全文获取类型
收费全文 | 81914篇 |
免费 | 7554篇 |
国内免费 | 3774篇 |
专业分类
电工技术 | 4143篇 |
技术理论 | 4篇 |
综合类 | 5205篇 |
化学工业 | 17685篇 |
金属工艺 | 2173篇 |
机械仪表 | 3003篇 |
建筑科学 | 5754篇 |
矿业工程 | 6373篇 |
能源动力 | 6234篇 |
轻工业 | 6794篇 |
水利工程 | 793篇 |
石油天然气 | 18705篇 |
武器工业 | 419篇 |
无线电 | 2662篇 |
一般工业技术 | 4732篇 |
冶金工业 | 3661篇 |
原子能技术 | 970篇 |
自动化技术 | 3932篇 |
出版年
2024年 | 301篇 |
2023年 | 1152篇 |
2022年 | 2234篇 |
2021年 | 2964篇 |
2020年 | 3010篇 |
2019年 | 2557篇 |
2018年 | 2237篇 |
2017年 | 2356篇 |
2016年 | 2966篇 |
2015年 | 2904篇 |
2014年 | 4921篇 |
2013年 | 4906篇 |
2012年 | 6297篇 |
2011年 | 6299篇 |
2010年 | 4368篇 |
2009年 | 4361篇 |
2008年 | 3727篇 |
2007年 | 4734篇 |
2006年 | 4947篇 |
2005年 | 4163篇 |
2004年 | 3478篇 |
2003年 | 3112篇 |
2002年 | 2575篇 |
2001年 | 2388篇 |
2000年 | 2062篇 |
1999年 | 1651篇 |
1998年 | 1247篇 |
1997年 | 1071篇 |
1996年 | 885篇 |
1995年 | 714篇 |
1994年 | 590篇 |
1993年 | 445篇 |
1992年 | 355篇 |
1991年 | 287篇 |
1990年 | 233篇 |
1989年 | 204篇 |
1988年 | 83篇 |
1987年 | 75篇 |
1986年 | 59篇 |
1985年 | 51篇 |
1984年 | 45篇 |
1983年 | 26篇 |
1982年 | 28篇 |
1981年 | 62篇 |
1980年 | 43篇 |
1979年 | 8篇 |
1977年 | 7篇 |
1973年 | 5篇 |
1959年 | 7篇 |
1951年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Resin adsorption technique with XAD-8 and XAD-4 was used to characterize the raw water from Erlong reservoir in Jilin province of China. The NOM chemical composition sequences of four organic fractions in the raw water,from high to low,are fulvic acid (FA) fraction,hydrophilic non-acid (HPINA) fraction,hydrophilic acid (HPIA) fraction,and humic acid (HA) fraction. Experimental results show that FA is the main precursor of THMFP among the four organic fractions. However,HA or hydrophobic acid exhibits the highest chlorination activity in forming THMs. It is also found that the value of FI/DOC or SUVA and the specific THMFP have better positive correlation. It is implied that certain source water has unique nature of NOM and DBPs. 相似文献
72.
赵蕴林 《四川轻化工学院学报》2010,(3):369-372
文章结合工程设计经验对自贡地区的高层建筑在选用天然筏板基础的设计过程中,对高层建筑基础设计中涉及到的重要的地基沉降计算、结构设计和地下水等有关问题的处理进行了具体分析,对在一般高层建筑中采用天然筏板基础的实用性和可行性从设计和施工两个方面进行了相关的工程探讨。 相似文献
73.
针对低雷诺数的气液交叉流气体净化过程,提出有效避免二次雾沫夹带的液柱流体力学条件。数值模拟结果表明,液柱表面随着离开孔口的距离而变化,采用公式Lb/d=2.84We^0.694能有效预测液柱的断裂行为。 相似文献
74.
