全文获取类型
收费全文 | 102537篇 |
免费 | 8078篇 |
国内免费 | 3930篇 |
专业分类
电工技术 | 5332篇 |
技术理论 | 14篇 |
综合类 | 6052篇 |
化学工业 | 17340篇 |
金属工艺 | 5082篇 |
机械仪表 | 5524篇 |
建筑科学 | 7026篇 |
矿业工程 | 2567篇 |
能源动力 | 3086篇 |
轻工业 | 7471篇 |
水利工程 | 1731篇 |
石油天然气 | 4627篇 |
武器工业 | 671篇 |
无线电 | 13482篇 |
一般工业技术 | 13373篇 |
冶金工业 | 6106篇 |
原子能技术 | 1101篇 |
自动化技术 | 13960篇 |
出版年
2024年 | 412篇 |
2023年 | 1602篇 |
2022年 | 2912篇 |
2021年 | 4022篇 |
2020年 | 3119篇 |
2019年 | 2546篇 |
2018年 | 2894篇 |
2017年 | 3027篇 |
2016年 | 2916篇 |
2015年 | 3705篇 |
2014年 | 4707篇 |
2013年 | 5951篇 |
2012年 | 6219篇 |
2011年 | 6947篇 |
2010年 | 5671篇 |
2009年 | 5541篇 |
2008年 | 5546篇 |
2007年 | 5132篇 |
2006年 | 4793篇 |
2005年 | 4078篇 |
2004年 | 3203篇 |
2003年 | 3058篇 |
2002年 | 3109篇 |
2001年 | 2712篇 |
2000年 | 2489篇 |
1999年 | 2700篇 |
1998年 | 2665篇 |
1997年 | 2074篇 |
1996年 | 1941篇 |
1995年 | 1605篇 |
1994年 | 1383篇 |
1993年 | 1019篇 |
1992年 | 788篇 |
1991年 | 607篇 |
1990年 | 562篇 |
1989年 | 501篇 |
1988年 | 388篇 |
1987年 | 305篇 |
1986年 | 237篇 |
1985年 | 204篇 |
1984年 | 166篇 |
1983年 | 115篇 |
1982年 | 122篇 |
1981年 | 91篇 |
1980年 | 115篇 |
1979年 | 61篇 |
1978年 | 66篇 |
1977年 | 67篇 |
1976年 | 89篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
陆洪智 《武汉理工大学学报(材料科学英文版)》2009,24(2):229-234
Tungsten trioxide micropheres were prepared by spray pyrolysis, and tungsten carbide microspheres were produced by spray pyrolysis-low
temperature reduction and carbonization technology. Multi-walled carbon nanotube-tungsten carbide composites were prepared
by the continuous reduction and carbonization process using multi-walled carbon nanotubes (MWCNTs) and WO3 precursor by molecular level mixing and calcination. The morphology and structure of the samples were characterized by scanning
electron microscope and transmission electron microscope. Furthermore, the crystal phase was identified by X-ray diffraction.
The electrocatalytic activity of the sample was analyzed by means of methanol oxidation. Tungsten carbide microspheres were
catalytic active for methanol oxidation reaction. Nevertheless tungsten trioxide microspheres and multi-walled carbon nanotube-tungsten
carbide composites were not catalytic active for methanol oxidation reaction. These results indicate that tungsten carbide
micropheres are promising catalyst for methanol oxidation. 相似文献
982.
郑立霞 《武汉理工大学学报(材料科学英文版)》2009,24(3):415-417
The deformation resistance effect of polyacrylonitrile (PAN)-based carbon fibers was investigated, and the variatipn law of
electrical resistivity under tensile stress was analyzed. The results show that the gauge factor (fractional change in resistance
per unit strain) of PAN-based carbon fibers is 1.38, which is lower than that of the commonly-used resistance strain gauge.
These may due to that the electrical resistivity of carbon fibers decreases under tensile stress. In addition when the carbon
fibers are stretched, the change of its resistance is caused by fiber physical dimension and the change of electric resistivity,
and mainly caused by the change of physical dimension. The mechanical properties of carbon fiber monofilament were also measured.
Funded by the National Natural Science Foundation of China (No. 10672128 and 50878170) 相似文献
983.
介绍了一种软质电容式车辆动态称重系统.对该传感器静态特性进行了研究,分析了受力面积和时间的影响,针对橡胶材料粘弹性特性,提出了利用四元件模型对其建模.同时进行了动态实验,车辆总重量的测量误差在10%以内,其精度优于ASTME1318-02给出的Ⅰ类WIM系统精度(置信95%时总重误差±10%).实验结果表明:利用文中提出的车辆动态称重系统进行测量是可行的,它有助于随时测量,便于交通稽查. 相似文献
984.
