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31.
For chemistry the theoretical representation of the forces connecting atoms in molecules was and is a central problem. The Atomic Orbital and the Molecular Orbital are basic building blocks in the Heitler–London (HL) and in the Linear Combination of Atomic Orbitals–Molecular Orbital (LCAO-MO) methods, which have lead to the construction of modern Valence Bond and Hartree–Fock methods (and related extensions). However, accurate predictions from non semi-empirical methods often require enormous amount of computer power, if applied to molecules of reasonable size and current chemical interest. We have critically re-examined the two basic methods and suggested a few extensions. Merging of the Hartree–Fock with the Heitler–London algorithms, as recently proposed in the Hartree–Fock–Heitler–London (HF–HL) method, reduces the length of the expansions needed in AO or MO ab initio models in the computation of binding energy; this simplification allows easy interpretation of the resulting wave function. The HF–HL method is exemplified with systematic computations on ground and excited state of the hydrides and homonuclear diatomic molecules with atoms of the first and second period of the periodic table. Further, we show that the HF–HL method is derivable from a wave function constructed with a new type of orbital, the Chemical orbital (CO), which embodies the characterization of MO near equilibrium, AO at dissociation and at the united atom. Preliminary computations with CO are included. The new method provides the conceptual origin of both the HF and VB approaches, thus the foundation of an 80 years effort in variational quantum chemistry. 相似文献
32.
Yoshihiko Katayama Dr. Ondrej Burkacky Dr. Martin Meyer Dr. Christoph Bräuchle Prof. Enrico Gratton Prof. Don C. Lamb Prof. 《Chemphyschem》2009,10(14):2458-2464
We developed a new method for real‐time, three‐dimensional tracking of fluorescent particles. The instrument is based on a laser‐scanning confocal microscope where the focus of the laser beam is scanned or orbited around the particle. Two confocal pinholes are used to simultaneously monitor regions immediately above and below the particle and a feedback loop is used to keep the orbit centered on the particle. For moderate count rates, this system can track particles with 15 nm spatial resolution in the lateral dimensions and 50 nm in the axial dimension at a temporal resolution of 32 ms. To investigate the interaction of the tracked particles with cellular components, we have combined our orbital tracking microscope with a dual‐color, wide‐field setup. Dual‐color fluorescence wide‐field images are recorded simultaneously in the same image plane as the particle being tracked. The functionality of the system was demonstrated by tracking fluorescent‐labeled artificial viruses in tubulin‐eGFP expressing HUH7 cells. The resulting trajectories can be used to investigate the microtubule network with super resolution. 相似文献
33.
Roberta Ragni Enrico Orselli Gregg S. Kottas Omar Hassan Omar Francesco Babudri Adriana Pedone Francesco Naso Gianluca M. Farinola Prof. Dr. Luisa De Cola Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(1):136-148
The synthesis and photophysical and electrochemical characterisation of new heteroleptic iridium complexes with electron‐withdrawing sulfonyl groups and fluorine atoms bound to phenylpyridine ligands are reported. The emission energy of these materials strongly depends on the position of the sulfonyl groups and on the number of fluorine substituents. A 90 nm wide tuning range of photoluminescence from the blue‐green (λem=468 nm) of iridium(III)bis[2‐(4′‐benzylsulfonyl)phenylpyridinato‐N,C2′][3‐(pentafluorophenyl)‐pyridin‐2‐yl‐1,2,4‐triazolate] to the orange (λem=558 nm) of iridium(III)bis[2‐(3′‐benzylsulfonyl)phenylpyridinato‐N,C2′](2,4‐decanedionate) has been achieved. Emission quantum yields ranging from 47 to 71 % have also been found for degassed solutions of the complexes, and a surprisingly high value of 16 % was recorded for iridium(III)bis[2‐(5′‐benzylsulfonyl‐3′,6′‐difluoro)phenylpyridinato‐N,C2′](2,4‐decanedionate) in air‐equilibrated dichloromethane. A unusual stereochemistry of the benzylsulfonyl‐substituted dimer and heteroleptic complexes has been detected by 1H NMR spectroscopy, and is characterised by the mutual cis disposition of the pyridyl nitrogen atoms of the phenylpyridine ligands, which differs from the most common trans arrangement reported in the literature. 相似文献
34.
Loss aversion with multiple investment goals 总被引:1,自引:0,他引:1
Enrico G. De Giorgi 《Mathematics and Financial Economics》2011,5(3):203-227
This paper presents a time-continuous portfolio selection model with loss averse investors, who possess multiple investment
goals at different time horizons. The model assumes partial narrow framing. Investors follow a two-step approach. First, they
optimally allocate wealth among investment goals. Second, they determine an optimal investment strategy for each investment
goal separately. We show that when loss aversion is according to the experimental findings, investors mainly invest their
wealth to reach long-term goals and adopt investment strategies with high leverage to reach short-term goals. The overall
strategy also display high leverage. The same patterns is observed when loss aversion is extreme and goals are very ambitious.
By contrast, when loss aversion is extreme but goals are not too ambitious, investors mainly invest to reach short-term goals
and adopt safe investment strategies for this purpose. 相似文献
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38.
Patricia Gimenez Heleno Bolfarine Enrico A. Colosimo 《Annals of the Institute of Statistical Mathematics》2000,52(4):698-711
In this paper, hypotheses testing based on a corrected score function are considered. Five different testing statistics are proposed and their asymptotic distributions are investigated. It is shown that the statistics are asymptotically distributed according to the chisquare distribution or can be written as a linear combination of chisquare random variables with one degree of freedom. A small scale numerical Monte Carlo study is presented in order to compare the empirical size and power of the proposed tests. A comparative calibration example is used to illustrate the results obtained. 相似文献
39.
Franco Varsano Francesca Decker Enrico Masetti 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):83-95
Summary. Ce-V mixed oxide films have been deposited by RF sputtering with the aim of increasing the Li charge capacity of counter
electrodes in smart windows. Such mixed oxides have shown high transmittance and optical passivity in the visible region.
After electrode pre-conditioning by cyclic voltammetry, a good electrochemical reversibility in LiClO4– propylene carbonate electrolyte was observed, and large Li-charge capacity under galvanostatic charging (up to 50 mCċcm−2) has been measured. The electrode charge capacity decreased after prolonged insertion-deinsertion cycles, whereas the photoptic
transmittance remained about constant. After 800 cycles the Li-charge capacity decreased to 40 mCċcm−2. The Li diffusion coefficient inside the films measured by electrochemical impedance and by galvanostatic titration ranged
from 10−11 cm2ċs−1 to 10−13cm2ċs−1. We observed that the Li charge capacity of the film electrodes is a function of the film deposition conditions, because
it increased with the vanadium oxide concentration in the target and with the oxygen content in the sputtering atmosphere.
Received June 23, 2000. Accepted (revised) August 7, 2000 相似文献
40.