全文获取类型
收费全文 | 17765篇 |
免费 | 2901篇 |
国内免费 | 2667篇 |
专业分类
化学 | 13250篇 |
晶体学 | 316篇 |
力学 | 1055篇 |
综合类 | 285篇 |
数学 | 2286篇 |
物理学 | 6141篇 |
出版年
2023年 | 293篇 |
2022年 | 418篇 |
2021年 | 479篇 |
2020年 | 737篇 |
2019年 | 701篇 |
2018年 | 593篇 |
2017年 | 569篇 |
2016年 | 847篇 |
2015年 | 954篇 |
2014年 | 1057篇 |
2013年 | 1413篇 |
2012年 | 1661篇 |
2011年 | 1722篇 |
2010年 | 1361篇 |
2009年 | 1260篇 |
2008年 | 1415篇 |
2007年 | 1279篇 |
2006年 | 1148篇 |
2005年 | 933篇 |
2004年 | 756篇 |
2003年 | 592篇 |
2002年 | 575篇 |
2001年 | 424篇 |
2000年 | 357篇 |
1999年 | 270篇 |
1998年 | 177篇 |
1997年 | 168篇 |
1996年 | 146篇 |
1995年 | 127篇 |
1994年 | 99篇 |
1993年 | 109篇 |
1992年 | 78篇 |
1991年 | 68篇 |
1990年 | 69篇 |
1989年 | 45篇 |
1988年 | 54篇 |
1987年 | 25篇 |
1986年 | 35篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 23篇 |
1979年 | 17篇 |
1978年 | 26篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1974年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Xue Jinming Wang Bo Li Ziqiang Xie Zongbo Le Zhanggao 《Research on Chemical Intermediates》2022,48(1):49-65
Research on Chemical Intermediates - In the process of uranium mining and smelting, large quantities of low-concentration uranium-containing wastewater have been produced. It is an ideal solution... 相似文献
2.
3.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device. 相似文献
4.
Jiraya Kiriratnikom Xun Zhang Xiaohan Cao Bo Chu Chengjian Zhang Xinghong Zhang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2262-2268
Facile construction of sulfur-rich polymers using readily available raw chemicals is an area aggressively pursued but challenging. Herein we use common feedstocks of ethylene oxide (EO), propylene oxide (PO), and carbonyl sulfide (COS) to synthesize copoly(thioether)s which are traditionally produced from unpleasant and difficult to store episulfides. In this protocol, the EO/COS coupling selectively generates a pure poly(ethylene sulfide) (PES) with melting temperature (Tm) values up to 172°C and high yields up to 98%. The EO/PO/COS terpolymerization leads to the incorporation of soft poly(propylene sulfide) (PPS) and hard PES segments together, affording a random PES-co-PPS copoly(thioether) with the complete consumption of EO and PO. Additionally, by simply varying the EO/PO feeding ratio, the obtained copoly(thioether)s possess tunable thermal properties, Tm values in the range of 76–144°C, and excellent solubility. These copolymerizations are conducted in one-pot/one-step at industrially favored reaction temperatures of 100–120°C using catalysts of common organic bases, suggesting a facile and practical manner. Especially, the copoly(thioether) exhibits high refractive indices up to 1.68 owing to its high sulfur content, suggesting a broad application prospect in optical materials. 相似文献
5.
WS2由于其优异的物理和光电性质引起了广泛关注。本研究基于第一性原理计算方法,探索了本征单层WS2及不同浓度W原子替位钇(Y)掺杂WS2的电子结构和光学特性。结果表明本征单层WS2为带隙1.814 eV的直接带隙半导体。进行4%浓度(原子数分数)的Y原子掺杂后,带隙减小为1.508 eV,依旧保持着直接带隙的特性,随着Y掺杂浓度的不断增大,掺杂WS2带隙进一步减小,当浓度达到25%时,能带结构转变为0.658 eV的间接带隙,WS2表现出磁性。适量浓度的掺杂可以提高材料的导电性能,且掺杂浓度增大时,体系依旧保持着透明性并且在红外光和可见光区对光子的吸收能力、材料的介电性能都有着显著提高。本文为WS2二维材料相关光电器件的研究提供了理论依据。 相似文献
6.
Nonlinear Dynamics - As a simplified model of structures of many kinds, the Euler Bernoulli beam has proved useful for studying vibration suppression. In order to meet engineering design... 相似文献
7.
Hao Lu Xiaodong Wang Hang Wang Andong Zhang Xinming Zheng Na Yu Zheng Tang Xinjun Xu Yahui Liu Ya-Nan Chen Zhishan Bo 《中国科学:化学(英文版)》2022,65(3):594-601
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs. 相似文献
8.
分子张力作为空间设计的重要组成部分正成为调控有机半导体的重要手段。由于分子内产生的拉伸张力、扭曲/弯曲张力以及空间张力而导致p轨道排布重组和构型构象结构发生变化,最近各种几何与拓扑结构的高张力有机半导体材料相继被报道,这使得高张力有机半导体材料成为有机电子领域研究的焦点。为了进一步梳理分子张力在有机半导体材料中扮演的角色与价值,该综述从分子张力的类型、实验与理论量化以及可视化出发,总结了高张力共轭芳烃的分子设计策略、与其光电性能分子张力之间的关系,以及这类新兴材料在光电领域的应用。最后,对高张力共轭芳烃的研究前景进行了展望,阐述了该类材料所面临的机遇与挑战。 相似文献
9.
Nonlinear Dynamics - In this paper, a (2+1)-dimensional Caudrey–Dodd–Gibbon–Kotera–Sawada system is investigated in fluid mechanics via the symbolic computation. With the... 相似文献
10.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献