全文获取类型
收费全文 | 70165篇 |
免费 | 11553篇 |
国内免费 | 7698篇 |
专业分类
化学 | 49498篇 |
晶体学 | 862篇 |
力学 | 4191篇 |
综合类 | 513篇 |
数学 | 8103篇 |
物理学 | 26249篇 |
出版年
2024年 | 58篇 |
2023年 | 1401篇 |
2022年 | 1609篇 |
2021年 | 2368篇 |
2020年 | 2935篇 |
2019年 | 2770篇 |
2018年 | 2373篇 |
2017年 | 2334篇 |
2016年 | 3363篇 |
2015年 | 3394篇 |
2014年 | 3971篇 |
2013年 | 5208篇 |
2012年 | 6374篇 |
2011年 | 6549篇 |
2010年 | 4474篇 |
2009年 | 4256篇 |
2008年 | 4650篇 |
2007年 | 4168篇 |
2006年 | 3752篇 |
2005年 | 3146篇 |
2004年 | 2440篇 |
2003年 | 1966篇 |
2002年 | 1753篇 |
2001年 | 1360篇 |
2000年 | 1219篇 |
1999年 | 1428篇 |
1998年 | 1182篇 |
1997年 | 1138篇 |
1996年 | 1172篇 |
1995年 | 1036篇 |
1994年 | 945篇 |
1993年 | 759篇 |
1992年 | 653篇 |
1991年 | 610篇 |
1990年 | 471篇 |
1989年 | 358篇 |
1988年 | 284篇 |
1987年 | 254篇 |
1986年 | 248篇 |
1985年 | 220篇 |
1984年 | 142篇 |
1983年 | 137篇 |
1982年 | 88篇 |
1981年 | 65篇 |
1980年 | 59篇 |
1979年 | 34篇 |
1977年 | 26篇 |
1976年 | 25篇 |
1975年 | 28篇 |
1972年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
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
22.
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the... 相似文献
23.
Yang Chunxiao Taralova Ina El Assad Safwan Loiseau Jean-Jacques 《Nonlinear dynamics》2022,109(3):2103-2127
Nonlinear Dynamics - Nonlinear dynamic systems and chaotic systems have been quite exhaustively researched in the domain of cryptography. However, the possibility of using fractional chaotic... 相似文献
24.
Sicheng Yang Dr. Jiaoyu Ren Prof. Hong Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202103867
The drug delivery system based on nano/micromotors has become a research hot spot in recent years. However, naked micromotors may be ruptured or passivated under the complex biological environment, which will result in the leakage of drugs in advance or limited self-propulsion performance. Herein, an injectable micromotor@hydrogel drug delivery system to protect micromotors from the external environment is proposed. The micromotors were prepared through layer-by-layer assembly technology. The asymmetric decomposition of hydrogen peroxide catalyzed by the locally distributed platinum nanoparticles enabled efficient propulsion of the micromotors in low concentration of hydrogen peroxide. In order to protect micromotors, they were loaded into the Schiff base hydrogel. The micromotor@hydrogel system can be injected directly into the lesion to release micromotors in response to the environment, reducing external influence on micromotors and improving the sustained-release effect. Erythromycin (Ery) loaded into the micromotors and the micromotor@hydrogel system demonstrated excellent antibacterial effect. Micromotors released from the hydrogel underwent enhanced diffusion in the surroundings of bacteria without addition of exogenous hydrogen peroxide, which was manifested by their appearance in edge of the inhibition zone. The proposed micromotor@hydrogel drug delivery system offers a new strategy for the treatment of bacterial infections. 相似文献
25.
Zhang Mingjie Song Yang Abdelkefi Abdessattar Yu Haiyan Wang Junlei 《Nonlinear dynamics》2022,108(3):1867-1884
Nonlinear Dynamics - Vortex-induced vibration (VIV) systems with stiffness nonlinearity have received increasing attention because the stiffness nonlinearity can broaden the effective flow velocity... 相似文献
26.
Nonlinear Dynamics - In this paper, the high-order coupled variable coefficient nonlinear Schrödinger equations is studied. The double-hump soliton solutions for the equations are obtained... 相似文献
27.
Yao Wen Chen Yangfan Li Jiangling Yang Jian Ren Shan Liu Weizao Liu Qingcai 《Research on Chemical Intermediates》2022,48(5):1813-1829
Research on Chemical Intermediates - Industrial wastewater is becoming a universal environmental problem, wherein toxic organic compounds are important sources of pollution. For the degradation... 相似文献
28.
Yuanbo Gao Tingting Yang Xueli Wang Jizong Chen Yong He 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1610-1623
Two series of novel alternating copolyoxamides (PAnT-alt-n2 and PAn2-alt-62) are synthesized via solution/solid-state polycondensation (SSP). The alternating structures are analyzed carefully with 1H NMR and 13C NMR spectra. The melting behaviors, thermal stabilities, crystal structures and crystallinities are systematically evaluated by DSC, TGA and WAXD. The results reveal that these alternating copolyoxamides possess almost perfect alternating chain structures and have high melting temperature (Tm > 270 °C), high crystallinity (Xc > 32%) and high decomposition temperature (T5 > 405 °C) as well as low saturated water absorption (<3.5 wt%), which suggests that they have high potential as engineering plastic of high heat resistant. 相似文献
29.
Liu Wei Li Kehong Deng Hao Wang Jing Zhao Peng Liao Wei Zhuo Liangang Wei Hongyuan Yang Xia Chen Yue 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(2):747-754
Journal of Radioanalytical and Nuclear Chemistry - There is an urgent need to develop more specific targeted therapies for lung cancer treatment due to the its low survival rate. EGFR is a... 相似文献
30.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献