全文获取类型
收费全文 | 343篇 |
免费 | 21篇 |
国内免费 | 6篇 |
专业分类
化学 | 311篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 4篇 |
物理学 | 47篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2019年 | 1篇 |
2018年 | 9篇 |
2017年 | 1篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 5篇 |
2012年 | 32篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 13篇 |
2008年 | 28篇 |
2007年 | 9篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有370条查询结果,搜索用时 0 毫秒
81.
Toshihide Tsukatani Hajime Katano Hirosuke Tatsumi Mika Deguchi Naoki Hirayama 《Analytical sciences》2006,22(2):199-200
The tetraoctylammonium cation forms water-immiscible room temperature ionic liquids with dodecylsulfate and dodecylbenzenesulfonate anions. The ionic liquids are halogen-free and can be considered environmentally friendly solvents. At 25 degrees C, the solubilities of water in tetraoctylammonium dodecylsulfate and tetraoctylammonium dodecylbenzenesulfonate were 2.8 and 4.0%, respectively, and the densities were 0.92 and 0.93 g cm(-3). The ionic liquids formed stable interfaces with water at 25 degrees C. The possible use of tetraoctylammonium dodecylsulfate as chelate extraction solvent was evaluated by using 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione as extractant. Tetraoctylammonium dodecylsulfate showed high extraction performance for divalent transition metal cations. 相似文献
82.
Three transition metal cyanoimido (NCN2-) complexes, (Cp*WS2)2(mu-NCN) (1) (Cp* = eta 5-C5Me5), K[(Cp*WS2)2(NCN)] (2) and ([bipy)2Co]2(mu-NCN)2)(ClO4)2 (3), were synthesized from dipotassium cyanamide, and their structures were determined. 相似文献
83.
The perturbation theory of Murrell, Randi and Williams for intermolecular interaction has been combined with the assumption of local zero-differential overlaps. The theory has been applied to the cycloadditions of singlet methylene and halocarbenes toward olefins. The results, obtained by use of the CNDO/2 energies and wave functions for isolated molecules, quantitatively assess the roles of various types of energies influencing the stereochemical courses of reaction. The syn/anti stereoselectivities of halocarbenes in their cycloadditions toward cis-butene-2 are found to be governed by the Coulombic, dispersion, charge-transfer and exchange-repulsion energies altogether. Participation of the d orbitals of the chlorine atom in charge transfer is emphasized.
Zusammenfassung Die Störungsrechnung von Murrell, Randic und Williams für intermolekulare Wechselwirkung wurde in Verbindung mit der Annahme von lokalen ZDO zur Berechnung der Cycloaddition von Singulett-Methylen oder -Halogencarbenen an Olefine angewendet. Die Resultate, die über die CNDO/2-Ergebnisse für die isolierten Moleküle erhalten wurden, lassen die Rolle der einzelnen Energieanteile erkennen, die die Stereochemie der Reaktion beeinflussen. Die syn/anti-Stereoselektivität der Halogencarbene gegenüber cis-2-Buten wird durch die Coulomb-, Dispersions-, Charge-transfer- und Austausch-Wechselwirkung gemeinsam bestimmt. Auch die d-Orbitale von Chlor sind für den Charge transfer von Bedeutung.相似文献
84.
Se Ahn Song Tatsumi Hirano Jong Bong Park Kazutoshi Kaji Ki Hong Kim Shohei Terada 《Microscopy and microanalysis》2005,11(5):431-445
Practical analyses of the structures of ultrathin multilayers in tunneling magneto resistance (TMR) and Magnetic Random Access Memory (MRAM) devices have been a challenging task because layers are very thin, just 1-2 nm thick. Particularly, the thinness (approximately 1 nm) and chemical properties of the AlOx barrier layer are critical to its magnetic tunneling property. We focused on evaluating the current TEM analytical methods by measuring the thickness and composition of an AlOx layer using several TEM instruments, that is, a round robin test, and cross-checked the thickness results with an X-ray reflectometry (XRR) method. The thickness measured by using HRTEM, HAADF-STEM, and zero-loss images was 1.1 nm, which agreed with the results from the XRR method. On the other hand, TEM-EELS measurements showed 1.8 nm for an oxygen 2D-EELS image and 3.0 nm for an oxygen spatially resolved EELS image, whereas the STEM-EDS line profile showed 2.5 nm in thickness. However, after improving the TEM-EELS measurements by acquiring time-resolved images, the measured thickness of the AlOx layer was improved from 1.8 nm to 1.4 nm for the oxygen 2D-EELS image and from 3.0 nm to 2.0 nm for the spatially resolved EELS image, respectively. Also the observed thickness from the EDS line profile was improved to 1.4 nm after more careful optimization of the experimental parameters. We found that EELS and EDS of one-dimensional line scans or two-dimensional elemental mapping gave a larger AlOx thickness even though much care was taken. The reasons for larger measured values can be found from several factors such as sample drift, beam damage, probe size, beam delocalization, and multiple scattering for the EDS images, and chromatic aberration, diffraction limit due to the aperture, delocalization, alignment between layered direction in samples, and energy dispersion direction in the EELS instrument for EELS images. In the case of STEM-EDS mapping with focused nanoprobes, it is always necessary to reduce beam damage and sample drift while trying to maintain the signal-to-noise (S/N) ratio as high as possible. Also we confirmed that the time-resolved TEM-EELS acquisition technique improves S/N ratios of elemental maps without blurring the images. 相似文献
85.
86.
Yilmaz B Müller U Tijsebaert B De Vos D Xie B Xiao FS Gies H Zhang W Bao X Imai H Tatsumi T 《Chemical communications (Cambridge, England)》2011,47(6):1812-1814
A new zeolite catalyst, Al-RUB-41, was synthesized for the first time. It was tested as a catalyst in methanol amination, and showed a shape-selective performance that results in a highly favorable product distribution. The shape-selective nature was also evidenced by using Pt-Al-RUB-41 as a bifunctional catalyst for decane hydroconversion. With its unique pore architecture and remarkable shape-selective character, Al-RUB-41 presents a significant commercial potential in industrial catalysis. 相似文献
87.
88.
Misa Numano Naoto Nagami Soichiro Nakatsuka Takazumi Katayama Kiichi Nakajima Sou Tatsumi Dr. Nobuhiro Yasuda Prof. Dr. Takuji Hatakeyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11574-11577
A demethylative direct borylation is reported, which was applied to the synthesis of benzo[fg]tetracenes containing boronate ester, amide, and thioester substructures. Depending on the heteroatom adjacent to boron, the molecules showed characteristic photophysical properties, molecular arrangements, and chemical stabilities. The key to the successful synthesis is the appropriate choice of the boron source and Brønsted base. The versatility of the direct borylation was demonstrated by the synthesis of a boronate‐based benzo[hi]hexacene. 相似文献
89.
Toshiyuki Yokoi Syusaku Sato Yoichiro Ara Daling Lu Yoshihiro Kubota Takashi Tatsumi 《Adsorption》2010,16(6):577-586
Chiral mesoporous silica (CMS) has been successfully synthesized in the presence of basic amino acids; the use of basic amino
acids in combination with the chiral anionic surfactant is advantageous for the formation of CMS in terms of uniformity in
the twisted morphology. We first demonstrate that thus obtained chiral mesoporous silicas can be used for the enantioselective
separation of racemic compounds; the helical rod-shaped CMS is found to be capable of asymmetric separation of racemic N-trifluoroacetylalanine ethyl ester (CF3CO-Ala-OEt). The left handedness-rich CMS shows asymmetric preferential adsorption of the L isomer and vice versa. 相似文献