全文获取类型
收费全文 | 4146篇 |
免费 | 171篇 |
国内免费 | 12篇 |
专业分类
化学 | 2792篇 |
晶体学 | 42篇 |
力学 | 73篇 |
数学 | 435篇 |
物理学 | 987篇 |
出版年
2023年 | 43篇 |
2022年 | 95篇 |
2021年 | 123篇 |
2020年 | 117篇 |
2019年 | 134篇 |
2018年 | 98篇 |
2017年 | 109篇 |
2016年 | 184篇 |
2015年 | 139篇 |
2014年 | 152篇 |
2013年 | 257篇 |
2012年 | 271篇 |
2011年 | 339篇 |
2010年 | 208篇 |
2009年 | 202篇 |
2008年 | 297篇 |
2007年 | 259篇 |
2006年 | 220篇 |
2005年 | 197篇 |
2004年 | 173篇 |
2003年 | 117篇 |
2002年 | 91篇 |
2001年 | 63篇 |
2000年 | 67篇 |
1999年 | 42篇 |
1998年 | 25篇 |
1997年 | 28篇 |
1996年 | 29篇 |
1995年 | 28篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 31篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1972年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有4329条查询结果,搜索用时 31 毫秒
1.
2.
3.
Application of TiO2-nanotubes/PbO2 as an anode for the electrochemical elimination of Acid Red 1 dye
Santos José Eudes L. de Moura Dayanne Chianca da Silva Djalma Ribeiro Panizza Marco Martínez-Huitle Carlos A. 《Journal of Solid State Electrochemistry》2019,23(2):351-360
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an... 相似文献
4.
Tatiana Monaretto Andre Souza Tiago Bueno Moraes Victor Bertucci-Neto Corinne Rondeau-Mouro Luiz Alberto Colnago 《Magnetic resonance in chemistry : MRC》2019,57(9):616-625
The traditional way to enhance signal-to-noise ratio (SNR) of nuclear magnetic resonance (NMR) signals is to increase the number of scans. However, this procedure increases the measuring time that can be prohibitive for some applications. Therefore, we have tested the use of several post-acquisition digital filters to enhance SNR up to one order of magnitude in time domain NMR (TD-NMR) relaxation measurements. The procedures were studied using continuous wave free precession (CWFP-T1) signals, acquired with very low flip angles that contain six times more noise than the Carr–Purcell–Meiboom–Gill (CPMG) signal of the same sample and experimental time. Linear (LI) and logarithmic (LO) data compression, low-pass infinity impulse response (LP), Savitzky–Golay (SG), and wavelet transform (WA) post-acquisition filters enhanced the SNR of the CWFP-T1 signals by at least six times. The best filters were LO, SG, and WA that have high enhancement in SNR without significant distortions in the ILT relaxation distribution data. Therefore, it was demonstrated that these post-acquisition digital filters could be a useful way to denoise CWFP-T1, as well as CPMG noisy signals, and consequently reducing the experimental time. It was also demonstrated that filtered CWFP-T1 method has the potential to be a rapid and nondestructive method to measure fat content in beef and certainly in other meat samples. 相似文献
5.
Alcindo A. Dos Santos Renan S. Ferrarini Jefferson L. Princival João V. Comasseto 《Tetrahedron letters》2006,47(50):8933-8935
A masked lithium homoenolate, generated by tellurium/lithium exchange, was reacted with epoxides. The lithium compound was also converted into other organometallics such as Grignard, and cuprates and the reactivity of those organometallics with epoxides was evaluated. The same building block was employed in the synthesis of (+/−)-frontalin. 相似文献
6.
J.-C. Thomas L. Achouri J. Äystö R. Béraud B. Blank G. Canchel S. Czajkowski P. Dendooven A. Ensallem J. Giovinazzo N. Guillet J. Honkanen A. Jokinen A. Laird M. Lewitowicz C. Longour F. de Oliveira Santos K. Peräjärvi M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):419-435
7.
C. M. Silva R. S. Amaral A. Amaral J. A. Santos Júnior D. C. Santos L. E. Lima S. V. Silveira 《Journal of Radioanalytical and Nuclear Chemistry》2006,270(1):237-241
Summary Studies performed by the Brazilian Nuclear Corporation (NUCLEBRAS), in collaboration with the Geological Survey Company of
Brazil (CPRM), identified high levels of natural uranium in the districts of Pedra and Venturosa, in the rural region of the
state of Pernambuco (PE) - Brazil, where the maximum value found in rocks was 22,000 mg. 相似文献
8.
Tereza C. R. dos Santos Ricardo Q. Aucélio Reinaldo C. Campos 《Mikrochimica acta》2003,142(1-2):63-66
A simple and direct spectrofluorimetric method has been developed for the determination of aluminum using alizarin red PS
(1,2,4-trihydroxy 9,10-anthraquinone-3-sulfonic acid). The method is based on the strong fluorescence (480/564 nm) of Al3+ and alizarin red. Experimental parameters such as pH, concentration of the ligand, ionic strength of the solution, reaction
time and temperature were optimized in order to maximize the analytical signal. Interferences of several ions (anions and
cations) were studied and evaluated. The linear range of the method extends from 3 to 100 μg L−1. Limit of detection (3sb) was 0.9 μg L−1. The method was tested with a silicate certified reference material. Interferences were eliminated by a liquid extraction
with cupferron.
Author for correspondence. E-mail: aucelior@rdc.puc-rio.br
Received September 10, 2002; accepted January 15, 2003
Published online May 5, 2003 相似文献
9.
M. A. Diniz-Ehrhardt M. A. Gomes-Ruggiero J. M. Martínez S. A. Santos 《Journal of Optimization Theory and Applications》2004,123(3):497-517
The spectral projected gradient method SPG is an algorithm for large-scale bound-constrained optimization introduced recently by Birgin, Martínez, and Raydan. It is based on the Raydan unconstrained generalization of the Barzilai-Borwein method for quadratics. The SPG algorithm turned out to be surprisingly effective for solving many large-scale minimization problems with box constraints. Therefore, it is natural to test its perfomance for solving the sub-problems that appear in nonlinear programming methods based on augmented Lagrangians. In this work, augmented Lagrangian methods which use SPG as the underlying convex-constraint solver are introduced (ALSPG) and the methods are tested in two sets of problems. First, a meaningful subset of large-scale nonlinearly constrained problems of the CUTE collection is solved and compared with the perfomance of LANCELOT. Second, a family of location problems in the minimax formulation is solved against the package FFSQP. 相似文献
10.