全文获取类型
收费全文 | 157篇 |
免费 | 2篇 |
专业分类
化学 | 103篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 25篇 |
物理学 | 26篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2000年 | 10篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1991年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 7篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 4篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1934年 | 2篇 |
1932年 | 2篇 |
1888年 | 3篇 |
1887年 | 4篇 |
1885年 | 1篇 |
1884年 | 1篇 |
1883年 | 6篇 |
1870年 | 2篇 |
1864年 | 1篇 |
1863年 | 2篇 |
1862年 | 2篇 |
排序方式: 共有159条查询结果,搜索用时 15 毫秒
1.
Polymers containing intact lactone groups are a new class of macromolecules with reactive groups, which are relatively easy to obtain by polymerization, polycondensation and polyaddition, as well as by reactions on existing macromolecules. Polymers with β-lactone Groups in particular can enter into numerous addition reactions, which can be used, for example, to obtain macromolecules containing hydroxy acid or amino acid groupings. The reactions proceed under mild conditions, and can even be carried out in aqueous media, frequently giving water-soluble polymers. The polymers can be cross-linked at low temperatures, even from the aqueous phase, by the addition of bifunctional or oligofunctional reagents. Polymers containing β-lactone groups can also be used as a basis for graft co-polymers; polyester or polyether branches can be grafted on, depending on whether monomeric lactones or monomeric epoxides are used. 相似文献
2.
3.
B. Damaskin S. Karpov S. Dyatkina U. Palm M. Salve 《Journal of Electroanalytical Chemistry》1982,136(2):217-227
Theoretical analysis of the double-layer model has been carried out in the presence of the specific adsorption of organic cations accompanied by considerable increase of the inner-layer dimensions. The formulae for calculation of the differential capacity curves of an electrode have been derived. A flat minimum at high negative charges, caused by the diffuse structure of the double layer, has been predicted on the capacity curves. The presence of such minima has been verified experimentally on the mercury and bismuth electrodes. By computer calculation it has been shown that, although. relatively good agreement of the theoretically calculated capacity curves with the experimental curves could he obtained, a physically unrealistic interaction parameter of the specifically adsorbed ions had to be used. As demonstrated, this result is a result of the double-layer model assuming linear dependence of the inner-layer integral capacity of the surface coverage and its independence from the electrode charge. 相似文献
4.
Alexander Goerke Gregor Leipelt Hartmut Palm C. P. Schulz I. V. Hertel 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,32(4):311-320
The first reactive differential scattering study for atomic clusters is reported. Oxidation of Na
x
(x8) with O2 is investigated in a crossed beam apparatus. Sodium oxide (Na
n
O,n4) and sodium dioxide (Na
n
O2,n6) are produced with a total reactive cross section from 50 to 80 Å2, depending on the cluster size. The excess energies for these reactions are estimated by an SCF type ab initio calculation and range from 0.5 to 5 eV. The large cross section may then be understood quantitatively in terms of a harpooning mechanism as a first step in the reaction path. Angular distributions have been determined for the most abundant products, showing strong forward scattering. Two different schemes are discussed for the reaction: while the dioxides Na
n
O2 may be formed by an evaporative cooling process from a highly excited collision complex, formation of Na
n
O appears to originate from a direct process. In both cases the experimental data suggest that most of the exothermicity remains in the reaction products. 相似文献
5.
A simple and rapid single-step method is presented to fabricate an enzyme reactor using trypsin immobilized on a macroporous polymer monolith. A reactor produced in a capillary format is ready to use within 1 h of preparation. The monomers making up the monolith, including N-acryloxysuccinimide for covalent immobilization of the enzyme, are mixed with trypsin and introduced into the column by capillary force for polymerization/immobilization. The enzyme activity from column-to-column is reproducible below 5% relative standard deviation (RSD), while the reactor is durable for at least 20 weeks when stored at room temperature. The apparent kinetic constants V(max) and K(m) are of value similar to those obtained by free trypsin in solution. Enzymatic digestion of proteins was shown to be feasible on a time-scale of seconds and submicromolar concentrations enabling peptide mass mapping by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. 相似文献
6.
