全文获取类型
收费全文 | 358篇 |
免费 | 12篇 |
专业分类
化学 | 286篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 1篇 |
物理学 | 76篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 22篇 |
2005年 | 23篇 |
2004年 | 11篇 |
2003年 | 23篇 |
2002年 | 21篇 |
2001年 | 14篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 5篇 |
排序方式: 共有370条查询结果,搜索用时 15 毫秒
141.
142.
Tomoaki Seyama Toshifumi Tanimura Keigo Tashiro Suzuko Yamazaki 《Research on Chemical Intermediates》2017,43(9):5025-5039
Porous platinum ion-doped TiO2 (Pt–TiO2) was prepared by a sol–gel method and demonstrated to have superior photocatalytic activity for the photodegradation of gaseous trichloroethylene (TCE) under visible light (VL) irradiation from a xenon lamp equipped with 422-nm cut-off filter. Kinetic studies were performed to clarify the effect of the doping amounts, space times, VL intensity, and mole fractions of TCE, O2, and H2O on the degradation of TCE. Under ultraviolet (UV) irradiation, the photocatalytic activity of Pt–TiO2 was the same as that of TiO2, indicating that the doped Pt ion did not act as a recombination center for the photogenerated holes and electrons. Based on the kinetic data and reaction products, we conclude that the photocatalytic degradation of TCE on Pt–TiO2 under VL irradiation proceeds similarly to TiO2 under UV irradiation. We also performed the photocatalytic degradation of TCE at the space time of 7.5 × 107 g s mol?1 in a tubular reactor packed with the Pt–TiO2 pellets which are more suitable than the Pt–TiO2 powder for the practical remediation of the contaminated gas. TCE was completely degraded, i.e. 100% conversion was achieved under VL irradiation but only a small quantity of CO2 was formed with the stoichiometric ratio of [CO2]formed/[TCE]degraded of ca. 0.33. By switching the gas stream containing TCE to humid air, more CO2 was formed, indicating that the dichloroacetates accumulated on the Pt–TiO2 surface are photodegradable to CO2 under VL irradiation. 相似文献
143.
Iridium‐Catalyzed Reductive Carbon–Carbon Bond Cleavage Reaction on a Curved Pyridylcorannulene Skeleton 下载免费PDF全文
Dr. Shohei Tashiro Dr. Mihoko Yamada Prof. Dr. Mitsuhiko Shionoya 《Angewandte Chemie (International ed. in English)》2015,54(18):5351-5354
The cleavage of C? C bonds in π‐conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an aromatic C? C bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2‐pyridylcorannulene with a catalytic amount of IrCl3?n H2O in ethylene glycol at 250 °C resulted in a structural transformation from the curved corannulene skeleton to a strain‐free flat benzo[ghi]fluoranthene skeleton through a site‐selective C? C cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2‐pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on C? C bond cleavage reactions. 相似文献
144.
A diastereoselective synthesis of the Leu-Pro type phosphinyl dipeptide isostere in its protected form was achieved from stereodefined α-amino-H-phosphinate. The methodology involved a cross-coupling reaction with alkenyl triflate and subsequent diastereoselective hydrogenation of the alkene moiety, which capitalized on the phosphorus chirality. 相似文献
145.
Yuko Izuchi Nobuhiro KanomataHiroyuki Koshino Yayoi HongoTadashi Nakata Shunya Takahashi 《Tetrahedron: Asymmetry》2011,22(2):246-251
The formal total synthesis of aspergillide A 1 is described. The cross-metathesis of enone 6 with 6-hepten-2-ol derivative 5 provided E-olefin 15 corresponding to the C4-C14 backbone of 1. The CBS asymmetric reduction of 15 gave allyl alcohol 16, which was transformed into β-alkoxyacrylate 4 which had a formyl group. SmI2-induced reductive cyclization of 4 gave a 2,6-syn-2,3-trans THP derivative 3 in good yield. After methoxymethylation of 3, the resulting compound 19 was submitted to desilylation and hydrolysis, to afford Fuwa’s key intermediate 2 for the total synthesis of 1. 相似文献
146.
