全文获取类型
收费全文 | 188860篇 |
免费 | 1050篇 |
国内免费 | 386篇 |
专业分类
化学 | 64714篇 |
晶体学 | 2618篇 |
力学 | 10415篇 |
综合类 | 8篇 |
数学 | 30024篇 |
物理学 | 59167篇 |
无线电 | 23350篇 |
出版年
2022年 | 526篇 |
2021年 | 533篇 |
2020年 | 499篇 |
2019年 | 495篇 |
2018年 | 11013篇 |
2017年 | 11928篇 |
2016年 | 5704篇 |
2015年 | 1695篇 |
2014年 | 1296篇 |
2013年 | 2888篇 |
2012年 | 7420篇 |
2011年 | 17412篇 |
2010年 | 11027篇 |
2009年 | 11178篇 |
2008年 | 15299篇 |
2007年 | 19494篇 |
2006年 | 3649篇 |
2005年 | 11010篇 |
2004年 | 6900篇 |
2003年 | 6483篇 |
2002年 | 3973篇 |
2001年 | 3865篇 |
2000年 | 3100篇 |
1999年 | 2108篇 |
1998年 | 1631篇 |
1997年 | 1619篇 |
1996年 | 1579篇 |
1995年 | 1385篇 |
1994年 | 1285篇 |
1993年 | 1256篇 |
1992年 | 1567篇 |
1991年 | 1572篇 |
1990年 | 1445篇 |
1989年 | 1239篇 |
1988年 | 1190篇 |
1987年 | 1083篇 |
1986年 | 926篇 |
1985年 | 1182篇 |
1984年 | 1143篇 |
1983年 | 804篇 |
1982年 | 808篇 |
1981年 | 764篇 |
1980年 | 691篇 |
1979年 | 828篇 |
1978年 | 839篇 |
1977年 | 753篇 |
1976年 | 689篇 |
1975年 | 593篇 |
1974年 | 630篇 |
1973年 | 585篇 |
排序方式: 共有10000条查询结果,搜索用时 875 毫秒
41.
42.
43.
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices.... 相似文献
44.
Sh. M. Khaliullin V. D. Zhuravlev V. G. Bamburov L. V. Ermakova 《Physics of Atomic Nuclei》2015,78(12):1382-1388
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics. 相似文献
45.
Dr. Nozomi Mihara Dr. Yasuyuki Yamada Dr. Hikaru Takaya Prof. Yasutaka Kitagawa Dr. Kazunobu Igawa Prof. Katsuhiko Tomooka Prof. Hiroshi Fujii Prof. Kentaro Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3369-3375
Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 3 5+, which is connected through a fourfold rotaxane, was prepared. Heterodimer 3 5+ catalyzed ethane oxidation in the presence of H2O2 at a relatively low temperature. The site-selective complexation of 3 5+ with an additional anionic porphyrin (TPPS4−) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 3 5+ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS4− to 3 5+ enhanced the catalytic activity. 相似文献
46.
47.
48.
Locke Davenport Huyer Serena Mandla Yufeng Wang Scott B. Campbell Bess Yee Christian Euler Benjamin F. Lai A. Dawn Bannerman Dawn S. Y. Lin Miles Montgomery Kayla Nemr Timothy Bender Slava Epelman Radhakrishnan Mahadevan Milica Radisic 《Advanced functional materials》2021,31(6):2003341
Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA. 相似文献
49.
Frequency Insertion Strategy for Channel Assignment Problem 总被引:1,自引:0,他引:1
This paper presents a new heuristic method for quickly finding a good feasible solution to the channel assignment problem
(CAP). Like many other greedy-type heuristics for CAP, the proposed method also assigns a frequency to a call, one at a time.
Hence, the method requires computational time that increases only linear to the number of calls. However, what distinguishes
the method from others is that it starts with a narrow enough frequency band so as to provoke violations of constraints that
we need to comply with in order to avoid radio interference. Each violation is then resolved by inserting frequencies at the
most appropriate positions so that the band of frequencies expands minimally. An extensive computational experiment using
a set of randomly generated problems as well as the Philadelphia benchmark instances shows that the proposed method perform
statistically better than existing methods of its kind and even yields optimum solutions to most of Philadelphia benchmark
instances among which two cases are reported for the first time ever, in this paper.
Won-Young Shin was born in Busan, Korea in 1978. He received B.S. in industrial engineering from Pohang University of Science and Technology
(POSTECH) in 2001 and M.S in operation research and applied statistics from POSTECH in 2003. Since 2003 he has been a researcher
of Agency for Defense Development (ADD) in Korea. He is interested in optimization of communication system and applied statistics.
Soo Y. Chang is an associate professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH),
Pohang, Korea. He teaches linear programming, discrete optimization, network flows and operations research courses. His research
interests include mathematical programming and scheduling. He has published in several journals including Discrete Applied
Mathematics, Computers and Mathematics with Application, IIE Transactions, International Journal of Production Research, and
so on. He is a member of Korean IIE, and ORMSS.
Jaewook Lee is an assistant professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH),
Pohang, Korea. He received the B.S. degree in mathematics with honors from Seoul National University, and the Ph.D. degree
from Cornell University in applied mathematics in 1993 and 1999, respectively. He is currently an assistant professor in the
department of industrial engineering at the Pohang University of Science and Technology (POSTECH). His research interests
include nonlinear systems, neural networks, nonlinear optimization, and their applications to data mining and financial engineering.
Chi-Hyuck Jun was born in Seoul, Korea in 1954. He received B.S. in mineral and petroleum engineering from Seoul National University in
1977, M.S. in industrial engineering from Korea Advanced Institute of Science and Technology in 1979 and Ph.D. in operations
research from University of California, Berkeley, in 1986. Since 1987 he has been with the department of industrial engineering,
Pohang University of Science and Technology (POSTECH) and he is now a professor and the department head. He is interested
in performance analysis of communication and production systems. He has published in several journals including IIE Transactions,
IEEE Transactions, Queueing Systems and Chemometrics and Intelligent Laboratory Systems. He is a member of IEEE, INFORMS and
ASQ. 相似文献
50.
Co-browsing is an activity in which a group of users navigate their way through of a set of Web pages together for a shared
purpose. Effective co-browsing among users with different device capabilities requires a shared understanding of those Web
pages. This paper demonstrates the concept of shared viewpoints (SVPs), and personal viewpoints (PVPs), for co-browsing, before
detailing a framework for implementing these concepts. Finally, the effectiveness of the framework is presented through a
perceptual experiment. 相似文献