全文获取类型
收费全文 | 935篇 |
免费 | 32篇 |
国内免费 | 5篇 |
专业分类
化学 | 708篇 |
晶体学 | 10篇 |
力学 | 17篇 |
数学 | 46篇 |
物理学 | 191篇 |
出版年
2023年 | 7篇 |
2022年 | 2篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 14篇 |
2018年 | 12篇 |
2017年 | 3篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 21篇 |
2013年 | 47篇 |
2012年 | 45篇 |
2011年 | 69篇 |
2010年 | 28篇 |
2009年 | 33篇 |
2008年 | 58篇 |
2007年 | 68篇 |
2006年 | 76篇 |
2005年 | 73篇 |
2004年 | 62篇 |
2003年 | 52篇 |
2002年 | 61篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 17篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有972条查询结果,搜索用时 36 毫秒
51.
Duanjun Xu Kunio Miki Yasushi Kai Nobutami Kasai Masanori Wada 《Journal of organometallic chemistry》1985,287(2):265-273
The structure of a nickel(II) complex, trans-[Ni(C6Cl5)(PMe2Ph)2{C(OMe)Me}]BF4, containing the simplest alkyl(alkoxy)carbene ligand has been determined by X-ray crystallography (R = 0.091). The geometry around the nickel atom is square-planar. The comparatively short NiC(1) bond length of 1.843(10) Å showed the presence of π-bonding in the nickel-carbene bond. 相似文献
52.
Ruslim C Hashimoto M Matsunaga D Tamaki T Ichimura K 《Langmuir : the ACS journal of surfaces and colloids》2004,20(1):95-100
The inherent chromonic lyotropic liquid crystalline properties of a dye have been manipulated to fabricate multi-axial micropolarizing thin films by means of the photoalignment technique. The dye aqueous solution is deposited on a photopatterned polymer film to result in the macroscopic alignment of the dye molecules, followed by drying at ambient temperature. The solid polarizing dye layers thus produced exhibit very a high contrast ratio and degree of polarization in the region of visible light. Addition of a small amount of surfactant to the dye solution is a prerequisite for the generation of a nematic chromonic phase and for the formation of homogeneous thin dye layers on the polymer film. The correlation between the optical and surface morphological properties of the dye layers is discussed. 相似文献
53.
Shintani Y Hirako K Motokawa M Iwano T Zhou X Takano Y Furuno M Minakuchi H Ueda M 《Journal of chromatography. A》2005,1073(1-2):17-23
We have developed miniaturized multi-channel high-performance liquid chromatography (HPLC) system. With this system, we can simultaneously separate multiple samples, using a single high-pressure gradient pump, a chip-based sample injection unit, a monolithic silica capillary column array, and a multi-channel UV detection unit based on fiber optics. The injection unit has a simplified structure composed of brass housing and a quartz microchip having microchannels and access ports, which enable a direct injection of sample to multi-channel by commercial multichannel micropipette. Moreover, that possesses a function of microvalve, and on-chip definition of sample injection plugs achieved with a cross channel injection method, providing each column of monolithic silica capillary array. The substances in channels were simultaneously detected with UV having multiple cells. Standard samples were analyzed for characterizing newly developed system, and sharp peaks were obtained with reproducibility data of < 0.9% (R.S.D.). Analysis of tryptic digestion of casein was also employed. These results show that the novel multi-channel HPLC system has the benefits for the high-throughput analysis in the post-genomic analysis/combinatorial chemistry. 相似文献
54.
