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31.
32.
Studies on nitrogen iodine compounds. VII. The IR spectrum of nitrogen triiodide-1 ammonia in the range of N—I fundamental vibrations and the valence force constants of the N—I bonds New infrared spectra in the region 33—600 cm?1 of 14NI3 · 14NH3, 15NI3 · 15NH3 and 14NI3 · pyridine, respectively, have been obtained. In addition, the infrared spectrum of 14NI3 · 14ND3, which has been prepared for the first time, was obtained. All absorption frequencies can be coordinated on the ground of the molecule model for the NI3 scaffold with 5 atoms Z2XY2 of the symmetry C2v which has been proved by X ray examination. A set of force constants has been calculated by approximation. The various nitrogeniodine valence force constants are discussed. 相似文献
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Tsirelson Vladimir Abramov Yury Zavodnik Valery Stash Adam Belokoneva Elena Stahn Jochen Pietsch Ullrich Feil Dirk 《Structural chemistry》1998,9(4):249-254
The critical points in the model electron density distributions of LiF, NaF, NaCl, and MgO crystals, constructed from accurate X-ray diffraction data, are determined. For LiF and MgO they are compared with those obtained from a Hartree–Fock electron density calculation. Both experiment and theory show the same type of critical points on the bond lines. The topological features in areas between structural units, where the electron density is low and near-uniform, turn out to be model dependent and cannot be established well with the data available. Topological analysis of procrystals (hypothetical systems consisting of spherical atoms or ions placed on the same sites as atoms in real crystal) show that (3, –1) critical points, usually connected with bonding interaction, are observed on interatomic lines in these nonbonded systems as well. 相似文献
35.
Dr. Dumitru-Claudiu Sergentu Dr. Corwin H. Booth Prof. Dr. Jochen Autschbach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(25):7239-7251
The Ce L3 edge XAS spectra of CeO2 and cerocene [Ce(C8H8)2] were calculated with relativistic ab-initio multireference wavefunction approaches capable of reproducing the observed spectra accurately. The study aims to resolve the decades-long puzzle regarding the relationship between the number and relative intensities of the XAS peaks and the 4f electron occupation in the ground state (GS) versus the core-excited states (ESs). CeO2 and cerocene exemplify the different roles of covalent bonding and wavefunction configurational composition in the observed intensity patterns. Good agreement is found between the calculated GS 4f-shell occupations and the value derived from XAS measurements using peak areas (nf). The identity of the two-peaked Ce L3 edge is fully rationalized from the perspective of the relaxed wavefunctions for the GS and core ESs. The states underlying the different peaks differ from each other in a surprisingly simple way that can be associated with 4f1 vs. 4f0 sub-configurations. Furthermore, part of one of the cerocene spectral peaks is associated with 4f2 sub-configurations. The pattern therefore reveals excited states that can be interpreted in terms of Ce IV and III oxidation numbers, as long assumed, with Ce II states additionally appearing in the cerocene spectrum. While this work demonstrates the rough accuracy of the conventional approach to determining nf from Ce L3-edge XAS, limitations are highlighted in terms of the ultimate accuracy of this approach and the potential of observing new types of excited states. The need to determine the sources of nf by calculations, is stressed. 相似文献
36.
The European Physical Journal H - This is a tutorial for the many-worlds theory by Everett, which includes some of my personal views. It has two main parts. The first main part shows the emergence... 相似文献
37.
Dr. Carel Kwamen Dr. Jochen Niemeyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):175-186
Mechanically interlocked molecules (MIMs) have gained attention in the field of catalysis due to their unique molecular properties. Central to MIMs, rotaxanes are highly promising and attractive supramolecular catalysts due to their unique three-dimensional structures and the flexibility of their subcomponents. This Minireview discusses the use of rotaxanes in organocatalysis and transition-metal catalysis. 相似文献
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Even if the first protein therapeutics are now for more than 20 years on the market the selection of suitable adsorbents for the preparative downstream processing (DSP) of these biomolecules as well as the method development towards process conditions are still based mainly on 'trial and error'. Therefore, theses processes are not perfectly efficient, but indeed very time consuming and laborious. In this study a novel systematic method is introduced to find a suitable adsorbent (not necessarily the best one) with appropriate separation parameters for a specific separation with reduced effort. Following this strategy, the adsorbents must first be packed into columns under preparative conditions and then characterized completely with regard to, e.g. pressure drop, k'-values, plate heights (HETP curves), selectivity and capacity by using test substances, which are similar in their characteristics (molecular mass, size, charge distribution, hydrophobicity) to the target proteins. With the database once determined, a preselection of most suitable adsorbents including separation parameters is made regarding chromatographic and also economical properties. After this, preparative experiments must be conducted with a reduced number of adsorbents to figure out the individual influence of side components. This approach is demonstrated for the separation of an exemplary industrial protein mixture using cation-exchange chromatography (CEX). Characterization of different weak CEX-adsorbents is illustrated. After comparing these phases with each other, a first preselection and a prediction of suitable adsorbents is made. In the following preparative separation conditions (load, velocity, gradient) are determined for the preparative separations using the database and results of some additional experiments. The final comparison of separation performance in preparative scale confirms this selection and so the applicability of the new method. 相似文献
40.
In this work, we present studies of ultra-thin polycrystalline silicon layers (5–100 nm) prepared by the aluminum-induced layer exchange process. Here, a substrate/Al/oxide/amorphous Si layer stack is annealed at temperatures below the eutectic temperature of the Al/Si system of 577 °C, leading to a layer exchange and the crystallization of the amorphous Si. We have studied the process dynamics and grain growth, as well as structural properties of the obtained polycrystalline Si thin films. Furthermore, we derive a theoretical estimate of the grain density and examine characteristic thermal activation energies of the process. The structural properties have been investigated by Raman spectroscopy. A good crystalline quality down to a layer thickness of 10 nm has been observed. 相似文献