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91.
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93.
摘要本文用Feynmann路径积分方法,研究了一种U(1)规范场理论中的Casimir效应。在一圈图近似下,计算了带电标量场在两个平行的理想金属板之间的Casimir能,并对低维情况进行了讨论。 相似文献
94.
Evaluating the accuracy of theoretical one‐bond 13C─13C scalar couplings and their ability to predict structure in a natural product
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Jacob Powell Domenic Valenti Harley Bobnar Erika Drain Blaine Elliott Sydney Frank Tyler McCullough Sean Moore Andrew Kettring Robbie Iuliucci James K. Harper 《Magnetic resonance in chemistry : MRC》2017,55(11):979-989
This study explores the feasibility of using a combination of experimental and theoretical 1‐bond 13C─13C scalar couplings (1JCC) to establish structure in organic compounds, including unknowns. Historically, nJCC and nJCH studies have emphasized 2 and 3‐bond couplings, yet 1JCC couplings exhibit significantly larger variations. Moreover, recent improvements in experimental measurement and data processing methods have made 1JCC data more available. Herein, an approach is evaluated in which a collection of theoretical structures is created from a partial nuclear magnetic resonance structural characterization. Computed 1JCC values are compared to experimental data to identify candidates giving the best agreement. This process requires knowledge of the error in theoretical methods, thus the B3LYP, B3PW91, and PBE0 functionals are evaluated by comparing to 27 experimental values from INADEQUATE. Respective errors of ±1.2, ±3.8, and ±2.3 Hz are observed. An initial test of this methodology involves the natural product 5‐methylmellein. In this case, only a single candidate matches experimental data with high statistical confidence. This analysis establishes the intramolecular hydrogen‐bonding arrangement, ring heteroatom identity, and conformation at one position. This approach is then extended to hydroheptelidic acid, a natural product not fully characterized in prior studies. The experimental/theoretical approach proposed herein identifies a single best‐fit structure from among 26 candidates and establishes, for the first time, 1 configuration and 3 conformations to complete the characterization. These results suggest that accurate and complete structural characterizations of many moderately sized organic structures (<800 Da) may be possible using only 1JCC data. 相似文献
95.
N. Thilagavathi A. Manimaran N. Padma Priya N. Sathya C. Jayabalakrishnan 《应用有机金属化学》2010,24(4):301-307
Four tridentate O, N, O donor Schiff base ligands were prepared by the reaction of substituted benzhydrazide and appropriate salicylaldehyde. The complexes of these ligands were synthesized by refluxing the ligands with ruthenium(II) starting complexes of the formula [RuHCl(CO)(EPh3)2B] in benzene, where E = P or As; B = PPh3 or AsPh3 or pyridine. The newly synthesized complexes were characterized by elemental, spectral (FT‐IR, UV and NMR) and electrochemical data. On the basis of the above studies, an octahedral structure has been proposed for all the complexes. The catalytic efficiency of the complexes in aryl–aryl couplings and oxidation of alcohols was examined and their inhibition activity against the growth of the micro‐organisms was also examined. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
96.
Monoalkylated acylguanidines are important functional groups in many biologically active compounds and additionally applied in coordination chemistry. Yet a straightforward assignment of the individual NH chemical shifts and the acylguanidine conformations is still missing. Therefore, in this study, NMR spectroscopic approaches for the chemical and especially the conformational assignment of protonated monoalkylated acylguanidines are presented. While NOESY and 3JH, H scalar couplings cannot be applied successfully for the assignment of acylguanidines, 4JH, H scalar couplings in 1H,1H COSY spectra allow for an unambiguous chemical shift and conformational assignment. It is shown that these 4JH, H long‐range couplings between individual acylguanidinium NH resonances are observed solely across all‐trans (w) pathways. Already one cis orientation in the magnetisation transfer pathway leads to signal intensities below the actual detection limit and significantly lower than cross‐peaks from 2JNH, NH couplings or chemical exchange. However, it should be noted that also in the case of conformational exchange being fast on the NMR time scale, averaged cross‐peaks from all‐trans 4JH, H scalar couplings are detected, which may lead at first glance to an incomplete or even wrong conformational analysis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
97.
S. F. King 《Pramana》2004,62(2):307-318
We review experimental and theoretical developments in inflation and its application to structure formation, including the
curvaton idea. We then discuss a particle physics model of supersymmetric hybrid inflation at the intermediate scale in which
the Higgs scalar field is responsible for large scale structure, show how such a theory is completely natural in the framework
extra dimensions with an intermediate string scale. 相似文献
98.
M. E. Fels 《Transactions of the American Mathematical Society》1996,348(12):5007-5029
A simple invariant characterization of the scalar fourth-order ordinary differential equations which admit a variational multiplier is given. The necessary and sufficient conditions for the existence of a multiplier are expressed in terms of the vanishing of two relative invariants which can be associated with any fourth-order equation through the application of Cartan's equivalence method. The solution to the inverse problem for fourth-order scalar equations provides the solution to an equivalence problem for second-order Lagrangians, as well as the precise relationship between the symmetry algebra of a variational equation and the divergence symmetry algebra of the associated Lagrangian.
99.
We propose a behavioral modeling that takes into account the thermomechanical couplings accompanying the phase transition in single-crystal CuZnAl samples. The goal of this model is to put forward the significant role played by the heat diffusion in the propagation mode of the phase change fronts. Numerical simulations showed the existence of such a phase change front and predicted the calorimetric and kinematic effects accompanying its propagation. In particular, an inversion of the propagation way during a creep test and caused by an increase of the room temperature was correctly simulated by the model. To cite this article: A. Chrysochoos et al., C. R. Mecanique 331 (2003). 相似文献
100.
Philippe Delanoe 《Annals of Global Analysis and Geometry》1992,10(1):3-61
Existence, uniqueness and weighted regularity of solutions of linear and nonlinear second-order uniformly elliptic differential equations on complete punctured compact N-manifolds, N > 2. Application to prescribed curvature problems: scalar curvature in a quasi-isometry class (including a contribution to the Lichnérowicz-York equation of General Relativity); Ricci curvature in a weighted Kähler class (with a related result in equiaffine geometry). A new asymptonic behaviour is allowed throughout, called partial decay, which requires its own maximum principle.Current support: CNRS; partial support; CEE contract GADGET # SC1-0105-C. 相似文献