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131.
Electrically charged (up to 107 e) macroscopic superconducting particles with sizes in the micrometer range confined in a static magnetic trap in liquid nitrogen and in nitrogen vapor at temperatures of 77–91 K are observed experimentally. The macroparticles with sizes up to 60 μm levitate in a nonuniform static magnetic field B ~ 2500 G. The formation of strongly correlated structures comprising as many as ~103 particles is reported. The average particle distance in these structures amounts to 475 μm. The coupling parameter and the Lindemann parameter of these structures are estimated to be ~107 and ~0.03, respectively, which is characteristic of strongly correlated crystalline or glasslike structures. 相似文献
132.
The oscillatory motion of electrons in a periodic potential under a constant applied electric field, known as Bloch oscillations (BO), is one of the most striking and intriguing quantum effects and was predicted more than eighty years ago. Oscillating electrons emit electromagnetic radiation and here we consider this BO effect for emission in the THz region. To date, it has been assumed that the Bloch oscillation of an electron is anharmonic oscillation, therefore with radiation emitted at the single Bloch frequency. We analyze scenarios when Bloch oscillations can be accompanied by the emission of radiation not only at the Bloch frequency but also with double and triple Bloch frequencies. The first scenario means that electrons could jump over neighboring Stark states. The second scenario of anharmonic emission is coupled to an opening of the minigap in the miniband. 相似文献
133.
T. A. Danilova A. N. Korepanov S. N. Petrov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):71-72
Abstract It is established that isometric butenyl phenyl sulfides on chromic catalysts yield mainly direct cyclization products unlike their reactions on heterogenous acidic catalysts previously investigated in our laboratory. In the presence of such catalysts the formation of cyclic comcounds proceeds in different ways depending on the position of the side-chain double bond. In case chromic catalysts are used the mentioned factor affects only the easiness of cyclization, but not the nature of the process as such. 相似文献
134.
A. A. Kaunova V. I. Petrov T. G. Tsyupko Z. A. Temerdashev V. V. Perekotii A. A. Luk’yanov 《Journal of Analytical Chemistry》2013,68(9):831-836
We have estimated the possibility of identifying the provenance of some natural wines produced in the Krasnodar region. The macro- and microelement composition of wines and soils from the place of grape origin has been used as the classification criterion. The main elements indicating the wine provenance, Al, Co, Cu, Mn, Ti, Zn, Ba, and Rb have been determined by inductively coupled plasma atomic emission spectroscopy. We have revealed the possibility of distinguishing wines by their brand and provenance using pair-wise comparison of the classification function parameters for soils and wines produced from grape grown on those soils. 相似文献
135.
A. B. Shishmakov M. S. Molochnikov D. O. Antonov O. V. Koryakova A. S. Seleznev L. A. Petrov 《Russian Journal of Applied Chemistry》2013,86(3):297-303
A Cu(II)-containing binary xerogel TiO2-SiO2 was synthesized by joint hydrolysis of tetrabutoxytitanium, teraethoxysilane and copper(II) chloride dissolved in their mixture. The synthesis was performed in a vapor of 10% aqueous ammonia under static conditions. EPR spectroscopy was used to examine the state of Cu(II) in the xerogel matrix. Data on specific features of the behavior of saccharose within xerogel pores under heating were obtained. The catalytic activity of the xerogel was tested by the kinetic method on model reactions of hydrogen peroxide decomposition and oxidative dehydrogenation of trimethylhydroquinone. 相似文献
136.
The state of tetra(5-tert-butylpyrazino)porphyrazine, octaethyltetrapyrazinoporphyrazine, octaphenyltetrapyrazinoporphyrazine in DMSO medium was studied. It was found that the complexes formed with the proton transfer exhibit a relatively high stability. In strong basic media these complexes are kinetically unstable. The influence of the nature of cyclic and acyclic nitrogen-containing bases, as well as the influence of NH-acidity of the porphyrazine macrocycle on the rate and activation parameters of decomposition of the proton-transfer complexes of tetra(5-tert-butylpyrazino)porphyrazine, octaethyltetrapyrazinoporphyrazine, and octaphenyltetrapyrazinoporphyrazine was established. 相似文献
137.
