全文获取类型
收费全文 | 3953篇 |
免费 | 125篇 |
国内免费 | 33篇 |
专业分类
化学 | 2945篇 |
晶体学 | 33篇 |
力学 | 85篇 |
综合类 | 1篇 |
数学 | 536篇 |
物理学 | 511篇 |
出版年
2023年 | 14篇 |
2022年 | 16篇 |
2021年 | 31篇 |
2020年 | 55篇 |
2019年 | 54篇 |
2018年 | 33篇 |
2017年 | 38篇 |
2016年 | 88篇 |
2015年 | 90篇 |
2014年 | 99篇 |
2013年 | 212篇 |
2012年 | 206篇 |
2011年 | 324篇 |
2010年 | 120篇 |
2009年 | 126篇 |
2008年 | 257篇 |
2007年 | 259篇 |
2006年 | 257篇 |
2005年 | 251篇 |
2004年 | 224篇 |
2003年 | 162篇 |
2002年 | 158篇 |
2001年 | 41篇 |
2000年 | 48篇 |
1999年 | 40篇 |
1998年 | 37篇 |
1997年 | 42篇 |
1996年 | 60篇 |
1995年 | 35篇 |
1994年 | 43篇 |
1993年 | 45篇 |
1992年 | 35篇 |
1991年 | 36篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 24篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 46篇 |
1984年 | 39篇 |
1983年 | 30篇 |
1982年 | 54篇 |
1981年 | 43篇 |
1980年 | 41篇 |
1979年 | 32篇 |
1978年 | 40篇 |
1977年 | 32篇 |
1976年 | 24篇 |
1975年 | 31篇 |
1974年 | 19篇 |
排序方式: 共有4111条查询结果,搜索用时 31 毫秒
991.
992.
993.
Ian Barkshire Peter Karduck Werner P. Rehbach Silvia Richter 《Mikrochimica acta》2000,132(2-4):113-128
Performing X-ray microanalysis at beam energies lower than those conventionally used (< 10 keV) is known to significantly
improve the spatial resolution for compositional analysis. However, the reduction in the beam energy which reduces the X-ray
interaction diameter also introduces analytical difficulties and constraints which can diminish the overall analytical performance.
This paper critically assesses the capabilities and limitations of performing low beam energy, high spatial resolution X-ray
microanalysis. The actual improvement in the spatial resolution and the reduction in the X-ray yield are explored as the beam
energy is reduced. The consequences for spectral interpretation, quantitative analysis and imaging due to the lower X-ray
yield and the increased occurrence of X-ray line overlaps are discussed in the context of currently available instrumentation. 相似文献
994.
A. Ian Murdoch 《Journal of Elasticity》2000,60(3):233-242
Restrictions imposed on stress response functions by objectivity and material symmetry are usually obtained by appeal to both
a reference configuration and a response function common to all observers. Here these restrictions are obtained by regarding
the reference configuration to be observer-dependent in a natural manner, and without the need to assume the existence of
a common response function. Remarks are made on the distinction which should be drawn between the notions of observer transformation
and rigid deformation, the consequences of this distinction for the correct interpretation of ‘invariance under superposed
rigid motions’, and on the domains of response functions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
996.
997.
A convenient scaleable process for the preparation of substituted phenylglycines 2 by a modified Strecker reaction is described. Bisulfite-mediated addition of benzylamine and cyanide anion to substituted benzaldehydes 3 gave the aminonitriles 4 which were hydrolysed in two steps to the N-protected amino acid 1. Debenzylation using catalytic transfer hydrogenation gave the title compounds in good yield. 相似文献
998.
999.
Daniel E. Lynch Ian McClenaghan 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e588-e588
The structure of the title compound, C14H12ClNO2, (I), comprises essentially planar molecules which crystallize in a monoclinic lattice. C—H?O interactions exist to both naphthoquinone O atoms and the Cl atom. 相似文献
1000.
Qiang Yu Ian Turner Fawang Liu Timothy Moroney 《Numerical Methods for Partial Differential Equations》2023,39(1):383-420
The distributed-order time fractional diffusion model with Dirichlet nonhomogeneous boundary conditions on a finite domain is considered. Four choices of continuous distribution weight functions with mean μ and standard deviation σ are investigated to study their impact on both the short-time and long-time solution behavior. An implicit numerical method implemented on a graded mesh is proposed to solve the model and the stability and convergence analysis are presented. Semi-analytic solutions are also derived for these distributions to assess the accuracy of the scheme. Numerical results highlight that the four continuous distribution weight functions produce a short-time solution behavior that is consistent with those solutions from the classical time fractional partial differential equation with fractional order γ* = μ. There are however long-time differences in the solution behavior that become more distinguishable as σ increases. In particular, we find a smaller value of σ produces more diffuse profiles and the diffusion rate slows as σ increases. Furthermore, the asymptotic behavior of the solution may be influenced by the time-fractional orders ranging between the smallest nonzero weight order and mean μ for the continuous uniform and raised cosine distribution weight functions, respectively. Similar findings are also observed for the truncated normal and beta distributions. 相似文献