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721.
The 13C NMR α-substituent effects within the series methane to neopentane and ethene to isobutene have been calculated using Hartree—Fock perturbation theory with MINDO/3. The sign and order of magnitude of the calculated α-effects are in agreement with new experimental values, including effects of multiple substitution. 相似文献
722.
Marianne Sveaas Løiten Christian Gløgård Jo Klaveness Berit Fjærtoft 《Journal of chemical crystallography》1999,29(4):493-496
1-(4-Bromobenzyl)-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane, C13H15BrO3, has been synthesized from 4-bromophenylacetic acid chloride via the oxetan ester (3-methyl-3-oxetanyl)methyl-2-(4-bromophenyl)acetate. The crystal structure of the title compound has been determined at low temperature (120 K), by X-ray diffraction methods. This compound crystallizes in the monoclinic space group P21/n (No. 14), Z = 4, with lattice parametersa = 6.019(5), b = 20.990(5), c = 9.915(2) Å, and = 101.29(1)°. 相似文献
723.
Minghui Zhou Marianne Lankelma Jarl Ivar van der Vlugt Bas de Bruin 《Angewandte Chemie (International ed. in English)》2020,59(27):11073-11079
The metalloradical activation of o‐aryl aldehydes with tosylhydrazide and a cobalt(II) porphyrin catalyst produces cobalt(III)‐carbene radical intermediates, providing a new and powerful strategy for the synthesis of medium‐sized ring structures. Herein we make use of the intrinsic radical‐type reactivity of cobalt(III)‐carbene radical intermediates in the [CoII(TPP)]‐catalyzed (TPP=tetraphenylporphyrin) synthesis of two types of 8‐membered ring compounds; novel dibenzocyclooctenes and unprecedented monobenzocyclooctadienes. The method was successfully applied to afford a variety of 8‐membered ring compounds in good yields and with excellent substituent tolerance. Density functional theory (DFT) calculations and experimental results suggest that the reactions proceed via hydrogen atom transfer from the bis‐allylic/benzallylic C?H bond to the carbene radical, followed by two divergent processes for ring‐closure to the two different types of 8‐membered ring products. While the dibenzocyclooctenes are most likely formed by dissociation of o‐quinodimethanes (o‐QDMs) which undergo a non‐catalyzed 8π‐cyclization, DFT calculations suggest that ring‐closure to the monobenzocyclooctadienes involves a radical‐rebound step in the coordination sphere of cobalt. The latter mechanism implies that unprecedented enantioselective ring‐closure reactions to chiral monobenzocyclooctadienes should be possible, as was confirmed for reactions mediated by a chiral cobalt‐porphyrin catalyst. 相似文献
724.
Galina Rodionova Bård Hoff Marianne Lenes Øyvind Eriksen Øyvind Gregersen 《Cellulose (London, England)》2013,20(3):1167-1174
The barrier properties of microfibrillated cellulose (MFC) films were improved by heterogeneous gas-phase esterification using various combinations of trifluoroacetic acid anhydride, acetic acid and acetic anhydride. The temperature, reagent ratio and reaction time were varied in the experimental design. The effects of two different purification procedures on the barrier properties of esterified MFC films were investigated. Washing with water did not affect the barrier properties compared to those of the films that were not washed, while the use of diethyl ether led to improved barrier properties as measured by the contact angle (CA) of water. The chemical composition of the modified films was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Alterations in hydrophobicity and oxygen permeability were evaluated using dynamic CA and oxygen transmission rate measurements, respectively. 相似文献
725.
Brask J Damstrup ML Nielsen PM Holm HC Maes J De Greyt W 《Applied biochemistry and biotechnology》2011,163(7):918-927
An integrated biodiesel process that combines enzymatic esterification and alkaline transesterification is suggested. With
focus on the enzymatic step, the paper provides proof of concept and suggestions for further process development. Hence, palm
fatty acid distillate (PFAD) has been enzymatically converted to fatty acid methyl esters in a two-step process using the
immobilized lipase Novozym 435 in packed-bed columns. With only a small excess of methanol, the first reaction stage could
reduce the free fatty acid (FFA) content from 85% to 5%. After removal of water by simple phase separation, it was possible
to lower the FFA content to 2.5% in a second reaction stage. Both reaction stages are relatively fast with suggested reaction
times of 15 min in column 1 (productivity 10 kg/kg/h) and 30 min in column 2 (productivity 5 kg/kg/h), resulting in 15% FFA
after column 1 and 5% FFA after column 2. A lifetime study indicated that approximately 3,500 kg PFAD/kg Novozym 435 can be
treated in the first reaction stage before the enzyme has become fully inactivated. With further optimization, the enzymatic
process could be a real alternative to today’s sulfuric acid catalyzed process. 相似文献
726.
