全文获取类型
收费全文 | 37794篇 |
免费 | 2996篇 |
国内免费 | 1745篇 |
专业分类
电工技术 | 2291篇 |
综合类 | 4131篇 |
化学工业 | 5937篇 |
金属工艺 | 2965篇 |
机械仪表 | 3555篇 |
建筑科学 | 3596篇 |
矿业工程 | 1563篇 |
能源动力 | 2594篇 |
轻工业 | 1418篇 |
水利工程 | 1033篇 |
石油天然气 | 2767篇 |
武器工业 | 173篇 |
无线电 | 1834篇 |
一般工业技术 | 4356篇 |
冶金工业 | 1725篇 |
原子能技术 | 442篇 |
自动化技术 | 2155篇 |
出版年
2024年 | 97篇 |
2023年 | 362篇 |
2022年 | 671篇 |
2021年 | 925篇 |
2020年 | 963篇 |
2019年 | 751篇 |
2018年 | 730篇 |
2017年 | 927篇 |
2016年 | 1106篇 |
2015年 | 1233篇 |
2014年 | 2203篇 |
2013年 | 2171篇 |
2012年 | 2807篇 |
2011年 | 2988篇 |
2010年 | 2164篇 |
2009年 | 2272篇 |
2008年 | 1982篇 |
2007年 | 2546篇 |
2006年 | 2413篇 |
2005年 | 2081篇 |
2004年 | 1833篇 |
2003年 | 1659篇 |
2002年 | 1381篇 |
2001年 | 1053篇 |
2000年 | 954篇 |
1999年 | 751篇 |
1998年 | 591篇 |
1997年 | 531篇 |
1996年 | 472篇 |
1995年 | 422篇 |
1994年 | 342篇 |
1993年 | 231篇 |
1992年 | 186篇 |
1991年 | 170篇 |
1990年 | 134篇 |
1989年 | 116篇 |
1988年 | 82篇 |
1987年 | 49篇 |
1986年 | 26篇 |
1985年 | 22篇 |
1984年 | 31篇 |
1983年 | 25篇 |
1982年 | 37篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 12篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1959年 | 3篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
11.
《Ceramics International》2020,46(10):16548-16555
In this article, NiFe2O4 nanoparticles (NPs) were prepared by co-precipitation method with subsequent thermal annealing leading to obtainment NPs with average sizes of 78 nm. Structure and magnetic analysis were performed by X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and vibrating sample magnetometry techniques. Stability of NiFe2O4 NPs was evaluated in PBS solution during 20 days. The toxicity of prepared NPs was evaluated in vitro using different cancer cell lines: HeLa (cervical cancer cell), PC-3 (prostate cancer cell). Fibroblasts like cells of L929 obtained from subcutaneous adipose tissue of mouse were used as normal cells. Results indicate successful synthesis of NiFe2O4 NPs that exhibit low cytotoxicity in concentration range from 1 to 100 μg/ml. Presented physical and biological results indicate the possibility of application investigated magnetic nanoparticles in hyperthermia, targeted drug delivery, magnetic resonance imaging or cell separation. 相似文献
12.
Li Lei Limin Li Shasha Wang Gaoyang Zhao Yoshifumi Oshima Yang Ren Lei Zhao Lihua Jin Yao Wang Chengshan Li Pingxiang Zhang 《Journal of the European Ceramic Society》2018,38(14):4694-4700
Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00?l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor. 相似文献
13.
《Journal of the European Ceramic Society》2020,40(12):3824-3828
Reactive hot pressing was utilized to synthesize and densify four ZrB2 ceramics with impurity contents low enough to avoid obscuring the effects of dopants on thermal properties. Nominally pure ZrB2 had a thermal conductivity of 141 ± 3 W/m K at 25 °C. Additions of 3 at% of Ti, Y, or Hf decreased the thermal conductivity by 20 %, 30 %, and 40 %, respectively. The thermal conductivity of (Zr,Hf)B2 was similar to ZrB2 synthesized from commercial powders containing the natural abundance of Hf as an impurity. This is the first study to demonstrate that Ti and Y additions decrease the thermal conductivity of ZrB2 ceramics and report intrinsic values for thermal conductivity and electrical resistivity of ZrB2 containing transition metal additions. Previous studies were unable to detect these effects because the natural abundance of Hf present masked the effects of these additions. 相似文献
14.
本文分析了燃气热水器行业针对无回水管水路系统实现零冷水功能的现有技术方案,指出现有技术方案存在的一些缺陷,并结合试验研究,对无回水管水路系统提出了一套全新的实现零冷水功能的技术解决方案。 相似文献
15.
This paper deals with the investigation of the effect of hygrothermal conditions on the bending of nanoplates using Levy type solution model employing the state-space concept. The nanoplates are assumed to be subjected to a hygrothermal environment. The two-unknown function plate theory is used to derive the governing differential equations on the basis of Eringen's nonlocal elasticity theory. The governing equations contain the small scale effect as well as hygrothermal and mechanical effects. These equations are converted into a set of first-order linear ordinary differential equations with constant coefficients. Analytical solution of bending response for nanoplates under combinations of simply supported, clamped and free boundary conditions is obtained. Comparison of the results with those being in the open literature is made. The influences played by small scale parameter, temperature rise, the degree of moisture concentration, boundary conditions, plate aspect ratio and side-to-thickness ratio are studied. 相似文献
16.
江苏油田的部分油井存在油管短路、地层高压低渗、漏失严重等问题,这些问题造成压井作业困难,并且压井作业过程中的井控与环境污染风险较大。为了进行不压井检泵作业,同时缩短检泵之后的产量恢复周期,进行了不压井作业技术研究,并研制了不压井作业装置。为解决起下抽油杆过程中的防喷问题,改进了抽油泵底阀结构,该结构可实现起下抽油杆过程中油管不带压、无溢流,并保障起下油管过程中的井控安全。该技术在江苏油田现场应用9井次,效果良好。 相似文献
17.
宁东供水工程供水水泵共有卧式和立式离心泵2种方案可供选择,也是工程论证时争论的焦点,经综合比较及主机设备的国际招标,最终确定了奥地利安德里兹公司的卧式双吸中开式离心泵为宁东供水工程的供水水泵。 相似文献
18.
19.
Nd:YVO4/KTP全固化倍频激光器的研究 总被引:2,自引:2,他引:0
介绍了两种腔型结构不同的Nd:YVO4/KTP全固化倍频绿光激光器,对腔结构参数进行了优化计算;在相同的实验条件下,对这两种腔的输出和稳定性等特性进行了比较和深入分析,在此基础上得出结论,提出改进措施。该折叠腔方案已进入产品化阶段。 相似文献
20.
迷宫螺旋泵和密封工作特性研究 总被引:1,自引:1,他引:0
介绍了一种实测迷宫螺旋泵和密封工作特性的实验方法,通过该方法可以测得迷宫螺旋泵的泵送特性曲线、迷宫螺旋端面组合密封的最大密封压力以及端面开启的开始转速,具有一定的实用价值。 相似文献