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991.
Herrero M Temirzoda TN Segura-Carretero A Quirantes R Plaza M Ibañez E 《Journal of chromatography. A》2011,1218(42):7511-7520
In this contribution, the capabilities of pressurized liquid extraction (PLE) using food-grade solvents, such as water and ethanol, to obtain antioxidant extracts rich on polyphenolic compounds from olive leaves are studied. Different extraction conditions were tested, and the PLE obtained extracts were characterized in vitro according to their antioxidant capacity (using the DPPH radical scavenging and the TEAC assays) and total phenols amounts. The most active extracts were obtained with hot pressurized water at 200 °C (EC(50) 18.6 μg/mL) and liquid ethanol at 150 °C (EC(50) 27.4 μg/mL), attaining at these conditions high extraction yields, around 40 and 30%, respectively. The particular phenolic composition of the obtained extracts was characterized by LC-ESI-MS. Using this method, 25 different phenolic compounds could be tentatively identified, including phenolic acids, secoiridoids, hydroxycinnamic acid derivatives, flavonols and flavones. Among them, hydroxytyrosol, oleuropein and luteolin-glucoside were the main phenolic antioxidants and were quantified on the extracts together with other minor constituents, by means of a UPLC-MS/MS method. Results showed that using water as extracting agent, the amount of phenolic compounds increased with the extraction temperature, being hydroxytyrosol the main phenolic component on the water PLE olive leaves extracts, reaching up to 8.542 mg/g dried extract. On the other hand, oleuropein was the main component on the extracts obtained with ethanol (6.156-2.819 mg/g extract). Results described in this work demonstrate the good possibilities of using PLE as a useful technique for the valorization of by-products from the olive oil industry, such as olive leaves. 相似文献
992.
Aragón A Cortés JM Toledano RM Villén J Vázquez A 《Journal of chromatography. A》2011,1218(30):4960-4965
An automated method for the direct analysis of wax esters in edible oils is presented. The proposed method uses the TOTAD (through oven transfer adsorption desorption) interface for the on-line coupling of normal phase liquid chromatography and gas chromatography. In this fully automated system, the oil with C32 wax ester as internal standard and diluted with heptane is injected directly with no sample pre-treatment step other than filtration. The proposed method allows analysis of different wax esters, and is simpler and faster than the European Union Official Method, which is tedious and time-consuming. The obtained results closely match the certified values obtained from the median of the analytical results of the inter-labs certification study. Relative standard deviations of the concentrations are less than 5%. The method is appropriate for routine analysis as it is totally automated. 相似文献
993.
Cebolla VL Jarne C Domingo P Domínguez A Delgado-Camón A Garriga R Galbán J Membrado L Gálvez EM Cossío FP 《Journal of chromatography. A》2011,1218(19):2668-2675
Changes in emission of berberine cation, induced by non-covalent interactions with lipids on silica gel plates, can be used for detecting and quantifying lipids using fluorescence scanning densitometry in HPTLC analysis. This procedure, referred to as fluorescence detection by intensity changes (FDIC) has been used here in combination with automated multiple development (HPTLC/AMD), a gradient-based separation HPTLC technique, for separating, detecting and quantifying lipids from different families. Three different HPTLC/AMD gradient schemes have been developed for separating: neutral lipid families and steryl glycosides; different sphingolipids; and sphingosine-sphinganine mixtures. Fluorescent molar responses of studied lipids, and differences in response among different lipid families have been rationalized in the light of a previously proposed model of FDIC response, which is based on ion-induced dipole interactions between the fluorophore and the analyte. Likewise, computational calculations using molecular mechanics have also been a complementary useful tool to explain high FDIC responses of cholesteryl and steryl-derivatives, and moderate responses of sphingolipids. An explanation for the high FDIC response of cholesterol, whose limit of detection (LOD) is 5 ng, has been proposed. Advantages and limitations of FDIC application have also been discussed. 相似文献
994.
Shi X Bertóti I Pukánszky B Rosa R Lazzeri A 《Journal of colloid and interface science》2011,362(1):67-73
In a preceding paper it was found that, during coating with solutions of a stearin salt in water, whatever the concentration used, a considerable part of the PCC surface remains free, indicating the development of an incomplete monolayer. This was explained by assuming a micelle adsorption mechanism as the dominating process in water, resulting in the formation of a multilayer structure composed of an inner incomplete chemisorbed monolayer and one or more physically adsorbed layers. This model predicted a physisorbed layer in which polar groups are oriented outwards of the particles, resulting in a hydrophilic surface, and contrary to experimental evidence. In this paper we propose that during the drying stage the physisorbed calcium stearate layers undergo a complex rearrangement leading to a hydrophobic coating with the aliphatic tails oriented outwards of the particles. The results of XRD measurements proved that the physisorbed stearate layer is crystalline, while DSC model experiments indicated that the layer goes through phase transitions during heat treatment. The proposed model matched with IGC measurements, showing a clear dependence of the specific component of surface energy on the amount of absorbed stearin. The agreement with values obtained for solvent and dry-coated particles support the proposed rearrangement of alkanoate molecules in the coating. 相似文献
995.
