全文获取类型
收费全文 | 918篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
化学 | 515篇 |
晶体学 | 2篇 |
力学 | 19篇 |
数学 | 116篇 |
物理学 | 297篇 |
出版年
2023年 | 10篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 11篇 |
2018年 | 29篇 |
2017年 | 21篇 |
2016年 | 32篇 |
2015年 | 31篇 |
2014年 | 34篇 |
2013年 | 59篇 |
2012年 | 58篇 |
2011年 | 60篇 |
2010年 | 36篇 |
2009年 | 40篇 |
2008年 | 46篇 |
2007年 | 40篇 |
2006年 | 32篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 14篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1969年 | 4篇 |
排序方式: 共有949条查询结果,搜索用时 31 毫秒
81.
Luk’yanenko N. G. Kirichenko T. I. Lyapunov A. Yu. Kulygina E. Yu. Mazepa A. V. 《Russian Journal of Organic Chemistry》2009,45(2):304-311
New crownophane family was synthesized containing fragments of 2,7-dioxyfluorenone and hydroquinone connected with residues of tri- and tetraethylene glycols. The formation of inclusion complexes of these ligands with paraquat was established by means of mass spectrometry (fast-atom bombardment), 1H NMR and electronic spectroscopy. The crownophane with a larger ring formed the more stable complex.
相似文献82.
V. I. Albul V. B. Bychkov S. S. Vasil’ev K. E. Gusev V. S. Demidov E. V. Demidova N. K. Krasnov A. F. Kurchanov V. E. Luk’yashin A. Yu. Sokolov 《Acoustical Physics》2005,51(1):33-37
In an experiment with a beam of protons accelerated up to an energy of 200 MeV, the space-time structure of the hydroacoustic field generated by protons stopping in the water medium was observed. The contributions of three components were separated: a cylindrical wave diverging from the middle part of the acoustic antenna and the signals from the ends of the antenna, namely, from the region of the maximal energy density release by protons (the Bragg peak) and from the other end corresponding to the beam entrance into water. 相似文献
83.
N. N. Gorobei A. S. Luk’yanenko A. E. Chmel 《Journal of Experimental and Theoretical Physics》2005,101(3):468-471
A time-ordered sequence of topographic images of a stressed amorphous Fe70Cr15B15 ribbon is presented. It is shown that the surface of this material (unlike polycrystalline metal foil) has a fractal structure due to the nonequilibrium conditions of its formation. As a tensile stress of about 500 MPa is applied to the surface, the fractal dimension of the surface increases from 1.21±0.02 to 1.34±0.03, then drops to 1.12±0.03, and finally increases to 1.22±0.02. In about 1.5 hours, a complex surface morphology characterized by a roughness amplitude of several tens of nanometers evolves into a regular pattern of shear bands with amplitude of about 300 nm. Self-affine changes in surface morphology are explained by competition between several processes, including crack propagation, surface smoothing, and self-diffusion. 相似文献
84.
The strain-induced roughening revealed by scanning tunneling microscopy on the surface of elastically strained Ge(111) crystals and Fe70Cr15B15 amorphous alloy foils is discussed. It is demonstrated that the strained-induced roughening can be considered a channel for a decrease in the elastic energy of the strained surface. The diffusion mechanism of relief formation on a strained Ge(111) surface is proposed and justified. 相似文献
85.
V. M. Derkacheva S. A. Mikhalenko L. I. Solov’eva V. I. Alekseeva L. E. Marinina L. P. Savina A. V. Butenin E. A. Luk’yanets 《Russian Journal of General Chemistry》2007,77(6):1117-1125
A series of conjugates of sulfo- and carboxy-substituted phthalocyanines with rhodamines were prepared, and their electronic absorption and luminescence spectra were studied. An intramolecular transfer of the excitation energy from the rhodamine moiety (donor) to the phthalocyanine moiety (acceptor) was revealed. 相似文献
86.
L. Lukšan 《Journal of Optimization Theory and Applications》1994,83(1):27-47
Variable metric methods from the Broyden family are well known and commonly used for unconstrained minimization. These methods have good theoretical and practical convergence properties which depend on a selection of free parameters. We demonstrate, using extensive computational experiments, the influence of both the Biggs stabilization parameter and Oren scaling parameter on 12 individual variable metric updates, two of which are new. This paper focuses on a class of variable metric updates belonging to the so-called preconvex part of the Broyden family. These methods outperform the more familiar BFGS method. We also experimentally demonstrate the efficiency of the controlled scaling strategy for problems of sufficient size and sparsity. 相似文献
87.
