全文获取类型
收费全文 | 1215篇 |
免费 | 54篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 63篇 |
综合类 | 1篇 |
化学工业 | 343篇 |
金属工艺 | 40篇 |
机械仪表 | 35篇 |
建筑科学 | 22篇 |
能源动力 | 67篇 |
轻工业 | 103篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 93篇 |
一般工业技术 | 230篇 |
冶金工业 | 130篇 |
原子能技术 | 38篇 |
自动化技术 | 119篇 |
出版年
2023年 | 11篇 |
2022年 | 46篇 |
2021年 | 62篇 |
2020年 | 29篇 |
2019年 | 32篇 |
2018年 | 37篇 |
2017年 | 25篇 |
2016年 | 46篇 |
2015年 | 25篇 |
2014年 | 51篇 |
2013年 | 84篇 |
2012年 | 57篇 |
2011年 | 91篇 |
2010年 | 59篇 |
2009年 | 56篇 |
2008年 | 61篇 |
2007年 | 38篇 |
2006年 | 37篇 |
2005年 | 40篇 |
2004年 | 25篇 |
2003年 | 31篇 |
2002年 | 28篇 |
2001年 | 20篇 |
2000年 | 17篇 |
1999年 | 27篇 |
1998年 | 45篇 |
1997年 | 34篇 |
1996年 | 29篇 |
1995年 | 17篇 |
1994年 | 23篇 |
1993年 | 15篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有1288条查询结果,搜索用时 15 毫秒
101.
102.
Single-wall carbon nanotubes were grown by thermal chemical vapor deposition using either boron- or nitrogen-containing feedstocks or both. Carrier doping was evidenced by hardenings of the G band in Raman spectra, and the estimated carrier concentration reached ∼0.4%. In the G′ and D band spectra, a doping-induced component was observed at the high- or low-energy side of the original one. However, the appearance of the new component did not always coincide with the carrier doping. The doped SWCNTs often show radial breathing mode peaks in the off-resonance region, indicating a defect-induced modification of absorption spectrum. 相似文献
103.
104.
Koichi DoiSatoshi Hino Hiroki MiyaokaTakayuki Ichikawa Yoshitsugu Kojima 《Journal of power sources》2011,196(1):504-507
A lithium silicon alloy was synthesized by mechanical alloying method. Hydrogen storage properties of this Li-Si-H system were studied. During hydrogenation of the lithium silicon alloy, lithium atom was extracted from the alloy and lithium hydride was generated. Equilibrium hydrogen pressures for desorption and absorption reactions were measured in a temperature range from 400 to 500 °C to investigate the thermodynamic characteristics of the system, which can reversibly store 5.4 mass% hydrogen with smaller reaction enthalpy than simple metal Li. Li absorbing alloys, which have been widely studied as a negative electrode material for Li ion rechargeable batteries, can be used as hydrogen storage materials with high hydrogen capacity. 相似文献
105.
In this investigation, a systematic procedure that can be used for modeling joint constraints for the absolute nodal coordinate
formulation is developed. To this end, the non-generalized intermediate coordinates are introduced to derive a mapping between
the generalized gradient coordinates and the non-generalized rotation parameters. With this mapping, a wide variety of joint
constraints can be defined for the absolute nodal coordinate formulation in terms of the non-generalized reference coordinates
and, therefore, existing well-developed constraint libraries formulated for the rigid body reference coordinates can be directly
employed without significant modifications in existing codes. Furthermore, in order to define a rigid surface at the joint
definition point, a set of orthonormality conditions is imposed on the gradient coordinates. This leads to not only accurate
modeling of interface to mechanical joint, but also a simpler definition of the joint coordinate system obtained by the orthonormal
gradient vectors. For this reason, a simpler form of constraint Jacobian and quadratic velocity vectors can be obtained as
compared to those of the existing approach which requires the use of highly nonlinear joint coordinate system. A systematic
procedure for eliminating the non-generalized coordinates and the dependent Lagrange multipliers associated with the coordinate
mapping equations from the equations of motion is presented. As a result, a standard augmented form of the equations of motion
can be obtained in terms of the generalized coordinates only. Several numerical examples are presented in order to demonstrate
the use of the joint constraint formulation developed in this investigation. 相似文献
106.