José María Rivera Susana Rincón Norberto Farfán Rosa Santillan 《Journal of organometallic chemistry》2011,696(11-12):2420-2428
Nine new boronates, six of them chiral, with five-six-membered ring heterobicycles were prepared by reaction of the Schiff bases and phenyl boronic acid. The boronates were fully characterized by spectroscopic techniques, NMR 1H, 13C, 11B, Infrared spectroscopy, mass spectrometry and elemental analysis. The reaction showed high diasteroselectivity, only in the case of compound 4c, containing a methyl substituent in the aliphatic moiety, the induction is low giving a 2:1 mixture of two diatereoisomers. The results showed that the preferred stereochemistry in the heterocycles is that where all substituents in the five membered ring and the phenyl group attached to boron atom are on the same side. 相似文献
996.
A new flow injection (FIA) procedure for the preconcentration of cadmium in urine using multiwalled carbon nanotubes (MWCNT) as sorbent and posterior electrothermal atomization atomic absorption spectrometry (ETA-AAS) Cd determination has been developed. Cadmium was retained in a column filled with previously oxidized MWCNTs and it was quantitatively eluted with a nitric acid solution. The parameters influencing the adsorption-elution process such as pH of the sample solution, amount of sorbent and flow rates of sample as well as eluent solutions have been studied. Cd concentration in the eluent was measured by ETA-AAS under the optimized conditions obtained. The results indicated the elimination of urine matrix effect as a consequence of the preconcentration process performed. Total recovery of cadmium from urine at pH 7.2 using a column with 45 mg of MWCNTs as sorbent and employing a HNO3 0.5 mol L−1 solution for elution was attained. The detection limit obtained was 0.010 μg L−1 and the preconcentration factor achieved was 3.4. The method showed adequate precision (RSD: 3.4-9.8%) and accuracy (mean recovery: 97.4-100%). The developed method was applied for the determination of cadmium in real urine samples from healthy people (in the range of 0.14-2.94 μg L−1) with satisfactory results. 相似文献
997.
A series of novel (oligo)thienyl-imidazo-benzocrown ethers were synthesised through a simple method and evaluated as fluorimetric chemosensors for transition metal cations. Interaction with Ni2+, Pd2+, and Hg2+ in ACN/DMSO solution (99:1) was studied by absorption and emission spectroscopy. Chemoselectivity studies in the presence of Na+ were also carried out and a fluorescence enhancement upon chelation (CHEF) effect was observed following Hg2+ complexation. Considering that most systems using fluorescence spectroscopy for detecting Hg2+ are based on the complexation enhancement of the fluorescence quenching (CHEQ) effect, the present work represents one of the few examples for sensing of Hg2+ based on a CHEF effect. 相似文献
998.
Rosa M.F. BatistaElisabete Oliveira Susana P.G. CostaCarlos Lodeiro M. Manuela M. Raposo 《Tetrahedron》2011,67(37):7106-7113
Novel fluorescent ionophores bearing imidazo-arylthienyl or imidazo-bithienyl π-conjugated bridges functionalized with one or two fused benzo-15-crown-5 ethers as receptor units are reported. The sensing ability of the compounds in the presence of metallic cations (Li+, Na+, K+, Ca2+, Zn2+, Cu2+, Ni2+, Pd2+, and Hg2+) and fluoride ion was studied in MeCN/DMSO solutions by absorption and emission spectroscopy. The experimental results indicate that all compounds could act as selective fluorimetric sensors for Cu2+ and Pd2+ and also for the fluoride ion, in the case of the bis-substituted crown ether derivatives. 相似文献
999.
Javier MoragaCristina Pinedo Rosa Durán-PatrónIsidro G. Collado Rosario Hernández-Galán 《Tetrahedron》2011,67(2):417-420
The absolute configuration of botrylactone, a unique compound with an interesting polyketide lactone skeleton with two oxirane bridges previously isolated from Botrytis cinerea and described as a powerful antibiotic, has been reviewed on the basis of sign of the optical rotation, NOE experiments and NMR method. The isolation of 7-deoxybotrylactone and 5-hydroxy-7-(4-hydroxydec-2(3)-enoyl) botrylactone enables us to characterize an intriguing new family of compounds with this interesting polyketide skeleton. A common biosynthetic origin with botcinin derivatives is proposed. 相似文献
1000.