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831.
Olga V. Mikolaichuk Aleksandra V. Protas Elena A. Popova Alexander S. Mikherdov Ilya V. Kornyakov Rostislav E. Trifonov 《Journal of heterocyclic chemistry》2020,57(6):2539-2547
A series of tris(5-aryl-1H-tetrazol-1-yl)methanes ( 3a-3g ) and 2-dichloromethyl-5-aryl-2H-tetrazoles ( 4a-4d ) were synthesized by reaction of 5-aryl-NH-tetrazoles with trichloromethane in strong aqueous basic condition. The compounds obtained were fully characterized by means of HRESI-MS, 1H and 13C{1H} NMR spectroscopies, as well as by single-crystal X-ray diffraction (for 3a , 3b , 4d ). Inspection of the X-ray diffraction data and Hirshfeld surface analysis for tris(5-aryl-1H-tetrazol-1-yl)methanes 3a , b and 2-dichloromethyl-5-aryl-2H-tetrazole 4d showed the presence of noncovalent π-hole•••lone pair and π-hole•••π interactions involving electrophilic tetrazole carbon atom. 相似文献
832.
Aleksandr A. Savateev Nataliya A. Shtil Aleksandra A. Chaikovskaya Radomyr V. Smaliy Yurii G. Vlasenko Alexandr N. Kostyuk 《Heteroatom Chemistry》2015,26(1):91-100
A simple approach to vicinal pyrrolylphosphane aldehydes was developed. The reaction of Alder's dimer 1 with a set of pyrrolylphosphane derivatives—its oxides, sulfides, and selenides—was studied in detail. While Alder's dimer reacted with phosphane oxides and sulfides at the O and S atoms, phosphane selenides 4a–c were found to be suitable for the introduction of the formyl group into the pyrrole ring. The reaction of highly electrophilic Alder's dimer with pyrrolylphosphane selenides proceeded predominantly at the pyrrolyl nuclei, affording the corresponding aldehydes. The phosphoroselenoyl groups of aldehydes 11 were reduced either with Raney Ni or hexamethylphosphorustriamide under mild conditions, affording pyrrolylphosphane aldehydes 12 . 相似文献
833.
Aleksandra Szkudlarek Wojciech Szmyt Czesław Kapusta Ivo Utke 《Applied Physics A: Materials Science & Processing》2014,117(4):1715-1726
In this work, we review the single-adsorbate time-dependent continuum model for focused electron beam-induced deposition (FEBID). The differential equation for the adsorption rate will be expressed by dimensionless parameters describing the contributions of adsorption, desorption, dissociation, and the surface diffusion of the precursor adsorbates. The contributions are individually presented in order to elucidate their influence during variations in the electron beam exposure time. The findings are condensed into three new scaling laws for pulsed exposure FEBID (or FEB-induced etching) relating the lateral resolution of deposits or etch pits to surface diffusion and electron beam exposure dwell time for a given adsorbate depletion state. 相似文献
834.
Zorica Ž. Lazarević Čedomir Jovalekić Valentin N. Ivanovski Aleksander Rečnik Aleksandra Milutinović Božidar Cekić Nebojša Ž. Romčević 《Journal of Physics and Chemistry of Solids》2014
ZnFe2O4 was prepared by a soft mechanochemical route from two starting combinations of powders: (1) Zn(OH)2/α-Fe2O3 and (2) Zn(OH)2/Fe(OH)3 mixed in a planetary ball mill. The mechanochemical treatment provoked reaction leading to the formation of the ZnFe2O4 spinel phase that was monitored by XRD, TEM, IR and Raman spectroscopy. The spinel phase was first observed after 4 h of milling and its formation was completed after 18 h in both the cases of starting precursors. The synthesized ZnFe2O4 has a nanocrystalline structure with a crystallite size of about 20.3 and 17.6 nm, for the cases (1) and (2), respectively. In the far-infrared reflectivity spectra are seen four active modes. Raman spectra suggest an existence of mixed spinel structure in the obtained nanosamples. In order to confirm phase formation and cation arrangement, Mössbauer measurements were done. Estimated degree of inversion is about 0.58 for both starting mixtures. The magnetic properties of the prepared ZnFe2O4 powders were also studied. The results show that the samples have a typical superparamagnetic-like behavior at room temperature. Higher values of magnetization in the case of samples obtained with starting mixture (2) suggest somewhat higher degree of cation inversion. 相似文献
835.
