全文获取类型
收费全文 | 351662篇 |
免费 | 1197篇 |
国内免费 | 587篇 |
专业分类
化学 | 176329篇 |
晶体学 | 6932篇 |
力学 | 16936篇 |
综合类 | 16篇 |
数学 | 36244篇 |
物理学 | 116989篇 |
出版年
2020年 | 3309篇 |
2019年 | 3919篇 |
2018年 | 4941篇 |
2017年 | 4990篇 |
2016年 | 7012篇 |
2015年 | 3885篇 |
2014年 | 6502篇 |
2013年 | 14349篇 |
2012年 | 11267篇 |
2011年 | 13694篇 |
2010年 | 10323篇 |
2009年 | 10554篇 |
2008年 | 12841篇 |
2007年 | 12727篇 |
2006年 | 11556篇 |
2005年 | 10434篇 |
2004年 | 9673篇 |
2003年 | 8701篇 |
2002年 | 8891篇 |
2001年 | 9676篇 |
2000年 | 7332篇 |
1999年 | 5751篇 |
1998年 | 5000篇 |
1997年 | 4968篇 |
1996年 | 4514篇 |
1995年 | 4148篇 |
1994年 | 4196篇 |
1993年 | 3936篇 |
1992年 | 4523篇 |
1991年 | 4720篇 |
1990年 | 4512篇 |
1989年 | 4585篇 |
1988年 | 4487篇 |
1987年 | 4357篇 |
1986年 | 4150篇 |
1985年 | 5272篇 |
1984年 | 5457篇 |
1983年 | 4613篇 |
1982年 | 4726篇 |
1981年 | 4563篇 |
1980年 | 4309篇 |
1979年 | 4802篇 |
1978年 | 4921篇 |
1977年 | 4942篇 |
1976年 | 4983篇 |
1975年 | 4691篇 |
1974年 | 4682篇 |
1973年 | 4753篇 |
1972年 | 3487篇 |
1971年 | 3204篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
William F. Trench 《Annali di Matematica Pura ed Applicata》1985,142(1):293-302
Summary
Conti defined t
similarity of systems (1)x=tA(t)xand (2)y=B(t)y, and showed that it is an equivalence relation which preserves uniform and strict stability. Here the definition is weakened by imposing less stringent integrability conditions, some in terms of perhaps conditionally convergent improper integrals, on the matrix function relating A and B. The extended relation, t
quasi-similarity, is not symmetric or transitive; however, it is shown that if (2) is t
quasi-similar to (1)and (1)is uniformly, uniformly asymptotically, or strictly stable, then so is (2).Results are also given concerning linear asymptotic equilibrium of (2)in the case where (1)is stricly stable or has linear asymptotic equilibrium. 相似文献
992.
N. V. Proskurin 《Journal of Mathematical Sciences》1985,29(2):1219-1229
One presents a method for the expansion of functions F:SL(m,)h that are automorphic with respect ot the congruence subgroup in SL(m,). For m=2 the method gives the usual expansion into Fourier series. One gives a comparison with the expansion presented previously by the author in the paper: The expansion of automorphic functions, J. Sov. Math.,26, No. 3 (1984).Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 129, pp. 164–176, 1983. 相似文献
993.
Polymeric dicyanoketene acetals (DCKA) were synthesized by copolymerization of styrene and divinylbenzene or ethylene glycol dimethacrylate. These novel polymers could be used successfully as recyclable pi-acid catalysts in monothioacetalization or carbon-carbon bond forming reaction of acetals. 相似文献
994.
995.
A. N. Fletcher 《Applied physics. B, Lasers and optics》1985,37(1):31-34
Reducing the diameter of the flashlamp was found to increase the percent improvement in output of a solid-state laser caused by using luminescent coolants. However, this change in diameter also reduced the effectiveness of the flashlamp in producing long (150 s) laser pulses so that an overall decrease in laser output was observed. In the formation of short (40 s) laser pulses, on the other hand, larger absolute values were obtained using the smaller diameter flashlamp. 相似文献
996.
V. A. Kiyashko A. K. Popov V. P. Timofeev N. P. Makarov V. Sh. Epstein 《Applied physics. B, Lasers and optics》1985,36(1):53-54
Generation of the second- and fourth-order harmonics of laser radiation is reported in Mg vapor at the forbidden 3s
21
S
o–4s
1
S
o transition. The conversion efficiency for the second-order harmonics has been measured to be 10–2% and for the fourth one 10–8%. 相似文献
997.
Effects of electron-core relaxation in the excitation of atomic systems are considered. A new approach to the consideration of relaxation is proposed, and the corresponding equations are obtained. In the -electron approximation, the first excited states of some organic molecules are calculated by the V(N–1)-potential method, the Morokuma-Iwata method, and a method proposed in the present work.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 55–59, October, 1985. 相似文献
998.
999.
1000.
Evstigneeva R. P. Luzgina V. N. Timashev P. S. Ol'shevskaya V. A. Zakharkin L. I. 《Russian Journal of General Chemistry》2003,73(10):1648-1652
Basing on protoporphyrin IX, its monobenzyl ester, deuteroporphyrin IX, 9-hydroxymethyl-m- and 9-hydroxymethyl-p-carboranes, mono- and dicarborane-containing porphyrins were prepared. 相似文献