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951.
A precise x-ray fluorescence method for the determination of sulphur in coat. The sample is mixed with calcium oxide and active carbon and is gradually heated to 900°C. After coding, lithium tetraborate and lead oxide are added and a prepared. The Pb Mα line is used as an internal standard for the KKα line. The results for coal have a relative standard deviation of approximately 1% and exhibit. 相似文献
952.
E. Hartung K. Heide R. Naumann K. H. Jost W. Hilmer 《Journal of Thermal Analysis and Calorimetry》1983,26(2):277-284
In spite of numerous investigations the literature data on the thermal decomposition of borax are contradictory. On the basis of thermal, X-ray, gas analytical and optical investigations this fact can be attributed to the complex decomposition mechanism. After the release of about 8 mole water the reaction product is an X-ray amorphous phase, having the thermal behaviour of glass. From this glass sodium diborate (Na2O.2B2O3) crystallizes between 500–600? with further mass loss. Sodium diborate decomposes from about 700? incongruently yielding NaBO2 vapor and B2O3 glass phase. After evaporation of NaBO2 is completed the rate of evaporation of B2O3 increases considerably. 相似文献
953.
K. Torkar G. W. Herzog W. Schintlmeister Dieter Fischer 《Monatshefte für Chemie / Chemical Monthly》1967,98(2):245-253
It is shown that in the case of thermal decomposition of sodium azide the overall kinetics can be predicted by defined particle size of the decomposed sodium azide crystals. This is always the case if the rate constant is a function of the particle size. Hence this special example can be generalized for similar decomposition reactions. It is necessary that the particles decompose independently which could be proved experimentally with sodium azide. If for this reason we state for true that the pressure/time-function of each particle size add together it is possible to set up a formula for the pressure/time-function of any particle size distribution. With the pressure/time function holding for sodium azide of uniform particle size, the total function for a Gauß distribution can be calculated exactly. Moreover, the trivial case of one single particle size and the case of two different particle sizes are discussed. Furthermore an approximation method for any arbitrary pressure/time-functions and distribution by means of “Schwerpunktdeutung” are discussed which can be carried out graphically as well as numerically. The numerical approximation is illustrated by an example. Pressure/time-functions then loose their characteristic form because of their dependence on the particle size distributions under consideration. In this case, reaction mechanism cannot be derived from pressure/time functions. 相似文献
954.
Isocyanides RNC and the isomeric nitriles, RCN, reacting with alkali or alkaline earth metals in liquid ammonia undergo reductive fission to metal cyanides and carbanions R?. The latter are ammonolized to the corresponding hydrocarbons. 相似文献
955.
M. Kahlenbach W. Görner G. Loos 《Journal of Radioanalytical and Nuclear Chemistry》1975,28(1-2):263-269
An automated off-line Ge(Li)-spectrometer is described. Its special features are a sample changer with rotating disk store and pneumatic tube, a self-controlling source—detector distance and an autonomous control programmed by cable connections or by punched tape via a central control unit. The system is meant to do complex routine work in activity supervision and activation analysis. 相似文献
956.
With the help of a commercial heat-flux calorimeter the enthalpy change was measured as a function of the interlamellar spacing for lamellar precipitated Cu-In samples. This is related to the replacement of the two-phase structure (α + δ) by the homogeneous solid solution (α0. From this, the specific interfacial enthalpy of the α-δ interface was determined to be ΔHδ = 1100 ± 550 mJ m?2. A value of ΔHc = 1320 ± 60 J mol?1 results for the chemical part of the total measured transformation enthalpy. A value of ΔSδ = 0.66 mJ m?2 K?1 was estimated for the specific interfacial entropy and using the Gibbs-Helmholtz equation the specific interfacial free energy was calculated as ΔGδ = 700 ± 400 mJ m?2 at 600 K. 相似文献
957.
Spinspin coupling tensors are calculated using self-consistent perturbation theory and INDO wavefunctions, in order to estimate whether neglect of their anisotropy influences molecular dimensions deduced from the NMR spectra of partially oriented solutes. It is found that anisotropy of cis and trans and many aromatic HF couplings can be neglected but that trans FF couplings are markedly anisotropic. Comparisons are made with the limited experimental results. 相似文献
958.
K. Seiffarth und H. W. Ardelt 《Fresenius' Journal of Analytical Chemistry》1964,204(3):184-189
Zusammenfassung Eine spektralphotometrische Methode zur Bestimmung von Mikrogrammengen Thioharnstoff in Gegenwart von Biuret, Cyanat, Cyanursäure, Dicyandiamid, Harnstoff, Melamin und Rhodanid wird beschrieben. Sie beruht auf der Umsetzung des Thioharnstoffs mit salpetriger Säure zu Rhodanwasserstoffsäure, die mit Brom in Bromcyan übergeführt wird. Letzteres wird mit Pyridin und Barbitursäure zu einem intensiv gefärbten, stabilen Polymethinfarbstoff umgesetzt. Störungen durch andere Cyanamidderivate und -folgeprodukte werden untersucht.
3. Mitteilune über die Analyse der Cyanamidderivate. 2. Mitteilung siehe 14.
Frau S. Mohs möchten wir an dieser Stelle für ihre gewissenhafte Mitarbeit unseren Dank aussprechen. 相似文献
Summary A spectrophotometric method is described for the determination of micro amounts of thiourea in presence of biuret, cyanates, cyanuric acid, dicyanodiamide, urea, melamine and thiocyanates. The method bases on the reaction of thiourea with nitrous acid to thiocyanic acid, which is converted with bromine to cyanogen bromide. The latter forms with pyridine and barbituric acid an intensively coloured, stable polymethine dye. The interferences by other cyanamide derivatives and resultant products have been investigated.
3. Mitteilune über die Analyse der Cyanamidderivate. 2. Mitteilung siehe 14.
Frau S. Mohs möchten wir an dieser Stelle für ihre gewissenhafte Mitarbeit unseren Dank aussprechen. 相似文献
959.
A polyurethane foam (PUF) sponge was mounted in a cassette sampler and evaluated as a sorbent for the collection of hexamethylene diisocyanate (HDI) monomer and HDI-based oligomers. Recovery studies indicated 112 +/- 34% average recovery of HDI monomer and 92 +/- 9% and 97 +/- 25% average recovery of HDI-based oligomers when using impregnated PUF sponges. The PUF sponge was also evaluated during actual spray-painting operations. In a series of side-by-side sampling events, an impinger filled with 1-(2-methoxyphenyl)piperazine (MOP) in toluene was compared directly with a cassette sampler containing a PUF sponge impregnated with MOP or 1-(9-anthracenylmethyl)piperazine (MAP) in dimethyl sulfoxide (DMSO). For the analysis of HDI-based oligomer, there is no significant difference (p < 0.05, n = 7) in the air concentration when sampling with either the PUF sponge cassette or the impinger. The results are significant because they indicate that a PUF sponge, which is more convenient than an impinger, may be used for the collection of HDI-based oligomer generated during spray-painting operations. 相似文献
960.
Pyrrolo[1,2-a[3,1]benzothiazepines were successfully synthesized from alkylthiopyrroles. The latter compounds were prepared from the appropriate N-aryl-2-thiocyanopyrroles. 2,3-Dihydro-3-oxo-4-phenylthieno[3,2-b]pyrrole ( 29 ) was obtained from acid treatment of the 2-pyrrolylthioacetic acid 28 . 相似文献