This paper is devoted to globally convergent methods for solving large sparse systems of nonlinear equations with an inexact approximation of the Jacobian matrix. These methods include difference versions of the Newton method and various quasi-Newton methods. We propose a class of trust region methods together with a proof of their global convergence and describe an implementable globally convergent algorithm which can be used as a realization of these methods. Considerable attention is concentrated on the application of conjugate gradient-type iterative methods to the solution of linear subproblems. We prove that both the GMRES and the smoothed COS well-preconditioned methods can be used for the construction of globally convergent trust region methods. The efficiency of our algorithm is demonstrated computationally by using a large collection of sparse test problems. 相似文献
88.
Biology‐Oriented Synthesis of a Withanolide‐Inspired Compound Collection Reveals Novel Modulators of Hedgehog Signaling 下载免费PDF全文
Dr. Jakub Švenda Dipl.‐Biochem. Michael Sheremet M. Sc. Lea Kremer Lukáš Maier Dr. Jonathan O. Bauer Prof. Dr. Carsten Strohmann Dr. Slava Ziegler Dr. Kamal Kumar Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(19):5596-5602
Biology‐oriented synthesis employs the structural information encoded in complex natural products to guide the synthesis of compound collections enriched in bioactivity. The trans‐hydrindane dehydro‐δ‐lactone motif defines the characteristic scaffold of the steroid‐like withanolides, a plant‐derived natural product class with a diverse pattern of bioactivity. A withanolide‐inspired compound collection was synthesized by making use of three key intermediates that contain this characteristic framework derivatized with different reactive functional groups. Biological evaluation of the compound collection in cell‐based assays that monitored biological signal‐transduction processes revealed a novel class of Hedgehog signaling inhibitors that target the protein Smoothened. 相似文献
89.
High‐throughput workflow for identification of phosphorylated peptides by LC‐MALDI‐TOF/TOF‐MS coupled to in situ enrichment on MALDI plates functionalized by ion landing 下载免费PDF全文
Lukáš Krásný Petr Pompach Marcela Strnadová Radovan Hynek Karel Vališ Vladimír Havlíček Petr Novák Michael Volný 《Journal of mass spectrometry : JMS》2015,50(6):802-811
We report an MS‐based workflow for identification of phosphorylated peptides from trypsinized protein mixtures and cell lysates that is suitable for high‐throughput sample analysis. The workflow is based on an in situ enrichment on matrix‐assisted laser desorption/ionization (MALDI) plates that were functionalized by TiO2 using automated ion landing apparatus that can operate unsupervised. The MALDI plate can be functionalized by TiO2 into any array of predefined geometry (here, 96 positions for samples and 24 for mass calibration standards) made compatible with a standard MALDI spotter and coupled with high‐performance liquid chromatography. The in situ MALDI plate enrichment was compared with a standard precolumn‐based separation and achieved comparable or better results than the standard method. The performance of this new workflow was demonstrated on a model mixture of proteins as well as on Jurkat cells lysates. The method showed improved signal‐to‐noise ratio in a single MS spectrum, which resulted in better identification by MS/MS and a subsequent database search. Using the workflow, we also found specific phosphorylations in Jurkat cells that were nonspecifically activated by phorbol 12‐myristate 13‐acetate. These phosphorylations concerned the mitogen‐activated protein kinase/extracellular signal‐regulated kinase signaling pathway and its targets and were in agreement with the current knowledge of this signaling cascade. Control sample of non‐activated cells was devoid of these phosphorylations. Overall, the presented analytical workflow is able to detect dynamic phosphorylation events in minimally processed mammalian cells while using only a short high‐performance liquid chromatography gradient. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
90.
O. A. Luk´yanov G. V. Pokhvisneva T. V. Ternikova G. A. Smirnov 《Russian Chemical Bulletin》2015,64(5):1062-1064
Chlorides and anhydrides of carboxylic (including dicarboxylic) acids react with salts of 1-methoxy-3-methyl-1-triazene 2-oxides to give the corresponding 3-acyl-1-methoxy-3-methyl-1-triazene 2-oxides. 相似文献