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931.
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
932.
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
933.
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
934.
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
935.
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
936.
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
937.
J. Langelaar M.W. Leeuw J.D.W.Van Voorst R.P.H. Rettschnick 《Chemical physics letters》1979,62(1):14-18
S2 and S1 fluorescence of chrysene and 3,4 benzophenanthrene has been observed in the vapour phase under collision free conditions. It is shown that the intermediate strong couplinng model can be applied to these molecules. The efficiency of the transfer of the excess energy to collision partners is given for different gases. 相似文献
938.
A solid-phase microextraction (SPME) device was used as a time-weighted average sampler for n-valeraldehyde. The SPME device was first modified to improve the wearer's acceptance as a passive sampler. Then a poly(dimethylsiloxane)-divinylbenzene fiber was used and O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was loaded onto the fiber. Vapors of known concentrations around the threshold limit values time-weighted average of n-valeraldehyde and specific relative humidities (RHs) were generated by syringe pumps in a dynamic generation system. n-Valeraldehyde vapors in gas bags were also generated. An exposure chamber was designed to allow measurement of face velocities, temperatures, exposing vapor concentrations, and RHs. Gas chromatography with flame ionization detection was used for sample analysis. The appropriate adsorption time for SPME coating PFBHA was determined to be 2 min and the desorption time for oxime formed after sampling was optimized to be 2 min. The experimental sampling constant was found to be (3.86+/-0.13) x 10(-2) cm3/min and face velocity was not expect to have effect on the sampler. 相似文献
939.
The mass spectra of the pyrrolidides of some long-chain carboxylic acids with alicyclic residues attached to their ω-end are discussed and compared with the spectra of the corresponding esters. Fragmentation triggered by the pyrrolidide group generates a series of peaks, which clearly exhibits the size and the structure of the carbon chain. 相似文献
940.
Vibrational energy transfer has been studied in S18O2, following pumping of the symmetric stretch (ν1) by a Q-switched CO2 laser. Fluorescence from the asymmetric stretch (ν3) is monitored as a function of time following the laser pulse. This fluorescence rises with a rate constant of 74 ± 10 ms?1 torr?1, and then decays with a rate constant of 3.6 ± 0.1 ms?1 torr?1 for the S18O2 itself. The effect of rare gases on the rise and fall rates was also studied. The results agree well with those on S16O2 and are consistent with a double V-V picture in which the excitation is distributed rapidly between the stretches, but is shared with the bend much more slowly. This produces molecules in which the stretches are much “hotter” than the bend, giving rise to possibilities of laser action on the stretch-to-bend transitions and mode-selective vibrational enhancement of chemical reactions. Also, new results have been derived on the kinetics of V-V processes in mixtures. V-V transfer in various isotopic mixtures of SO2 has been studied and the kinetic analysis indicates that S18O2 and S16O2 exhibit the same V-V rates. 相似文献