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991.
Dr. Jared B. DeCoste Dr. Mitchell H. Weston Patrick E. Fuller Trenton M. Tovar Gregory W. Peterson Dr. M. Douglas LeVan Dr. Omar K. Farha 《Angewandte Chemie (International ed. in English)》2014,53(51):14092-14095
We present a systematic study of metal–organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10 000 MOFs for the adsorption of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST‐1 (Cu‐BTC) and NU‐125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST‐1 and NU‐125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU‐125 has an increased excess capacity for oxygen of 237 % and 98 %, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications. 相似文献
992.
Rutledge LR Navarro-Whyte L Peterson TL Wetmore SD 《The journal of physical chemistry. A》2011,115(45):12646-12658
The MP2/6-31G*(0.25) π-π or π(+)-π T-shaped (edge-to-face) interactions between neutral or protonated histidine and adenine were considered using computational models of varying size to determine the effects of the protein and DNA backbones on the preferred dimer structure and binding strength. The overall consequences of the backbones are reasonably subtle for the neutral adenine-histidine T-shaped dimers. Furthermore, the minor changes in the binding strengths of these dimers upon model extension arise from additional (attractive) backbone-π (bb-π) contacts and changes in the preferred π-π orientations, which is verified by the quantum theory of atoms in molecules (QTAIM). Since the binding strength of the extended dimer equals the sum of the individual backbone-π and π-π contributions, the π-π component is not appreciably affected by polarization of the ring upon inclusion of the biological backbone. In contrast, the larger effect of the backbone on the protonated histidine dimers cannot simply be predicted as the sum of changes in the π-π and bb-π components regardless of the dimer type or model. This suggests, and QTAIM qualitatively supports, that the magnitude of the π(+)-π contribution changes, which is likely due to alterations in the electrostatic landscape of the monomer rings upon inclusion of the biological backbone that largely affect T-shaped dimers. These findings differ from those previously reported for (neutral) π-π stacked and (metallic) cation-π interactions, which highlights the distinct properties of each (π-π, π(+)-π, and cation-π) classification of noncovalent interaction. Furthermore, these results emphasize the importance of considering backbone-π interactions when analyzing contacts that appear in experimental crystal structures and cautions the use of truncated models when evaluating the magnitude of the π(+)-π contribution present in large biological complexes. 相似文献
993.
994.
Bushuyev OS Brown P Maiti A Gee RH Peterson GR Weeks BL Hope-Weeks LJ 《Journal of the American Chemical Society》2012,134(3):1422-1425
Energetic materials have been used for nearly two centuries in military affairs and to cut labor costs and expedite laborious processes in mining, tunneling, construction, demolition, and agriculture, making a tremendous contribution to the world economy. Yet there has been little advancement in the development of altogether new energetic motifs despite long-standing research efforts to develop superior materials. We report the discovery of new energetic compounds of exceptionally high energy content and novel polymeric structure which avoid the use of lead and mercury salts common in conventional primary explosives. Laboratory tests indicate the remarkable performance of these Ni- and Co-based energetic materials, while DFT calculations indicate that these are possibly the most powerful metal-based energetic materials known to date, with heats of detonation comparable with those of the most powerful organic-based high explosives currently in use. 相似文献
995.
Consider the Emden-Fowler dynamic equation $$ x^{\Delta\Delta}(t)+p(t)x^\alpha(t)=0,\:\:\alpha >0 , \qquad \qquad \qquad \qquad (0.1) $$ where ${p\in C_{rd}([t_0,\infty)_{\mathbb{T}},\mathbb{R}), \alpha}$ is the quotient of odd positive integers, and ${\mathbb{T}}$ denotes a time scale which is unbounded above and satisfies an additional condition (C) given below. We prove that if ${\int^\infty_{t_0}t^\alpha |p(t)|\Delta t<\infty}$ (and when ???=?1 we also assume lim t???? tp(t)??(t)?=?0), then (0.1) has a solution x(t) with the property that $$ \lim_{t\rightarrow\infty} \frac{x(t)}{t}=A\neq 0.$$ 相似文献
996.
The pulse shape of a passively Q-switched microchip laser 总被引:2,自引:0,他引:2
T. Erneux P. Peterson A. Gavrielides 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):423-431
The shape of the intensity pulse of a passively Q-switched microchip laser is investigated numerically and analytically. Our
analysis is motivated by independent microchip laser experiments exhibiting nearly symmetric pulses in the case of a semiconductor
saturable absorber and asymmetric pulses in the case of a solid state saturable absorber. Asymptotic methods are used to determine
limiting behaviors of the pulse shape for both symmetric and asymmetric pulses. In the first case, we determine a sech2 solution parametrized by one parameter which can be determined by solving two coupled nonlinear algebraic equations. In the
second case, the pulse solution is decomposed into two distinct approximations exhibiting different amplitude and time scales
properties. We review earlier approximations of the repetition rate and the pulse width.
Received 2 August 1999 相似文献
997.
998.
Generalized variational inequalities 总被引:5,自引:0,他引:5
This paper introduces and analyzes generalized variational inequalities. The most general existence theory is established, traditional coercivity conditions are extended, properties of solution sets under various monotonicity conditions are investigated, and a computational scheme is considered. Similar results can be obtained for generalized complementarity and fixed-point problems.The authors are indebted to Professor R. Saigal of Northwestern University for his continuous encouragement and helpful discussions concerning this paper. 相似文献
999.
Coan TE Gao YS Liu F Artuso M Boulahouache C Blusk S Butt J Dambasuren E Dorjkhaidav O Li J Menaa N Mountain R Nandakumar R Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Csorna SE Bonvicini G Cinabro D Dubrovin M Briere RA Chen GP Chen J Ferguson T Tatishvili G Vogel H Watkins ME Rosner JL Adam NE Alexander JP Berkelman K Cassel DG Crede V Duboscq JE Ecklund KM Ehrlich R Fields L Gibbons L Gittelman B Gray R Gray SW Hartill DL Heltsley BK Hertz D Hsu L Jones CD Kandaswamy J Kreinick DL 《Physical review letters》2005,95(18):181802
With the first data sample collected by the CLEO-c detector at the psi(3770) resonance we have studied four exclusive semileptonic decays of the D0 meson. Our results include the first observation and absolute branching fraction measurement for D0 --> p-e+ve and improved measurements of the absolute branching fractions for D0 decays to K-e+ve, pi-e+ve, and K*-e+ve. 相似文献
1000.
The accuracy of employing effective core polarization potentials (CPPs) to account for the effects of core-valence correlation
on the spectroscopic constants and dissociation energies of the molecules B2, C2, N2, O2, F2, CO, CN, CH, HF, and C2H2 has been investigated by comparison to accurate all-electron benchmark calculations. The results obtained from the calculations
employing CPPs were surprisingly accurate in every case studied, reducing the errors in the calculated valence D
e values from a maximum of nearly 2.5 kcal/mol to just 0.3 kcal/mol. The effects of enlarging the basis set and using higher-order
valence electron correlation treatments were found to have only a small influence on the core-valence correlation effect predicted
by the CPPs. Thus, to accurately recover the effects of intershell correlation, effective core polarization potentials such
as the ones used in the present work provide an attractive alternative to carrying out computationally demanding calculations
where the core electrons are explicitly included in the correlation treatment.
Received: 11 May 1998 / Accepted: 27 July 1998 / Published online: 28 October 1998 相似文献