全文获取类型
收费全文 | 1898篇 |
免费 | 53篇 |
国内免费 | 4篇 |
专业分类
化学 | 1160篇 |
晶体学 | 4篇 |
力学 | 110篇 |
数学 | 341篇 |
物理学 | 340篇 |
出版年
2024年 | 6篇 |
2023年 | 20篇 |
2022年 | 46篇 |
2021年 | 64篇 |
2020年 | 38篇 |
2019年 | 39篇 |
2018年 | 34篇 |
2017年 | 32篇 |
2016年 | 67篇 |
2015年 | 61篇 |
2014年 | 54篇 |
2013年 | 92篇 |
2012年 | 103篇 |
2011年 | 147篇 |
2010年 | 61篇 |
2009年 | 61篇 |
2008年 | 117篇 |
2007年 | 110篇 |
2006年 | 107篇 |
2005年 | 81篇 |
2004年 | 73篇 |
2003年 | 59篇 |
2002年 | 72篇 |
2001年 | 22篇 |
2000年 | 15篇 |
1999年 | 22篇 |
1998年 | 15篇 |
1997年 | 23篇 |
1996年 | 34篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 21篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 5篇 |
排序方式: 共有1955条查询结果,搜索用时 15 毫秒
161.
Leif J. Saethre Michele R. F. Siggel T. Darrah Thomas 《Journal of Electron Spectroscopy and Related Phenomena》1992,60(4):R1-R5
In earlier papers the atoms-in-molecules concept of Bader was used to show the inadequacies of the point-charge model for calculating potentials at atoms in molecules and, hence, for accounting for shifts in core-ionization energies in terms of atomic charges. Because questions have been raised about the suitability of the basis set that was used, part of these calculations has been repeated with the 6-31G** basis set. The conclusions of the earlier study are unchanged: the point-charge model does not accurately give the potentials at atoms in molecules. A multipole model gives better results, but needs to be carried at least to octupole terms. 相似文献
162.
163.
A. De Michele K. Bousbahi G. Carelli A. Moretti 《International Journal of Infrared and Millimeter Waves》2003,24(10):1649-1654
We have investigated CHD2OH methanol as source of far-infrared (FIR) laser radiation using the optical pumping technique. Our new waveguide pulsed CO2 laser, with peak powers as high as some kW, has allowed us to observe 12 new lines. Each of them is characterized in wavelength, relative polarization, intensity, optimum operating pressure and pump offset from the center of the exciting CO2 line. 相似文献
164.
Michele Caputo 《Annali dell'Universita di Ferrara》1995,41(1):73-84
The solution of differential equations of fractional order is generalized to the case when the fractional order derivatives
are integrated with respect to the order of differentiation. The formal solution is found by means of the Laplace Transform.
The solutions of the integro-differential equations, defined by means of derivatives of fractional order and of their integrals
with respect to the order of differentiation, are also discussed in terms of filtering.
Sunto Si generalizza la soluzione di equazioni differenziali di ordine frazionario al caso in cui le derivate frazionarie sono integrate rispetto all’ordine di differenziazione. La soluzione formale è trovata a mezzo della Transformata di Laplace. Le soluzioni delle equazioni integrodifferenziali, definite a mezzo delle derivate di ordine frazionario e dei loro integrali rispetto all’ordine di differenziazione, sono discusse a mezzo della teoria dei filtri.相似文献
165.
David Naso Michele Surico Biagio Turchiano Uzay Kaymak 《European Journal of Operational Research》2007
The coordination of just-in-time production and transportation in a network of partially independent facilities to guarantee timely delivery to distributed customers is one of the most challenging aspect of supply chain management. From a theoretical perspective, the timely production/distribution can be viewed as a hybrid combination of planning, scheduling and routing problems, each notoriously affected by nearly prohibitive combinatorial complexity. From a practical viewpoint, the problem calls for a trade-off between risks and profits. This paper focuses on the ready-mixed concrete delivery: in addition to the mentioned complexity, strict time-constraints forbid both earliness and lateness of the supply. After developing a detailed model of the considered problem, we propose a novel meta-heuristic approach based on a hybrid genetic algorithm combined with constructive heuristics. A detailed case study derived from industrial data is used to illustrate the potential of the proposed approach. 相似文献
166.
