全文获取类型
收费全文 | 1267篇 |
免费 | 48篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 11篇 |
综合类 | 2篇 |
化学工业 | 337篇 |
金属工艺 | 33篇 |
机械仪表 | 27篇 |
建筑科学 | 36篇 |
矿业工程 | 2篇 |
能源动力 | 74篇 |
轻工业 | 103篇 |
水利工程 | 2篇 |
石油天然气 | 16篇 |
无线电 | 94篇 |
一般工业技术 | 308篇 |
冶金工业 | 63篇 |
原子能技术 | 17篇 |
自动化技术 | 194篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 58篇 |
2021年 | 73篇 |
2020年 | 46篇 |
2019年 | 38篇 |
2018年 | 63篇 |
2017年 | 56篇 |
2016年 | 48篇 |
2015年 | 32篇 |
2014年 | 57篇 |
2013年 | 108篇 |
2012年 | 52篇 |
2011年 | 85篇 |
2010年 | 78篇 |
2009年 | 67篇 |
2008年 | 67篇 |
2007年 | 55篇 |
2006年 | 45篇 |
2005年 | 48篇 |
2004年 | 35篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 16篇 |
2000年 | 5篇 |
1999年 | 10篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1319条查询结果,搜索用时 31 毫秒
21.
Media access protocols in wireless networks require each contending node to wait for a backoff time, chosen randomly from a fixed range, before attempting to transmit on a shared channel. However, nodes acting in their own selfish interest may not follow the protocol. In this paper, a static version of the problem is modeled as a strategic game played by non-cooperating, rational players (the nodes). The objective is to design a game which exhibits a unique, a priori mixed-strategy Nash equilibrium. In the context of the media access problem, the equilibrium of the game would correspond to nodes choosing backoff times randomly from a given range of values, according to the given distribution. We consider natural variations of the problems concerning the number of actions available to the players and show that it is possible to design such a game when there are at least two players that each have the largest number of possible actions among all players. In contrast, we show that if there are exactly two players with different number of actions available to them, then it becomes impossible to design a strategic game with a unique such Nash equilibrium. 相似文献
22.
Sunil Kumar Richard J. Pippy Erdem Acar Nam H. Kim Raphael T. Haftka 《Structural and Multidisciplinary Optimization》2009,38(6):613-626
Probabilistic structural design deals with uncertainties in response (e.g. stresses) and capacity (e.g. failure stresses).
The calculation of the structural response is typically expensive (e.g., finite element simulations), while the capacity is
usually available from tests. Furthermore, the random variables that influence response and capacity are often disjoint. In
previous work we have shown that this disjoint property can be used to reduce the cost of obtaining the probability of failure
via Monte Carlo simulations. In this paper we propose to use this property for an approximate probabilistic optimization based
on exact capacity and approximate response distributions (ECARD). In Approximate Probabilistic Optimization Using ECARD, the
change in response distribution is approximated as the structure is re-designed while the capacity distribution is kept exact,
thus significantly reducing the number of expensive response simulations. ECARD may be viewed as an extension of SORA (Sequential
Optimization and Reliability Assessment), which proceeds with deterministic optimization iterations. In contrast, ECARD has
probabilistic optimization iterations, but in each iteration, the response distribution is approximated so as not to require
additional response calculations. The use of inexpensive probabilistic optimization allows easy incorporation of system reliability
constraints and optimal allocation of risk between failure modes. The method is demonstrated using a beam problem and a ten-bar
truss problem. The former allocates risk between two different failure modes, while the latter allocates risk between members.
It is shown that ECARD provides most of the improvement from risk re-allocation that can be obtained from full probabilistic
optimization. 相似文献
23.
Sunny Chilankamol Das Satyajit Martin Kevin J. M. Coussy Philippe 《Journal of Signal Processing Systems》2022,94(9):895-912
Journal of Signal Processing Systems - Research interest and industry investment in edge computing solutions have increased dramatically in recent years. Consequent quest for balanced performance,... 相似文献
24.
Sanjay Sahare Ravi Kant Choubey Gurunath Jadhav Tejashree M. Bhave Samrat Mukherjee Sunil Kumar 《Journal of Superconductivity and Novel Magnetism》2017,30(6):1439-1446
In this report, we studied various structural and optical properties of pure and copper-doped cadmium oxide (CdO) thin films. Nanostructured Cu-doped CdO films were deposited using sol–gel spin-coating technique. The structural and morphological changes have been observed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) studies. The optical and electrical properties of the pure and Cu-doped CdO thin films were studied by UV–vis spectroscopy and four-point probe method, respectively. The XRD peaks show the formation of nanocrystalline CdO with cubic face-centered crystal structure. The band gaps of the as deposited films were found in the range of 2.32–2.73 eV, while after doping, it decreases due to structural deformation. The electrical resitivity was found to decrease approximately ~10 in Cu-doped CdO thin films. 相似文献
25.
26.
The investigations on optimization of composite composition of nickel–zirconia for the functionally graded layered thermal barrier coating for the lowest but uniform stress field under thermal loading is presented. The procedure for obtaining temperature- and composition-dependent thermal and mechanical properties of various coating compositions is discussed. These material parameters were used in thermo-mechanical finite element stress analyses of a nickel substrate with the coating. The results showed that the Von-Mises stresses in the substrate and the interfaces were the lowest with the coating profile that followed a concave power law relationship with the index n ≈ 2.65. 相似文献
27.
