全文获取类型
收费全文 | 64248篇 |
免费 | 15856篇 |
国内免费 | 177篇 |
专业分类
化学 | 67849篇 |
晶体学 | 159篇 |
力学 | 2445篇 |
数学 | 6045篇 |
物理学 | 3783篇 |
出版年
2024年 | 378篇 |
2023年 | 4107篇 |
2022年 | 1522篇 |
2021年 | 2622篇 |
2020年 | 4772篇 |
2019年 | 2487篇 |
2018年 | 2460篇 |
2017年 | 783篇 |
2016年 | 5863篇 |
2015年 | 5785篇 |
2014年 | 5278篇 |
2013年 | 5974篇 |
2012年 | 3990篇 |
2011年 | 2089篇 |
2010年 | 3908篇 |
2009年 | 3797篇 |
2008年 | 1943篇 |
2007年 | 1685篇 |
2006年 | 1067篇 |
2005年 | 1074篇 |
2004年 | 945篇 |
2003年 | 787篇 |
2002年 | 711篇 |
2001年 | 284篇 |
1997年 | 318篇 |
1996年 | 368篇 |
1995年 | 338篇 |
1994年 | 285篇 |
1993年 | 392篇 |
1992年 | 285篇 |
1988年 | 283篇 |
1987年 | 273篇 |
1985年 | 392篇 |
1984年 | 361篇 |
1983年 | 311篇 |
1982年 | 404篇 |
1981年 | 385篇 |
1980年 | 486篇 |
1979年 | 436篇 |
1978年 | 460篇 |
1977年 | 585篇 |
1976年 | 596篇 |
1975年 | 652篇 |
1974年 | 660篇 |
1973年 | 455篇 |
1972年 | 454篇 |
1971年 | 455篇 |
1970年 | 613篇 |
1969年 | 480篇 |
1968年 | 516篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
861.
Confinement of CuII–Phthalocyanine in a Bioinspired Hybrid Nanoparticle‐Assembled Structure Yields Selective and Stable Epoxidation Catalysts 下载免费PDF全文
Joydeb Manna Arlin Jose Amali Dr. Rohit Kumar Rana 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8453-8457
Herein, we demonstrate that a bioinspired assembly of silica nanoparticles with polyamines as structure‐directing agents similar to that known for the biosilicification of diatoms can pave the way for the efficient encapsulation of sulfonated copper–phthalocyanine in a hybrid microcapsule structure, in which the organic component provides a capable environment for its catalytic activity in epoxidation reactions and the nanoassembled structure imparts stability. 相似文献
862.
A Strategy for the Preparation of Thioantimonates Based on the Concept of Weak Acids and Corresponding Strong Bases 下载免费PDF全文
Carolin Anderer Natalie Delwa de Alarcón Prof. Dr. Christian Näther Prof. Dr. Wolfgang Bensch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16953-16959
By following a new synthetic approach, which is based on the in situ formation of a basic medium by the reaction between the strong base Sb(V)S43? and the weak acid H2O, it was possible to prepare three layered thioantimonate(III) compounds of composition [TM(2,2′‐bipyridine)3][Sb6S10] (TM=Ni, Fe) and [Ni(4,4′‐dimethyl‐2,2′‐bipyridine)3][Sb6S10] under hydrothermal conditions featuring two different thioantimonate(III) network topologies. The antimony source, Na3SbS4 ? 9 H2O, undergoes several decomposition reactions and produces the SbIIIS3 species, which condenses to generate the layered anion. The application of transition‐metal complexes avoids crystallization of dense phases. The reactions are very fast compared to conventional hydrothermal/solvothermal syntheses and are much less sensitive to changes of the reaction parameters. 相似文献
863.
Palladium‐Catalyzed Stereoselective Intramolecular Oxidative Amidation of Alkenes in the Synthesis of 1,3‐ and 1,4‐Amino Alcohols and 1,3‐Diamines 下载免费PDF全文
Prof. Dr. Andrei V. Malkov Dr. Darren S. Lee Dr. Maciej Barłóg Dr. Mark R. J. Elsegood Prof. Dr. Pavel Kočovský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):4901-4905
An efficient and practical Pd‐catalyzed intramolecular oxidative allylic amidation provides facile access to derivatives of 1,3‐ and 1,4‐amino alcohols and 1,3‐diamines. The method operates under mild reaction conditions (RT) with molecular oxygen (1 atm) as the sole reoxidant of Pd. Excellent diastereoselectivities were attained with substrates bearing a secondary stereogenic center 相似文献
864.
