全文获取类型
收费全文 | 9798篇 |
免费 | 719篇 |
国内免费 | 666篇 |
专业分类
电工技术 | 602篇 |
综合类 | 639篇 |
化学工业 | 227篇 |
金属工艺 | 313篇 |
机械仪表 | 949篇 |
建筑科学 | 338篇 |
矿业工程 | 92篇 |
能源动力 | 181篇 |
轻工业 | 47篇 |
水利工程 | 234篇 |
石油天然气 | 158篇 |
武器工业 | 91篇 |
无线电 | 1031篇 |
一般工业技术 | 449篇 |
冶金工业 | 97篇 |
原子能技术 | 86篇 |
自动化技术 | 5649篇 |
出版年
2024年 | 12篇 |
2023年 | 76篇 |
2022年 | 88篇 |
2021年 | 129篇 |
2020年 | 137篇 |
2019年 | 152篇 |
2018年 | 145篇 |
2017年 | 229篇 |
2016年 | 217篇 |
2015年 | 304篇 |
2014年 | 470篇 |
2013年 | 470篇 |
2012年 | 562篇 |
2011年 | 704篇 |
2010年 | 450篇 |
2009年 | 607篇 |
2008年 | 605篇 |
2007年 | 743篇 |
2006年 | 655篇 |
2005年 | 615篇 |
2004年 | 540篇 |
2003年 | 435篇 |
2002年 | 367篇 |
2001年 | 281篇 |
2000年 | 256篇 |
1999年 | 254篇 |
1998年 | 243篇 |
1997年 | 232篇 |
1996年 | 207篇 |
1995年 | 176篇 |
1994年 | 172篇 |
1993年 | 120篇 |
1992年 | 99篇 |
1991年 | 83篇 |
1990年 | 69篇 |
1989年 | 52篇 |
1988年 | 59篇 |
1987年 | 23篇 |
1986年 | 12篇 |
1985年 | 29篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1976年 | 7篇 |
1974年 | 6篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
81.
M. MoessnerAuthor VitaeGul N. KhanAuthor Vitae 《Computer Networks》2012,56(1):273-286
Privacy and security concerns inhibit the fast adaption of RFID technology for many applications. A number of authentication protocols that address these concerns have been proposed but real-world solutions that are secure, maintain low communication cost and can be integrated into the ubiquitous EPCglobal Class 1 Generation 2 tag protocol (C1G2) are still needed and being investigated. We present a novel authentication protocol, which offers a high level of security through the combination of a random key scheme with a strong cryptography. The protocol is applicable to resource, power and computationally constraint platforms such as RFID tags. Our investigation shows that it can provide mutual authentication, untraceability, forward and backward security as well as resistance to replay, denial-ofth-service and man-in-the-middle attacks, while retaining a competitive communication cost. The protocol has been integrated into the EPCglobal C1G2 tag protocol, which assures low implementation cost. We also present a successful implementation of our protocol on real-world components such as the INTEL WISP UHF RFID tag and a C1G2 compliant reader. 相似文献
82.
Design of optimal plans for environmental planning and management applications should ideally consider the multiple quantitative and qualitative criteria relevant to the problem. For example, in ground water monitoring design problems, qualitative criteria such as acceptable spatial extent and shape of the contaminant plume predicted from the monitored locations can be equally important as the typical quantitative criteria such as economic costs and contaminant prediction accuracy. Incorporation of qualitative criteria in the problem-solving process is typically done in one of two ways: (a) quantifying approximate representations of the qualitative criteria, which are then used as additional criteria during the optimization process, or (b) post-optimization analysis of designs by experts to evaluate the overall performance of the optimized designs with respect to the qualitative criteria. These approaches, however, may not adequately represent all of the relevant qualitative information that affect a human expert involved in design (e.g. engineers, stakeholders, regulators, etc.), and do not necessarily incorporate the effect of the expert's own learning process on the suitability of the final design. The Interactive Genetic Algorithm with Mixed Initiative Interaction (IGAMII) is a novel approach that addresses these limitations by using a collaborative human-computer search strategy to assist users in designing optimized solutions to their applications, while also learning about their problem. The algorithm adaptively learns from the expert's feedback, and explores multiple designs that meet her/his criteria using both the human expert and a simulated model of the expert's responses in a collaborative fashion. The algorithm provides an introspection-based learning framework for the human expert and uses the human's subjective confidence measures to adjust the optimization search process to the transient learning process of the user. This paper presents the design and testing of this computational framework, and the benefits of using this approach for solving groundwater monitoring design problems. 相似文献
83.
Analog circuits are one of the most important parts of modern electronic systems and the failure of electronic hardware presents a critical threat to the completion of modern aircraft, spacecraft, and robot missions. Compared to digital circuits, designing fault-tolerant analog circuits is a difficult and knowledge-intensive task. A simple but powerful method for robustness is a redundancy approach to use multiple circuits instead of single one. For example, if component failures occur, other redundant components can replace the functions of broken parts and the system can still work. However, there are several research issues to make the redundant system automatically. In this paper, we used evolutionary computation to generate multiple analog circuits automatically and then we combined the solutions to generate robust outputs. Evolutionary computation is a natural way to produce multiple redundant solutions because it is a population-based search. Experimental results on the evolution of the low-pass, high-pass and band-stop filters show that the combination of multiple evolved analog circuits produces results that are more robust than those of the best single circuit. 相似文献
84.
