全文获取类型
收费全文 | 3130篇 |
免费 | 180篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 30篇 |
综合类 | 16篇 |
化学工业 | 659篇 |
金属工艺 | 72篇 |
机械仪表 | 79篇 |
建筑科学 | 123篇 |
矿业工程 | 8篇 |
能源动力 | 90篇 |
轻工业 | 337篇 |
水利工程 | 22篇 |
石油天然气 | 8篇 |
无线电 | 332篇 |
一般工业技术 | 665篇 |
冶金工业 | 170篇 |
原子能技术 | 16篇 |
自动化技术 | 714篇 |
出版年
2023年 | 36篇 |
2022年 | 35篇 |
2021年 | 86篇 |
2020年 | 70篇 |
2019年 | 46篇 |
2018年 | 123篇 |
2017年 | 136篇 |
2016年 | 166篇 |
2015年 | 116篇 |
2014年 | 156篇 |
2013年 | 253篇 |
2012年 | 227篇 |
2011年 | 186篇 |
2010年 | 191篇 |
2009年 | 175篇 |
2008年 | 193篇 |
2007年 | 160篇 |
2006年 | 148篇 |
2005年 | 99篇 |
2004年 | 95篇 |
2003年 | 86篇 |
2002年 | 82篇 |
2001年 | 40篇 |
2000年 | 28篇 |
1999年 | 39篇 |
1998年 | 50篇 |
1997年 | 38篇 |
1996年 | 25篇 |
1995年 | 27篇 |
1994年 | 20篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 6篇 |
排序方式: 共有3341条查询结果,搜索用时 15 毫秒
101.
Cunin F Milhiet PE Anglin E Sailor MJ Espenel C Le Grimellec C Brunel D Devoisselle JM 《Ultramicroscopy》2007,107(10-11):1048-1052
Reconstituting artificial membranes for in vitro studies of cell barrier mechanisms and properties is of major interest in biology. Here, artificial membranes supported on porous silicon photonic crystal reflectors are prepared and investigated. The materials are of interest for label-free probing of supported membrane events such as protein binding, molecular recognition, and transport. The porous silicon substrates are prepared as multilayered films consisting of a periodically varying porosity, with pore dimensions of a few nanometers in size. Planar phospholipid bilayers are deposited on the topmost surface of the oxidized hydrophilic mesoporous silicon films. Atomic force microscopy provides evidence of continuous bilayer deposition at the surface, and optical measurements indicate that the lipids do not significantly infiltrate the porous region. The presence of the supported bilayer does not obstruct the optical spectrum from the porous silicon layer, suggesting that the composite structures can act as effective optical biosensors. 相似文献
102.
We consider the edit distance with moves on the class of words and the class of ordered trees. We first exhibit a simple tester
for the class of regular languages on words and generalize it to the class of ranked and unranked regular trees. We also show
that this distance problem is
-complete on ordered trees.
A preliminary version of this paper appeared in Proceedings of 31st International Colloquium on Automata, Languages and Programming, volume 3142 of Lecture Notes in Computer Science, pages 932–944, Springer, 2005. Work supported by ACI Sécurité Informatique: VERA of the French Ministry of research. 相似文献
103.
104.
105.
We describe two algorithms, BiBoost (Bipartite Boosting) and MultBoost (Multiparty Boosting), that allow two or more participants to construct a boosting classifier without explicitly sharing
their data sets. We analyze both the computational and the security aspects of the algorithms. The algorithms inherit the
excellent generalization performance of AdaBoost. Experiments indicate that the algorithms are better than AdaBoost executed separately by the participants, and that, independently of the number of participants, they perform close to AdaBoost executed using the entire data set.
Responsible Editor: Charu Aggarwal. 相似文献
106.
107.
阴离子交换树脂分离提取发酵液中的乳酸 总被引:1,自引:0,他引:1
为提高乳酸产品收率和纯度,实验筛选得到国产315型阴离子交换树脂,用于分离提取发酵液中乳酸,并研究其对乳酸、乙酸、丙酮酸及柠檬酸的吸附等温线、吸附动力学和动态吸附及洗脱效果.吸附等温线结果表明,315型树脂对乳酸等有机酸的吸附等温线符合Freundlich方程,特征参数n>1,属于优惠吸附.吸附动力学研究表明,液膜扩散是吸附过程的主要控制步骤,符合Boyd 液膜扩散模型.动态吸附及洗脱实验结果表明,以15 BV/h、pH 188上柱吸附,再用1 BV/h的去离子水洗脱,可实现发酵液中乳酸的良好分离. 相似文献
108.
The hitting time of a classical random walk (Markov chain) is the time required to detect the presence of—or equivalently, to find—a marked state. The hitting time of a quantum walk is subtler to define; in particular, it is unknown whether the detection and finding problems have the same time complexity. In this paper we define new Monte Carlo type classical and quantum hitting times, and we prove several relationships among these and the already existing Las Vegas type definitions. In particular, we show that for some marked state the two types of hitting time are of the same order in both the classical and the quantum case. Then, we present new quantum algorithms for the detection and finding problems. The complexities of both algorithms are related to the new, potentially smaller, quantum hitting times. The detection algorithm is based on phase estimation and is particularly simple. The finding algorithm combines a similar phase estimation based procedure with ideas of Tulsi from his recent theorem (Tulsi A.: Phys. Rev. A 78:012310 2008) for the 2D grid. Extending his result, we show that we can find a unique marked element with constant probability and with the same complexity as detection for a large class of quantum walks—the quantum analogue of state-transitive reversible ergodic Markov chains. Further, we prove that for any reversible ergodic Markov chain P, the quantum hitting time of the quantum analogue of P has the same order as the square root of the classical hitting time of P. We also investigate the (im)possibility of achieving a gap greater than quadratic using an alternative quantum walk. In doing so, we define a notion of reversibility for a broad class of quantum walks and show how to derive from any such quantum walk a classical analogue. For the special case of quantum walks built on reflections, we show that the hitting time of the classical analogue is exactly the square of the quantum walk. 相似文献
109.
110.
The working-set bound [Sleator and Tarjan in J. ACM 32(3), 652–686, 1985] roughly states that searching for an element is fast if the element was accessed recently. Binary search trees, such as splay trees, can achieve this property in the amortized sense, while data structures that are not binary search trees are known to have this property in the worst case. We close this gap and present a binary search tree called a layered working-set tree that guarantees the working-set property in the worst case. The unified bound [B?doiu et al. in Theor. Comput. Sci. 382(2), 86–96, 2007] roughly states that searching for an element is fast if it is near (in terms of rank distance) to a recently accessed element. We show how layered working-set trees can be used to achieve the unified bound to within a small additive term in the amortized sense while maintaining in the worst case an access time that is both logarithmic and within a small multiplicative factor of the working-set bound. 相似文献