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101.
Luci Pirmez Jaime C. Carvalho Flávia C. Delicato Fábio Protti Luiz F.R.C. Carmo Paulo F. Pires Marcos Pirmez 《Computer Networks》2010,54(13):2117-2136
This work presents SUTIL, a mechanism for network selection in the context of next generation networks (NGN). SUTIL selection mechanism prioritizes networks with higher relevance to the application and lower energy consumption and it enables full and seamless connectivity to mobile user devices and applications. Consequently, SUTIL contributes to realize the vision of ubiquitous computing, in which services, devices, and sensor-enriched environments interact anytime, anywhere to accomplish human designed tasks. The provided solution is based on utility function and integer linear programming and it aims at: (i) maximizing the user satisfaction while meeting application QoS and (ii) minimizing the energy consumption of devices when connecting to a target network. The solution is global since it considers for a given base station all devices that are simultaneously candidate for handoff. Simulation results showed the benefits of SUTIL usage in NGN environments. 相似文献
102.
Ivan Damgård Mads Jurik Jesper Buus Nielsen 《International Journal of Information Security》2010,9(6):371-385
We propose a generalization of Paillier’s probabilistic public-key system, in which the expansion factor is reduced and which
allows to adjust the block length of the scheme even after the public key has been fixed, without losing the homomorphic property.
We show that the generalization is as secure as Paillier’s original system and propose several ways to optimize implementations
of both the generalized and the original scheme. We construct a threshold variant of the generalized scheme as well as zero-knowledge
protocols to show that a given ciphertext encrypts one of a set of given plaintexts, and protocols to verify multiplicative
relations on plaintexts. We then show how these building blocks can be used for applying the scheme to efficient electronic
voting. This reduces dramatically the work needed to compute the final result of an election, compared to the previously best
known schemes. We show how the basic scheme for a yes/no vote can be easily adapted to casting a vote for up to t out of L candidates. The same basic building blocks can also be adapted to provide receipt-free elections, under appropriate physical
assumptions. The scheme for 1 out of L elections can be optimized such that for a certain range of the other parameter values, the ballot size is logarithmic in
L. 相似文献
103.
Caio César Mori Carélo Ives Renê Venturini Pola Ricardo Rodrigues Ciferri Agma Juci Machado Traina Caetano Traina Jr Cristina Dutra de Aguiar Ciferri 《Information Systems》2011
Searching in a dataset for elements that are similar to a given query element is a core problem in applications that manage complex data, and has been aided by metric access methods (MAMs). A growing number of applications require indices that must be built faster and repeatedly, also providing faster response for similarity queries. The increase in the main memory capacity and its lowering costs also motivate using memory-based MAMs. In this paper, we propose the Onion-tree, a new and robust dynamic memory-based MAM that slices the metric space into disjoint subspaces to provide quick indexing of complex data. It introduces three major characteristics: (i) a partitioning method that controls the number of disjoint subspaces generated at each node; (ii) a replacement technique that can change the leaf node pivots in insertion operations; and (iii) range and k-NN extended query algorithms to support the new partitioning method, including a new visit order of the subspaces in k-NN queries. Performance tests with both real-world and synthetic datasets showed that the Onion-tree is very compact. Comparisons of the Onion-tree with the MM-tree and a memory-based version of the Slim-tree showed that the Onion-tree was always faster to build the index. The experiments also showed that the Onion-tree significantly improved range and k-NN query processing performance and was the most efficient MAM, followed by the MM-tree, which in turn outperformed the Slim-tree in almost all the tests. 相似文献
104.
