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71.
A Power Interruption Technique for Investigation of Temperature Difference in Stabilized Low Direct-Current Arc Burning in Pure Argon on Atmospheric Pressure 下载免费PDF全文
M. M. Kuzmanovic J. J. Savovic D. P. Rankovic M. Stoiljkovic A. Antic Jovanovic M.S. Pavlovic M. Marinkovic 《中国物理快报》2008,25(4):1376-1379
Plasma of argon stabilized arc column, in a current range 3-11 A, is investigated using emission spectrometric diagnostic techniques. Temperatures are evaluated using several methods: argon line to adjacent recombinational continuum intensity ratio, absolute emissivity of argon line, measurement of electron number density, and power interruption. Electron number density is evaluated from absolute emissivity of recombinational continuum. The difference between electron Te and heavy particle Th temperature ranged from 4500 K for 3 A to 2300 K for 11A arc current. By comparing the present with the previously obtained results, using the same arc device but with the introduction of water aerosol, it is concluded that water aerosol reduces the difference Te - Th and brings plasma closer to the partial thermodynamic equilibrium state. 相似文献
72.
Postsynthetic Metal and Ligand Exchange in MFU‐4l: A Screening Approach toward Functional Metal–Organic Frameworks Comprising Single‐Site Active Centers 下载免费PDF全文
Dmytro Denysenko Dr. Jelena Jelic Prof. Dr. Karsten Reuter Prof. Dr. Dirk Volkmer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8188-8199
The isomorphous partial substitution of Zn2+ ions in the secondary building unit (SBU) of MFU‐4l leads to frameworks with the general formula [MxZn(5–x)Cl4(BTDD)3], in which x≈2, M=MnII, FeII, CoII, NiII, or CuII, and BTDD=bis(1,2,3‐triazolato‐[4,5‐b],[4′,5′‐i])dibenzo‐[1,4]‐dioxin. Subsequent exchange of chloride ligands by nitrite, nitrate, triflate, azide, isocyanate, formate, acetate, or fluoride leads to a variety of MFU‐4l derivatives, which have been characterized by using XRPD, EDX, IR, UV/Vis‐NIR, TGA, and gas sorption measurements. Several MFU‐4l derivatives show high catalytic activity in a liquid‐phase oxidation of ethylbenzene to acetophenone with air under mild conditions, among which Co‐ and Cu derivatives with chloride side‐ligands are the most active catalysts. Upon thermal treatment, several side‐ligands can be transformed selectively into reactive intermediates without destroying the framework. Thus, at 300 °C, CoII‐azide units in the SBU of Co‐MFU‐4l are converted into CoII‐isocyanate under continuous CO gas flow, involving the formation of a nitrene intermediate. The reaction of CuII‐fluoride units with H2 at 240 °C leads to CuI and proceeds through the heterolytic cleavage of the H2 molecule. 相似文献
73.
Dr. Stepas Toliautas Dr. Jelena Dodonova Audrius Žvirblis Ignas Čiplys Artūras Polita Dr. Andrius Devižis Prof. Sigitas Tumkevičius Prof. Juozas Šulskus Dr. Aurimas Vyšniauskas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10342-10349
Molecular rotors are a class of fluorophores that enable convenient imaging of viscosity inside microscopic samples such as lipid vesicles or live cells. Currently, rotor compounds containing a boron-dipyrromethene (BODIPY) group are among the most promising viscosity probes. In this work, it is reported that by adding heavy-electron-withdrawing −NO2 groups, the viscosity-sensitive range of a BODIPY probe is drastically expanded from 5–1500 cP to 0.5–50 000 cP. The improved range makes it, to our knowledge, the first hydrophobic molecular rotor applicable not only at moderate viscosities but also for viscosity measurements in highly viscous samples. Furthermore, the photophysical mechanism of the BODIPY molecular rotors under study has been determined by performing quantum chemical calculations and transient absorption experiments. This mechanism demonstrates how BODIPY molecular rotors work in general, why the −NO2 group causes such an improvement, and why BODIPY molecular rotors suffer from undesirable sensitivity to temperature. Overall, besides reporting a viscosity probe with remarkable properties, the results obtained expand the general understanding of molecular rotors and show a way to use the knowledge of their molecular action mechanism for augmenting their viscosity-sensing properties. 相似文献
74.
Dimitrije Djukanovic Milos Petkovic Milena Simic Predrag Jovanovic Gordana Tasic Vladimir Savic 《Tetrahedron letters》2018,59(10):914-917
A one-pot, domino process was developed as an alternative approach for the preparation of 2-unsubstituted imidazolones. The methodology utilizes readily accessible bisamides, which upon a dehydration/cyclisation sequence produced imidazolones in good yields. The transformation relies on the compatibility of the dehydrating agent and base, and the reaction conditions tolerate various functional groups. 相似文献
75.
