全文获取类型
收费全文 | 626篇 |
免费 | 11篇 |
国内免费 | 8篇 |
专业分类
化学 | 212篇 |
晶体学 | 2篇 |
力学 | 21篇 |
数学 | 269篇 |
物理学 | 141篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 18篇 |
2017年 | 26篇 |
2016年 | 38篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 44篇 |
2012年 | 52篇 |
2011年 | 49篇 |
2010年 | 30篇 |
2009年 | 30篇 |
2008年 | 40篇 |
2007年 | 24篇 |
2006年 | 37篇 |
2005年 | 28篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 8篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1968年 | 3篇 |
1965年 | 1篇 |
1939年 | 1篇 |
1911年 | 1篇 |
排序方式: 共有645条查询结果,搜索用时 0 毫秒
121.
S. V. Kozhevnikov Yu. N. Khaidukov F. Ott F. Radu 《Journal of Experimental and Theoretical Physics》2018,126(5):592-599
The channeling of neutrons in a three-layer planar waveguide with a neutron-optical potential well is studied. Neutrons incident on a sample surface, which propagate in a middle layer and escape from the waveguide end in the form of a narrow divergent beam, are detected. The decay parameter of a neutron wave inside the waveguide is measured as a function of the potential well depth. Experimental results are compared with a theory. 相似文献
122.
We review various methods in the investigation of magnetic films with neutrons, including those based on the effects of Larmor precession, Zeeman spatial splitting of the beam, neutron spin resonance, and polarized neutron channeling. The underlying principles, examples of the investigated systems, specific features, applications, and perspectives of these methods are discussed. 相似文献
123.
Anca Petran Teodora Radu Alexandrina Nan Diana Olteanu Adriana Filip Simona Clichici Ioana Baldea Maria Suciu Rodica Turcu 《Journal of nanoparticle research》2017,19(1):10
The paper presents the synthesis, characterization, and in vitro cytotoxicity tests of Fe3O4 magnetic nanoclusters coated with ethylenediaminetetraacetic acid disodium salt (EDTA). Electron microscopy analysis (SEM) evidences that magnetite nanoparticles are closely packed into the clusters stabilized with EDTA with well-defined near spherical shapes and sizes in the range 100–200 nm. From XRD measurements, we determined the mean size of the crystallites inside the magnetic cluster about 36 nm. The saturation magnetization determined for the magnetic clusters stabilized with EDTA has high value, about 81.7 emu/g at 300 K. X-ray photoelectron spectroscopy has been used to determine both the elemental and chemical structure of the magnetic cluster surface. In vitro studies have shown that the magnetic clusters at low doses did not induce toxicity on human umbilical vein endothelial cells or lesions of the cell membrane. In contrast, at high doses, the magnetic clusters increased the lipid peroxidation and reduced the leakage of a cytoplasmic enzyme, lactate dehydrogenase (LDH), in parallel with increasing the antioxidant defense. 相似文献
124.
Lucas C. Céleri Rafael M. Gomes Radu Ionicioiu Thomas Jennewein Robert B. Mann Daniel R. Terno 《Foundations of Physics》2014,44(5):576-587
We describe a new class of experiments designed to probe the foundations of quantum mechanics. Using quantum controlling devices, we show how to attain a freedom in temporal ordering of the control and detection of various phenomena. We consider wave–particle duality in the context of quantum-controlled and the entanglement-assisted delayed-choice experiments. Then we discuss a quantum-controlled CHSH experiment and measurement of photon’s transversal position and momentum in a single set-up. 相似文献
125.
Photoluminescence and magnetic circular dichroism of the IrQ(ppy)2-5Cl compound were investigated between 15 and 295 K. These results have been compared with the output files obtained from Density Functional Theory by using the Gaussian 03W software and some additional packages. The experimental results confirm the first triplet state absorption which arises from d to πQ transition. The temperature dependence photoluminescence have shown a small interaction with the polystyrene, used for dispersion of IrQ(ppy)2-5Cl compound. The green and red phosphorescence have the same temperature dependence. The MCD spectra, especially at 15 K, reveals the main transitions involved in the Metal-to-Ligand Charge Transfer processes from the Ir towards the two ligands, phenylpyridine and quinoline, respectively. 相似文献
126.
