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911.
Zusammenfassung Versuche, von o-Benzochinolacetaten ausgehend die hydroaromatischen (primären) Additionsprodukte derMichael-Reaktion zu erhalten, hatten bisher nur bei Ia und Ib mit Malonsäuredinitril Erfolg. Mit p-Benzochinolacetat VI gelingt die Darstellung der primären Additionsprodukte auch mit anderen Reaktionskomponenten, wie z. B. Malonsäurediäthylester. *** DIRECT SUPPORT *** A3615076 00007 相似文献
912.
Bunyard WC Kadla JF DeYoung J DeSimone JM 《Journal of the American Chemical Society》2001,123(30):7199-7206
The thermal decomposition of the free-radical initiator bis(perfluoro-2-N-propoxyprionyl) peroxide (BPPP) was studied in dense carbon dioxide and a series of fluorinated solvents. For the fluorinated solvents, the observed first-order decomposition rate constants, k(obs), increased with decreasing solvent viscosity, suggesting a single-bond decomposition mechanism. The k(obs) values are comparatively larger in dense carbon dioxide and similar to the "zero-viscosity" rate constants extrapolated from the decomposition kinetics in the fluorinated solvents. The decomposition activation parameters demonstrate a compensation behavior of the activation enthalpy with the activation entropy upon change in solvent viscosity. Comparison of the change in activation parameter values upon change in solvent viscosity for BPPP with two additional initiators, acetyl peroxide (AP) and trifluoroacetyl peroxide (TFAP), further suggests that carbon dioxide exerts a very minimal influence on the decomposition mechanism of these initiators through solvent-cage effects. 相似文献
913.
The solvation parameter model is used to construct equations for the estimation of the non-specific toxicity of neutral organic compounds to five organisms used for short-term toxicity testing. For the bacteria Vibrio fischeri (Microtox test) and Pseudomonas putida, the protozoan Tetrahymena pyriformis (Tetratox test), the green alga Scendesmus quadricauda and the brine shrimp Artemia salina, the main factors resulting in increased non-specific toxicity are size (dominantly) and lone-pair electron interactions, with hydrogen-bond basicity the most important solute property reducing toxicity. Species differences in relative non-specific toxicity are largely related to differences in cohesion and hydrogen-bond acidity of the biomembranes. The models for non-specific toxicity are proposed as an alternative to the octanol-water distribution constant for the determination of baseline toxicity. Failure of the octanol-water distribution constant to model non-specific toxicity is quantitatively explained by its inability to adequately characterize the sorption properties of the biomembranes for compounds with varied properties. 相似文献
914.
[formula: see text] The photoaddition of the thiol 2,3,4,6-tetra-O-acetyl-beta-D-1-thioglucopyranose to the allyl ether functions of per-2-allyl-, per-6-allyl-, and per-2,6-diallyl-beta-cyclodextrin derivatives provides a remarkably simple and efficient way for attaching glucopyranose units onto (1) the secondary face, as well as (2) the primary face, of beta-cyclodextrin--not to mention (3) both the primary and secondary faces, simultaneously--in yields of up to 70%. 相似文献
915.
R. Vîlcu F. Irinei J. Ionescu-Bujor M. Olteanu I. Demetrescu 《Journal of Thermal Analysis and Calorimetry》1985,30(2):495-502
The thermal behaviour of acrylamide-maleic anhydride copolymers was studied by thermogravimetric (TG and DTG) analysis. The obtained data permitted the calculation of activation energies and reaction orders of the decomposition steps by the Coats-Redfern and Freeman-Carroll methods.Thermal analysis shows four distinct peaks in the case of polyacrylamide and AAMA (71) copolymer and only three for AAMA (11) copolymer.In AA:MA (11) copolymers intermolecular imidization occurs only and thermal degradation is influenced more by the anhydride groups which are equal in number with the amide ones.
Zusammenfassung Das thermische Verhalten von Acrylamid-Maleinsäureanhydrid-Kopolymeren wurde durch thermogravimetrische Analyse (TG und DTG) untersucht. Aus den erhaltenen Daten wurden die Aktivierungsenergien und Reaktionsordnungen der Zersetzungsschritte nach den Methoden von Coats-Redfern und Freeman-Carroll berechnet. Durch thermische Analyse können im Falle von Polyacrylamid und AAMA (71 (-Kopolymeren 4 Peaks und bei AA:MA (11) -Kopolymeren nur 3 Peaks unterschieden werden. Bei AAMA (1 1)-Kopolymeren verläuft nur eine intermolekulare Imidisierung und der thermische Abbau wird mehr durch die in gleicher Zahl wie die Amidgruppen vorliegenden Anhydridgruppen beeinflußt.
T () — (). , - -, . : ( 71) , : 11 — . : 11 , , .相似文献
916.
L. A. Chetkina A. N. Sobolev V. K. Bel'skii V. E. Zavodnik I. G. Arzamanova Ya. V. Gurvich O. F. Starikova 《Journal of Structural Chemistry》1991,32(5):766-768
L. Ya. Karpov Scientific-Research Physicochemical Institute. Scientific-Research Institute of Rubber and Latex Goods. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 5, pp. 162–164, September–October, 1991. 相似文献
917.