对再生丁基橡胶(RIIR)与非极性不饱和橡胶共混物的性能进行了研究。结果表明,RIIR易以填料的形式加入到非极性不饱和橡胶中使用,当RIIR以填料的形式加入到NR、BR及SBR中时,不仅使它们的耐热氧老化性及耐屈挠龟裂性得到明显改善,而且使NR及BR的撕裂强度及扯断伸长率提高;RIIR作为生胶与BR及NR共混,可改善BR的耐热氧老化性,提高NR的撕裂强度;SBR与RIIR共混,均使拉伸强度及撕裂强度降低;非极性不饱和二烯类橡胶与RIIR共混后,均使耐磨性降低。 相似文献
75.
钯-银合金膜分离氢气的研究 总被引:1,自引:0,他引:1
采用厚为50μm的Pd/Ag(23)合金膜进行了氢气渗透系数的测定和H_2/N_2混和气分离的研究,得出温度、压力、膜厚、进料气流量、膜的预处理和再活化及膜表面中毒等因素对氢气渗透的影响。分离H_2/N_2混和气可获得高纯氢气。 相似文献
76.
Due to huge calculation of SAR echo simulation of a three-dimensional (3D) ground scene, a fast simulation method is proposed. First, the data of a 3D ground scene are fractionally interpolated based on the Fractional Brownian Motion (FBM) model. Second, the data interpolated are divided into lots of small facets whose precision meets the simulation requirement, the backscattering coefficients of the small facets are calculated. Third, the shaded area is judged by the comparison method of overlook angles. Three parallel levels are analyzed and the kernel function is designed. Finally, the computing method of reduction adding and external thread are also utilized under the framework of GPU in order to get high efficiency. With the methods mentioned above, the imaging result of experimental DEM data verifies the validity and superiority of the proposed method. 相似文献
77.
根据普光气田现场资料,分析普光气田关井压降恢复时间和稳定生产时间的关系。建立邻井干扰计算模型,评价邻井干扰压降值及邻井干扰,并对邻井干扰规律进行敏感性分析。 相似文献
78.
79.
Butt joints between Mg alloy AZ31 B and pure Al 1 060 sheets were produced via metal inert gas welding process with Zn-Cd alloy foil. Crack-free Al/Mg butt joints between AZ31 B Mg alloy and pure Al 1060 sheets were obtained. Intermetallic compound layer 1 and layer 2 had formed in fusion zone/Mg alloy and the average thickness of the layer 1 was about 50 μm. The intermetallic compound layer 1 consisted of Al12Mg17 and Mg2Si phases while layer 2 consisted of Al12Mg17, Mg2Si and Mg Zn2 phases. The crack started from the IMC layer at the bottom of the joint and propagated along the brittle IMC layer, then expanded into weld metal during the SEM in situ tensile test. The highest tensile strength of the dissimilar metal butt joints could reach 46.8 MPa and the effect ofinterfacial IMC layer on mechanical property of the joint was discussed in detail in the present study. 相似文献
80.
An experimental study of the gas-dynamic aspects of the high-velocity oxyfuel (HVOF) thermal spray process has been performed
using commercially available HVOF equipment (Hobart-Tafa JP-5000, Ho-bart-Tafa Technologies, Inc., Concord, NH). Optical diagnostic
techniques, including microsecond-expo-sure schlieren and shadowgraph imaging, were applied to visualize the hot supersonic
jet produced by this equipment without particle injection. Rapid turbulent mixing of the jet with the surrounding atmos-phere
was observed, which is an issue of concern in coating quality due to the possibility of oxidation of sprayed particles. This
mixing appears to be a function of the ratio of densities of the hot jet and the cold atmosphere as well as a function of
the velocity of the jet, rather than one of combustion-chamber pres-sure or barrel length. The supersonic core of the HVOF
jet dissipates rapidly due to the mixing, so that the jet is no longer supersonic when it impinges on the target surface being
sprayed. Secondary issues also observed in this study include strong jet-noise radiation from the HVOF plume and the entrainment
and induced bulk motion of the surrounding air. 相似文献