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871.
872.
Natalia Campillo Juan Ignacio Cacho Javier Marín Pilar Viñas Manuel Hernández-Córdoba 《Mikrochimica acta》2014,181(1-2):97-104
We describe a simple method for the simultaneous determination of organolead and organomanganese compounds in seawater samples. It is based on ultrasound-assisted emulsification microextraction. Trimethyllead, triethyllead, tetraethyllead, cyclopentadienylmanganese tricarbonyl and its methyl derivative were separated and determined using gas chromatography and mass spectrometry. Trimethyllead and triethyllead were derivatized with sodium tetraphenylborate before being submitted to the preconcentration step. Detection limits ranged from 7.0 to 41 ng L?1 depending on the compound. Recoveries ranged from 84 to 118 %, depending on the compound and the sample analyzed. Seawater samples were collected at different sites of the Cartagena Bay and none of the target analytes were found at levels above the corresponding detection limits. Figure
The most relevant organomanganese and organolead compounds can be monitorized in seawaters by using a relatively simple instrumentation (Gas chromatography–mass spectrometry). Advantage is taken of ultrasound-assisted emulsification microextraction that involves minimal amounts of organic solvents 相似文献
873.
Lidia S. Konstantinova Ekaterina A. Knyazeva Natalia V. Obruchnikova Nadezhda V. Vasilieva Irina G. Irtegova Yulia V. Nelyubina Irina Yu. Bagryanskaya Leonid A. Shundrin Zhanna Yu. Sosnovskaya Andrey V. Zibarev Oleg A. Rakitin 《Tetrahedron》2014
A new general procedure for the selective synthesis of 1,2,5-thiadiazole 2-oxides (including fused derivatives) 8a,b,c,g,h from the reaction of vic-glyoximes with S2Cl2 and pyridine in acetonitrile was elaborated together with general procedure for the synthesis of 1,2,5-thiadiazoles 7a–i, 10, 12, and 14 from the same starting materials and reagents. Molecular structures of 3,4-dimethyl-1,2,5-thiadiazole 2-oxide 8a and [1,2,5]thiadiazolo[3,4-b]quinoxaline 10 were confirmed by single-crystal X-ray diffraction. Electrochemical properties of 1,2,5-thiadiazole 2-oxides 8 were studied by cyclic voltammetry and different behavior was observed for monocyclic and benzo-fused derivatives. With compounds 8g and 17, previously unknown deoxygenation of 2,1,3-benzothiadiazole 1-oxides was discovered by electrochemical reduction, and resulted 2,1,3-benzothiadiazoles 7g and 19 were detected in the forms of their radical anions by EPR spectroscopy combined with DFT calculations. 相似文献
874.
An efficient protocol for the synthesis of highly functionalized 2-aminoindolizines and pyrido[3,2-a]indolizines has been achieved via the reaction of N-RC(O)CH2-2-chloropyridinium bromides with 2-amino-1,1,3-tricyanopropene in the presence of Et3N. The reaction of N-allyl-2-chloropyridinium bromide with 2-amino-1,1,3-tricyanopropene in the presence of Et3N gives 3-[1-allylpyridin-2(1Н)-ylidene]-2-aminoprop-1-ene-1,1,3-tricarbonitrile, which could be cyclized to give [2-amino-(2-amino-3-vinylindolizin-1-yl)methylene]malononitrile upon treatment with KOH–DMF. 相似文献
875.