Efficient pulse sequences for measuring long-range C-H coupling constants (J(C-H)) and proton-proton spin coupling constants (J(H-H)), named BIRD-J-resolved HMBC and BIRD-high-resolution HMBC, respectively, have been developed. In spin systems possessing a secondary methyl group positioned between protonated carbons (e.g. -CH(2)-CH(CH(3))-CH(2)-), the methine proton splits in a complicated fashion, resulting in difficulty in the determination of its spin coupling constants. For easy and accurate measurements of the long-range J(C-H) and J(H-H) in such a spin system, the BIRD pulse [90°x(H)-180°x (H/C)- 90° (-x)(H)] or [90°x(H)-180°x(H/C)-90° (-x)(H)180°x(C)] is incorporated into the J-resolved portion of the pulse sequence. As a result, the above secondary methyl group can be selectively decoupled, providing simplified cross-peak patterns, which are suitable for the accurate measurements of the long-range J(C-H) and J(H-H). 相似文献
147.
The first step toward elucidating the mutagenic effects of chemicals and pathways is to determine the specificity of the mutations generated spontaneously or in response to treatment with mutagens. We constructed a set of plasmid-encoded probes for the specific detection of each type of base substitution mutation. Using these probes, we were able to quickly determine both the mutation rate and the specificity of the mutations caused by different types of mutagens and mutagenic conditions. We also developed a PCR-based method to rapidly and robustly determine the mutation spectrum in response to various mutagenic samples in parallel. This system allows one to not only analyze the mutation specificity of various chemicals, but also to search for novel genetic elements that promote the specific mutation events. 相似文献
148.
Clever GH Kawamura W Tashiro S Shiro M Shionoya M 《Angewandte Chemie (International ed. in English)》2012,51(11):2606-2609
Neatly wrapped up: alternately stacked square-planar platinum(II) complexes inside a dinuclear coordination cage were prepared to give a discrete and soluble Pt(5) -array of the Magnus' salt type. Characterization of the complex in solution was complemented by an X-ray crystal structure of {[Pt(pyridine)(4)]? [PtCl(4)](2) @Cage}; this structure showed the linear, pentanuclear array within the cages and their circular packing into a hollow tubular superstructure. 相似文献
149.
A phenanthroline-based macrocycle 1 has been newly developed which has two chemically equivalent metal chelating sites within the spatially restricted cavity for dinuclear metal arrangement. The macrocycle 1 reacts with Zn(CF(3)CO(2))(2) or ZnCl(2) to form homodinuclear Zn(II)-complexes. A single-crystal X-ray structural analysis of the resulting Zn(2)1(CF(3)CO(2))(4) determined the complex structure in which two Zn(II) ions are bound by two phenanthroline sites and two CF(3)CO(2)(-) ions bind to each Zn(II) ion in a tetrahedral geometry. Similarly, a homodinuclear Cu(I)-macrocycle was formed from 1 and Cu(CH(3)CN)(4)BF(4). Notably, from 1 and an equimolar mixture of Cu(CH(3)CN)(4)BF(4) and Zn(CF(3)CO(2))(2), a heterodinuclear Cu(I)-Zn(II)-macrocycle was exclusively formed in high yield (>90%) because of the relatively low stability of the dinuclear Cu(I)-macrocycle. A heterodinuclear Ag(I)-Zn(II)-macrocycle was similarly formed with fairly high selectivity from a mixture of Ag(I) and Zn(II) ions. Such selective heterodinuclear metal arrangement was not observed with other combinations of M-Zn(II) (M = Li(I), Mg(II), Pd(II), Hg(II), La(III), and Tb(III)). 相似文献
150.
Jung YM Sato H Ikeda T Tashiro H Ozaki Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(8-9):1941-1945
Surface-enhanced Raman scattering (SERS) of dipping films of azobenzene-containing long-chain fatty acids, nAmH (n=8, 12, m=3, 5), on silver mirrors measured with a wide range of excitation wavelengths in the 457.9-1064 nm region is reported. The obtained Raman spectra show great SERS effect even with the 1064 nm excitation, and the excitation with 457.9, 476.5, and 488.0 nm gives surface-enhanced resonance Raman scattering (SERRS) due to the resonance effect of the symmetry-forbidden n-pi* transition of the azo group. Of particular note in the present study is that the SERS spectra with the excitation in the 532-1064 nm region yield Raman bands whose frequencies are almost identical to those bands in Raman spectra of nAmH in solid state while the SERRS spectra with the excitation in the 457.9-514.5 nm region show not only a set of bands which correspond to those of nAmH in the solid state but also a set of bands whose frequencies show a significant shift from those of the bands of nAmH in the solid state. These observations lead us to conclude that there are two kinds of molecular aggregates in the dipping films of azobenzene-containing long-chain fatty acid in which azobenzene moieties are condensed to form small bundles. 相似文献