全文获取类型
收费全文 | 92659篇 |
免费 | 6900篇 |
国内免费 | 4263篇 |
专业分类
电工技术 | 2143篇 |
技术理论 | 6篇 |
综合类 | 6709篇 |
化学工业 | 5384篇 |
金属工艺 | 25802篇 |
机械仪表 | 5202篇 |
建筑科学 | 17415篇 |
矿业工程 | 2766篇 |
能源动力 | 1836篇 |
轻工业 | 2123篇 |
水利工程 | 997篇 |
石油天然气 | 2549篇 |
武器工业 | 492篇 |
无线电 | 1233篇 |
一般工业技术 | 8807篇 |
冶金工业 | 18497篇 |
原子能技术 | 538篇 |
自动化技术 | 1323篇 |
出版年
2024年 | 240篇 |
2023年 | 939篇 |
2022年 | 2147篇 |
2021年 | 2502篇 |
2020年 | 2665篇 |
2019年 | 1907篇 |
2018年 | 1665篇 |
2017年 | 2607篇 |
2016年 | 2776篇 |
2015年 | 3106篇 |
2014年 | 5780篇 |
2013年 | 5117篇 |
2012年 | 6713篇 |
2011年 | 7646篇 |
2010年 | 5796篇 |
2009年 | 6028篇 |
2008年 | 4802篇 |
2007年 | 6308篇 |
2006年 | 5738篇 |
2005年 | 4782篇 |
2004年 | 4030篇 |
2003年 | 3506篇 |
2002年 | 3131篇 |
2001年 | 2649篇 |
2000年 | 2237篇 |
1999年 | 1724篇 |
1998年 | 1311篇 |
1997年 | 1284篇 |
1996年 | 1060篇 |
1995年 | 802篇 |
1994年 | 673篇 |
1993年 | 499篇 |
1992年 | 415篇 |
1991年 | 275篇 |
1990年 | 226篇 |
1989年 | 237篇 |
1988年 | 139篇 |
1987年 | 72篇 |
1986年 | 53篇 |
1985年 | 31篇 |
1984年 | 39篇 |
1983年 | 24篇 |
1982年 | 32篇 |
1981年 | 18篇 |
1980年 | 43篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Shuang Kuang) Yong-lin Kang) Hao Yu) Ren-dong Liu) ) School of Materials Science Engineering University of Science Technology Beijing Beijing China ) Technology Center Anshan Iron & Steel Group Corporation Anshan China 《北京科技大学学报(英文版)》2009,16(4):393-398
A more accurate estimation of stress-strain relationships for martensite and ferrite was developed, and the modified law of mixture was used to investigate the stress-strain partitioning of constituent phases in dual phase (DP) steels with two different martensite volume fractions. The results show that there exist great differences in the stress-strain contribution of martensite and ferrite to DP steel. The stress-strain partitioning coefficient is not constant in the whole strain range, but decreases with... 相似文献
952.
Effects of annealing temperature on the microstructure and properties of the 25Mn-3Si-3Al TWIP steel 总被引:3,自引:0,他引:3
Microstructures and mechanical properties of the 25Mn twinning induced plasticity (TWIP) steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 1000°C,the 25Mn steel showed ex-cellent comprehensive mechanical properties,the tensile strength was about 640 MPa,the yield strength was higher than 255 MPa,and the elongation was above 82%. The microstructure was analyzed by optical microscopy (OM),X-ray diffraction (XRD),and transmission electron... 相似文献
953.
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
954.
To understand the solidification behavior of austenitic stainless steel in rotary electromagnetic-field, the influence of
low-frequency rotary electromagnetic-field on solidification structure of austenitic stainless steel in horizontal continuous
casting was investigated based on industrial experiments. The results show that the solidification structure of austenitic
stainless steel can be remarkably refined, the central porosity and shrinkage cavity can be remarkably decreased, and the
equiaxed grains zone are enlarged by means of application of appropriate low-frequency electromagnetic-field parameters. The
industrial trials verify that the stirring intensity of austenitic stainless steel should be higher compared with that of
plain carbon steel. Electromagnetic stirring affects the macrostructure even if the average magnetic flux density of the electromagnetic
stirring reaches 90 mT (amplitude reaches 141 mT) with the frequency of 3–4 Hz. Due to a higher viscosity, rotating speed
of molten stainless steel is 20%–30% lower than that of molten carbon steel in the same magnetic flux density.
