全文获取类型
收费全文 | 2438篇 |
免费 | 281篇 |
国内免费 | 255篇 |
专业分类
化学 | 1824篇 |
晶体学 | 29篇 |
力学 | 95篇 |
综合类 | 39篇 |
数学 | 347篇 |
物理学 | 640篇 |
出版年
2023年 | 16篇 |
2022年 | 35篇 |
2021年 | 57篇 |
2020年 | 73篇 |
2019年 | 93篇 |
2018年 | 63篇 |
2017年 | 65篇 |
2016年 | 104篇 |
2015年 | 95篇 |
2014年 | 119篇 |
2013年 | 174篇 |
2012年 | 154篇 |
2011年 | 154篇 |
2010年 | 110篇 |
2009年 | 129篇 |
2008年 | 139篇 |
2007年 | 121篇 |
2006年 | 112篇 |
2005年 | 114篇 |
2004年 | 130篇 |
2003年 | 122篇 |
2002年 | 154篇 |
2001年 | 135篇 |
2000年 | 84篇 |
1999年 | 67篇 |
1998年 | 23篇 |
1997年 | 19篇 |
1996年 | 20篇 |
1995年 | 25篇 |
1994年 | 24篇 |
1993年 | 17篇 |
1992年 | 25篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 20篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1968年 | 4篇 |
排序方式: 共有2974条查询结果,搜索用时 15 毫秒
31.
A series of 5‐aryl‐1H‐pyrazole derivatives were synthesized via the reaction of 3‐(dimethylamino)‐1‐arylprop‐2‐en‐1‐one with hydrazine in aqueous media without using any catalyst. This method has the advantages of easier work‐up, mild reaction condition, high yields, and an environmentally benign procedure. 相似文献
32.
Rücktitelbild: Cofactor‐Free Light‐Driven Whole‐Cell Cytochrome P450 Catalysis (Angew. Chem. 3/2015)
33.
Monte Carlo simulation of full energy spectrum of electrons emitted from silicon in Auger electron spectroscopy 下载免费PDF全文
N. Cao B. Da Y. Ming S. F. Mao K. Goto Z. J. Ding 《Surface and interface analysis : SIA》2015,47(1):113-119
A Monte Carlo simulation including surface excitation, Auger electron‐ and secondary electron production has been performed to calculate the energy spectrum of electrons emitted from silicon in Auger electron spectroscopy (AES), covering the full energy range from the elastic peak down to the true‐secondary‐electron peak. The work aims to provide a more comprehensive understanding of the experimental AES spectrum by integrating the up‐to‐date knowledge of electron scattering and electronic excitation near the solid surface region. The Monte Carlo simulation model of beam–sample interaction includes the atomic ionization and relaxation for Auger electron production with Casnati's ionization cross section, surface plasmon excitation and bulk plasmon excitation as well as other bulk electronic excitation for inelastic scattering of electrons (including primary electrons, Auger electrons and secondary electrons) through a dielectric functional approach, cascade secondary electron production in electron inelastic scattering events, and electron elastic scattering with use of Mott's cross section. The simulated energy spectrum for Si sample describes very well the experimental AES EN(E) spectrum measured with a cylindrical mirror analyzer for primary energies ranging from 500 eV to 3000 eV. Surface excitation is found to affect strongly the loss peak shape and the intensities of the elastic peak and Auger peak, and weakly the low energy backscattering background, but it has less effect to high energy backscattering background and the Auger electron peak shape. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
34.
Jing Tang Jun Li Peimei Da Yongcheng Wang Prof. Gengfeng Zheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11288-11299
Photoelectrochemical sensing represents a unique means for chemical and biological detection, with foci of optimizing semiconductor composition and electronic structures, surface functionalization layers, and chemical detection methods. Here, we have briefly discussed our recent developments of TiO2 nanowire‐based photoelectrochemical sensing, with particular emphasis on three main detection mechanisms and corresponding examples. We have also demonstrated the use of the photoelectrochemical sensing of real‐time molecular reaction kinetic measurements, as well as direct interfacing of living cells and probing of cellular functions. 相似文献
35.
Da Wang Dr. Christian Richter Andreas Rühling Dr. Patrick Drücker Daniel Siegmund Prof. Dr. Nils Metzler‐Nolte Prof. Dr. Frank Glorius Prof. Dr. Hans‐Joachim Galla 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15123-15126
A series of imidazolium salts bearing two alkyl chains in the backbone of the imidazolium core were synthesized, resembling the structure of lipids. Their antibacterial activity and cytotoxicity were evaluated using Gram‐positive and Gram‐negative bacteria and eukaryotic cell lines including tumor cells. It is shown that the length of alkyl chains in the backbone is vital for the antibiofilm activities of these lipid‐mimicking components. In addition to their biological activity, their surface activity and their membrane interactions are shown by film balance and quartz crystal microbalance (QCM) measurements. The structure–activity relationship indicates that the distinctive chemical structure contributes considerably to the biological activities of this novel class of lipids. 相似文献
36.
Back Cover: Cofactor‐Free Light‐Driven Whole‐Cell Cytochrome P450 Catalysis (Angew. Chem. Int. Ed. 3/2015) 下载免费PDF全文
37.
Monitoring of Endogenous Hydrogen Sulfide in Living Cells Using Surface‐Enhanced Raman Scattering 下载免费PDF全文
Dr. Da‐Wei Li Lu‐Lu Qu Kai Hu Prof. Dr. Yi‐Tao Long Prof. Dr. He Tian 《Angewandte Chemie (International ed. in English)》2015,54(43):12758-12761
Hydrogen sulfide (H2S) has emerged as an important gasotransmitter in diverse physiological processes, although many aspects of its roles remain unclear, partly owing to a lack of robust analytical methods. Herein we report a novel surface‐enhanced Raman scattering (SERS) nanosensor, 4‐acetamidobenzenesulfonyl azide‐functionalized gold nanoparticles (AuNPs/4‐AA), for detecting the endogenous H2S in living cells. The detection is accomplished with SERS spectrum changes of AuNPs/4‐AA resulting from the reaction of H2S with 4‐AA on AuNPs. The SERS nanosensor exhibits high selectivity toward H2S. Furthermore, AuNPs/4‐AA responds to H2S within 1 min with a 0.1 μM level of sensitivity. In particular, our SERS method can be utilized to monitor the endogenous H2S generated in living glioma cells, demonstrating its great promise in studies of pathophysiological pathways involving H2S. 相似文献
38.
The non-linear differential equations of motion, and boundary conditions, for Euler-Bernoulli beams able to experience flexure along two principal directions (and, thus, flexure in any direction in space), torsion and extension are formulated. The beam's material is assumed to be Hookean but its properties may vary along its span. The nonlinearities present in the differential equations include contributions from the curvature expression and from inertia terms. A set of differential equations with polynomial nonlinearities to cubic order, suitable for a perturbation analysis of the motion, is also developed and the validity of the inextensional approximation is assessed. The equations developed here reduce to those for an inextensional beam. In Part II of this paper, a specific example of application is analyzed and the results obtained are compared with those available in the literature where several non-linear terms have been neglected a priori. 相似文献
39.
40.
In this paper an exterior point polynomial time algorithm for convex quadratic programming problems is proposed. We convert a convex quadratic program into an unconstrained convex program problem with a self-concordant objective function. We show that, only with duality, the Path-following method is valid. The computational complexity analysis of the algorithm is given. 相似文献