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841.
Summary Silver and lead, respectively, are determined in a microcalorimeter by measuring the effect of the cation concentration upon an enzyme catalyzed reaction. The reduction in heat of the glucose oxidase catalyzed reaction in presence of Ag+ and Pb2+ is confirmed.
This work was supported by USPHS Grant CA 08023. 相似文献
Zusammenfassung Silber bzw. Blei kann man mit einem Mikrokalorimeter bestimmen, indem die Wirkung der Konzentration des Kations auf eine enzymatische Reaktion gemessen wird. Die Herabsetzung der Wärmetönung der durch Glukoseoxydase katalysierten Reaktion in Gegenwart von Ag+ bzw. Pb2+ wurde bestätigt.
This work was supported by USPHS Grant CA 08023. 相似文献
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Ana Snchez‐Migalln Antonio delaHoz Concepcin Lpez RosaM. Claramunt Lourdes Infantes Sam Motherwell Kenneth Shankland Harriott Nowell Ibon Alkorta Jos Elguero 《Helvetica chimica acta》2003,86(4):1026-1039
The crystal structure of 1‐hydroxy‐2,4,5‐triphenyl‐1H‐imidazole 3‐oxide ( 1 ) has been determined from laboratory X‐ray powder‐diffraction data. The two independent molecules in the asymmetric unit form chains via O? H???O hydrogen bonds related by a twofold screw axis. One of the O???O distances is extremely short (2.32(1) and 2.43(1) Å). Solid‐state NMR spectroscopy (CPMAS) combined with calculation of absolute shieldings (GIAO/B3LYP/6‐31G*) allowed us to determine that the compound behaves as if the O? H???O hydrogen bond has the proton in the middle (single‐well potential), resulting in the near identity of both 15N‐NMR signals. 相似文献
844.
Groenhof G Bouxin-Cademartory M Hess B De Visser SP Berendsen HJ Olivucci M Mark AE Robb MA 《Journal of the American Chemical Society》2004,126(13):4228-4233
Atomistic QM/MM simulations have been carried out on the complete photocycle of Photoactive Yellow Protein, a bacterial photoreceptor, in which blue light triggers isomerization of a covalently bound chromophore. The "chemical role" of the protein cavity in the control of the photoisomerization step has been elucidated. Isomerization is facilitated due to preferential electrostatic stabilization of the chromophore's excited state by the guanidium group of Arg52, located just above the negatively charged chromophore ring. In vacuo isomerization does not occur. Isomerization of the double bond is enhanced relative to isomerization of a single bond due to the steric interactions between the phenyl ring of the chromophore and the side chains of Arg52 and Phe62. In the isomerized configuration (ground-state cis), a proton transfer from Glu46 to the chromophore is far more probable than in the initial configuration (ground-state trans). It is this proton transfer that initiates the conformational changes within the protein, which are believed to lead to signaling. 相似文献
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This paper presents a simple algorithm for quality triangulation in domains with complex geometries. Based on the fact that the equilateral triangles (regular meshes) are ideal for numerical computations in computational fluids dynamics (CFD) analysis, the proposed algorithm starts with an initial equilateral triangle mesh covering the whole domain. Nodes close to the boundary edges satisfy the so‐called non‐encroaching criterion, the distance from any inserted node to any boundary vertices and the midpoints of any boundary edge is greater than a given characteristic length. Both nearly uniform and non‐uniform triangle meshes can be generated using a mesh size reduction technique. Local refinement is achieved by using transition layers. More regular meshes can be generated in the interior of the domain and all angles of the triangle mesh produced by this algorithm are proven to be bounded in a reasonable range (19.5–141°). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
848.
In geometrically complex domains, the Ryskin and Leal (RL) orthogonal mesh generation system may cause mesh distortion and overlapping problems when using the ‘weak constraint’ method with specified boundary point distribution for all boundaries. To resolve these problems, an improved RL system with automatic smoothness control is proposed. In this improved RL system, the automatic smoothness control mechanism is based on five types of smoothness conditions and includes the self‐adjustment mechanism and the auto‐evaluation mechanism for an empirical parameter. The proposed system is illustrated using several test examples. Several applications to natural domains are also demonstrated. It is shown that the improved RL system is capable of resolving the above problems at little cost of orthogonality. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
849.
Burcu Binici Dionne I. Fortenberry Kayce C. Leard Marcus Molden Nesrin Olten Sam Popwell John A. Pojman 《Journal of polymer science. Part A, Polymer chemistry》2006,44(4):1387-1395
We demonstrate for the first time spherically propagating frontal polymerization that also exhibits spin modes. We have developed an interesting system using the amine‐catalyzed Michael addition of a trithiol to a triacrylate to create a rubbery gel. The gel suppresses convection and bubble formation during front propagation. A peroxide is also present to act as a thermal initiator. The front propagates via free‐radical polymerization of the remaining triacrylate after being initiated photochemically in the center of the reactor. It is possible to prepare the rubbery gel in any shape and then initiate thermal frontal polymerization. So‐called spin modes have been observed for the first time in spherically propagating fronts in which waves of polymerization propagate on the expanding spherical front. A system using a diacrylate dissolved in dimethyl sulfoxide with added silica gel and with persulfate as the initiator supports spherical fronts but does not exhibit spin modes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1387–1395, 2006 相似文献
850.