K Kajiwara E Sugaya N Yuyama H Nagasawa T Tsuda A Sugaya M Motoki K Shimizu-Nishikawa M Kimura 《Canadian Metallurgical Quarterly》1997,47(1-2):49-58
To determine the molecular mechanism of regulation of pentylenetetrazol (PTZ)-induced calcium entry by the seizure-related gene, PTZ-17, the role of the 3'-untranslated region (3'UTR) and also interaction between 3'UTR and intracellular factors were investigated. PTZ-induced calcium inward current in Xenopus oocytes injected with PTZ-17 RNA varied in magnitude among strains of mice: RNA derived from the DBA/2 mouse, which has a high susceptibility to convulsions, showed the largest current and that from the BALB/c mouse with a low susceptibility to convulsions showed no PTZ response. The sequence of 3'UTR showed alterations among mouse strains: 3'UTR of BALB/c showed a sequence alteration from T to G and that of DBA/2 showed a GTG insertion compared with that of B6. The 3'UTR also regulated the translation of chloramphenicol acetyltransferase (CAT) RNA depending on its sequence. A particular region within the 3'UTR demonstrated interaction with 60- and 47-kDa proteins. Sequence alterations in this region corresponded to disappearance or increase in PTZ-induced calcium entry. These findings suggest that a particular region within 3'UTR of the seizure-related gene, PTZ-17, is involved in PTZ-induced calcium entry via interaction between mRNA and specific RNA-binding proteins. 相似文献
107.
C. X. Wang N. Maeda M. Hiroki T. Tawara T. Makimoto T. Kobayahsi T. Enoki 《Journal of Electronic Materials》2005,34(4):361-364
AlGaN/GaN-based metal-insulator-semiconductor heterostructure field-effect transistors (MIS-HFETs) with Al2O3/Si3N4 bilayer as insulator have been investigated in detail, and compared with the conventional HFET and Si3N4-based MIS-HFET devices. Al2O3/Si3N4 bilayer-based MIS-HFETs exhibited much lower gate current leakage than conventional HFET and Si3N4-based MIS devices under reverse gate bias, and leakage as low as 1×10−11 A/mm at −15 V has been achieved in Al2O3/Si3N4-based MIS devices. By using ultrathin Al2O3/Si3N4 bilayer, very high maximum transconductance of more than 180 mS/mm with ultra-low gate leakage has been obtained in the MIS-HFET
device with gate length of 1.5 μm, a reduction less than 5% in maximum transconductance compared with the conventional HFET
device. This value was much smaller than the more than 30% reduction in the Si3N4-based MIS device, due to the employment of ultra-thin bilayer with large dielectric constant and the large conduction band
offset between Al2O3 and nitrides. This work demonstrates that Al2O3/Si3N4 bilayer insulator is a superior candidate for nitrides-based MIS-HFET devices. 相似文献
108.
Hiroki Minoda 《Thin solid films》2003,424(1):40-44
Step instabilities on Si(1 1 1) vicinal surface and Si(1 1 1) vicinal surface induced by Au adsorption were observed by reflection electron microscopy. On the Si(0 0 1) vicinal surface faceting of (0 0 1) surface due to surface reconstruction takes place and surface steps are bunching. The kinetics of mass transport of Si depends on the substrate temperature and steps are impermeable for Si adatoms at lower temperature and they are permeable at higher temperature. On the Si(1 1 1) vicinal surface the permeability of steps depends on the heating current direction. The steps are permeable for step-up current heating and are impermeable for step-down current heating. Above a critical coverage of Au (≈0.3 ML) steps are bunching irrespective of heating current direction and periodic array of extremely straight step bands is formed for the step-down current heating. 相似文献
109.
Hiroki Mori Yoshihiro Ohama Naohiro Fukumura Yoji Uno 《Electrical Engineering in Japan》2007,161(4):38-48
A forward‐propagation learning rule (FPL) has been proposed for a neural network (NN) to learn an inverse model of a controlled object. A feature of FPL is that the trajectory error propagates forward in NN and appropriate values of two learning parameters are required to be set. FPL has only been simulated to several kinds of controlled objects such as a two‐link arm in a horizontal plane. In this work, we applied FPL to AIBO and showed the validity of FPL on a real controlled object. At first, we tested a learning experiment of an inverse dynamic of a two‐link arm in a sagittal plane with viscosity and Coulomb friction by computer simulation. In this simulation, a low‐pass filter (LPF) was applied to realized trajectories because coulomb friction vibrates them. From the simulation results, we found that the learning process is stable by some adequate sets of the learning parameters although it is more sensitive to the values of the parameters owing to friction and gravity terms. Finally, we tested applying FPL to motor control of AIBO's leg. The inverse dynamics model was acquired by FPL with only about 150 learning iterations. From these results, the validity of the FPL was confirmed by the real robot control experiments. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(4): 38–48, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20456 相似文献
110.