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971.
972.
The ab initio SCF-MO-LCAO calculation of the ethylene molecule considering explicitly all valence electrons and using a minimum basis set of Slater orbitals as well as the Mulliken approximation of integrals is presented. Further, a CI calculation including all mono-excited and some di-excited configurations has been carried out. The implications of this study with respect to the validity of the — separability conditions are discussed.
Zusammenfassung Es wird eine ab initio SCF-MO-LCAO Berechnung des Äthylenmoleküls vorgelegt, in der alle Valenzelektronen in Betracht gezogen sind. Als Funktionenansatz wurde ein aus Slater-Atomeigenfunktionen bestehendes System benützt, die Atomintegrale wurden nach der Mullikenschen Näherung berechnet. Weiter wurde eine CI-Rechnung mit Berücksichtigung aller einfach angeregten und einiger doppelt angeregten Zustände angeschlossen und die Folgerungen in Bezug auf die — -Separation diskutiert.
Résumé Dans cette communication on présente les résultats d'un calcul ab initio par la méthode SCF-MO-LCAO, dans lequel on tient compte explicitement de tous les éléctrons de valence en utilisant une base minimum des orbitales de Slater et l'approximation des intégrals par Mulliken. On a aussi performé le calcul par la méthode de l'interaction des configurations avec toutes les configurations monoexcitées et quelques diexcitées. On discute les implications de cette étude en relation avec la validité des conditions de la f séparabilité.相似文献
973.
PdSCl, a Molecular Palladium(II) Disulfidechloride with Octanuclear Pd8(S2)4Cl8 Groups and with Tetra Metal-coordinated bridging Disulfide Groups Black crystals of PdSCl have been obtained by reaction of Pd with S2Cl2 in closed quartz ampoules at 200°C. The compound is to be formulated as a Palladium(II)-disulfidechloride consisting of Pd8(S2)4Cl8 molecules with approximately D4h symmetry. In the octanuclear complexes Pd atoms form a cube, where bridging disulfide groups are found in front of 4 faces and μ2?bridging Cl atoms on 8 edges. In the monoclinic crystal structure (a = 8.763(2) Å; b = 9.082(2) Å; c = 13.662(4) Å; β = 91.748(23)°; V = 1086.8 Å3; Z = 16 PdSCl; Space gr. P21/n) the molecules form a cubic closed arrangement. 相似文献
974.
Narottam Gharah Krishna Chowdhury Monika Mukherjee Ramgopal Bhattacharyya 《Transition Metal Chemistry》2008,33(5):635-642
A green heteropolyblue compound, (PPh4)4[PMo12O40] · 3DMF(1), has been synthesized from MoO3, H2O2 and H3PO4 in acetylacetone medium and crystallized from N,N-dimethylformamide. Compound 1 was characterized by analytical and spectroscopic methods, and X-ray structure analysis. The compound is a one-electron paramagnet
and shows a featureless and cubic EPR spectrum with <g> = 1.95 in DMF glass. The complex shows a Mo(V)–Mo(IV) couple, which
has been studied by cyclic voltammetric and coulometric methods. The compound acts as an efficient olefin epoxidation catalyst
with H2O2 as oxidant and NaHCO3 as co-catalyst.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
975.
van der Waals D Pugh T Khan MA Stewart AJ Johnson AL Lewis SE 《Chemistry Central journal》2011,5(1):80
ABSTRACT: We report the first synthesis of a cobalt Cp diene complex wherein the diene is derived by microbial dearomatising dihydroxylation of an aromatic ring. The complex has been characterised crystallographically and its structure is compared to that of an uncomplexed diene precursor. 相似文献
976.
977.
Gauczinski J Liu Z Zhang X Schönhoff M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(9):4267-4273
An improvement to molecular imprinting in polymers, where bulk systems often suffer from slow dynamics of release and uptake, is the formation of thin films with imprinting sites that are more rapid to access by guest molecules. Based on our previous development of surface molecular imprinting layer-by-layer (LbL) films (SMILbL), the present paper presents selective imprinted sites in a surface film on dispersed silica particles, thus designing a SMILbL system with maximized active area and in addition allowing studies with bulk techniques. The multilayer is designed to include the template during the LbL buildup and to form a cross-linked network upon UV-irradiation for enhanced stability. A theophylline moiety is grafted to poly(acrylic acid) as the template, while a UV-sensitive diazo polycation cross-links the polymers after irradiation. Electrophoretic measurements prove the successful buildup of the multilayers by an alternating sign of the zeta potential. Template release is achieved by cleavage of the grafted template. The released amount of template is quantified in solution by (1)H NMR spectra and is in good agreement with the prediction from surface coverage calculations. Rebinding studies of template to the now empty imprinted binding sites show a high affinity for a theophylline derivative with a rebound amount on the order of the original template content. In contrast to theophylline, caffeine with a very similar chemical structure-only differing in one functional group-shows very different binding properties due to a thiol moiety in the binding site. Thus, a particle system with very selective molecular imprinting sites is demonstrated. 相似文献
978.
