全文获取类型
收费全文 | 4491篇 |
免费 | 340篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 89篇 |
综合类 | 22篇 |
化学工业 | 1150篇 |
金属工艺 | 99篇 |
机械仪表 | 76篇 |
建筑科学 | 358篇 |
矿业工程 | 54篇 |
能源动力 | 126篇 |
轻工业 | 314篇 |
水利工程 | 49篇 |
石油天然气 | 2篇 |
无线电 | 366篇 |
一般工业技术 | 956篇 |
冶金工业 | 342篇 |
原子能技术 | 17篇 |
自动化技术 | 818篇 |
出版年
2024年 | 7篇 |
2023年 | 69篇 |
2022年 | 105篇 |
2021年 | 174篇 |
2020年 | 134篇 |
2019年 | 114篇 |
2018年 | 150篇 |
2017年 | 133篇 |
2016年 | 183篇 |
2015年 | 194篇 |
2014年 | 218篇 |
2013年 | 307篇 |
2012年 | 300篇 |
2011年 | 370篇 |
2010年 | 306篇 |
2009年 | 242篇 |
2008年 | 249篇 |
2007年 | 252篇 |
2006年 | 198篇 |
2005年 | 181篇 |
2004年 | 121篇 |
2003年 | 112篇 |
2002年 | 86篇 |
2001年 | 57篇 |
2000年 | 55篇 |
1999年 | 62篇 |
1998年 | 81篇 |
1997年 | 49篇 |
1996年 | 56篇 |
1995年 | 38篇 |
1994年 | 25篇 |
1993年 | 27篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1979年 | 9篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1970年 | 8篇 |
1920年 | 4篇 |
排序方式: 共有4838条查询结果,搜索用时 343 毫秒
71.
Max-SAT-CC is the following optimization problem: Given a formula in CNF and a bound k, find an assignment with at most k variables being set to true that maximizes the number of satisfied clauses among all such assignments. If each clause is restricted to have at most ? literals, we obtain the problem Max-?SAT-CC. Sviridenko [Algorithmica 30 (3) (2001) 398-405] designed a (1−e−1)-approximation algorithm for Max-SAT-CC. This result is tight unless P=NP [U. Feige, J. ACM 45 (4) (1998) 634-652]. Sviridenko asked if it is possible to achieve a better approximation ratio in the case of Max-?SAT-CC. We answer this question in the affirmative by presenting a randomized approximation algorithm whose approximation ratio is . To do this, we develop a general technique for adding a cardinality constraint to certain integer programs. Our algorithm can be derandomized using pairwise independent random variables with small probability space. 相似文献
72.
We present a complete mechanized proof of the result in homological algebra known as basic perturbation lemma. The proof has
been carried out in the proof assistant Isabelle, more concretely, in the implementation of higher-order logic (HOL) available
in the system. We report on the difficulties found when dealing with abstract algebra in HOL, and also on the ongoing stages
of our project to give a certified version of some of the algorithms present in the Kenzo symbolic computation system.
J. Aransay was partially supported by Ministerio de Educación y Ciencia, MTM2006/06513, and by Gobierno de La Rioja ANGI2005/19
and J. Rubio was partially supported by Ministerio de Educación y Ciencia, MTM2006/06513, and by Gobierno de La Rioja ANGI2005/19. 相似文献
73.
Markus Hinkelmann Andreas Jakoby and Peer Stechert Institut für Theoretische Informatik Universitt zu Lübeck Germany Fachgruppe Didaktik der Informatik und E-Learning Universitt Siegen Germany 《计算机科学技术学报》2008,23(5)
In most of the auction systems the values of bids are known to the auctioneer. This allows him to manipulate the outcome of the auction. Hence, one might be interested in hiding these values. Some cryptographically secure protocols for electronic auctions have been presented in the last decade. Our work extends these protocols in several ways. On the basis of garbled circuits, i.e., encrypted circuits, we present protocols for sealed-bid auctions that fulfill the following requirements: 1) protocols are information-theoretically t-private for honest but curious parties; 2) the number of bits that can be learned by malicious adversaries is bounded by the output length of the auction; 3) the computational requirements for participating parties are very low: only random bit choices and bitwise computation of the XOR-function are necessary. Note that one can distinguish between the protocol that generates a garbled circuit for an auction and the protocol to evaluate the auction. In this paper we address both problems. We will present a t-private protocol for the construction of a garbled circuit that reaches the lower bound of 2t 1 parties, and a more randomness effcient protocol for (t 1)2 parties. Finally, we address the problem of bid changes in an auction. 相似文献
74.
Marco Bakera Tiziana Margaria Clemens D. Renner Bernhard Steffen 《Innovations in Systems and Software Engineering》2009,5(3):211-228
We show on a case study from an autonomous aerospace context how to apply a game-based model-checking approach as a powerful
technique for the verification, diagnosis, and adaptation of system behaviors based on temporal properties. This work is part
of our contribution within the SHADOWS project, where we provide a number of enabling technologies for model-driven self-healing.
We propose here to use GEAR, a game-based model checker, as a user-friendly tool that can offer automatic proofs of critical
properties of such systems. Although it is a model checker for the full modal μ-calculus, it also supports derived, more user-oriented logics. With GEAR, designers and engineers can interactively investigate
automatically generated winning strategies for the games, by this way exploring the connection between the property, the system,
and the proof.
This work has been partially supported by the European Union Specific Targeted Research Project SHADOWS (IST-2006-35157), exploring a Self-Healing Approach to Designing cOmplex softWare Systems. The project’s web page is at .
