全文获取类型
收费全文 | 5500篇 |
免费 | 235篇 |
国内免费 | 23篇 |
专业分类
化学 | 3645篇 |
晶体学 | 40篇 |
力学 | 130篇 |
数学 | 743篇 |
物理学 | 1200篇 |
出版年
2023年 | 54篇 |
2022年 | 69篇 |
2021年 | 99篇 |
2020年 | 140篇 |
2019年 | 139篇 |
2018年 | 92篇 |
2017年 | 74篇 |
2016年 | 223篇 |
2015年 | 166篇 |
2014年 | 202篇 |
2013年 | 300篇 |
2012年 | 415篇 |
2011年 | 515篇 |
2010年 | 240篇 |
2009年 | 152篇 |
2008年 | 338篇 |
2007年 | 351篇 |
2006年 | 330篇 |
2005年 | 300篇 |
2004年 | 217篇 |
2003年 | 152篇 |
2002年 | 131篇 |
2001年 | 63篇 |
2000年 | 58篇 |
1999年 | 45篇 |
1998年 | 33篇 |
1997年 | 30篇 |
1996年 | 51篇 |
1995年 | 45篇 |
1994年 | 40篇 |
1993年 | 48篇 |
1992年 | 46篇 |
1991年 | 29篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1987年 | 19篇 |
1986年 | 23篇 |
1985年 | 27篇 |
1984年 | 18篇 |
1983年 | 23篇 |
1982年 | 36篇 |
1981年 | 33篇 |
1980年 | 24篇 |
1979年 | 38篇 |
1978年 | 24篇 |
1977年 | 33篇 |
1976年 | 31篇 |
1975年 | 19篇 |
1974年 | 17篇 |
1973年 | 55篇 |
排序方式: 共有5758条查询结果,搜索用时 31 毫秒
91.
Finitary Markov processes are described in G. Morvai and B. Weiss, Prediction for discrete time series, Probability Theory and Related Fields 132 (2005), 1–12. The transition functions of finitary Markov processes are residually locally constant g-functions that can be extended by continuity to their maximal domain of definition. The study of their associated symbolic
dynamics leads one to the D-shifts as introduced in W. Krieger, On g-functions for subshifts, Institute of Mathematical Statistics Lecture Notes-Monograph Series, Vol. 48, Dynamics & Stochastics, arXiv:math.DS/0608259,
(2006), 306–316, We study the phenomena that can arise in residually locally constant and locally constant maximally defined
g-functions on D-shifts, Markov shifts and synchronizing systems with respect to future measures and g-measures 相似文献
92.
Error-rate measurements have been performed on an experimental all-optical regenerator at 140 Mbit s−1 for a range of input wavelengths in the 1.5-μm band. The best sensitivity was −40 dB m and the maximum gain 31.5 dB from facet to facet. Wavelength translations from −11 to +24 nm were obtained for a penalty of less than 5 dB. The regenerator used the interaction of the input signal with an optical clock waveform in a bistable laser amplifier to re-time the signal and restore the data levels. Future applications may include use in a repeater, as an interface in a wavelength-multiplexed network or as a logic element.
相似文献93.
Affolder T Akimoto H Akopian A Albrow MG Amaral P Amidei D Anikeev K Antos J Apollinari G Arisawa T Artikov A Asakawa T Ashmanskas W Azfar F Azzi-Bacchetta P Bacchetta N Bachacou H Bailey S de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Baroiant S Barone M Bauer G Bedeschi F Belforte S Bell WH Bellettini G Bellinger J Benjamin D Bensinger J Beretvas A Berge JP Berryhill J Bhatti A Binkley M Bisello D Bishai M Blair RE Blocker C Bloom K Blumenfeld B Blusk SR Bocci A Bodek A Bokhari W 《Physical review letters》2001,87(13):131802
We report on a measurement of the mass dependence of the forward-backward charge asymmetry, A(FB), and production cross section d sigma/dM for e(+)e(-) pairs with mass M(ee)>40 GeV/c(2). The data sample consists of 108 pb(-1) of pp macro collisions at square root of s = 1.8 TeV taken by the Collider Detector at Fermilab during 1992-1995. The measured asymmetry and d sigma/dM are compared with the predictions of the standard model and a model with an extra Z' gauge boson. 相似文献
94.
Webb Miller 《BIT Numerical Mathematics》1973,13(1):76-83
Necessary and sufficient conditions are given for quadratic convergence in interval arithmetic.Partially supported by NSF grant GJ-797. 相似文献
95.
Some classes of partial differential equations with deviating arguments in the time variable are investigated. The equations are written as abstract ordinary functional differential equations of the form , where ?A is the infinitesimal generator of a linear semigroup and F is not necessarily continuous. Existence, uniqueness, and stability properties are developed by studying the equations in appropriately chosen spaces of initial functions φ. 相似文献
96.
