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81.
A reinvestigation was undertaken in order to obtain reliable data of the relative intensities of the L spectra for the elements
24 ≤ Z ≤ 33. A TAP crystal with a periodicity of 25.757 ? was used as the dispersing element. With this crystal one is able
to resolve the lines/bands Ll = L3M1, Lη = L2M1, Lα1,2 = L3M4,5, Lβ1 = L2M4, and Lβ3,4 = L1M2,3. Among the investigated elements 33As is the only one for which the energy of the lines Lα1,2 and Lβ1 is below the L3 absorption edge. For all the other elements the lines Ll, Lη, and Lα1,2 are below the L3 edge, whereas Lβ1 and Lβ3,4 are above this edge. This difference leads to effects of differential absorption, where the absorption is stronger for decreasing
line energy. For the net peak height ratio β1/α we obtained results which are of the same order of magnitude as those given by White and Johnson (W&J) in their popular
tables. But for l/α and β3,4/β1 our results show an atomic number dependence which is completely different from those given by W&J. 相似文献
82.
Thomas C. Rosen Ralf Feldmann Pascal Dünkelmann Thomas Daußmann 《Tetrahedron letters》2006,47(28):4803-4806
Perfluorinated chiral alcohols are interesting building blocks for pharmaceuticals and agrochemicals. Different chiral (R)- and (S)-configured perfluorinated alcohols were produced by asymmetric reduction of the corresponding ketones. Commercially available alcohol dehydrogenases were used as catalyst in combination with different cofactor regenerating systems. High selectivities of >99% were observed in most cases. The results also demonstrate the influence of the CF3 group on reactivity and enantioselectivity of alcohol dehydrogenases. 相似文献
83.
A. Gämann 《Helvetica chimica acta》1968,51(3):543-548
The temperature/concentration diagrams of the binary systems of HgJ2 with AsJ3, SbJ3, and BiJ3 are determined by differential-thermal analysis. In addition to the temperature of the several phase transitions the peak areas of the differential curves are evaluated as a new quantity of measurement. Eutectic systems are found in each case. 相似文献
84.
L. Hock B. Helferich K. Neumann F. Peters H. Schmidt W. Lauppe B. Roßmann 《Colloid and polymer science》1951,123(1):54-56
Ohne Zusammenfassung 相似文献
85.
The Crystal Structure of Me3SiI · β-Picoline and Me3SiI · γ-Picoline A Comparison between the Lewis-Bases Pyridine, β-Picoline, and γ-Picoline The reaction of Iodinetrimethylsilane with β- und γ-Picoline (Pic) leads to solid 1 : 1 compounds Me3SiI · β-Picoline 1 , Me3SiI · γ-Picoline 2. The reaction was performed at room temperature. Yellow single crystals were obtained by sublimation. Single crystal X-ray investigations confirm that both compounds are ionic [Me3SiPic]+I?. The comparison of β-Picoline with γ-Picoline and Pyridine (Py) demonstrates that the presence of a methyl group and also its position has no significant influence on the Si? N bond length in compound 1, 2 and on the adduct Me3SiI · Py. 相似文献
86.
Rudolf Preußmann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1974,86(21):786-786
87.
Sebastian Preiß Ayla Päpcke Lukas Burkhardt Luca Großmann Prof. Dr. Stefan Lochbrunner Prof. Dr. Matthias Bauer Prof. Dr. Till Opatz Prof. Dr. Katja Heinze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(23):5940-5949
In the context of solar-to-chemical energy conversion, inspired by natural photosynthesis, the synthesis, electrochemical properties and photoinduced electron-transfer processes of three novel zinc(II)-gold(III) bis(porphyrin) dyads [ZnII(P)–AuIII(P)]+ are presented (P: tetraaryl porphyrin). Time-resolved spectroscopic studies indicated ultrafast dynamics (k >1010 s−1) after visible-light excitation, which finally yielded a charge-shifted state [ZnII(P ⋅ +)–AuII(P)]+ featuring a gold(II) center. The lifetime of this excited state is quite long due to a comparably slow charge recombination (k ≈3×108 s−1). The [ZnII(P ⋅ +)–AuII(P)]+ charge-shifted state is reductively quenched by amines in bimolecular reactions, yielding the neutral zinc(II)–gold(II) bis(porphyrin) ZnII(P)–AuII(P). The electronic nature of this key gold(II) intermediate, prepared by chemical or photochemical reduction, is elucidated by UV/Vis, X-band EPR, gold L3-edge X-ray absorption near edge structure (XANES) and paramagnetic 1H NMR spectroscopy as well as by quantum chemical calculations. Finally, the gold(II) site in ZnII(P)–AuII(P) is thermodynamically and kinetically competent to reduce an aryl azide to the corresponding aryl amine, paving the way to catalytic applications of gold(III) porphyrins in photoredox catalysis involving the gold(III/II) redox couple. 相似文献
88.
Johanna Gra?mann Romy K. Scheerle Thomas Letzel 《Analytical and bioanalytical chemistry》2012,402(2):625-645
This review covers recent developments in mass spectrometry-based applications dealing with functional proteomics with special
emphasis on enzymology. The introduction of mass spectrometry into this research field has led to an enormous increase in
knowledge in recent years. A major challenge is the identification of “biologically active substances” in complex mixtures.
These biologically active substances are, on the one hand, potential regulators of enzymes. Elucidation of function and identity
of those regulators may be accomplished by different strategies, which are discussed in this review. The most promising approach
thereby seems to be the one-step procedure, because it enables identification of the functionality and identity of biologically
active substances in parallel and thus avoids misinterpretation. On the other hand, besides the detection of regulators, the
identification of endogenous substrates for known enzymes is an emerging research field, but in this case studies are quite
rare. Moreover, the term biologically active substances may also encompass proteins with diverse biological functions. Elucidation
of the functionality of those—so far unknown—proteins in complex mixtures is another branch of functional proteomics and those
investigations will also be discussed in this review. 相似文献
89.
90.
A series of halogenated nucleobase derivatives 1–4 is reported to yield solvent-free (2) and DMSO solvated crystals (1, 3, 4) on the crystallization from DMSO with one of them (4) containing an additional molecule of water. The molecular and crystal structures are described and comparatively discussed
with reference to previous results on related compounds. The molecule of 1 is planar, molecules of 2 and 3 show syn alignment with reference to the heterocyclic ring and common C2′-endo conformation of the ribose residue, while 4 is also syn aligned but C4′-exo in the sugar conformation. The packing structures reveal typical aggregations created via networks of hydrogen bonds. These
involve conventional N–H···N, N–H···O and O–H···O interactions between nucleobase and ribose units as well as solvent molecules,
additionally supported by weak C–H···O contacts but excluding the participation of halogen···halogen interactions as well
as halogen···heteroatom contacts in the supramolecular structure formation. 相似文献