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411.
Helane?MS?Costa Augusto?CV?Freitas Júnior Ian?PG?Amaral Izaura?Y?Hirata Patrícia?MG?Paiva Luiz?B?CarvalhoJr Vitor?Oliveira Ranilson?S?BezerraEmail author 《Chemistry Central journal》2013,7(1):166
Background
Over the past decades, the economic development and world population growth has led to increased for food demand. Increasing the fish production is considered one of the alternatives to meet the increased food demand, but the processing of fish leads to by-products such as skin, bones and viscera, a source of environmental contamination. Fish viscera have been reported as an important source of digestive proteases with interesting characteristics for biotechnological processes. Thus, the aim of this study was to purify and to characterize a trypsin from the processing by-products of crevalle jack (Caranx hippos) fish.Results
A 27.5 kDa trypsin with N-terminal amino acid sequence IVGGFECTPHVFAYQ was easily purified from the pyloric caeca of the crevalle jack. Its physicochemical and kinetic properties were evaluated using N-α-benzoyl-DL-arginine-p-nitroanilide (BApNA) as substrate. In addition, the effects of various metal ions and specific protease inhibitors on trypsin activity were determined. Optimum pH and temperature were 8.0 and 50°C, respectively. After incubation at 50°C for 30 min the enzyme lost only 20% of its activity. K m , kcat, and k cat /K m values using BApNA as substrate were 0.689 mM, 6.9 s-1, and 10 s-1 mM-1, respectively. High inhibition of trypsin activity was observed after incubation with Cd2+, Al3+, Zn2+, Cu2+, Pb2+, and Hg2+ at 1 mM, revealing high sensitivity of the enzyme to metal ions.Conclusions
Extraction of a thermostable trypsin from by-products of the fishery industry confirms the potential of these materials as an alternative source of these biomolecules. Furthermore, the results suggest that this trypsin-like enzyme presents interesting biotechnological properties for industrial applications.412.
Barnabé?Pessoa?Lima Luciano?MariEmail author José?Fabio?Bezerra?MontenegroEmail author Franciane?de?Brito?Vieira 《Mathematische Annalen》2016,366(3-4):1035-1066
Let \(\varphi : M^m \rightarrow N^n\) be a minimal, proper immersion in an ambient space suitably close to a space form \(\mathbb {N}^n_k\) of curvature \(-k\le 0\). In this paper, we are interested in the relation between the density function \(\Theta (r)\) of M and the spectrum of its Laplace–Beltrami operator. In particular, we prove that if \(\Theta (r)\) has subexponential growth (when \(k<0\)) or sub-polynomial growth (\(k=0\)) along a sequence, then the spectrum of \(M^m\) is the same as that of the space form \(\mathbb {N}^m_k\). Notably, the result applies to Anderson’s (smooth) solutions of Plateau’s problem at infinity on the hyperbolic space, independently of their boundary regularity. We also give a simple condition on the second fundamental form that ensures M to have finite density. In particular, we show that minimal submanifolds with finite total curvature in the hyperbolic space also have finite density. 相似文献
413.
414.
Rodrigo?M.?GesterEmail author Herbert?C.?Georg Tertius?L.?Fonseca Patricio?F.?Provasi Sylvio?CanutoEmail author 《Theoretical chemistry accounts》2012,131(5):1220
Electronic polarization induced by the interaction of a reference molecule with a liquid environment is expected to affect
the magnetic shielding constants. Understanding this effect using realistic theoretical models is important for proper use
of nuclear magnetic resonance in molecular characterization. In this work, we consider the pyridine molecule in water as a
model system to briefly investigate this aspect. Thus, Monte Carlo simulations and quantum mechanics calculations based on
the B3LYP/6-311++G (d,p) are used to analyze different aspects of the solvent effects on the 15N magnetic shielding constant of pyridine in water. This includes in special the geometry relaxation and the electronic polarization
of the solute by the solvent. The polarization effect is found to be very important, but, as expected for pyridine, the geometry
relaxation contribution is essentially negligible. Using an average electrostatic model of the solvent, the magnetic shielding
constant is calculated as −58.7 ppm, in good agreement with the experimental value of −56.3 ppm. The explicit inclusion of
hydrogen-bonded water molecules embedded in the electrostatic field of the remaining solvent molecules gives the value of
−61.8 ppm. 相似文献
415.
