全文获取类型
收费全文 | 103篇 |
免费 | 5篇 |
国内免费 | 24篇 |
专业分类
化学 | 58篇 |
晶体学 | 2篇 |
力学 | 8篇 |
综合类 | 2篇 |
数学 | 30篇 |
物理学 | 32篇 |
出版年
2022年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 10篇 |
2004年 | 26篇 |
2003年 | 15篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 13篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
排序方式: 共有132条查询结果,搜索用时 15 毫秒
1.
2.
3.
In this paper, we study the existence, uniqueness, and the global exponential stability of the periodic solution and equilibrium of hybrid bidirectional associative memory neural networks with discrete delays. By ingeniously importing real parameters di > 0 (i = 1,2, …, n) which can be adjusted, making use of the Lyapunov functional method and some analysis techniques, some new sufficient conditions are established. Our results generalize and improve the related results in [9]. These conditions can be used both to design globally exponentially stable and periodical oscillatory hybrid bidirectional associative neural networks with discrete delays, and to enlarge the area of designing neural networks. Our work has important significance in related theory and its application. 相似文献
4.
Yu Lin Ting Xie Baochang Cheng Baoyou Geng Lide Zhang 《Chemical physics letters》2003,380(5-6):521-525
Ordered NiO nanowire arrays embedded in anodic alumina membranes have been prepared by using an electrochemical deposition method. After annealing at 300 °C, the NiO nanowire arrays were characterized using SEM, TEM, SAED, and XRD. SEM and TEM observations reveal that these nanowires are dense, continuous and arranged roughly parallel to one another. XRD and SAED analysis together indicate that these NiO nanowires crystallize with a polycrystalline structure. The optical absorption band gap of NiO nanowire arrays is 3.74 eV, and no obvious blue shift or red shift with respect of that of the bulk NiO can be observed. 相似文献
5.
The drug-loaded alginate/poly-L-arginine/chitosan ternary complex microcapsules were prepared by mixing method, absorption method and the combined method of mixing and absorption, respectively. The effect of drug-loading methods on drug load, the encapsulation efficiency and the release properties of the complex microcapsules were investigated. The results showed that the absorption process is a dominating factor to greatly increase the drug load of Hb into microcapsules. Upon loading Hb into microcapsules by combined method of mixing and absorption, the drug load (19.9%) is up to the maximum value, and the encapsulation efficiency is 93.8%. Moreover, the drug release is a zero-order kinetics process for the ternary complex microcapsules made by mixing. For the complex microcapsules made by absorption, the drug release is a first-order kinetics. However, for the complex microcapsules made by combining the mixing and the absorption, the drug release obeys a first-order kinetics during the first eighteen hours, changing afterwards to a zero-order kinetics process. Effect of drug-loading methods on drug load and encapsulation efficiency of alginate/poly-L-arginine/chitosan ternary complex microcapsules. 相似文献
6.
Enhancing the organic dye adsorption on porous xerogels 总被引:4,自引:0,他引:4
Zhijian Wu Ik-Sung Ahn Chang-Ha Lee Jung-Hyun Kim Yong Gun Shul Kangtaek Lee 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,240(1-3):157-164
We investigate the adsorption of four different organic dyes (i.e., methyl orange, alizarin red S, brilliant blue FCF, and phenol red) on porous xerogels. To understand the factors affecting the adsorption capacity of the xerogels, we vary the hydrophobicity and the textural properties of the xerogels as well as the solution pH. We control the hydrophobicity by mixing two different precursors (i.e., vinyltriethoxysilane (VTES) and tetraethoxysilane (TEOS)) and the textural properties by using cetyltrimethylammonium bromide (CTAB) as a templating agent. We find that the adsorption capacity is enhanced as the organic/inorganic hybrid xerogel or the templated xerogel is used instead of the purely inorganic or the untemplated xerogel. In all the cases studied, adsorption decreases as the pH is increased due to the electrostatic repulsion between the dyes and the xerogel surface. We find that both the hydrophobic surface and larger pore size/volume are required to enhance the adsorption capacity significantly. 相似文献
7.
