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991.
Xu Zhang 《Computers & Fluids》2009,38(2):340-346
Despite the importance of wall shear stress measurements in both fundamental and applied fluid dynamic problems, sensors for this application suffer from several shortcomings. A new class of wall shear stress sensor concept that addresses these shortcomings is studied numerically. The properties of a dynamic resonant shear stress sensor are determined using a specially-developed two-dimensional unsteady boundary layer code and a commercially available three-dimensional fluid model. Several characteristics of the sensors are determined using these models including: static sensitivities with and without pressure gradients, sensor design parameter effects. These results indicate that low amplitude, high resonant frequency operation associated with small sensors will have optimum performance. These results also suggest that a MEMS implementation of this sensor should provide the capability of measuring wall shear stress fluctuations in turbulent flows. 相似文献
992.
Yuming Zhou Leung H. Baowen Xu 《IEEE transactions on pattern analysis and machine intelligence》2009,35(5):607-623
Previous research shows that class size can influence the associations between object-oriented (OO) metrics and fault-proneness and therefore proposes that it should be controlled as a confounding variable when validating OO metrics on fault-proneness. Otherwise, their true associations may be distorted. However, it has not been determined whether this practice is equally applicable to other external quality attributes. In this paper, we use three size metrics, two of which are available during the high-level design phase, to examine the potentially confounding effect of class size on the associations between OO metrics and change-proneness. The OO metrics that are investigated include cohesion, coupling, and inheritance metrics. Our results, based on Eclipse, indicate that: 1) The confounding effect of class size on the associations between OO metrics and change-proneness, in general, exists, regardless of whichever size metric is used; 2) the confounding effect of class size generally leads to an overestimate of the associations between OO metrics and change-proneness; and 3) for many OO metrics, the confounding effect of class size completely accounts for their associations with change-proneness or results in a change of the direction of the associations. These results strongly suggest that studies validating OO metrics on change-proneness should also consider class size as a confounding variable. 相似文献
993.
Harmonic fields have been shown to provide effective guidance for a number of geometry processing problems. In this paper, we propose a method for fast updating of harmonic fields defined on polygonal meshes, enabling real-time insertion and deletion of constraints. Our approach utilizes the penalty method to enforce constraints in harmonic field computation. It maintains the symmetry of the Laplacian system and takes advantage of fast multi-rank updating and downdating of Cholesky factorization, achieving both speed and numerical stability. We demonstrate how the interactivity induced by fast harmonic field update can be utilized in several applications, including harmonic-guided quadrilateral remeshing, vector field design, interactive geometric detail modeling, and handle-driven shape editing and animation transfer with a dynamic handle set. 相似文献
994.
TCP is a reliable transport protocol tuned to perform well over traditional wired networks. Although it performs well for wired networks, TCP’s implicit assumption that any packet loss is due to congestion is not valid any longer in mobile ad hoc networks. It is observed that TCP induces the over-action of routing protocol and reduces the performance of the connection. Fraction window increment (FeW) scheme for TCP improves the connection performance by limiting TCP’s aggressiveness. But to some extent, this limitation is too strict in that it eliminates the possibility to deliver more bytes under the same congestion window. To solve this problem, we propose an adaptive packet size (APS) scheme to work on top of FeW for TCP. The proposed scheme utilizes the advantages of both legacy TCP and FeW to achieve high performance over multihop 802.11 networks. Extensive simulation results demonstrate that APS over FeW outperforms FeW alone by 10–25% according to different scenarios, e.g., chain-topology, grid-topology, and random-topology with mobility. 相似文献
995.
We propose a visualization based approach for digital signature authentication. Using our method, the speed and pressure aspects of a digital signature process can be clearly and intuitively conveyed to the user for digital signature authentication. Our design takes into account both the expressiveness and aesthetics of the derived visual patterns. With the visual aid provided by our method, digital signatures can be authenticated with better accuracy than using existing methods—even novices can examine the authenticity of a digital signature in most situations using our method. To validate the effectiveness of our method, we conducted a comprehensive user study which confirms positively the advantages of our approach. Our method can be employed as a new security enhancement measure for a range of business and legal applications in reality which involve digital signature authorization and authentication. 相似文献
996.
A structured P2P network based on the small world phenomenon 总被引:1,自引:0,他引:1
In this paper, we propose a new structured P2P overlay network, named SW-Uinta(small-world). In order to reduce the routing
latency, we firstly construct the Uinta network in which both physical characteristics of network and data semantic are considered.
Furthermore, based on Uinta, a nondeterministic caching strategy is employed to allow for poly-logarithmic search time while
having only a constant cache size. Compared with the deterministic caching strategy proposed by previous P2P systems, the
nondeterministic caching strategy can reduce communication overhead for maintaining the routing cache table. Cache entries
in the cache table of peer nodes can be updated by subsequent queries rather than only by running stabilization periodically.
In the following, a novel cache replacement scheme, named the SW cache replacement scheme, is used to improve lookup performance,
which has proved to satisfy the small-world principle. So we call this network SW-Uinta(small-world). After that, according
to the theoretical analysis, it can be proved that SW-Uinta(small-world) can get O((log 2
N)/k) search time with O(k) cache size. Lastly, the performance of SW-Uinta(small-world) is compared with those of other structured P2P networks such
as Chord and Uinta. It shows that SW-Uinta(small-world) can achieve improved object lookup performance and reduce maintenance
cost.
相似文献
Hai Jin (Corresponding author)Email: |
997.
Password authentication has been adopted as one of the most commonly used solutions in network environment to protect resources from unauthorized access. Recently, Lee–Kim–Yoo [S.W. Lee, H.S. Kim, K.Y. Yoo, Improvement of Chien et al.'s remote user authentication scheme using smart cards, Computer Standards & Interfaces 27 (2) (2005) 181–183] and Lee-Chiu [N.Y. Lee, Y.C. Chiu, Improved remote authentication scheme with smart card, Computer Standards & Interfaces 27 (2) (2005) 177–180] respectively proposed a smart card based password authentication scheme. We show that these two schemes are both subject to forgery attacks provided that the information stored in the smart card is disclosed by the adversary. We also propose an improved scheme with formal security proof. 相似文献
998.
Ciprian Iliescu Guolin Xu Elena Barbarini Marioara Avram Andrei Avram 《Microsystem Technologies》2009,15(8):1157-1162
This paper presents a microfluidic device for magnetophoretic separation of red blood cells from blood under continuous flow.
The separation method consists of continuous flow of a blood sample (diluted in PBS) through a microfluidic channel which
presents on the bottom “dots” of ferromagnetic layer. By applying a magnetic field perpendicular on the flowing direction,
the ferromagnetic “dots” generate a gradient of magnetic field which amplifies the magnetic force. As a result, the red blood
cells are captured on the bottom of the microfluidic channel while the rest of the blood is collected at the outlet. Experimental
results show that an average of 95% of red blood cells is trapped in the device. 相似文献
999.
1000.
针对目前电磁流量计在出厂时只标注有允许误差或准确度等级,其不确定度未予表述这一现状,依据<电磁流量计检定规程>JJG 1033-2007,进行水流量标准装置实流校验试验.分别介绍了评定的测量依据、环境条件、测量标准、被测对象、测量过程以及评定结果的使用.示值误差校准不确定度分析评定表明,该标定装置的不确定度对于电磁流量计的测量非常重要. 相似文献