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排序方式: 共有1008条查询结果,搜索用时 31 毫秒
31.
CF3I(NO3)2 is formed from the reactions of CF3IF2 or CF3IO with N2O5 as well as CF3I with ClNO3. During the reactions of CF3IF2 with N2O5 or CF3I with ClNO3 the intermediate products CF3IF(NO3) or CF3ICl(NO3) can be identified. The preparations, properties, 19F-nmr spectra and the thermal decomposition of CF3I(NO3)2 are described. 相似文献
32.
Kinetic investigations of thermo-controlled two-step reactions between an uretdione cross-linker and OH-groups are undertaken. Non-isothermal DSC measurements are chosen for the determination of the kinetic parameters (E, A, n) using of THERMOKINETICS software. The system can be described very accurately with a four-step kinetic model of consecutive reactions. On the basis of the kinetic model and parameters the realization of the first reaction step, which is the formation of the allophanate network is simulated. Finally, the result of the calculated progress of the reaction is evaluated by FT-IR and isothermal DSC measurements. 相似文献
33.
Xiangbing Zeng Silvio Poppe Anne Lehmann Marko Prehm Changlong Chen Feng Liu Huanjun Lu Goran Ungar Carsten Tschierske 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7453-7457
The first single‐diamond cubic phase in a liquid crystal is reported. This skeletal structure with the space group is formed by self‐assembly of bolaamphiphiles with swallow‐tailed lateral chains. It consists of bundles of π‐conjugated p‐terphenyl rods fused into an infinite network by hydrogen‐bonded spheres at tetrahedral four‐way junctions. We also present a quantitative model relating molecular architecture to the space‐filling requirements of six possible bicontinuous cubic phases, that is, the single‐ and double‐network versions of gyroid, diamond, and “plumber′s nightmare”. 相似文献
34.
G. Lehmann und T. Bruhn 《Fresenius' Journal of Analytical Chemistry》1968,243(1):300-314
Zusammenfassung Ein Verfahren zur quantitativen Bestimmung der Ascorbinsäure und Dehydroascorbinsäure nach der Hydroxamatmethode wird beschrieben. Das Verfahren gestattet die Erfassung von Ascorbinsäure und Dehydroascorbinsäure in einer Reaktion, wobei in saurer Lösung beständige Eisen(III)-hydroxamatkomplexe bei 500 nm photometrisch ausgewertet werden können. Die Methode ist leicht durchführbar und nicht so störanfällig wie andere Nachweise; sie kann auch zur qualitativen Probe z. B. auf der Dünnschichtplatte herangezogen werden, wenn Ascorbinsäure neben anderen Carbonsäuren nachzuweisen ist.Es wird ferner die dünnschicht-chromatographische Trennung auf Celluloseschichten der Hydroxamsäuren, die aus der Ascorbinsäure und Dehydroascorbinsäure entstehen, beschrieben.
Unserem verehrten Lehrer, Herrn Prof. Dr. O. Neunhoeffer, danken wir für sein stetiges Interesse an der Arbeit und seine anregenden Diskussionen, Herrn Prof. Dr. B. Eistert für wertvolle Hinweise und Unterstützung durch Institutsmittel.
Herrn Prof. Dr. B. Eistert zum 65. Geburtstag gewidmet.
Auszug aus der Diplomarbeit von T. Bruhn: Bestimmung der Ascorbinsäure mit Hilfe ihrer Hydroxylaminoderivate, Saarbrücken 1968. 相似文献
On the behaviour of Ascorbic acid towards hydroxylamine, a contribution to the analysis of vitamin C
A spectrometric method is presented for the quantitative determination of 0.5–5 mg/100 ml of ascorbic and dehydroascorbic acids. It is based on the formation of hydroxamates by reaction with hydroxylamine. The conditions and the application of this method are discussed. Colouring matter and phenolic compounds, which can present difficulty in the photometric measurement, are eliminated by treatment with polyamide powder. Furthermore, the separation of the hydroxamic acid derivatives of ascorbic and dehydroascorbic acids by thinlayer chromatography on cellulose is described.
Unserem verehrten Lehrer, Herrn Prof. Dr. O. Neunhoeffer, danken wir für sein stetiges Interesse an der Arbeit und seine anregenden Diskussionen, Herrn Prof. Dr. B. Eistert für wertvolle Hinweise und Unterstützung durch Institutsmittel.
Herrn Prof. Dr. B. Eistert zum 65. Geburtstag gewidmet.
Auszug aus der Diplomarbeit von T. Bruhn: Bestimmung der Ascorbinsäure mit Hilfe ihrer Hydroxylaminoderivate, Saarbrücken 1968. 相似文献
35.
