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991.
The deoxygenation of methyloxirane to propene and its isomerization to oxo compounds on a Ni/SiO2 catalyst were studied in a pulse microreactor, in the presence of H2 as carrier gas, at 473 K. It was found that the deoxigenation leads to the creation of new types of active centers (Lewis acid site-basic site), which cause a change in the direction of ring opening. The differences in regioselectivity observed between Ni and Cu, and Pt and Pd, can be explained by the different affinities of the metals for oxygen. This finding can be generalized to other oxygen-containing compounds.
Part IV: J. Catal. (to be published) 相似文献
=qa Ni/SiO2 473 . , - - , . Ni Cu, Pt Pd . .
Part IV: J. Catal. (to be published) 相似文献
992.
E. P. Talsi Yu. S. Zimin V. M. Nekipelov 《Reaction Kinetics and Catalysis Letters》1985,27(2):361-364
993.
A. S. Kharitonov G. K. Boreskov G. I. Panov Yu. D. Pankratiev 《Reaction Kinetics and Catalysis Letters》1983,22(3-4):309-314
Adsorption heats q and activation energies of the nitrogen exchange on several metal nitrides have been compared. For the systems capable of changing readily their composition upon varying conditions, the isotope exchange is suggested to be the most reliable method of the determination of q.
. , , , .相似文献
994.
A study has been made of the comparative suitability of the ceriumIII, lanthanum and praseodymium chelates of alizarin complexan as reagents for the spectrophotometric determination of microgram amounts of fluoride. The ceriumIII reagent is most sensitive at pH < 4.5 and the lanthanum reagent at pH 5.0. An enhancement of sensitivity may be obtained for both reagents at pH 4.3 by addition of acetone to 25 % v/v, but the most sensitive means of determination is to use the lanthanum reagent in aqueous solution at pH 5.2 with measurement at 281 mμ. This procedure is 200% more sensitive than the standard method at 620 mμ. 相似文献
995.
Summary 1. The structure of the main groups of phospholipids isolated from the seed kernels of the thin-fibered cotton plant of variety S-6029 has been studied.2. The fatty-acid compositions and the position distributions of the fatty acids have been determined, and from the results the possible molecular compositions of the phosphatidylcholines, phosphatidylethanolamines, and phosphatidylinositols have been calculated.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedimenii, No. 1, pp. 22–26, January–February, 1976. 相似文献
996.
Günther Kraft Dieter Lindenberger Heinz Beck 《Fresenius' Journal of Analytical Chemistry》1976,282(2):119-121
Zusammenfassung Die Intensität des flammenabsorptionsspektrometrischen Cr-Signals hängt in einer sehr komplexen Weise von der Wertigkeit des Chroms und der Flammentemperatur ab. Ferner ist ein ausgeprägter Kalium-Einfluß vorhanden. Alle diese Schwierigkeiten können am besten dadurch eliminiert werden, daß in der Lachgasflamme gearbeitet und die Analysenlösung mit einer höheren K-Konzentration gepuffert wird.
Effect of valency on the determination of chromium by flame absorption spectrometry
The intensity of the chromium signal in AAS depends in a very complex manner strongly on the valency of the Cr and the flame temperature. It is furthermore influenced by potassium, if present. The best way to overcome all these interferences is to use the nitrous oxide flame and to buffer the solution with a higher concentration of potassium.相似文献
997.
Janko Dimitriev Michail Arnaudov Vesselin Dimitrov 《Monatshefte für Chemie / Chemical Monthly》1976,29(21):1335-1343
Studies of glasses and their crystalline products in the TeO2–V2O5 system were made in the 1400–400 cm–1 range. A continuous shift of the V=O-band from 1020 cm–1 to 940 cm–1 was found in the glasses with decreasing concentration of V2O5, as well as a sharp decrease in the intensity at 830 cm–1. On the basis of the results obtained, it is concluded that with increasing TeO2 content, the structure of the glasses is changed, caused by the breaking of the V–O–V bonds and the formation of Te–O–Te bridges.The IR-spectrum of the 2TeO2·V2O5 compound in both crystalline and vitreous states was studied for the first time. The behaviour of the absorption bands is related to the structure of the glasses studied. 相似文献
998.
A. S. Lisitsyn V. L. Kuznetsov Yu. I. Yermakov 《Reaction Kinetics and Catalysis Letters》1980,14(4):445-450
Catalysts prepared by pyrolysis of Co2(CO)8 on oxide supports have been studied in the hydrogenation of CO. It is shown that MgO and -Al2O3-based catalysts are less active than those supported on SiO2, TiO2 and ZrO2. The application of -Al2O3 as a support increases the relative yield of light hydrocarbons.
, Co2(CO)8 , CO. , MgO -Al2O3 SiO2, TiO2 ZrO2. -Al2O3 .相似文献
999.
K. Yu. Adzhamov A. K. Khanmamedova T. G. Alkhazov 《Reaction Kinetics and Catalysis Letters》1980,13(4):361-365
The reduction of bismuth molybdate Bi2(MoO4)3 by hydrogen increases its activity in isomerization of butene-1 to butenes-2 due to the activation effect of oxygen vacancies.
Bi2(MoO4)3 -І -2, .相似文献
1000.
T. Mathew D. Ramaiah
C. P. Joshua
D. Weir
M. V. George
《Journal of photochemistry and photobiology. A, Chemistry》1993,70(3):245-251The transient absorption spectra of the 2,2′-dinitrodiphenylmethanes 1a–1c in solution were examined in the picosecond and nanosecond time ranges. The absorption bands, observed at 420–450 nm on 355 nm (18 ps) excitation of these compounds, were attributed to the nitronic acids 2a–2c, formed through the singlet-state- mediated intramolecular hydrogen abstraction and the triplet states of 1a–1c. Biradical intermediates, formed through the intramolecular abstraction of the benzylic hydrogen by the triplet excited state, were detected for 1a and 1b. Transient species produced following 355 nm (approximately 6 ns) pulse excitation of 1a–1c result in the formation of the corresponding nitronic acids 2a–2c, with absorption maxima around 415–430 nm. These nitronic acids are the precursors of the various products formed in the steady state irradiation of 1a–1c 相似文献