全文获取类型
收费全文 | 25348篇 |
免费 | 1935篇 |
国内免费 | 867篇 |
专业分类
电工技术 | 1337篇 |
技术理论 | 1篇 |
综合类 | 1385篇 |
化学工业 | 4517篇 |
金属工艺 | 1323篇 |
机械仪表 | 1338篇 |
建筑科学 | 1873篇 |
矿业工程 | 581篇 |
能源动力 | 885篇 |
轻工业 | 1647篇 |
水利工程 | 339篇 |
石油天然气 | 1349篇 |
武器工业 | 118篇 |
无线电 | 3117篇 |
一般工业技术 | 3247篇 |
冶金工业 | 1441篇 |
原子能技术 | 315篇 |
自动化技术 | 3337篇 |
出版年
2024年 | 85篇 |
2023年 | 409篇 |
2022年 | 707篇 |
2021年 | 1036篇 |
2020年 | 727篇 |
2019年 | 676篇 |
2018年 | 694篇 |
2017年 | 812篇 |
2016年 | 764篇 |
2015年 | 929篇 |
2014年 | 1248篇 |
2013年 | 1588篇 |
2012年 | 1580篇 |
2011年 | 1732篇 |
2010年 | 1405篇 |
2009年 | 1444篇 |
2008年 | 1349篇 |
2007年 | 1240篇 |
2006年 | 1351篇 |
2005年 | 1171篇 |
2004年 | 843篇 |
2003年 | 760篇 |
2002年 | 767篇 |
2001年 | 547篇 |
2000年 | 532篇 |
1999年 | 614篇 |
1998年 | 577篇 |
1997年 | 469篇 |
1996年 | 448篇 |
1995年 | 349篇 |
1994年 | 281篇 |
1993年 | 190篇 |
1992年 | 177篇 |
1991年 | 122篇 |
1990年 | 92篇 |
1989年 | 73篇 |
1988年 | 89篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 25篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
郭惠玲 《武汉理工大学学报(材料科学英文版)》2018,33(3):559-565
A facile approach has been developed to synthesize Fe3O4@PAM (polyacrylamide) nanoparticles (NPs) with carboxyl groups on the surfaces by copolymerization with acrylamide and acrylic acid in Fe3O4 NPs aqueous suspension. Nitrilotriacetic acid (NTA) was conjugated to the magnetic NPs via well-known carboniimide chemistry using EDC and NHS. The Ni2+ ions loaded on the surface of NPs provide abundant docking sites for immobilization of His-tagged green fluorescent proteins (His-tagged GFP). The high magnetic property of Fe3O4@PAM@NTA-Ni2+ allows an easy separation of the NPs from solution under an external magnetic field, with high His-tagged protein binding capacity (42 μg protein/mg of NPs). The NPs can be recycled for at least four times without significant loss of binding capacity to proteins. These materials show great potential to separate His-tagged protein with low-cost purification at industrial scale. 相似文献
84.
85.
86.
刘苏 《西安建筑科技大学学报(自然科学版)》1990,(3)
本文是应用仿射对应原理,以椭圆曲线上4个点及其中心,求作椭圆的方法。以及用此方法解决某些一般形式的二次曲面中的一些几何作图问题。 相似文献
87.
Suárez-Orozco Carola; Gaytán Francisco X.; Bang Hee Jin; Pakes Juliana; O'Connor Erin; Rhodes Jean 《Canadian Metallurgical Quarterly》2010,46(3):602
Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve analysis revealed that although some newcomer students performed at high or improving levels over time, others showed diminishing performance. Multinomial logistic regressions identified significant group differences in academic trajectories, particularly between the high-achieving youth and the other groups. In keeping with ecological–developmental and stage–environment fit theories, School Characteristics (school segregation rate, school poverty rate, and student perceptions of school violence), Family Characteristics (maternal education, parental employment, and household structure), and Individual Characteristics (academic English proficiency, academic engagement, psychological symptoms, gender, and 2 age-related risk factors, number of school transitions and being overaged for grade placement) were associated with different trajectories of academic performance. A series of case studies triangulate many of the quantitative findings as well as illuminate patterns that were not detected in the quantitative data. Thus, the mixed-methods approach sheds light on the cumulative developmental challenges that immigrant students face as they adjust to their new educational settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
The distribution of neutrons produced by the reaction of 50MeV/u ^12C-ion on a thick Cu target are studied.The neutrons are measured with threshold activation detectors.Al.F,C,Al and In activation samples were used to measure neutrons with energy greater than 7,11,20,50MeV and thermal neutrons,respectively,The fluence rate,energy and angular distributions of neutrons,total neutron yield of 12C-ion and the emission rate in the forward direction of neutrons over 11 and 20MeV were obtained. 相似文献
89.
90.
将图像融合以及高精度测量方法应用于天文图像处理,对图片进行处理得到有效点扩散函数,并将有效点扩散函数拟合星像,得到星体的位置与光度信息.结果表明, 方向平均定位精度为0.036 pixel,Y方向平均定位精度为0.O44 pixel,平均测光精度达到0.032 magnitude,测量结果验证了该算法的有效性. 相似文献