全文获取类型
收费全文 | 3716篇 |
免费 | 77篇 |
国内免费 | 13篇 |
专业分类
化学 | 2581篇 |
晶体学 | 43篇 |
力学 | 64篇 |
数学 | 181篇 |
物理学 | 937篇 |
出版年
2021年 | 24篇 |
2020年 | 47篇 |
2019年 | 50篇 |
2018年 | 43篇 |
2017年 | 24篇 |
2016年 | 51篇 |
2015年 | 57篇 |
2014年 | 73篇 |
2013年 | 170篇 |
2012年 | 146篇 |
2011年 | 183篇 |
2010年 | 127篇 |
2009年 | 120篇 |
2008年 | 192篇 |
2007年 | 219篇 |
2006年 | 197篇 |
2005年 | 150篇 |
2004年 | 133篇 |
2003年 | 139篇 |
2002年 | 140篇 |
2001年 | 108篇 |
2000年 | 127篇 |
1999年 | 80篇 |
1998年 | 53篇 |
1997年 | 50篇 |
1996年 | 44篇 |
1995年 | 42篇 |
1994年 | 42篇 |
1993年 | 59篇 |
1992年 | 47篇 |
1991年 | 47篇 |
1990年 | 38篇 |
1989年 | 47篇 |
1988年 | 48篇 |
1987年 | 41篇 |
1986年 | 35篇 |
1985年 | 52篇 |
1984年 | 57篇 |
1983年 | 48篇 |
1982年 | 43篇 |
1981年 | 30篇 |
1980年 | 34篇 |
1979年 | 50篇 |
1978年 | 44篇 |
1977年 | 48篇 |
1976年 | 16篇 |
1975年 | 28篇 |
1974年 | 30篇 |
1973年 | 15篇 |
1967年 | 16篇 |
排序方式: 共有3806条查询结果,搜索用时 296 毫秒
21.
The educational system has gradually shifted from a face-to-face to an e-learning system, which has become prevalent in advanced countries with the advance of information technology, and connection of global networks. Accordingly, a growing demand is emerging for more reliable individual certification with technical precision in order to measure and record learning achievements and credentials of participants. The present system has a limit in terms of registration capacity, therefore, its accuracy has often been questioned. Against this background, an individual certification system is proposed particularly for access control in e-learning. Under our proposed system, a compact optical correlator for facial recognition is employed. This correlator was previously tested for of biometrics authentication accuracy and proved highly reliable, having recorded remarkably low error rates (below 1%). The recorded error rate is sufficiently robust that the system itself can be regarded as a valid and practical viable attestation system. 相似文献
22.
The study reported in this paper investigated perceptions concerning connections between mathematics and science held by university/college instructors who participated in the Maryland Collaborative for Teacher Preparation (MCTP), an NSF-funded program aimed at developing special middle-level mathematics and science teachers. Specifically, we asked (a) “What are the perceptions of MCTP instructors about the ‘other’ discipline?” (b) “What are the perceptions of MCTP instructors about the connections between mathematics and science?” and (c) “What are some barriers perceived by MCTP instructors in implementing mathematics and science courses that emphasize connections?” The findings suggest that the benefits of emphasizing mathematics and science connections perceived by MCTP instructors were similar to the benefits reported by school teachers. The barriers reported were also similar. The participation in the project appeared to have encouraged MCTP instructors to grapple with some fundamental questions, like “What should be the nature of mathematics and science connections?” and “What is the nature of mathematics/science in relationship to the other discipline?” 相似文献
23.
24.
Miyuki Harada Yutaka Watanabe Yuko Tanaka Mitsukazu Ochi 《Journal of Polymer Science.Polymer Physics》2006,44(17):2486-2494
A mesogenic‐type curing agent was synthesized to introduce a mesogenic group not only into epoxy resin backbones but also into the crosslink units. In the mesogenic curing agent system, the domain size became larger, and the network arrangement in each domain existed to a greater extent than that in a system cured with the ordinary diamine curing system according to the evidence from polarized optical micrographs and polarized Fourier transform infrared mapping measurements. Moreover, the fracture toughness of the system was considerably improved. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2486–2494, 2006 相似文献
25.
Kazuhiko Nakano Toshihiro Nakamura Izumi Nakai Akira Kawase Makoto Imai Mikio Hasegawa Yohichi Ishibashi Isamu Inamoto Kazuhuyu Sudou Masaru Kozaki Akira Tsuruta Akihiro Ono Kazutoshi Kakita Mamoru Sakata 《Analytical sciences》2006,22(9):1265-1268
The Japan Society for Analytical Chemistry has developed some new plastic certified reference materials (CRMs) for the analysis of mercury in polyester disks using XRF analysis. These CRMs (named as JSAC 0621-0625) were prepared by casting polyesters including a toluene solution of organometallic compounds as a standard. Concentrations of the five levels of mercury ranged from 0 to 250 mg/kg. Homogeneity tests of prepared disks had shown excellent results. Interlaboratory comparison study for the certification was performed by 15 laboratory participants. The z-scores in robust statistical method was applied for the evaluation of outliers. The certified values were assigned after discarding outliers. The uncertainties of certified values were determined as the confidence levels of 95%. 相似文献
26.
N Fujii T Watanabe A Otaka K Bessho I Yamamoto T Noda H Yajima 《Chemical & pharmaceutical bulletin》1987,35(12):4769-4776
27.
We compute the cyclic homology of the coordinate ring A(SLq(2)) of the quantum algebraic group SL
q
(2). We observe a degeneration of the noncommutative de Rham complex. The results are also verified from the point of view of Connes' noncommutative differential geometry. 相似文献
28.
29.
30.