全文获取类型
收费全文 | 3558篇 |
免费 | 210篇 |
国内免费 | 17篇 |
专业分类
化学 | 2504篇 |
晶体学 | 13篇 |
力学 | 86篇 |
数学 | 605篇 |
物理学 | 577篇 |
出版年
2023年 | 30篇 |
2022年 | 37篇 |
2021年 | 61篇 |
2020年 | 80篇 |
2019年 | 77篇 |
2018年 | 70篇 |
2017年 | 76篇 |
2016年 | 182篇 |
2015年 | 139篇 |
2014年 | 126篇 |
2013年 | 229篇 |
2012年 | 274篇 |
2011年 | 287篇 |
2010年 | 164篇 |
2009年 | 120篇 |
2008年 | 235篇 |
2007年 | 201篇 |
2006年 | 164篇 |
2005年 | 175篇 |
2004年 | 154篇 |
2003年 | 140篇 |
2002年 | 125篇 |
2001年 | 40篇 |
2000年 | 33篇 |
1999年 | 37篇 |
1998年 | 40篇 |
1997年 | 27篇 |
1996年 | 40篇 |
1995年 | 14篇 |
1994年 | 21篇 |
1993年 | 34篇 |
1992年 | 19篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1975年 | 9篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有3785条查询结果,搜索用时 31 毫秒
11.
Additive-subtractive phase modulated speckle interferometry (ASPMSI) is a technique that minimizes the susceptibility of speckle methods to environmental noise while providing fringes of good visibility. The method requires the acquisition of two consecutive video frames of additive-speckle images of the same two deformed states of an object at a rapid enough rate such that ambient noise is not a problem. The additive-speckle images as expected are of very poor visibility due to the presence of the self-interference term. An interframe phase-modulation is introduced and the two additive-speckle images are digitally subtracted to improve the fringe visibility by removing the self-interference term. The ASPM-SI method works with in-plane and out-of-plane deformation sensitive ESPI as well as with displacement-gradient sensitive speckle-shearing interferometry. It is shown that the ASPM-SI scheme has higher visibility than conventional additive-SI and performs consistently better than subtractive-SI schemes in the presence of partial interframe speckle decorrelating optical noise. Furthermore, it is shown that the fringe visibility of the out-of-plane displacement sensitive interferometer which uses a protected reference beam separate from the object beam can be made to be essentially unity even at complete interframe decorrelation. 相似文献
12.
On‐line coupling of LC and ICP‐MS has been used for fractionation and detection of species of Cu, Fe, I, Se and Zn in human serum. It has been shown that anion exchange chromatography provided better separation capability (both intra‐ and inter‐element) than size‐exclusion chromatography. The mobile phases for ion exchange chromatography consisted of Tris–HNO3 buffer and ammonium salt (nitrate, acetate or formate). Formate was found to be the best mobile phase counter ion, enabling good chromatographic separation, and is acceptable for mass spectrometry too. The quantitative evaluation of element concentrations adhering to individual fractions was performed by the peak area normalization method. The repeatability of results ranged from 3 to 15% (depending on the element concentration level) and represented the main part of the result uncertainty. The accuracy of Cu and Zn fraction determinations was confirmed by comparison with the isotope dilution technique. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
13.
J. Pisút N. Pisútová B. Tomásik 《The European Physical Journal C - Particles and Fields》2003,29(1):79-85
We present a few estimates of energy densities reached in heavy-ion collisions at the CERN SPS. The estimates are based on
data and models of proton-nucleus and nucleus-nucleus interactions. In all of these estimates the maximum energy density in
central Pb+Pb interactions is larger than the critical energy density GeV/fm3 following from lattice gauge theory computations. In estimates which we consider as realistic the maximum energy density
is about . In this way our analysis gives some support to claims that deconfined matter has been produced at the CERN SPS. Any definite
statement requires a deeper understanding of formation times of partons and hadrons in nuclear collisions. We also compare
our results with implicit energy estimates contained in earlier models of anomalous suppression in nuclear collisions.
Received: 3 February 2003 / Revised version: 5 March 2003 / Published online: 5 May 2003 相似文献
14.
15.
16.
Tomás Chacón Rebollo Antonio Domı́nguez Delgado Enrique D. Fernández Nieto 《Comptes Rendus Mathematique》2004,338(1):85-90
In this work we introduce a class of balanced numerical schemes, up to second order, for the solution of general non-homogeneous hyperbolic systems of conservation laws. We give a general technique to build such schemes. We also prove that they balance up to second order a large class of steady solutions in the whole domain but some subset whose measure tends to zero as the grid size decreases to zero. We finally present an application to Shallow Water equations that exhibit the good performances of some of the schemes introduced. To cite this article: T. Chacón Rebollo et al., C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
17.
18.
Tom Edgar 《Journal of Algebraic Combinatorics》2007,26(3):357-362
Twisted Bruhat orders are certain partial orders on a Coxeter system (W,S) associated to initial sections of reflection orders, which are certain subsets of the set of reflections T of a Coxeter system. We determine which subsets of T give rise to a partial order on W in the same way. 相似文献
19.
We derive the incompressible and compressible k–ε model for locally homogeneous turbulence. The model is rigorously derived on formal mathematical grounds using the MPP modelling technique. This lets us calculate by either analytical or numerical means the closure constants of the model. To cite this article: T. Chacón Rebollo, D. Franco Coronil, C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献
20.
Inhibition of the reduction of Cr(VI) at the magnetite–water interface by calcium carbonate coatings
The effect of calcium carbonate coatings on the reduction of aqueous chromate on the magnetite(1 1 1) surface has been investigated using a combination of synchrotron based X-ray photoemission spectroscopy (PES) and X-ray absorption near edge structure (XANES) spectroscopy, along with laboratory-based powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). CaCO3 coatings (dominantly calcite with minor quantities of aragonite and vaterite) of thicknesses ranging from 10 Å to 20 m were grown on magnetite(1 1 1) surfaces by exposure to supersaturated aqueous solutions followed by evaporation of the solution—a process that mimics pore-water evaporation in vadose zones leading to the formation of caliche and calcium carbonate coatings on mineral grains. Coating thicknesses were determined from attenuation of the Fe 2p photoemission signal by the carbonate coating. For coatings less than 15 Å thick, Cr 2p photoemission and Cr LII, LIII-edge XANES spectra show that chromate is reduced by the underlying magnetite surface; however, as the minimum coating thickness increases beyond 15 Å, the magnetite surface becomes passivated and further chromate reduction ceases. Our findings suggest that carbonate coatings on natural magnetite grains can significantly reduce or eliminate their ability to reduce Cr(VI), which is a toxic and highly mobile environmental contaminant. 相似文献