Aleksandra Č. Mišan Neda M. Mimica-Dukić Anamarija I. Mandić Marijana B. Sakač Ivan Lj. Milovanović Ivana J. Sedej 《Central European Journal of Chemistry》2011,9(1):133-142
Rapid Resolution HPLC/DAD method, on a 1.8 μm, 4.6×50 mm column, was developed to enable a rapid separation of a mixture of
17 compounds, which consisted of hydroxybenzoic acids, hydroxycinnamic acids, flavones, flavonols, flavanone, flavonol-glycoside
and antraquinone, in a single run, within 22 minutes. The developed method is precise, accurate and sensitive enough for simultaneous
quantitative evaluation of major compounds in crude and hydrolyzed extracts of parsley, buckthorn, mint, caraway and birch.
In order to overcome the inability to quantify all the phenolic compounds present in the samples caused by lack of external
standards, HPLC approaches for the total phenolic content estimation based on sum of all integrated peak areas were made.
These results were compared with the total phenolic content determined by Folin-Cioacalteu method. Although the correlation
between the series of data was not significant (p<0.05), the difference between the results of total phenolic content obtained spectrophotometrically and by HPLC was not high
in the case of parsley, buckthorn and mint extract. Regarding the obtained results, the HPLC approach could serve as an excellent
tool for total phenolic content estimation, without the need for complete identification of the individual compounds.
相似文献
836.
Grubba R Wiśniewska A Baranowska K Matern E Pikies J 《Dalton transactions (Cambridge, England : 2003)》2011,40(9):2017-2024
Reactions of (Et(2)N)(2)P-P(SiMe(3))Li with [Cp(2)MCl(2)] (M = Zr, Hf) in toluene or pentane yield the related terminal phosphanylphosphido complexes [Cp(2)M(Cl){η(1)-(Me(3)Si)P-P(NEt(2))(2)}]. The solid state structure of [Cp(2)Hf(Cl){η(1)-(Me(3)Si)P-P(NEt(2))(2)}] was established by single crystal X-ray diffraction. The reaction of (Et(2)N)(2)P-P(SiMe(3))Li with [Cp(2)ZrCl(2)] in THF or DME solutions leads to the formation of deep red crystals of the first neutral diamagnetic zirconocene-phosphanylphosphinidene dimer [Cp(2)Zr{μ(2)-P-P(NEt(2))(2)}(2)ZrCp(2)]. The molecular structure of this compound was confirmed by X-ray diffraction. The reactions of (R(2)N)(2)P-P(SiMe(3))Li with [CpZrCl(3)] yield the related tetraphosphetanes R(2)NP(μ(2)-PSiMe(3))(2)PNR(2), which apparently are formed as a result of a transfer of NR(2) groups from a P atom to the Zr atom. 相似文献
837.
Zomer B Collé L Jedyńska A Pasterkamp G Kooter I Bloemen H 《Analytical and bioanalytical chemistry》2011,401(9):2945-2954
Acridinium esters traditionally are triggered using basic hydrogen peroxide. By serendipity, we have found that acridinium
esters can also be triggered with emission of chemiluminescence by reductive triggering, e.g., by zinc metal or reduced forms
of ferric and cupric salts. Furthermore, organic reducing compounds like dithiothreitol, tricarboxyethylphosphine or glutathione
could be used in combination with organic oxidants like quinones or inorganic ferric or cupric salts. Mechanisms are proposed
which involve the intermediacy of superoxide. Two forms of reactive oxygen species (i.e., hydrogen peroxide and superoxide)
could be discriminated based on differences in kinetics. Some applications (improved detection of acridinium ester, use of
acridinium ester as redox probes) are discussed. 相似文献
838.
