全文获取类型
收费全文 | 43917篇 |
免费 | 950篇 |
国内免费 | 178篇 |
专业分类
电工技术 | 572篇 |
综合类 | 630篇 |
化学工业 | 4719篇 |
金属工艺 | 612篇 |
机械仪表 | 900篇 |
建筑科学 | 837篇 |
矿业工程 | 390篇 |
能源动力 | 419篇 |
轻工业 | 2140篇 |
水利工程 | 608篇 |
石油天然气 | 48篇 |
武器工业 | 4篇 |
无线电 | 2042篇 |
一般工业技术 | 3618篇 |
冶金工业 | 21702篇 |
原子能技术 | 199篇 |
自动化技术 | 5605篇 |
出版年
2024年 | 55篇 |
2023年 | 196篇 |
2022年 | 126篇 |
2021年 | 129篇 |
2019年 | 51篇 |
2018年 | 467篇 |
2017年 | 686篇 |
2016年 | 1078篇 |
2015年 | 793篇 |
2014年 | 451篇 |
2013年 | 451篇 |
2012年 | 2160篇 |
2011年 | 2473篇 |
2010年 | 694篇 |
2009年 | 797篇 |
2008年 | 654篇 |
2007年 | 657篇 |
2006年 | 579篇 |
2005年 | 3374篇 |
2004年 | 2580篇 |
2003年 | 2072篇 |
2002年 | 883篇 |
2001年 | 755篇 |
2000年 | 293篇 |
1999年 | 641篇 |
1998年 | 6268篇 |
1997年 | 3882篇 |
1996年 | 2548篇 |
1995年 | 1480篇 |
1994年 | 1106篇 |
1993年 | 1125篇 |
1992年 | 257篇 |
1991年 | 321篇 |
1990年 | 322篇 |
1989年 | 287篇 |
1988年 | 306篇 |
1987年 | 232篇 |
1986年 | 212篇 |
1985年 | 182篇 |
1984年 | 78篇 |
1983年 | 85篇 |
1982年 | 134篇 |
1981年 | 184篇 |
1980年 | 201篇 |
1979年 | 73篇 |
1978年 | 102篇 |
1977年 | 624篇 |
1976年 | 1332篇 |
1975年 | 101篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Attribute selection with fuzzy decision reducts 总被引:2,自引:0,他引:2
Rough set theory provides a methodology for data analysis based on the approximation of concepts in information systems. It revolves around the notion of discernibility: the ability to distinguish between objects, based on their attribute values. It allows to infer data dependencies that are useful in the fields of feature selection and decision model construction. In many cases, however, it is more natural, and more effective, to consider a gradual notion of discernibility. Therefore, within the context of fuzzy rough set theory, we present a generalization of the classical rough set framework for data-based attribute selection and reduction using fuzzy tolerance relations. The paper unifies existing work in this direction, and introduces the concept of fuzzy decision reducts, dependent on an increasing attribute subset measure. Experimental results demonstrate the potential of fuzzy decision reducts to discover shorter attribute subsets, leading to decision models with a better coverage and with comparable, or even higher accuracy. 相似文献
992.
Vladim?´r Janiš 《Information Sciences》2010,180(7):1134-1137
We consider the system of intuitionistic fuzzy sets (IF-sets) in a universe X and study the cuts of an IF-set. Suppose a left continuous triangular norm is given. The t-norm based cut (level set) of an IF-set is defined in a way that binds the membership and nonmembership functions via the triangular norm. This is an extension of usual cuts of IF-sets. We show that the system of these cuts fulfils analogical properties as usual systems of cuts. However, it is not possible to reconstruct an IF-set from the system of t-norm based cuts. 相似文献
993.
Matej Perše Author Vitae Matej Kristan Author Vitae Author Vitae Gašper Muši? Author Vitae Author Vitae Stanislav Kova?i? Author Vitae 《Pattern recognition》2010,43(4):1491-1501
This paper presents the use of place/transition petri nets (PNs) for the recognition and evaluation of complex multi-agent activities. The PNs were built automatically from the activity templates that are routinely used by experts to encode domain-specific knowledge. The PNs were built in such a way that they encoded the complex temporal relations between the individual activity actions. We extended the original PN formalism to handle the propagation of evidence using net tokens. The evaluation of the spatial and temporal properties of the actions was carried out using trajectory-based action detectors and probabilistic models of the action durations. The presented approach was evaluated using several examples of real basketball activities. The obtained experimental results suggest that this approach can be used to determine the type of activity that a team has performed as well as the stage at which the activity ended. 相似文献
994.
In this paper we propose a new circularity measure which defines the degree to which a shape differs from a perfect circle. The new measure is easy to compute and, being area based, is robust—e.g., with respect to noise or narrow intrusions. Also, it satisfies the following desirable properties:
- •
- it ranges over (0,1] and gives the measured circularity equal to 1 if and only if the measured shape is a circle;
- •
- it is invariant with respect to translations, rotations and scaling.
995.
