全文获取类型
收费全文 | 4260篇 |
免费 | 108篇 |
国内免费 | 24篇 |
专业分类
化学 | 2377篇 |
晶体学 | 62篇 |
力学 | 129篇 |
数学 | 705篇 |
物理学 | 1119篇 |
出版年
2022年 | 79篇 |
2021年 | 91篇 |
2020年 | 93篇 |
2019年 | 113篇 |
2018年 | 103篇 |
2017年 | 102篇 |
2016年 | 164篇 |
2015年 | 127篇 |
2014年 | 170篇 |
2013年 | 277篇 |
2012年 | 235篇 |
2011年 | 250篇 |
2010年 | 186篇 |
2009年 | 191篇 |
2008年 | 231篇 |
2007年 | 226篇 |
2006年 | 182篇 |
2005年 | 151篇 |
2004年 | 145篇 |
2003年 | 107篇 |
2002年 | 115篇 |
2001年 | 70篇 |
2000年 | 71篇 |
1999年 | 48篇 |
1998年 | 29篇 |
1997年 | 26篇 |
1996年 | 54篇 |
1995年 | 40篇 |
1994年 | 38篇 |
1993年 | 31篇 |
1992年 | 34篇 |
1991年 | 19篇 |
1990年 | 32篇 |
1989年 | 27篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 34篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 22篇 |
1979年 | 20篇 |
1978年 | 36篇 |
1977年 | 22篇 |
1976年 | 25篇 |
1974年 | 16篇 |
1973年 | 16篇 |
1971年 | 18篇 |
排序方式: 共有4392条查询结果,搜索用时 15 毫秒
1.
Dominik Vítek Prof. Aleš Růžička Lise Vermeersch Dr. Libor Dostál Dr. Jan Turek Prof. Roman Jambor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202202639
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed. 相似文献
2.
3.
Musalov M. V. Yakimov V. A. Potapov V. A. Andreev M. V. Amosova S. V. 《Russian Journal of Organic Chemistry》2019,55(11):1809-1811
Russian Journal of Organic Chemistry - The reaction of selenium dichloride with methyl and ethyl propiolates leads to formation of anti-Markovnikov adducts. The regio- and stereoselective synthesis... 相似文献
4.
Molecular n-v complexes of quinoline N-oxides with BF3 have been studied by electronic and IR spectroscopy. In most case the donor centre is the oxygen atom of the N-oxide group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1087–1092, August, 1994. 相似文献
5.
In this work we study nonnegativity and positivity of a discrete quadratic functional with separately varying endpoints. We introduce a notion of an interval coupled with 0, and hence, extend the notion of conjugate interval to 0 from the case of fixed to variable endpoint(s). We show that the nonnegativity of the discrete quadratic functional is equivalent to each of the following conditions: The nonexistence of intervals coupled with 0, the existence of a solution to Riccati matrix equation and its boundary conditions. Natural strengthening of each of these conditions yields a characterization of the positivity of the discrete quadratic functional. Since the quadratic functional under consideration could be a second variation of a discrete calculus of variations problem with varying endpoints, we apply our results to obtain necessary and sufficient optimality conditions for such problems. This paper generalizes our recent work in [R. Hilscher, V. Zeidan, Comput. Math. Appl., to appear], where the right endpoint is fixed. 相似文献
6.
7.
Andreev V. N. Kolyadko E. A. Podlovchenko B. I. 《Russian Journal of Electrochemistry》2004,40(5):580-583
Radioactive tracer studies confirm the earlier electrochemical results that carbon monoxide can virtually completely displace iodine adatoms. For the first time, it is found that iodine adatoms are not displaced by carbon monoxide when iodide anions are adsorbed in the presence of an upd silver monolayer. The possible reasons for the effect observed are discussed. 相似文献
8.
The diffuse scattering of x rays in a four-layer waveguide-type heterostructure is investigated. The dynamic enhancement of
diffuse scattering is detected experimentally in regions corresponding to the excitation of waveguide modes for both the incident
and scattered waves.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 219–223 (25 August 1997) 相似文献
9.
10.
S. S. Andreev A. D. Akhsakhalyan M. A. Bibishkin N. I. Chkhalo S. V. Gaponov S. A. Gusev E. B. Kluenkov K. A. Prokhorov N. N. Salashchenko F. Schafers S. Yu. Zuev 《Central European Journal of Physics》2003,1(1):191-209
We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed
at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss
normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing
of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements
for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography
(ψ-13nm) and short period multilayer optics. 相似文献