全文获取类型
收费全文 | 2143篇 |
免费 | 54篇 |
国内免费 | 27篇 |
专业分类
化学 | 1191篇 |
晶体学 | 7篇 |
力学 | 38篇 |
数学 | 442篇 |
物理学 | 546篇 |
出版年
2023年 | 8篇 |
2022年 | 44篇 |
2021年 | 59篇 |
2020年 | 33篇 |
2019年 | 43篇 |
2018年 | 56篇 |
2017年 | 45篇 |
2016年 | 67篇 |
2015年 | 58篇 |
2014年 | 70篇 |
2013年 | 98篇 |
2012年 | 148篇 |
2011年 | 140篇 |
2010年 | 103篇 |
2009年 | 98篇 |
2008年 | 154篇 |
2007年 | 145篇 |
2006年 | 125篇 |
2005年 | 125篇 |
2004年 | 128篇 |
2003年 | 69篇 |
2002年 | 74篇 |
2001年 | 46篇 |
2000年 | 26篇 |
1999年 | 30篇 |
1998年 | 38篇 |
1997年 | 25篇 |
1996年 | 18篇 |
1995年 | 24篇 |
1994年 | 20篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有2224条查询结果,搜索用时 15 毫秒
11.
We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design. 相似文献
12.
Yuri L. Sachkov 《Transactions of the American Mathematical Society》2004,356(2):457-494
Flat sub-Riemannian structures are local approximations -- nilpotentizations -- of sub-Riemannian structures at regular points. Lie algebras of symmetries of flat maximal growth distributions and sub-Riemannian structures of rank two are computed in dimensions 3, 4, and 5.
13.
Letters in Mathematical Physics - 相似文献
14.
This Review discusses the synthesis and characterization by our Group of new antibiotics belonging to the class of penicillins, cephalosporins and rifamycins with ferrocenyl and 1, 1′-ferrocenilene residues in the molecule. As reactants for 6-aminopenicillanic acid (6-APA) and 7-aminocephalosporanic acid (7-ACA) the following were used: 1, 1-bis(chlorocarbonyl)ferrocene, ferrocenyl sulfochloride, 1, 1′-ferrocenylenedisulfochloride and thioglycolic acids S-modified with ferrocene. In the synthesis of rifamycins, the hydrazides of the thioglycolic acids, S-modified with ferrocene, were employed as nucleophilic agents. The synthesized intermediates were characterized by elemental analysis, TLC, IR, UV and 1H NMR spectra. The characterization of new antibiotics was made by TLC, IR and UV spectral analysis. Biological activity was tested on Gram-negative and Gram-positive bacteria. Good activity is reported towards Gram-positive bacteria in the case of derivatives containing residues of thioglycolic acid S-modified with ferrocene, the antibacterial activity being similar to that of amoxicillin, carbenicillin and cephalothin. All compounds are inactive towards Gram-negative bacteria. 相似文献
15.
Yuri Borovskikh 《Acta Appl Math》1994,35(3):213-298
U-statistics in Banach spaces are considered and thoroughly investigated. The martingale structure, estimates of moments, the law of large numbers, the central limit theorem, the invariance principle, estimates of the rate of convergence, and large deviations are established 相似文献
16.
17.
Yuri L. Mikhlin Alexander S. Romanchenko Alexander A. Shagaev 《Applied Surface Science》2006,252(16):5645-5658
Natural n-type PbS single crystals have been studied using AFM, STM and STS after long-term oxidation in air at ambient temperatures and extensive etching in aqueous acid solutions, in contrast to previous work devoted to initial corrosion of fresh surfaces. The exposure of PbS to atmosphere at high relative humidity for several days yields widespread loose oxidation products; the process is much slower at low humidity. Surface morphologies diverge after the treatment in 1 M perchloric and hydrochloric acid solutions at room temperature and become widely different at elevated temperatures, displaying commonly etch pits up to several micrometers in size and depth along with rather uniformly distributed 20-100 nm protrusions of PbS phase. The changes both in topography and semiconducting properties of PbS found by tunneling spectroscopy have been explained in terms of the non-uniform distribution of donor- and acceptor-type defects D+/D− in the metal depleted surface layer, which are generated by chemical reactions and, in turn, determine the rates of the PbS corrosion. In particular, the D− centers exhibit a self-catalyzing effect on the non-oxidative local dissolution of PbS in HCl media, resulting in the deep etch pits. 相似文献
18.
Yuri Bilu 《Monatshefte für Mathematik》2002,137(1):1-3
We correct an inaccuracy in the papers of Le, Mignotte, and Bugeaud on the generalized Ramanujan-Nagell equation.
Received June 23, 2001 相似文献
19.
20.
Yuri Bozhkov Antonio Carlos Gilli Martins 《Journal of Mathematical Analysis and Applications》2004,294(1):334-344
It is shown that a Lie point symmetry of the Lane-Emden system is a Noether symmetry if and only if its parameters belong to the critical hyperbola. 相似文献