合成了3-(水杨酰肼)-丁基-2-酮肟H2L(1,C11H13N3O3)和2个镍的3-(水杨酰肼)-丁基-2-酮肟化合物[Ni(HL)(CH3COO-)(C5H5N)2](2)和[Ni(HL)2]·2C3H7NO(3)。化合物1晶体属单斜晶系,空间群为P21/n,晶体学参数为:a=0.451 87(2) nm,b=2.086 8(1) nm,c=1.224 48(9) nm,β=94.974(3)°,V=1.150 3(1) nm3,Z=4,Dc=1.358 g·cm-3,μ=0.101 mm-1,F(000)=496,R=0.0435,wR=0.142 5。化合物2晶体属单斜晶系,空间群为P21/n,晶体学参数为:a=1.362 39(8) nm,b=1.345 37(6) nm,c=1.438 54(7) nm,β=113.138(3)°,V=2.424 6(2) nm3,Z=4,Dc=1.398 g·cm-3,μ=0.843mm-1,F(000)=1 064,R=0.042 4,wR=0.116 6。化合物3晶体属单斜晶系,空间群为P21/c,晶体学参数为:a=1.104 22(7) nm,b=2.860 1(1) nm,c=1.114 13(7)nm,β=114.589(5)°,V=3.199 5(3) nm3,Z=4,Dc=1.398 g·cm-3,μ=0.667 mm-1,F(000)=1 416,R=0.057 6,wR=0.1535。在化合物1晶体中,酮肟分子之间通过分子间氢键形成二维网状结构。在化合物2中,每个镍(Ⅱ)离子由1个3-(水杨酰肼)-丁基-2-酮肟的2个氮原子和1个氧原子,2个吡啶分子中的2个氮原子和1个乙酸根中的1个氧原子形成畸变的NiN4O2八面体配位构型,存在分子内氢键O-H(肟)…O(乙酸根)和O-H(酚)…N(酰肼)。在化合物3晶体中,每个镍(Ⅱ)离子由2个3-(水杨酰肼)-丁基-2-酮肟的4个氮原子和2个氧原子配位,形成畸变的NiN4O2八面体配位构型。晶体中存在O-H…O和O-H…N两种分子内氢键和O-H…O分子间氢键。 相似文献
8.
N-乙酰皮考林酰肼合镍配合物的合成和晶体结构 总被引:5,自引:0,他引:5
合成了N-乙酰皮考林酰肼α-(C_5H_4N)CONHNHCOCH_3(简写为HL)及其镍配合 物Ni~(II)L_2·1.5CH_3OH·H_2O(C_(17.5)H_(24-)N_6NiO_(6.5))。配合物晶体属 于单斜晶系,空间群为P2_1/c,a = 1.5393 (1) nm, b = 0.80278(7) nm, c = 1. 8245(1) nm, β = 105.985(3)°, V=2.1674(3)nm~3, Z = 4, F(000) = 1004, R = 0.0503。在配合物中,镍(II)原子呈扭曲的N_4O_2八面体配位构型,晶体通 过分子间氢健作用形成一维的无限链状结构。红外光谱表明,配体在形成配合物后 , v (C=O)和v(C=N)红移,电子光谱表明存在π-π~*和d-π~*的跃迁。 相似文献
9.
光象散法测量溶液浓度的研究 总被引:5,自引:2,他引:3
本文报道一种用光象散技术测量溶液浓度的新方法。给出其理论解析、测量原理、系统构成与实验结果。从理论研究与初步实验结果表明,本方法用于自动测量溶液浓度有好的可行性与实用性,亦可作为在线监测。 相似文献
10.
共焦非稳腔中ps激光的内腔倍频 总被引:2,自引:1,他引:1
考虑倍频晶体相位匹配接收角(Angular acceptance)对倍频转换效率的影响,设计了正支(p支)共焦非稳腔Nd:YAP锁模激光器。平行光通过晶体实现完全相位匹配。以BBO和KTP作为腔内倍频元件,分别获得80.6%和60.2%的高效倍频转换,及几十mJ的绿光输出。同时实验测定其它有关参数。 相似文献