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111.
Magdalena Kurdziel Elżbieta Szczepaniec-Cięciak Barbara Dąbrowska Wojciech Nitek Katarzyna Paliś Edyta Ślusarska 《Journal of solution chemistry》2003,32(7):601-615
The solubilities of solid 2,3-dimethylbutane and cyclopentene in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in solutes. The experimental value of the mole fraction solubility of solid 2,3-dimethyl-butane in liquid argon at 87.3 K is (8.26 ± 1.60) × 10–6 and (2.77 ± 0.94) × 10–8 in liquid nitrogen at 77.4 K. The experimental value of the mole fraction solubility of solid cyclopentene in liquid argon at 87.3 K is (5.11 ± 0.44) × 10–6 and (4.60 ± 0.76) × 10–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbons in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l
12 were also calculated. At 90.0 K liquid argon is a better solvent for investigated solid hydrocarbons than is liquid nitrogen. 相似文献
112.
The reversed-phase high-performance liquid Chromatographic (RP-HPLC) behaviour of the binary chelates of V(V) and V(IV) with 4-(2-pyridylazo) resorcinol (PAR) and ternary chelates of vanadium with PAR and auxiliary ligands: hydrogen peroxide, hydroxylamine, tartrate and citrate were studied using a C18 column. The complex double-peak chromatograms of V(IV)/V(V)-PAR systems were studied and the origin of each peak was proved. Vanadium in ternary systems with PAR and hydrogen peroxide was found exclusively in V(V)-H2O2-PAR complex (single peak on the chromatogram) despite its initial oxidation state. The double role of hydroxylamine (complex agent and reductor) in vanadium systems with PAR was confirmed: in the V(V) system three species were identified (V(V)-PAR, V(V)-NH2OH-PAR and V(IV)-PAR), but in the V(IV) system only two: V(IV)-PAR and V(V)-NH2OH-PAR. Citrate and tartrate giving single peak were found as auxiliary ligands in ternary V(V) systems of analytical importance. Due to its masking potential towards iron (III) ions, citrate was chosen as the most suitable third component of a ternary vanadium system with PAR, to form the basis of an RP-HPLC method for direct determination of V in steel. 相似文献
113.
A novel agarofuran sesquiterpene polyol ester, 1beta,2beta,6alpha,15beta-tetracetoxy-8 beta,9alpha-dibenzoyloxy-beta- dihydroagarofuran (celahin D) (1), two known analogues of 1,1beta-acetoxy-8beta,9alpha-dibenzoyloxy-4al pha6alpha-dihydroxy-2beta(alphamethylbutanoyloxy)-beta-++ +dihydroagarofuran (2) and beta-acetoxy-8beta,9alpha-dibenzoyloxy-6alpha-hy droxy-2beta(alpha -methylbutanoyloxy)-beta-dihydroagarofuran (3), and a known cytotoxic sesquiterpene pyridine alkaloid, emarginatine E (4) were isolated from the stems of Celastrus hindsii Benth. Three known triterpenes, loranthol (5), lupenone (6) and friedelinol (7) were also obtained from the titled plant. Structural elucidation of compound 1 was established by 2D NMR spectra. 相似文献
114.
Lapinski L Nowak MJ Kwiatkowski JS Leszczynski J 《Photochemistry and photobiology》2003,77(3):243-252
N2-hydroxyisocytosine and 1-methyl-N2-hydroxyisocytosine were studied using a matrix isolation technique combined with infrared absorption spectroscopy. For N2-hydroxyisocytosine isolated in an Ar matrix (at 10 K), two imino-oxo isomers, one with the hydroxyimino =N-OH group directed toward the N1-H group (the form called further anti) and the second with the =N-OH group directed toward N3-H (syn), were observed in the ratio 1.4:1. The syn isomer is converted totally to the anti form after UV (lambda > 295 nm) irradiation of the matrix. A small amount of the N(3)H-hydroxy-amino tautomer of N2-hydroxyisocytosine was also detected in the matrix. This form did not react photochemically. For 1-methyl-N2-hydroxyisocytosine, only the syn form of the imino-oxo tautomer was observed after deposition of the matrix. UV (lambda > 295 nm) irradiation induced a photoreaction converting this isomer into the anti form. After 15% of the starting material had been converted into the product, a photostationary state was achieved, and no further progress of the reaction was observed. Subsequent UV irradiation (lambda > 335 nm) caused a back reaction, leading to a disappearance of the anti form and to the recovery of the initial syn isomer. All isomers were identified by comparing their experimental IR spectra with the spectra theoretically calculated at the DFT(B3LYP)/6-31G(d,p) level, where DFT is the density functional theory. Good agreement between the observed and predicted patterns of the spectral lines allowed for reliable identification. The experimental IR spectra were interpreted and discussed. The relative energies of the 12 isomers of N2-hydroxyisocytosine were calculated at the MP2/6-31G(d,p) and MP4//MP2/6-31G(d,p) levels. For six isomers of 1-methyl-N2-hydroxyisocytosine, the calculations were carried out at the MP2/6-31G(d,p) level. The anti form of the imino-oxo tautomer of N-hydroxyisocytosine and the syn form of the imino-oxo tautomer of 1-methyl-N2-hydroxyisocytosine were predicted to be the most stable. 相似文献
115.
