全文获取类型
收费全文 | 366篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 305篇 |
晶体学 | 7篇 |
数学 | 35篇 |
物理学 | 28篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 10篇 |
2014年 | 8篇 |
2013年 | 8篇 |
2012年 | 20篇 |
2011年 | 33篇 |
2010年 | 13篇 |
2009年 | 21篇 |
2008年 | 21篇 |
2007年 | 25篇 |
2006年 | 18篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1954年 | 4篇 |
排序方式: 共有375条查询结果,搜索用时 15 毫秒
121.
A. V. G. Netto Regina C. G. Frem A. E. Mauro Marisa S. Crespi H. E. Zorel Jr 《Journal of Thermal Analysis and Calorimetry》2007,87(3):789-792
Synthesis, spectroscopic characterization
and thermal behavior of pyrazolate-bridged palladium complexes [Pd(μ-Pz)2]n
(1), [Pd(μ-mPz)2]n
(2), [Pd(μ-dmPz)2]n
(3), [Pd(μ-IPz)2]n
(4) {pyrazolate (Pz–),
4-methylpyrazolate (mPz–), 3,5-dimethylpyrazolate
(dmPz–), 4-iodopyrazolate (IPz–)}
have been described in this work. The exobidentate coordination mode of pyrazolato
ligands in 1–4
was inferred on basis of IR spectroscopic evidences. TG investigations indicated
that the introduction of substituents at the 4 position in the pyrazolyl moiety
into coordination polymers do not affect significantly their thermal stability,
whereas at the 3 and 5 position reduced the stability of the main chain. Metal
palladium was the final product of the thermal decompositions, which was identified
by X-ray powder diffraction. 相似文献
122.
Tejel C Villarroya BE Ciriano MA Oro LA Lanfranchi M Tiripicchio A Tiripicchio-Camellini M 《Inorganic chemistry》1996,35(15):4360-4368
Reactions of [M(2)(&mgr;-Cl)(2)(cod)(2)] (cod = 1,5-cyclooctadiene, M = Rh, Ir) with benzimidazole-2-thiol (H(2)Bzimt) afford the mononuclear complexes [MCl(H(2)Bzimt)(cod)] (M = Rh (1), Ir (2)) for which a S-coordination of the ligand is proposed based on their spectroscopic data. The dinuclear complexes [M(2)(&mgr;-HBzimt)(2)(cod)(2)] (M = Rh (3), Ir (4)) are isolated from the reaction of [M(acac)(cod)] and benzimidazole-2-thiol. They contain the monodeprotonated ligand (HBzimt(-)) bridging the two metals in a &mgr;(2)-(1kappaN,2kappaS) coordination mode and in a relative cis,cis-HT arrangement. Complexes 3 and 4 react with the appropriate species [M(cod)(Me(2)CO)(2)](+) to afford the trinuclear cationic aggregates [M(3)(&mgr;-HBzimt)(2)(cod)(3)](+) (M = Rh (5), Ir (6)) and with the [M'(2)(&mgr;-OMe)(2)(cod)(2)] compounds to give the homo- and heterotetranuclear complexes [MM'(&mgr;-Bzimt)(cod)(2)](2) (M = M' = Rh (7), Ir (8); M = Ir, M' = Rh (9)) containing the dideprotonated ligand (Bzimt(2)(-)). The trinuclear neutral complexes [M(3)(&mgr;-Bzimt)(&mgr;-HBzimt)(cod)(3)] are intermediates detected in the synthesis of the tetranuclear complexes. Protonation of 9 with HBF(4) gives the unsymmetrical complex [Ir(2)Rh(&mgr;-HBzimt)(2)(cod)(3)]BF(4) (10). This reaction involves the protonation of the bridging ligands followed by the removal of one "Rh(cod)" moiety to give a single isomer. The molecular structure of [Rh(2)(&mgr;-Bzimt)(cod)(2)](2) (7) has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P2(1)/n, a = 20.173(5) ?, b = 42.076(8) ?, c = 10.983(3) ?, beta = 93.32(2) degrees, Z = 8, 7145 reflections, R = 0.0622, and R(w) = 0.0779. The complete assignment of the resonances of the (1)H NMR spectra of the complexes 3, 4, and 7-9 was carried out by selective decoupling, NOE, and H,H-COSY experiments. The differences in the chemical shifts of the olefinic protons are discussed on the basis of steric and magnetic anisotropy effects. 相似文献
123.