Yu. F. Migal' 《Journal of Structural Chemistry》1991,32(5):619-624
Conclusions The results from our analysis of quasistationary states in real molecules and solid clusters provide us with grounds for stating that the proposed method can be used successfully to predict the number of resonances of form in molecules and to obtain approximate estimates of their characteristics.In studies in this area at the qualitative level, it is easy to establish the genealogy of the resonances (i.e., from which atomic states they have proceeded) and the effective value of the quantum number characterizing one resonance or another. In qualitative analysis, the mutual positions of the resonances are indicated approximately; with increasing number of atoms, the inaccuracy increases. Moreover, without carrying out the calculation, it is impossible to estimate the resonance energy, as it is impossible to distinguish reliably between resonances from collective free states of the discrete spectrum and from the rudiments of resonances.Nonetheless, it is possible to use the proposed method to judge trends in the change of resonances from one compound to another. Particularly valuable, in our view, is the possibility that is offered here for the use of very nearly the entire arsenal of the qualitative LCAO-MO theory.In order to obtain semiquantitative estimates of the characteristics of resonances, a model with potential wells is applicable. In simple cases, calculations using this model can be performed on a microcalculator.Rostov Institute of Agricultural Machinery Construction. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 5, pp. 3–8, September–October, 1991. 相似文献
918.
919.
Zusammenfassung Die Zersetzung von Pb(CH3COO)3 · 3 H3O wurde im Bereich von Raumtemperatur bis 450° unter N3 mittels TG, DTA verfolgt und die Produkte wurden analytisch charakterisiert. PbO ist das hauptsächliche feste Endprodukt, neben dem im wesentlichen nur Pb entsteht. Als feste Zwischenprodukte wurden neben Pb(CH3COO)3 die basischen Acetate Pb(CH3COO)2 · PbO und Pb(CH3COO)2 · 2 PbO gefunden und durch Röntgenpulveraufnahmen identifiziert; diese basischen Acetate wurden durch isotherme Zersetzung bei 240 bzw. 305° dargestellt. Unter den durch GC und MS erfaßten und quantitativ bestimmten flüchtigen Zersetzungsprodukten sind CO2 und Aceton Hauptbestandteile. Verschiedene Bildungsweisen der übrigen Produkte, CH3COOH, (CH3CO)2O, Acetylaceton und des Zwischenproduktes Keten werden aufgezeigt.
Dem Fonds der Chemischen Industrie danken wir für finanzielle Unterstützung. 相似文献
The decomposition of Pb(CH3COO)3 · 3 H2O under N2 has been studied by TG and DTA between room temperature and 450° and the products have been characterized analytically. PbO is the main solid product, besides which essentially only Pb is produced. As solid intermediates, aside from Pb(CH3COO)3 the basic acetates Pb(CH3COO)2 · PbO and Pb(CH3COO)2 · 2 PbO have been found and identified via their X-ray powder diagrams; these basic acetates have been prepared by isothermal decomposition at 240 and 305°, respectively. Among the volatile decomposition products analyzed by GC and MS and determined quantitatively, CO2 and acetone are the main products. Different routes for the formation of the other products, CH3COOH, (CH3CO)2O, acetylacetone and the intermediate ketene are shown.
Résumé On a suivi, par TG et ATD sous N2, dans l'intervalle de températures allant de l'ambiante jusqu'à 450°, la décomposition de Pb(CH3COO)2 · 3 H2O dont on a caractérisé les produits par des méthodes analytiques. PbO est le principal produit final solide, en dehors duquel il ne se forme essentiellement que du Pb. Comme produits intermédiaires solides, on a trouvé, à part Pb(CH3COO)2, les acétates basiques Pb(CH3COO)3. PbO et Pb(CH3COO)2 · · 2 PbO qui ont été identifiés par analyse de poudres aux rayons X. Ces acétates basiques se sont formés, par décomposition isotherme, respectivement à 240 et à 305°. Parmi les produits de décomposition volatils décelés par GC et MS et dosés par des méthodes quantitatives, CO3 et l'acétone sont les composants principaux. On montre les différents modes de formation des autres produits, comme CH3COOH, (CH3CO)3O, l'acétylacétone et le cétène formé transitoirement.
Pb(CH3COO)2. 32O 450°. . PbO , , . , Pb(CH3COO)2, Pb(CH3COO)2. PbO Pb(CH3COO)2. 2PbO, . , , 240 305°. , -, CO2 . , CH3COOH, (CH3CO)2O, .
Dem Fonds der Chemischen Industrie danken wir für finanzielle Unterstützung. 相似文献
920.
A. F. Pavlenko A. V. Kurika V. A. Khomenko Yu. S. Ovodov 《Chemistry of Natural Compounds》1975,10(2):155-158
Conclusions It has been shown by the methylation method that pelvecyan and sargassan are polysaccharides of similar structures with a high degree of branching of the carbohydrate chains. Fucose, xylose, and galactose are located at the nonreducing ends of their molecules, and mannose and galactose form points of branching of the carbohydrate chains of these polysaccharides.The positions of the bonds between the monosaccharide residues in pelvecyan and sargassan have been determined.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 142–145, March–April, 1974. 相似文献