全文获取类型
收费全文 | 706篇 |
免费 | 29篇 |
国内免费 | 114篇 |
专业分类
电工技术 | 12篇 |
综合类 | 43篇 |
化学工业 | 36篇 |
金属工艺 | 45篇 |
机械仪表 | 20篇 |
建筑科学 | 6篇 |
矿业工程 | 19篇 |
能源动力 | 24篇 |
轻工业 | 7篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
武器工业 | 2篇 |
无线电 | 331篇 |
一般工业技术 | 173篇 |
冶金工业 | 32篇 |
原子能技术 | 68篇 |
自动化技术 | 28篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 28篇 |
2016年 | 23篇 |
2015年 | 30篇 |
2014年 | 28篇 |
2013年 | 40篇 |
2012年 | 60篇 |
2011年 | 71篇 |
2010年 | 43篇 |
2009年 | 41篇 |
2008年 | 46篇 |
2007年 | 33篇 |
2006年 | 46篇 |
2005年 | 31篇 |
2004年 | 36篇 |
2003年 | 22篇 |
2002年 | 38篇 |
2001年 | 30篇 |
2000年 | 40篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 16篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1974年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有849条查询结果,搜索用时 78 毫秒
91.
为满足钎焊原理和条件的要求,选用软钎焊封接工艺,对锗窗口进行了金属化处理。对金属化材料与焊料的选择、配制以及钎焊等工艺做了大量的探索与实验,并取得了有用的结果。该工艺技术已应用于制作红外探测器件。 相似文献
92.
Epitaxial (100) CdTe and ZnTe layers with high crystalline quality have been grown on Si substrates by atmospheric pressure
organometallic vapor phase epitaxy (OMVPE). A thin Ge interfacial layer grown at low temperature was used as a buffer layer
prior to ZnTe and CdTe growth. The layers were characterized by Nomarski optical microscopy and double crystal x-ray diffraction.
Double crystal rocking curves with full width at half maximum of about 110 and 250 arc-sec have been obtained for a 7 μm thick
ZnTe layer and a 4 μm thick CdTe layer, respectively. The results presented demonstrate a novel method ofin-situ Si cleaning step without a high temperature deoxidation process to grow high quality CdTe and ZnTe on Si in a single OMVPE
reactor. 相似文献
93.
H. Fathollahnejad R. Rajesh J. Liu R. Droopad G. N. Maracas R. W. Carpenter 《Journal of Electronic Materials》1995,24(1):35-38
A low resistance PdGe nonalloyed ohmic contact has been successfully formed to epitaxially lifted-off n-type GaAs films. The
contact is made by lifting off partially metallized n-type GaAs films using the epitaxial lift-off method and bonding them
to metallized Si substrates by natural intermolecular Van Der Waals forces. Low temperature sintering (200°C) of this contact
results in metallurgical bonding and formation of the ohmic contact. We have measured specific contact resistances of 5 ×
10−5 Ω-cm2 which is almost half the value obtained for pure Pd contacts. Germanium forms a degenerately doped heterojunction interfacial
layer to GaAs. Our experimental results show that germanium diffuses to the interface and acts as a dopant layer to n-GaAs
film surface. Therefore, for epitaxially lifted-off n-type GaAs films, PdGe is a low resistance ohmic metal contact to use. 相似文献
94.
低本底反康普顿高纯锗γ谱仪 总被引:2,自引:1,他引:1
本文介绍的谱仪采用铅-石蜡-铅为主的复合物质屏蔽。HPGe探测器对~(60)Co的1332keV γ射线的相对效率为25%,能量分辨率好于1.75keV。在阱型反符合屏蔽下,系统对放在HPGe端面的~(137)Cs点状薄膜源的峰康比可达800:1;测量时间1000min,置信度95%时,对~(137)Cs点源探测灵敏度好于5.6mBq;谱议在100—2000keV能区内的积分本底好于8.7±0.1次/min,与无反符合屏蔽时相比,压缩倍数为6.6。 相似文献
95.
The epitaxial growth and characterization of in-situ germanium and boron (Ge/B) doped Si epitaxial films is described. As
indicated by secondary ion mass spectroscopy and spreading resistance measurements, the total and electrically activated B
concentrations are essentially identical and independent of Ge incorporation. The B and Ge concentrations are uniformly distributed
in these Ge/B doped films. A slight enhancement of Hall mobility is obtained, possibly due to the stress relief induced by
Ge counterdoping. Carrier conduction in these films is due to the activated B with an activation energy of 0.04 eV as revealed
by conductivity versus temperature measurements. Ge atoms appear to be isoelectronic with Si atoms in these films. A slight
degradation of minority carrier diffusion length is observed. Electrical characterization of PN diodes on these Ge/B doped
films do not reveal any anomaly. SiO2 on these Ge/B doped films has similar oxide fixed charge density, interface state density and dielectric breakdown strength
compared to silicon dioxide on boron doped epitaxial films. Electron injection reveals a different transport mechanism of
the SiO2 grown on these Ge/B doped films. 相似文献
96.
曾燕芬 《核电子学与探测技术》1994,(4)
本文介绍了由于核污染产生的环境放射性样品的采集和制备方法,还介绍了所使用的微机多道分析系统,然后阐述了γ谱测量技术,给出了对污染样品的核素分析实例。 相似文献
97.