An axis-parallel k-dimensional box is a Cartesian product R 1×R 2×???×R k where R i (for 1≤i≤k) is a closed interval of the form [a i ,b i ] on the real line. For a graph G, its boxicity box?(G) is the minimum dimension k, such that G is representable as the intersection graph of (axis-parallel) boxes in k-dimensional space. The concept of boxicity finds applications in various areas such as ecology, operations research etc. A number of NP-hard problems are either polynomial time solvable or have much better approximation ratio on low boxicity graphs. For example, the max-clique problem is polynomial time solvable on bounded boxicity graphs and the maximum independent set problem for boxicity d graphs, given a box representation, has a $\lfloor 1+\frac{1}{c}\log n\rfloor^{d-1}An axis-parallel k-dimensional box is a Cartesian product R
1×R
2×⋅⋅⋅×R
k
where R
i
(for 1≤i≤k) is a closed interval of the form [a
i
,b
i
] on the real line. For a graph G, its boxicity box (G) is the minimum dimension k, such that G is representable as the intersection graph of (axis-parallel) boxes in k-dimensional space. The concept of boxicity finds applications in various areas such as ecology, operations research etc.
A number of NP-hard problems are either polynomial time solvable or have much better approximation ratio on low boxicity graphs.
For example, the max-clique problem is polynomial time solvable on bounded boxicity graphs and the maximum independent set
problem for boxicity d graphs, given a box representation, has a
?1+\frac1clogn?d-1\lfloor 1+\frac{1}{c}\log n\rfloor^{d-1}
approximation ratio for any constant c≥1 when d≥2. In most cases, the first step usually is computing a low dimensional box representation of the given graph. Deciding whether
the boxicity of a graph is at most 2 itself is NP-hard. 相似文献
28.
Cheng Reynold Kao Ben Kwan Alan Prabhakar Sunil Tu Yicheng 《Knowledge and Data Engineering, IEEE Transactions on》2010,22(2):234-248
The idea of allowing query users to relax their correctness requirements in order to improve performance of a data stream management system (e.g., location-based services and sensor networks) has been recently studied. By exploiting the maximum error (or tolerance) allowed in query answers, algorithms for reducing the use of system resources have been developed. In most of these works, however, query tolerance is expressed as a numerical value, which may be difficult to specify. We observe that in many situations, users may not be concerned with the actual value of an answer, but rather which object satisfies a query (e.g., "who is my nearest neighbor?”). In particular, an entity-based query returns only the names of objects that satisfy the query. For these queries, it is possible to specify a tolerance that is "nonvalue-based.” In this paper, we study fraction-based tolerance, a type of nonvalue-based tolerance, where a user specifies the maximum fractions of a query answer that can be false positives and false negatives. We develop fraction-based tolerance for two major classes of entity-based queries: 1) nonrank-based query (e.g., range queries) and 2) rank-based query (e.g., k-nearest-neighbor queries). These definitions provide users with an alternative to specify the maximum tolerance allowed in their answers. We further investigate how these definitions can be exploited in a distributed stream environment. We design adaptive filter algorithms that allow updates be dropped conditionally at the data stream sources without affecting the overall query correctness. Extensive experimental results show that our protocols reduce the use of network and energy resources significantly. 相似文献
29.
Pei-Lan Lei Gloria Yi-Ming Kao Sunny S.J. Lin Chuen-Tsai Sun 《Computers in human behavior》2009,25(6):1270-1279
Google Earth search function was used to study the impacts of small-scale spatial ability, large-scale environmental cognition, and geographical knowledge on new technology usage. The participants were 153 junior high students from central Taiwan. Geography grades served as indicators of prior knowledge, mental rotation and abstract reasoning skills as indicators of spatial ability, and sketch maps of school neighborhoods as indicators of environmental cognition (including landmark representation, intersection representation, and frame of reference). Lastly, the authors announced the landmarks searching worksheet and asked the participants to accomplish 16 familiar and unfamiliar landmark searching tasks using Google Earth with keyword search function disabled. The result showed the strongest predictor of landmark searching performance is ‘frame of reference’ in environmental cognition, followed by ‘mental rotation’ of spatial ability, ‘landmark representation’ of environmental cognition, and geographical knowledge. Google Earth landmark searches require complex cognitive processing; therefore, our conclusion is that GIS-supported image search activities give students good practice of active knowledge construction. 相似文献
30.
在游戏这个飞速发展的行业里,人们喜新厌旧,玩家们会随意拥立一个游戏的王者,也会多次在一刹那间把被奉为神作的游戏拉下神坛。单机游戏时代似乎已经与我们渐行渐远,不少人怀念那个时代纯粹的快乐,感叹时光不再复返,但有些东西却留了下来,恰如目标软件。
这个成立于1995年的中国游戏企业,经历过中国游戏的黎明时代和历史转型期,从这样的游戏公司身上,我们可以看到中国的游戏产业在诞生的过程中经历了怎样的分娩阵痛;从这样的游戏公司的管理者身上,我们可以看到,中国游戏行业的沧桑变化。
目标公司在历经了十几年的发展后,已经成为了国内游戏界的一流研发企业。现在,我们就来看看,这个企业是如何将中国自主研发战略坚持到底的。 相似文献