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421.
Cobalt(II) and copper(II) complexes with 1-allyl-2-methylimidazole (L), of general formula [ML2(NO3)2], have been prepared in the solid state. The compounds were characterised by structural, spectroscopic and magnetic measurements. The metal ions in both six coordinate complexes are surrounded by two nitrogen atoms of the imidazole rings and four oxygen atoms of the chelating nitrato group (the CoN2O4 and CuN2O4 chromophores). The structure of both chromophores is described by a very distorted tetragonal bipyramid. The formation of successive complexes of the azole with Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ in aqueous solution was followed potentiometrically. An irregularity in the Kn constants of successive Co2+ and Zn2+ complexes suggests a change in the coordination sphere of the central ions from octahedral to tetrahedral. With the Co2+–1-allyl-2-methylimidazole system, the change has been proven by inspection of the visible absorption spectra. 相似文献
422.
Krystyna?Cie?laEmail author Ann-Charlotte?Eliasson 《Journal of Thermal Analysis and Calorimetry》2005,79(1):19-27
DSC studies were carried out in the heating-cooling cycles for non-irradiated and irradiated with -rays (60Co) using 30 kGy dose wheat flour. The differences between gelatinisation and reversible transition of amylose-lipid complexes occurring in suspensions of non-irradiated and the irradiated flour (characterized by a dry matter to water ratio of 1:1 and 1:3) depend on the conditions applied in DSC measurements (concentration, heating/cooling rate) and on the preceding treatment of samples. An essential decrease in the temperature of amylose-lipid complex transition was discovered after irradiation. Retrogradation is inhibited in the dense gels of the irradiated samples as compared to the initial ones. The results are discussed in terms of radiation-induced destruction of the polysaccharide chains and lipid modification. 相似文献
423.
A simple method for the determination of thiuram disulphides was developed. These compounds induce the iodine-azide reaction after cleavage of the SS bond. The consumption of iodine in this reaction is proportional to the amount of the inductor. Inducing properties of the compounds examined were estimated from an induction coefficient ([I]/[S]) which indicates how many times the consumption of iodine in the induced reaction is higher than that in the iodimetric reaction. Under analytically optimum conditions the induction coefficients are in the range 176–211 for eight thiuram disulphides. The identical behaviour of thiuram disulphides in the induced reaction and of the corresponding dithiocarbamates allows the analysis of their mixture in the same sample. The method is sensitive, selective, accurate, cheap and rapid. Other compounds that induce the iodine-azide reaction interfere. 相似文献
424.
Krystyna Schreiber-Pawlak W. Reichert C. Freiburg 《Fresenius' Journal of Analytical Chemistry》1974,270(3):198-200
Summary Semiconductors of the composition Cd
v
Hg1–v
Se and Cd
x
Hg1–x
Te are gaining growing industrial interest. The energy gap between the bands of such systems depends significantly on the magnitude of the mole fractions v and x. X-ray fluorescence analysis of acid solutions of these crystals is a simple and precise procedure to determine the stoichiometry. Sample preparation, calibration series and results are discussed.
Bestimmung der Stöchiometrie von Halbleitersystemen des Typs CdvHg1–vSe und CdxHg1–xTe, durch Röntgenfluorescenz-Spektrometrie
Zusammenfassung Halbleiter der Typen Cd v Hg1–v Se und Cd x Hg1–x Te gewinnen zunehmend industrielles Interesse. Der Energieabstand der Bänder in solchen Systemen hängt entscheidend von der Größe der Molenbrüche v und x ab. Ein einfaches und sicheres Analysenverfahren zur Ermittlung der Stöchiometrie ist die Röntgenfluorescenzanalyse von sauren Lösungen dieser Kristalle. Die Probenvorbereitung, Eichreihen und Resultate werden diskutiert.
Delegated to Central Institute of Analytical Chemistry, Nuclear Research Establishment (KFA), Jülich, FRG. 相似文献
425.
