全文获取类型
收费全文 | 371篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
化学 | 229篇 |
晶体学 | 6篇 |
力学 | 2篇 |
数学 | 21篇 |
物理学 | 125篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 28篇 |
2012年 | 13篇 |
2011年 | 22篇 |
2010年 | 18篇 |
2009年 | 18篇 |
2008年 | 23篇 |
2007年 | 25篇 |
2006年 | 29篇 |
2005年 | 28篇 |
2004年 | 15篇 |
2003年 | 22篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有383条查询结果,搜索用时 15 毫秒
41.
42.
The luminescence induced by heavy charged particle irradiation has been measured. The bi-exciton lines (MT and ML) and the line at 3926 Å were observed. It is concluded that these lines arise from the densely excited region in particle tracks. 相似文献
43.
Motokura K Fujita N Mori K Mizugaki T Ebitani K Kaneda K 《Journal of the American Chemical Society》2005,127(27):9674-9675
A Ti4+-exchanged montmorillonite (Ti4+-mont) and a hydrotalcite (HT) are strong solid Br?nsted acid and base, and these two clay catalysts could be used in a single reactor without neutralization of active sites. Because the Ti4+-mont have active acid site in the narrow interlayers, the base sites of large HT particles show no interaction with the acid sites. A variety of acid and base reactions, such as esterification, acetalization, deacetalization, aldol reaction, Michael reaction, and epoxidation, proceeded using both the Ti4+-mont and the HT in a single reactor. 相似文献
44.
Yutaka T Obara S Ogawa S Nozaki K Ikeda N Ohno T Ishii Y Sakai K Haga MA 《Inorganic chemistry》2005,44(13):4737-4746
A series of novel emissive Ir(III) complexes having the coordination environments of [Ir(N--N--N)2]3+, [Ir(N--N--N)(N--N)Cl]2+, and [Ir(N--N--N)(N--C--N)]2+ with 2,6-bis(1-methyl-benzimidazol-2-yl)pyridine (L1, N--N--N), 1,3-bis(1-methyl-benzimidazol-2-yl)benzene (L2H, N--C--N), 4'-(4-methylphenyl)-2,2':6',2' '-terpyridine (ttpy, N--N--N), and 2,2'-bipyridine (bpy, N--N) have been synthesized and their photophysical and electrochemical properties studied. The Ir(III) complexes exhibited phosphorescent emissions in the 500-600 nm region, with lifetimes ranging from approximately 1-10 micros at 295 K. Analysis of the 0-0 energies and the redox potentials indicated that the lowest excited state of [Ir(L1)(L2)]2+ possessed the highest contribution of 3MLCT (MLCT = metal-to-ligand charge transfer) among the Ir(III) complexes, reflecting the sigma-donating ability of the tridentate ligand, ttpy < L1 < L2. The emission quantum yields (phi) of the Ir(III) complexes ranged from 0.037 to 0.19, and the highest phi value (0.19) was obtained for [Ir(L1)(bpy)Cl]2+. Radiative rate constants (k(r)) were 1.2 x 10(4) s(-1) for [Ir(ttpy)2]3+, 3.7 x 10(4) s(-1) for [Ir(L1)(bpy)Cl]2+, 3.8 x 10(4) s(-1) for [Ir(ttpy)(bpy)Cl]2+, 3.9 x 10(4) s(-1) for [Ir(L1)2]3+, and 6.6 x 10(4) s(-1) for [Ir(L1)(L2)]2+. The highest radiative rate for [Ir(L1)(L2)]2+ with the highest contribution of 3MLCT could be explained in terms of the singlet-triplet mixing induced by spin-orbit coupling of 5d electrons in the MLCT electronic configurations. 相似文献
45.
Kiyoshi Bannai Takeshi Toru Takeo Ba Toshio Tanaka Noriaki Okamura Kenzo Watanabe Seizi Kurozumi 《Tetrahedron letters》1981,22(15):1417-1420
Stable analogues of PGI2, 7-hydroxy- and 7-acetoxy-PGI2, were synthesized from protected PGI2 methyl ester via sulfoxides , through stereocontrolled sulfoxide-sulfenate rearrangement. 相似文献
46.
Noriaki Takahashi 《Hyperfine Interactions》1985,21(1-4):173-195
A series of experiments is described in which beta-ray asymmetry has been used to determine polarization of heavy-ion reaction products12B and the present status of the studies of polarization phenomena in heavy-ion reactions is reviewed. A large amount of angular momentum sustained by the two colliding nuclei gives rise to polarization phenomena of reaction products. Coupling between the degrees of freedom accompanying the intrinsic and the relative motions is investigated from the systematic behaviour of polarization of reaction products disclosed by the experiments. 相似文献
47.
Ichikawa S Minakawa N Shuto S Tanaka M Sasaki T Matsuda A 《Organic & biomolecular chemistry》2006,4(7):1284-1296
3'-beta-Carbamoylmethylcytidine (CAMC) and its derivatives were synthesized using an intramolecular Reformatsky-type reaction promoted by SmI2 as the key step. In vitro tumor cell growth inhibitory activity was evaluated and CAMC was found to exhibit potent cytotoxicity against various human tumor cell lines. From a structure-activity relationship study it was postulated that the cytotoxic mechanism of action of CAMC did not require phosphorylation at the 5'-hydroxyl group. This study provides a novel strategy for the development of a new type of antitumor nucleoside. 相似文献
48.
49.
Yoshiki Nakata Noriaki Miyanaga 《Applied Physics A: Materials Science & Processing》2010,98(2):401-405
Combined structures composed of a micron-sized periodic structure and a nano-sized quasi-periodic ripple structure were generated
by a single process of multiple shots of an interfering femtosecond laser. The former structure was generated by an interference
pattern and controlled by a number of beams. The latter structure was generated by a multiple shot method. As a result, multiple
periodic structures were generated. The periodicity of the structures was analyzed by two-dimensional (2D) fast Fourier transform
(FFT). The most probable period of ripple structure was downsized to 177 nm by restricting irradiated region by a TM wave
interference pattern. The smallest period was 105 nm. The dispersion angle of a ripple decreased to about 50%. The period
and direction of the ripples were for a first time controlled by using interference. 相似文献
50.
Masahito Katto Hironari Zushi Wataru Nagaya Shinya Harano Ryota Matsumoto Atushi Yokotani Masanori Kaku Shoichi Kubodera Noriaki Miyanaga 《Applied Physics A: Materials Science & Processing》2010,101(2):297-301
We have developed intense vacuum ultraviolet (VUV) radiation sources for advanced material processing, such as photochemical
surface reactions and precise processing on a nanometer scale. We have constructed a new VUV laser system to generate sub-picosecond
pulses at the wavelength of 126 nm. A seed VUV pulse was generated in Xe as the 7th harmonic of a 882-nm Ti:sapphire laser.
The optimum conversion was achieved at the pressure of 1.2 Torr. The seed pulse will be amplified by the Ar2*\mathrm{Ar}_{2}^{*} media generated by an optical-field-induced ionization Ar plasma produced by the Ti:sapphire laser. We have obtained a gain
coefficient of g=0.16 cm−1. Our developing system will provide VUV ultra-short pulses with sub-μJ energy at a repetition rate of 1 kHz. 相似文献