Kurach E Djurado D Rimarčik J Kornet A Wlostowski M Lukeš V Pécaut J Zagorska M Pron A 《Physical chemistry chemical physics : PCCP》2011,13(7):2690-2700
Two series of new soluble conjugated compounds containing tetrazine central ring have been synthesized. The three-ring compounds have been synthesized by the reaction of aryl cyanide (where aryl = thienyl, alkylthienyl, phenyl or pyridyl) with hydrazine followed by oxidation of the intermediate product with diethyl azodicarboxylate. The five-ring compounds have been prepared using two pathways: (i) reaction of 5-cyano-2,2'-bithiophene (or its alkyl derivative) with hydrazine; (ii) via Suzuki or Stille coupling of 3,6-bis(5-bromo-2-thienyl)-1,2,4,5-tetrazine with a stannyl or boronate derivative of alkylthiophene. UV-vis spectroscopic properties of the synthesized compounds are strongly dependent on the nature of the aryl group, the position of the solubilizing substituent and the length of the molecule, showing the highest bathochromic shift (λ(max) > 440 nm) for five-ring compounds with alkyl groups attached to C(α) carbon in the terminal thienyl ring. An excellent linear correlation has been found for spectroscopically determined and theoretically calculated (TD-B3LYP/6-31G*) excitation energies. With the exception of dipyridyl derivative, the calculated lowest unoccupied molecular orbital (LUMO) level of the investigated molecules changes within a narrow range (from -2.63 to -2.41 eV), in line with the electrochemical data, which show a reversible reduction process with the redox potential varying from -1.23 V to -1.33 V (vs. Fc/Fc(+)). The electrochemically determined positions of the LUMO levels are consistently lower by 0.9 to 1.2 eV with respect to the calculated ones. All molecules readily crystallize. Single crystal studies of 3,6-bis(2,2'-bithien-5-yl)-1,2,4,5-tetrazine show that it crystallizes in a P2(1)/c space group whose structural arrangement is not very favorable to the charge carriers flow within the crystal. Powder diffraction studies of other derivatives have shown that their structural organization is sensitive to the position of the solubilizing substituent. In particular, the presence of alkyl groups attached to C(α) carbon in the terminal thienyl ring promotes the formation of a lamellar-type supramolecular organization. 相似文献
839.
Trąbska J Wesełucha-Birczyńska A Zięba-Palus J Runge MT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(4):824-830
This work aimed at characterization of a black layer covering a Bronze Age (period VI) pot surface. To solve research problems plane polarized light microscopy (PLM), scanning microscopy with X-ray microanalyser (SEM/EDS), Raman and FTIR microspectroscopies were applied. Observation of the black layer under the PLM suggests that we deal with an opaque, isotropic layer, purposely put on leather-hard, burnished surface of a pot. No traces of organic substances that might have modified a pot surface before painting were detected. The black layer coats the pot with a continuous 0.2-0.4 μm thick layer. The black layer must have been applied while warm or hot. It is recognized that the black layer is a true painting layer. Spectroscopic analyses (Raman and FTIR) point that birch tar or a birch-pine tar had been applied. Carbon black should be definitely excluded. The analyzed organic substance is structurally ordered in various degrees, due to varying temperature influence. Some Raman spectra reveal, in second-order region of the spectrum (>2000 cm(-1)), the graphite presence. Scarce points reveal the presence of inorganic admixtures: clay minerals, feldspars and quartz. The next question is: Is it an organic paint or a carbon-based, "mixed" paint? Inorganic admixtures are only casual. Relatively high concentration of alumina is expected to have appeared due to aluminum mobility in acidic environment and this was provided by organic tar/pitch substances. Phosphorus (usually with calcium) mostly concentrates together with clay minerals. Thus, hypothesis on bone powder or ash addition to tar/pitch should be excluded. Some elements may originate not only from inorganic substances but also from wood ashes. 相似文献
840.
Aleksandra Kwiatkowska 《Israel Journal of Mathematics》2014,201(1):75-97
We show that the automorphism group, Aut(?), of a projective Fraïssé limit ?, whose natural quotient is the pseudo-arc, has a comeager conjugacy class. This generalizes an unpublished result of Izhar Oppenheim that Aut(?) (and consequently, the group of all homeomorphisms of the pseudo-arc) has a dense conjugacy class. We also present a simple proof of the result of Oppenheim. 相似文献