全文获取类型
收费全文 | 9296篇 |
免费 | 318篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 102篇 |
综合类 | 9篇 |
化学工业 | 2097篇 |
金属工艺 | 256篇 |
机械仪表 | 188篇 |
建筑科学 | 340篇 |
矿业工程 | 28篇 |
能源动力 | 207篇 |
轻工业 | 784篇 |
水利工程 | 112篇 |
石油天然气 | 38篇 |
武器工业 | 2篇 |
无线电 | 683篇 |
一般工业技术 | 1748篇 |
冶金工业 | 1931篇 |
原子能技术 | 62篇 |
自动化技术 | 1045篇 |
出版年
2023年 | 63篇 |
2022年 | 112篇 |
2021年 | 184篇 |
2020年 | 145篇 |
2019年 | 137篇 |
2018年 | 188篇 |
2017年 | 172篇 |
2016年 | 188篇 |
2015年 | 141篇 |
2014年 | 231篇 |
2013年 | 505篇 |
2012年 | 403篇 |
2011年 | 507篇 |
2010年 | 330篇 |
2009年 | 361篇 |
2008年 | 431篇 |
2007年 | 426篇 |
2006年 | 343篇 |
2005年 | 315篇 |
2004年 | 285篇 |
2003年 | 246篇 |
2002年 | 262篇 |
2001年 | 118篇 |
2000年 | 128篇 |
1999年 | 131篇 |
1998年 | 161篇 |
1997年 | 146篇 |
1996年 | 156篇 |
1995年 | 142篇 |
1994年 | 140篇 |
1993年 | 158篇 |
1992年 | 119篇 |
1991年 | 109篇 |
1990年 | 131篇 |
1989年 | 106篇 |
1988年 | 82篇 |
1987年 | 130篇 |
1986年 | 97篇 |
1985年 | 127篇 |
1984年 | 124篇 |
1983年 | 131篇 |
1982年 | 104篇 |
1981年 | 93篇 |
1980年 | 77篇 |
1979年 | 74篇 |
1978年 | 92篇 |
1977年 | 72篇 |
1976年 | 74篇 |
1975年 | 79篇 |
1974年 | 83篇 |
排序方式: 共有9632条查询结果,搜索用时 10 毫秒
81.
82.
Kim Tak H. Sirdaarta Joseph P. Zhang Qian Eftekhari Ehsan St. John James Kennedy Derek Cock Ian E. Li Qin 《Nano Research》2018,11(4):2204-2216
Nano Research - The toxicity of nanoparticles in a biological system is an integration of effects arising from surface functionality, particle size, ionic dissolution, etc. This complexity suggests... 相似文献
83.
The computation of visible surfaces is usually formulated in a regularization framework based on thin-plate and membrane splines. When discretized, this formulation leads to large sparse linear systems. Most surface interpolation methods solve these sparse systems with iterative methods. Here we explore the use of direct methods. Through a careful analysis of the regularization operator, we derive direct methods that efficiently make use of all zeros in the sparse discretization of the operator. Experimental results show that, compared with iterative interpolation methods, the direct methods we present are competitive in general, and they provide significant speed-ups for problems involving discontinuities. In addition to their use in visible-surface interpolation, the presented methods also support very efficient time integration for deformable surfaces. 相似文献
84.
David A. Bader Joseph Jájá David Harwood Larry S. Davis 《The Journal of supercomputing》1996,10(2):141-168
This paper presents efficient and portable implementations of a powerful image enhancement process, the Symmetric Neighborhood Filter (SNF), and an image segmentation technique that makes use of the SNF and a variant of the conventional connected components algorithm which we call -Connected Components. We use efficient techniques for distributing and coalescing data as well as efficient combinations of task and data parallelism. The image segmentation algorithm makes use of an efficient connected components algorithm based on a novel approach for parallel merging. The algorithms have been coded in Split-C and run on a variety of platforms, including the Thinking Machines CM-5, IBM SP-1 and SP-2, Cray Research T3D, Meiko Scientific CS-2, Intel Paragon, and workstation clusters. Our experimental results are consistent with the theoretical analysis (and provide the best known execution times for segmentation, even when compared with machine-specific implementations). Our test data include difficult images from the Landsat Thematic Mapper (TM) satellite data.Also affiliated with the Department of Electrical Engineering.Also affiliated with the Department of Computer Science and the Center for Automation Research. 相似文献
85.
Tao Dong Zhaochu Yang Qianhua Su Nhut Minh Tran Eirik Bentzen Egeland Frank Karlsen Yulong Zhang Matteo Joseph Kapiris Henrik Jakobsen 《Microfluidics and nanofluidics》2011,10(4):855-865
This study addresses the need to reduce the risk of clogging when preparing samples for cell concentration, i.e., the CaSki
Cell-lines (epidermoid cervical carcinoma cells). Aiming to develop a non-clogging microconcentrator, we proposed a new counter-flow
concentration unit characterized by the directions of penetrating flows being at an obtuse angle to the main flow, due to
employment of streamlined turbine blade-like micropillars. Based on the optimization results of the counter-flow unit profile,
a fractal arrangement for the counter-flow concentration unit was developed. A counter-flow microconcentrator chip was then
designed and fabricated, with both the processing layer and collecting layer arranged in terms of the honeycomb structure.
