全文获取类型
收费全文 | 10385篇 |
免费 | 335篇 |
国内免费 | 32篇 |
专业分类
化学 | 7288篇 |
晶体学 | 23篇 |
力学 | 151篇 |
综合类 | 1篇 |
数学 | 2077篇 |
物理学 | 1212篇 |
出版年
2020年 | 74篇 |
2019年 | 86篇 |
2016年 | 183篇 |
2015年 | 173篇 |
2014年 | 231篇 |
2013年 | 407篇 |
2012年 | 268篇 |
2011年 | 259篇 |
2010年 | 228篇 |
2009年 | 216篇 |
2008年 | 291篇 |
2007年 | 272篇 |
2006年 | 299篇 |
2005年 | 278篇 |
2004年 | 253篇 |
2003年 | 260篇 |
2002年 | 271篇 |
2001年 | 191篇 |
2000年 | 171篇 |
1999年 | 117篇 |
1998年 | 111篇 |
1997年 | 138篇 |
1996年 | 139篇 |
1995年 | 121篇 |
1994年 | 126篇 |
1993年 | 146篇 |
1992年 | 144篇 |
1991年 | 122篇 |
1990年 | 131篇 |
1989年 | 137篇 |
1988年 | 140篇 |
1987年 | 141篇 |
1986年 | 121篇 |
1985年 | 228篇 |
1984年 | 199篇 |
1983年 | 125篇 |
1982年 | 170篇 |
1981年 | 157篇 |
1980年 | 199篇 |
1979年 | 196篇 |
1978年 | 198篇 |
1977年 | 230篇 |
1976年 | 186篇 |
1975年 | 173篇 |
1974年 | 135篇 |
1973年 | 190篇 |
1972年 | 100篇 |
1971年 | 90篇 |
1970年 | 73篇 |
1933年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Robin F. Weitkamp Beate Neumann Hans‐Georg Stammler Berthold Hoge 《Angewandte Chemie (International ed. in English)》2020,59(14):5494-5499
We report on the first examples of isolated silanol–silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol–silanolate anions are postulated intermediates in the hydroxide‐mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization. 相似文献
2.
Let A be a symmetric matrix of size n×n with entries in some (commutative) field K. We study the possibility of decomposing A into two blocks by conjugation by an orthogonal matrix T∈Matn(K). We say that A is absolutely indecomposable if it is indecomposable over every extension of the base field. If K is formally real then every symmetric matrix A diagonalizes orthogonally over the real closure of K. Assume that K is a not formally real and of level s. We prove that in Matn(K) there exist symmetric, absolutely indecomposable matrices iff n is congruent to 0, 1 or −1 modulo 2s. 相似文献
3.
A comprehensive study of the excited electronic states of HCl is reported. Using resonance enhanced multiphoton ionization ((2 + 1) REMPI) and time-of-flight mass spectrometry (TOFMS) over 120 band systems are analyzed. Supersonic jet techniques are used to prepare rotationally cold species for laser spectroscopy in the 77 000 to 96 000 cm−1 region. At least 50 new electronic states are characterized as well as several features only tentatively assigned previously. A long vibrational progression consisting of 29 vibrational levels of the deeply bound V1Σ+(0+) valence/ion-pair state is studied. We also extend the identification and analysis to high vibrational levels of low-lying Rydberg states. The assignments of [2Πi] Rydberg state complexes are evaluated in terms of spin-orbit coupling and united-atom calculations. In several band systems, the spectra exhibit anomalous rotational line intensities and broadened linewidths which are consistent with predissociation. Multiphoton ionization with mass spectrometry permits the investigation of isotope effects as well as the appearance of fragment species associated with repulsive potential curves. 相似文献
4.
5.
6.
7.
8.
Hans Maaß 《Mathematische Annalen》1941,118(1):312-318
Ohne Zusammenfassung 相似文献
9.
Keller Teichmann Hans Pfeiffer W. Langenbeck A. Reid Heinrich Menzel Th. Höpner W. Mühlsteph M. Ulmann Geib R. E. Liesegang 《Colloid and polymer science》1939,87(1):100-104
Ohne Zusammenfassung 相似文献
10.
Erich Miersemann Hans D. Mittelmann W. Trnig 《Mathematical Methods in the Applied Sciences》1989,11(1):95-104
In this paper we generalize recent theoretical results on the local continuation of parameter-dependent non-linear variational inequalities. The variational inequalities are rather general and describe, for example, the buckling of beams, plates or shells subject to obstacles. Under a technical hypothesis that is satisfied by the simply supported beam, we obtain the existence of a continuation of both the solution and the eigenvalue with respect to a local parameter. A numerical continuation method is presented that easily overcomes turning points. Numerical results are presented for the non-linear beam. 相似文献