Stela Minkovska Monika Fedieva Bojana Jeliazkova Todor Deligeorgiev 《Polyhedron》2004,23(18):3147-3153
Chelation with Al(III), Fe(II) or Cu(II) of the open photomerocyanine form obtained under steady irradiation of spiroindolinonaphthooxazines, with a hydroxyl group at the 5′ position in the naphthooxazine moiety, induces a slight hypsochromic shift of its visible absorption band and increases the lifetime of this form, slowing down its thermal bleaching in the dark (rate constant 10−3 s−1). Complexation with Al(III), Fe(II) or Cu(II) allows the spiroindolinonaphthooxazines to isomerize to their open coloured form even under dark conditions giving a complex spectroscopically identical to the photoinduced product. The activation energy of thermal complexation is independent of the metal ion which implies the ring opening as the rate determining step. 相似文献
979.
Ambarish Ray Parikshit Chandra Mandal Atish Dipankar Jana William S. Sheldrick Swastik Mondal Monika Mukherjee Mahammad Ali 《Polyhedron》2008,27(14):3112-3122
Two new copper(II) complexes, viz. [Cu(nelin)(H2O)2]2[Fe(CN)6] · 6H2O (2) and [{Cu(nelin)}2Ni(CN)4](ClO4)2 · 2H2O (3), have been synthesized using [Cu(nelin)](ClO4)2 (1) (nelin = 1,9-diamino-5-methyl-5-nitro-3,7-diazanonane) as a nitroalkyl-substituted CuIIN4 precursor, and their structures and supramolecular networks have been fully explored using the single crystal X-ray diffraction technique. The H-bonded 1D chains of 2 run along the a-axis, being generated from supramolecular synthons using cations and anions, and are further propagated into a 3D array to form irregular honeycomb-like channels which are divided into two halves, with each half accomodating a helical water chain running in opposite directions to each other. In complex 3, the trinuclear units are arranged in successive rows in a herringbone fashion and bifurcated hydrogen bonding through the uncoordinated terminals of the [Ni(CN)4]2− units give rise to a supramolecular (4,4) network. A comparison of the PXRD pattern of complex 2 and its dehydrated form indicate marked changes in the diffraction pattern with the development of a quasi glassy nature in the dehydrated form. The electrochemical properties of 1, 2 and 3 have been investigated in comparative ways using the cyclic voltammetric technique in aqueous and MeCN solutions with Ag/AgCl as a reference electrode. Electrochemical reduction generates the one-electron reduced nitro-radical anion. In water–alcohol glass at 77 K complex 2 exhibits a typical four-line hyperfine EPR spectra with g|| = 2.11, g = 2.02, A|| = 150 Oe and A = 5 Oe at ν = 9.45 MHz. 相似文献
980.
Anja These Dorina Bodi Stefan Ronczka Monika Lahrssen-Wiederholt Angelika Preiss-Weigert 《Analytical and bioanalytical chemistry》2013,405(29):9375-9383
In tandem mass spectrometry the multiple reaction monitoring (MRM) mode is normally used for targeted analysis but this mode also has the potential to screen for structural similarities of analytes. On the basis of the fact that in general similar molecular structures result in similar fragments or losses of neutrals, this approach was used for pyrrolizidine alkaloid (PA) screening but could also be easily adapted to screen for other compound classes. PA are plant toxins of which several hundred individual compounds have been identified. Our MRM screening approach uses the structural relation and similar core structure of all PA which results in a common and thus predictable mass spectrometric fragmentation behaviour. On this basis a method was developed which screens for PA structures by MRM transitions and allows the detection of each individual PA down to a low microgram per kilogram concentration range. The approach was applied to investigate plants from the families of Asteraceae (several species of Senecio and Eupatorium), Boraginaceae (Echium, Cynoglossum, Borago and Anchusa officinalis as well as Heliotropium europaeum) and Fabaceae (Crotalaria incana) for a complete qualitative and quantitative PA characterisation. All analytes that were detected as possible PA by MRM screening were further investigated by recording product ion spectra. Analytes which exhibited a typical PA fragmentation pattern were either confirmed as PA or otherwise deleted as false positive signals (false positive rate was below 10 %). Sum formulas of confirmed PA were determined by additional measurements applying high resolution mass spectrometry. In that way 121 unknown PA were identified and for the first time complete PA profiles of different PA plants were delivered. 相似文献