全文获取类型
收费全文 | 72篇 |
免费 | 64篇 |
国内免费 | 46篇 |
专业分类
化学 | 67篇 |
力学 | 2篇 |
数学 | 40篇 |
物理学 | 73篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 15篇 |
2012年 | 9篇 |
2011年 | 19篇 |
2010年 | 14篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有182条查询结果,搜索用时 0 毫秒
61.
采用一维层流预混火焰模型对二甲醚/甲醇/空气预混气体的流动反应过程进行了数值模拟, 考察甲醛、甲酸等污染物的生成规律. 结果表明: 在低流速下, 添加甲醇能够改变二甲醚反应途径, 抑制二甲醚的低温氧化反应. 当添加和二甲醚等质量的甲醇时, 二甲醚几乎不发生低温氧化反应, 生成的OH自由基减少是导致其发生的主要原因. 随着甲醇添加量的增加, 甲酸排放指数EIHCOOH迅速降低, 而甲醛排放指数EIHCHO在少量增加后持续降低. 添加适量甲醇能够同时降低这两种污染物的排放指数. 相似文献
62.
Approximate proximal point algorithms (abbreviated as APPAs) are classical approaches for convex optimization problems and
monotone variational inequalities. In Part I of this paper (He et al. in Proximal-like contraction methods for monotone variational
inequalities in a unified framework I: effective quadruplet and primary methods, 2010), we proposed a unified framework consisting of an effective quadruplet and a corresponding accepting rule. Under the framework,
various existing APPAs can be grouped in the same class of methods (called primary or elementary methods) which adopt one
of the geminate directions in the effective quadruplet and take the unit step size. In this paper, we extend the primary methods
by using the same effective quadruplet and the accepting rule. The extended (general) contraction methods need only minor
extra even negligible costs in each iteration, whereas having better properties than the primary methods in sense of the distance
to the solution set. A set of matrix approximation examples as well as six other groups of numerical experiments are constructed
to compare the performance between the primary (elementary) and extended (general) methods. As expected, the numerical results
show the efficiency of the extended (general) methods are much better than that of the primary (elementary) ones. 相似文献
63.
The decoding principle of a tetra wedge anode, which is a development of the wedge and strip anode, is described. The influence of charge cloud size on decoding accuracy is studied using the Monte Carlo method. Simulation results show that the decoding error is large when the size of charge clouds collected by the anode is small. Thus, the charge clouds collected by the tetra wedge anode should reach a necessary size to ensure accurate decoding. Finally, using the ultraviolet photon counting imaging system, the linearity and the spatial resolution of the system are tested. Experimental results show that the system has a good linearity and the spatial resolution is better than 100 μm. 相似文献
64.
The coupling of lower hybrid wave to the plasma is a
crucial issue for efficient current drive in tokamaks. This paper
establishes a new coupling model which assumes the antenna to be a
curved face and the plasma to be a cylinder. Power spectrum considering
the coupling between wave-guides in both poloidal and toroidal
direction is simply estimated and discussed. The effect of the poloidal wave
vector on wave propagation, power deposition and driven current is
also investigated with the help of lower hybrid current drive code.
Results show that the poloidal wave vector affects the ray tracing,
and also has effect on power deposition and driven current. The
effect of the poloidal wave vector on power deposition and driven
current profile depends on plasma parameters. Preliminary studies
suggest that it seems possible to control the current profile by
adjusting the poloidal phase difference between the waveguide in
poloidal direction. 相似文献
65.
66.
利用无机纳米材料与有机聚合物材料相结合的方法制备白光发光二极管器件, 研究了蓝光量子点QDs(B)掺杂聚[2-甲氧基-5-(2-乙基己氧基-1, 4-苯撑乙烯撑](MEH-PPV) 复合体系的发光特性及量子点QDs(B) 掺杂浓度(质量分数)不同对器件发光特性的影响. 制备了ITO/PEDOT:PSS/MEH-PPV:QDs(B)/LiF/Al 结构的电致发光器件, 测试了器件的电致发光光谱和电学、光学特性. 当QDs掺杂浓度为40%, 驱动电压为8 V时器件能得到较为理想的白光发射. 同时, 对比研究了非掺杂体系的发光特性, 制备了结构为ITO/PEDOT:PSS/MEH-PPV/QDs(B)/LiF/Al的器件, 掺杂体系相较于非掺杂体系, 器件的最大亮度增大, 启亮电压降低, 并分析了掺杂体系器件性能改善的原因. 相似文献
67.
Mathematical Programming - A new scheme to cope with two-stage stochastic optimization problems uses a risk measure as the objective function of the recourse action, where the risk measure is... 相似文献
68.
本文根据σ模型论证了由反常中子态可以形成一种新的致密天体——反常中子星,它是晚期恒星的一个重要阶段或一种重要类型。讨论了正常中子星和反常中子星的稳定性问题以及不稳-亚稳-稳定之间的变化问题,给出了各转变点的临界值。大体上说,质量M(?)0.8M⊙时,正常中子星是稳定的,反常中子星是亚稳的;质量M(?)0.8M⊙时,正常中子星是亚稳的,反常中子星是稳定的;亚稳正常中子星的质量极限Mmaxn~2M⊙,稳定反常中子星的质量极限Mmaxa~4M⊙。亚稳天体的存在以及亚稳-稳定的变化过程,可能会提供一些爆发性释能的新机制。 相似文献
69.
锂离子电池用Li4Ti5O12-碳复合材料的制备与电化学性能 总被引:6,自引:0,他引:6
Li4Ti5O12-C composite was prepared by sol-gel method using ethyl alcohol as solvent, lithium acetate and tetrabutyl titanate as raw materials, and graphite as carbon source. Li4Ti5O12-C composites were characterized by thermogravimertric(TG) analysis and differential thermal analysis(DTA), X-ray diffraction(XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and electrochemical tests. Results show that Li4Ti5O12-C composite with 5% carbon containing can be obtained by annealing the precursor at 600 ℃ for 6 h in N2 atomsphere. The composites can deliver a specific capacity of 167.1 mAh·g-1, 99.0% and 105.1% of the capacity can be retained after discharged for 80 times at 0.1C and 2.0C, respectively. Compared with pure Li4Ti5O12, Li4Ti5O12-C composite shares larger discharge capacity, better cyclability and rate performance. 相似文献
70.