全文获取类型
收费全文 | 12385篇 |
免费 | 261篇 |
国内免费 | 45篇 |
专业分类
化学 | 7412篇 |
晶体学 | 111篇 |
力学 | 407篇 |
数学 | 1957篇 |
物理学 | 2804篇 |
出版年
2022年 | 115篇 |
2021年 | 132篇 |
2020年 | 143篇 |
2019年 | 145篇 |
2018年 | 137篇 |
2017年 | 112篇 |
2016年 | 228篇 |
2015年 | 205篇 |
2014年 | 227篇 |
2013年 | 707篇 |
2012年 | 469篇 |
2011年 | 580篇 |
2010年 | 402篇 |
2009年 | 336篇 |
2008年 | 518篇 |
2007年 | 479篇 |
2006年 | 492篇 |
2005年 | 443篇 |
2004年 | 472篇 |
2003年 | 374篇 |
2002年 | 361篇 |
2001年 | 212篇 |
2000年 | 213篇 |
1999年 | 175篇 |
1998年 | 143篇 |
1997年 | 159篇 |
1996年 | 199篇 |
1995年 | 147篇 |
1994年 | 153篇 |
1993年 | 180篇 |
1992年 | 173篇 |
1991年 | 177篇 |
1990年 | 135篇 |
1989年 | 146篇 |
1988年 | 152篇 |
1987年 | 193篇 |
1986年 | 169篇 |
1985年 | 231篇 |
1984年 | 217篇 |
1983年 | 167篇 |
1982年 | 187篇 |
1981年 | 204篇 |
1980年 | 202篇 |
1979年 | 191篇 |
1978年 | 181篇 |
1977年 | 188篇 |
1976年 | 156篇 |
1975年 | 179篇 |
1974年 | 138篇 |
1973年 | 144篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The generator coordinate approximation is a non-adiabatic theory of molecular systems. Its fundamental outlines were developed during the 1970's. A further analysis and first applications were published during the 1980's. In this paper, we review the present status of the theory. 相似文献
62.
Amylopectin tris(phenylcarbamate) has been evaluated as a chiral stationary phase for HPLC; the influence on its cptical resolving capabilities of mobile phase composition and nature of the alcohol used as modifier has been studied. Separation and resolution of twelve arylalcohol racemates were examined. In most instances, the stationary phase exhibited high optical resolving capacity. 相似文献
63.
64.
For a real Enriques surface Y we prove that every homology class in H1(Y (R), Z/2) can be represented by a real algebraic curve if and only if all connected components of Y(R) are orientable. Furthermore, we give a characterization of real Enriques surfaces which are Galois-Maximal and/or Z-Galois-Maximal and we determine the Brauer group of any real Enriques surface Y. 相似文献
65.
Tetsuya Okuyama Masaru Nakayama Yoshitsugu Tomokiyo Omer Van Der Biest 《Microscopy and microanalysis》2002,8(1):11-15
Lattice strains around a platelet oxygen precipitate in Si wafer is studied by energy filtering convergent-beam electron diffraction (CBED) and calculations based on the finite element method (FEM). Local lattice strains are measured from CBD patterns obtained with a probe size less than 2 nm in a specimen thicker than 450 nm. Strains measured are compressive along a direction normal to a plate of the precipitation and tensile along a direction parallel to the plate. Two-dimensional stress fields near the precipitate are obtained with FEM computer analyses by fitting the measured strains. It appears that shear stresses are concentrated at the end of the precipitate edge and the maximum shear stress at an interface between the precipitate and the Si-matrix is 1.9 GPa. It is demonstrated that a combination of the energy filtering CBED and FEM is very useful for the study of local strains near interfaces in semiconductor devices, in particular for the study of stress fields that are too steep for application of the conventional CBED technique. 相似文献
66.
Supported by a Heisenberg-scholarship of the DFG 相似文献
67.
J. Ramier L. Chazeau C. Gauthier L. Guy M. N. Bouchereau 《Journal of Polymer Science.Polymer Physics》2006,44(1):143-152
The treatment of nanoscopic silica grafted in the blend during the processing of silica‐filled styrene butadiene rubber was performed with silane, introduced at different concentrations, or at a constant concentration with a given length of alkyl chain. From swelling measurements in water and in solvent, the maximum silane content that can be grafted has been calculated as a function of the length of the silane alkyl chains as well as their efficiency to cover the silica surface. The found values are close to the values found in the literature for grafting in solution. Moreover, a direct correspondence between the length of the silane alkyl chains and their concentration has been deduced. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 143–152, 2006 相似文献
68.
Juray De Wilde Denis Constales Geraldine J. Heynderickx Guy B. Marin 《International Journal of Multiphase Flow》2007
The propagation speeds of linear waves in gas–solid suspensions depend strongly on the solids volume fraction and the wave frequency. The latter is due to gas–solid momentum transfer and allows a simple test on filtered gas–solid momentum transfer models. Such models may predict linear wave propagation speeds different from those obtained with the non-filtered model at wave frequencies higher than the filter frequency, but not at wave frequencies lower than the filter frequency. 相似文献
69.
For about thirty years, time series models with time-dependent coefficients have sometimes been considered as an alternative
to models with constant coefficients or non-linear models. Analysis based on models with time-dependent models has long suffered
from the absence of an asymptotic theory except in very special cases. The purpose of this paper is to provide such a theory
without using a locally stationary spectral representation and time rescaling. We consider autoregressive-moving average (ARMA)
models with time-dependent coefficients and a heteroscedastic innovation process. The coefficients and the innovation variance
are deterministic functions of time which depend on a finite number of parameters. These parameters are estimated by maximising
the Gaussian likelihood function. Deriving conditions for consistency and asymptotic normality and obtaining the asymptotic
covariance matrix are done using some assumptions on the functions of time in order to attenuate non-stationarity, mild assumptions
for the distribution of the innovations, and also a kind of mixing condition. Theorems from the theory of martingales and
mixtingales are used. Some simulation results are given and both theoretical and practical examples are treated.
Received 2004; Final version 23 December 2004 相似文献
70.