The deformation processes in impact-modified PMMA, which deforms homogeneously, were determined by means of the stress/strain experiment (, ) with simultaneous lateral strain measurement (lat) in a wide range of strain rates () up to 105%/min (impact stress). The elastic, plastic cavitation and plastic shear processes were determined as a function of strain. Therefore we calculated the elastic strain (
el), the elastic volume expansion (
vol el), the cavitation strain (
cav), which is identical with the plastic volume expansion (
vol pl), the shear strain (
sh) and the energy densities (Wel, Wcav, Wsh) related to these three processes.For strains of 3 % onward it was found that plastic shear processes and plastic cavitation processes are responsible for a partial loss of elastically stored energy. Both plastic processes turn out to be mostly anelastic deformations, their amount depending strongly on the strain rate. The contributions of the processes to the total deformation of the unmodified PMMA in its strain range are similar to those of the impact-modified PMMA, and the high impact strength is caused by a shift of the catastrophic rupture to very high strains. 相似文献
36.
Andreas?HeintzEmail author Dagmar?Klasen Jochen?K.?Lehmann Christiane?Wertz 《Journal of solution chemistry》2005,34(10):1135-1144
Experimental densities were measured for the system 1-methyl-3-octyl-imidazolium tetrafluoroborate [OMIM][BF4] + butan-1-ol, + pentan-1-ol at 298.15 K and ambient pressure using a vibrating tube densimeter, taking into account the
influence of the viscosity correction. Excess molar volumes VE have been determined. VE is quite small and negative in the alcohol-rich range of the mixture composition and positive in the alcohol-poor range.
LLE data of [OMIM][BF4] + pentan-1-ol have been measured using a laser light scattering cell for detecting cloud points at different compositions
in the temperature range of 282–292 K. A miscibility gap with an upper critical solution temperature (UCST) of 292 K has been
found. 相似文献
37.
The post-translational modifications of the 96 kDa protein dynamin A from Dictyostelium discoideum were analyzed using Q-TOF mass spectrometry. The accurate molecular mass of the intact protein revealed a covalent modification causing an additional mass of 42 Da. The modification could be identified as N-terminal acetylation by tandem mass spectrometry. Extracted ion chromatograms for the a(1) and b(1) ion of the tryptic T1 peptide were used to detect the acetylated peptide within 54 nanoelectrospray ionization tandem mass spectra. Owing to the accurate molecular mass of the intact protein, additional covalent modifications could be excluded. In addition to the covalent modification, the domain structure of dynamin A was determined by applying a combination of limited proteolysis, sodium dodecylsulfate polyacrylamide gel electrophoresis, automated tandem mass spectrometry and protein database searching. 相似文献
38.
Kremzow D Seidel G Lehmann CW Fürstner A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(6):1833-1853
Oxidative insertion of [Pd(PPh3)4] or [Ni(cod)2]/PPh3 into the C-Cl bond of various 2-chloroimidazolinium- and other -amidinium salts affords metal-diaminocarbene complexes in good to excellent yields. This procedure is complementary to existing methodology in which the central metal does not change its oxidation state, and therefore allows to incorporate carbene fragments that are difficult to access otherwise. The preparation of a variety of achiral as well as enantiomerically pure, chiral metal-NHC complexes (NHC = N-heterocyclic carbene) and metal complexes with acyclic diaminocarbene ligands illustrates this aspect. Furthermore it is shown that oxidative insertion also paves a way to prototype Fischer carbenes of Pd(II). Since the required starting materials are readily available from urea- or thiourea derivatives, this novel approach allows for substantial structural variations of the ligand backbone. The catalytic performance of the resulting library of nickel- and palladium-carbene complexes has been evaluated by applications to prototype Suzuki-, Heck-, and Kumada-Corriu cross-coupling reactions as well as Buchwald-Hartwig aminations. It was found that even Fischer carbenes show appreciable catalytic activity. Moreover, representative examples of all types of neutral and cationic metal-carbene complexes formed in this study have been characterized by X-ray crystallography. 相似文献
39.
Obrecht D Altorfer M Lehmann C Schönholzer P Müller K 《The Journal of organic chemistry》1996,61(12):4080-4086
A novel strategy for the synthesis of (R)- and (S)-alpha-methyl(alkyl)serine-containing peptides is presented. Using (S)-phenylalanine cyclohexylamide 6 as chiral auxiliary, the optically pure azlactones (R)- and (S)-2 were synthesized via a novel azlactone/oxazoline interconversion reaction (Figures 3 and 6). These azlactones constitute fully protected and activated synthetic equivalents of (R)- and (S)-alpha-methylserine and can be directly incorporated into peptides without further protective group manipulations. Like other alpha,alpha-dialkylated glycines, optically pure alpha-alkylserines can be used to stabilize beta-turn and alpha-helical conformations in short peptides. 相似文献
40.
In contrast to the N-heterocyclic carbene (NHC) 1, the homologous N-heterocyclic silylene (NHS) 4 acts as a bridging ligand to Pd(0), giving rise to the dinuclear complex 5 which is catalytically active in Suzuki reactions. 相似文献