Williams Ludwell Harrison III 《LISP and Symbolic Computation》1989,2(3-4):179-396
Lisp and its descendants are among the most important and widely used of programming languages. At the same time, parallelism in the architecture of computer systems is becoming commonplace. There is a pressing need to extend the technology of automatic parallelization that has become available to Fortran programmers of parallel machines, to the realm of Lisp programs and symbolic computing. In this paper we present a comprehensive approach to the compilation of Scheme programs for shared-memory multiprocessors. Our strategy has two principal components:interprocedural analysis andprogram restructuring. We introduceprocedure strings andstack configurations as a framework in which to reason about interprocedural side-effects and object lifetimes, and develop a system of interprocedural analysis, using abstract interpretation, that is used in the dependence analysis and memory management of Scheme programs. We introduce the transformations ofexit-loop translation andrecursion splitting to treat the control structures of iteration and recursion that arise commonly in Scheme programs. We propose an alternative representation for s-expressions that facilitates the parallel creation and access of lists. We have implemented these ideas in a parallelizing Scheme compiler and run-time system, and we complement the theory of our work with snapshots of programs during the restructuring process, and some preliminary performance results of the execution of object codes produced by the compiler.This work was supported in part by the National Science Foundation under Grant No. NSF MIP-8410110, the U.S. Department of Energy under Grant No. DE-FG02-85ER25001, the Office of Naval Research under Grant No. ONR N00014-88-K-0686, the U.S. Air Force Office of Scientific Research under Grant No. AFOSR-F49620-86-C-0136, and by a donation from the IBM Corportation. 相似文献
85.
A method capable of estimating the hydrograph from a prescribed storm for a practical mild slope upstream catchment is proposed. This method makes use of two new characteristic parameters, andS, in conjunction with the kinematic wave equation to compute lateral inflows of the main stream of the catchment. The depth profile of overland flow at any instant within the catchment and hydrograph at any location can be easily found. Lag times for individual lateral inflows are then considered and are linearly combined to obtain the hydrograph at the outlet of the catchment or depth profile of the main stream at any instant. The validity of the excess rainfall-surface runoff linear relationship in this study has also been verified with Tatsunokuchiyama catchment, and it shows good results for this computed runoff. 相似文献
86.
We describe a new parallel data structure, namely parallel heap, for exclusive-read exclusive-write parallel random access machines. To our knowledge, it is the first such data structure to efficiently implement a truly parallel priority queue based on a heap structure. Employing p processors, the parallel heap allows deletions of (p) highest priority items and insertions of (p) new items, each in O(log n) time, where n is the size of the parallel heap. Furthermore, it can efficiently utilize processors in the range 1 through n.This work was supported by U.S. Army's PM-TRADE contract N61339-88-g-0002, Florida High Technology and Industry grant 11-28-716, and Georgia State University's internal research support during spring and summer quarters, 1991. 相似文献
87.
Paul Feautrier 《International journal of parallel programming》1992,21(6):389-420
This paper extends the algorithms which were developed in Part I to cases in which there is no affine schedule, i.e. to problems whose parallel complexity is polynomial but not linear. The natural generalization is to multidimensional schedules with lexicographic ordering as temporal succession. Multidimensional affine schedules, are, in a sense, equivalent to polynomial schedules, and are much easier to handle automatically. Furthermore, there is a strong connection between multidimensional schedules and loop nests, which allows one to prove that a static control program always has a multidimensional schedule. Roughly, a larger dimension indicates less parallelism. In the algorithm which is presented here, this dimension is computed dynamically, and is just sufficient for scheduling the source program. The algorithm lends itself to a divide and conquer strategy. The paper gives some experimental evidence for the applicability, performances and limitations of the algorithm. 相似文献
88.
89.
研究鸟体本构模型的动力学过程,是飞行器抗鸟撞,保证飞行安全的重要问题。由于鸟体模型参数难确定,为得到准确而合理的鸟体参数,在已知鸟体本构模型的前提下,采用并行优化技术对本构参数进行反演。将鸟撞平板的试验结果与数值仿真结果的相对误差平方和最小作为目标函数,将待反演的鸟体参数作为设计变量,在同一撞击速度范围内,将鸟撞不同靶板分为不同工况构造并行优化反演模型。把反演得到的鸟体参数代回到鸟撞平板仿真模型中检验,经与试验结果对比,效果较好,表明采用的并行优化技术是有效的、可靠的。并行优化反演技术的实现为更准确的获取鸟体参数提供了新的思路和方法,也为提高飞行器抗鸟撞设计研究提供有益参考。 相似文献
90.
The two basic performance parameters that capture the complexity of any VLSI chip are the area of the chip,A, and the computation time,T. A systematic approach for establishing lower bounds onA is presented. This approach relatesA to the bisection flow, . A theory of problem transformation based on , which captures bothAT
2 andA complexity, is developed. A fundamental problem, namely, element uniqueness, is chosen as a computational prototype. It is shown under general input/output protocol assumptions that any chip that decides ifn elements (each with (1+)lognbits) are unique must have =(nlogn), and thus, AT2=(n
2log2
n), andA= (nlogn). A theory of VLSI transformability reveals the inherentAT
2 andA complexity of a large class of related problems.This work was supported in part by the Semiconductor Research Corporation under contract RSCH 84-06-049-6. 相似文献