全文获取类型
收费全文 | 1313篇 |
免费 | 27篇 |
国内免费 | 11篇 |
专业分类
化学 | 1038篇 |
晶体学 | 11篇 |
力学 | 8篇 |
数学 | 62篇 |
物理学 | 232篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2016年 | 19篇 |
2015年 | 14篇 |
2014年 | 35篇 |
2013年 | 59篇 |
2012年 | 65篇 |
2011年 | 67篇 |
2010年 | 46篇 |
2009年 | 34篇 |
2008年 | 61篇 |
2007年 | 68篇 |
2006年 | 84篇 |
2005年 | 60篇 |
2004年 | 54篇 |
2003年 | 61篇 |
2002年 | 58篇 |
2001年 | 27篇 |
2000年 | 31篇 |
1999年 | 22篇 |
1998年 | 16篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 23篇 |
1994年 | 24篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 24篇 |
1983年 | 8篇 |
1982年 | 22篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 24篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 17篇 |
1973年 | 19篇 |
1971年 | 5篇 |
1965年 | 5篇 |
排序方式: 共有1351条查询结果,搜索用时 15 毫秒
141.
Shiro Ishikawa 《Fuzzy Sets and Systems》1998,100(1-3):291-300
Our main interest in this paper is to translate from “natural language” into “system theoretical language”. This is of course important since a statement in system theory can be analyzed mathematically or computationally. We assume that, in order to obtain a good translation, “system theoretical language” should have great power of expression. Thus we first propose a new frame of system theory, which includes the concepts of “measurement” as well as “state equation”. And we show that a certain statement in usual conversation, i.e., fuzzy modus ponens with the word “very”, can be translated into a statement in the new frame of system theory. Though our result is merely one example of the translation from “natural language” into “system theoretical language”, we believe that our method is fairly general. 相似文献
142.
143.
To clarify the role of formant frequency in the perception of pitch in whispering, we conducted a preliminary experiment to determine (1.) whether speakers change their pitch during whispering; (2.) whether listeners can perceive differences in pitch; and (3.) what the acoustical features are when speakers change their pitch. The listening test of whispered Japanese speech demonstrates that one can determine the perceived pitch of vowel /a/ as ordinary, high, or low. Acoustical analysis revealed that the perception of pitch corresponds to some formant frequencies. Further data with synthesized whispered voice are necessary to confirm the importance of the formant frequencies in detail for perceived pitch of whispered vowels. 相似文献
144.
145.
146.
Shiro Kubuki Norifumi Kawakami Takamitsu Kamikawa Masayuki Fukagawa Toshiharu Nishizumi Tetsuaki Nishida Zoltán Homonnay Ernő Kuzmann 《Hyperfine Interactions》2005,166(1-4):429-436
A relationship between the structure and water purifying ability of waste glass prepared from household garbage and Fe2O3 was examined by 57Fe-Mössbauer and induced coupled plasma (ICP) measurements. From the Debye temperature of waste glass, FeII proved to be loosely bound in the glass network as a network modifier. Dissolution amount of FeIII into artificial drain can be controlled from 0.14 to 0.35 mg/l by changing the Fe2O3 content. It proved that chemical oxygen demand (COD) decreases in proportion to the content of FeIII, indicating that iron causes decomposition of organic and phosphorus compounds. 相似文献
147.
Shiro Kobayashi Ryosuke Itoh Hidekazu Morii Shun-Ichi Fujikawa Shunsaku Kimura Masashi Ohmae 《Journal of polymer science. Part A, Polymer chemistry》2003,41(22):3541-3548
Hyaluronic acid and chondroitin were successfully synthesized as representative molecules of glucosaminoglycans and galactosaminoglycans found in a glycosaminoglycan family via enzymatic polymerization catalyzed by testicular hyaluronidases. A newly designed N-acetylhyalobiuronate oxazoline derivative with a β-D -glucuronyl-(1→3)-N-acetyl-D -glucosamine disaccharide structure served as a transition-state analogue substrate monomer for the enzyme, giving rise to artificial hyaluronic acid in 52% yields with a number-average molecular weight of 1.35 × 104 through ring-opening polyaddition in a perfect regioselective and stereoselective manner. A novel N-acetylchondrosine oxazoline derivative with a β-D -glucuronyl-(1→3)-N-acetyl-D -galactosamine disaccharide structure also acted as a transition-state analogue substrate monomer for the enzyme, yielding artificial chondroitin in 35% yields with a number-average molecular weight of 2.5 × 103. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3541–3548, 2003 相似文献
148.
1-Deoxy-azasugars are efficiently prepared from sugar-lactones using a stereoinversion process and they are applied to the synthesis of a natural product. 相似文献
149.
Preparation and characterization of single-phase SiC nanotubes and C-SiC coaxial nanotubes 总被引:2,自引:0,他引:2
Tomitsugu Taguchi Naoki Igawa Hiroyuki Yamamoto Shin-ichi Shamoto Shiro Jitsukawa 《Physica E: Low-dimensional Systems and Nanostructures》2005,28(4):431-438
Preparation conditions of single-phase SiC nanotubes and C-SiC coaxial nanotubes were investigated. The characterization of single-phase SiC nanotubes and C-SiC coaxial nanotubes were carried out. The SiC nanowires, which were made of the catenated SiC grains of 50–200 nm in diameter, were obtained in carbon nanotubes reacted at 1450 °C. The only C-SiC coaxial nanotubes were formed at 1300 °C. A few single-phase SiC nantoubes were synthesized at 1200 °C for 100 h. More than half number of nanotubes reacted at 1200 °C for 100 h were altered to single-phase SiC nantoubes by heat treatment of 600 °C for 1 h in air since the remained carbon was removed. The energy dispersive X-ray spectroscopy analysis revealed that the atomic ratio of Si to C in single-phase SiC nanotubes was almost 1; these single-phase SiC nanotubes consisted of near-stoichiometric SiC grains. 相似文献
150.