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961.
P. J. M. Wakkers Matthijs J. Janssen W. D. Weringa 《Journal of mass spectrometry : JMS》1972,6(9):963-970
The ratio [M ? D]/{[M-D] + [M ? H]} in the 70 eV mass spectra of six deuterated 3-methylthiophenes has been determined. From these values the mole fractions of the molecular ions that lose hydrogen atoms specifically from the various positions of the molecule were calculated, as well as the mole fraction in which the hydrogen atoms are fully scrambled before hydrogen elimination. It appears that hydrogen atoms are mainly lost from a fully scrambled [C5H6S]+· ion and from the α-position of the original molecular ion. A deuterium isotope effect of 1·60 to 1·72 was calculated for the hydrogen elimination. The reaction was also studied at low electron energies. In order to determine the degree of scrambling in the [C5H5S]+ ions, some decomposition reactions of this ion were investigated. 相似文献
962.
Supercritical fluid extraction (SFE) is combined with supercritical fluid chromatography (SFC) in an analytical mode to develop a system for fractionating and enriching high value ferulate-phytosterol esters (FPE) contained in corn bran oil. Corn bran is initially extracted with neat supercritical carbon dioxide (SC-CO2) at various pressures (13.8, 34.5, and 69 MPa) and temperatures (40, 60, and 80 degrees C) to see if the FPE can be enriched in the extracts. These initial studies show the greatest percentage of FPE could be extracted under two sets of conditions: 69 MPa at 80 degrees C and 34.5 MPa at 40 degrees C. Both sets of parameters yield an extract containing approximately 1.25% FPE. A stock supply of corn bran oil is then produced by scaled-up SFE at 34.5 MPa and 40 degrees C for subsequent chromatographic fractionation. The SFE-obtained corn bran oil is then applied to the head of a minichromatographic column containing an amino-propyl sorbent. SFC is than commenced using neat SC-CO2 at 69 MPa and 80 degrees C to remove the majority of the triglyceride-based oil. Pressure and temperature are then lowered to 34.5 MPa and 40 degrees C, respectively, and ethanol is added as a modifier. The modifier is added in an increasing stepwise gradient program, and fractions are collected at equal volume intervals. The resultant fractions are analyzed by analytical high-performance liquid chromatography with evaporative light-scattering detection and show that FPE could be enriched to a 14.5% (w) level. 相似文献
963.
A rapid, sensitive and specific assay for 9-chloro-2-(2-furyl) [1,2,4]triazolo[1,5-c]quinazolin-5-imine (I) and its oxo metabolite (II) in plasma was developed and validated employing reversed-phase high-performance liquid chromatography with fluorescence detection. Sample preparation was achieved by a simple ethyl acetate extraction from plasma buffered at pH 10 (0.1 M boric acid-0.1 M potassium chloride). Chromatographic analyses were performed isocratically on a C18 column, with a mobile phase consisting of methanol-0.2 M sodium acetate buffer, pH 5.0 (67:33, v/v). Chromatographic run time was less than 8 min. The assay was linear (r greater than 0.9998) over the concentration range 1.50-10,000 ng/ml for both I and II; for individual studies, curves covering a range of two orders of magnitude were generally employed. Limits of detection for I and II were 0.5 and 1.0 ng/ml, respectively. A preliminary investigation of the plasma concentrations of I and II in the rat following a single 30 mg/kg oral dose demonstrated the applicability of the method for pharmacokinetic studies. 相似文献
964.
P. W. Naik P. S. Dhami S. K. Misra U. Jambunathan J. N. Mathur 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(2):327-332
Silica-gel has been used as an inert support for the extraction chromatographic separation of actinides and lanthanides from HNO3 and synthetic high level waste (HLW) solutions. Silica-gel was impregnated with tri-butyl phosphate (TBP), to yield STBP; 2-ethylhexyl phosphonic acid, mono 2-ethylhexyl ester (KSM-17, equivalent to PC-88A), SKSM; octyl(phenyl)-N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO), SCMPO; and trialkylphosphine oxide (Cyanex-923), SCYN and sorption of Pu(IV), Am(III) and Eu(III) from HNO3 solutions was studied batchwise. Several parameters, like time of equilibration, HNO3 and Pu(IV) concentrations were varied. The uptake of Pu(IV) from 3.0M HNO3 followed the order SCMPO>SCYN>SKSM>STBP. With increasing HNO3 concentration, D
Pu increased up to 3.0M of HNO3 for STBP, SKSM and SCMPO and then decreased. In the case of Am and Eu with SCMPO, the D values initially increased between 0.5 to 1.0M of HNO3, remained constant up to 5.0M and then slightly decreased at 7.5M. Also, the effects of NaNO3, Nd(III) and U(VI) concentrations on the uptake of Am(III) from HNO3 solutions were evaluated. With increasing NaNO3 concentration up to 3.0M, D
Am remained almost constant while it was observed that it decreases drastically by adding Nd(III) or U(VI). The uptake of Pu and Am from synthetic pressurized heavy water reactor high level waste (PHWR-HLW) in presence of high concentrations of uranium and after depleting the uranium content, and finally extraction chromatographic column separation of Pu and Am from U-depleted synthetic PHWR-HLW have been carried out. Using SCMPO, high sorption of Pu, Am and U was obtained from the U-depleted HLW solution. These metal ions were subsequently eluted using various reagents. The sorption results of the metal ions on silica-gel impregnated with several phosphorus based extractants have been compared. The uptake of Am, Pu and rare earths by SCMPO has been compared with those where CMPO was sorbed on Chromosorb-102, Amberchrom CG-71 and styrene divinylbenzene copolymer immobilized in porous silica particles. 相似文献
965.
