全文获取类型
收费全文 | 528篇 |
免费 | 25篇 |
国内免费 | 3篇 |
专业分类
化学 | 334篇 |
晶体学 | 3篇 |
力学 | 6篇 |
数学 | 50篇 |
物理学 | 163篇 |
出版年
2024年 | 1篇 |
2023年 | 18篇 |
2022年 | 16篇 |
2021年 | 19篇 |
2020年 | 18篇 |
2019年 | 18篇 |
2018年 | 8篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 24篇 |
2014年 | 25篇 |
2013年 | 45篇 |
2012年 | 50篇 |
2011年 | 42篇 |
2010年 | 27篇 |
2009年 | 20篇 |
2008年 | 30篇 |
2007年 | 29篇 |
2006年 | 12篇 |
2005年 | 26篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 1篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1965年 | 1篇 |
1939年 | 2篇 |
1938年 | 1篇 |
排序方式: 共有556条查询结果,搜索用时 0 毫秒
71.
Bhardwaj Hema Singh Chandan Kotnala R. K. Sumana Gajjala 《Analytical and bioanalytical chemistry》2018,410(28):7313-7323
Analytical and Bioanalytical Chemistry - Due to the similar electrochemical properties to graphene oxide (GO), graphene quantum dots (GQDs) are considered as a highly potential candidate for... 相似文献
72.
Dey S Pal C Nandi D Giri VS Zaidlewicz M Krzeminski M Smentek L Hess BA Gawronski J Kwit M Babu NJ Nangia A Jaisankar P 《Organic letters》2008,10(7):1373-1376
3,3'-Bipyrroles 3 could be synthesized using a double Michael addition reaction involving diaroyl acetylene 1 and the appropriate 1,3-dicarbonyls 2 using ammonium acetate as a nitrogen source. The axial chirality of bipyrrole was anticipated from the X-ray crystal structure and DFT calculations and confirmed by separating the racemates on a chiral column and subsequent CD spectra of the enantiomers. The absolute configuration of the enantiomers was achieved by theoretical CD spectra calculation using the ZINDO method. 相似文献
73.
74.
2,2,5-Trisubstituted pyrrolidines are available from allylic pyroglutamates by Ireland-Claisen ester rearrangement followed by Eschenmoser sulfide contraction and reduction in a highly diastereoselective and efficient sequence. Some of the products from this sequence exhibit activity against S. aureus, but are much less active against E. coli. 相似文献
75.
76.
Podder Soumik Halder Suman Roychowdhury Anirban Das Dipankar Ghosh Chandan Kr. 《Journal of nanoparticle research》2016,18(10):1-13
Journal of Nanoparticle Research - With the widespread use of titanium dioxide (TiO2) human exposure is inevitable, but the exposure data on TiO2 are still limited. This study adopted off-line... 相似文献
77.
Using the heavy quark approximation, we have studied the nonleptonic decay mode Λ
b
→Λ
c
a
1. We have included nonfactorizable contributions as well as factorizable ones in our analysis. The estimated branching ratio
for this process is (1.4±0.1)% and the asymmetry parameter α found to be −0.8. 相似文献
78.
The cross-coupling reaction of α-arylacetyl chlorides with triarylbismuths was studied under Pd-catalyzed conditions. The reaction was found to be facile under the established protocol and furnished high yields of α-aryl ketones in short reaction times. This work also demonstrated a facile synthesis of various regio-isomeric mono-, di- and tri-substituted α-aryl ketones in high yields. Triarylbismuths were employed as sub-stoichiometric multi-coupling organometallic nucleophiles in this coupling protocol. 相似文献
79.
Chandan Kumar Jana Dr. Stefan Grimme Prof. Dr. Armido Studer Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9078-9084
CuI‐catalyzed enantioselective nitroso‐Diels–Alder reactions (NDA reactions) of 2‐nitrosopyridine with various dienes are presented. The [CuPF6(MeCN)4]/Walphos‐CF3 catalyst system is best suited to catalyze the NDA reaction of various dienes by using 2‐nitrosopyridine as a dienophile. In most of the cases studied, cycloadducts are obtained in quantitative yield with very good to excellent enantioselectivities. Based on DFT calculations, a model to explain the stereochemical outcome of the NDA reaction is presented. Finally, an efficient short synthesis of (?)‐peracetylated conduramine A‐1 by applying the enantioselective NDA reaction as a key step is described. 相似文献
80.
Chandan K. Dubey 《Discrete Applied Mathematics》2009,157(1):149-163
An undirected graph G=(V,E) with a specific subset X⊂V is called X-critical if G and G(X), induced subgraph on X, are indecomposable but G(V−{w}) is decomposable for every w∈V−X. This is a generalization of critically indecomposable graphs studied by Schmerl and Trotter [J.H. Schmerl, W.T. Trotter, Critically indecomposable partially ordered sets, graphs, tournaments and other binary relational structures, Discrete Mathematics 113 (1993) 191-205] and Bonizzoni [P. Bonizzoni, Primitive 2-structures with the (n−2)-property, Theoretical Computer Science 132 (1994) 151-178], who deal with the case where X is empty.We present several structural results for this class of graphs and show that in every X-critical graph the vertices of V−X can be partitioned into pairs (a1,b1),(a2,b2),…,(am,bm) such that G(V−{aj1,bj1,…,ajk,bjk}) is also an X-critical graph for arbitrary set of indices {j1,…,jk}. These vertex pairs are called commutative elimination sequence. If G is an arbitrary indecomposable graph with an indecomposable induced subgraph G(X), then the above result establishes the existence of an indecomposability preserving sequence of vertex pairs (x1,y1),…,(xt,yt) such that xi,yi∈V−X. As an application of the commutative elimination sequence of an X-critical graph we present algorithms to extend a 3-coloring (similarly, 1-factor) of G(X) to entire G. 相似文献