全文获取类型
收费全文 | 517篇 |
免费 | 4篇 |
专业分类
化学 | 303篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 2篇 |
物理学 | 208篇 |
出版年
2022年 | 3篇 |
2020年 | 2篇 |
2018年 | 5篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 9篇 |
2012年 | 29篇 |
2011年 | 25篇 |
2010年 | 12篇 |
2009年 | 26篇 |
2008年 | 23篇 |
2007年 | 31篇 |
2006年 | 21篇 |
2005年 | 27篇 |
2004年 | 23篇 |
2003年 | 24篇 |
2002年 | 24篇 |
2001年 | 10篇 |
2000年 | 17篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 16篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 17篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有521条查询结果,搜索用时 31 毫秒
81.
H. Iwasawa J.F. Douglas K. Sato T. Masui Y. Yoshida Z. Sun H. Eisaki H. Bando A. Ino M. Arita K. Shimada H. Namatame M. Taniguchi S. Tajima S. Uchida T. Saitoh D.S. Dessau Y. Aiura 《Physica C: Superconductivity and its Applications》2010
Using angle-resolved photoemission spectroscopy (ARPES) with low-energy tunable photons, we studied the oxygen isotope effect in optimally doped Bi2Sr2CaCu2O8+δ (Bi2212). We found the oxygen isotope shift in the real part of the electron self-energies [ReΣ(ω)s] along the nodal direction derived not only from the momentum distribution curves (MDCs) but also from the energy distribution curves (EDCs). Present results indicate straightforwardly the coupling between the nodal electrons and the phonons. 相似文献
82.
Yoshitane Imai Dr. Katuzo Murata Kakuhiro Kawaguchi Tomohiro Sato Nobuo Tajima Dr. Reiko Kuroda Dr. Yoshio Matsubara Dr. 《化学:亚洲杂志》2008,3(3):625-629
A solid‐state fluorescent host system was created by self‐assembly of a 21‐helical columnar organic fluorophore composed of (1R,2S)‐2‐amino‐1,2‐diphenylethanol and fluorescent 1‐pyrenecarboxylic acid. This host system has a characteristic 21‐helical columnar hydrogen‐ and ionic‐bonded network. Channel‐like cavities are formed by self‐assembly of this column, and various guest molecules can be included by tuning the packing of this column. Moreover, the solid‐state fluorescence of this host system can change according to the included guest molecules. This occurs because of the change in the relative arrangement of the pyrene rings as they adjust to the tuning of the packing of the shared 21‐helical column, according to the size of the included guest molecules. Therefore, this host system can recognize slight differences in molecular size and shape. 相似文献
83.
Hayasaka T Goto-Inoue N Sugiura Y Zaima N Nakanishi H Ohishi K Nakanishi S Naito T Taguchi R Setou M 《Rapid communications in mass spectrometry : RCM》2008,22(21):3415-3426
We recently developed a matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight (MALDI-QIT-TOF)-based imaging mass spectrometry (IMS) system. This system enables us to perform structural analyses using tandem mass spectrometry (MS/MS), as well as to visualize phospholipids and peptides in frozen sections. In the retina, phototransduction is regulated by the light-sensitive interaction between visual pigment-coupled receptor proteins, such as rhodopsin, and G proteins, such as transducin. There are some reports that the conformation of rhodopsin is influenced by the composition of phospholipids in the lipid bilayer membrane. However, these results were based on in vitro experiments and have not been analyzed in vivo. In this study, we visualized and identified phospholipids in mouse retinal sections with the MALDI-QIT-TOF-based IMS system. From a spectrum obtained by raster-scanned analysis of the sections, ions with high signal intensities were selected and analyzed by MS/MS. As a result, sixteen ions were identified as being from four diacyl-phosphatidylcholine (PC) species, i.e., PC (16:0/16:0), PC (16:0/18:1), PC (16:0/22:6), and PC (18:0/22:6), with different ion forms. The ion images revealed different distributions on the retinal sections: PC (16:0/18:1) was distributed in the inner nuclear layer and outer plexiform layer, PC (16:0/16:0) in the outer nuclear layer and inner segment, and both PC (16:0/22:6) and PC (18:0/22:6) in the outer segment and pigment epithelium. In conclusion, our in vivo IMS analyses demonstrated a three-zone distribution of PC species on the retinal sections. This approach may be useful for analyzing lipid changes and their contribution to phototransduction in the retina. 相似文献
84.
Reduction of dibenzo[a,e]pentalene 3 (denoted as dibenzopentalene hereafter) with excess lithium gave dilithium dibenzopentalenide 1. Since oxidation of 1 with iodine gave 3, redox behavior between 1 and 3 is controllable and reversible. Reaction of 3 with methyllithium gave lithium 5-methyldibenzopentalenide 5, the formation of which was evidenced by some trapping experiments and X-ray crystallographic analysis. Reactions of 3 with halogens gave 5,10-dihalodibenzopentalenes, 8 and 9. Some optical properties of novel dibenzopentalene derivatives are also demonstrated. 相似文献
85.
