全文获取类型
收费全文 | 330007篇 |
免费 | 3044篇 |
国内免费 | 933篇 |
专业分类
化学 | 164857篇 |
晶体学 | 5374篇 |
力学 | 15531篇 |
综合类 | 7篇 |
数学 | 38467篇 |
物理学 | 109748篇 |
出版年
2021年 | 3133篇 |
2020年 | 3330篇 |
2019年 | 3760篇 |
2018年 | 5200篇 |
2017年 | 5440篇 |
2016年 | 7369篇 |
2015年 | 4142篇 |
2014年 | 7030篇 |
2013年 | 15906篇 |
2012年 | 12380篇 |
2011年 | 14825篇 |
2010年 | 11017篇 |
2009年 | 10917篇 |
2008年 | 13240篇 |
2007年 | 13197篇 |
2006年 | 12145篇 |
2005年 | 10524篇 |
2004年 | 9835篇 |
2003年 | 8689篇 |
2002年 | 8676篇 |
2001年 | 10393篇 |
2000年 | 7656篇 |
1999年 | 5969篇 |
1998年 | 4973篇 |
1997年 | 4812篇 |
1996年 | 4479篇 |
1995年 | 3865篇 |
1994年 | 3820篇 |
1993年 | 3702篇 |
1992年 | 4096篇 |
1991年 | 4307篇 |
1990年 | 4097篇 |
1989年 | 4009篇 |
1988年 | 3780篇 |
1987年 | 3917篇 |
1986年 | 3685篇 |
1985年 | 4634篇 |
1984年 | 4684篇 |
1983年 | 3886篇 |
1982年 | 3974篇 |
1981年 | 3698篇 |
1980年 | 3649篇 |
1979年 | 3915篇 |
1978年 | 3902篇 |
1977年 | 3906篇 |
1976年 | 3880篇 |
1975年 | 3675篇 |
1974年 | 3615篇 |
1973年 | 3650篇 |
1972年 | 2603篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
861.
We construct weighted modifications of statistical modeling of an ensemble of interacting particles which is connected with approximate solution of a nonlinear Boltzmann equation. 相似文献
862.
The effects of stimulus frequency and intensity on response patterns (PST histograms) to tone burst stimulation were examined in differently tuned saccular fibers of the goldfish. In addition, the sensitivity of these fibers to amplitude-modulated (AM) signals of different carrier frequencies was measured. The response patterns evoked by unmodulated signals were a complex function of tuning, spontaneous activity and sensitivity of the fiber, and the frequency and intensity of the signal. Frequency-dependent response patterns were found in low-frequency fibers with best frequencies (BF) below 200 Hz. Responses in these fibers ranged from tonic to phasic in nonspontaneous fibers and included more complex patterns in spontaneously active fibers, such as suppression of evoked activity below spontaneous levels. Midfrequency fibers (BF = 500-600 Hz) showed responses similar to those in low-frequency fibers, but with less dependence on frequency. In contrast, both high-frequency (BF = 800-1000 Hz) and wideband, untuned fibers showed frequency-invariant patterns of adaptation. High-frequency fibers were equally sensitive to AM signals at all frequencies tested. The sensitivity of low-frequency fibers to AM, however, increased as a function of carrier frequency and corresponded to the degree of adaptation in response to unmodulated tones. In general, the AM sensitivity of a fiber could be predicted more by its pattern of response to unmodulated signals than by its tuning characteristics. 相似文献
863.
864.
865.
The pressure dependence of the experimental 7Li NMR spectra is reported for first stage lithium graphite (LiC6) intercalation compound at temperatures T = 232 and 293 K. This experiment together with the presented point charge model calculation of the 7Li quadrupole coupling constant allows an unambiguous determination of the sign of e2qQ/h which is negative: at p = 1 bar and T = 232 K. The averaged location of the electrons transferred from the Li intercalant to the graphite layers, as estimated in this study, is in excellent agreement with earlier theoretical energy-band calculations. The compressibility of LiC6 in the c-direction is predicted to be kc = 1.7 × 10-12cm2dyn-1, it agrees with estimates derived from the available phonon dispersion relations. 相似文献
866.
S. M. J. Kelly 《Optics Communications》1989,70(6):495-501
The effect of incorporating an empty external cavity into the feedback loop of a mode-locked laser is investigated. Particular attention is paid to the response of the mode-locking as the external cavity is detuned by a fraction of a wavelength from the round trip transit time associated with the laser. The results for two regimes of operation are presented. In the first case a series of short lived transients develop whereas the other case leads to a persistent intermittent Q-switching scenario, where mode-locking fails. The role of coupling between the cavities and the laser's memory time in relation to the results is discussed. A mechanism for the improved mode-locking observed with non-linear external cavities is suggested. 相似文献
867.
C. R. Bector S. Chandra M. K. Bector 《Journal of Optimization Theory and Applications》1989,60(2):243-260
Using a parametric approach, duality is presented for a minimax fractional programming problem that involves several ratios in the objective function.The first author is thankful to Natural Science and Engineering Research Council of Canada for financial support through Grant A-5319, and the authors are thankful to the anonymous referees for useful suggestions. 相似文献
868.
T Koizumi S Taniguchi S Hiromitsu 《The Journal of the Acoustical Society of America》1987,82(4):1179-1192
Three new two-mass models of the vocal cords are treated. First, the features, structure, and differential equations of motion are described for each of the new models and compared with those of previous models. Second, performances of the models are discussed in terms of glottal volume flow, glottal area, radiated sound pressure, trajectories of mass movement, running spectra of the output sound pressure, and perceptual naturalness of the output sound. Finally, the major effects of glottal source-vocal tract interaction including skewing, truncation, and superposition are investigated, using one of the simplest types of two-mass models and two types of load representing the vocal tract. 相似文献
869.
Yu. S. Khokhlov 《Journal of Mathematical Sciences》1991,57(4):3325-3327
Translated fromProblemy Ustoichivosti Stokhasticheskikh Modelei. Trudy Seminara, 1988, pp. 137–140. 相似文献
870.