全文获取类型
收费全文 | 12056篇 |
免费 | 387篇 |
国内免费 | 32篇 |
专业分类
化学 | 8275篇 |
晶体学 | 30篇 |
力学 | 169篇 |
综合类 | 1篇 |
数学 | 2240篇 |
物理学 | 1760篇 |
出版年
2020年 | 108篇 |
2019年 | 105篇 |
2016年 | 214篇 |
2015年 | 214篇 |
2014年 | 250篇 |
2013年 | 437篇 |
2012年 | 342篇 |
2011年 | 343篇 |
2010年 | 268篇 |
2009年 | 254篇 |
2008年 | 354篇 |
2007年 | 341篇 |
2006年 | 354篇 |
2005年 | 316篇 |
2004年 | 295篇 |
2003年 | 294篇 |
2002年 | 302篇 |
2001年 | 238篇 |
2000年 | 208篇 |
1999年 | 160篇 |
1998年 | 135篇 |
1997年 | 167篇 |
1996年 | 153篇 |
1995年 | 143篇 |
1994年 | 166篇 |
1993年 | 182篇 |
1992年 | 175篇 |
1991年 | 145篇 |
1990年 | 157篇 |
1989年 | 158篇 |
1988年 | 168篇 |
1987年 | 175篇 |
1986年 | 147篇 |
1985年 | 262篇 |
1984年 | 232篇 |
1983年 | 147篇 |
1982年 | 196篇 |
1981年 | 185篇 |
1980年 | 225篇 |
1979年 | 224篇 |
1978年 | 223篇 |
1977年 | 249篇 |
1976年 | 223篇 |
1975年 | 191篇 |
1974年 | 153篇 |
1973年 | 208篇 |
1972年 | 111篇 |
1971年 | 94篇 |
1970年 | 78篇 |
1967年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Timm Bergholz Dr. Benjamin Oelkers Dr. Benedikt Huber Prof. Bernhard Roling Prof. Dr. Jörg Sundermeyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2613-2620
New salts based on imidazolium, pyrrolidinium, phosphonium, guanidinium, and ammonium cations together with the 5‐cyanotetrazolide anion [C2N5]? are reported. Depending on the nature of cation–anion interactions, characterized by XRD, the ionic liquids (ILs) have a low viscosity and are liquid at room temperature or have higher melting temperatures. Thermogravimetric analysis, cyclic voltammetry, viscosimetry, and impedance spectroscopy display a thermal stability up to 230 °C, an electrochemical window of 4.5 V, a viscosity of 25 mPa s at 20 °C, and an ionic conductivity of 5.4 mS cm?1 at 20 °C for the IL 1‐butyl‐1‐methylpyrrolidinium 5‐cyanotetrazolide [BMPyr][C2N5]. On the basis of these results, the synthesized compounds are promising electrolytes for lithium‐ion batteries. 相似文献
2.
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
3.
P. Seelig A. Dax S. Faber M. Gerlach G. Huber T. Kühl D. Marx P. Merz W. Quint F. Schmitt H. Winter M. Würtz 《Hyperfine Interactions》1998,114(1-4):135-139
The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric
and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in 207Pb81+. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique
using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics
from an ion beam at relativistic velocities.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献
5.
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
6.
7.
8.
9.
10.
C. Czeranowsky V. M. Baev G. Huber P. A. Khandokhin Ya. I. Khanin I. V. Koryukin E. Yu. Shirokov 《Radiophysics and Quantum Electronics》2004,47(10-11):723-728
Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser. 相似文献