全文获取类型
收费全文 | 453479篇 |
免费 | 5017篇 |
国内免费 | 1889篇 |
专业分类
化学 | 250150篇 |
晶体学 | 6647篇 |
力学 | 19478篇 |
综合类 | 68篇 |
数学 | 51706篇 |
物理学 | 132336篇 |
出版年
2019年 | 3806篇 |
2018年 | 5069篇 |
2017年 | 5096篇 |
2016年 | 7413篇 |
2015年 | 4647篇 |
2014年 | 7138篇 |
2013年 | 18033篇 |
2012年 | 14276篇 |
2011年 | 17465篇 |
2010年 | 12416篇 |
2009年 | 12105篇 |
2008年 | 16401篇 |
2007年 | 16691篇 |
2006年 | 15625篇 |
2005年 | 14224篇 |
2004年 | 12885篇 |
2003年 | 11556篇 |
2002年 | 11480篇 |
2001年 | 12525篇 |
2000年 | 9691篇 |
1999年 | 7260篇 |
1998年 | 6262篇 |
1997年 | 6263篇 |
1996年 | 5994篇 |
1995年 | 5437篇 |
1994年 | 5653篇 |
1993年 | 5230篇 |
1992年 | 5899篇 |
1991年 | 5892篇 |
1990年 | 5667篇 |
1989年 | 5539篇 |
1988年 | 5613篇 |
1987年 | 5453篇 |
1986年 | 5300篇 |
1985年 | 7069篇 |
1984年 | 7369篇 |
1983年 | 6082篇 |
1982年 | 6485篇 |
1981年 | 6170篇 |
1980年 | 6143篇 |
1979年 | 6257篇 |
1978年 | 7311篇 |
1977年 | 7032篇 |
1976年 | 6699篇 |
1975年 | 6072篇 |
1974年 | 6261篇 |
1973年 | 6414篇 |
1972年 | 4785篇 |
1971年 | 3917篇 |
1968年 | 3609篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Immobilized Catalysts for Iridium‐Catalyzed Allylic Amination: Rate Enhancement by Immobilization
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Chandi C. Malakar Prof. Dr. Günter Helmchen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7127-7134
The first immobilized catalyst for Ir‐catalyzed asymmetric allylic aminations is described. The catalyst is a cationic (π‐allyl)Ir complex bound by cation exchange to an anionic silica gel support. Preparation of the catalyst is facile, and the supported catalyst displayed considerably enhanced activity compared with the parent homogeneous catalyst. Up to 43 consecutive amination runs were possible in recycling experiments. 相似文献
152.
153.
Gelikonov G. V. Ksenofontov S. Yu. Shilyagin P. A. Gelikonov V. M. 《Radiophysics and Quantum Electronics》2019,62(3):228-236
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in... 相似文献
154.
A.G. Rousskikh A.V. Fedyunin A.P. Artyomov A.S. Zhigalin V.I. Oreshkin 《Current Applied Physics》2019,19(6):704-708
The aim of the study presented in this paper was to characterize quantitatively the erosion of aluminum cathodes in high-current vacuum arcs. The experimental setup comprised two current generators. The first one, capable of generating a current of amplitude up to 350 kA, was used to produce a plasma jet, that is, the object to be investigated. The second generator was used to produce a source of probe radiation for imaging the object under investigation in soft x rays of energy ?ν ≈ 0.5–3 keV. The findings of the study are based on experimental data obtained by electrophysical and radiographic methods. It has been shown that the cathode erosion rate in a high-current vacuum arc is a function of the charge passed through the cathode. 相似文献
155.
Yamshchikov V. M. Rogachev V. G. Kudryashov E. A. Kachalin G. N. 《Optics and Spectroscopy》2020,128(8):1182-1186
Optics and Spectroscopy - The population kinetics of a two-level system has been theoretically investigated taking into account the transfer of spontaneous radiation under continuous optical... 相似文献
156.
Synthesis,Electronic Properties and WOLED Devices of Planar Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. François Riobé Rózsa Szűcs Dr. Pierre‐Antoine Bouit Dr. Denis Tondelier Bernard Geffroy Fátima Aparicio Julia Buendía Prof. Luis Sánchez Prof. Régis Réau Prof. László Nyulászi Prof. Muriel Hissler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6547-6556
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs). 相似文献
157.
158.
Sh. M. Khaliullin V. D. Zhuravlev V. G. Bamburov L. V. Ermakova 《Physics of Atomic Nuclei》2015,78(12):1382-1388
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics. 相似文献
159.
Dr. Zhoulong Fan Katherine L. Bay Dr. Xiangyang Chen Zhe Zhuang Han Seul Park Dr. Kap-Sun Yeung Prof. Dr. K. N. Houk Prof. Dr. Jin-Quan Yu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4800-4807
A simple and efficient nitrile-directed meta-C−H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U-shaped template to achieve a molecular U-turn and assemble the large-sized cyclophane transition state for the remote C−H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta-C−H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta-selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand-containing Pd–Ag heterodimeric transition state (TS) favors the desired remote meta-selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non-directed meta-C−H activation. Substituted 2-pyridone ligands were found to be key in assisting the cleavage of the meta-C−H bond in the concerted metalation–deprotonation (CMD) process. 相似文献
160.
Romanenko G. V. Letyagin G. A. Maryunina K. Yu. Bogomyakov A. S. Nishihara S. Inoue K. Ovcharenko V. I. 《Russian Chemical Bulletin》2020,69(8):1530-1536
Russian Chemical Bulletin - The study is concerned with structural rearrangements in the crystals of heterospin complexes Cu(hfac)2 with nitroxide radicals LR (hfac is hexafluoroacetylacetonate, LR... 相似文献