Ying-chieh Lee 《北京科技大学学报(英文版)》2009,16(1):124-127
The effect of SiO2 doping on the sintering behavior,microstructure,and dielectric properties of BaTiO3-based ceramics has been investigated.Silica was added to the BaTiO3-based powder prepared by the solid state method with 0.075mo1%,0.15mo1%,and 0.3mo1%,respectively.The SiO2-doped BaTiO3-based ceramic with high density and uniform grain size were obtained,which were sintered in reducing atmosphere.A scanning electron microscope,X-ray diffraction,and LCR meter were used to determine the microstructure as well as the dielectric properties.SiO2 can form a liquid phase belonging to the ternary system of BaO-TiO2-SiO2,leading to the formation of BaTiO3 ceramics with high density at a lower sintering temperature.The SiO2-doped BaTiO3-based ce-ramics can be sintered to a theoretical density higher than 95% at 1220℃ with a soaking time of 2 h.The dielectric constants of the sample with 0.15mo1% SiO2 addition sintered at 1220℃ is about 9000.Doping with a small amount of silica can improve the sinter-ing and dielectric properties of BaTiO3-based ceramics. 相似文献
985.
The full-range behavior of partially bonded, together with partially prestressed concrete beams containing fiber reinforced
polymer (FRP) tendons and stainless steel reinforcing bars was simulated using a simplified theoretical model. The model assumes
that a section in the beam has a trilinear moment—curvature relationship characterized by three particular points, initial
cracking of concrete, yielding of non-prestressed steel, and crushing of concrete or rupturing of prestressing tendons. Predictions
from the model were compared with the limited available test data, and a reasonable agreement was obtained. A detailed parametric
study of the behavior of the prestressed concrete beams with hybrid FRP and stainless steel reinforcements was conducted.
It can be concluded that the deformability of the beam can be enhanced by increasing the ultimate compressive strain of concrete,
unbonded length of tendon, percentage of compressive reinforcement and partial prestress ratio, and decreasing the effective
prestress in tendons, and increasing in ultimate compressive strain of concrete is the most efficient one. The deformability
of the beam is almost directly proportional to the concrete ultimate strain provided the failure mode is concrete crushing,
even though the concrete ultimate strain has less influence on the load-carrying capacity.
Foundation item: Project (50478502) supported by the National Natural Science Foundation of China 相似文献
986.
Failure mode and strength anisotropic characteristic of stratified rock mass under uniaxial compressive situation 总被引:1,自引:1,他引:0
A stratified rock mass model was founded by FLAC3D. The failure mode and anisotropic characteristic of strength for stratified rock mass were analyzed. The analysis results
show that the numerical simulation can visually reflect the failure modes of rock samples under different inclination angles
β of structural plane. The stiffness of rock sample before peak strength changes in the compressive procedure. With the increase
of β, the compressive strength σ
c of rock sample decreases firstly and then increases; when β is in the range of 20°–30° and 80°–90°, σ
c has the largest sensitivity to β; while β falls in the range of 30°–70°, σ
c varies little. When ϕ
j
<β<90° (β
j
is friction angle of structure plane), the results obtained from numerical simulation and theoretical analysis are in almost
the same values; while β⩽ ϕ
j
or β=90°, they are in great different values. The results obtained from theoretical analysis are obvious larger than those from
numerical simulation; and the results from numerical simulation can reflect the difference of compressive strength of rock
samples for the two situations of β⩾ ϕ
j
and β=90°, which is in more accordance with the real situation.
Foundation item: Project (50099620) supported by the National Natural Science Foundation of China 相似文献
987.
借助L-fuzzy映射和L-fuzzy集的像,给出了由L-fuzzy映射诱导的L-fuzzy闭包算子及其等价刻画.当L为有限分配格时,讨论了代数的L-fuzzy闭包算子及其所诱导的闭包系统的等价刻画. 相似文献
988.
大规模定制模式下,产品采用面向装配的设计有利于快速响应市场和降低产品成本.详细分析影响零件可装配性的因素,针对大规模定制模式下充分提高零件的可装配性,提出零件可装配性的评价指标体系和模糊综合评价模型.依据提出的评价模型,开发了零件可装配性评价系统,作为设计人员进行零件可装配性在线评价的工具. 相似文献
989.
在集群通信系统中,为了利用语音信道进行数据传输,设计了一种以64QAM作为调制方式的调制器.讲述了64QAM的原理,给出了系统设计的方框图和软件编程的流程,对调制器中几个重要的功能模块进行详细说明,最后利用DSP芯片通过软件编程进行实现. 相似文献
990.