全文获取类型
收费全文 | 389篇 |
免费 | 10篇 |
国内免费 | 3篇 |
专业分类
化学 | 284篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 57篇 |
物理学 | 52篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 2篇 |
2013年 | 18篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 16篇 |
2007年 | 15篇 |
2006年 | 18篇 |
2005年 | 16篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 21篇 |
2001年 | 11篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 16篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1935年 | 4篇 |
1933年 | 3篇 |
1931年 | 2篇 |
排序方式: 共有402条查询结果,搜索用时 15 毫秒
101.
Bardelang D Rockenbauer A Jicsinszky L Finet JP Karoui H Lambert S Marque SR Tordo P 《The Journal of organic chemistry》2006,71(20):7657-7667
236CDTIPNO, a derivative of the persistent free radical TIPNO (1,1-dimethylethyl 2-methyl-1-phenylpropyl nitroxide) covalently bound to a permethylated-beta-cyclodextrin, was prepared. Self-association of 236CDTIPNO in water was proved by solvent- and competition-dependent EPR spectroscopy experiments with 2,6-di-O-Me-beta-cyclodextrin (DIMEB) and permethylated-beta-cyclodextrin (TRIMEB) as external hosts competing for accommodation of the TIPNO moiety. Temperature-dependent EPR spectra were simulated with a novel two-dimensional (field-temperature) EPR simulation program that afforded a full determination of the thermodynamic parameters characterizing the rate constants of the self-inclusion reaction derived from Arrhenius and Eyring models. This method allows separating the line broadening effects due to relaxation from a chemical exchange, even if only the fast exchange regime is accessible experimentally. The activation parameters for the forward and backward steps were consistent with an equilibrium between a nonassociated form and a weakly associated form, with activation free enthalpies for each reaction of around 34 kJ.mol(-)(1). 相似文献
102.
Snopok B Yurchenko M Szekely L Klein G Kashuba E 《Analytical and bioanalytical chemistry》2006,386(7-8):2063-2073
Biosensor technologies based on optical readout are widely used in protein–protein interaction studies. Here we describe a
fast and simple approach to the creation of oriented interfacial architectures for surface plasmon resonance (SPR) transducers,
based on conventional biochemical procedures and custom reagents. The proposed protocol permits the oriented affinity-capture
of GST fusion proteins by a specific antibody which is bound to protein A, which in turn has been immobilized on the transducer
surface (after the surface has been modified by guanidine thiocyanate). The applicability of the method was demonstrated by
studying the interaction between retinoblastoma tumor suppressor protein (pRb) and MRS18-2 proteins. The formation of the
pRb–MRS18-2 protein complex was examined and the pRb binding site (A-box–spacer–B-box) was mapped. We have also shown that
MRS18-2, which was detected as the Epstein–Barr virus-encoded EBNA-6 binding partner using the yeast two-hybrid system, binds
to pRb in GST pull-down assays. 相似文献
103.
DiCarlo CM Compton DL Evans KO Laszlo JA 《Bioelectrochemistry (Amsterdam, Netherlands)》2006,68(2):134-143
Cytochrome c immobilized on alkylthiol self-assembled monolayers exhibits a characteristic Fe(II)/Fe(III) redox signal that is lost when exposed to ionic liquids composed of a butylimidazolium cation combined with either hexafluorophosphate or bis(trifluoromethylsulfonyl)imide anion. In this study it was shown that exposure to the aqueous solubilized ionic liquid components, butyl-, hexyl-, and octyl-imidazolium cations and hexafluorophosphate, tetrafluoroborate, and bis(trifluoromethylsulfonyl)imide anions, resulted in partial electrochemical signal loss. Absorbance and fluorescence measurements showed that signal loss due to the cationic ionic liquid component followed a different mechanism than that of the anionic component. Although a portion of the signal was recoverable, irreversible signal loss also occurred in both cases. The source of the irreversible component is suggested to be the loss of protein secondary structure through complexation between the ionic liquid components and the protein surface residues. The reversible electrochemical signal loss is likely due to interfacial interactions imposed between the electrode and the cytochrome heme group. The influence of the amount of exposed surface residues was explored with a simplified model protein, microperoxidase-11. 相似文献
104.
105.
106.
107.
Decompositions of elements into intersections of primal elements and into intersections
of p-components are studied in certain lattice-ordered commutative semigroups, by
making use of the new development in commutative ideal theory without finiteness conditions,
due to Fuchs-Heinzer-Olberding [7]. Several results concerning ideals can be phrased
as theorems in abstract ideal theory.The intersections we consider are in general not irredundant, and the associated prime
elements are not unique. However, one can establish a canonical intersection that is often
irredundant with uniquely determined associated primes. 相似文献
108.
MaoJun Guo Laszlo Varady Demosthenes Fokas Carmen Baldino Libing Yu 《Tetrahedron letters》2006,47(23):3889-3892
Aromatic bromination on various aromatic systems with different substitutions was performed in the presence of alkyl bromide and sodium hydride in DMSO. Mono-bromination on a wide range of substrates was achieved by selecting proper alkyl bromides and controlling its amount. Further bromination could happen with more active alkyl bromides and additional amount of bromides and sodium hydride. The yields ranged from moderate to excellent. In addition, reaction mechanism was postulated to explain our observations. 相似文献
109.
The K-10 bentonite clay doped with FeIII or, even better AlCl3 alone catalyse the Diels-Alder reaction between furan or dimethyl-2,5-furan and either acrolein or methyl- vinylketone. The cycloadducts are obtained with isolated yields in the range 20–81%. 相似文献
110.
Laszlo Prokai Katalin Prokai-Tatrai Emil Pop Nicholas Bodor Jozsef Lango John Roboz 《Journal of mass spectrometry : JMS》1993,28(6):707-715
Fast atom bombardment and collision-induced dissociation tandem mass spectrometry were used to study the fragmentation of quaternary pyridinium salt-type amides of tryptophan (α-amino-3-indolepropionic acid) esters and their analogs which incorporate the α-nitrogen into the quaternary pyridinium structure. By cleavage directly at the pyridine nitrogen, the 1-alkyl-substituted nicotinamides decompose exclusively to a carbocation, which then becomes the intermediate to further fragments. Rearrangement of the 3-indolepropionate-2-yl carbocations may involve a five- to seven-membered ring expansion, which generates alternative fragmentation pathways; the formation of an even-electron and a radical cation, respectively. In trigonellyl amide-type tryptophan derivatives, fragmentation of the pyridinium ion proceeds on multiple pathways induced by the positive charge which may not be localized on the quaternary nitrogen, and isomerization to a dihydropyridinyl structure is probably involved. Besides the formation of protonated nicotinamide and alkene from tryptophan amides that contain methylene or ethylene units between the amino and the quaternary pyridinium nitrogens, a fragmentation route leading to the carbocation identical with that of the 1-alkyl-substituted nicotinamides has also been revealed. 相似文献