全文获取类型
收费全文 | 719678篇 |
免费 | 10578篇 |
国内免费 | 2991篇 |
专业分类
化学 | 389700篇 |
晶体学 | 10075篇 |
力学 | 31323篇 |
综合类 | 78篇 |
数学 | 91884篇 |
物理学 | 210187篇 |
出版年
2021年 | 5714篇 |
2020年 | 6560篇 |
2019年 | 7009篇 |
2018年 | 8956篇 |
2017年 | 8787篇 |
2016年 | 13954篇 |
2015年 | 9393篇 |
2014年 | 13393篇 |
2013年 | 33451篇 |
2012年 | 26412篇 |
2011年 | 31810篇 |
2010年 | 21952篇 |
2009年 | 21710篇 |
2008年 | 29226篇 |
2007年 | 29078篇 |
2006年 | 27159篇 |
2005年 | 24649篇 |
2004年 | 22422篇 |
2003年 | 19723篇 |
2002年 | 19332篇 |
2001年 | 20851篇 |
2000年 | 16128篇 |
1999年 | 12470篇 |
1998年 | 10383篇 |
1997年 | 10131篇 |
1996年 | 10072篇 |
1995年 | 8904篇 |
1994年 | 8812篇 |
1993年 | 8539篇 |
1992年 | 9441篇 |
1991年 | 9410篇 |
1990年 | 8983篇 |
1989年 | 8729篇 |
1988年 | 8608篇 |
1987年 | 8413篇 |
1986年 | 8094篇 |
1985年 | 10826篇 |
1984年 | 10992篇 |
1983年 | 8938篇 |
1982年 | 9341篇 |
1981年 | 9092篇 |
1980年 | 8461篇 |
1979年 | 8986篇 |
1978年 | 9347篇 |
1977年 | 9237篇 |
1976年 | 9186篇 |
1975年 | 8617篇 |
1974年 | 8628篇 |
1973年 | 8677篇 |
1972年 | 6108篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
In the pursuit to enlarge the library of polyimide materials for energy applications, new polyimide/MWCNTs composite films have been developed by MWCNTs-assisted polycondensation reaction of a hydroxyl and triphenylmethane-containing diamine with benzophenone tetracarboxylic dianhydride targeting to highlight their electrical storage capability as flexible electrodes in micro-supercapacitors (mSCs). The Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, UV–vis, fluorescence, and Raman spectroscopies were used to demonstrate the evolution of interfacial interactions between MWCNTs and the precursors (diamine monomer and intermediate polyamidic acid) and polyimide matrix that proved to be the origin of MWCNTs homogeneous dispersion. Thus, composite films incorporating 1, 3, 5, and 10 w.t.% MWCNTs were obtained and thoroughly investigated with regard to their morphology, mechanical behavior, thermal stability, and electrical conductivity. The electrochemical performance of these composites was first analyzed in a classical three-electrode cell by cyclic voltammetry and galvanostatic charge-discharge in both aqueous and organic electrolyte systems. By far, the best electrical storage capacity was obtained with the composite polyimide film containing 10% MWCNTs that was further used as both active material and current collector in a flexible symmetric mSC realized by a straightforward and low-cost procedure. In the attempt to better exploit the advantages of this composite film, it was layered with a graphite-containing paint and tested as an electrode in a flexible mSC, which provided satisfactory results. To our knowledge, this is the first report on the electrical charge storage capability of a polyimide/MWCNTs free-standing film as a flexible electrode in mSCs, which do not require time- and resource-consuming processing steps. 相似文献
12.
Petrov P. A. Filippova E. A. Kompankov N. B. Sukhikh T. S. Sokolov M. N. 《Journal of Structural Chemistry》2022,63(3):470-475
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the... 相似文献
13.
Dominik Vítek Prof. Aleš Růžička Lise Vermeersch Dr. Libor Dostál Dr. Jan Turek Prof. Roman Jambor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202202639
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed. 相似文献
14.
Peralta Cecilia Mariana Acosta Gimena Henestrosa Cecilia Gil Raúl Andrés Fernández Liliana Patricia 《Journal of Analytical Chemistry》2022,77(3):308-317
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,... 相似文献
15.
Herraiz A. Gutierrez M. Ortega-Mier M. 《Central European Journal of Operations Research》2022,30(4):1427-1450
Central European Journal of Operations Research - We define a geometric transformation of Euclidean Travelling Salesman Problem (TSP) tours that leads to a new formulation of the TSP. For every... 相似文献
16.
Bazarra Noelia Castejón Alberto Fernández José R. Quintanilla Ramón 《Meccanica》2021,56(12):3025-3037
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within... 相似文献
17.
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
18.
Yuki Shintani Taku Ohtomi Dr. Aya Shibata Dr. Yoshiaki Kitamura Koichiro M. Hirosawa Prof. Kenichi G. N. Suzuki Prof. Masato Ikeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202104421
Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging. 相似文献
19.
Journal of Structural Chemistry - Atomic and electronic structures of cyclic organosilicon compound 9,9,10,10-tetraethynyl-9,10-dihydrodisilaanthracene are studied by the density functional theory.... 相似文献
20.
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