全文获取类型
收费全文 | 3626篇 |
免费 | 141篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 40篇 |
综合类 | 5篇 |
化学工业 | 809篇 |
金属工艺 | 63篇 |
机械仪表 | 97篇 |
建筑科学 | 151篇 |
矿业工程 | 17篇 |
能源动力 | 63篇 |
轻工业 | 327篇 |
水利工程 | 28篇 |
石油天然气 | 13篇 |
无线电 | 296篇 |
一般工业技术 | 615篇 |
冶金工业 | 693篇 |
原子能技术 | 21篇 |
自动化技术 | 535篇 |
出版年
2023年 | 23篇 |
2022年 | 45篇 |
2021年 | 74篇 |
2020年 | 63篇 |
2019年 | 47篇 |
2018年 | 69篇 |
2017年 | 65篇 |
2016年 | 96篇 |
2015年 | 65篇 |
2014年 | 102篇 |
2013年 | 239篇 |
2012年 | 187篇 |
2011年 | 227篇 |
2010年 | 149篇 |
2009年 | 151篇 |
2008年 | 152篇 |
2007年 | 161篇 |
2006年 | 118篇 |
2005年 | 85篇 |
2004年 | 92篇 |
2003年 | 98篇 |
2002年 | 91篇 |
2001年 | 57篇 |
2000年 | 40篇 |
1999年 | 65篇 |
1998年 | 112篇 |
1997年 | 68篇 |
1996年 | 48篇 |
1995年 | 51篇 |
1994年 | 40篇 |
1993年 | 49篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 40篇 |
1989年 | 41篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 24篇 |
1985年 | 41篇 |
1984年 | 26篇 |
1983年 | 35篇 |
1982年 | 30篇 |
1981年 | 33篇 |
1980年 | 32篇 |
1979年 | 33篇 |
1978年 | 34篇 |
1977年 | 35篇 |
1976年 | 35篇 |
1975年 | 42篇 |
1974年 | 24篇 |
排序方式: 共有3773条查询结果,搜索用时 15 毫秒
91.
Marsha Chechik Arie Gurfinkel Benet Devereux Albert Lai Steve Easterbrook 《Formal Methods in System Design》2006,29(3):295-344
Multi-valued logics provide an interesting alternative to classical boolean logic for modeling and reasoning about systems. Such logics can be used for reasoning about partially-specified systems, effectively encode vacuity detection and query-checking problems, help in detecting inconsistencies, and many others.In our earlier work, we identified a useful family of multi-valued logics: those specified over finite distributive lattices where negation preserves involution, i.e., for every element a of the logic. Such structures are called quasi-boolean algebras, and model-checking over these not only extends the domain of applicability of automated reasoning to new problems, but can also speed up solutions to some classical verification problems.Symbolic model-checking over quasi-boolean algebras can be cast in terms of operations over multi-valued sets: sets whose membership functions are multi-valued. In this paper, we propose and empirically evaluate several choices for implementing multi-valued sets with decision diagrams. In particular, we describe two major approaches: (1) representing the multi-valued membership function canonically, using MDDs or ADDs; (2) representing multi-valued sets as a collection of classical sets, using a vector of either MBTDDs or BDDs. The naive implementation of (2) includes having a classical set for each value of the algebra. We exploit a result of lattice theory to reduce the number of such sets that need to be represented.The major contribution of this paper is the evaluation of the different implementations of multi-valued sets, done via a series of experiments and using several case studies.
相似文献
Steve EasterbrookEmail: |
92.
Albert C. Van Der Woerd Aarnout C. Pluygers 《Analog Integrated Circuits and Signal Processing》1993,3(2):119-125
This paper deals with a systematic approach to the common mode and the differential mode biasing of a differential transistor pair. Four different variants will be shown, two of these variants show practical importance; a practical circuit of one of these variants turns out to be the traditional long-tailed pair. This variant is mainly suited, if the input signal operates at voltage level, whereas another variant has great advantages if operation at current level occurs. Besides, the latter variant turns out to be very favorable in circuits operating with a single low supply voltage. Two practical circuits based on this variant are given. 相似文献
93.
Gang Li Jennifer Edwards Albert F. Carley Graham J. Hutchings 《Catalysis Today》2007,122(3-4):361-364
The direct synthesis of hydrogen peroxide from H2 and O2 using zeolite-supported Au-Pd catalysts is described using two zeolites, ZSM-5 and zeolite Y, using an impregnation method of preparation. The addition of Pd to Au for these catalysts significantly enhances the productivity for hydrogen peroxide. The use of zeolites as a support for Au-Pd gives higher rates of hydrogen peroxide formation when compared with alumina-supported Au catalysts prepared using a similar method. The addition of metals other than Pd is also investigated, but generally Au-Pd catalysts give the highest activity for the synthesis of hydrogen peroxide. The addition of Ru and Rh have no significant effect, but the addition of Pt does enhance the activity for the selective formation of hydrogen peroxide. 相似文献
94.
