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1.
A preparative-scale electrophoretic technique for protein fractionation and elution on a discontinuous gradient of acrylamide is described, which permits the separation and elution of a pure protein from a mixture containing 4-20 electrophoretically different proteins. The sharpness of the gradient electrophoretic resolution is demonstrated by the separation of proteins consisting of bovine serum albumin polymers and lactate dehydrogenase and enzymes such as acid phosphatase. The compositions of various discontinuous gradients of acrylamide and their application to enzyme purification are discussed. It was found that 60% of the enzyme activity loaded on the gel is recovered after gel fractionation and elution. 相似文献
2.
The saponification of ethyl acetate was measured by conductimetry at different temperatures within a batch reactor. A new mathematical model for obtaining concentration profiles from conductivity was presented and used for reaction‐kinetics' determination. The Arrhenius parameters (A, Ea) showed good agreement with the previously published values. Basic transition‐state theory was used for obtaining the Gibbs energy (ΔG?), the enthalpy (ΔH?), and the entropy (ΔS?) of activation. The low enthalpy of activation and negative entropy of activation were consistent with a reaction pathway when forming a transition‐state complex. The suggested mechanism involves OH?, acting as a general base for removing proton from one of the hydroxide hydrating water, placed directly between it and the ester. The nucleophile from the water then attacks at the electrophilic C of the ester, breaking the π bond, and creating a tetrahedral intermediate. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 692–698, 2012 This article was published online on 24 January 2012. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected on 16 July 2012. 相似文献
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Pure states in quantum field theory can be represented by many-fingered block-time wave functions, which treat time on an equal footing with space and make the notions of “time evolution” and “state at a given time” fundamentally irrelevant. Instead of information destruction resulting from an attempt to use a “state at a given time” to describe semi-classical black-hole evaporation, the full many-fingered block-time wave function of the universe conserves information by describing the correlations of outgoing Hawking particles in the future with ingoing Hawking particles in the past. 相似文献
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We present the first experimental observation of modulation instability and spontaneous pattern formation with incoherent white light emitted from an incandescent light bulb. We show experimentally that modulation instability of white light propagating in a noninstantaneous self-focusing medium is a collective effect, where the entire temporal spectrum of the light beam becomes unstable at the same threshold value and collectively forms a pattern with a single periodicity. We experimentally demonstrate that the temporal spectrum of the evolving perturbation self-adjusts to match the collective pattern formation phenomenon. 相似文献
7.
Hrvoje Šikić 《Journal of Theoretical Probability》2000,13(2):571-574
We prove that for a>0, (B
t) one-dimensional standard Brownian motion and
0=inf{t>0 : B
t=0} the following zero–one law is valid
相似文献
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Hasan Karabıyık Hande Petek Nazan Ocak İskeleli Çiğdem Albayrak Erbil Ağar 《Journal of chemical crystallography》2011,41(11):1642-1648
Abstract
Some molecules having a molecular skeleton similar to that of stilbenes and azobenzenes show orientational disorder in the crystals due to pedal motion. Heretofore, the orientational disorder through pedal motion has been observed for the compounds containing only two aromatic rings in the absence of bulky substituent groups. Here we report that the pedal motion can be detected even in the presence of a bulky substituent group to which orientational disorder becomes invisible as a result of anchor effect arising from phenoxyphtalonitrile group. X-ray crystallographic analysis of the compound, C23H18N4O, reveals the existence of partially overlapped two pedal conformers. The compound crystallizes in the monoclinic space group P21/c with a = 12.9429(11) Å, b = 8.5075(5) Å, c = 21.063(2) Å and β = 123.155(6)°. Major pedal conformer is stabilized by weak C–H···O type hydrogen bond and C–H···π type edge-to-face interactions in solid state. Quantum chemical calculations at B3LYP/6-311G+(d,p) level suggest that the stabilization of the compound decreases with increasing deviation from the planar geometry of trans-azobenzene fragment. 相似文献10.
Construction of a New Class of Tetracycline Lead Structures with Potent Antibacterial Activity through Biosynthetic Engineering
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Dr. Urška Lešnik Dr. Tadeja Lukežič Dr. Ajda Podgoršek Dr. Jaka Horvat Dr. Tomaž Polak Dr. Martin Šala Branko Jenko Dr. Kirsten Harmrolfs Dr. Alain Ocampo‐Sosa Prof. Dr. Luis Martínez‐Martínez Dr. Paul R. Herron Dr. Štefan Fujs Dr. Gregor Kosec Prof. Dr. Iain S. Hunter Prof. Dr. Rolf Müller Prof. Dr. Hrvoje Petković 《Angewandte Chemie (International ed. in English)》2015,54(13):3937-3940
Antimicrobial resistance and the shortage of novel antibiotics have led to an urgent need for new antibacterial drug leads. Several existing natural product scaffolds (including chelocardins) have not been developed because their suboptimal pharmacological properties could not be addressed at the time. It is demonstrated here that reviving such compounds through the application of biosynthetic engineering can deliver novel drug candidates. Through a rational approach, the carboxamido moiety of tetracyclines (an important structural feature for their bioactivity) was introduced into the chelocardins, which are atypical tetracyclines with an unknown mode of action. A broad‐spectrum antibiotic lead was generated with significantly improved activity, including against all Gram‐negative pathogens of the ESKAPE panel. Since the lead structure is also amenable to further chemical modification, it is a platform for further development through medicinal chemistry and genetic engineering. 相似文献