Gollmer A Arnbjerg J Blaikie FH Pedersen BW Breitenbach T Daasbjerg K Glasius M Ogilby PR 《Photochemistry and photobiology》2011,87(3):671-679
The development of efficient and selective luminescent probes for reactive oxygen species, particularly for singlet molecular oxygen, is currently of great importance. In this study, the photochemical behavior of Singlet Oxygen Sensor Green® (SOSG), a commercially available fluorescent probe for singlet oxygen, was examined. Despite published claims to the contrary, the data presented herein indicate that SOSG can, in fact, be incorporated into a living mammalian cell. However, for a number of reasons, caution must be exercised when using SOSG. First, it is shown that the immediate product of the reaction between SOSG and singlet oxygen is, itself, an efficient singlet oxygen photosensitizer. Second, SOSG appears to efficiently bind to proteins which, in turn, can influence uptake by a cell as well as behavior in the cell. As such, incorrect use of SOSG can yield misleading data on yields of photosensitized singlet oxygen production, and can also lead to photooxygenation‐dependent adverse effects in the system being investigated. 相似文献
727.
Nicolas Cinausero Nathalie Azema José‐Marie Lopez Cuesta Marianne Cochez Michel Ferriol 《先进技术聚合物》2011,22(12):1931-1939
Grafting of ethylene glycol methacrylate phosphate (EGMP) monomer polymerized from alumina nanoparticles has been performed in order to confer a better thermal stability and fire retardancy to PMMA and PS nanocomposites. Grafting and polymerization processes have been investigated using FTIR, TGA, and elemental analyses. Thermal stability and decomposition routes of monomer and polymer grafted alumina have been studied using thermogravimetric analysis and compared with the thermal behavior of the same alumina modified with octylsilane. The thermal stability of EGMP supported by the nanoparticles is higher than that of free EGMP. The incorporation of 5 wt% of both surface treated alumina in PMMA and PS leads to an improvement of thermal stability in comparison with unfilled polymers as well as nanocomposites containing unmodified alumina. Furthermore, the grafting of organic compounds on alumina also allows the peak of heat release rate measured using a cone calorimeter to be significantly reduced for PMMA nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
728.
Brian Drozdowski Yuhong Zhou Brad Kline Jared Spidel Yin Yin Chan Earl Albone Howard Turchin Qimin Chao Marianne Henry Jacqueline Balogach Eric Routhier Sina Bavari Nicholas C Nicolaides Philip M Sass Luigi Grasso 《Journal of immune based therapies and vaccines》2010,8(1):1-9
Background
Staphylococcal enterotoxins are considered potential biowarfare agents that can be spread through ingestion or inhalation. Staphylococcal enterotoxin B (SEB) is a widely studied superantigen that can directly stimulate T-cells to release a massive amount of proinflammatory cytokines by bridging the MHC II molecules on an antigen presenting cell (APC) and the Vβ chains of the T-cell receptor (TCR). This potentially can lead to toxic, debilitating and lethal effects. Currently, there are no preventative measures for SEB exposure, only supportive therapies.Methods
To develop a potential therapeutic candidate to combat SEB exposure, we have generated three human B-cell hybridomas that produce human monoclonal antibodies (HuMAbs) to SEB. These HuMAbs were screened for specificity, affinity and the ability to block SEB activity in vitro as well as its lethal effect in vivo.Results
The high-affinity HuMAbs, as determined by BiaCore analysis, were specific to SEB with minimal crossreactivity to related toxins by ELISA. In an immunoblotting experiment, our HuMAbs bound SEB mixed in a cell lysate and did not bind any of the lysate proteins. In an in vitro cell-based assay, these HuMAbs could inhibit SEB-induced secretion of the proinflammatory cytokines (INF-γ and TNF-α) by primary human lymphocytes with high potency. In an in vivo LPS-potentiated mouse model, our lead antibody, HuMAb-154, was capable of neutralizing up to 100 μg of SEB challenge equivalent to 500 times over the reported LD50 (0.2 μg), protecting mice from death. Extended survival was also observed when HuMAb-154 was administered after SEB challenge.Conclusion
We have generated high-affinity SEB-specific antibodies capable of neutralizing SEB in vitro as well as in vivo in a mouse model. Taken together, these results suggest that our antibodies hold the potential as passive immunotherapies for both prophylactic and therapeutic countermeasures of SEB exposure. 相似文献729.
Background
Processing of multimodal information is a critical capacity of the human brain, with classic studies showing bimodal stimulation either facilitating or interfering in perceptual processing. Comparing activity to congruent and incongruent bimodal stimuli can reveal sensory dominance in particular cognitive tasks. 相似文献730.
The synthesis of NaA-type zeolite from superalkaline reaction mixtures by influence on the formation- and transformation rate of the polymorphous phases according to the Ostwald step rule is discussed. The appearence time of NaA as a single crystallization product is described in dependence on the reaction conditions. The kinetics of the zeolite crystallization and the property alterations of the reaction products in dependence on the time are investigated in the pilot scale. 相似文献