全文获取类型
收费全文 | 407篇 |
免费 | 28篇 |
专业分类
化学 | 224篇 |
晶体学 | 1篇 |
力学 | 9篇 |
数学 | 45篇 |
物理学 | 156篇 |
出版年
2023年 | 8篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 16篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 22篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 17篇 |
2012年 | 28篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 14篇 |
2008年 | 22篇 |
2007年 | 21篇 |
2006年 | 8篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 5篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 7篇 |
1929年 | 2篇 |
排序方式: 共有435条查询结果,搜索用时 140 毫秒
41.
Intramolecular Formal anti‐Carbopalladation/Heck Reaction: Facile Domino Access to Carbo‐ and Heterooligocyclic Dienes 下载免费PDF全文
Martin Pawliczek Bastian Milde Prof. Dr. Peter G. Jones Prof. Dr. Daniel B. Werz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(35):12303-12307
An intramolecular domino process consisting of a formal anti‐carbopalladation followed by Heck reaction is realized. Complex oligo(hetero)cyclic scaffolds are efficiently obtained in one synthetic step from easily obtainable enyne precursors. In contrast to common syn‐carbopalladation reactions of alkyne units, the carbopalladation employed here is designed to afford an anti‐arrangement of the two new substituents across the emerging double bond. A prerequisite is that the residues next to the alkyne should lack any β‐hydrogen atoms. The method paves the way to tri‐ and tetrasubstituted double‐bond systems that have not been accessible by conventional Pd catalysis. 相似文献
42.
Back Cover: Switch‐On Fluorescence of a Perylene‐Dye‐Functionalized Metal–Organic Framework through Postsynthetic Modification (Chem. Eur. J. 30/2015) 下载免费PDF全文
43.
Mayilmurugan R Harum BN Volpe M Sax AF Palaniandavar M Mösch-Zanetti NC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(2):704-713
The asymmetric molybdenum(VI) dioxo complexes of the bis(phenolate) ligands 1,4‐bis(2‐hydroxybenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐methylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐dimethylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐di‐tert‐butylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐flurobenzyl)‐1,4‐diazepane, and 1,4‐bis(2‐hydroxy‐4‐chlorobenzyl)‐1,4‐diazepane (H2(L1)–H2(L6), respectively) have been isolated and studied as functional models for molybdenum oxotransferase enzymes. These complexes have been characterized as asymmetric complexes of type [MoO2(L)] 1–6 by using NMR spectroscopy, mass spectrometry, elemental analysis, and electrochemical methods. The molecular structures of [MoO2(L)] 1–4 have been successfully determined by single‐crystal X‐ray diffraction analyses, which show them to exhibit a distorted octahedral coordination geometry around molybdenum(VI) in an asymmetrical cis‐β configuration. The Mo? Ooxo bond lengths differ only by ≈0.01 Å. Complexes 1 , 2 , 5 , and 6 exhibit two successive MoVI/MoV (E1/2, ?1.141 to ?1.848 V) and MoV/MoIV (E1/2, ?1.531 to ?2.114 V) redox processes. However, only the MoVI/MoV redox couple was observed for 3 and 4 , suggesting that the subsequent reduction of the molybdenum(V) species is difficult. Complexes 1 , 2 , 5 , and 6 elicit efficient catalytic oxygen‐atom transfer (OAT) from dimethylsulfoxide (DMSO) to PMe3 at 65 °C at a significantly faster rate than the symmetric molybdenum(VI) complexes of the analogous linear bis(phenolate) ligands known so far to exhibit OAT reactions at a higher temperature (130 °C). However, complexes 3 and 4 fail to perform the OAT reaction from DMSO to PMe3 at 65 °C. DFT/B3LYP calculations on the OAT mechanism reveal a strong trans effect. 相似文献
44.
45.