Dimitra?Giannakopoulou David?H.?Bushnell Johann?SchumannEmail author Heinz?Erzberger Karen?Heere 《Annals of Mathematics and Artificial Intelligence》2011,63(1):5-30
In order to address the rapidly increasing load of air traffic operations, innovative algorithms and software systems must
be developed for the next generation air traffic control. Extensive verification of such novel algorithms is key for their
adoption by industry. Separation assurance algorithms aim at predicting if two aircraft will get closer to each other than
a minimum safe distance; if loss of separation is predicted, they also propose a change of course for the aircraft to resolve
this potential conflict. In this paper, we report on our work towards developing an advanced testing framework for separation
assurance. Our framework supports automated test case generation and testing, and defines test oracles that capture algorithm
requirements. We discuss three different approaches to test-case generation, their application to a separation assurance prototype,
and their respective strengths and weaknesses. We also present an approach for statistical analysis of the large numbers of
test results obtained from our framework. 相似文献
996.
This paper proposes a novel signal transformation and interpolation approach based on the modification of DCT (Discrete Cosine Transform). The proposed algorithm can be applied to any periodic or quasi periodic waveform for time scale and/or pitch modification purposes in addition to signal reconstruction, compression, coding and packet lost concealment. The proposed algorithm has two advantages:
(i)
Since DCT does not have the explicit phase information, one does not need the cubic spline interpolation of the phase component of the sinusoidal model. (ii)
The parameters to be interpolated can be reduced because of the energy packing efficiency of the DCT. This is particularly important if signal synthesis is carried out on a remote location from the transmitted parameters.
997.
This paper proposes a novel computer vision approach that processes video sequences of people walking and then recognises
those people by their gait. Human motion carries different information that can be analysed in various ways. The skeleton
carries motion information about human joints, and the silhouette carries information about boundary motion of the human body.
Moreover, binary and gray-level images contain different information about human movements. This work proposes to recover
these different kinds of information to interpret the global motion of the human body based on four different segmented image
models, using a fusion model to improve classification. Our proposed method considers the set of the segmented frames of each
individual as a distinct class and each frame as an object of this class. The methodology applies background extraction using
the Gaussian Mixture Model (GMM), a scale reduction based on the Wavelet Transform (WT) and feature extraction by Principal
Component Analysis (PCA). We propose four new schemas for motion information capture: the Silhouette-Gray-Wavelet model (SGW)
captures motion based on grey level variations; the Silhouette-Binary-Wavelet model (SBW) captures motion based on binary
information; the Silhouette–Edge-Binary model (SEW) captures motion based on edge information and the Silhouette Skeleton
Wavelet model (SSW) captures motion based on skeleton movement. The classification rates obtained separately from these four
different models are then merged using a new proposed fusion technique. The results suggest excellent performance in terms
of recognising people by their gait. 相似文献
998.
One of the main goals of an applied research field such as software engineering is the transfer and widespread use of research
results in industry. To impact industry, researchers developing technologies in academia need to provide tangible evidence
of the advantages of using them. This can be done trough step-wise validation, enabling researchers to gradually test and
evaluate technologies to finally try them in real settings with real users and applications. The evidence obtained, together
with detailed information on how the validation was conducted, offers rich decision support material for industry practitioners
seeking to adopt new technologies and researchers looking for an empirical basis on which to build new or refined technologies.
This paper presents model for evaluating the rigor and industrial relevance of technology evaluations in software engineering.
The model is applied and validated in a comprehensive systematic literature review of evaluations of requirements engineering
technologies published in software engineering journals. The aim is to show the applicability of the model and to characterize
how evaluations are carried out and reported to evaluate the state-of-research. The review shows that the model can be applied
to characterize evaluations in requirements engineering. The findings from applying the model also show that the majority
of technology evaluations in requirements engineering lack both industrial relevance and rigor. In addition, the research
field does not show any improvements in terms of industrial relevance over time. 相似文献
999.
Although the deterministic flow shop model is one of the most widely studied problems in scheduling theory, its stochastic
analog has remained a challenge. No computationally efficient optimization procedure exists even for the general two-machine
version. In this paper, we describe three heuristic procedures for the stochastic, two-machine flow shop problem and report
on computational experiments that compare their effectiveness. We focus on heuristic procedures that can be adapted for dispatching
without the need for computer simulation or computer-based search. We find that all three procedures are capable of quickly
generating solutions close to the best known sequences, which were obtained by extensive search. 相似文献
1000.
Nobuyuki?KobayashiEmail author Tsubasa?Wago Yoshiki?Sugawara 《Multibody System Dynamics》2011,26(3):265-281
A method of reducing the system matrices of a planar flexible beam described by an absolute nodal coordinate formulation (ANCF)
is presented. In this method, we focus that the bending stiffness matrix expressed by adopting a continuum mechanics approach
to the ANCF beam element is constant when the axial strain is not very large. This feature allows to apply the Craig–Bampton
method to the equation of motion that is composed of the independent coordinates when the constraint forces are eliminated.
Four numerical examples that compare the proposed method and the conventional ANCF are demonstrated to verify the performance
and accuracy of the proposed method. From these examples, it is verified that the proposed method can describe the large deformation
effects such as dynamic stiffening due to the centrifugal force, as well as the conventional ANCF does. The use of this method
also reduces the computing time, while maintaining an acceptable degree of accuracy for the expression characteristics of
the conventional ANCF when the modal truncation number is adequately employed. This reduction in CPU time particularly pronounced
in the case of a large element number and small modal truncation number; the reduction can be verified not only in the case
of small deformation but also in the case of a fair bit large deformation. 相似文献