Dr. Natalia G. Zhegalova Dr. Sergey A. Dergunov Steven T. Wang Prof. Eugene Pinkhassik Prof. Mikhail Y. Berezin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10292-10297
We have developed a novel design of optical nanothermometers that can measure the surrounding temperature in the range of 20–85 °C. The nanothermometers comprise two organic fluorophores encapsulated in a crosslinked polymethacrylate nanoshell. The role of the nanocapsule shell around the fluorophores is to form a well‐defined and stable microenvironment to prevent other factors besides temperature from affecting the dyes’ fluorescence. The two fluorophores feature different temperature‐dependent emission profiles; a fluorophore with relatively insensitive fluorescence (rhodamine 640) serves as a reference whereas a sensitive fluorophore (indocyanine green) serves as a sensor. The sensitivity of the nanothermometers depends on the type of nanocapsule‐forming lipid and is affected by the phase transition temperature. Both the fluorescence intensity and the fluorescence lifetime can be utilized to measure the temperature. 相似文献
876.
Evgeniia S. Vikulova Kseniya V. Zherikova Ilia V. Korolkov Ludmila N. Zelenina Tamara P. Chusova Sergey V. Sysoev Nina I. Alferova Natalia B. Morozova Igor K. Igumenov 《Journal of Thermal Analysis and Calorimetry》2014,118(2):849-856
The series of adducts of magnesium beta-diketonates with diamimes namely Mg(thd)2(tmeda) 1 and four new complexes Mg(thd)2(tmpda) 2, Mg(thd)2(pda) 3, Mg(ptac)2(tmeda) 4, Mg(tfac)2(tmeda) 5 [beta-diketonates = R1C(O)CHC(O)R2: thd (R1 = R2 = t Bu), ptac (R1 = t Bu, R2 = CF3), tfac (R1 = Me, R2 = CF3); diamines = R2N(CH2) n NR2: tmeda (n = 2, R = Me), tmpda (n = 3, R = Me), pda (n = 3, R = H)] were synthesized in order to investigate the influence of both ligand types on the thermochemical properties of these compounds. The thermal behavior of the complexes in the condensed phase was investigated by thermogravimetry and differential scanning calorimetry; the thermodynamic parameters of phase transitions were determined. The saturated vapor pressure of solid complexes Mg(thd)2(tmeda) and Mg(tfac)2(tmeda) were measured by the transmission method giving the enthalpies and entropies of sublimation processes. The reliable thermodynamic data for compound Mg(thd)2(tmeda) were obtained with the assistance of X-ray diffraction and the static method of saturated and unsaturated vapor pressure measurements. 相似文献
877.
Maxim Bykov Stella Chariton Elena Bykova Saiana Khandarkhaeva Timofey Fedotenko Alena V. Ponomareva Johan Tidholm Ferenc Tasndi Igor A. Abrikosov Pavel Sedmak Vitali Prakapenka Michael Hanfland Hanns‐Peter Liermann Mohammad Mahmood Alexander F. Goncharov Natalia Dubrovinskaia Leonid Dubrovinsky 《Angewandte Chemie (International ed. in English)》2020,59(26):10321-10326
Polynitrides are intrinsically thermodynamically unstable at ambient conditions and require peculiar synthetic approaches. Now, a one‐step synthesis of metal–inorganic frameworks Hf4N20?N2, WN8?N2, and Os5N28?3 N2 via direct reactions between elements in a diamond anvil cell at pressures exceeding 100 GPa is reported. The porous frameworks (Hf4N20, WN8, and Os5N28) are built from transition‐metal atoms linked either by polymeric polydiazenediyl (polyacetylene‐like) nitrogen chains or through dinitrogen units. Triply bound dinitrogen molecules occupy channels of these frameworks. Owing to conjugated polydiazenediyl chains, these compounds exhibit metallic properties. The high‐pressure reaction between Hf and N2 also leads to a non‐centrosymmetric polynitride Hf2N11 that features double‐helix catena‐poly[tetraz‐1‐ene‐1,4‐diyl] nitrogen chains [?N?N?N=N?]∞. 相似文献
878.