综述了对自组装量子点形态和生长过程所做的探讨和研究。介绍了关于量子点成核和形态的热力学理论、量子点生长过程的计算机模拟及Ge/Si(001)和InAs/GaAs(001)量子点生长和形态的实验观察。鉴于InAs/GaAs(001)体系的复杂性,把对InAs量子点的观察和研究分为"微观"和"宏观"两种。微观研究对象包括量子点原子尺度上的结构、量子点表面小晶面的晶体学的精确取向等,这些性质可能受热运动的影响比较大,在一定程度上是随机的,它们代表了量子点生长行为的复杂性;宏观研究的对象是指量子点密度、纳米尺度形态等大量粒子统计意义上的集体行为,这些性质和行为可能更具有实际意义。因此作者认为,目前研究量子点生长和形态更为有效的方法应该是探寻以量子点宏观行为所表征的简单性。重点介绍中科院半导体所半导体材料重点实验室最近所做的对InAs/GaAs(001)量子点生长过程的实验观察。结果表明,在一般生长条件下(富As,500℃,0.1ML/s),InAs量子点成核和生长应该都是连续的,没有经历被普遍认为的不连续(一级)相变。按照作者的观察,把InAs量子点成核看作是连续(二级)相变更为贴切。 相似文献
98.
N. Michel 《Computer Physics Communications》2007,176(3):232-249
A new algorithm to calculate Coulomb wave functions with all of its arguments complex is proposed. For that purpose, standard methods such as continued fractions and power/asymptotic series are combined with direct integrations of the Schrödinger equation in order to provide very stable calculations, even for large values of |η| or |ℑ(?)|. Moreover, a simple analytic continuation for is introduced, so that this zone of the complex z-plane does not pose any problem. This code is particularly well suited for low-energy calculations and the calculation of resonances with extremely small widths. Numerical instabilities appear, however, when both |η| and |ℑ(?)| are large and comparable or smaller than |ℑ(?)|.
Program summary
Title of program: cwfcomplexCatalogue number:ADYO_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADYO_v1_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandLicensing provisions: noneComputers on which the program has been tested: DELL GX400Operating systems: Linux, WindowsProgramming language used: C++No. of bits in a word: 64No. of processors used: 1Has the code been vectorized?: noNo. of bytes in distributed program, including test data, etc.: 33 092No. of lines in distributed program, including test data, etc.: 3210Distribution format:tar.gzNature of physical problem: The calculation of Coulomb wave functions with all of their arguments complex is revisited. The new methods introduced allow to greatly augment the range of accessible ?, η, and z.Method of solution: Power/asymptotic series and continued fractions are supplemented with direct integrations of the Coulomb Schrödinger equation. Analytic continuation for is also precisely computed using linear combinations of the functions provided by standard methods, which do not follow the branch cut requirements demanded for Coulomb wave functions.Typical running time: N/AUnusual features of the program: none 相似文献99.
We present a suite of programs to determine the ground state of the time-independent Gross-Pitaevskii equation, used in the simulation of Bose-Einstein condensates. The calculation is based on the Optimal Damping Algorithm, ensuring a fast convergence to the true ground state. Versions are given for the one-, two-, and three-dimensional equation, using either a spectral method, well suited for harmonic trapping potentials, or a spatial grid.
Program summary
Program title: GPODACatalogue identifier: ADZN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZN_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 5339No. of bytes in distributed program, including test data, etc.: 19 426Distribution format: tar.gzProgramming language: Fortran 90Computer: ANY (Compilers under which the program has been tested: Absoft Pro Fortran, The Portland Group Fortran 90/95 compiler, Intel Fortran Compiler)RAM: From <1 MB in 1D to ∼102 MB for a large 3D gridClassification: 2.7, 4.9External routines: LAPACK, BLAS, DFFTPACKNature of problem: The order parameter (or wave function) of a Bose-Einstein condensate (BEC) is obtained, in a mean field approximation, by the Gross-Pitaevskii equation (GPE) [F. Dalfovo, S. Giorgini, L.P. Pitaevskii, S. Stringari, Rev. Mod. Phys. 71 (1999) 463]. The GPE is a nonlinear Schrödinger-like equation, including here a confining potential. The stationary state of a BEC is obtained by finding the ground state of the time-independent GPE, i.e., the order parameter that minimizes the energy. In addition to the standard three-dimensional GPE, tight traps can lead to effective two- or even one-dimensional BECs, so the 2D and 1D GPEs are also considered.Solution method: The ground state of the time-independent of the GPE is calculated using the Optimal Damping Algorithm [E. Cancès, C. Le Bris, Int. J. Quantum Chem. 79 (2000) 82]. Two sets of programs are given, using either a spectral representation of the order parameter [C.M. Dion, E. Cancès, Phys. Rev. E 67 (2003) 046706], suitable for a (quasi) harmonic trapping potential, or by discretizing the order parameter on a spatial grid.Running time: From seconds in 1D to a few hours for large 3D grids 相似文献100.
As a first step towards developing heterostructures such as GaAs/Ge/Si entirely by chemical vapor deposition, Ge films have
been deposited on (100) Si by the pyrolysis of GeH4. The best films are grown at 700° C and are planar and specular, with RBS minimum channeling yields of ≈4.0% (near the theoretical
value) and defect densities of 1.3 x 108 cm−2. Variations of in-situ cleaning conditions, which affect the nature of the Si substrate surface, greatly affect the ability
to get good epitaxial growth at 700° C. The majority of the defects found in the Ge films are extrinsic stacking faults, formed
by dissociation of misfit and thermal expansion accommodation dislocations. The stacking fault density is not significantly
reduced by post-deposition annealing, as is the case for the dislocations observed in MBE Ge films. It is suggested that lowering
the CVD growth temperature through the use of high vacuum deposition equipment would result in dislocation defects like those
of MBE films which could then be annealed more effectively than stacking faults. Films with defect densities equivalent to
MBE Ge films (~2 x 107 cm−2) could then probably be produced. 相似文献