Buenker RJ Liebermann HP Melnikov V Tachikawa M Pichl L Kimura M 《The journal of physical chemistry. A》2005,109(26):5956-5964
Ab initio multireference single- and double-excitation configuration interaction (MRD-CI) calculations are carried out to study the interactions of positrons with the members of the alkali hydride class of molecules. A new computer program has been constructed for this purpose that makes use of the Table-Direct-CI method for construction of the required Hamiltonian matrixes and electronic/positronic wave functions. The calculations indicate that the binding energy (positron affinity PA) of a single positron to these systems increases by an increment of 0.2-0.3 eV as the atomic number of the alkali atom is increased. It is found that the positron prefers a location in the more electronegative regions of such molecules, similarly as has been found in earlier calculations for the urea and acetone molecules. The positron orbital itself possesses a diffuse charge distribution with relatively small expectation values of the kinetic energy in all four systems considered. Each of the four positronic molecules is stable with respect to formation of either positronium (Ps) or HPs according to the present calculations. Relatively large changes in the equilibrium bond distance of the hydrides occur as a result of the positron interaction. The importance of bond dipole moments in producing the binding of positrons to molecules is discussed, as well as the role that the electronegativity of the constituent atoms plays in determining the magnitude of the PA for a given system. 相似文献
55.
Rumiko Sakurai Kenichi Sakai Koichi Kodama Masanori Yamaura 《Tetrahedron: Asymmetry》2012,23(3-4):221-224
A useful key intermediate for the dipeptidyl peptidase-4 (DPP-4) inhibitor, 3-aminopiperidine 1, was successfully resolved with an enantiomerically pure resolving agent, N-tosyl-(S)-phenylalanine 2, to give both stereoisomers (R)-1 and (S)-1 as a less-soluble diastereomeric salt with (S)-2, via a dielectrically controlled resolution (DCR) phenomenon. 相似文献
56.
The studies of J. A. Ramírez, Hino–Ramírez, and Ariyoshi–Hino showed that an integrated version of Varadhan’s asymptotics holds for Markovian semigroups associated with arbitrary strong local symmetric Dirichlet forms. In this paper, we consider non-symmetric bilinear forms that are the sum of strong local symmetric Dirichlet forms and lower-order perturbed terms. We give sufficient conditions for the associated semigroups to have asymptotics of the same type. 相似文献
57.
Susumu Takigawa Masanori Koshimizu Takio Noguchi Tsutomu Aida Seiichi Takami Tadafumi Adschiri Yutaka Fujimoto Akira Yoko Gimyeong Seong Takaaki Tomai Keisuke Asai 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(2):611-615
We synthesized liquid scintillators incorporating ZrO2 nanoparticles for application in neutrinoless double beta decay experiments. ZrO2 nanoparticles of less than 10 nm in size were synthesized with sub- and supercritical hydrothermal methods. The Zr concentrations in the liquid scintillators were determined to be up to 1.4 wt% with inductively coupled plasma analysis, and the liquid scintillators were transparent to scintillation. These results indicate that these methods are applicable for the preparation of liquid scintillators for neutrinoless double beta decay experiments. 相似文献
58.
59.
60.
Dr. Takeshi Matsumoto Risa Yamamoto Dr. Masanori Wakizaka Dr. Akinobu Nakada Prof. Dr. Ho-Chol Chang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9609-9619
The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H2) important. A high-spin (hs) FeII complex with o-phenylenediamine (opda) ligands, [FeII(opda)3]2+ (hs- [6R] 2+), was reported showing photochemical H2 evolution. In addition, a low-spin (ls) [FeII(bqdi)3]2+ (bqdi: o-benzoquinodiimine) (ls- [0R] 2+) formation by O2 oxidation of hs- [6R] 2+, accompanied by ligand-based six-proton and six-electron transfer, revealed the potential of the complex with redox-active ligands as a novel multiple-proton and -electron storage material, albeit that the mechanism has not yet been understood. This paper reports that the oxidized ls- [0R] [PF6]2 can be reduced by hydrazine giving ls-[FeII(opda)(bqdi)2][PF6]2 (ls- [2R] [PF6]2) and ls-[FeII(opda)2(bqdi)][PF6]2 (ls- [4R] [PF6]2) with localized ligand-based proton-coupled mixed-valence (LPMV) states. The first isolation and characterization of the key intermediates with LPMV states offer unprecedented molecular insights into the design of photoresponsive molecule-based hydrogen-storage materials. 相似文献