全文获取类型
收费全文 | 14972篇 |
免费 | 1476篇 |
国内免费 | 733篇 |
专业分类
电工技术 | 305篇 |
技术理论 | 2篇 |
综合类 | 1022篇 |
化学工业 | 3216篇 |
金属工艺 | 531篇 |
机械仪表 | 521篇 |
建筑科学 | 608篇 |
矿业工程 | 199篇 |
能源动力 | 731篇 |
轻工业 | 3555篇 |
水利工程 | 112篇 |
石油天然气 | 260篇 |
武器工业 | 92篇 |
无线电 | 1140篇 |
一般工业技术 | 2028篇 |
冶金工业 | 415篇 |
原子能技术 | 272篇 |
自动化技术 | 2172篇 |
出版年
2024年 | 131篇 |
2023年 | 528篇 |
2022年 | 661篇 |
2021年 | 779篇 |
2020年 | 715篇 |
2019年 | 644篇 |
2018年 | 595篇 |
2017年 | 616篇 |
2016年 | 592篇 |
2015年 | 661篇 |
2014年 | 895篇 |
2013年 | 1090篇 |
2012年 | 903篇 |
2011年 | 1082篇 |
2010年 | 705篇 |
2009年 | 723篇 |
2008年 | 708篇 |
2007年 | 802篇 |
2006年 | 665篇 |
2005年 | 582篇 |
2004年 | 502篇 |
2003年 | 436篇 |
2002年 | 338篇 |
2001年 | 256篇 |
2000年 | 236篇 |
1999年 | 241篇 |
1998年 | 179篇 |
1997年 | 126篇 |
1996年 | 139篇 |
1995年 | 124篇 |
1994年 | 96篇 |
1993年 | 79篇 |
1992年 | 61篇 |
1991年 | 49篇 |
1990年 | 41篇 |
1989年 | 21篇 |
1988年 | 29篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1961年 | 4篇 |
1959年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Ying Chen Shuichi Iwata Tetsuo Mohri 《稀有金属(英文版)》2006,25(5):437-440
Theoretical investigation of the phase equilibria of the Fe-Ni alloy has been performed by combining the FLAPW total energy calculations and the Cluster Variation Method through the Cluster Expansion Method. The calculations have proved the stabilization of the LIE phase at 1:3 stoichiometry, which is in agreement with the experimental result, and predicted the existence of L1 0 as a stable phase below 550 K; this L1 0 phase has been missing in the conventional phase diagram. The calculations are extended to the Fe-rich region that is characterized by a wide range phase separation and has drawn considerable attention because of the intriguing Invar property associated with a Fe concentration of 65%. To reveal the origin of the phase separation, a P-V curve in an entire concentration range is derived by the second derivative of free energy functional of the disordered phase with respect to the volume. The calculation confirmed that the phase separation is caused by the breakdown of the mechanical-stability criterion. The newly calculated phase separation line combined with the L1 0 and L12Eorder-disordered phase boundaries provides phase equilibria in the wider concentration range of the system. Furthermore, a coefficient of thermal expansion (CTE) is attempted by incorporating the thermal vibration effect through harmonic approximation of the Debye-Gruneisen model. The Invar behavior has been reproduced, and the origin of this anomalous volume change has been discussed. 相似文献
102.
BASKES M. I. 《金属学报(英文版)》1995,(Z1)
ATOMISTICSIMULATIONSFORNi/AlINTERMETALLICSBASKESM.I.(SandiaNationalLaboratories,Livermore,Califormia)Abstract:AlargenumberofE... 相似文献
103.
A statistical-thermodynamic model for binary nonstoichiometric A5B3 with D81-structure has been established on the basis of the grand canonical ensemble. In the model the average chemical potentials according to the composition and a new extra equation as a boundary condition are proposed for more accuracy and free experimental data calculations. The model can be used in any A5B3 type compounds with D81 structure. The establishment method of the statistical-thermodynamic model can be extended to other complicated structures. We apply the statistical-thermodynamic model to α-Nb5Si3 and the parameters used in the model are obtained from the first-principles' calculations. From these parameters the expression for the point defect concentrations as a function of compositions and temperatures is obtained by numeral calculations. The constitutional defects and thermal defects in α-Nb5Si3 are discussed. 相似文献
104.
105.
