全文获取类型
收费全文 | 460篇 |
免费 | 31篇 |
国内免费 | 5篇 |
专业分类
化学 | 309篇 |
晶体学 | 21篇 |
力学 | 7篇 |
综合类 | 1篇 |
数学 | 75篇 |
物理学 | 83篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 20篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 7篇 |
2016年 | 21篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 63篇 |
2012年 | 29篇 |
2011年 | 25篇 |
2010年 | 15篇 |
2009年 | 31篇 |
2008年 | 24篇 |
2007年 | 28篇 |
2006年 | 20篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有496条查询结果,搜索用时 31 毫秒
1.
2.
An optimization approach for planning daily drayage operations 总被引:1,自引:0,他引:1
Yetkin Ileri Mokhtar Bazaraa Ted Gifford George Nemhauser Joel Sokol Erick Wikum 《Central European Journal of Operations Research》2006,14(2):141-156
Daily drayage operations involve moving loaded or empty equipment between customer locations and rail ramps. Our goal is to
minimize the cost of daily drayage operations in a region on a given day. Drayage orders are generally pickup and delivery
requests with time windows. The repositioning of empty equipment may also be required in order to facilitate loaded movements.
The drayage orders are satisfied by a heterogeneous fleet of drivers. Driver routes must satisfy various operational constraints.
We present an optimization methodology for finding cost-effective schedules for regional daily drayage operations. The core
of the formulation is a set partitioning model whose columns represent routes. Routes are added to the formulation by column
generation. We present numerical results for real-world data which demonstrate that our methodology produces low cost solutions
in a reasonably short time. 相似文献
3.
In this paper we will introduce a new type of incidence matrices, namely “Fuzzy incidence matrices”. Also we introduce the fuzzy simplicial complexes in its fuzzy form. We will describe some types of foldings especially the folding of a physical character. 相似文献
4.
在重力场和磁场影响下自旋刚性航天器的周期运动 总被引:1,自引:0,他引:1
考虑重力场和磁场对轴对称航天器本体的影响,研究其质心在圆形轨道上的运动,通过降低系统的运动方程数,并将它变成为一个带电粒子在电磁场作用下的平面运动.确认系统运动是稳定的,并通过Liapunov全纯积分定理,构建其近似的周期运动. 相似文献
5.
Brahim Lakhrissi Mohamed Massoui El Mokhtar Essassi Vincent Lequart Nicolas Joly Patrick Martin Grard Goethals 《Journal of heterocyclic chemistry》2004,41(6):1011-1014
Reaction of 1,5‐benzodiazepin‐2,4‐dione with 3‐O‐substituted‐5,6‐anhydro‐1,2‐isopropylidene‐α‐D‐glucofuranose gave the unexpected N,N'‐di‐glucofuranosyl benzimidazol‐2‐one by a novel rearrangement and ring closure reaction. A mechanism is proposed. 相似文献
6.
Kamaladin Gharanjig Mokhtar Arami Shohre Rouhani Hajir Bahrami Barahman Movassagh Niyaz Mohammad Mahmoodi 《中国化学会会志》2007,54(4):1021-1028
Five novel monoazo disperse dyestuffs based on N‐ester‐1,8‐naphthalimide were synthesized. Acenaphthene was nitrated, then oxidized to 4‐nitro‐1,8‐naphthalic anhydride. 4‐Nitro‐1,8‐naphthalic anhydride was reacted with methyl and ethyl glycinate in alcoholic media, followed with reduction. 4‐Amino‐N‐methyl and ethyl glycinate‐1,8‐naphthalimide were obtained. These products were diazotized and coupled with appropriate aromatic amines to give bluish‐red or violet dyestuffs. All intermediates and dyestuffs were purified and characterized by 1H‐NMR, FTIR, DSC, UV‐VIS and Elemental Analysis. Dispersion of dyestuffs was prepared in water and applied to polyester fabrics. The dyed fabrics showed that four of the synthesized dyestuffs were suitable for coloring polyester fibers, producing deep bluish red with very good build up properties. 相似文献
7.
H. Jaskólska L. Rowińska M. Radwan 《Journal of Radioanalytical and Nuclear Chemistry》1974,20(2):419-428
In view of the inhomogeneous distribution of lanthanum in steel, large samples should be used for the determination of this element. The method elaborated consists in the preparation of an average samople by dissolving 50 g steel and analysing an aliquot of the obtained solution corresponding to 0.5 g of steel. In order to reduce the activity of the sample, iron and some other elements are separated from the steel solution by electrolysis prior to irradiation. The amount of lanthanum contamination introduced during the pre-irradiation treatment of the sample is relatively low (10?10–10?9 g) if the treatment is carried out under suitable conditions. The post-irradiation treatment consists in the separation of24Na by shaking the sample solution with Sb2O5. The140La-activity is measured by means of a γ-spectrometer (1.6 MeV photopeak). 相似文献
8.
Four kinds of polythiophenes have been doped with CH3SO3H in CHCl3 under air, oxygen, and nitrogen. In the doping of two types of poly(3-hexylthiophene)s, P3HexTh(Zn/Ni) and P3HexTh(Fe) with different contents of a head-to-tail unit, the p-doping occurs at a similar rate. The reaction between poly(3-dodecylthiophene), P3DodTh, and the acid takes place more rapidly. P3OBuTh with a butoxy substituent undergoes more facile p-doping and receives photochemical reaction with CHCl3, and this reaction obeys a pseudo-first-order rate law with a rate constant kobs of 1.42×10-5 s-1 at room temperature. 相似文献
9.
In this paper, we establish the existence of multiple solutions for nonhomogeneous singular elliptic equations with cylindrical weights, by using Ekeland??s variational principle and mountain pass theorem without Palais?CSmale condition. 相似文献
10.
Metal complexes of novel Schiff base derived from the condensation of 2‐quinoline carboxaldehyde and ambroxol drug with some transition metal ions
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A new Schiff base was prepared as the condensation product of the reaction of 2‐quinoline carboxaldehyde and ambroxol drug. The Schiff base ligand thus obtained (HL; trans‐4‐[(2‐(2‐quinolinoimino)‐3,5‐dibromobenzyl)amino]cyclohexanol) was further employed as a tridentate ligand for the synthesis of new complexes through reaction with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) metal ions. The synthesized HL and its metal complexes were characterized using various physicochemical techniques including elemental analysis, Fourier transform infrared and UV–visible spectroscopies, conductimetric and magnetic susceptibility measurements, mass spectrometry and thermal analyses. 1H NMR data indicated that complex formation was through the amino group rather than the aliphatic hydroxyl group. Thermal analysis gave an idea about the decomposition pattern of HL and its complexes. Also, it revealed the number of water molecules in the inner and outer spheres of the complexes. An octahedral geometry for all the complexes has been suggested. HL and its complexes were screened for their antimicrobial activity against various species of bacteria and fungi using the disc diffusion method. The Cr(III) complex had the highest antimicrobial activity. 相似文献