Foundation item: Project(CSTC2007BB4216) supported by the Natural Science Foundation of Chongqing, China 相似文献
955.
Ji-ping Chen) Yong-lin Kang ) Ying-min Hao) Guang-ming Liu) Ai-ming Xiong) ) School of Materials Science Engineering University of Science Technology Beijing Beijing China ) The State Key Laboratory for Advanced Metals Materials China ) Steel Research Institute of Shougang Beijing China 《北京科技大学学报(英文版)》2009,16(5):540-548
A Ti+Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the conventional austenite region and in the ferrite region with lubrication was experimentally studied.Subsequent cold rolling and continuous annealing processes were also conducted.The results show that microstructures of ultra-low carbon bake hardening hot strips at room temperature are basically irregular polygonal ferrites.The yield strength,ultimate tensile strength,n value,and r value of the No.2 specimen hot-rolled in the ferr... 相似文献
956.
CAO Wei LI Bing-wen GUO Chu'wen MAO Xin-yuan MA Qin-qin 《中国矿业大学学报(英文版)》2009,19(1):133-136
High-speed steel W18Cr4V is commonly used in industries such as blade and mould manufacturers because of its high level of hardness and toughness, red-hardness and resistance. Ion implantation is an effective method to improve the wear resis-tance of W18Cr4V. In our investigation, Ta and Ta+N ion implantation was performed on W18Cr4V high-speed steel. The surface properties after implantation were evaluated by measuring friction coefficients while the carbonyl phase of the surface was ana-lyzed by X-ray diffraction analysis. It was found that the friction coefficients of the treated samples were much lower. Samples implanted with Ta+N had a lower friction coefficients than samples implanted only with Ta. This can be attributed to the formation of a new chemical compound, Fe7Ta3, on both surfaces. An even harder chemical compound, Fe2N, was formed on both sttrfaces of Ta+N implanted samples. 相似文献
957.
方钢管混凝土柱-钢梁节点研究综述 总被引:1,自引:0,他引:1
方钢管混凝土柱--钢梁节点的结构性能直接影响钢管混凝土结构在建筑工程中推广和应用.为使设计人员对方钢管混凝土柱--钢梁节点有一个较为全面的了解,该文综合国内外相关资料,按刚接、半刚接、铰接三种节点类型,分别介绍目前常用节点的构造型式和受力特点,并简要介绍该节点研究现状.最后,对方钢管混凝土柱--钢梁节点的进一步研究工作做了探讨. 相似文献
958.
实际工程中的钢管都是有初始弯曲的,初始弯曲的存在会降低薄壁钢管混凝土柱的承载力.采用能量法对具有初始弯曲管壁的屈曲性能进行了分析,分析结果表明,初始弯曲的存在会使管壁的宽厚比降低30%左右. 相似文献
959.
通过对14根500 MPa细晶粒钢筋、1根400 MPa及1根600 MPa钢筋做箍筋的混凝土简支梁在集中荷载作用下的试验,观测了不同混凝土强度、不同剪跨比、不同箍筋强度、不同配箍率、不同截面尺寸条件下试件的裂缝、挠度、承载力及破坏形态;并将实测值与有关公式的计算值进行了比较.试验结果表明,构件的斜截面承载力仍可按现行《混凝土结构设计规范》的相关公式进行计算,并有足够的安全储备. 相似文献
960.
杨秀雷 《青岛建筑工程学院学报》2009,(2):135-138
随着钢结构的不断发展,钢结构在越来越多的领域得到了广泛的应用,其技术日益成熟.为了不断提高钢结构工程的制作技术,根据青岛开发区国际贸易中心钢结构的特点和设计要求,结合其制作过程中的加工工艺,介绍了超高层钢结构建筑主体——大型圆管柱在制作中的生产工艺和加工流程,重点阐述了圆管柱的制作、组装、焊接等方面的要点,提出了一些加工过程中的建议,对其他相同结构形式的钢结构建筑具有一定的借鉴作用. 相似文献