Wojakowska A. Krzyżak E. Wojakowski A. 《Journal of Thermal Analysis and Calorimetry》2001,65(2):491-495
The phase diagram for the RbBr–CuBr system has been determined. In the system two intermediate compounds are formed: RbCu2Br3, melting congruently at 537 K and Rb3CuBr4, melting incongruently at 544 K. The coordinates of the two eutectic points are: 501 K, 54 mole% CuBr and 522 K, 74 mole%
CuBr.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
116.
Studies on 16-Membered Azothia- and Azoxythiacrown Ethers as Ion Carriers in Ion Selective Membranes
Jolanta Szczygelska-Tao Jan F. Biernat Łukasz Górski Elżbieta Malinowska 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):167-171
16-Membered azothia- and azoxythiacrown ethers have been studied as ion carriers in ion-selective membranes. Their selectivities towards alkali, alkaline earth, transition and heavy metal cations were evaluated. The complex formation constants for these compounds with chosen cations have been determined using segmented sandwich membranes method. 相似文献
117.
Maciej PisklakFranciszek Herold Romana Anulewicz-OstrowskaIwona Wawer 《Journal of Molecular Structure》2002,605(1):85-92
13C cross-polarisation magic angle spinning NMR data have been reported for four derivatives of 4-aryl-octahydro-pyrido[1,2-c]pyrimidine-1,3-dione and the X-ray diffraction data for two (with 2′-Me and 2′-OMe). The crystal structures show the presence of centrosymmetric cyclic dimers with intermolecular C1O?H-N or C3O?H-N hydrogen bonds, the configuration at the chiral centres (C4 and C4a) was determined as RR (SS). The twisting of aromatic ring at C4 with respect to the pyrido[1,2-c]pyrimidine skeleton is about 68-109°. 相似文献
118.
Colloidal noble metal-based nanoparticles are able to catalyze oxidation of chromogenic substrates by H2O2, similarly to peroxidases, even in basic media. However, lack of robust chromogens, which work in high pH impedes their real applications. Herein we demonstrate the applicability of selected catechol derivatives: bromopyrogallol red (BPR) and pyrogallol (PG) as chromogenic substrates for peroxidase-like activity assays, which are capable of working over wide range of pH, covering also basic values. Hyperbranched polyglycidol-stabilized gold nanoparticles (HBPG@AuNPs) were used as model enzyme mimetics. Efficiency of several methods of improving stability of substrates in alkaline media by means of selective suppression of their autoxidation by molecular oxygen was evaluated. In a framework of presented studies the impact of borate anion, applied as complexing agent for PG and BPR, on their stability and reactivity towards oxidation mediated by catalytic AuNPs was investigated. The key role of high concentration of hydrogen peroxide in elimination of non-catalytic oxidation of PG and improvement of optical properties of BPR in alkaline media containing borate was underlined. Described methods of peroxidase-like activity characterization with the use of BPR and PG can become universal tools for characterization of nanozymes, which gain various applications, among others, they are used as catalytic labels in bioassays and biosensors. 相似文献
119.
Dimethyl acetals are converted to the corresponding aldehyde in THF with acetyl chloride/zinc chloride in the presence of dimethyl sulfide 相似文献
120.
A new method of stabilizing low-order, proper orthogonal decomposition based reduced-order models of the Navier?CStokes equations is proposed. Unlike traditional approaches, this method does not rely on empirical turbulence modeling or modification of the Navier?CStokes equations. It provides spatial basis functions different from the usual proper orthogonal decomposition basis function in that, in addition to optimally representing the solution, the new proposed basis functions also provide stable reduced-order models. The proposed approach is illustrated with two test cases: two-dimensional flow inside a square lid-driven cavity and a two-dimensional mixing layer. 相似文献