Step sequence planning for a biped robot by means of a cylindrical shape model and a high-resolution 2.5D map 总被引:1,自引:0,他引:1
Robert CupecAuthor Vitae Ivan AleksiAuthor VitaeGünther SchmidtAuthor Vitae 《Robotics and Autonomous Systems》2011,59(2):84-100
A novel step sequence planning (SSP) method for biped-walking robots is presented. The method adopts a free space representation custom-designed for efficient biped robot motion planning. The method rests upon the approximation of the robot shape by a set of 3D cylindrical solids. This feature allows efficient determination of feasible paths in a 2.5D map, comprising stepping over obstacles and stair climbing. A SSP algorithm based on A∗-search is proposed which uses the advantages of the aforementioned environment representation. The efficiency of the proposed approach is evaluated by a series of simulations performed for eight walking scenarios. 相似文献
105.
Marija Dakulovi?Author Vitae Ivan Petrovi? Author Vitae 《Robotics and Autonomous Systems》2011,59(5):329-342
Inspired by the Witkowski’s algorithm, we introduce a novel path planning and replanning algorithm — the two-way D∗ (TWD∗) algorithm — based on a two-dimensional occupancy grid map of the environment. Unlike the Witkowski’s algorithm, which finds optimal paths only in binary occupancy grid maps, the TWD∗ algorithm can find optimal paths in weighted occupancy grid maps. The optimal path found by the TWD∗ algorithm is the shortest possible path for a given occupancy grid map of the environment. This path is more natural than the path found by the standard D∗ algorithm as it consists of straight line segments with continuous headings. The TWD∗ algorithm is tested and compared to the D∗ and Witkowski’s algorithms by extensive simulations and experimentally on a Pioneer 3DX mobile robot equipped with a laser range finder. 相似文献
106.
J. P. Carmo M. F. Silva J. F. Ribeiro R. F. Wolffenbuttel P. Alpuim J. G. Rocha L. M. Gon?alves J. H. Correia 《Microsystem Technologies》2011,17(8):1283-1291
This paper presents an approach for generating a well-defined cooling pattern over an area of tissue. An array of solid-state
microcoolers is used, which could be included in a probe that provides local cooling. This medical instrument can be used
for removal of scar tissue in the eye or for the rapid stopping of bleeding due to micro-cuts, which makes it a useful tool
to medical doctors and could make surgery more secure to the patient. The array of microcoolers is composed of 64 independent
thermo-electric elements, each controlled using an integrated circuit designed in CMOS. The independent control allows the
flexible programming of the surface temperature profile. This type of control is very suitable in case abrupt temperature
steps should be avoided. Cooling by lateral heat flow was selected in order to minimize the influence of heat by dissipation
from the electronic circuits. Moreover, a thermo-electric component with lateral heat allows fabrication of the cooling elements
using planar thin-film technology, lithography and wet etching on top of the silicon wafer. This approach is potentially CMOS
compatible, which would allow for the fabrication of the thermo-electric elements on top of a pre-fabricated CMOS wafer as
a post-process step. Each pixel is composed of thin-films of n-type bismuth telluride, Bi2Te3 and p-type antimony telluride, Sb2Te3, which are electrically interconnected as thermocouple. These materials have excellent thermoelectric characteristics, such
as thermoelectric figures-of-merit, ZT, at room temperatures of 0.84 and 0.5, respectively, which is equivalent to power-factors, PF, of 3.62 × 10−3 W K−1 m−2 and 2.81 × 10−3 W K−1 m−2, respectively. The theoretical study presented here demonstrates a cooling capability of 15°C at room temperature (300 K ≈ 27°C).
This cooling performance is sufficient to maintain a local tissue temperature at 25°C, which makes it suitable for the intended
application. A first prototype was successfully fabricated to demonstrate the concept. 相似文献
107.