Fuchino H Sekita S Mori K Kawahara N Satake M Kiuchi F 《Chemical & pharmaceutical bulletin》2008,56(1):93-96
A new furostan-type saponin (1) was isolated from the methanolic extract of Brunfelsia grandiflora leaves, together with four known compounds. The chemical structure of 1 was determined by spectroscopic analysis and chemical reaction to be 26-O-beta-D-glucopyranosyl 22alpha-methoxyfurost-3beta,26-diol 3-O-beta-D-xylopyranosyl(1-->3)-{beta-D-glucopyranosyl(1-->2)}-beta-D-glucopyranosyl(1-->4)-beta-D-glucopyranoside. Compound 1 showed potent leishmanicidal activity in vitro against Leishmania major. 相似文献
86.
Ichikawa S Kimura S Takahashi K Mori H Yoshida G Manabe Y Matsuda M Tajima H Yamaura J 《Inorganic chemistry》2008,47(10):4140-4145
New supramolecular copper complexes with pyrazinotetrathiafulvalene (pyra-TTF) as the ligand, [Cu(II)Cl2(pyra-TTF)] (1) and (pyra-TTF) 2[Cu(I)3Cl4(pyra-TTF)] (2), have been synthesized by the diffusion method. Complex 1 is a black block crystal with a three-dimensional (3-D) supramolecular network; the linear chain [-Cu(II)Cl2-(pyra-TTF)-] n extends along the b axis, where the coordinated pyra-TTF donors are stacked in a head-to-tail and ring-over-bond configuration to construct two-dimensional (2-D) sheets, and between the sheets, there are C...Cl(-) or H...Cl(-) contacts. Even though the electron spin resonance (ESR) measurement reveals the nearly Cu(II) state, complex 1 is a semiconductor with sigmaRT=1.0 x 10(-4) S cm(-1) and Ea=0.33 eV. The high-frequency conductivity measurement also confirmed the intrinsic slight carrier doping from Cu(II) to the pyra-TTF donor. This slight doping enhances not only the real and imaginary dielectric constants but also the antiferromagnetic interaction between Cu(II) spins following the 2-D Heisenberg model with 2J=-20 K. In contrast, complex 2 is a very thin black needle. This needle crystal has two crystallographically independent pyra-TTF molecules, which are coordinated and noncoordinated donors. The coordinated donors composed a supramolecular chain [Cu(I)3Cl4(pyra-TTF)(0)]n , whereas the noncoordinated donors formed conducting alpha'-type pyra-TTF(+0.5) sheets. This complex is semiconducting with sigmaRT=0.1 S cm(-1) and Ea=0.15 eV. Both complexes 1 and 2 demonstrate that the pyra-TTF molecule works not only as an oxidized donor by Cu(II) to construct conducting sheets but also as a ligand coordinated to a Cu cation to form supramolecuar chains. 相似文献
87.
88.
89.
Ab initio calculations up to MP4(SDTQ) level and density functional theory have been used to estimate binding energies and electronic structures of Cu+(L)n (L=OH2, NH3, n=1–4) complexes using TZP basis set types. The computed binding energies agree well with experimental values. General trends in structures and energetics are recorded for both Cu+(OH2)n and Cu+(NH3)n systems. The first two ligands are more strongly bound to Cu+ than the third and fourth molecules. The 4s–3dσ hybridization and electrostatic interactions are the main factors behind the higher binding energies for the first two ligands. Analysis of HOMO mixed orbitals in the copper ion as well as in complexes indicates shrinking of the orbital lobes directed to the ligand with shrinking more effective in the two ligand system. The lower binding energies for the third and fourth ligands were attributed to the attenuation of sdσ hybridization and decreasing of Cu–L attraction at long separation which is necessary to relieve Cu–L and L–L exchange repulsions. NBO analysis and charge-model calculations support the presence of sdσ hybridization and electron transfer to the copper ion in case of the first two ligands. 相似文献
90.
Keisuke Tajima Gen Ogawa Takuzo Aida 《Journal of polymer science. Part A, Polymer chemistry》2000,38(Z1):4821-4825
A novel molecularly hybridized polyethylene/silica composite thin film was obtained by the gas‐phase polymerization of ethylene with a titanocene‐mounted mesoporous silica layer on a mica plate with mesoscopic pores arranged on the film surface. However, the use of titanocene‐mounted hexagonal domains of mesoporous silica on a glass plate for the gas‐phase polymerization of ethylene resulted in the formation of an islanded polyethylene/silica hybridized material. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4821–4825, 2000 相似文献