全文获取类型
收费全文 | 2463篇 |
免费 | 75篇 |
国内免费 | 11篇 |
专业分类
化学 | 1466篇 |
晶体学 | 59篇 |
力学 | 42篇 |
数学 | 249篇 |
物理学 | 733篇 |
出版年
2022年 | 14篇 |
2021年 | 21篇 |
2020年 | 26篇 |
2019年 | 35篇 |
2017年 | 18篇 |
2016年 | 53篇 |
2015年 | 60篇 |
2014年 | 47篇 |
2013年 | 81篇 |
2012年 | 109篇 |
2011年 | 117篇 |
2010年 | 62篇 |
2009年 | 85篇 |
2008年 | 107篇 |
2007年 | 107篇 |
2006年 | 101篇 |
2005年 | 98篇 |
2004年 | 100篇 |
2003年 | 64篇 |
2002年 | 88篇 |
2001年 | 44篇 |
2000年 | 49篇 |
1999年 | 41篇 |
1998年 | 35篇 |
1997年 | 38篇 |
1996年 | 41篇 |
1995年 | 34篇 |
1994年 | 43篇 |
1993年 | 35篇 |
1992年 | 26篇 |
1991年 | 34篇 |
1990年 | 38篇 |
1989年 | 18篇 |
1988年 | 41篇 |
1987年 | 45篇 |
1986年 | 17篇 |
1985年 | 43篇 |
1984年 | 30篇 |
1983年 | 31篇 |
1982年 | 24篇 |
1981年 | 41篇 |
1980年 | 31篇 |
1979年 | 29篇 |
1978年 | 26篇 |
1977年 | 15篇 |
1976年 | 21篇 |
1975年 | 24篇 |
1974年 | 18篇 |
1973年 | 19篇 |
1972年 | 11篇 |
排序方式: 共有2549条查询结果,搜索用时 31 毫秒
1.
Alloys of the systems Fe–Al (mixable over the whole concentration range) and Fe–Mg (insoluble with each other) were produced by implantation of Fe ions into Al and Mg, respectively. The implantation energy was 200 keV and the ion doses ranged from 1 × 1014 to 9 × 1017cm-2The obtained implantation profiles were determined by Auger electron spectroscopy depth profiling. Maximum iron concentrations reached were up to 60 at.% for implantation into Al and 94 at.% for implantation into Mg. Phase analysis of the implanted layers was performed by conversion electron Mössbauer spectroscopy and X‐ray diffraction. For implantation into Mg, two different kinds of Mössbauer spectra were obtained: at low doses paramagnetic doublets indicating at least two different iron sites and at high doses a dominant ferromagnetic six‐line‐pattern with a small paramagnetic fraction. The X‐ray diffraction pattern concluded that in the latter case a dilated αiron lattice is formed. For implantation into Al, the Mössbauer spectra were doublet structures very similar to those obtained at amorphous Fe–Al alloys produced by rapid quenching methods. They also indicated at least two different main iron environments. For the highest implanted sample a ferromagnetic six‐line‐pattern with magnetic field values close to those of Fe3Al appeared. 相似文献
2.
3.
For a graph G and a positive integer m, G(m) is the graph obtained from G by replacing every vertex by an independent set of size m and every edge by m2 edges joining all possible new pairs of ends. If G triangulates a surface, then it is easy to see from Euler's formula that G(m) can, in principle, triangulate a surface. For m prime and at least 7, it has previously been shown that in fact G(m) does triangulate a surface, and in fact does so as a “covering with folds” of the original triangulation. For m = 5, this would be a consequence of Tutte's 5‐Flow Conjecture. In this work, we investigate the case m = 2 and describe simple classes of triangulations G for which G(2) does have a triangulation that covers G “with folds,” as well as providing a simple infinite class of triangulations G of the sphere for which G(2) does not triangulate any surface. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 79–92, 2003 相似文献
4.
5.
YoungJu Choie Olav K. Richter 《Proceedings of the American Mathematical Society》2007,135(8):2309-2315
We determine a class of functions spanned by theta series of higher degree. We give two applications: A simple proof of the inversion formula of such theta series and a classification of skew-holomorphic Jacobi forms.
6.
Kristin Fischer Silvio Prause Stefan Spange Frank Cichos Christian Von Borczyskowski 《Journal of Polymer Science.Polymer Physics》2003,41(11):1210-1218
Solvent‐dependent ultraviolet–visible (UV–vis) absorption and Stokes shifts including strong hydrogen‐bond‐donating (HBD) solvents such as 2,2,2‐trifluoroethanol and 1,1,1,3,3,3‐hexafluoro‐2‐propanol of two coumarine dyes (Co 151 and Co 153) were analyzed with multiple‐square analyses of linear solvation energy relationships and the Kamlet–Taft solvent parameter set to α (HBD capacity), β (hydrogen‐bond‐accepting capacity), and π* (dipolarity/polarizability). The UV–vis absorption and emission spectra of Co 151 and Co 153 were measured when adsorbed on various polysaccharides such as different cellulose batches, carboxymethylcelluloses with different degrees of substitution, and chitine. As a result of this evaluation, Co 153 is recommended as an alternative UV–vis probe for evaluating the dipolarity/polarizability of cellulose and cellulose derivates. Multiple adsorption of Co 153 on Linters cellulose took place indicating a wide‐surface polarity distribution, which makes the determination of a rigid polarity parameter questionable. Thus, fluorescence measurements of adsorbed Co 153 are suitable to detect inhomogenities on a surface but not for the determination of empirical polarity parameters. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1210–1218, 2003 相似文献
7.
Stefan Richter William T. Ross Carl Sundberg 《Proceedings of the American Mathematical Society》2004,132(8):2361-2365
In this paper, we refine a result of Nagel, Rudin, and Shapiro (1982) concerning the zeros of holomorphic functions on the unit disk with finite Dirichlet integral.
8.
Christian Richter 《Elemente der Mathematik》1998,53(4):149-158
9.
10.
M. Brunken L. Casper H. Genz C. Hessler S. Khodyachykh A. Richter 《Optics & Laser Technology》2003,35(5):349-353
A compact autocorrelator suitable for the measurement of the optical pulse length of the infrared free electron laser (IR-FEL) at the S-DALINAC is described. It allows to investigate the energy transfer process from the electrons into the laser light within the undulator of the FEL. The autocorrelator utilizes the second harmonic generation (SHG) and it provides the possibility of a background-free measurement at wavelengths between 4 and 10 μm. Simulations for three different crystals used for SHG show that the largest efficiency for SHG and the best temporal resolution is achieved with a ZnGeP2 crystal at a length of 2 mm. A test experiment at the free electron laser for infrared experiments confirmed the expected high efficiency of about 7.5% of SHG for the ZnGeP2 crystal as well as the easy handling and fast adjustment of the system. 相似文献