介孔材料化学改性研究进展 总被引:1,自引:0,他引:1
综述了介孔材料化学改性目的,改性原理以及改性方法。介孔材料的化学改性包括对材料骨架的修饰以及对孔道表面的功能化,介孔材料表面自由硅醇键、双羟基硅醇踺是化学改性的基础,利用疏水性物质改性可以提高材料的水热稳定性,引入催化活性组分可以提高催化性能,利用具有特定官能团的硅烷偶连剂改性,则能够实现特殊的目的。详述了化学改性方法,包括元素取代法、共价键移植法和有机硅烷偶连法。元素取代法是对分子筛骨架结构的修饰,共价键移植法是一种不引起孔道结构破坏且非常有效的骨架修饰方法,对介孔材料表面进行有机硅烷偶连剂法修饰改性主要有两种途径:即共沉淀法和后移植法。 相似文献
106.
Andrew J. Morris Rebecca J. Nicholls Chris J. Pickard Jonathan R. Yates 《Computer Physics Communications》2014
We present OptaDOS, a program for calculating core-electron and low-loss electron energy loss spectra (EELS) and optical spectra along with total-, projected- and joint-density of electronic states (DOS) from single-particle eigenenergies and dipole transition coefficients. Energy-loss spectroscopy is an important tool for probing bonding within a material. Interpreting these spectra can be aided by first principles calculations. The spectra are generated from the eigenenergies through integration over the Brillouin zone. An important feature of this code is that this integration is performed using a choice of adaptive or linear extrapolation broadening methods which we show produces higher accuracy spectra than standard fixed-width Gaussian broadening. OptaDOS may be straightforwardly interfaced to any electronic structure code. OptaDOS is freely available under the GNU General Public licence from http://www.optados.org. 相似文献
107.
Volumetric measurements were made on compressed solutions of carbon dioxide in n-decane and trans-decalin at 37.78°C at pressures up to 60 bar. The data were numerically analyzed to yield the isothermal compressibility function of the solutions at their saturation pressures. 相似文献
108.
《Expert systems with applications》2014,41(7):3343-3350
109.
Gang Yao William Yi Wang Chengxiong Zou Ke Ren Peixuan Li Xingyu Gao Deye Lin Jun Wang Shufeng Yang Yiguang Wang Haifeng Song Jinshan Li 《Journal of the American Ceramic Society》2022,105(6):4260-4276
High-entropy carbides (HECs) are regarded as potential candidate structural materials with attractive mechanical properties due to their ultra-high hardness. It is essential to reveal the atomic and electronic basis for strengthening mechanism in order to develop the advanced HECs. In the present work, C (M = Nb, Ti, V) are selected as case studies. The effects of transition metals (M) on the lattice parameters, bulk modulus, enthalpy of formation, electron work function (EWF), and bonding morphology/strength of HECs are comprehensively studied by first-principles calculations. It is found that the lattice parameters, equilibrium volumes, and bulk modulus of HECs are improved with the increase of M atomic volumes. The atomic-size differences among various groups of elements not only result in the lattice mismatch/distortion but also contribute to the formation of weak spots. In the view of bonding charge density, the electron redistributions caused by the coupling effect of the lattice distortion and valance electron differences can be revealed obviously, which identify the different bonding strength. Moreover, in terms of EWF, the proposed power-law-scaled hardness of HECs is validated and matches well with those reported theoretical and experimental results, providing a strategy to design advanced HECs with excellent mechanical properties. 相似文献
110.
Density functional theory is applied to predicting the structures and electrostatic potentials of planar electrochemical surfaces within the framework of the restricted primitive model where small ions are represented by charged hard spheres of equal diameter and the solvent is assumed to be a continuous dielectric medium. The hard-sphere contribution to the excess Helmholtz energy functional is evaluated using the modified fundamentalmeasure theory and the electrostatic contribution is obtained from the quadratic functional Taylor expansion using the second-order direct correlation function from the mean-spherical approximation. Numerical results for the ionic density profiles and the mean electrostatic potentials near a planar surface of various charge densities are in excellent agreement with molecular simulations. In contrast to the modified Gouy-Chapman theory, the present density functional theory correctly predicts the second layer formation and charge inversion of charged surfaces as observed in simulations and in experiments. The theory has also been tested with the zeta potentials of positively charged polystyrene particles in aqueous solutions of KBr. Good agreement is achieved between the calculated and experimental results. 相似文献