全文获取类型
收费全文 | 65152篇 |
免费 | 18678篇 |
国内免费 | 2361篇 |
专业分类
化学 | 68700篇 |
晶体学 | 306篇 |
力学 | 3283篇 |
综合类 | 187篇 |
数学 | 4698篇 |
物理学 | 9017篇 |
出版年
2024年 | 423篇 |
2023年 | 4361篇 |
2022年 | 2073篇 |
2021年 | 3175篇 |
2020年 | 5292篇 |
2019年 | 3061篇 |
2018年 | 2860篇 |
2017年 | 1196篇 |
2016年 | 6405篇 |
2015年 | 6360篇 |
2014年 | 5936篇 |
2013年 | 6471篇 |
2012年 | 4965篇 |
2011年 | 2901篇 |
2010年 | 4582篇 |
2009年 | 4403篇 |
2008年 | 2297篇 |
2007年 | 2004篇 |
2006年 | 1231篇 |
2005年 | 1077篇 |
2004年 | 770篇 |
2003年 | 672篇 |
2002年 | 603篇 |
2001年 | 472篇 |
2000年 | 433篇 |
1999年 | 501篇 |
1998年 | 377篇 |
1997年 | 454篇 |
1996年 | 387篇 |
1995年 | 437篇 |
1994年 | 388篇 |
1993年 | 457篇 |
1992年 | 294篇 |
1991年 | 264篇 |
1990年 | 232篇 |
1989年 | 187篇 |
1988年 | 200篇 |
1987年 | 187篇 |
1980年 | 208篇 |
1978年 | 189篇 |
1977年 | 309篇 |
1976年 | 361篇 |
1975年 | 458篇 |
1974年 | 471篇 |
1973年 | 284篇 |
1972年 | 369篇 |
1971年 | 355篇 |
1970年 | 541篇 |
1969年 | 413篇 |
1968年 | 456篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Giang Truong Nguyen Prof. Dr. Liviu Ungur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200227
Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs. 相似文献
2.
4.
5.
Dr. H. Schmieg Prof. Dr. P. Vielsack 《Archive of Applied Mechanics (Ingenieur Archiv)》1987,57(6):446-458
Übersicht Betrachtet wird ein zwangserregtes Zweikörpersystem mit wechselnden Bindungen infolge trockener Reibung. Stationäre Bewegungen werden als Grenzfall instationärer Einschwingvorgänge berechnet. Abhängig von den Systemparametern ergeben sich drei typische Bewegungsformen. Ihnen entsprechen dauernde Haftzustände, wechselnde Haft-Gleitzustände oder dauernde Gleitzustände an der Berührfläche beider Körper.
Intermittant constraints in a two-body-system with dry friction
Summary An externally excited two-body-system with intermittant constraints due to dry friction is considered. Stationary motions are calculated as limit cases of instationary transients. Depending on the parameters of the system, three typical modes are of interest. These correspond to permanent sticking, slipstick behaviour, or to permanent slipping in the contact surface of the bodies, respectively.相似文献
6.
7.
The drawbacks of our earlier report of preparing fuel cell catalyst arrays by borohydride reduction of inkjet prepared arrays of metal salts are discussed along with the need for inclusion of state-of-the-art metrics in all array screening. An alternative method for screening of hydrogen/air cathode catalysts, direct methanol fuel cell (DMFC) anode catalysts, and catalyst loading studies is provided. State-of-the-art Johnson Matthey catalysts were used in control experiments to demonstrate the utility of the array fuel cell for high throughput screening of fuel cell catalysts in the 3-4 mg/cm2 range. This report lays out hard learned rules for high throughput screening and demonstrates that the array fuel cell can be used for very precise screening of libraries of membrane electrode assembly (MEA) components without the pitfalls discussed in the introduction. 相似文献
8.
Let T be a bounded linear operator on Hilbert space H, M an invariant subspace of T. If there exists another invariant subspace N of T such that H = M + N and M ∩ N = 0, then M is said to be a completely reduced subspace of T. If T has a nontrivial completely reduced subspace, then T is said to be completely reducible; otherwise T is said to be completely irreducible. In the present paper we briefly sum up works on completely irreducible operators that
have been done by the Functional Analysis Seminar of Jilin University in the past ten years and more.
The paper contains four sections. In section 1 the background of completely irreducible operators is given in detail. Section
2 shows which operator in some well-known classes of operators, for example, weighted shifts, Toeplitz operators, etc., is
completely irreducible. In section 3 it is proved that every bounded linear operator on the Hilbert space can be approximated
by the finite direct sum of completely irreducible operators. It is clear that a completely irreducible operator is a rather
suitable analogue of Jordan blocks in L(H), the set of all bounded linear operators on Hilbert space H. In section 4 several questions concerning completely irreducible operators are discussed and it is shown that some properties
of completely irreducible operators are different from properties of unicellular operators.
__________
Translated from Acta Sci. Nat. Univ. Jilin, 1992, (4): 20–29 相似文献
9.
10.