Nina I. Giricheva Georgiy V. Girichev Marwan Dakkouri Sergey N. Ivanov Vjacheslav M. Petrov Valentina N. Petrova 《Structural chemistry》2013,24(3):819-826
α-Naphthalenesulfonyl chloride, α-NaphSC, was studied by gas-phase electron diffraction (GED) and quantum chemical calculations (HF/6-311 + G**, HF/aug-cc-pVDZ, B3LYP/cc-pVDZ, B3LYP/cc-pVTZ, B3LYP/aug-cc-pVDZ, B3LYP/aug-cc-pVTZ, MP2/cc-pVDZ, and MP2/cc-pVTZ). The calculations predict the existence of two conformers with C 1 (I) and C s (II) symmetries. The most stable conformer I has an enantiomer. The experimental data of α-NaphSC obtained at 370(5) K could be best fitted by a C 1 symmetry model indicating that only this form exists in the gas-phase. In this model the Cα–S–Cl plane deviates from the perpendicular orientation relative to the plane of the naphthalene skeleton. Under the applied experimental conditions, the mole fraction of a second less stable conformer II of α-NaphSC predicted by calculations is no more than 1 %. The following geometrical parameters of conformer I were obtained from the experiment (Å and °; uncertainties are in parentheses): r h1(C–H) = 1.082(6), r h1(C–C)cp = 1.407(3), r h1(C–S) = 1.764(5), r h1(S–O)av = 1.425(3), r h1(S–Cl) = 2.051(5), ∠C–Cα–C = 122.5(1), ∠Cα–S–Cl = 101.5(10); C9–C1–S–Cl = 71.4(21). The calculated barriers to internal rotation of the sulfonyl chloride group exceed considerably the thermal energy values corresponding to the temperatures of the GED experiments. Natural bond orbitals analysis of the electron density distribution was carried out to explain the peculiarities of the molecular structure of the studied compound and the deviation from the structures of β-NaphSHal molecules and their benzene analogs. 相似文献
138.
O. I. Kudinova V. G. Krasheninnikov A. A. Samoilenko T. A. Ladygina L. A. Novokshonova E. S. Petrov L. F. Rybakova 《Kinetics and Catalysis》2013,54(5):566-571
The polymerization of 1-butene over the TiCl4/MgCl2 (TMC) catalyst with the use of substituted phosphine oxides R n P(O)(CH2OR′)3 ? n (R = alkyl, R′ = methyl or acyl, n = 0–2)—new external electron donors-has been investigated. The electron-donating (coordinating) centers in these compounds are the phosphoryl group (P=O) and the oxygen atoms of the substituents at the phosphorus atom. The dependence of the 1-butene polymerization activity of TMC on the nature of the substituents in the phosphine oxides has been studied. The microstructure, degree of crystallinity, molecular weight, and strain-strength characteristics of the synthesized polybutene-1 and the effect of hydrogen on these properties are reported. The most efficient external donor is Me2P(O)CH2OAc. 相似文献
139.
Meili Duan Takeyasu Tasaka Hiroaki Okamoto Vladimir F. Petrov Shunsuke Takenaka 《Liquid crystals》2013,40(9):1195-1205
This paper describes the effect of substituent and ester linkage on smectic properties for some derivatives of 4-R -phenyl 4-(4-octyloxybenzoyloxy)benzoates (1), 4-octyloxyphenyl 4-(4-R-benzyloxy)benzoates (2), 4-(4-octyloxybenzoyloxy)phenyl 4- R -benzoates (3), and 4-R-phenyl 4-octyloxyphenyl terephthalates (4) where R = OCH3, CH3, OC8H17, C8H17, halogens, CF3, OCF3, CN, NO2, etc. The thermal properties are discussed in terms of the electrostatic nature of the substituents and the relative orientation of the ester groups with respect to both terminal substituents. The substituent effect on the layer structure of the smectic A phase is also examined by means of a small angle X-ray analysis. 相似文献
140.
Rossitsa B. Georgieva Panayot K. Petrov Plamen S. Dimitrov 《International journal of environmental analytical chemistry》2013,93(9):673-685
The aim of this study was to develop a method for the characterization of internal exposure to arsenic, which is thought to play a role in the development of a kidney disease, known as Balkan Endemic Nephropathy, typical for a district in Bulgaria, and to investigate whether the As body burden differs in the offspring versus control individuals. For this case study, an analytical procedure for the determination of toxicologically relevant arsenic (the sum of arsenite, arsenate, monomethylarsonate, and dimethylarsinate) in urine by batch-type hydride generation atomic absorption spectrometry was developed. Optimization experiments for levelling off the sensitivity of inorganic arsenic and its mono- and dimethylated species in dilute HCl–L-cysteine medium were performed. The limit of detection for hydride forming arsenic fraction was 0.5?ng As, i.e. 0.25?µg?L?1 in 10?mL of 1?+?4 v/v diluted urine. The relative standard deviation was typically 1.5–1.8% for aqueous solution and 2–6% for urine samples at 1.0?µg?L?1 As. The sample throughput rate was 15?h?1. No statistical correlation and cross-correlation between individuals case-control and sex at 95% confidence were found: controls (n?=?99), mean 3.5?±?2.1 (SD), range 0.9–10.4, median 3.0?µg?L?1 As and cases (n?=?102), mean 3.6?±?2.2 (SD), range 0.5–11.0, median 3.2?µg?L?1 As. On the basis of this study, arsenic can be excluded as a factor involved in BEN development. 相似文献