全文获取类型
收费全文 | 569969篇 |
免费 | 5258篇 |
国内免费 | 1675篇 |
专业分类
化学 | 273546篇 |
晶体学 | 9133篇 |
力学 | 29036篇 |
综合类 | 8篇 |
数学 | 80187篇 |
物理学 | 184992篇 |
出版年
2021年 | 4182篇 |
2020年 | 4552篇 |
2019年 | 5162篇 |
2018年 | 12754篇 |
2017年 | 13318篇 |
2016年 | 12680篇 |
2015年 | 6416篇 |
2014年 | 9807篇 |
2013年 | 23477篇 |
2012年 | 20581篇 |
2011年 | 30063篇 |
2010年 | 20696篇 |
2009年 | 20627篇 |
2008年 | 26779篇 |
2007年 | 29142篇 |
2006年 | 18200篇 |
2005年 | 20493篇 |
2004年 | 17099篇 |
2003年 | 15534篇 |
2002年 | 14130篇 |
2001年 | 15443篇 |
2000年 | 11819篇 |
1999年 | 9126篇 |
1998年 | 7641篇 |
1997年 | 7393篇 |
1996年 | 7155篇 |
1995年 | 6308篇 |
1994年 | 6205篇 |
1993年 | 6156篇 |
1992年 | 6623篇 |
1991年 | 6915篇 |
1990年 | 6580篇 |
1989年 | 6435篇 |
1988年 | 6269篇 |
1987年 | 6285篇 |
1986年 | 5882篇 |
1985年 | 7745篇 |
1984年 | 7988篇 |
1983年 | 6505篇 |
1982年 | 6750篇 |
1981年 | 6470篇 |
1980年 | 6280篇 |
1979年 | 6662篇 |
1978年 | 6712篇 |
1977年 | 6612篇 |
1976年 | 6720篇 |
1975年 | 6235篇 |
1974年 | 6208篇 |
1973年 | 6321篇 |
1972年 | 4456篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
11.
Dr. Jordan Donat Mr. Patrick Dubourdeaux Dr. Martin Clémancey Dr. Julia Rendon Clara Gervasoni Mr. Morgan Barbier Jessica Barilone Dr. Jacques Pécaut Prof. Dr. Serge Gambarelli Prof. Dr. Pascale Maldivi Prof. Dr. Jean-Marc Latour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202201875
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor. 相似文献
12.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,... 相似文献
13.
Aequationes mathematicae - In this paper, we establish a new class of dynamic inequalities of Hardy’s type which generalize and improve some recent results given in the literature. More... 相似文献
14.
Journal of Experimental and Theoretical Physics - The surface current density of charge carriers in two-dimensional doubly periodic n-type semiconductor superlattices in an external magnetic field... 相似文献
15.
Tsyganova S. I. Fetisova O. Yu. Mazurova E. N. Taran O. P. Kuznetsov B. N. 《Russian Journal of Applied Chemistry》2022,95(3):408-416
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed.... 相似文献
16.
Roopa K. P. Keshavamurthy K. Mahesh B. Veena K. P. Shankara B. S. Basavaiah K. 《Journal of Applied Spectroscopy》2022,89(4):809-818
Journal of Applied Spectroscopy - Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The... 相似文献
17.
Moroz Ya. A. Lozinskyy N. S. Lopanov A. N. Chebyshev K. A. 《Russian Journal of General Chemistry》2022,92(1):101-107
Russian Journal of General Chemistry - Tungstophosphatozincates with the Keggin anion structure Kt5[PW11O39Zn(H2O)]?nH2O, Kt = Rb+, Cs+, (CH3)4N+; (C2H5)4N+ were synthesized. Their... 相似文献
18.
Filatova S. M. Guseva M. K. Bodrova T. G. Parshina D. V. Budanova U. A. Sebyakin Yu. L. 《Russian Journal of General Chemistry》2022,91(1):S13-S23
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial... 相似文献
19.
Knyazev Yu. V. Kazak N. V. Gavrichkov V. A. Polukeev S. I. Ovchinnikov S. G. 《JETP Letters》2022,116(8):567-573
JETP Letters - Changes in the magnetic properties of FeBO3 single crystals in the course of spin crossover occurring with increasing pressure up to 63 GPa are studied both experimentally and... 相似文献
20.
Varfolomeev S. D. Panin A. A. Semenova N. A. Ublinskiy M. V. Akhadov T. A. Bykov V. I. Tsybenova S. B. 《Russian Chemical Bulletin》2022,71(3):591-594
A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.
相似文献