P. Laggner O. Kratky W. H. Palm A. Holasek 《Monatshefte für Chemie / Chemical Monthly》1971,102(6):1729-1744
Zusammenfassung Schweineserum-Albumin wurde nach sorgfältiger Reinigung bei den pH-Werten 7,0, 5,1 und 3,7 mit Hilfe der Röntgenkleinwinkelstreuung untersucht. Es wurde bei allen Messungen praktisch dasselbe Molekulargewicht gefunden: der Mittelwert liegt bei 70 300±2 500. Die Ermittlung der Streumassenradien ergab bei pH 7,0 und pH 5,1 ähnliche Werte (33,0 Å bzw. 31,1 Å), bei pH 3,7 dagegen einen Wert von 37,8 Å. Die Formbestimmung ergab bei pH 7,0 und pH 5,1 identische Achsenverhältnisse (0,75 : 1 : 2), während bei pH 3,7 ein solches von 0,2 : 1 : 1 gefunden wurde.
Herrn Prof. Dr.H. Nowotny gewidmet. 相似文献
X-ray small-angle scattering investigations on solutions of porcine serum albumin at differentpH-values
Higly purified samples of porcine serum albumin were measured by the X-ray small-angle scattering method at pH 7.0, 5.1, and 3.7. The molecular weight is found to be the same in all three cases: the mean value is 70 300±2 500. The radius of gyration is 31.1 Å and 33.0 Å at pH 5.1 and 7.0 resp., whereas at pH 3.7 a value of 37.8 Å is found. The determination of the molecular conformation yields a similar axial ratio at pH 5.1 and pH 7.0 of 0.75 : 1 : 2; at pH 3,7 we find an axial ratio of 0.2 : 1 : 1 to be consistent with the scattering curves.
Herrn Prof. Dr.H. Nowotny gewidmet. 相似文献
7.
Fused-silica capillaries chemically derivatized with silane/poly(vinylpyrrolidone) (PVP) or dynamically modified with plexiglas [poly(methyl methacrylate)] were prepared and evaluated with regard to column stability and separation performance for capillary isoelectric focusing of standard proteins. The PVP coating showed the better stability and was good for at least 100 runs while the plexiglas coating started to deteriorate after about 30 runs. The time spent for the plexiglas coating is about 40 minutes while the PVP coating requires two days. The migration time reproducibility was better with the PVP capillary (RSD 0.7-1.6%, n = 5) compared to the plexiglas-coated column (RSD 1.2-2.9%, n = 5) while peak area and height varied over a similar interval (RSD 2-28.1% area; 0.9-22.7% height, n = 5). The two most consistent proteins in this evaluation, viz. myoglobin A and carbonic anhydrase II, showed linear dynamic ranges between 5-150 and 5-50 microg/mL, and limits of detections at 2 and 1 microg/mL, respectively, employing UV detection at 280 nm. 相似文献
8.
Enzymatic Conversion of Flavonoids using Bacterial Chalcone Isomerase and Enoate Reductase 下载免费PDF全文
Dipl.‐Biol. Mechthild Gall Dipl.‐Biochem. Maren Thomsen Dipl.‐Biochem. Christin Peters Dr. Ioannis V. Pavlidis M. Sc. Patrick Jonczyk M. Sc. Philipp P. Grünert Dr. Sascha Beutel Prof. Dr. Thomas Scheper Egon Gross Dr. Michael Backes Dr. Torsten Geißler Dr. Jakob P. Ley Dr. Jens‐Michael Hilmer Dr. Gerhard Krammer Dr. Gottfried J. Palm Prof. Dr. Winfried Hinrichs Prof. Dr. Uwe T. Bornscheuer 《Angewandte Chemie (International ed. in English)》2014,53(5):1439-1442
Flavonoids are a large group of plant secondary metabolites with a variety of biological properties and are therefore of interest to many scientists, as they can lead to industrially interesting intermediates. The anaerobic gut bacterium Eubacterium ramulus can catabolize flavonoids, but until now, the pathway has not been experimentally confirmed. In the present work, a chalcone isomerase (CHI) and an enoate reductase (ERED) could be identified through whole genome sequencing and gene motif search. These two enzymes were successfully cloned and expressed in Escherichia coli in their active form, even under aerobic conditions. The catabolic pathway of E. ramulus was confirmed by biotransformations of flavanones into dihydrochalcones. The engineered E. coli strain that expresses both enzymes was used for the conversion of several flavanones, underlining the applicability of this biocatalytic cascade reaction. 相似文献
9.
10.
Olaf Kühl Stephan Millinghaus Gottfried J. Palm 《Central European Journal of Chemistry》2011,9(4):706-711
Starting from the paddlewheel complex copper(II)acetate, the green N-methylimidazole adduct of copper(II)acetate is formed
and transformed into the monomeric and dimeric N-methylimidazole adducts of copper(II)acetate [Cu(C4H6N2)2(CH3COO)2]n·xH2O (n = 1,2; x = 0, 6). The formation of the blue dimer or the purple monomer depends on the solvent and the presence or absence
of water. 相似文献