全文获取类型
收费全文 | 4045篇 |
免费 | 119篇 |
国内免费 | 13篇 |
专业分类
化学 | 3056篇 |
晶体学 | 29篇 |
力学 | 68篇 |
数学 | 162篇 |
物理学 | 862篇 |
出版年
2022年 | 24篇 |
2021年 | 37篇 |
2020年 | 39篇 |
2019年 | 49篇 |
2018年 | 31篇 |
2017年 | 34篇 |
2016年 | 64篇 |
2015年 | 78篇 |
2014年 | 73篇 |
2013年 | 188篇 |
2012年 | 169篇 |
2011年 | 185篇 |
2010年 | 97篇 |
2009年 | 97篇 |
2008年 | 183篇 |
2007年 | 175篇 |
2006年 | 207篇 |
2005年 | 225篇 |
2004年 | 208篇 |
2003年 | 168篇 |
2002年 | 209篇 |
2001年 | 136篇 |
2000年 | 104篇 |
1999年 | 73篇 |
1998年 | 49篇 |
1997年 | 43篇 |
1996年 | 63篇 |
1995年 | 55篇 |
1994年 | 59篇 |
1993年 | 55篇 |
1992年 | 77篇 |
1991年 | 63篇 |
1990年 | 54篇 |
1989年 | 49篇 |
1988年 | 44篇 |
1987年 | 37篇 |
1986年 | 48篇 |
1985年 | 70篇 |
1984年 | 61篇 |
1983年 | 24篇 |
1982年 | 48篇 |
1981年 | 30篇 |
1980年 | 30篇 |
1979年 | 46篇 |
1978年 | 38篇 |
1977年 | 44篇 |
1976年 | 30篇 |
1975年 | 30篇 |
1974年 | 30篇 |
1973年 | 34篇 |
排序方式: 共有4177条查询结果,搜索用时 15 毫秒
991.
Masahiko Suzuki Yukio Yamamoto Masahiro Irie Koichiro Hayashi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1607-1622
Photopolymerization of styrene in the presence of pyromellitic dianhydride, an electron acceptor which forms a charge-transfer complex with the monomer, was studied. Polymerization was initiated by illumination with a light of wavelength longer than 350 nm, where only the charge-transfer absorption band exists. It was found that the reaction involves cationic and radical polymerizations and that the reaction course strongly depends on polarity of the system. It was also suggested by the dependence of the rate of polymerization on light intensity and temperature that the cationic polymerization consists of free ion and ion-pair polymerizations. These results were compared with those of the photoinduced cationic polymerization of α-methylstyrene, which has previously been studied. 相似文献
992.
993.
994.
995.
Yuichi Yamamoto 《International Journal of Game Theory》2010,39(3):431-443
This paper presents an example where the set of subgame-perfect equilibrium payoffs of the infinitely repeated game without
public randomization is not convex, no matter how large the discount factor is. Also, the set of pure-strategy equilibrium
payoffs is not monotonic with respect to the discount factor in this example. These results are in sharp contrast to the fact
that the equilibrium payoff set is convex and monotonic if public randomization is available. 相似文献
996.
Y. Miyamoto T. Yamamoto K. Kinoshita S. Koyama Y. Takei H. Nanto Y. Shimotsuma M. Sakakura K. Miura K. Hirao 《Radiation measurements》2010,45(3-6):546-549
The objective of this study is to investigate the emission mechanism of radiophotoluminescence (RPL) in the Ag+-doped phosphate glass (glass dosimeter), which is now used as individual radiation dosimeter, because the emission mechanism of RPL in glass dosimeter was not fully understood. Optical properties such as optical absorption spectrum, RPL spectrum and change of RPL spectrum as a function of X-ray irradiation dose were measured for commercially available glass dosimeter. In this study, we discuss the emission mechanism of two RPL peaks at 460 nm and 560 nm, based on the fact that electrons and holes produced by X-ray irradiation are trapped at Ag+ ions to produce Ag0 and Ag2+ ions, respectively, when the Ag+-doped phosphate glass is exposed to X-ray. We would like to propose the emission mechanism of RPL peaks at 460 nm and 560 nm, concerning with Ag2+ and Ag0 ions. 相似文献
997.
A novel water-holding adsorbent bonded with a zwitterionic polymer, diallylamine–maleic acid copolymer, was developed. With this adsorbent, hydrophilic solutes are partitioned by a hydration layer that forms on the zwitterions, as a main separating force. When the adsorbent was used to separate saccharides by normal-phase partition chromatography, the saccharides eluted in the order, mono-, di- and trisaccharide. The elution profile for mono- and di-saccharides was similar but not identical to that on anion exchange columns. This indicated that the adsorbent exhibited a complex retention behavior by the existence of both anion and cation exchange moieties in the functional polymer. Selecting Na+ as a counter-ion of the maleate moiety enhanced the retention of saccharide. When used in an high performance liquid chromatography (HPLC) system with gradient elution, the adsorbent enabled the simultaneous analysis of mono-, di- and oligosaccharides. 相似文献
998.
Synthesis of Three‐Dimensional Butterfly Slit‐Cyclobisazaanthracenes and Hydrazinobisanthenes through One‐Step Cyclodimerization and Their Properties 下载免费PDF全文
Dr. Koji Yamamoto Prof. Dr. Shuhei Higashibayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):663-671
New three‐dimensional (3D) π‐conjugated molecules, butterfly‐shaped slit‐cyclobisazaanthracenes, were synthesized in high yields by Ni‐mediated one‐step cyclodimerization of dibromoazaanthracenes with a dimethylacridine, phenothiazine, or acridone skeleton. The 3D slit butterfly shape was formed by folded azaanthracene skeletons. Closure of the slit via N?N bond formation afforded hydrazinobisanthenes with an embedded hydrazine structure in a bisanthene skeleton, which exhibited a 3D butterfly or a 2D plane structure depending on the type of heterocycle used. Extensive study of the stereoselective chemical reactivity of the butterfly shape, X‐ray analysis, DFT calculations, electrochemical/chemical oxidations, and photophysical measurements revealed that the properties of these materials included stereoselective oxidation, a rigid or flexible butterfly shape, dynamic conformational behavior, unique crystal‐packing structures, excellent electron donation with low oxidation potential, a radical cation, a long absorption wavelength, and fluorescence property. 相似文献
999.
1000.
We report the highly regioselective cyclotrimerization of the 1-perfluoroalkylenynes in the presence of Ni(PPh3)4. The substituent effects on the reactivity of the enynes were investigated. We also succeeded in the nickel-catalyzed cocyclization of the 1-perfluoroalkylenynes with (trimethylsilyl)-acetylene. The possible structures of the intermediates of the cyclotrimerization and the reasons for the observed high regioselectivity were discussed. 相似文献