Iga Stryjak Natalia Warmuziska Joanna Bogusiewicz Kamil uczykowski Barbara Bojko 《Journal of separation science》2020,43(9-10):1867-1878
The limiting factor in conventional quality assessments of transplanted organs, namely the invasiveness of tissue sample collection, has prompted much research on the field of transplantology to focus on the development of alternative evaluation methods of organ quality. In the present project, we undertake the challenge to address the need for a new analytical solution for graft quality assessments by using a novel metabolomic diagnostic protocol based on low‐invasive solid‐phase microextraction. Solid‐phase microextraction probes of ca. 0.2 mm coated with 4 mm long mixed‐mode extraction phase were inserted into rabbit kidneys immediately following euthanasia and after 2, 4, 6, and 21 h of preservation. Liquid chromatography–mass spectrometry analysis of the extracts was performed with the use of a reversed phase column and a Q‐Exactive Focus mass spectrometer operated in positive ionization mode. Statistical analysis of significantly changing compounds revealed metabolic profile changes in kidneys induced by ischemia and oxidative stress as a function of the duration of cold storage. The most pronounced alterations were reflected in levels of essential amino acids and purine nucleosides. Our findings demonstrate that the proposed approach may be successfully used to monitor changes in the metabolic profile of organs over time of preservation. 相似文献
879.
Alexandra S. Antonova Marina A. Vinokurova Pavel A. Kumandin Natalia L. Merkulova Anna A. Sinelshchikova Mikhail S. Grigoriev Roman A. Novikov Vladimir V. Kouznetsov Kirill B. Polyanskii Fedor I. Zubkov 《Molecules (Basel, Switzerland)》2020,25(22)
The ring rearrangement metathesis (RRM) of a trans-cis diastereomer mixture of methyl 3-allyl-3a,6-epoxyisoindole-7-carboxylates derived from cheap, accessible and renewable furan-based precursors in the presence of a new class of Hoveyda–Grubbs-type catalysts, comprising an N→Ru coordinate bond in a six-membered ring, results in the difficult-to-obtain natural product-like cyclopenta[b]furo[2,3-c]pyrroles. In this process, only one diastereomer with a trans-arrangement of the 3-allyl fragment relative to the 3a,6-epoxy bridge enters into the rearrangement, while the cis-isomers polymerize almost completely under the same conditions. The tested catalysts are active in the temperature range from 60 to 120 °C at a concentration of 0.5 mol % and provide better yields of the target tricycles compared to the most popular commercially available second-generation Hoveyda–Grubbs catalyst. The diastereoselectivity of the intramolecular Diels–Alder reaction furan (IMDAF) reaction between starting 1-(furan-2-yl)but-3-en-1-amines and maleic anhydride, leading to 3a,6-epoxyisoindole-7-carboxylates, was studied as well. 相似文献
880.
Gabrielle A. Leith Allison M. Rice Brandon J. Yarbrough Anna A. Berseneva Richard T. Ly Charles N. Buck Denis Chusov Amy J. Brandt Donna A. Chen Benjamin W. Lamm Morgan Stefik Kenneth S. Stephenson Mark D. Smith Aaron K. Vannucci Perry J. Pellechia Sophya Garashchuk Natalia B. Shustova 《Angewandte Chemie (International ed. in English)》2020,59(15):6000-6006
The effect of donor (D)–acceptor (A) alignment on the materials electronic structure was probed for the first time using novel purely organic porous crystalline materials with covalently bound two‐ and three‐dimensional acceptors. The first studies towards estimation of charge transfer rates as a function of acceptor stacking are in line with the experimentally observed drastic, eight‐fold conductivity enhancement. The first evaluation of redox behavior of buckyball‐ or tetracyanoquinodimethane‐integrated crystalline was conducted. In parallel with tailoring the D‐A alignment responsible for “static” changes in materials properties, an external stimulus was applied for “dynamic” control of the electronic profiles. Overall, the presented D–A strategic design, with stimuli‐controlled electronic behavior, redox activity, and modularity could be used as a blueprint for the development of electroactive and conductive multidimensional and multifunctional crystalline porous materials. 相似文献