全文获取类型
收费全文 | 1545篇 |
免费 | 37篇 |
国内免费 | 8篇 |
专业分类
化学 | 1172篇 |
晶体学 | 21篇 |
力学 | 17篇 |
综合类 | 1篇 |
数学 | 126篇 |
物理学 | 253篇 |
出版年
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 18篇 |
2019年 | 23篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 24篇 |
2015年 | 24篇 |
2014年 | 34篇 |
2013年 | 119篇 |
2012年 | 50篇 |
2011年 | 85篇 |
2010年 | 40篇 |
2009年 | 51篇 |
2008年 | 80篇 |
2007年 | 84篇 |
2006年 | 76篇 |
2005年 | 74篇 |
2004年 | 84篇 |
2003年 | 69篇 |
2002年 | 61篇 |
2001年 | 30篇 |
2000年 | 19篇 |
1999年 | 12篇 |
1998年 | 25篇 |
1997年 | 17篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 15篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1972年 | 6篇 |
1967年 | 7篇 |
1956年 | 6篇 |
排序方式: 共有1590条查询结果,搜索用时 62 毫秒
41.
Transition of the radial electric field by electron cyclotron heating in the CHS heliotron/torsatron
42.
43.
Leesajakul W Nakano M Taniguchi A Handa T 《Colloids and surfaces. B, Biointerfaces》2004,34(4):253-258
Cubosomes are novel dispersed nanoparticles with bicontinuous cubic phases of monoolein in their interior. We investigated their disintegration process in plasma by in vitro and in vivo studies. Cubosomes were incubated with whole plasma or plasma components such as HDL, LDL, and albumin. The lypolysis study indicated lipolytic activity of whole plasma towards cubosomes. Gel filtration chromatography revealed that HDL, LDL and albumin interacted with cubosomes. HDL affected cubosomes’ integrity and gave rise to smaller particles which contained the components of both cubosomes and HDL. Upon incubation with LDL, cubosomes fused with LDL. Albumin was shown to take up monoolein out of the particles. Cubosomes were disintegrated by whole plasma as a result of the interaction with plasma components. It was concluded that in vivo observation of a long circulation time of a hydrophobic substance in cubosomes was due to the sustained behavior of cubosome remnant particles. 相似文献
44.
Yasuhiro Takahashi Yusuke Ozaki Minoru Takase W. R. Krigbaum 《Journal of Polymer Science.Polymer Physics》1993,31(9):1135-1143
Redetermination of the crystal structure of poly(p-benzamide) was made by using newly collected intensity data. The molecular conformation is TCTC, where the internal rotation angles about the N? C bond of the amide group and about the virtual bond of N-phenyl-C are T (trans) and C (cis) conformations, respectively. Two molecular chains pass through a rectangular unit cell with dimension, a = 7.75 Å, b = 5.30 Å, c (fiber axis) = 12.87 Å, and the space group, P212121-D. The reflection observed at the spacing of 010 may be attributed to the reflection due to another crystal polymorph or the diffuse scattering due to disorder. © 1993 John Wiley & Sons, Inc. 相似文献
45.
Minoru Yoshimoto 《Chemical physics letters》1997,280(5-6)
The behavior of the phase-death mode (cessation of oscillations and transition to a steady state) in the two-coupled Belousov–Zhabotinsky reactions is studied in the asymmetric coupling. In an experiment, the types of synchronized modes and their regions were investigated as an extension of our previous study. This experiment is compared to a simulation using the two-coupled three-variable Oregonator models. The results confirm that the phase-death mode changes from “bistable” to “monostable” and reveal the stable region of the latter. 相似文献
46.
Copper mediated alkyl-transfer reaction of trialkylaluminum (R3Al) with (E)-4,4-difluoro-5-hydroxyallylic alcohol derivative smoothly proceeded to give the corresponding 2-alkylated 4-fluoro-5-hydroxyhomoallylic alcohol derivative with completely Z and 2,5-syn selective manner. Regio- and stereoselective conversion of the C5-hydroxyl group of the fluoroolefin thus obtained to amino group could be achieved through one-pot mesylation and azidation reaction. 相似文献
47.
Determination of chemical form of antimony in contaminated soil around a smelter using X-ray absorption fine structure. 总被引:1,自引:0,他引:1
Masaki Takaoka Satoshi Fukutani Takashi Yamamoto Masato Horiuchi Naoya Satta Nobuo Takeda Kazuyuki Oshita Minoru Yoneda Shinsuke Morisawa Tsunehiro Tanaka 《Analytical sciences》2005,21(7):769-773
Only limited information is available about the behavior of antimony (Sb) in contaminated soils. However, understanding the behavior of Sb in contaminated soils is important, because the toxicity or solubility of this element depends on its chemical state. In this study, we investigated the levels of Sb and the chemical forms of Sb in the soil around a smelter using X-ray absorption fine structure (XAFS) spectra. The highest Sb concentration in the contaminated soil was 2900 mg/kg dry soil. According to Sb-K edge X-ray absorption near edge (XANE) spectra, the Sb in the soil was in the form of Sb(V) compounds. The similarity of extended XAFS (EXAFS) spectra suggests that Sb speciation was independent of the sampling site, which indicates that Sb or Sb2O3 emitted from the smelter was converted into Sb(V) compounds in the soil. 相似文献
48.
Photolysis of the N-[ω-(cycloalken-1-yl)alkyl]phthalimides 6b- in each case gave a pair of stereoisomers of spiro-nitrogen multicyclic systems (9b-) in moderate yields, whose stereochemistry was determined by means of chemical and spectroscopic analyses. Similarly, in N-[ω-(inden-3-yl)alkyl]-phthalimides (8), spiro-nitrogen macrocycles up to 13-membered 13a- were obtained in good yields 相似文献
49.
Albano VG Di Serio M Monari M Orabona I Panunzi A Ruffo F 《Inorganic chemistry》2002,41(10):2672-2677
The silver-assisted ligand metathesis reaction involving a platinum(II) complex of formula [PtClMe(N,N-chelate)] with acetonitrile has been investigated. By using a suitably hindered N,N-chelate, an otherwise hardly detectable trinuclear species has been isolated and characterized through X-ray diffractometry. The trinuclear cation consists of two nearly orthogonal [PtCl(Me)(N,N-chelate)] square-planar units entrapping an Ag(+) cation through the chloride ligands that, acting as bidentate, form a linear AgCl(2) unit with two nonequivalent Ag-Cl bonds. The residual acidity of the silver cation is satisfied by one secondary Ag-Pt interaction [Ag-Pt(1) = 2.82 A] in which the platinum atom acts as a donor. Kinetic studies have demonstrated that the silver assistance operates both through a simple associative step and through a pathway in which the above trinuclear complex is an active intermediate. In a noncoordinating solvent the latter species evolves with AgCl loss and formation of a dinuclear Pt,Pt complex showing a rare single chloride bridge. 相似文献
50.
The chiral separation ability of unmodified and di- and trimethylated -, β- and γ-cyclodextrins (CDs) as chiral selectors in capillary zone electrophoresis was investigated in the presence of urea derivatives using twelve dansylamino acids as model solutes. The addition of these urea derivatives (unsubstituted, methyl-, ethyl- and 1,3-dimethylureas) produced dramatic enhancement in the enantioselectivity of unmodified β-CD but also reduced the enantioselectivities of the other CDs. 相似文献