Experimental study of electrostatically stabilized colloidal particles: colloidal stability and charge reversal 总被引:1,自引:0,他引:1
Schneider C Hanisch M Wedel B Jusufi A Ballauff M 《Journal of colloid and interface science》2011,358(1):62-67
We consider the interaction of colloidal spheres in the presence of mono-, di-, and trivalent ions. The colloids are stabilized by electrostatic repulsion due to surface charges. The repulsive part of the interaction potential Ψ(d) is deduced from precise measurements of the rate of slow coagulation. These "microsurface potential measurements" allow us to determine a weak repulsion in which Ψ(d) is of the order of a few k(B)T. These data are compared to ζ potential measured under similar conditions. At higher concentrations both di- and trivalent counterions accumulate at the very proximity of the particle surface leading to charge reversal. The salt concentration c(cr) at which charge reversal occurs is found to be always above the critical coagulation concentration c(ccc). The analysis of Ψ(d) and of the ζ potential demonstrates, however, that adsorption of multivalent counterions starts far below c(cr). Hence, colloid stability in the presence of di- and trivalent ions cannot be described in terms of a DLVO ansatz assuming a surface charge that is constant with regard to the ionic strength. 相似文献
46.
Nuss G Saischek G Harum BN Volpe M Belaj F Mösch-Zanetti NC 《Inorganic chemistry》2011,50(24):12632-12640
Reaction of potassium tris(mercapto-tert-butylpyridazinyl)borate K[Tn(tBu)] with copper(II) chloride in dichloromethane at room temperature led to the diamagnetic copper boratrane compound [Cu{B(Pn(tBu))(3)}Cl] (Pn = pyridazine-3-thionyl) (1) under activation of the B-H bond and formation of a Cu-B dative bond. In contrast to this, stirring of the same ligand with copper(I) chloride in tetrahydrofuran (THF) gave the dimeric compound [Cu{Tn(tBu)}](2) (2) where one copper atom is coordinated by two sulfur atoms and one hydrogen atom of one ligand and one sulfur of the other ligand. Hereby, no activation of the B-H bond occurred but a 3-center-2-electron B-H···Cu bond is formed. The reaction of copper(II) chloride with K[Tn(tBu)] in water gave the same product 2, but a formal reduction of the metal center from Cu(II) to Cu(I) occurred. When adding tricyclohexyl phosphine to the reaction mixture of K[Tn(R)] (R = tBu, Me) and copper(I) chloride in MeOH, the distorted tetrahedral Cu complexes [Cu{Tn(R)}(PCy(3))] (R = tBu 3, Me 4) were formed. Compound 4 is exhibiting an "inverted" κ(3)-H,S,S, coordination mode. The copper boratrane 1 was further investigated by density functional theory (DFT) calculations for a better understanding of the M→B interaction involving the d(8) electron configuration of Cu. 相似文献
47.
Gaidzik N Kaiser A Kowalczyk D Westerlind U Gerlitzki B Sinn HP Schmitt E Kunz H 《Angewandte Chemie (International ed. in English)》2011,50(42):9977-9981
A shot in the arm for cancer treatment: Two MUC1 tetanus toxoid vaccines were synthesized and induced a strong immune response in mice. The antibodies elicited by the vaccines show a high selectivity for the tumor cells in mammary carcinoma tissues and also distinguish between tumor tissues at different stages. 相似文献
48.
We discuss here nano-scale size localized wave excitations, which are intrinsic localized traveling modes in two-dimensional anharmonic crystal lattice systems. In particular, using different initial conditions of coordinates and momenta we search for the longest lasting excitations in triangular lattices. As most stable and longest lasting unaltered appear quasi-one-dimensional Toda-like solitons running in rectilinear chains along the main crystallographic axes of such lattices. Furthermore, by following the trace of high energetic excitations like in “bubble chamber” methodology (or in scanning tunneling microscopy) we show how such localized nonlinear waves appearing spontaneously in heated systems can be detected and followed in space-time. 相似文献
49.
Yu.M. Romanovsky A.V. Kargovsky W. Ebeling 《The European physical journal. Special topics》2013,222(10):2465-2479
We analyze the dynamics of driven translations or rotations based on models with internal oscillations. In particular we discuss several new mechanisms of motors driven by chemical energy. First we study the simple depot model and give analytical solutions including efficiency and stochastic effects. Then we introduce internal oscillations based on inertia including variable friction functions. Further we replace inertia by delay effects and study motors in trigger regime. As possible applications we consider a model of ATP-driven motors operating on angle and elasticity variables. We develop a model of F1-ATPase motors with three β-subunits which drive the rotation of the central γ-shaft. 相似文献
50.