The aim of this paper is to implement some new techniques, based on conjugate duality in convex optimization, for proving the existence of global error bounds for convex inequality systems. First of all, we deal with systems described via one convex inequality and extend the achieved results, by making use of a celebrated scalarization function, to convex inequality systems expressed by means of a general vector function. We also propose a second approach for guaranteeing the existence of global error bounds of the latter, which meanwhile sharpens the classical result of Robinson. 相似文献
127.
In this paper, by using some of our new results concerning the shift space for an infinite IFS (see A. Mihail and R. Miculescu, The shift space for an infinite iterated function system, Math. Rep. Bucur. 11 (2009), 21?C32), we show that, for an infinite set A, the embedded version of the Lipscomb space L(A) in l p (A), ${p \in [1,\infty)}$ , with the metric induced from l p (A), denoted by ${\omega_p^A}$ , is the attractor of an infinite iterated function system comprising affine transformations of l p (A). In this way we provide a generalization of the positive answer that we gave to an open problem of J.C. Perry (see Lipscomb??s universal space is the attractor of an infinite iterated function system, Proc. Amer. Math. Soc. 124 (1996), 2479?C2489) in one of our previous works (see R. Miculescu and A. Mihail, Lipscomb space ?? A is the attractor of an infinite IFS containing affine transformations of l 2(A), Proc. Amer. Math. Soc. 136 (2008), 587?C592). Moreover, as a byproduct, we provide a generalization of Corollary 15 from Perry??s paper by proving that ${\omega_p^A}$ is a closed subset of l p (A). 相似文献
128.
Iterative methods to solve systems of linear equations Ax = b usually require preconditioners M to speed convergence. But the calculation of many preconditioners can be notoriously sequential. The sparse approximate inverse preconditioner (SPAI) has particular potential for high performance computing [1]. We have ported the SPAI algorithm to graphical processing units (GPUs) within NVIDIA's CUSP library [2] for sparse linear algebra. GPUs perform well on dense linear algebra problems where data resides for long periods on the device. Since the underlying minimization problems are independent, they are mapped to separate thread-blocks, and an optimized QR algorithm implemented using NVIDIA's CUBLAS library is employed on each. Traditionally the challenge has been to determine a sparsity pattern Sp( M ) of the preconditioner dynamically [3], which reduces the condition number of MA to a degree where a preconditioned iterative solver such as GMRES becomes computationally viable. Due to the extremely high performance of the GPU, it is possible to consider initial sparsity patterns much denser than have been previously considered. We therefore consider a fixed sparsity patterns to simplify the GPU implementation. We evaluate the performance of the resulting preconditioner on a standard set of sparse matrices, and compare SPAI to other preconditioners. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
129.
The work presents theoretical and experimental investigations concerning the neuro-fuzzy control of electrohydraulic servos. The control algorithm is built around a neurocontroller designed to optimize a performance index. Whenever the neurocontrol saturates or a system performance parameter decreases, the control scheme switches to a feasible and reliable fuzzy logic control. In accordance with simulation studies developed in previous works of the authors, the neuro-fuzzy controlled system proves often to be better than the corresponding classical PI or LQG systems. We emphasize that the entire control synthesis is thought as a model free approach, thus ensuring reduced design complexity and focusing on increased system robustness. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
130.
The aim of this paper is to develop an efficient algorithm for solving a class of unconstrained nondifferentiable convex optimization problems in finite dimensional spaces. To this end we formulate first its Fenchel dual problem and regularize it in two steps into a differentiable strongly convex one with Lipschitz continuous gradient. The doubly regularized dual problem is then solved via a fast gradient method with the aim of accelerating the resulting convergence scheme. The theoretical results are finally applied to an l 1 regularization problem arising in image processing. 相似文献