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991.
Biogas generally contains significant quantities of carbon dioxide in addition to methane. A bubbling column reactor operating at atmospheric pressure is proposed for cheap separation and a Mettler RC1 reaction calorimeter was used to build a simplified empirical model for measuring the molar heat of solubility of CO2 in aqueous solutions of monoethanolamine (MEA). Determinations were performed in 12 mass% MEA solutions regenerated at atmospheric pressure and reflux temperature for 3 h. Flows of CO2 from 174 to 917 mL min?1 were used at a reactor temperature of 283 to 353 K. 相似文献
992.
The analysis of the cellular lipidic fraction of bacteria is described. After hydrolysis and methylation, the fatty acid methyl esters (FAMEs) are determined by 1-D GC using the Sherlock MIDI bacteria identification system, by comprehensive GC (GC x GC) and by GC-MS in electron impact (EI) and positive chemical ionisation (PCI) mode. With GC x GC, the enhanced selectivity and group type separation provides a more complete elucidation of the fatty acids in microorganisms. GC-EI-MS and GC-PCI-MS were helpful for confirmation. The bacteria selected in this study are Brevundimonas diminuta, Chryseobacterium gleum and Stenotrophomonas maltophilia. 相似文献
993.
Suijkerbuijk BM Klein Gebbink RJ 《Angewandte Chemie (International ed. in English)》2008,47(39):7396-7421
The coordination chemistry of porphyrins has traditionally involved the ability of the porphyrin's tetrapyrrolic core to accommodate metal ions of varying charges and sizes, and on the organometallic chemistry of the resulting metalloporphyrins. However, the organometallic chemistry of porphyrins is not necessarily restricted to the metal bound in the porphyrin core, but can also be extended to the porphyrin periphery, be it through direct metalation of the porphyrin macrocycle at the meso or beta position, or by attachment to or merger of the porphyrin skeleton with ligands, followed by metalation. This Review focuses on the synthetic strategies used for porphyrins with peripheral metal-carbon bonds. The exciting results that have been produced underscore the importance and future potential of this field. 相似文献
994.
The effect of ultrasound waves in an ultrasonic resonator cell on ozone generation by a hollow needle to plate electrical discharge enhanced by the airflow through the needle is experimentally investigated. It was found that the application of ultrasound waves increases ozone generation for discharge when the needle is negatively biased, and has no effect on ozone generation for the discharge when the needle is biased positively. We try to explain the influence of ultrasound on the discharge mechanisms. 相似文献
995.
van Oort B van Hoek A Ruban AV van Amerongen H 《The journal of physical chemistry. B》2007,111(26):7631-7637
Nonphotochemical quenching (NPQ) of chlorophyll fluorescence plays an important role in the protection of plants against excessive light. Fluorescence quenching of the major light-harvesting complex (LHCII) provides a model system to study the mechanism of NPQ. The existence of both quenched and nonquenched states of LHCII has been postulated. We used time-resolved fluorescence and hydrostatic pressure to study differences between these states. Pressure shifts the thermodynamic equilibrium between the two states. The estimated volume difference was 5 mL/mol, indicating a local conformational switch. The estimated free energy difference was 7.0 kJ/mol: high enough to keep the quenched state population low under normal conditions, but low enough to switch in a controlled way. These properties are physiologically relevant properties, because they guarantee efficient light harvesting, while at the same time maintaining the capacity to switch to a quenched state. These results indicate that conformational changes of LHCII can play an important role in NPQ. 相似文献
996.
Sutter M Oliveira S Sanders NN Lucas B van Hoek A Hink MA Visser AJ De Smedt SC Hennink WE Jiskoot W 《Journal of fluorescence》2007,17(2):181-192
The fluorescent dye Nile red was used as a probe for the sensitive detection of large, denatured aggregates of the model protein
β-galactosidase (E. coli) in solution. Aggregates were formed by irreversible heat denaturation of β-galactosidase below and above the protein’s unfolding
temperature of 57.4°C, and the presence of aggregates in heated solutions was confirmed by static light scattering. Interaction
of Nile red with β-galactosidase aggregates led to a shift of the emission maximum (λ
max) from 660 to 611 nm, and to an increase of fluorescence intensity. Time-resolved fluorescence and fluorescence correlation
spectroscopy (FCS) measurements showed that Nile red detected large aggregates with hydrodynamic radii around 130 nm. By steady-state
fluorescence measurements, it was possible to detect 1 nM of denatured and aggregated β-galactosidase in solution. The comparison
with size exclusion chromatography (SEC) showed that native β-galactosidase and small aggregates thereof had no substantial
effect on the fluorescence of Nile red. Large aggregates were not detected by SEC, because they were excluded from the column.
