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991.
Directly suspended droplet liquid–liquid–liquid microextraction (LLLME) has been used to determine residues of diclofenac
(2-[2-(2,6-dichlorophenyl) aminophenyl] ethanoic acid), in environmental water samples. In this technique a free suspended
droplet of an aqueous solvent is delivered to the top-center position of an immiscible organic solvent floating on the top
of an aqueous sample while being agitated by a stirring bar placed on the bottom of the sample cell. Recently, diclofenac
was found as an environmental contaminant in sewage, surface, ground and drinking water samples. In the present work, diclofenac
was extracted from water samples by LLLME and analysed by HPLC with UV detection at 281 nm. Factors such as organic solvent,
extraction and back extraction times, stirring rate and the pH of acceptor and donor phases were optimized. Enrichment factor
and detection limit (LOD, n = 7) were 102 and 0.1 μg L−1, respectively. The linearity ranged from 0.5 to 2,000 μg−1 with a %RSD (n = 5) of 7.2 at S/N = 3. All experiments were carried out at room temperature (22 ± 0.5 °C). 相似文献
992.
A. A. Bobrikova M. P. Koroteev A. I. Stash V. K. Bel’skii E. E. Nifant’ev 《Russian Journal of Organic Chemistry》2008,44(8):1150-1156
A novel procedure has been proposed for the synthesis of chiral α-aminophosphoryl compounds from glycosylamines and PH compounds (diphenylphosphine oxide and ethyl and phenyl phenylphosphonates) under mild conditions. The reaction is accompanied by dehydration of the carbohydrate moiety in unprotected monosaccharides to form furan ring. 相似文献
993.
G. Yu. Lopatkova E. I. Volodina N. D. Pis’menskaya Yu. A. Fedotov D. Cot V. V. Nikonenko 《Russian Journal of Electrochemistry》2006,42(8):847-854
Transport characteristics of commercial heterogeneous anion-exchange membranes MA-40 and MA-41 are studied, together with those of membrane MA-40M fabricated by treating the MA-40 surfaces with a strong polyelectrolyte complex. It is demonstrated that, after modification, the electrical conductivity of MA-40M in an NaOH solution increases. At overlimiting currents, the water dissociation rate on this membrane decreases as compared with the initial membrane. At the same time, no noticeable change in the rate of transport of counter-ions (ions Cl-) through the membrane at a fixed potential drop is discovered at under-and overlimiting currents. The MA-40M membrane behavior is explained by the conversion of secondary and tertiary functional ammonium groups in the near-surface membrane layers approximately 80 μm thick into quaternary groups during the treatment by the polyelectrolyte. 相似文献
994.
G. A. Gainanova E. P. Zhil’tsova L. A. Kudryavtseva S. V. Kharlamov Sh. K. Latypov A. P. Timosheva A. I. Konovalov 《Russian Chemical Bulletin》2006,55(8):1411-1418
Micelle formation in a cetyltrimethylammonium bromide-poly(ethylene glycol)-600 monolaurate-chloroform system in the absence
and presence of hydroxybenzylated polyethylenimines (PEI) was studied by dielcometric titration, NMR self-diffusion, light
scattering, and kinetic methods. A catalytic effect of mixed micelles on the reaction of 4-nitrophenylbis(chloromethyl)phosphinate
with PEI was shown. The catalytic effect depends on the degree of substitution of PEI and composition of a surfactant mixture.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1359–1365, August, 2006. 相似文献
995.
A. A. Bogdanov Yu. V. Kosmotynskaya K. I. Yakovlev N. A. Kas’yanenko 《Journal of Structural Chemistry》2006,47(1):178-185
A comparison has been made of conformational changes in the DNA molecule during its interaction in solution with different binuclear coordination compounds of platinum [Pt(NH3)2Cl-R-Pt(NH3)2Cl]Cl2 in cis and trans conformations, which contain cytosine, pyrazine, and carboxypyrazine as the common ligand (R). The influence of concentration of the components, and in particular, of ionic strength of the solution on the complexation process was studied. The influence of the nature of the common ligand, and of cis and trans conformations of coordination compounds on the character of their interaction with DNA was considered. A comparison was made between the structures of DNA complexes with mono-and binuclear compounds with the same set of ligands in the platinum coordination sphere. 相似文献
996.
