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排序方式: 共有335条查询结果,搜索用时 15 毫秒
71.
Summary: Gelatin is widely used in capsules manufacturing. Most of the capsules in pharmaceutical applications are hard capsules made out of concentrated solutions of gelatin, where water has been progressively removed during the drying process. More recently soft capsules found an increasing interest in pharmaceutical and cosmetic applications where they are filled and sealed with a liquid substance. In order to keep the shells of capsules flexible after drying at room temperature, plasticizer is added to the gelatin aqueous solutions. We present in this paper a systematic investigation of gelatin films, equilibrated under a range of relative humidity (RH). The films contain glycerol as plasticizer P or only water and gelatin, (G). In order to analyze the role of the plasticizer, we fixed various P/G ratios and measured the water retention versus RH. Films were characterized by DSC (Mettler Toledo DSC823). Glass transition temperature Tg, melting temperature Tm and enthalpy associated with helix-coil transition were determined. The role of water and glycerol was examined in relation with the large variations of these transition temperatures with film composition. Non equilibrium effects are also discussed, in particular concerning the glass transition temperature, the relaxation effects and the water repartition between amorphous coils and helical structure. In conclusion, we propose a unique phase diagram of the gelatin films with any proportion of water and glycerol. 相似文献
72.
Al–1 wt% Ti alloy was directionally solidified upwards under argon atmosphere under the two conditions; with different temperature gradients (G = 2.20–5.82 K/mm) at a constant growth rate (V = 8.30 μm/s) and with different growth rates (V = 8.30–498.60 μm/s) at a constant temperature gradient (G = 5.82 K/mm) in a Bridgman furnace. The dependence of characteristic microstructure parameters such as primary dendrite arm spacing (λ1), secondary dendrite arm spacing (λ2), dendrite tip radius (R) and mushy zone depth (d) on the velocity of crystal growth and the temperature gradient were determined by using a linear regression analysis. A detailed analysis of microstructure development with models of dendritic solidification and with previous similar experimental works on dendritic growth for binary alloys were also made. 相似文献
73.
Werwie M Xu X Haase M Basché T Paulsen H 《Langmuir : the ACS journal of surfaces and colloids》2012,28(13):5810-5818
Light-harvesting complex (LHCII) of the photosynthetic apparatus in plants is attached to type-II core-shell CdTe/CdSe/ZnS nanocrystals (quantum dots, QD) exhibiting an absorption band at 710 nm and carrying a dihydrolipoic acid coating for water solubility. LHCII stays functional upon binding to the QD surface and enhances the light utilization of the QDs significantly, similar to its light-harvesting function in photosynthesis. Electronic excitation energy transfer of about 50% efficiency is shown by donor (LHCII) fluorescence quenching as well as sensitized acceptor (QD) emission and corroborated by time-resolved fluorescence measurements. The energy transfer efficiency is commensurable with the expected efficiency calculated according to F?rster theory on the basis of the estimated donor-acceptor separation. Light harvesting is particularly efficient in the red spectral domain where QD absorption is relatively low. Excitation over the entire visible spectrum is further improved by complementing the biological pigments in LHCII with a dye attached to the apoprotein; the dye has been chosen to absorb in the "green gap" of the LHCII absorption spectrum and transfers its excitation energy ultimately to QD. This is the first report of a biological light-harvesting complex serving an inorganic semiconductor nanocrystal. Due to the charge separation between the core and the shell in type-II QDs the presented LHCII-QD hybrid complexes are potentially interesting for sensitized charge-transfer and photovoltaic applications. 相似文献
74.
Tariq M Freire MG Saramago B Coutinho JA Lopes JN Rebelo LP 《Chemical Society reviews》2012,41(2):829-868
Some of the most active scientific research fronts of the past decade are centered on ionic liquids. These fluids present characteristic surface behavior and distinctive trends of their surface tension versus temperature. One way to explore and understand their unique nature is to study their surface properties. This critical review analyses most of the surface tension data reported between 2001 and 2010 (187 references). 相似文献
75.