Slobodan??iri?Email authorView authors OrcID profile Violeta?Miti? Sne?ana?Jovanovi? Marija?Ili? Jelena?Nikoli? Gordana?Stojanovi? Vesna?Stankov Jovanovi? 《Mikrochimica acta》2018,185(12):556
The authors report on a novel sorbent (thermally treated natural zeolite; clinoptilolite) for use in dispersive micro-solid phase extraction (D-μ-SPE) of polycyclic aromatic hydrocarbons (PAHs) from water samples. The method was applied to the D-μ-SPE of 16 priority PAHs which then were quantified by gas chromatography with mass spectrometric detection (GC-MS). The method was validated in terms of specificity and selectivity, linearity and linear range, accuracy, precision, uncertainty, limits of detection and quantification. Figures of merit include (a) linear analytical ranges between 2.08 and 208 ppb, and (b) detection limits in the range from 0.01 to 0.92 ppb. The method was successfully applied to the determination of PAHs in river waters. 相似文献
76.
LetX andY be closed subspaces of the Lorentz sequence spaced(v, p) and the Orlicz sequence spacel
M
, respectively. It is proved that every bounded linear operator fromX toY is compact whenever
As an application, the reflexivity of the space of bounded linear operators acting fromd(v, p) tol
M
is characterized.
This research was partially supported by the Estonian Science Foundation Grant 3055. 相似文献
77.
Santos O Kosoric J Hector MP Anderson P Lindh L 《Journal of colloid and interface science》2008,318(2):175-182
The salivary protein statherin is known to adsorb selectively onto hydroxyapatite (HA), which constitutes the main mineral of the tooth enamel. This adsorption is believed to be crucial for its function as an inhibitor of primary (spontaneous) and secondary (crystal growth) precipitation of calcium phosphate salts present in saliva. A fragment corresponding to the first 21 N-terminus amino acids of statherin (StN21) was previously found to reduce the rate of demineralization of HA. Therefore, the interfacial properties of this peptide and statherin onto silica, hydrophobized silica and HA discs was studied by in situ ellipsometry. Their reversibility induced by dilution and elutability induced by buffer and sodium dodecyl sulfate (SDS) was also determined. The results revealed that statherin adsorbed at a greater extent onto the HA as compared to StN21, suggesting that the hydrogen bonding between the uncharged polar residues at the C-terminal region of statherin and HA contributes to its adsorption. However, on both silica surfaces the peptide adsorption appeared to proceed in a similar way. Onto the hydrophobized silica the adsorption of both peptides was suggested to occur either via multilayer formation or adsorption of aggregates from solution, while onto the hydrophilic silica adsorption of peptide aggregates from solution was the suggested mechanism. Further, both peptides were observed to be strongly adsorbed onto HA, even after SDS treatment, in comparison to the layers adsorbed onto hydrophobized silica. Both peptide layers were found to be weakly adsorbed onto the hydrophilic silica surface as they were totally removed by buffer dilution. 相似文献
78.
An optional approach in the meteorological service Quality Management System (QMS) based on the case study of the Republic
Hydrometeorological Service (MHS) of Serbia is presented and discussed in this paper. The idea is to use the ISO/IEC 17025
standard as a base for its QMS development. Main reasons for such a decision and the elements of the implemented solution
are presented and discussed. Meteorological testing processes of the MHS of Serbia and relevant ISO/IEC 17025 scope of accreditation
are presented. After establishing competencies in meteorological, environmental, and hydrological testing, the MHS of Serbia
will develop an integrative ISO 9001 QMS. The Serbian case study could be taken into consideration as one of the options related
to the future World Meteorological Organization Quality Management Framework. 相似文献
79.
80.
Hydrogen Bonding between Metal‐Ion Complexes and Noncoordinated Water: Electrostatic Potentials and Interaction Energies 下载免费PDF全文
Jelena M. Andrić Majda Z. Misini‐Ignjatović Dr. Jane S. Murray Prof. Peter Politzer Prof. Snežana D. Zarić 《Chemphyschem》2016,17(13):2035-2042
The hydrogen bonding of noncoordinated water molecules to each other and to water molecules that are coordinated to metal‐ion complexes has been investigated by means of a search of the Cambridge Structural Database (CSD) and through quantum chemical calculations. Tetrahedral and octahedral complexes that were both charged and neutral were studied. A general conclusion is that hydrogen bonds between noncoordinated water and coordinated water are much stronger than those between noncoordinated waters, whereas hydrogen bonds of water molecule in tetrahedral complexes are stronger than in octahedral complexes. We examined the possibility of correlating the computed interaction energies with the most positive electrostatic potentials on the interacting hydrogen atoms prior to interaction and obtained very good correlation. This study illustrates the fact that electrostatic potentials computed for ground‐state molecules, prior to interaction, can provide considerable insight into the interactions. 相似文献