Yu. M. Chumakov N. M. Samus’ G. Bocelli K. Yu. Suponitskii V. I. Tsapkov A. P. Gulya 《Russian Journal of Coordination Chemistry》2006,32(1):14-20
3-Phenylpropenal thiosemicarbazone hydrate C6H5-HC=CH-CH=N-NH-C(S)-NH2 · H2O (HL · H2O, I) and two chelates [Ni(L)2] · nCH3OH (II) and [Zn(L)2] (III) are studied by X-ray diffraction. The crystals of I are orthorhombic: a = 6.227(1) Å, b = 7.763(2) Å, c = 25.585(5) Å, β = 90°, space group P212121, Z = 4, R = 0.0426. A nonplanar molecule of I has an E conformation. The crystals of II are triclinic: a = 6.551(2) Å, b = 10.752(3) Å, c = 10.885(3) Å, α = 64.751(5)°, β = 82.753(5)°, γ = 89.857(5)°, space group, Z = 1, R = 0.0661. In a centrosymmetric molecule of II, the central atom coordinates two deprotonated ligands L through the immine nitrogen atom and thioamide sulfur atom at the vertices of a distorted square. The crystals of III are monoclinic: a = 25.342(2) Å, b = 9.150(2) Å, c = 21.340(3) Å, α = 90°, β = 111.84(2)°, γ = 90°, space group C2/c, Z = 8, R = 0.0556. In a molecule of complex III, two deprotonated bidentate ligands L are coordinated by the zinc ion through the immine nitrogen atoms and thioamide sulfur atoms to form a distorted tetrahedron at the central atom. In both II and III, ligand L after coordination by the metal ion changes the E conformation with respect to the N(1)-C(2) bond for the Z conformation. In crystals I-III, molecules are packed to form infinite layers parallel to the planes (001) and (010). 相似文献
997.
L. A. Kartsova A. V. Alekseeva I. K. Khmel’nitskii S. M. Komissarchik G. G. Nyanikova V. G. Berezkin 《Journal of Analytical Chemistry》2009,64(12):1264-1269
Conditions were optimized for separating synthetic food dyes E 102, E 110, E 122, E 124, E 128, E 129, and E 133 by two-dimensional thin-layer chromatography (TLC) on Sorbfil plates using the mobile phase methanol-2-propanol-ethyl acetate-water (1: 1: 2: 2) in both the first (high-performance TLC) and second (electroosmotic TLC) directions. Conditions were selected for separating E 122, E 124, and E 133 by capillary zone electrophoresis; a borate buffer solution with pH 9.2 containing 10 vol % of acetonitrile was used. The time of separation was 16 min. 相似文献
998.
The filter diagonalization method (FDM) is a recently developed computational technique capable of extracting resonance frequencies and amplitudes from very short transient signals. Although it requires stable resonance frequencies and is slower than the fast Fourier transform (FFT), FDM has a resolution and accuracy that is unmatched by the FFT or any other comparable techniques. This unique feature of FDM makes it an ideal tool for tracing space charge induced frequency modulations in Fourier transform ion cyclotron resonance (FT-ICR) cells, which are shown to reach +/-400 ppm even for such simple spectra as Substance P. 相似文献
999.
Meija J Mester Z D'Ulivo A 《Journal of the American Society for Mass Spectrometry》2006,17(7):1028-1036
Three conceptually different mathematical methods are presented for accurate mass spectrometric determination of H2O/HOD/D2O and H2Se/HDSe/D2Se concentrations from mixtures. These are alternating least-squares, weighted two-band target entropy minimization, and a statistical mass balance model. The otherwise nonmeasurable mass spectra of partially deuterated isotopologues (HOD and HDSe) are mathematically constructed. Any recorded isotopologue mixture mass spectra are then deconvoluted by least-squares into their components. This approach is used to study the H2O/D2O exchange reaction, and is externally validated gravimetrically. The H2O/D2O exchange equilibrium constant is also measured from the deconvoluted 70 eV electron impact GC/MS data (K = 3.85 +/- 0.03). 相似文献
1000.
S. I. Lopatin V. L. Stolyarova V. G. Sevast’yanov P. Ya. Nosatenko V. V. Gorskii D. V. Sevast’yanov N. T. Kuznetsov 《Russian Journal of Inorganic Chemistry》2012,57(2):219-225
Silicon evaporation has been investigated by high-temperature mass spectrometry, and the saturation vapor pressure of silicon
over its melt has been determined over the temperature range from 1739 and 2326 K. The saturation vapor pressure data obtained
via silicon evaporation from Knudsen cells made of molybdenum, tungsten, molybdenum disilicide-lined molybdenum, and graphite
silicided by the gas-phase method are compared. Among these materials, silicided graphite is the most inert toward silicon
vapor. The silicon partial pressures measured in the silicided graphite cell are close to the recommended values. 相似文献