Paulo Anselmo da Mota Silveira Neto Ivan do Carmo Machado John D. McGregorEduardo Santana de Almeida Silvio Romero de Lemos Meira 《Information and Software Technology》2011,53(5):407-423
Context
In software development, Testing is an important mechanism both to identify defects and assure that completed products work as specified. This is a common practice in single-system development, and continues to hold in Software Product Lines (SPL). Even though extensive research has been done in the SPL Testing field, it is necessary to assess the current state of research and practice, in order to provide practitioners with evidence that enable fostering its further development.Objective
This paper focuses on Testing in SPL and has the following goals: investigate state-of-the-art testing practices, synthesize available evidence, and identify gaps between required techniques and existing approaches, available in the literature.Method
A systematic mapping study was conducted with a set of nine research questions, in which 120 studies, dated from 1993 to 2009, were evaluated.Results
Although several aspects regarding testing have been covered by single-system development approaches, many cannot be directly applied in the SPL context due to specific issues. In addition, particular aspects regarding SPL are not covered by the existing SPL approaches, and when the aspects are covered, the literature just gives brief overviews. This scenario indicates that additional investigation, empirical and practical, should be performed.Conclusion
The results can help to understand the needs in SPL Testing, by identifying points that still require additional investigation, since important aspects regarding particular points of software product lines have not been addressed yet. 相似文献108.
Jesús P. Mena-Chalco Ives Macêdo Luiz Velho Roberto M. Cesar Jr. 《The Visual computer》2009,25(10):899-909
In this paper, we present a 3D face photography system based on a facial expression training dataset, composed of both facial range images (3D geometry) and facial texture (2D photography). The proposed system allows one to obtain a 3D geometry representation of a given face provided as a 2D photography, which undergoes a series of transformations through the texture and geometry spaces estimated. In the training phase of the system, the facial landmarks are obtained by an active shape model (ASM) extracted from the 2D gray-level photography. Principal components analysis (PCA) is then used to represent the face dataset, thus defining an orthonormal basis of texture and another of geometry. In the reconstruction phase, an input is given by a face image to which the ASM is matched. The extracted facial landmarks and the face image are fed to the PCA basis transform, and a 3D version of the 2D input image is built. Experimental tests using a new dataset of 70 facial expressions belonging to ten subjects as training set show rapid reconstructed 3D faces which maintain spatial coherence similar to the human perception, thus corroborating the efficiency and the applicability of the proposed system. 相似文献
109.
Matjaz B. Juric Author Vitae Ana Sasa Author Vitae Author Vitae Ivan Rozman Author Vitae 《Journal of Systems and Software》2009,82(8):1326-1343
Versioning is an important aspect of web service development, which has not been adequately addressed so far. In this article, we propose extensions to WSDL and UDDI to support versioning of web service interfaces at development-time and run-time. We address service-level and operation-level versioning, service endpoint mapping, and version sequencing. We also propose annotation extensions for developing versioned web services in Java. We have tested the proposed solution for versioning in two real-world environments and identified considerable improvements in service development and maintenance efficiency, improved service reuse, and simplified governance. 相似文献
110.
The bilateral filter is a nonlinear filter that smoothes a signal while preserving strong edges. It has demonstrated great
effectiveness for a variety of problems in computer vision and computer graphics, and fast versions have been proposed. Unfortunately,
little is known about the accuracy of such accelerations. In this paper, we propose a new signal-processing analysis of the
bilateral filter which complements the recent studies that analyzed it as a PDE or as a robust statistical estimator. The
key to our analysis is to express the filter in a higher-dimensional space where the signal intensity is added to the original
domain dimensions. Importantly, this signal-processing perspective allows us to develop a novel bilateral filtering acceleration
using downsampling in space and intensity. This affords a principled expression of accuracy in terms of bandwidth and sampling.
The bilateral filter can be expressed as linear convolutions in this augmented space followed by two simple nonlinearities.
This allows us to derive criteria for downsampling the key operations and achieving important acceleration of the bilateral
filter. We show that, for the same running time, our method is more accurate than previous acceleration techniques. Typically,
we are able to process a 2 megapixel image using our acceleration technique in less than a second, and have the result be
visually similar to the exact computation that takes several tens of minutes. The acceleration is most effective with large
spatial kernels. Furthermore, this approach extends naturally to color images and cross bilateral filtering. 相似文献