The synthesis of poly(methyl acrylate)-block-poly(gamma-benzyl-L-glutamate) (PMA-b-PBLG) diblock copolymers, using atom-transfer radical polymerization (ATRP) of methyl acrylate and living polymerization of gamma-benzyl-L-glutamate-N-carboxyanhydride (Glu-NCA) is described. Amido-amidate nickelacycle end groups were incorporated onto amino-terminated poly(methyl acrylates), and the resulting complexes were successfully used as macroinitiators for the growth of polypeptide segments. This method allows the controlled preparation of polypeptide-block-poly(methyl acrylate) diblock architectures with control over polypeptide chain length and without the formation of homopolypeptide contaminants. 相似文献
426.
Reed BM Kovalchuk I Kushnarenko S Meier-Dinkel A Schoenweiss K Pluta S Straczynska K Benson EE 《Cryo letters》2004,25(5):341-352
Cryopreservation of plant tissues in liquid nitrogen is now used for long-term conservation of vegetatively-propagated crops. Development of standard techniques for cryopreservation is important to the international plant-conservation community for successful implementation of storage protocols in diverse and internationally dispersed laboratories. Evaluation of the critical points of each preservation technique will greatly assist in developing and validating internationally-used cryopreservation protocols. The goals of this project were to assess critical points of two major cryopreservation techniques (PVS2 vitrification and encapsulation dehydration) during their transfer to international laboratories; analyze post-storage viability for each technique and location; and develop recommendations based on the assessments and data from the participating laboratories. Investigators from Germany, Kazakhstan, Poland and UK participated in a 2-week training workshop in cryopreservation methods after which the techniques were tested in the home laboratories of the participants. After one-year site visits by the technology trainers identified critical points in the protocols. Critical points were identified as 1) Cryogenic (cryoprotection, LN exposure, rewarming); 2) Non-cryogenic (plant health status, pre- and post-storage culture); 3) Operational (skills transfer, training, interpretation of procedures); 4) Facility (growth room, ambient conditions, media preparation, equipment). The most critical factors in all laboratories were culture health, operator skills and experience, and clarification of the technical details of the procedures. Final results showed that correction of critical factors improved the post-storage recovery in all the laboratories. 相似文献
427.
We present a rounding error analysis of Higham's scaled method for computing the polar decomposition of a nonsingular complex matrix. Under certain natural conditions we prove that the method computes acceptable polar factors. 相似文献
428.
Imre Bárány Krystyna Kuperberg Tudor Zamfirescu 《Discrete and Computational Geometry》2003,30(2):167-176
This paper gives a partial confirmation of a conjecture of
Agarwal, Har-Peled, Sharir, and Varadarajan that the total
curvature of a
shortest path on the boundary of a convex polyhedron in R
3
cannot be
arbitrarily large. It is shown here that the conjecture holds for a class of
polytopes
for which the ratio of the radii of the circumscribed and inscribed ball is
bounded. On
the other hand, an example is constructed to show that the total curvature
of a
shortest path on the boundary of a convex polyhedron in R
3 can
exceed 2. Another example shows that the spiralling number of a
shortest path on the boundary of a convex polyhedron can be arbitrarily
large. 相似文献
429.
John E. Drake Krystyna Gorzelska Reinhard Helbing Reint Eujen 《Journal of Electron Spectroscopy and Related Phenomena》1982,26(1):19-30
He(I), He(II) and X-ray-excited photoelectron spectra of the trifluoromethylgermanes (CF3)4?nGeHn(n = 1–3) are reported. Assignments of the valence region are made on the basis of semi-empirical CNDO/2 calculations, comparisons with the spectra of related series of molecules, band shapes, and relative-intensity changes between features in the He(I) and He(II) spectra. Core-level binding energies are also compared with those of related species, and the usefulness of CNDO/2 and EESOP charge calculations is examined. 相似文献
430.
Józef Lipiński Henryk Chojnacki Zbigniew R. Grabowski Krystyna Rotkiewicz 《Chemical physics letters》1980,70(3):449-453
The energies of the low lying electronic states of p-cyano-N,N-dimethylaniline (CDMA) in its planar and in 90° twisted conformation have been calculated using the modified INDO method. Solvent effects have been taken into account. The results agree reasonably well with the experimental data and support the hypothesis of the dual fluorescence of CDMA as being related to the intramolecular rotation of the N(CH3)2 group, with a decisive role of the solvent polarity. 相似文献