全文获取类型
收费全文 | 6580篇 |
免费 | 575篇 |
国内免费 | 347篇 |
专业分类
化学 | 1213篇 |
晶体学 | 13篇 |
力学 | 321篇 |
综合类 | 200篇 |
数学 | 4012篇 |
物理学 | 1743篇 |
出版年
2024年 | 9篇 |
2023年 | 68篇 |
2022年 | 169篇 |
2021年 | 225篇 |
2020年 | 155篇 |
2019年 | 186篇 |
2018年 | 194篇 |
2017年 | 265篇 |
2016年 | 270篇 |
2015年 | 234篇 |
2014年 | 347篇 |
2013年 | 636篇 |
2012年 | 304篇 |
2011年 | 379篇 |
2010年 | 297篇 |
2009年 | 359篇 |
2008年 | 395篇 |
2007年 | 377篇 |
2006年 | 326篇 |
2005年 | 294篇 |
2004年 | 258篇 |
2003年 | 234篇 |
2002年 | 209篇 |
2001年 | 168篇 |
2000年 | 135篇 |
1999年 | 145篇 |
1998年 | 152篇 |
1997年 | 99篇 |
1996年 | 92篇 |
1995年 | 93篇 |
1994年 | 72篇 |
1993年 | 53篇 |
1992年 | 41篇 |
1991年 | 37篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 27篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有7502条查询结果,搜索用时 437 毫秒
31.
An approach to dealing with missing data, both during the design and normal operation of a neuro-fuzzy classifier is presented in this paper. Missing values are processed within a general fuzzy min–max neural network architecture utilising hyperbox fuzzy sets as input data cluster prototypes. An emphasis is put on ways of quantifying the uncertainty which missing data might have caused. This takes a form of classification procedure whose primary objective is the reduction of a number of viable alternatives rather than attempting to produce one winning class without supporting evidence. If required, the ways of selecting the most probable class among the viable alternatives found during the primary classification step, which are based on utilising the data frequency information, are also proposed. The reliability of the classification and the completeness of information is communicated by producing upper and lower classification membership values similar in essence to plausibility and belief measures to be found in the theory of evidence or possibility and necessity values to be found in the fuzzy sets theory. Similarities and differences between the proposed method and various fuzzy, neuro-fuzzy and probabilistic algorithms are also discussed. A number of simulation results for well-known data sets are provided in order to illustrate the properties and performance of the proposed approach. 相似文献
32.
Alex Hellsten 《Archive for Mathematical Logic》2006,45(6):705-714
We extract some properties of Mahlo’s operation and show that some other very natural operations share these properties. The weakly compact sets form a similar hierarchy as the stationary sets. The height of this hierarchy is a large cardinal property connected to saturation properties of the weakly compact ideal. 相似文献
33.
34.
本文讨论由L2深度修正得到的L2深度相应的样本深度的性质,得到了样本深度的相合性和渐近正态性,并证明了它在任意紧集上的一致相合性.最后,基于上述性质简要讨论了样本深度等高的一些性质. 相似文献
35.
36.
Jaeyoung Chung 《Journal of Mathematical Analysis and Applications》2004,300(2):376-350
We reformulate and prove the Hyers–Ulam–Rassias stability of Cauchy equation in the space of Schwartz tempered distributions and Fourier hyperfunctions. 相似文献
37.
We study the number of determining modes necessary for continuous data assimilation in the two-dimensional incompressible Navier–Stokes equations. Our focus is on how the spatial structure of the body forcing affects the rate of continuous data assimilation and the number of determining modes. We treat this problem analytically by proving a convergence result depending on the H
–1 norm of f and computationally by considering a family of forcing functions with identical Grashof numbers that are supported on different annuli in Fourier space. The rate of continuous data assimilation and the number of determining modes is shown to depend strongly on the length scales present in the forcing. 相似文献
38.
Telecommunications systems have recently undergone significant innovations. These call for suitable statistical models that can properly describe the behaviour of the input traffic in a network. Here we use fractional Brownian motion (FBM) to model cumulative traffic network, thus taking into account the possible presence of long‐range dependence in the data. A Bayesian approach is devised in such a way that we are able to: (a) estimate the Hurst parameter H of the FBM; (b) estimate the overflow probability which is a parameter measuring the quality of service of a network: (c) develop a test for comparing the null hypothesis of long‐range dependence in the data versus the alternative of short‐range dependence. In order to achieve these inferential results, we elaborate an MCMC sampling scheme whose output enables us to obtain an approximation of the quantities of interest. An application to three real datasets, corresponding to three different levels of traffic, is finally considered. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
39.
Let a text of u characters over an alphabet of size σ be compressible to n phrases by the LZ78 algorithm. We show how to build a data structure based on the Ziv–Lempel trie, called the LZ-index, that takes 4nlog2n(1+o(1)) bits of space (that is, 4 times the entropy of the text for ergodic sources) and reports the R occurrences of a pattern of length m in worst case time O(m3logσ+(m+R)logn). We present a practical implementation of the LZ-index, which is faster than current alternatives when we take into consideration the time to report the positions or text contexts of the occurrences found. 相似文献
40.
Nguyen Minh Chuong Bui Kien Cuong 《Proceedings of the American Mathematical Society》2004,132(12):3589-3597
A class of Cauchy problems for interesting complicated periodic pseudodifferential equations is considered. By the Galerkin-wavelet method and with weak solutions one can find sufficient conditions to establish convergence estimates of weak Galerkin-wavelet solutions to a Cauchy problem for this class of equations.