Visualized experiments using CaSki cell samples on the microconcentrator chip demonstrated that no cell-clogging phenomena
occurred during the test and that no cells were found in the final filtrate. The test results show an excellent concentration
performance for the microconcentrator chip, while a concentrating ratio of >4 with the flow rate being below 1.0 ml/min. As
only geometrical structure is employed in the passive device, the counter-flow microconcentrator can be easily integrated
into advanced microfluidic systems. Owing to the merit of non-clogging and continuous processing ability, the counter-flow
microconcentrator is not only suitable for the sample preparation within biomedical field, but also applicable in water-particle
separation. 相似文献
86.
Surrogate modeling approximation using a mixture of experts based on EM joint estimation 总被引:1,自引:1,他引:0
Dimitri Bettebghor Nathalie Bartoli Stéphane Grihon Joseph Morlier Manuel Samuelides 《Structural and Multidisciplinary Optimization》2011,43(2):243-259
An automatic method to combine several local surrogate models is presented. This method is intended to build accurate and
smooth approximation of discontinuous functions that are to be used in structural optimization problems. It strongly relies
on the Expectation−Maximization (EM) algorithm for Gaussian mixture models (GMM). To the end of regression, the inputs are
clustered together with their output values by means of parameter estimation of the joint distribution. A local expert is
then built (linear, quadratic, artificial neural network, moving least squares) on each cluster. Lastly, the local experts
are combined using the Gaussian mixture model parameters found by the EM algorithm to obtain a global model. This method is
tested over both mathematical test cases and an engineering optimization problem from aeronautics and is found to improve
the accuracy of the approximation. 相似文献
87.
Ohad Gur Manav Bhatia William H. Mason Joseph A. Schetz Rakesh K. Kapania Taewoo Nam 《Structural and Multidisciplinary Optimization》2011,44(2):277-298
The paper describes the development of a multidisciplinary design optimization framework for conceptual design of truss-braced
wing configurations. This unconventional configuration requires specialized analysis tools supported by a modular and flexible
framework to accommodate different configurations. While the previous framework developed at Virginia Tech was a monolithic
Fortran-77 code, the need for more flexibility for complex truss-braced wing configurations was addressed by the development
of this new framework, which is based on Phoenix Integration ModelCenterTM environment. The framework uses updated structural and aerodynamic design modules that enable a more general geometry definition.
The new framework, thus, provides a foundation for future design concepts, especially multi-member truss-braced wing configurations.
The fuel saving potential of these truss-braced wing configurations is presented by comparing different truss designs with
gradually increased level of complexity. 相似文献
88.
We consider the problem of nonpreemptively scheduling a set of n jobs with equal processing times on m parallel machines so as to minimize the makespan. Each job has a prespecified set of machines on which it can be processed,
called its eligible set. We consider the most general case of machine eligibility constraints as well as special cases of nested and inclusive eligible
sets. Both online and offline models are considered. For offline problems we develop optimal algorithms that run in polynomial
time, while for online problems we focus on the development of optimal algorithms of a new and more elaborate structure as
well as approximation algorithms with good competitive ratios. 相似文献
89.
Consider a distributed system N in which each agent has an input value and each communication link has a weight. Given a global function, that is, a function
f whose value depends on the whole network, the goal is for every agent to eventually compute the value f (N). We call this problem global function computation. Various solutions for instances of this problem, such as Boolean function computation, leader election, (minimum) spanning
tree construction, and network determination, have been proposed, each under particular assumptions about what processors
know about the system and how this knowledge can be acquired. We give a necessary and sufficient condition for the problem
to be solvable that generalizes a number of well-known results (Attyia et al. in J ACM 35(4):845–875, 1988; Yamashita and
Kameda in IEEE Trans Parallel Distrib Syst 7(1):69–89, 1996; Yamashita and Kameda in IEEE Trans Parallel Distrib Syst 10(9):878–887,
1999). We then provide a knowledge-based (kb) program (like those of Fagin et al. (Reasoning about knowledge, MIT Press, Cambridge, 1995, Distrib Comput 10(4):199–225, 1997))
that solves global function computation whenever possible. Finally, we improve the message overhead inherent in our initial
kb program by giving a counterfactual belief-based program (Halpern and Moses in Distrib Comput 17(2):91–106, 2004) that also solves the global function computation whenever possible,
but where agents send messages only when they believe it is necessary to do so. The latter program is shown to be implemented
by a number of well-known algorithms for solving leader election. 相似文献
90.
Given a hypergraph and a set of embedded functional dependencies, we investigate the problem of determining the conditions under which we can efficiently generate redundancy-free XML storage structures with as few scheme trees as possible. Redundancy-free XML structures guarantee both economy in storage space and the absence of update anomalies, and having the least number of scheme trees requires the fewest number of joins to navigate among the data elements. We know that the general problem is intractable. The problem may still be intractable even when the hypergraph is acyclic and each hyperedge is in Boyce–Codd normal form (BCNF). As we show here, however, given an acyclic hypergraph with each hyperedge in BCNF, a polynomial-time algorithm exists that generates a largest possible redundancy-free XML storage structure. Successively generating largest possible scheme trees from among hyperedges not already included in generated scheme trees constitutes a reasonable heuristic for finding the fewest possible scheme trees. For many practical cases, this heuristic finds the set of redundancy-free XML storage structures with the fewest number of scheme trees. In addition to a correctness proof and a complexity analysis showing that the algorithm is polynomial, we also give experimental results over randomly generated but appropriately constrained hypergraphs showing empirically that the algorithm is indeed polynomial. 相似文献