整体性强、冲灌的混凝土强度可根据工程具体要求设计的优点.它克服了其它护面型式的诸多缺点,成为十分成熟的护面新技术.随着土工合成材料在水利工程上大面积推广应用,模袋混凝土护坡具有良好的应用前景. 相似文献
10.