全文获取类型
收费全文 | 1045篇 |
免费 | 27篇 |
国内免费 | 4篇 |
专业分类
化学 | 559篇 |
晶体学 | 3篇 |
力学 | 40篇 |
数学 | 313篇 |
物理学 | 161篇 |
出版年
2023年 | 9篇 |
2022年 | 4篇 |
2021年 | 26篇 |
2020年 | 40篇 |
2019年 | 23篇 |
2018年 | 26篇 |
2017年 | 19篇 |
2016年 | 40篇 |
2015年 | 29篇 |
2014年 | 36篇 |
2013年 | 60篇 |
2012年 | 78篇 |
2011年 | 95篇 |
2010年 | 69篇 |
2009年 | 51篇 |
2008年 | 54篇 |
2007年 | 62篇 |
2006年 | 57篇 |
2005年 | 57篇 |
2004年 | 50篇 |
2003年 | 24篇 |
2002年 | 19篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1968年 | 1篇 |
1944年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有1076条查询结果,搜索用时 33 毫秒
91.
Ioannis N. Lykakis 《Tetrahedron letters》2004,45(41):7645-7649
Decatungstate photocatalyzes the oxidation of aryl alkanes to the corresponding tertiary hydroperoxides and alcohols, in the presence of molecular oxygen. The addition of triethylsilane to the reaction mixture substantially increases the proportion of hydroperoxide formed. 相似文献
92.
93.
The issue is that of following the path of a Brownian particle by a process of bounded total variation and subject to a reflecting barrier at the origin, in such a way as to minimize expected total cost over a finite horizon. We establish the existence of optimal processes and the dynamic programming equations for this question, and show (by purely probabilistic arguments) its relation to an appropriatefamily of optimal stopping problems with absorption at the origin.Work carried out during a visit by the second author at the University Pierre et Marie Curie (Paris VI), and at INRIA (Institut National de Recherche en Informatique et en Automatique). The hospitality of these institutions is gratefully acknowledged.Research supported in part by the U.S. Air Force Office of Scientific Research, under grant AFOSR-86-0203. 相似文献
94.
Ioannis Emmanouil 《Inventiones Mathematicae》1998,132(2):307-330
In this paper, we use the Connes-Karoubi character liftings of the Hattori-Stallings rank in order to obtain examples of
groups satisfying Bass' conjecture. We consider the nilpotence of the periodicity operator in cyclic homology and verify the
conjecture for a certain class of groups which contains properly the ones studied by Eckmann. We also give an application
of this method to the idempotent conjecture.
Oblatum 21-III-1997 & 12-VI-1997 相似文献
95.
Ioannis E. Antoniou Baydyanath Misra 《International Journal of Theoretical Physics》1992,31(1):119-136
We construct a self-adjoint time operator for massless relativistic systems in terms of the generators of the Poincaré group. The Lie algebra generated by the time operator and the generators of the Poincaré group turns out to be an infinitedimensional extension of the Poincaré algebra. The internal time operator generates two new entities, namely the velocity operator and the internal position operator. The transformation properties of the internal time and position operator under Lorentz boosts are different from what one would expect from relativity theory. This difference reflects the fact that the time concept associated with the internal time operator is radically different from the time coordinate of Minkowski space, due to the nonlocality of the time operator. The spectral projections of the time operator allow us to construct incoming subspaces for the wave equation without invoking Huygens' principle, as in two and one spatial dimensions where Huygens' principle does not hold. 相似文献
96.
Ioannis K. Argyros 《Journal of Applied Mathematics and Computing》1998,5(2):465-474
In this study we are concerned with the problem of approximating a locally unique solution of an equation on a Banach space. A semilocal convergence theorem is given for the Super-Halley method in Banach spaces. Earlier results have shown that the order of convergence is four for a certain class of operators [4], [5], [8]. These results were not given in affine invariant form, and made use of a real quadratic majorizing polynomial. Here, we provide our results in affine invariant form showing that the order of convergence is at least four. In cases that it is exactly four the rate of convergence is improved. We achieve these results by using a cubic majorizing polynomial. Some numerical examples are given to show that our error bounds are better than earlier ones. 相似文献
97.
A new microtensile tester for the study of MEMS materials with the aid of atomic force microscopy 总被引:4,自引:0,他引:4
An apparatus has been designed and implemented to measure the elastic tensile properties (Young's modulus and tensile strength)
of surface micromachined polysilicon specimens. The tensile specimens are “dog-bone” shaped ending in a large “paddle” for
convenient electrostatic or, in the improved apparatus, ultraviolet (UV) light curable adhesive gripping deposited with electrostatically
controlled manipulation. The typical test section of the specimens is 400 μm long with 2 μm×50 μm cross section. The new device
supports a nanomechanics method developed in our laboratory to acquire surface topologies of deforming specimens by means
of Atomic Force Microscopy (AFM) to determine (fields of) strains via Digital Image Correlation (DIC). With this tool, high
strength or non-linearly behaving materials can be tested under different environmental conditions by measuring the strains
directly on the surface of the film with nanometer resolution. 相似文献
98.
Ioannis P. Gerothanassis 《Magnetic resonance in chemistry : MRC》1983,21(12):719-722
The relationship between the signal-to-noise ration and T2 and, hence, the line width of a resonance for quadrupolar nuclei, with particular reference to 17O at natural abundance, is discussed. Emphasis is placed on the importance of choosing appropriate FID acquisition times related to the T2 values or resonance widths of the quadrupolar nuclei. When this is feasible (i.e. when the principal resonances in a spectrum have similar widths) the signal-to-noise ratio attainable against a flat base line in a given time of spectral accumulation is independent of resonance line width. Although resolution improvements can be made by using appropriate solvents or elevated sample temperatures, the sensitivity has been to be strongly dependent on the acquisition parameters used. 相似文献
99.
Ioannis Parissis 《Journal of Geometric Analysis》2010,20(3):771-785
Let ℳ denote the maximal function along the polynomial curve (γ
1
t,…,γ
d
t
d
):
$\mathcal{M}(f)(x)=\sup_{r>0}\frac{1}{2r}\int_{|t|\leq r}|f(x_1-\gamma_1t,\ldots,x_d-\gamma_dt^d)|\,dt.$\mathcal{M}(f)(x)=\sup_{r>0}\frac{1}{2r}\int_{|t|\leq r}|f(x_1-\gamma_1t,\ldots,x_d-\gamma_dt^d)|\,dt. 相似文献
100.
We provide a semilocal convergence analysis for Broyden’s method for approximating locally unique solutions of nonlinear operator equations. Using the majorant principle we show that under the same or weaker hypotheses, in combination with our new idea of recurrent functions, we can find weaker sufficient conditions for the convergence of Broyden’s method as well as finer error bounds on the distances involved, and a more precise information on the location of the solution than before (Broyden, Math. Comput. 19:577–593, 1965; Chen, Ann. Inst. Stat. Math. 42:387–401, 1990; Dennis, Nonlinear Functional Analysis and Applications, pp. 425–472, Academic Press, San Diego, 1971; Li and Fukushima, Ann. Oper. Res. 103:71–97, 2001). Numerical examples are also provided involving polynomial, integral, and differential equations. 相似文献
|