Xiaohu Yang Liping Zhao Xinyu Wang Ye Wang Jie Sun Albert Jerry Cristoforo 《Software》2012,42(2):131-157
Although quality requirements (QRs) have become a major drive in today's software development, there have been very few real‐world examples in the literature that demonstrate how to meet these requirements. This paper presents such an example. Specifically, the paper describes the design of a partition‐based distributed stock trading service system that satisfies a set of QRs related to resource utilization, performance, scalability and availability. The paper evaluates this design through detailed experiments and discusses some design alternatives and the lessons learned. Central to this design are a static load distribution strategy and a dynamic load balancing strategy. The first strategy is to achieve an initial balanced workload on the system's server cluster during the system initialization time, whereas the second strategy is to maintain this balanced workload throughout the system execution time. Together, these two strategies work in unison to ensure that the server resources are efficiently utilized; the user requests are processed with the required speed; the application is partitioned with sufficient room to scale; and the system is highly available. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
95.
D.G. Fernández-PachecoF. Albert N. Aleixos J. Conesa 《Expert systems with applications》2012,39(8):7181-7195
Important advances in natural calligraphic interfaces for CAD (Computer Aided Design) applications are being achieved, enabling the development of CAS (Computer Aided Sketching) devices that allow facing up to the conceptual design phase of a product. Recognizers play an important role in this field, allowing the interpretation of the user’s intention, but they still present some important lacks. This paper proposes a new recognition paradigm using an agent-based architecture that does not depend on the drawing sequence and takes context information into account to help decisions. Another improvement is the absence of operation modes, that is, no button is needed to distinguish geometry from symbols or gestures, and also “interspersing” and “overtracing” are accomplished. 相似文献
96.
Computational models of protein folding and ligand docking are large and complex. Few systematic methods have yet been developed to optimize the parameters in such models. We describe here an iterative parameter optimization strategy that is based on minimizing a structural error measure by descent in parameter space. At the start, we know the ‘correct’ native structure that we want the model to produce, and an initial set of parameters representing the relative strengths of interactions between the amino acids. The parameters are changed systematically until the model native structure converges as closely as possible to the correct native structure. As a test, we apply this parameter optimization method to the recently developed Gaussian model of protein folding: each amino acid is represented as a bead and all bonds, covalent and noncovalent, are represented by Hooke's law springs. We show that even though the Gaussian model has continuous degrees of freedom, parameters can be chosen to cause its ground state to be identical to that of Go-type lattice models, for which the global ground states are known. Parameters for a more realistic protein model can also be obtained to produce structures close to the real native structures in the protein database. 相似文献
97.
Osman Allen; Albert Robert; Ridderinkhof K. Richard; Band Guido; van der Molen Maurits 《Canadian Metallurgical Quarterly》2006,32(4):986
A frequency analysis was used to tag cortical activity from imagined rhythmic movements. Participants synchronized overt and imagined taps with brief visual stimuli presented at a constant rate, alternating between left and right index fingers. Brain potentials were recorded from across the scalp and topographic maps made of their power at the alternation frequency between left and right taps. Two prominent power foci occurred in each hemisphere for both overt and imagined taps, one over sensorimotor cortex and the other over posterior parietal cortex, with homologous foci in opposite hemispheres arising from oscillations 180° out of phase. These findings demonstrate temporal isomorphism at a neural level between overt and imagined movements and illustrate a new approach to studying covert actions. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
98.
Electrokinetic Remediation of Cadmium-Contaminated Clay 总被引:1,自引:0,他引:1
Electrokinetic extraction has been demonstrated to be very effective in removing heavy metals from Georgia kaolinite. The relatively high removal efficiency depends on the extremely acidic soil environment generated by the electrokinetic process. However, the efficiency observed in Georgia kaolinite cannot be achieved in soils of high acid/base buffer capacity without enhancement. In this study, the effect of ethylenediaminetetraacetic acid (EDTA) to enhance electrokinetic extraction of cadmium from Milwhite kaolinite was examined. The influence of electro-osmotic flow direction on the migration of cadmium, EDTA, and their complexes were also investigated. It was observed that injection of EDTA from the cathode reservoir by a reverse electro-osmotic flow could mobilize the cadmium in the specimen effectively. A less significant mobilization of cadmium was observed when the electro-osmotic flow was directed toward the cathode. However, accumulation of cadmium near the anode was observed regardless of the electro-osmotic flow direction. 相似文献
99.
Recent proposals for multi-paradigm declarative programming combine the most important features of functional, logic and concurrent programming into a single framework. The operational semantics of these languages is usually based on a combination of narrowing and residuation. In this paper, we introduce a non-standard, residualizing semantics for multi-paradigm declarative programs and prove its equivalence with a standard operational semantics. Our residualizing semantics is particularly relevant within the area of program transformation where it is useful, e.g., to perform computations during partial evaluation. Thus, the proof of equivalence is a crucial result to demonstrate the correctness of (existing) partial evaluation schemes. 相似文献
100.
A set of perception experiments, using reiterant and lexicalised speech, was designed to perform a diagnostic of the relative implication of prosody in the segmentation and hierarchisation of speech. Both natural and synthetic intonation were evaluated. Then, two distance measures—correlation and root-mean-square distance on the acoustic parameters (F0, syllabic duration and intensity)—were applied to match the perception results. This objective vs. subjective comparison underlines which acoustic cues are used by listeners to judge the adequacy of prosody in performing a given function such as demarcation. Results can be summarized by a scale of the perceptual distance between two demarcation functions. This study also points out the ability of listeners to retrieve pertinent information on the basis of pure prosodic stimuli. 相似文献