全文获取类型
收费全文 | 32636篇 |
免费 | 447篇 |
国内免费 | 555篇 |
专业分类
化学 | 11493篇 |
晶体学 | 279篇 |
力学 | 1457篇 |
综合类 | 16篇 |
数学 | 9234篇 |
物理学 | 8689篇 |
无线电 | 2470篇 |
出版年
2023年 | 68篇 |
2022年 | 76篇 |
2021年 | 121篇 |
2020年 | 137篇 |
2019年 | 107篇 |
2018年 | 1287篇 |
2017年 | 1573篇 |
2016年 | 863篇 |
2015年 | 741篇 |
2014年 | 628篇 |
2013年 | 872篇 |
2012年 | 3421篇 |
2011年 | 2600篇 |
2010年 | 1934篇 |
2009年 | 1697篇 |
2008年 | 753篇 |
2007年 | 748篇 |
2006年 | 726篇 |
2005年 | 4900篇 |
2004年 | 4012篇 |
2003年 | 2360篇 |
2002年 | 556篇 |
2001年 | 377篇 |
2000年 | 159篇 |
1999年 | 222篇 |
1998年 | 156篇 |
1997年 | 110篇 |
1996年 | 94篇 |
1995年 | 89篇 |
1994年 | 86篇 |
1993年 | 55篇 |
1992年 | 198篇 |
1991年 | 194篇 |
1990年 | 184篇 |
1989年 | 141篇 |
1988年 | 132篇 |
1987年 | 103篇 |
1986年 | 86篇 |
1985年 | 78篇 |
1984年 | 62篇 |
1983年 | 53篇 |
1982年 | 46篇 |
1979年 | 45篇 |
1976年 | 88篇 |
1975年 | 48篇 |
1974年 | 48篇 |
1973年 | 61篇 |
1972年 | 47篇 |
1970年 | 48篇 |
1968年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
A Collaboration M. Makek P. Achenbach C. Ayerbe Gayoso C. Barbieri J. C. Bernauer R. B?hm D. Bosnar A. Denig M. O. Distler I. Fri??i? C. Giusti H. Merkel U. Müller L. Nungesser J. Pochodzalla S. Sanches Majos B. S. Schlimme M. Schwamb Th. Walcher 《The European Physical Journal A - Hadrons and Nuclei》2016,52(9):298
972.
Hua Pang 《Telematics and Informatics》2018,35(8):2147-2156
Although WeChat has recently spawned significant resolutions in technology-mediated social contact and interpersonal communication, the research regarding the social and psychological impacts of the newly emerging technology is relatively few. The primary purpose of the current empirical research is to unearth whether and how WeChat interaction could enhance overseas students’ sense of subjective well-being by concentrating on social integration, bridging relationships, and bonding relationships. Using web-based data of 228 Chinese subjects, the obtained results reveal that the time spent on WeChat significantly and directly impacts users’ subjective well-being. Additionally, the findings demonstrate that social integration, bridging relationships, bonding relationships are all significant predictors to subjective well-being. Furthermore, the perceptions of social integration and social capital could play the crucial mediating roles in the connection between WeChat use and the dependent variable of subjective well-being. Therefore, these outcomes may shed light on a more nuanced comprehending of the influence of the new social media interaction on sojourner’s social adaption and overall life quality in the digital age. 相似文献
973.
Jing He Mohan Yu Maofu Pang Yanqing Fan Zhe Lian Dr. Ying Wang Prof. Wenguang Wang Prof. Yajun Liu Prof. Hua Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(13):e202103832
Structural designs combining cycloparaphenylenes (CPPs) backbone with planar chiral [2.2]paracyclophane ([2.2]PCP) lead to optical-active chiral macrocycles with intriguing properties. X-ray crystal analysis revealed aesthetic necklace-shaped structures and size-dependent packages with long-range channels. The macrocycles exhibit unique photophysical properties with high fluorescence quantum yield of up to 82 %, and the fluorescent color varies with ring size. In addition, size-dependent chiroptical properties with moderately large CPL dissymmetry factor of 10−3 and CPL brightness in the range of 30–40 M−1 cm−1 were observed. 相似文献
974.
Yue Liu Mingxin Lv Lu Li Hailong Yu Qiong Wu Jinhui Pang Yuxiang Liu Congxia Xie Shitao Yu Shiwei Liu 《应用有机金属化学》2019,33(4)
An amino‐functionalized silica‐coated Fe3O4 nanocomposite (Fe3O4@SiO2/APTS) was synthesized. The Fe3O4@SiO2 microspheres possessed a well‐defined core–shell structure, uniform sizes and high magnetization. An immobilized ruthenium nanoparticle catalyst (Fe3O4@SiO2/APTS/Ru) was obtained after coordination and reduction of Ru3+ on the Fe3O4@SiO2/APTS nanocomposite. The Ru nanoparticles were not only ultra‐small with nearly monodisperse sizes but also had strong affinity with the surface of Fe3O4@SiO2/APTS. The obtained catalyst exhibited excellent catalytic performance for the hydrogenation of a variety of aromatic nitro compounds, even at room temperature. Moreover, Fe3O4@SiO2/APTS/Ru was easily recovered using a magnetic field and directly reused for at least five cycles without significant loss of its activity. 相似文献
975.
Acta Mathematicae Applicatae Sinica, English Series - For the variational inequality with symmetric cone constraints problem, we consider using the inexact modified Newton method to efficiently... 相似文献
976.
Zhang Ning Zhang Bin Pang Yong Yang Hong-Sheng Zong Lu Duan Yong-Xin Zhang Jian-Ming 《高分子科学》2022,40(4):373-383
Chinese Journal of Polymer Science - Macromolecule nanocrystal network and strong interfacial interaction are always beneficial to enhance the mechanical property of polymer-based nanocomposites.... 相似文献
977.
We explore two- and three-state Markov models driven out of thermal equilibrium by non-potential forces, to demonstrate basic properties of the steady heat capacity based on the concept of quasistatic excess heat. It is shown that large enough driving forces can make the steady heat capacity negative. For both the low- and high-temperature regimes we propose an approximative thermodynamic scheme in terms of “dynamically renormalized” effective energy levels. 相似文献
978.
979.
Patrick Homenya Markus Messerschmidt Muhammad Nawaz Tahir Victor Martinez Yajun Cheng Jochen S. Gutmann Michael Klein Stefan Jung Morris Wolff Reza Saadat Driss Nariaki Roman Bo?a G?star Klingelh?fer Wolfgang Tremel Franz Renz 《Hyperfine Interactions》2012,205(1-3):63-67
The nonanuclear coordination compound [MoIV{(CN)FeIII(3-methyl-saldptn)}8]Cl4 exhibits multiple spin transitions (3-methyl-saldptn = N,N′-bis(3′′-methyl-2′′-hydroxy-benzyliden)-1,7-diamino-4-azaheptane). This spin crossover cluster is bound via a self-assembled monolayer onto a two dimensional array gold surface. M?ssbauer spectroscopy indicates that the thermally and optically induced spin crossover of the compound is maintained. Thereby, the foundation for its potential practical application (e.g. in the field of information storage) was laid. 相似文献
980.
This paper studies dynamic stochastic optimization problems parameterized by a random variable. Such problems arise in many applications in operations research and mathematical finance. We give sufficient conditions for the existence of solutions and the absence of a duality gap. Our proof uses extended dynamic programming equations, whose validity is established under new relaxed conditions that generalize certain no-arbitrage conditions from mathematical finance. 相似文献