全文获取类型
收费全文 | 987篇 |
免费 | 36篇 |
国内免费 | 27篇 |
专业分类
化学 | 536篇 |
晶体学 | 10篇 |
力学 | 23篇 |
数学 | 107篇 |
物理学 | 374篇 |
出版年
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 16篇 |
2013年 | 74篇 |
2012年 | 42篇 |
2011年 | 49篇 |
2010年 | 27篇 |
2009年 | 18篇 |
2008年 | 51篇 |
2007年 | 35篇 |
2006年 | 46篇 |
2005年 | 41篇 |
2004年 | 45篇 |
2003年 | 41篇 |
2002年 | 51篇 |
2001年 | 34篇 |
2000年 | 35篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 24篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 24篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 18篇 |
1977年 | 9篇 |
1976年 | 14篇 |
1975年 | 10篇 |
1974年 | 4篇 |
1973年 | 9篇 |
1972年 | 6篇 |
排序方式: 共有1050条查询结果,搜索用时 15 毫秒
111.
Zhakhovsky VV Budzevich MM Inogamov NA Oleynik II White CT 《Physical review letters》2011,107(13):135502
By decoupling time and length scales in moving window molecular dynamics shock-wave simulations, a new regime of shock-wave propagation is uncovered characterized by a two-zone elastic-plastic shock-wave structure consisting of a leading elastic front followed by a plastic front, both moving with the same average speed and having a fixed net thickness that can extend to microns. The material in the elastic zone is in a metastable state that supports a pressure that can substantially exceed the critical pressure characteristic of the onset of the well-known split-elastic-plastic, two-wave propagation. The two-zone elastic-plastic wave is a general phenomenon observed in simulations of a broad class of crystalline materials and is within the reach of current experimental techniques. 相似文献
112.
I. Usman Z. Buthelezi J. Carter G.R.J. Cooper R.W. Fearick S.V. Förtsch H. Fujita Y. Fujita Y. Kalmykov P. von Neumann-Cosel R. Neveling P. Papakonstantinou A. Richter R. Roth A. Shevchenko E. Sideras-Haddad F.D. Smit 《Physics letters. [Part B]》2011
The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in 40Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at Ep=200 MeV. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon–nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for 40Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle–two-hole (2p–2h) states. 相似文献
113.
The control of regiochemistry in the synthesis of polysaccharide derivatives is one of the most significant scientific challenges
in the field. Its importance is only further highlighted by the individual successes in synthesis of regioselectively substituted
derivatives, in particular cellulose esters and ethers, over the last 20 years. The availability of these samples and studies
of their properties versus randomly substituted analogs has shown clearly that properties like solubility, aggregation phenomena,
and optical properties depend heavily on the regiochemistry of substitution. We report here on the one-pot synthesis of novel
6-bromo-6-deoxy-2,3-O-acylcellulose derivatives, which as more organic soluble derivatives of 6-bromo-6-deoxycellulose should allow broader exploitation
of the highly regioselective cellulose 6-bromination chemistry. We illustrate the potential of these new derivatives by conversion
to 6-cyano-6-deoxycellulose esters. 相似文献
114.
The objective of this research is to determine whether Systems Dynamics (SD) is a beneficial method for modelling hospital patient flow from a strategic planning perspective. While discrete event simulation has frequently been used as a tool for analysing and improving patient flow in health care settings, the desire to assess and understand patient flow and resource demand from a more strategic, and therefore aggregate, perspective led to the use of SD. To evaluate the suitability of such an approach, a model was developed in collaboration with the General Campus at The Ottawa Hospital with particular attention paid to the delays experienced by patients in the emergency department. The modelling techniques used, model validation and scenarios tested with the model are discussed, accompanied by comments regarding the appropriateness of SD for such a model. 相似文献
115.
116.
117.
Substitution effects on the stereochemical outcome of bisspiroketalization on the C1-C17 carbon backbone of azaspiracid is presented. A possible explanation is offered to explain the observed stereochemical outcome. 相似文献
118.
119.
以LCD为目标的自动定焦判据选择 总被引:2,自引:0,他引:2
在光学综合自动测量中 ,使用液晶显示屏作为分划板可以大大简化结构 ,提高效率 ,真正地实现自动测量。由于液晶显示具有对比度低、噪声大等特点 ,所以根据液晶的这些特点以及图像处理和CCD信号接收的特点选择两种适用的判据进行了分析和试验比较 ,并给出了结果。结果表明 ,这两种判别函数都适用于以液晶显示屏为目标和用图像处理方法进行光学参数测量的系统 ,其中锐度判别函数更优于信息熵判别函数 ,前者具有更好的抗干扰性和稳定性 ,而且其判定结果更接近目视清晰度判别 相似文献
120.