High‐Yield Formation of Substituted Tetracyanobutadienes from Reaction of Ynamides with Tetracyanoethylene 下载免费PDF全文
Dr. Marie Betou Nicolas Kerisit Esme Meledje Dr. Yann R. Leroux Dr. Claudine Katan Dr. Jean‐François Halet Dr. Jean‐Claude Guillemin Dr. Yann Trolez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9553-9557
A high‐yielding sequence of [2+2] cycloaddition–retroelectrocyclization of ynamides with tetracyanoethylene (TCNE) is described. The reaction provided tetracyanobutadiene (TCBD) species, which were characterized by various techniques. DFT and TD‐DFT calculations were also performed to complement experimental findings. 相似文献
865.
Frontispiece: A Multicomponent Conjugation Strategy to Unique N‐Steroidal Peptides: First Evidence of the Steroidal Nucleus as a β‐Turn Inducer in Acyclic Peptides 下载免费PDF全文
866.
A Doping Technique that Suppresses Undesirable H2 Evolution Derived from Overall Water Splitting in the Highly Selective Photocatalytic Conversion of CO2 in and by Water 下载免费PDF全文
Prof. Dr. Kentaro Teramura Zheng Wang Dr. Saburo Hosokawa Prof. Dr. Yoshihisa Sakata Prof. Dr. Tsunehiro Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):9906-9909
Photocatalytic conversion of CO2 to reduction products, such as CO, HCOOH, HCHO, CH3OH, and CH4, is one of the most attractive propositions for producing green energy by artificial photosynthesis. Herein, we found that Ga2O3 photocatalysts exhibit high conversion of CO2. Doping of Zn species into Ga2O3 suppresses the H2 evolution derived from overall water splitting and, consequently, Zn‐doped, Ag‐modified Ga2O3 exhibits higher selectivity toward CO evolution than bare, Ag‐modified Ga2O3. We observed stoichiometric amounts of evolved O2 together with CO. Mass spectrometry clarified that the carbon source of the evolved CO is not the residual carbon species on the photocatalyst surface, but the CO2 introduced in the gas phase. Doping of the photocatalyst with Zn is expected to ease the adsorption of CO2 on the catalyst surface. 相似文献
867.
Magnetic Coupling Constants of Self‐Assembled CuII [3×3] Grids: Alternative Spin Model from Theoretical Calculations 下载免费PDF全文
Dr. Carmen J. Calzado Dr. Nadia Ben Amor Dr. Daniel Maynau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):8979-8987
This paper reports a theoretical analysis of the electronic structure and magnetic properties of a ferromagnetic CuII [3×3] grid. A two‐step strategy, combining calculations on the whole grid and on binuclear fragments, has been employed to evaluate all the magnetic interactions in the grid. The calculations confirm an S=7/2 ground state, which is in accordance with the magnetisation versus field curve and the thermal dependence of the magnetic moment data. Only the first‐neighbour coupling terms present non‐negligible amplitudes, all of them in agreement with the structure and arrangement of the Cu 3d magnetic orbitals. The results indicate that the dominant interaction in the system is the antiferromagnetic coupling between the ring and the central Cu sites (J3=J4≈?31 cm?1). In the ring two different interactions can be distinguished, J1=4.6 cm?1 and J2=?0.1 cm?1, in contrast to the single J model employed in the magnetic data fit. The calculated J values have been used to determine the energy level distribution of the Heisenberg magnetic states. The effective magnetic moment versus temperature plot resulting from this ab initio energy profile is in good agreement with the experimental curve and the fitting obtained with the simplified spin model, despite the differences between these two spin models. This study underlines the role that the theoretical evaluations of the coupling constants can play on the rationalisation of the magnetic properties of these complex polynuclear systems. 相似文献
868.
Cover Picture: Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets (Chem. Eur. J. 6/2014) 下载免费PDF全文
869.
Multivalent Inhibitors for Carbohydrate‐Processing Enzymes: Beyond the “Lock‐and‐Key” Concept 下载免费PDF全文
Dr. Sébastien G. Gouin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11616-11628
During the last decades, tremendous chemical efforts have been dedicated to design monovalent inhibitors of carbohydrate‐processing enzymes, with comparatively few rewards in terms of marketed drugs. Recently, an alternative to the traditional “lock and key” approach has emerged. Multivalency, a widely used strategy for lectin inhibition, has been successfully applied to specific glycosidases and glycosyltransferases. 相似文献
870.
Kanyal Supriya S. Jensen David S. Dadson Andrew E. Vanfleet Richard R. Davis Robert C. Linford Matthew R. 《平面色谱法杂志一现代薄层色谱法》2014,27(3):151-156
JPC – Journal of Planar Chromatography – Modern TLC - We describe the direct, conformal, atomic layer deposition (ALD) of silica onto carbon nanotubes (CNTs) in the microfabrication of... 相似文献