全文获取类型
收费全文 | 362947篇 |
免费 | 83097篇 |
国内免费 | 53374篇 |
专业分类
电工技术 | 38842篇 |
技术理论 | 14篇 |
综合类 | 33034篇 |
化学工业 | 52733篇 |
金属工艺 | 33629篇 |
机械仪表 | 17695篇 |
建筑科学 | 26287篇 |
矿业工程 | 18165篇 |
能源动力 | 13468篇 |
轻工业 | 33816篇 |
水利工程 | 10701篇 |
石油天然气 | 22282篇 |
武器工业 | 5074篇 |
无线电 | 50731篇 |
一般工业技术 | 50641篇 |
冶金工业 | 15243篇 |
原子能技术 | 3248篇 |
自动化技术 | 73815篇 |
出版年
2024年 | 3610篇 |
2023年 | 7914篇 |
2022年 | 11700篇 |
2021年 | 14620篇 |
2020年 | 15143篇 |
2019年 | 22634篇 |
2018年 | 24666篇 |
2017年 | 26612篇 |
2016年 | 25582篇 |
2015年 | 26537篇 |
2014年 | 27289篇 |
2013年 | 28320篇 |
2012年 | 28635篇 |
2011年 | 25704篇 |
2010年 | 22586篇 |
2009年 | 19055篇 |
2008年 | 16785篇 |
2007年 | 15469篇 |
2006年 | 14557篇 |
2005年 | 12898篇 |
2004年 | 12841篇 |
2003年 | 10781篇 |
2002年 | 10083篇 |
2001年 | 8976篇 |
2000年 | 8286篇 |
1999年 | 8497篇 |
1998年 | 7309篇 |
1997年 | 6377篇 |
1996年 | 6021篇 |
1995年 | 5524篇 |
1994年 | 4561篇 |
1993年 | 3855篇 |
1992年 | 3550篇 |
1991年 | 2607篇 |
1990年 | 1995篇 |
1989年 | 1818篇 |
1988年 | 1392篇 |
1987年 | 548篇 |
1986年 | 478篇 |
1985年 | 328篇 |
1984年 | 245篇 |
1983年 | 179篇 |
1982年 | 228篇 |
1981年 | 209篇 |
1980年 | 161篇 |
1976年 | 253篇 |
1975年 | 220篇 |
1972年 | 238篇 |
1971年 | 129篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
A large quantity of laminated fine grain zones were observed in the Al-Mg-Li alloy weld metal by manual TIG, which was not found in ordinary Al alloy welds. The fine grain zone is formed because of the Al3(Zr,Ti) particles in the filler metal and the manual filling of filler metal in welding process 相似文献
112.
CA/PAN中空纤维血浆分离膜的结构与性能 总被引:4,自引:2,他引:2
本研究以CA及PAN的共混溶液,通过干-湿法纺丝制取中空纤维,利用共混高聚物各组分在凝固剂中相分离速度的差异,形成具有稳定结构的中空纤维孔膜,该膜用于分离血液中的血浆成分具有良好效果。讨论了成型条件及添加剂等对膜结构、性能的影响,用SEM及图相分析仪、MAP压汞仪及DSC等分析手段,对膜的微孔结构、形态、孔尺寸及中空纤维膜的血浆通量和水通量等进行了系统的考查。 相似文献
113.
114.
Moss C.D. Teixeira F.L. Yang Y.E. Jin Au Kong 《Geoscience and Remote Sensing, IEEE Transactions on》2002,40(1):178-186
A three-dimensional (3D) finite-difference time-domain (FDTD) scheme is introduced to model the scattering from objects in continuous random media. FDTD techniques have been previously applied to scattering from random rough surfaces and randomly placed objects in a homogeneous background, but little has been done to simulate continuous random media with embedded objects where volumetric scattering effects are important. In this work, Monte Carlo analysis is used in conjunction with FDTD to study the scattering from perfectly electrically conducting (PEC) objects embedded in continuous random media. The random medium models under consideration are chosen to be inhomogeneous soils with a spatially fluctuating random permittivities and prescribed correlation functions. The ability of frequency averaging techniques to discriminate objects in this scenarion is also briefly investigated. The simulation scheme described in this work can be adapted and used to help in interpreting the scattered field data from targets in random environments such as geophysical media, biological media, or atmospheric turbulence 相似文献
115.
换热器小浮头螺栓断裂失效分析 总被引:2,自引:0,他引:2
针对换热器小浮头螺栓发生断裂的情况进行失效分析,找出原因,提出处理措施及材质选择时应注意的问题。 相似文献
116.
Following up on recent studies of the Zn-rich corners of the Zn-Fe-Ni and Zn-Fe-Si ternary systems, a 450 °C isothermal section
of the Zn-Fe-Ni-Si quaternary phase diagram with the Zn composition being fixed at 93 at.% was determined experimentally using
optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS), and x-ray
diffractometry (XRD). FeSi was found to be in equilibrium with almost all phases in the section, including the T, ζ, Ni-δ,
NiSi2, and FeSi2 phases, as well as the liquid phase (L). Silicon solubilities in the T, ζ, and Ni-δ phases were rather limited. However,
the solubilities of Fe and Zn in the NiSi2 phase, at 4.5 at.% and 7.2 at.%, respectively, were appreciable. The existence of the (L+NiSi2+Ni-δ) three-phase equilibrium state apparently prevents other Ni-Si compounds from entering equilibrium with the liquid at
450 °C. No true quaternary compound was found in the study. 相似文献
117.
118.
119.
120.
Tatsuya Hanaoka Hisashi Ishitani Ryuji Matsuhashi Yoshikuni Yoshida 《Applied Energy》2002,72(3-4):705-721
The objective of this study is to evaluate the potential for recovering fluorocarbons as measures for the abatement of global warming. In this study, we focused on the three different kinds of fluorocarbons: CFCs, HCFCs and HFCs, and targeted refrigerant use because of the availability of relevant data. We first estimated future fluorocarbon emissions from the targeted appliances; we next compared those emissions in the units of CO2 equivalent to the level of CO2 emissions in 1990 from a quantitative point of view. As the result of this study, it was found that fluorocarbon emissions in 1999 and 2010 would be equal to approximately 7 and 3% of the level of CO2 emissions in 1990 respectively. Moreover, if we implement a 100% recovery rate in every recovery route, we can reduce a large amount of emissions which correspond to approximately 2–5% of the level of CO2 emissions in 1990, even if we take into account the energy-related CO2 emissions by the transportation and decomposition of fluorocarbons. 相似文献