全文获取类型
收费全文 | 621篇 |
免费 | 134篇 |
国内免费 | 38篇 |
专业分类
化学 | 109篇 |
力学 | 397篇 |
综合类 | 1篇 |
数学 | 20篇 |
物理学 | 266篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 24篇 |
2019年 | 28篇 |
2018年 | 14篇 |
2017年 | 24篇 |
2016年 | 23篇 |
2015年 | 26篇 |
2014年 | 30篇 |
2013年 | 44篇 |
2012年 | 40篇 |
2011年 | 49篇 |
2010年 | 29篇 |
2009年 | 38篇 |
2008年 | 39篇 |
2007年 | 38篇 |
2006年 | 27篇 |
2005年 | 41篇 |
2004年 | 38篇 |
2003年 | 21篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 21篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 20篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有793条查询结果,搜索用时 15 毫秒
1.
2.
The use of liquid fuels such as kerosene is of interest for the pulse detonation engine (PDE). Within this context, the aim
of this work, which is a preliminary study, was to show the feasibility to initiate a detonation in air with liquid-fuel pyrolysis
products, using energies and dimensions of test facility similars to those of PDEs. Therefore, two liquids fuels have been
compared, JP10, which is a synthesis fuel generally used in the field of missile applications, and decane, which is one of
the major components of standard kerosenes (F-34, Jet A1, ...). The thermal degradation of these fuels was studied with two
pyrolysis processes, a batch reactor and a flow reactor. The temperatures varied from 600°C to 1,000°C and residence times
for the batch reactor and the flow reactor were, respectively, between 10–30 s and 0.1–2 s. Subsequently, the detonability
of synthetic gaseous mixtures, which was a schematisation of the decomposition state after the pyrolysis process, has been
studied. The detonability study, regarding nitrogen dilution and equivalence ratio, was investigated in a 50 mm-diameter,
2.5 m-long detonation tube. These dimensions are compatible with applications in the aircraft industry and, more particularly,
in PDEs. Therefore, JP10 and decane were compared to choose the best candidate for liquid-fuel PDE studies.
This paper was based on work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Montreal, Canada, July 31 – August 5, 2005. 相似文献
3.
4.
Molecular Dynamics Simulations of Energetic Solids 总被引:1,自引:0,他引:1
A continuing objective in the area of energetic materials is to reduce sensitivity toward impact and shock. One approach is to develop a better understanding of how factors related to the crystal lattice, e.g., defects, influence the initiation and propagation of detonation. Molecular dynamics is a useful tool for this purpose. This paper presents an overview of molecular dynamics treatments of energetic solids. Some of these have simulated initiation and propagation in idealized systems; others have focused on developing a satisfactory procedure for describing molecular crystals of practical significance. Our emphasis in this discussion is on the progress that has been made along the second lines. 相似文献
5.
《Mendeleev Communications》2020,30(1):84-87
- Download : Download high-res image (155KB)
- Download : Download full-size image
6.
We have calculated the heats of formation (HOFs) for a series of polyazidocubanes by using the density functional theory (DFT), Hartree-Fock, and MP2 methods with 6-31G* basis set as well as semiempirical methods. The cubane skeleton was chosen for a reference compound, that is, the cubane skeleton was not broken in the process of designing isodesmic reactions. There exists group additivity for the HOF with respect to the azido group. The semiempirical AM1 method also produced reliable results for the HOFs of the title compounds, but the semiempirical MINDO3 did not. The relationship between HOFs and molecular structures was discussed. It was found that the HOF increases 330-360 kJ/mol for each additional number of the azido group being added to the cubane skeleton. The distance between azido groups slightly influences the values of HOFs. The interacting energies of neighbor azido groups in polyazidocubanes are in the range of 2.3 approximately 6.6 kJ/mol, which are so small and less related to the substituent numbers. The average interaction energy between nearest neighbor --N3 groups in the most stable conformer of octaazidocubane is 2.29 kJ/mol at the B3LYP/6-31G* level. The relative stability related to the number of azido groups of the title compounds was assessed based on the calculated HOFs, the energy gaps between the frontier orbitals, and the bond orders of the C--N3 and C--C bonds. The predicted detonation velocity of hepta- and octa-derivatives is over 9 km/s, and the detonation pressure of them is ca. 40 GPa or over. 相似文献
7.
The regions of variation of density, enthalpy of formation, and detonation velocity of all of the formally possible structual isomers were determined for several molecular formulas of C,H,N,O-containing explosives. The histograms of the distribution of the structual isomers over these parameters were constructed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 859–862, May, 1995.The authors are grateful to Mrs. I. D. Solodukhina for the design of the graphical material.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 94-03-09323). 相似文献
8.
- Download : Download high-res image (201KB)
- Download : Download full-size image
9.
《Particuology》2016
The nanosize grain growth characteristics of spherical single-crystal titanium oxide (TiO2) during the rapid gaseous detonation reaction are discussed. Based on the experimental conditions and the Chapman–Jouguet theory, the Kruis model was introduced to simulate the growth characteristics of spherical TiO2 nanoparticles obtained under high pressure, high temperature and by rapid reaction. The results show that the numerical analysis can satisfactorily predict the growth characteristics of spherical TiO2 nanoparticles with diameters of 15–300 nm at different affecting factors, such as concentration of particles, reaction temperature and time, which are in agreement with the obtained experimental results. We found that the increase of the gas-phase reaction temperature, time, and particle concentration affects the growth tendency of spherical nanocrystal TiO2, which provides effective theoretical support for the controllable synthesis of multi-scale nanoparticles. 相似文献
10.
SUI GuoFa LI JinShan SUN Feng* MA Bei & LI HongWei State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi’an China 《中国科学:物理学 力学 天文学(英文版)》2011,(5)
A 3D finite element model of the explosive welding process of three-layer plates with materials of steel-copper-copper is established. Based on the presented model, the bonding mechanism is simulated and analyzed, different detonation modes are also comparatively studied to indicate the driving force spread in few microseconds. The results show that the three layer plates bond together after many times of impact between the flyers and the base driven by detonation wave, which is damping rapidly at each impa... 相似文献