全文获取类型
收费全文 | 434篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 331篇 |
晶体学 | 9篇 |
力学 | 9篇 |
数学 | 39篇 |
物理学 | 62篇 |
出版年
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 13篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 16篇 |
2016年 | 13篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 37篇 |
2012年 | 14篇 |
2011年 | 43篇 |
2010年 | 14篇 |
2009年 | 10篇 |
2008年 | 26篇 |
2007年 | 19篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1992年 | 8篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有450条查询结果,搜索用时 31 毫秒
361.
We consider a family of steady free‐surface flow problems in two dimensions, concentrating on the effect of nonlinearity on the train of gravity waves that appear downstream of a disturbance. By exploiting standard complex variable techniques, these problems are formulated in terms of a coupled system of Bernoulli equation and an integral equation. When applying a numerical collocation scheme, the Jacobian for the system is dense, as the integral equation forces each of the algebraic equations to depend on each of the unknowns. We present here a strategy for overcoming this challenge, which leads to a numerical scheme that is much more efficient than what is normally used for these types of problems, allowing for many more grid points over the free surface. In particular, we provide a simple recipe for constructing a sparse approximation to the Jacobian that is used as a preconditioner in a Jacobian‐free Newton‐Krylov method for solving the nonlinear system. We use this approach to compute numerical results for a variety of prototype problems including flows past pressure distributions, a surface‐piercing object and bottom topographies. 相似文献
362.
363.
364.
Recently it has been proved that any arithmetically Cohen–Macaulay (ACM) bundle of rank two on a general, smooth hypersurface
of degree at least three and dimension at least four is a sum of line bundles. When the dimension of the hypersurface is three,
a similar result is true provided the degree of the hypersurface is at least six. We extend these results to complete intersection
subvarieties by proving that any ACM bundle of rank two on a general, smooth complete intersection subvariety of sufficiently
high multi-degree and dimension at least four splits. We also obtain partial results in the case of threefolds. 相似文献
365.
366.
367.
368.
Coumarins: Spectroscopic measurements and first principles calculations of C4‐substituted 7‐aminocoumarins
下载免费PDF全文
![点击此处可从《Journal of Physical Organic Chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shraddha Singh Vagarshak V. Begoyan Marina Tanasova Kevin Waters Max Seel Ravindra Pandey 《Journal of Physical Organic Chemistry》2018,31(9)
Coumarins are widely applied in sensing devices due to their diverse fluorescence properties. In this paper, we consider the C4‐substituted 7‐aminocoumarins to investigate the structure‐property relationship via examining the effect of the various substitutions on their optical properties. Absorption and fluorescence measurements together with time‐dependent density functional theory calculations are described. We find that the significant red shift in the fluorescence spectra is associated with the cyclic carbonyl group of coumarins due to a substantial increase in the dipole moment in the photoexcited state. The apparent correlation between experimental and calculated results provides an atomistic‐level insight into the role of the functionality at the C4 of coumarins and sets the basis for using computational analysis to predict the fluorescence properties of coumarins. 相似文献
369.
Ravindra N. Bulakhe Sandeep A. Arote Binhee Kwon Seongmin Park Insik In 《Materials Today Chemistry》2020
A facile synthesis of nickel cobalt sulfide (NCS) nanoflowers have been deposited successfully onto binder free 3D nickel foam electrodes using simple successive ionic layer adsorption and reaction (SILAR) method for supercapacitor applications. The obtained NCS nanoflowers manifest ultrahigh specific capacitance of 1899 F g?1 at a scan rate of 5 mV s?1. The NCS nanoflowers exhibit a prominent energy density of 55.16 Wh kg?1 at power density of 495 W kg?1 and superior cyclic stability of 94% after 10000 cycles. In addition, the asymmetric supercapacitor (ASC) device is fabricated using NCS nanoflower as positive and reduced graphene oxide (rGO) as negative electrodes, respectively. The ASC (NCS//rGO) delivered good capacity with excellent energy and power densities within 1.6 V wider potential window. Hence, NCS nanoflowers are an outstanding material for energy storage applications in near future. 相似文献
370.
This paper describes the results of the effect of 24 MeV proton and 60Co γ-irradiation on the collector characteristics and forward current gain of commercial bipolar transistor (npn 2N2219A). The transistor has been exposed to these radiations in the biased condition and the collector characteristics and forward current gain have been measured as a function of proton fluence and γ-dose. The observation is that both the proton and γ-irradiation induce significant gain degradation in the transistor. The results are discussed in terms of displacement damage produced by energetic protons and γ-radiation in the bulk of the semiconductor. 相似文献