全文获取类型
收费全文 | 131篇 |
免费 | 43篇 |
国内免费 | 22篇 |
专业分类
化学 | 47篇 |
晶体学 | 6篇 |
力学 | 51篇 |
综合类 | 7篇 |
数学 | 15篇 |
物理学 | 70篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有196条查询结果,搜索用时 31 毫秒
91.
四种不同基团取代的苯酚锂盐分别与三叔丁基膦亚胺三氯化钛进行反应,制得相应三叔丁基膦亚胺苯氧钛配合物(t-Bu_3)PNTi(OAr)Cl_2[OAr=O-C_6H_5(4a),O-2,6-Me_2C_6H_3(4b),O-2,6-i-Pr_2C_6H_3(4c)和O-2,6-t-Bu_2C_6H_3(4d)],产物均借助~1H NMR,~(13)C NMR,~(31)P NMR及元素分析进行了结构表征,并利用X射线单晶衍射确定了配合物三叔丁基膦亚胺三氯化钛(3),4b和4d的分子结构.在助催化剂甲基铝氧烷(MAO)作用下,4a~4d对乙烯聚合均表现出高催化活性,并随配合物空间位阻增加而升高.4c热稳定性好,通过控制聚合反应条件,由此可以得到不同分子量及分子量分布的聚乙烯产物. 相似文献
92.
针对模糊随机桁架结构的动力特性分析,提出了一种新的模糊随机有限元方法.当结构的物理参数和几何尺寸同时具有模糊随机性时,利用模糊因子法和随机因子法建立了结构刚度矩阵和质量矩阵;从结构振动的Rayleigh商表达式出发,利用区间运算推导出结构动力特性模糊随机变量的计算表达式;之后利用随机变量的矩法和代数综合法,推导出结构特征值的数字特征的计算式.通过算例分析了模糊随机桁架结构参数的模糊随机性对其动力特性的影响.该方法的优点是能准确反映结构某一参数的模糊随机性对结构特征值及其数字特征的影响. 相似文献
93.
Long-range surface plasmon polaritons with subwavelength mode expansion in an asymmetrical system
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Long-range surface plasmon polariton (LRSPP) modes in an
asymmetrical system, in which the thin metal film is sandwiched
between a semi-infinite substrate and a high permittivity polymer
film with a finite thickness, are theoretically calculated and
analyzed. Due to the high permittivity of the polymer film, at
proper polymer film thicknesses, the index-matching condition of the
dielectrics at both sides of the metal can be satisfied for
supporting LRSPP modes, and the electromagnetic field above the
metal can be localized well. It is found that these LRSPP modes have
both long propagation lengths and subwavelength mode expansion above
the metal at the optimal polymer film thicknesses. Furthermore, the
requirements on the refractive index and the thickness of the
polymer film to support LRSPP modes at the optimal thicknesses are
found to be not critical. 相似文献
94.
Bending Loss Calculation of a Dielectric-Loaded Surface Plasmon Polariton Waveguide Structure
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Based on full 3D finite element method simulations, the transmission of a dielectric-loaded surface plasmon polariton waveguide (DLSPPW) based 1/4 circle is calculated for a 90° bend model and a 270° bend model, respectively. It is found that the 270° bend model gives almost pure bending loss while the 90° bend model contains additional coupling loss. The models are applied to deduce the loss and unloaded quality factor of DLSPPW based waveguide ring resonators (WRRs) and the results of the 270° bend model agree well with direct simulating results of the WRRs. Thus the 270° bend model gives a fast and simple way to calculate bending loss and it is helpful for WRR design because no wavelength scan is needed. 相似文献
95.
96.
97.
98.
Morphological and structural damage investigation of nanostructured molybdenum fuzzy surface after pulsed plasma bombardment
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yu-Chuan Luo 《中国物理 B》2022,31(4):45203-045203
Steady high-flux helium (He) plasma with energy ranging from 50 eV to 90 eV is used to fabricate a fiber-form nanostructure called fuzz on a polycrystalline molybdenum (Mo) surface. Enhanced hydrogen (H) pulsed plasma in a wide power density range of 12 MW/m2-35 MW/m2 is subsequently used to bombard the fuzzy Mo, thereby simulating the damage of edge localized mode (ELM) to fuzz. The comparisons of surface morphologies, crystalline structures, and optical reflectivity between the original Mo and the Mo treated with various He+ energy and transient power densities are performed. With the increase of He ion energy, the Mo nano-fuzz evolved density is enlarged due to the decrease of filament diameter and optical reflectivity. The fuzz-enhanced He release should be the consequence of crystalline growth and the lattice shrinkage inside the Mo-irradiated layers (~200 nm). The fuzz induced by lower energy experiences more severe melting damage and dust release under the condition of the identical transient H plasma-bombardment. The H and He are less likely to be trapped due to aggravated melting evidenced by the enhanced crystalline size and distinct lattice shrinkage. As the transient power density rises, the thermal effect is enhanced, thereby causing the fuzz melting loss to aggravate and finally to completely disappear when the power density exceeds 21 MW/m2. Irreversible grain expansion results in huge tensile stress, leading to the observable brittle cracking. The effects of transient thermal load and He ion energy play a crucial role in etching Mo fuzz during ELM transient events. 相似文献
99.
100.
Although hot carriers induced degradation of NMOSFETs has been studied for decades, the role of hot electron in this process is still debated. In this paper, the additional substrate hot electrons have been intentionally injected into the oxide layer to analyze tile role of hot electron in hot carrier degradation. The enhanced degradation and the decreased time exponent appear with the injected hot electrons increasing, the degradation increases from 21.80% to 62.00% and the time exponent decreases from 0.59 to 0.27 with Vb decreasing from 0 V to -4 V, at the same time, the recovery also becomes remarkable and which strongly depends on the post stress gate bias Vg. Based on the experimental results, more unrecovered interface traps are created by the additional injected hot electron from the breaking Si-H bond, but the oxide trapped negative charges do not increase after a rapid recovery. 相似文献