The results with β-galactosidase demonstrate the potential of Nile red for developing complementary analytical methods that
overcome the size limitations of SEC, and can detect the formation of large protein aggregates at early stages. 相似文献
997.
Vercaemst C Ide M Allaert B Ledoux N Verpoort F Van Der Voort P 《Chemical communications (Cambridge, England)》2007,(22):2261-2263
A novel synthesis of diastereoselective pure periodic mesoporous ethenylene-silicas is presented, using (a) the homemade E-diastereoisomer of bis(triethoxysilyl)ethene, (b) a more efficient extraction procedure of the template P123 and (c) an ultra-fast synthesis procedure. 相似文献
998.
Hermans I Moens B Peeters J Jacobs P Sels B 《Physical chemistry chemical physics : PCCP》2007,9(31):4269-4274
The thermal reaction of olefins with nitrous oxide was recently put forward as a promising synthetic ketone source. The 1,3-dipolar cycloaddition of N(2)O to the C=C double bond, forming a 4,5-dihydro-[1,2,3]oxadiazole intermediate, was predicted to be the first elementary reaction step. This oxadiazole can subsequently decompose to the desired carbonyl product and N(2)via a hydrogen shift. In this contribution, Potential Energy Surfaces are constructed at the reliable G2M level of theory and used to evaluate thermal rate constants by Transition State Theory. Compelling theoretical and experimental evidence is presented that an oxadiazole intermediate not only can undergo a hydrogen shift, but eventually also a methyl- or even an alkyl-shift. Special emphasis is also given on a hitherto neglected decomposition of the oxadiazole via a concerted C-C and N-O cleavage. For some substrates, such as internal olefins, this diazo route is negligibly slow, compared to the ketone path, leaving no marks on the selectivity. For cyclopentene the diazo cleavage was however found to be nearly as fast as the desired ketone route. However, the diazo compound, viz. 5-diazopentanal, reconstitutes the oxadiazole much faster upon ring-closure than it is converted to side-products. Therefore, a pre-equilibrium between the diazoalkanal and the oxadiazole is established, explaining the high ketone yield. On the other hand, for primary alkenes, such a concerted C-C and N-O cleavage to diazomethane is identified as an important side reaction, producing aldehydes with the loss of one C-atom. For these substrates, the bimolecular back-reaction of the C(n-1) aldehyde and diazomethane is too slow to sustain an equilibrium with the oxadiazole; diazomethane rather reacts with the substrate to form cyclopropane derivatives. The overall selectivity is thus determined by a combination of H-, methyl- or alkyl-shift, and the eventual impact of a diazo cleavage in the oxadiazole intermediate. 相似文献
999.
Suijkerbuijk BM Aerts BN Dijkstra HP Lutz M Spek AL van Koten G Klein Gebbink RJ 《Dalton transactions (Cambridge, England : 2003)》2007,(13):1273-1276
The potential of "click" 1,2,3-triazoles to act as mono-dentate ligands in late transition metal complexes is explored relative to other commonly-used Lewis bases and it is shown that their coordination strength, determined by their 1- and 4-substituents, is easily tunable. 相似文献
1000.
Wim Christiaens Christian de Ronde Bart D’Hooghe Federico Holik 《International Journal of Theoretical Physics》2010,49(12):3061-3068
In this paper we present Aerts’ vessels of water model which violates Bell inequalities, and discuss how this fits in the
Creation Discovery View in the context of the Operational Quantum Logic approach. We analyze the 2 different ways in which
correlation is classically observed, either as pre-existing ‘independent of measurement’ or established by sending a signal,
hence limited by the speed of light. As the Aerts’ model shows, there is yet a third possibility, namely a situation in which
correlation is potentially present, but only actualized to its full extent by the act of measurement. This creation-discovery
view can be applied to the quantum mechanical situation of two entangled photons, and shows that in the debate of understanding
‘what is really going on in Aspects experiments’ an alternative explanation can be found, in which potentiality, creation
and discovery play a central role. 相似文献