Bayesian inference for the power law process 总被引:2,自引:0,他引:2
Shaul K. Bar-Lev Idit Lavi Benjamin Reiser 《Annals of the Institute of Statistical Mathematics》1992,44(4):623-639
The power law process has been used to model reliability growth, software reliability and the failure times of repairable systems. This article reviews and further develops Bayesian inference for such a process. The Bayesian approach provides a unified methodology for dealing with both time and failure truncated data. As well as looking at the posterior densities of the parameters of the power law process, inference for the expected number of failures and the probability of no failures in some given time interval is discussed. Aspects of the prediction problem are examined. The results are illustrated with two data examples. 相似文献
97.
Aaltonen T Adelman J Akimoto T Albrow MG Alvarez González B Amerio S Amidei D Anastassov A Annovi A Antos J Aoki M Apollinari G Apresyan A Arisawa T Artikov A Ashmanskas W Attal A Aurisano A Azfar F Azzi-Bacchetta P Azzurri P Bacchetta N Badgett W Barbaro-Galtieri A Barnes VE Barnett BA Baroiant S Bartsch V Bauer G Beauchemin PH Bedeschi F Bednar P Behari S Bellettini G Bellinger J Belloni A Benjamin D Beretvas A Beringer J Berry T Bhatti A Binkley M Bisello D Bizjak I Blair RE Blocker C 《Physical review letters》2008,100(10):101802
We have performed a search for B(s)(0) --> micro(+) micro(-) and B(0) --> micro(+) micro(-) decays in pp collisions at square root s = 1.96 TeV using 2 fb(-1) of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron Collider. The observed number of B(s)(0) and B0 candidates is consistent with background expectations. The resulting upper limits on the branching fractions are B(B(s)0) --> micro(+) micro(-)) <5.8 x 10(-8) and B(B(0) --> micro(+) micro(-))<1.8 x 10(-8) at 95% C.L. 相似文献
98.
Background
Tone languages such as Thai and Mandarin Chinese use differences in fundamental frequency (F0, pitch) to distinguish lexical meaning. Previous behavioral studies have shown that native speakers of a non-tone language have difficulty discriminating among tone contrasts and are sensitive to different F0 dimensions than speakers of a tone language. The aim of the present ERP study was to investigate the effect of language background and training on the non-attentive processing of lexical tones. EEG was recorded from 12 adult native speakers of Mandarin Chinese, 12 native speakers of American English, and 11 Thai speakers while they were watching a movie and were presented with multiple tokens of low-falling, mid-level and high-rising Thai lexical tones. High-rising or low-falling tokens were presented as deviants among mid-level standard tokens, and vice versa. EEG data and data from a behavioral discrimination task were collected before and after a two-day perceptual categorization training task.Results
Behavioral discrimination improved after training in both the Chinese and the English groups. Low-falling tone deviants versus standards elicited a mismatch negativity (MMN) in all language groups. Before, but not after training, the English speakers showed a larger MMN compared to the Chinese, even though English speakers performed worst in the behavioral tasks. The MMN was followed by a late negativity, which became smaller with improved discrimination. The High-rising deviants versus standards elicited a late negativity, which was left-lateralized only in the English and Chinese groups.Conclusion
Results showed that native speakers of English, Chinese and Thai recruited largely similar mechanisms when non-attentively processing Thai lexical tones. However, native Thai speakers differed from the Chinese and English speakers with respect to the processing of late F0 contour differences (high-rising versus mid-level tones). In addition, native speakers of a non-tone language (English) were initially more sensitive to F0 onset differences (low-falling versus mid-level contrast), which was suppressed as a result of training. This result converges with results from previous behavioral studies and supports the view that attentive as well as non-attentive processing of F0 contrasts is affected by language background, but is malleable even in adult learners. 相似文献99.
The influence of material and thickness on the subwavelength imaging performance of a negative dielectric constant slab is studied. Resonance in the plane-wave transfer function produces a high spatial frequency ripple that could be useful in fabricating periodic structures. A cost function based on the plane-wave transfer function provides a useful metric to evaluate the planar slab lens performance, and using this, the optimal slab dielectric constant can be determined. 相似文献
100.
Benjamin Y. Ku Mei-Lin ChanZhiya Ma David A. Horsley 《Journal of magnetism and magnetic materials》2008
Optical detection of the frequency-dependent magnetic relaxation signal is used to monitor the binding of biological molecules to magnetic nanoparticles in a ferrofluid. Biological binding reactions cause changes in the magnetic relaxation signal due to an increase in the average hydrodynamic diameter of the nanoparticles. To allow the relaxation signal to be detected in dilute ferrofluids, measurements are made using a balanced photodetector, resulting in a 25 μV/√Hz noise floor, within 50% of the theoretical limit imposed by photon shot noise. Measurements of a ferrofluid composed of magnetite nanoparticles coated with anti-IgG antibodies show that the average hydrodynamic diameter increases from 115.2 to 125.4 nm after reaction with IgG. 相似文献