A historical perspective is given contrasting challenges and advances in theoretical chemistry at the time the first issue
of Theoretical Chemistry Accounts appeared in 1962 and the progress achieved since then as expressed in current state-of-the-art
applications in photochemistry and thermochemistry. 相似文献
416.
Bakardjiev M Štíbr B Holub J Růžička A Padělková Z 《Dalton transactions (Cambridge, England : 2003)》2012,41(23):7151-7155
Reactions between the mesitylene (mes) dication [(η(6)-mes)(2)Fe](2+) (1a) [(PF(6)(-))(2) salt] and lithium o-carboranes Li[1-R-1,2-C(2)B(10)H(11)] (2) (R = H, 2a; Me, 2b; Ph, 2c) at low temperature (-60 °C, 1 h, followed by stirring for 2 h at r.t.) in THF resulted in a clean addition of the corresponding carborane anions to one of the unsubstituted arene sites in 1a, forming a series of orange monocations of general structure [(η(5)-mes-exo-6-{2-R-1,2-C(2)B(10)H(11)})Fe(η(6)-mes)](+) (3) (R = H, 3a; Me, 3b; Ph, 3c) which were isolated as PF(6)(-) salts (3PF(6)) in yields ranging 50-75%. Individual complexes were obtained on purification by LC or preparative TLC on a silica gel substrate, using MeCN-CH(2)Cl(2) mixtures as the mobile phase. Interestingly, the room-temperature reaction between 2a (threefold excess) and 1a(PF(6))(2) with a reverse order of addition of the reaction components yielded an orange salt [(η(5)-mes-exo-6-{1,2-C(2)B(10)H(11)})Fe(η(6)-mes)](+)[closo-nido-H(11)B(10)C(2)-C(2)B(10)H(12)](-) (3acCA) (cCA = conjucto-carborane anion = [closo-nido-H(11)B(10)C(2)-C(2)B(10)H(12)](-)) as a sole product in 71% yield. The formation of this conjucto anion can be taken as a strong support for the participation of a radical-chain mechanism in the ostensible nucleophilic addition which we suppose to be initiated by the formation of the [(mes)(2)Fe(+)]˙ radical cation. The structures of both 3PF(6) and 3acCA have been established by X-ray diffraction and the constitution of all compounds isolated is in agreement with elemental analyses, multinuclear NMR data, and MS spectra. 相似文献
417.
Marcelo?M.?CavalcantiEmail author Valéria?N.?Domingos?Cavalcanti Andrei?Faminskii Fábio?Natali 《Applied Mathematics and Optimization》2012,65(2):221-251
In the present paper we establish results concerning the decay of the energy related to the damped Korteweg–de Vries equation
posed on infinite domains. We prove the exponential decay rates of the energy when a initial value problem and a localized
dissipative mechanism are in place. If this mechanism is effective in the whole line, we get a similar result in H
k
-level, k∈ℕ. In addition, the decay of the energy regarding a initial boundary value problem posed on the right half-line, is obtained
considering convenient a smallness condition on the initial data but a more general dissipative effect. 相似文献
418.
N.?A.?Santos J.?R.?J.?Santos F.?S.?M.?Sinfr?nio T.?C.?Bicudo I.?M.?G.?Santos N.?R.?Antoniosi Filho V.?J.?FernandesJr A.?G.?SouzaEmail author 《Journal of Thermal Analysis and Calorimetry》2009,97(2):611-614
The babassu (Orbignya Phalerata Mart.) biodiesel has lauric esters as main constituents, resulting in high oxidative stability and low cloud and freezing
points. In order to reduce these side effects, the saturated ethyl esters content was reduced by means of winterization process.
The TMDSC and PDSC techniques were used to verify the thermal and oxidative stabilities of the ethyl babassu biodiesel. During
the heating stage, the winterized solid phase of ethyl esters presented an endothermic transition associated to the solidification
process. This behavior was not observed for the liquid winterized FAEE, confirming the efficiency of the winterization process. 相似文献
419.
Michael G. S. Londesborough Jonathan Bould Josef Holub John D. Kennedy Mark Thornton‐Pett Bohumil tíbr 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1423-1424
The title compound, 1,1,2,2‐tetracarbonyl‐1,2‐μ‐carbonyl‐4,11‐dimethylsulfido‐closo‐1,2‐dicobaltadodecaborane, [Co2(C4H20B10S2)(CO)5], has a closo 12‐vertex {1,2‐Co2B10H8} structure with SMe2 ligands at the exo‐4‐ and 11‐positions. The cluster displays close structural similarities to the SEt2 analogue. 相似文献