全文获取类型
收费全文 | 342482篇 |
免费 | 2369篇 |
国内免费 | 993篇 |
专业分类
化学 | 164752篇 |
晶体学 | 4899篇 |
力学 | 18468篇 |
综合类 | 9篇 |
数学 | 60432篇 |
物理学 | 97284篇 |
出版年
2019年 | 2291篇 |
2018年 | 13248篇 |
2017年 | 13088篇 |
2016年 | 10352篇 |
2015年 | 3462篇 |
2014年 | 4549篇 |
2013年 | 10940篇 |
2012年 | 11643篇 |
2011年 | 19893篇 |
2010年 | 12493篇 |
2009年 | 12698篇 |
2008年 | 15626篇 |
2007年 | 17857篇 |
2006年 | 9069篇 |
2005年 | 9265篇 |
2004年 | 8857篇 |
2003年 | 8610篇 |
2002年 | 7596篇 |
2001年 | 7539篇 |
2000年 | 5931篇 |
1999年 | 4497篇 |
1998年 | 4032篇 |
1997年 | 3974篇 |
1996年 | 3772篇 |
1995年 | 3442篇 |
1994年 | 3563篇 |
1993年 | 3285篇 |
1992年 | 3718篇 |
1991年 | 3731篇 |
1990年 | 3651篇 |
1989年 | 3514篇 |
1988年 | 3626篇 |
1987年 | 3522篇 |
1986年 | 3339篇 |
1985年 | 4407篇 |
1984年 | 4675篇 |
1983年 | 3911篇 |
1982年 | 4045篇 |
1981年 | 3968篇 |
1980年 | 3953篇 |
1979年 | 3922篇 |
1978年 | 4225篇 |
1977年 | 4126篇 |
1976年 | 4187篇 |
1975年 | 3864篇 |
1974年 | 3903篇 |
1973年 | 4075篇 |
1972年 | 2867篇 |
1971年 | 2385篇 |
1970年 | 2184篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Mieko Tanaka-Yamawaki 《Annals of the Institute of Statistical Mathematics》2003,55(2):437-446
Contrary to the common sense in economics and financial engineering, price fluctuations at very fine level of motion exhibit
various evidences against the efficient market hypothesis. We attempt to investigate this issue by studying extensive amount
of foreign currency exchange data for over five years at the finest level of resolution. We specifically focus on the proposed
stability in binomial conditional probabilities originally found in much smaller examples of financial time series. In order
to handle very large data, we have written an efficient program in C that automatically generates those conditional probabilities.
It is found that the stability is maintained for extremely large time duration that covers almost the entire period. Based
on the length of conditions for which the conditional probabilities are distinguishable each other, we identify the length
of memory being less than 3 movements. 相似文献
992.
Yi Liu David D. Díaz Adrian A. Accurso K. Barry Sharpless Valery V. Fokin M. G. Finn 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5182-5189
1,2,3‐Triazole‐based polymers generated from the Cu(I)‐catalyzed cycloaddition between multivalent azides and acetylenes are effective adhesive materials for metal surfaces. The adhesive capacities of candidate mixtures of azide and alkyne components were measured by a modified peel test, using a customized adhesive tester. A particularly effective tetravalent alkyne and trivalent azide combination was identified, giving exceptional strength that matches or exceeds the best commercial formulations. The addition of Cu catalyst was found to be important for the synthesis of stronger adhesive polymers when cured at room temperature. Heating also accelerated curing rates, but the maximum adhesive strengths achieved at both room temperature and high temperature were the same, suggesting that crosslinking reaches the same advanced point in all cases. Polytriazoles also form adhesives to aluminum, but copper is bound more effectively, presumably because active Cu(I) ions may be leached from the surface to promote crosslinking and adhesion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5182–5189, 2007 相似文献
993.
S. A. Klimin M. N. Popova E. P. Chukalina B. Z. Malkin A. R. Zakirov E. Antic-Fidancev Ph. Goldner P. Aschehoug G. Dhalenne 《Physics of the Solid State》2005,47(8):1425-1430
The absorption spectra of Yb2Ti2O7 single crystals and the luminescence and luminescence excitation spectra of Y2Ti2O7: Yb (1%) polycrystals were studied in the temperature range 4.2–300 K. The spectra were analyzed in terms of the crystal-field
theory and the exchange-charge model. Based on the set of crystal-field parameters found for Yb2Ti2O7, analogous sets of parameters were determined for other rare-earth titanates and proved to be in reasonable agreement with
all available experimental data.
__________
Translated from Fizika Tverdogo Tela, Vol. 47, No. 8, 2005, pp. 1376–1380.
Original Russian Text Copyright ? 2005 by Klimin, Popova, Chukalina, Malkin, Zakirov, Antic-Fidancev, Goldner, Aschehoug,
Dhalenne. 相似文献
994.
995.
All homothetic self-similar solutions of the Brans-Dicke scalar field in three-dimensional spacetime with circular symmetry
are found in closed form. 相似文献
996.
Fabio Scardigli 《Foundations of Physics》2007,37(8):1278-1295
The Titius–Bode law for planetary distances is reviewed. A model describing the basic features of this rule in the “quantum-like”
language of a wave equation is proposed. Some considerations about the ’t Hooft idea on the quantum behavior of deterministic
systems with dissipation are discussed. 相似文献
997.
The forces acting on interacting moving atoms exposed to resonant laser radiation are calculated. It is shown that the forces acting on the atoms include the radiation pressure forces as well as the external and internal bias forces. The dependences of the forces on the atomic spacing, polarization, and laser radiation frequency are given. It is found that the internal bias force associated with the interaction of atomic dipoles via the reemitted field may play an important role in the dynamics of dense atomic ensembles in a light field. It is shown that optical size resonances appear in the system of interacting atoms at frequencies differing substantially from transition frequencies in the spectrum of atoms. It is noted that optical size resonances as well as the Doppler frequency shift in the spectrum of interacting atoms play a significant role in the processes of laser-radiation-controlled motion of the atoms. 相似文献
998.
FexNi100−x nanometric films were deposited on SiO2/Si substrates at room temperature using the pulsed laser deposition technique. The targets were Fe-Ni amorphous magnetic foils with composition Fe50Ni50, Fe35Ni65 and Fe22Ni78. Morphological and structural properties of the deposited films were investigated using scanning electron microscopy, Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, and X-ray reflectivity. Electrical and magnetic characteristics of the films were investigated by using the four-point probe and the magneto-optic Kerr effect techniques, respectively. The film properties are strictly dependent on the Fe-Ni compositional ratio. 相似文献
999.
Yu. G. Tselishchev 《Colloid Journal》2007,69(4):537-539
The capillary pressure in a liquid interlayer between two spherical particles is calculated as a function of their sizes and the wetting properties of the liquid. 相似文献
1000.
Three-dimensional (3-D) ZnO random-wall nanostructures and one-dimensional (1-D) ZnO nanorods were prepared on silicon substrates by a simple solid-vapour phase thermal sublimation technique. Optical pumped random lasing has been observed in the ZnO random-wall arrays with a threshold intensity of 0.38 MW/cm2 in the emission wavelength from 380 to 395 nm. The optical gain was attributed to the closed-loop scattering and light amplification of the ZnO random-wall. The experimental result suggests that the morphology of nanostructure is the key factor to effect random lasing. 相似文献