全文获取类型
收费全文 | 7239篇 |
免费 | 277篇 |
国内免费 | 41篇 |
专业分类
化学 | 4678篇 |
晶体学 | 60篇 |
力学 | 228篇 |
数学 | 1027篇 |
物理学 | 1564篇 |
出版年
2023年 | 67篇 |
2022年 | 138篇 |
2021年 | 195篇 |
2020年 | 183篇 |
2019年 | 200篇 |
2018年 | 171篇 |
2017年 | 160篇 |
2016年 | 289篇 |
2015年 | 235篇 |
2014年 | 258篇 |
2013年 | 460篇 |
2012年 | 518篇 |
2011年 | 650篇 |
2010年 | 378篇 |
2009年 | 386篇 |
2008年 | 532篇 |
2007年 | 443篇 |
2006年 | 406篇 |
2005年 | 349篇 |
2004年 | 295篇 |
2003年 | 230篇 |
2002年 | 178篇 |
2001年 | 105篇 |
2000年 | 95篇 |
1999年 | 64篇 |
1998年 | 48篇 |
1997年 | 50篇 |
1996年 | 59篇 |
1995年 | 42篇 |
1994年 | 31篇 |
1993年 | 39篇 |
1992年 | 42篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1942年 | 6篇 |
排序方式: 共有7557条查询结果,搜索用时 15 毫秒
11.
Dr. Felipe L. Coelho Eduarda S. Gil Dr. Paulo F. B. Gonçalves Dr. Leandra F. Campo Dr. Paulo H. Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8157-8162
In this work, a series of 2-chalcogenylindoles was synthesized by an efficient methodology, starting from chalcogenoalkynes, including a previously unreported tellurium indole derivative. For the first time, these 2-substituted chalcogenylindoles were obtained in the absence of metal catalyst or base, under thermal conditions only. In addition, the results described herein represent a methodology with inverse regioselectivity for the chalcogen functionalization of indoles. 相似文献
12.
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
13.
14.
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
15.
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
16.
Paulo D. Cordaro 《Advances in Mathematics》2004,184(1):89-118
Taking as a start point the recent article of Meziani [7], we present several results concerning the normalization of a class of complex vector fields in the plane which degenerate along a real curve. We mainly deal with operators with finite regularity and analyze both the local situation as well as the case of normalization near a circle. Some related questions (e.g., on semi-global solvability and on the normalization of a class of generalized Mizohata operators) are also discussed. 相似文献
17.
18.
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
19.
Alexandre Munnier 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2003,9(2):977-1000
This article deals with stability and small linear
oscillations of liquid bridges between fixed solid surfaces
(parallel plates, spheres, ...) under zero gravity. A general
investigation method for any kind of axisymmetric liquid bridge is
exposed but the author focus his work on the spherical liquid
bridge cases. In particular, he exposes a full theoretical study
of spherical liquid bridges between two spheres, plates and
cones. 相似文献
20.
Alexandre Stojanovic 《Mathematical Physics, Analysis and Geometry》2004,7(4):347-349
The errata concern mainly the last computations for the universality of the local statistics of eigenvalues at the edge of the spectrum in parts (iii) of Theorems 2.3 and 2.4. 相似文献