The atomic correlation terms necessary to lead to anaccurate 4s23d8-4st 3d9 separation for the Ni atom have been incorporated into all-electron MC SCF/Cl calculations for the X2 Δ state of NiH. The calculated potential curve properties are significantly improved compared to calculations which dissociate to Hartree-Fock atoms. 相似文献
966.
L. R. P. Butler K. Krger C. D. West 《Spectrochimica Acta Part B: Atomic Spectroscopy》1975,30(12):489-499
A Grimm-type glow discharge lamp was found to have emission lines which are narrow enough to allow the advantageous use of resonance detection. Design of a cathodic sputtering cell which has an exchangeable cathode is described. The fluorescence signal from this lamp was detected electronically by either a synchronous (lock-in) detection system or a dual-gated integration (boxcar) system. It was found that the dual-gated system improved detection limits by a factor of 50 over the synchronous detection system. Calibration curves for copper in aluminium and silver in gold were found to be linear from the detection limit (about 1 ppm for both elements) up to approximately 20% in the case of copper in aluminium, and 5% silver in gold. Reproducibility of signal measurements was 1%. 相似文献
967.
R. Wäppling L. Häggström T. Ericsson S. Devanarayanan E. Karlsson B. Carlsson S. Rundqvist 《Journal of solid state chemistry》1975,13(3):258-271
The para- to ferromagnetic transition in Fe2P has been studied using Mössbauer spectroscopy. The magnetic hyperfine fields drop abruptly from about half of their saturation values to zero at 214.5 K indicating a first order transition. The isomer shifts show a discontinuous change at the transition point. For some samples the transition takes place over a wide temperature range, probably due to impurities and other imperfections in the samples. From the magnetic hyperfine fields at 15 K the magnetic moments can be deduced to be 1.14 μB and 1.78 μB for Fe(1) and Fe(2), respectively. An assignment of the components in the Mössbauer spectra to the two crystallographically nonequivalent iron positions has been made from the temperature variation of the spectra.The ordering of metal vacancies has been investigated by a Mössbauer study of a nonstoichiometric Fe2P sample and by an X-ray diffraction study of a nonstoichiometric Mn2P crystal. 相似文献
968.
The molecular structures of the title compounds have been determined by gas phase electron diffraction methods. The SiMn and GeMn bond lengths are 240.7 ? 0.5 and 248.7 ? 0.2 pm respectively and the CMnC angles in the silyl and germyl cases are 94.5 ± 2° and 97 ± 2° respectively. Comparisons are made with the reported structure of CH3Mn(CO)5 and HeI photoelectron spectra of these compounds in an attempt to determine the extent of d → d π-bonding in the SiMn or GeMn bonds. 相似文献
969.
B.W. Budesinsky 《Analytica chimica acta》1974,71(2):343-347
Antipyrylazo III or diantipyrylazo (3,6-bis(4-antipyrylazo)-4,5-dihydroxy-2, 7-napthalenedisulfonic acid) forms at PH 12.7 a complex Ca2HL with calcium. The logarithmic overall stability constant, 10g β211, is 23.99 ±0.03 (0.1 MNaClO4,25°C).The effective molar absorptivity is 21,500 ±100 l mole-1 cm-1 at 605 nm. The complex can be used for a selective photometric determination of calcium(0.25–3.50μmole) if tri-and tetravalent ions are removed by extraction with cupferron (into chloroform) and transition divalent ions are masked with sodium cyanide. Only strontium (0.5 μmole) and EDTA (0.1 μmole) interfere seriously. 相似文献
970.
Shubhasish MukherjeeKevin W.C Poon Daniel L Flynn Paul R Hanson 《Tetrahedron letters》2003,44(38):7187-7190
Application of a capture-ROMP-release strategy for the chromatography-free purification of Mitsunobu reaction products is described. Norbornenyl-tagged reagents are utilized for standard solution phase Mitsunobu chemistry. Post-reaction phase-switching is accomplished via in situ ring-opening metathesis polymerization (ROMP) followed by precipitation of the polymer with methanol. Release of the product from the polymer affords amines and alkyl hydrazine derivatives with good yields and purities. 相似文献