Thaddeus C. Ezeji Marisa Groberg Nasib Qureshi Hans P. Blaschek 《Applied biochemistry and biotechnology》2003,106(1-3):375-382
Acetone, butanol, ethanol (ABE, or solvents) were produced from starch-based packing peanuts in batch and continuous reactors.
In a batch reactor, 18.9 g/L of total ABE was produced from 80 g/L packing peanuts in 110 h of fermentation. The initial and
final starch concentrations were 69.6 and 11.1 g/L, respectively. In this fermentation, ABE yield and productivity of 0.32
and 0.17 g/(L·h) were obtained, respectively. Compared to the batch fermentation, continuous fermentation of 40 g/L of starch-based
packing peanuts in P2 medium resulted in a maximum solvent production of 8.4 g/L at a dilution rate of 0.033 h−1. This resulted in a productivity of 0.27 g/(L·h). However, the reactor was not stable and fermentation deteriorated with
time. Continuous fermentation of 35 g/L of starch solution resulted in a similar performance. These studies were performed
in a vertical column reactor using Clostridium beijerinckii BA101 and P2 medium. It is anticipated that prolonged exposure of culture to acrylamide, which is formed during boiling/autoclaving
of starch, affects the fermentation negatively. 相似文献
124.
Giovanna Gasparri Fava Marisa Belicchi Ferrari Giorgio Pelosi Franca Zanardi Giovanni Casiraghi Gloria Rassu 《Journal of chemical crystallography》1996,26(7):509-513
The structure of 2,3-dideoxy-4-thio-d-arabino-heptonic acid 1,4-lactone has been determined by X-ray diffraction. Crystals of the compound are orthorhombic, space groupP212121, with cell dimensionsa=11.555(5),b=10.451(5),c=9.604(5) Å, andZ=4. The diffraction experiment has allowed to assign the absolute configuration (4R, 5R, 6R) to the chiral centers of the molecule. 相似文献
125.
126.
127.
128.
Fay JP Guaita MS Danelón JL Chifflet S Wawrzkiewicz M Fernández HM Ross DA 《Journal of AOAC International》2005,88(4):995-997
The objective of this work was to compare the traditional Van Soest's procedure to analyze neutral detergent fibers (NDF) and acid detergent fibers (ADF) using filtering crucibles (VS) with a semiautomatic method which uses filter bags in an ANKOM Technology Corp. instrument (ANK). Nine ruminant feeds widely used in the temperate region of Argentina were analyzed: soybean meal expeller, alfalfa, pasture silage, ryegrass, corn silage, weeping lovegrass, tall wheatgrass, guinea grass, and barley grass. Four runs were done for each technique and feed. The comparison of ADF and NDF means by the means test for paired samples showed no significant differences between techniques (alpha = 0.01). The variability among runs was greater with the VS method than the ANK, both for NDF, standard deviation (SD) = 0.71 vs 0.39, and for ADF, SD = 0.83 vs 0.56, but the differences were not significant. The linear regressions were VS = 1.43 + 0.95 ANK; R2 = 0.99, and VS = 0.53 + 0.98 ANK; R2 = 0.99 for NDF and ADF, respectively, which indicated a strong linear relationship among the results of both procedures. It was concluded that the ANK procedure gave results comparable to those of the VS method when ruminant feeds from the temperate region of Argentina were analyzed. 相似文献
129.
130.