167.
Martina Mazzoni Lorenzo Franco Alberta Ferrarini Carlo Corvaja Giovanni Zordan Gianfranco Scorrano Michele Maggini 《Liquid crystals》2002,29(2):203-208
A nitroxide [60]fullerene adduct containing a pyrrolidine-1-oxyl group has been synthesized. Its orientational order in the nematic phase of the liquid crystal solvent 4,4'-azoxyanisole (PAA) has been measured from the variation of the EPR spectral parameters on passing from the isotropic to the nematic phase. Highly resolved EPR lines allow for precise evaluation of the shifts of the g , a N and a H values. Since the g and the hyperfine tensors are known, the order matrix could be obtained. This is compared with the one calculated with a theoretical model based on short range solute-solvent interactions, which predicts a considerable degree of orientation of the molecular axes, despite the almost spherical shape of the molecule. The agreement with experimental findings is quite good and it is further improved if a bent structure of the pyrrolidine ring is taken into account. 相似文献
168.
Susan A. Kirch Mary Ellen Bargerhuff Heidi Turner Michele Wheatly 《School science and mathematics》2005,105(4):175-196
Inclusion is the meaningful participation of students with disabilities in general education classrooms. The CLASS project (Creating Laboratory Access for Science Students) is a unique initiative offering training and resources to help educators provide students with a variety of physical, sensory and learning disabilities equal access in the science laboratory or field. To determine whether participants believed a 2‐week residential workshop sponsored by CLASS raised disability awareness and provided teacher training in inclusive science teaching practice, a multipoint Likert scale survey and questionnaire was completed by all participants (N= 20) in four workshops. Participants reported large gains in their preparedness to teach science to students with disabilities. Participants also reported gains in their familiarity with instructional strategies, curricula, and resources and their ability to design, select, and modify activities for students with disabilities. Finally, shifts in attitudes about teaching science to students with disabilities were noted. 相似文献
169.
This paper represents a first attempt to derive one-dimensional models with non-convex strain energy starting from “genuine” three-dimensional, nonlinear, compressible, elasticity theory. Following the usual method of obtaining beam theories, we show here for a constrained kinematics appropriate for long cylinders governed by a polyconvex, objective, stored energy function, that the bar model originally proposed by Ericksen [3] is obtainable but enriched by an additional term in the strain gradient. This term, characteristic of nonsimple grade-2 materials, penalizes interfacial energies and makes single-interface two-phase solutions preferred. The resulting model has been proposed by a number of authors to describe the phenomenon of necking and cold drawing in polymeric fibers and, here, we discuss its suitability to interpret also the elastic-plastic behavior of metallic tensile bars under monotone loading. 相似文献
170.
Thermal Stability and Molecular Ordering of Organic Semiconductor Monolayers: Effect of an Anchor Group
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Andrew O. F. Jones Philipp Knauer Prof. Roland Resel Dr. Andreas Ringk Prof. Peter Strohriegl Dr. Oliver Werzer Prof. Michele Sferrazza 《Chemphyschem》2015,16(8):1712-1718
The thermal stability and molecular order in monolayers of two organic semiconductors, PBI‐PA and PBI‐alkyl, based on perylene derivatives with an identical molecular structure except for an anchor group for attachment to the substrate in PBI‐PA, are reported. In situ X‐ray reflectivity measurements are used to follow the stability of these monolayers in terms of order and thickness as temperature is increased. Films have thicknesses corresponding approximately to the length of one molecule; molecules stand upright on the substrate with a defined structure. PBI‐PA monolayers have a high degree of order at room temperature and a stable film exists up to 250 °C, but decomposes rapidly above 300 °C. In contrast, stable physisorbed PBI‐alkyl monolayers only exist up to 100 °C. Above the bulk melting point at 200 °C no more order exists. The results encourage using anchor groups in monolayers for various applications as it allows enhanced stability at the interface with the substrate. 相似文献