全文获取类型
收费全文 | 24817篇 |
免费 | 3011篇 |
国内免费 | 2303篇 |
专业分类
化学 | 12404篇 |
晶体学 | 186篇 |
力学 | 1170篇 |
综合类 | 135篇 |
数学 | 2023篇 |
物理学 | 5692篇 |
综合类 | 8521篇 |
出版年
2024年 | 80篇 |
2023年 | 404篇 |
2022年 | 618篇 |
2021年 | 707篇 |
2020年 | 738篇 |
2019年 | 691篇 |
2018年 | 585篇 |
2017年 | 628篇 |
2016年 | 861篇 |
2015年 | 946篇 |
2014年 | 1222篇 |
2013年 | 1458篇 |
2012年 | 1821篇 |
2011年 | 1836篇 |
2010年 | 1349篇 |
2009年 | 1287篇 |
2008年 | 1488篇 |
2007年 | 1377篇 |
2006年 | 1283篇 |
2005年 | 1097篇 |
2004年 | 845篇 |
2003年 | 826篇 |
2002年 | 888篇 |
2001年 | 810篇 |
2000年 | 627篇 |
1999年 | 713篇 |
1998年 | 583篇 |
1997年 | 570篇 |
1996年 | 559篇 |
1995年 | 426篇 |
1994年 | 401篇 |
1993年 | 360篇 |
1992年 | 321篇 |
1991年 | 314篇 |
1990年 | 261篇 |
1989年 | 233篇 |
1988年 | 172篇 |
1987年 | 120篇 |
1986年 | 111篇 |
1985年 | 76篇 |
1984年 | 57篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1980年 | 30篇 |
1978年 | 24篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1974年 | 21篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Lu Yuchan He Qiao Peng Qiao Chen Wenhai Cheng Qunpeng Song Guangsen Fan Guozhi 《Cellulose (London, England)》2021,28(13):8343-8354
Cellulose - The coproduction of 5-hydroxymethylfurfural (5-HMF) and furfural (FUR) via the direct hydrolysis of holocellulose analogue composed of cellulose and hemicellulose was investigated. The... 相似文献
993.
994.
995.
We present some necessary and sufficient conditions for positive semi-compact operators being L-weakly compact and M-weakly
compact respectively. 相似文献
996.
Cheng Wang Yuxin Leng Chuang Li Baozhen Zhao Zhizhan Xu 《Optics & Laser Technology》2010,42(4):657-661
A decentered grating stretcher for chirped pulse amplification systems is analyzed with oblique meridional ray tracing. Several formulae and conclusions are developed to design and optimize the stretcher. On basis of an analytical phase expression with an explicit significance, the expressions of the second-, third- and approximate fourth-order phases at the central wavelength are presented with only independent variables. These simplify the parameter design for this kind of stretcher and the phase compensation design of the whole amplifier system, which has been demonstrated with a practical example. 相似文献
997.
D. Z. Li X. D. Xu S. S. Cheng D. H. Zhou F. Wu Z. W. Zhao C. T. Xia J. Xu J. Zhang H. M. Zhu X. Y. Chen 《Applied physics. B, Lasers and optics》2010,101(1-2):199-205
Nd:CaYAlO4 single crystal has been grown by the Czochralski technique. The cell parameters were analyzed with X-ray diffraction (XRD). The polarized absorption spectra, the polarized fluorescence spectra, and the fluorescence decay curve of the crystal were measured at room temperature. The spectroscopic parameters were determined by Judd–Ofelt theory and Fuchtbauer–Ladenburg formula. The effective intensity parameters Ω 2, Ω 4, and Ω 6 were obtained to be 2.19, 8.16, and 8.57×10?20 cm2, respectively. The calculated radiative probabilities, branching ratios, and radiative lifetime were also evaluated for the 4F3/2 excited state using the calculated intensity parameters. The results indicate Nd:CaYAlO4 has potential as a laser gain medium for ultrashort laser system. 相似文献
998.
Wei Ren Weiren Cheng Guan Wang Ye Liu 《Journal of polymer science. Part A, Polymer chemistry》2017,55(4):632-639
Effective antimicrobial polymers have been attracting more interests because of the low propensity to cause drug-resistant microorganisms. The recent progresses in antimicrobial polymers are updated according to the action approaches, that is, antimicrobial polymers with free mobility or fixed on surfaces, respectively. Free antimicrobial polymers kill pathogens majorly via electrostatic interaction followed by disruption of the cell membranes; strong antimicrobial activity of primary/secondary amines, new chemical units, and peptides without facial amphiphilicity are highlighted; and the dependences on amphiphilicity, topology, and self-assembly profiles are summarized. Antimicrobial polymers fixed on surfaces kill pathogens via interaction with the cell membranes of pathogens via electrostatic or hydrophobic interaction; approaches to antimicrobial surfaces based on covalently grafting, anchoring, and bulk-mixing of polymers are summarized; and new designs of sustainable antimicrobial surfaces and hydrogels are highlighted. Deep biology understanding and development strategies of materials are suggested for the future. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 632–639 相似文献
999.
1000.
Jingshan S. Du Peng‐Cheng Chen Dr. Brian Meckes Dr. Zhuang Xie Jinghan Zhu Yuan Liu Prof. Vinayak P. Dravid Prof. Chad A. Mirkin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(26):7733-7737
Multicomponent nanoparticles can be synthesized with either homogeneous or phase‐segregated architectures depending on the synthesis conditions and elements incorporated. To understand the parameters that determine their structural fate, multicomponent metal‐oxide nanoparticles consisting of combinations of Co, Ni, and Cu were synthesized by using scanning probe block copolymer lithography and characterized using correlated electron microscopy. These studies revealed that the miscibility, ratio of the metallic components, and the synthesis temperature determine the crystal structure and architecture of the nanoparticles. A Co‐Ni‐O system forms a rock salt structure largely owing to the miscibility of CoO and NiO, while Cu‐Ni‐O, which has large miscibility gaps, forms either homogeneous oxides, heterojunctions, or alloys depending on the annealing temperature and composition. Moreover, a higher‐ordered structure, Co‐Ni‐Cu‐O, was found to follow the behavior of lower ordered systems. 相似文献