全文获取类型
收费全文 | 384篇 |
免费 | 7篇 |
专业分类
化学 | 274篇 |
晶体学 | 2篇 |
力学 | 13篇 |
数学 | 7篇 |
物理学 | 95篇 |
出版年
2022年 | 3篇 |
2021年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 8篇 |
2013年 | 28篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 13篇 |
2005年 | 13篇 |
2004年 | 30篇 |
2003年 | 20篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有391条查询结果,搜索用时 15 毫秒
241.
Abstract The magnetic circular dichroism (MCD) and absorption spectra of some p-disubstituted benzenes possessing both electron-donating and accepting groups were measured. The electronic spectra of the above compounds are characterized by the appearance of two absorption bands, one of which appears at 25000–40000 cm?1 region with large intensity, and another at 40000–50000 cm?1 region with rather small intensity. These absorption bands, especially the latter one, have been investigated by means of the MCD spectra and molecular orbital calculations based on the Pariser-Parr-Pople method. 相似文献
242.
A method to compute magnetic shielding tensors with generalized hybrid-orbital (GHO) QM/MM scheme is developed at the levels of Hartree-Fock and second-order M?ller-Plesset perturbation theory using gauge-including atomic orbitals. A feature of the GHO method is utilized to ensure gauge-origin independency of GHO shielding tensors in a simple way. The benchmark calculations indicate that the GHO method reproduced full-QM shielding constants nearly quantitatively for atoms not directly coupled to the GHO linking atoms. As an application to a realistic protein, carbon chemical shifts are calculated for the retinal chromophore in visual rhodopsin. 相似文献
243.
Kodo Kawase Manabu Sato Tetsuo Taniuchi Hiromasa Ito 《International Journal of Infrared and Millimeter Waves》1996,17(11):1839-1849
Wide tunable terahertz (THz) wave generation was successfully demonstrated utilizing a grating coupler fabricated on the surface of a LiNbO3 crystal which was pumped by a Q-switched Nd:YAG laser. In this paper, we report the detailed characteristics of the oscillation and the radiation including tunability, spatial and temporal coherency, directivity, and efficiency. Oscillation using a LiTaO3 crystal was also performed, in which experimental phasematching condition values agreed well with the calculated one. 相似文献
244.
245.
Mitsuro Kato Toshihiko Ito Yoshitaka Aoyama Koji Sawa Takeshi Kaneko Noboru Kawase Hiroshi Jinnai 《Journal of Polymer Science.Polymer Physics》2007,45(6):677-683
A three‐dimensional (3D) lamellar structure of a poly(styrene‐block‐isoprene) block copolymer was observed at submicrometer and micrometer levels by scanning electron microscopy combined with a focused ion beam (FIB–SEM). The 3D lamellar structure with an exceptionally large periodicity, about 0.1 μm, was successfully reconstructed, and the size of the reconstructed image by FIB–SEM was 6.0 × 6.0 × 4.0 μm3, which was greater than the transmission electron microtomography data, 3.8 × 3.9 × 0.24 μm3, by a factor of about 40. This result indicates that 3D reconstruction using FIB–SEM is quite useful for direct 3D observations, especially analyses of polymeric materials at the submicrometer and micrometer levels. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 677–683, 2007 相似文献
246.
247.
Y. Toh S. Yamada A. Taniguchi Y. Kawase 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):331-332
Abstact: Multipolarities of γ-rays in 152Nd have been studied by conversion electron measurements in the β− decay of 152Pr. The praseodymium activities were obtained by the thermal neutron fission of 235U and followed with the on-line isotope separator KUR–ISOL. Conversion electrons and γ-rays were measured with a Si(Li) detector
and a HPGe detector, respectively. The two γ-rays, 226 keV and 285 keV, were decided to have the multipolarities of the E1
transition. The spins and parities of the 1600 keV and 1542 keV levels were determined to be 3+ and 2+, respectively.
Received: 14 April 1998 相似文献
248.
Yasumitsu Matsuo Keiko Saito Hiroshi Kawashima Seiichiro Ikehata 《Solid State Communications》2004,130(6):411-414
We have fabricated a fuel cell based on a superprotonic conductor, a Tl3H(SO4)2 crystal, and have measured the electrical properties of this fuel cell. It is found that the open-circuit voltage in the fuel cell based on the Tl3H(SO4)2 crystal increases by supplying H2 fuel gas and typically becomes 0.83 V. Moreover, we have observed that the cell voltage decreases with increasing current density, as observed in fuel cells such as proton exchange membrane fuel cell, solid oxide fuel cell, etc. These results indicate that it is possible to use the Tl3H(SO4)2 crystal as the electrolyte of a solid acid fuel cell. In addition, we suggest that the selection of the electrode and the preparation of the very thin electrolyte are extremely important to achieve high-efficiency of power generation of this fuel cell. 相似文献
249.
A validated two-dimensional HPLC method for the comprehensive analysis of small quantities of branched aliphatic D-amino acids in the presence of large amounts of their L-congeners in mammalian tissues and physiological fluids is described. The quantitative analysis of these aliphatic amino acids (Val, allo-Ile, Ile, and Leu) is important for the diagnosis of various inherent metabolic disorders of amino acids, and the D-enantiomers are expected to be of particular interest from a pharmacological point of view. Target analytes were determined as their fluorescent derivatives, pre-column labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), using an automated two-dimensional column-switching high-performance liquid chromatographic system combining a narrow bore reversed-phase column and an enantioselective column connected with an integrated multi-loop peak fraction storage device. The described two-dimensional analysis concept proved to be successful for the given task in biological samples taken from mammals. Total analysis time for the reversed-phase separation of the four target NBD-amino acids is 60 min, and the integrated enantiomer separation of each of the four analytes is completed in approximately 5 min. In the rat, significant amounts of D-Leu were found in all tissues and physiological fluids tested (trace-1.3 nmol/g tissue), and in the urine, the presence of high amounts of D-allo-Ile (D-isomer of a non-proteinogenic amino acid, 22.2 nmol/ml) was demonstrated. D-allo-Ile was also found in the urine of dog and mouse, which indicates the ubiquitous presence of this unusual D-amino acid and the potential need to clarify its unique metabolism in mammals. 相似文献
250.
An indoor traction measurement system for agricultural tires 总被引:1,自引:0,他引:1
To reliably study soil–wheel interactions, an indoor traction measurement system that allows creation of controlled soil conditions was developed. This system consisted of: (i) single wheel tester (SWT); (ii) mixing-and-compaction device (MCD) for soil preparation; (iii) soil bin; (iv) traction load device (TLD). The tire driving torque, drawbar pull, tire sinkage, position of tire lug, travel distance of the SWT and tire revolution angle were measured. It was observed that these measurements were highly reproducible under all experimental conditions. Also relationships of slip vs. sinkage and drawbar pull vs. slip showed high correlation. The tire driving torque was found to be directly influenced by the tire lug spacing. The effect of tire lug was also discussed in terms of tire slip. 相似文献