Fiametti KG Ustra MK de Oliveira D Corazza ML Furigo A Vladimir Oliveira J 《Ultrasonics sonochemistry》2012,19(3):440-451
This work reports experimental kinetic data of solvent-free glycerolysis of olive oil using a commercial immobilized lipase (Novozym 435) under the influence of ultrasound irradiation. The experiments were performed in a mechanically stirred reactor under ultrasound irradiation, evaluating the effects of temperature (50-70 °C), enzyme concentration (2.5-10 wt%) and glycerol to oil molar ratio (0.8:1-3:1). Results show that ultrasound-assisted lipase-catalyzed glycerolysis might be a potential alternative route to conventional methods, as high contents of reaction products, especially monoglycerides, were achieved at mild irradiation power supply (∼130 W) and temperature, in a relatively short reaction time (2 h) and low enzyme content (7.5 wt%). To completeness, two simplified kinetic modeling approaches, based on the ordered-sequential bi bi mechanism and reaction stoichiometry, were employed to represent the experimental data, thus allowing a better understanding of the reaction kinetics. 相似文献
76.
Mara Mirasoli Angela Buragina Luisa Stella Dolci Massimo Guardigli Patrizia Simoni Angel Montoya Elisabetta Maiolini Stefano Girotti Aldo Roda 《Analytica chimica acta》2012
Simple, rapid and highly sensitive assays, possibly allowing on-site analysis, are required in the security and forensic fields or to obtain early signs of environmental pollution. Several bioanalytical methods and biosensors based on portable devices have been developed for this purpose. Among them, Lateral Flow ImmunoAssays (LFIAs) offer the advantages of rapidity and ease of use and, thanks to the high specificity of antigen–antibody binding, allow greatly simplifying and reducing sample pre-analytical treatments. However, LFIAs usually employ colloidal gold or latex beads as labels and they rely on the formation of colored bands visible by the naked eye. With this assay format, only qualitative or semi-quantitative information can be obtained and low sensitivity is achieved. Recently, the use of enzyme-catalyzed chemiluminescence detection in LFIA has been proposed to overcome these problems. In this work, we describe the development of a quantitative CL-LFIA assay for the detection of 2,4,6-trinitrotoluene (TNT) in real samples. Thanks to the use of a portable imaging device for CL signal measurement based on a thermoelectrically cooled CCD camera, the analysis could be performed directly on-field. A limit of detection of 0.2 μg mL−1 TNT was obtained, which is five times lower than that obtained with a previously described colloidal gold-based LFIA developed employing the same immunoreagents. The dynamic range of the assay extended up to 5 μg mL−1 TNT and recoveries ranging from 97% to 111% were obtained in the analysis of real samples (post blast residues obtained from controlled explosion). 相似文献
77.
Several optical arrangements using non-uniformly polarized fields are proposed for generating beams with spin and/or orbital angular momentum. By choosing adequately the input beam polarization and the characteristics of the different proposed set-ups we can control the overall angular momentum of the output beam at will. The orbital angular momentum is analyzed with the beam moments theory and the spin term is evaluated using the averaged s3 Stokes parameter. 相似文献
78.
Mara D. Neusel 《Mathematische Zeitschrift》2000,235(2):353-378
Let H be an unstable algebra over the Steenrod algebra, and let be a multiplicatively closed subset. inherits an action of the Steenrod algebra from H, which is, however, in general no longer unstable. In this note we consider the following three statements.
(1)] H is Noetherian,
(2) the integral closure, , of H in the localization with respect to S is Noetherian,
(3) , where denotes the unstable part.
If the set S contains only (nonzero) nonzero divisors and the algebras are reduced then
If S contains zerodivisors, then only remains true, to show the converse is false we construct a counterexample. The implication is always true, while needs a bunch of technical assumptions to remain true. However, none of them can be removed: we illustrate this also with
examples. Finally, as a technical tool, we characterize -finite algebras.
Received February 8, 1999 / in final form August 16, 1999 / Published online July 20, 2000 相似文献
79.
80.
Mara Beller 《Foundations of Physics》1996,26(4):545-557
The aim of this paper is to combine the intellectual and the psychosocial aspects. blurring the distinction between the conceptual and the anecdotal history of quantum mechanics. The full realization of the importance of such anecdotal factors leads to the revision of our understanding of the conceptual development itself. The paper concludes with the suggestion that a major part of numerous inconsistencies in the Copenhagen interpretation of quantum physics are of a psychosocial origin. 相似文献