This article is an extended version of Renner et al. [18] presented at ISoLA 2007, Poitiers, December 2007. 相似文献
75.
van Oostrum J Calonder C Rechsteiner D Ehrat M Mestan J Fabbro D Voshol H 《Proteomics. Clinical applications》2009,3(4):412-422
Controlling aberrant protein kinase activity is a promising strategy for a variety of diseases, particularly cancer. Hence, the development of kinase inhibitors is currently a focal point for pharmaceutical research. In this study we utilize a chip-based reverse phase protein array (RPA) platform for profiling of kinase inhibitors in cell-based assays. In combination with the planar wave-guide technology the assay system has an absolute LOD down to the low zeptomole range. A431 cell lysates were analyzed for the activation state of key effectors in the epidermal growth factor (EGF) and insulin signaling pathways to validate this model for compound screening. A microtiter-plate format for growing, treating, and lysing cells was shown to be suitable for this approach, establishing the value of the technology as a screening tool for characterization of large numbers of kinase inhibitors against a wide variety of cellular signaling pathways. Moreover, the reverse array format allows rapid development of site-specific phosphorylation assays, since in contrast to ELISA type systems only a single antigen-specific antibody is required. 相似文献
76.
Ludovit Markus 《Journal of Intelligent and Robotic Systems》1994,11(1-2):109-116
A general method for solving the robot inverse kinematics problem is presented. The method is based upon the general elimination method to obtain the equivalent system of equations which are triangularized and the solutions of the inverse kinematics problem can be solved by backsubstitutions. 相似文献
77.
Hemminki Ari; Hoffren Anna-Marja; Takkinen Kristiina; Vehniainen Markus; Makinen Maija-Liisa; Pettersson Kim; Teleman Olle; Soderlund Hans; Teeri Tuula T. 《Protein engineering, design & selection : PEDS》1995,8(2):185-191
Europium chelates provide a non-radioactive alternative forsensitive labelling of antibodies for diagnostic immunoassays.Lysine residues at antibody surfaces are ready targets for labellingby an isothiocyanate derivative of the europium chelate (Eu3+).Here the labelling efficiency of a recombinant anti-human -fetoprotein(hAFP) Fab fragment has been improved by increasing its lysinecontent by protein engineering. Molecular modelling was usedto identify three light chain constant domain surface arginineresidues, R154, R187 and R210, which were mutated to lysineresidues. The mutations did not influence the affinity of thelysine-enriched Fab fragment and its labelling efficiency wasfound to be 40% higher than that of the wildtype Fab fragmentWith low degree of labelling, the affinities of the two Fabfragments were identical and comparable with that of the originalmonoclonal anti-hAFP IgG. With a higher degree of labellingthe affinities of both Fab fragments decreased more than thatof the intact IgG since more lysine residues are available forlabelling in the additional heavy chain constant domains ofthe larger molecule. Electrostatic adsorption and covalent immobilizationof the Fab fragments were characterized by BIAcoreTM and thelysine-enriched Fab fragment was found to be more efficientlyimmobilized to an activated carboxymethyl surface. 相似文献
78.
Erik Valentine Bachtiar Markus Rüggeberg Stefan Hering Michael Kaliske Peter Niemz 《Materials and Structures》2017,50(6):248
In this study, several theoretical models to numerically estimate shear properties of orthotropic materials are introduced. These approaches are based on the combination of Hankinson’s empirically derived formula with other empirical and analytical calculations. Next to shear moduli, which are estimated from the elastic moduli and Poisson’s ratios, shear strengths are also estimated from the in-axis strengths. The models are validated by mechanical tests on walnut wood (Juglans regia L.), for which a sufficient data set can be found in literature. The Arcan test is used to estimate the shear moduli, while the shear block test is used to estimate the shear strengths. The results show that the model, which is based on a combined use of Hankinson’s formula and tensor rotation, gives the best estimation of shear moduli as evaluated by the minimum differences to the experimentally obtained results. For the shear strengths, a combination of Hankinson’s formula and Norris’ failure criterion shows the best agreement in comparison to the experimental data. The theoretical calculations may be used for a time efficient estimation of shear modulus and strength in comparison to the very time-consuming experimental estimation. 相似文献
79.
80.
Mathematical models are important tools to study the excluded volume effects on reaction–diffusion systems, which are known to play an important role inside living cells. Detailed microscopic simulations with off‐lattice Brownian dynamics become computationally expensive in crowded environments. In this study, the authors therefore investigate to which extent on‐lattice approximations, the so‐called cellular automata models, can be used to simulate reactions and diffusion in the presence of crowding molecules. They show that the diffusion is most severely slowed down in the off‐lattice model, since randomly distributed obstacles effectively exclude more volume than those ordered on an artificial grid. Crowded reaction rates can be both increased and decreased by the grid structure and it proves important to model the molecules with realistic sizes when excluded volume is taken into account. The grid artefacts increase with increasing crowder density and they conclude that the computationally more efficient on‐lattice simulations are accurate approximations only for low crowder densities.Inspec keywords: reaction‐diffusion systems, cellular biophysics, biodiffusion, Brownian motion, cellular automata, molecular biophysics, molecular configurationsOther keywords: crowder density, grid artefacts, grid structure, crowded reaction rates, artificial grid, randomly distributed obstacles, crowding molecules, cellular automata models, on‐lattice approximations, crowded environments, off‐lattice Brownian dynamics, detailed microscopic simulations, living cells, mathematical models, off‐lattice reaction‐diffusion models, on‐lattice reaction‐diffusion models, excluded volume effects 相似文献