全文获取类型
收费全文 | 617878篇 |
免费 | 72161篇 |
国内免费 | 46041篇 |
专业分类
电工技术 | 53438篇 |
技术理论 | 7篇 |
综合类 | 64787篇 |
化学工业 | 80186篇 |
金属工艺 | 41805篇 |
机械仪表 | 44145篇 |
建筑科学 | 48651篇 |
矿业工程 | 25965篇 |
能源动力 | 16427篇 |
轻工业 | 61730篇 |
水利工程 | 20016篇 |
石油天然气 | 24558篇 |
武器工业 | 9553篇 |
无线电 | 65569篇 |
一般工业技术 | 53665篇 |
冶金工业 | 24779篇 |
原子能技术 | 9677篇 |
自动化技术 | 91122篇 |
出版年
2024年 | 1629篇 |
2023年 | 9576篇 |
2022年 | 22764篇 |
2021年 | 29717篇 |
2020年 | 21661篇 |
2019年 | 15465篇 |
2018年 | 16541篇 |
2017年 | 18968篇 |
2016年 | 16824篇 |
2015年 | 26989篇 |
2014年 | 34194篇 |
2013年 | 40025篇 |
2012年 | 50525篇 |
2011年 | 52895篇 |
2010年 | 50161篇 |
2009年 | 47628篇 |
2008年 | 49133篇 |
2007年 | 47894篇 |
2006年 | 41728篇 |
2005年 | 34225篇 |
2004年 | 24315篇 |
2003年 | 16581篇 |
2002年 | 15399篇 |
2001年 | 14130篇 |
2000年 | 11789篇 |
1999年 | 6182篇 |
1998年 | 3399篇 |
1997年 | 2814篇 |
1996年 | 2508篇 |
1995年 | 2199篇 |
1994年 | 1702篇 |
1993年 | 1350篇 |
1992年 | 1112篇 |
1991年 | 808篇 |
1990年 | 656篇 |
1989年 | 618篇 |
1988年 | 447篇 |
1987年 | 280篇 |
1986年 | 221篇 |
1985年 | 110篇 |
1984年 | 87篇 |
1983年 | 61篇 |
1982年 | 74篇 |
1981年 | 87篇 |
1980年 | 177篇 |
1979年 | 119篇 |
1965年 | 16篇 |
1964年 | 10篇 |
1959年 | 109篇 |
1951年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The exosome-mediated response can promote or restrain the diseases by regulating the intracellular pathways, making the exosome become an effective marker for diagnosis and therapeutic control at the single-cell level. However, real-time analysis is hard to be achieved with traditional approaches because the exosomes usually need to be enriched by ultracentrifugation for a measurable signal-to-noise ratio. Recently developed label-free single-molecule imaging approaches may become an real-time quantitative tool for the analysis of single exosomes and related secretion behaviors of single living cells owing to their extreme sensitivity. 相似文献
3.
电磁超声换能器一般采用具有超强磁力的稀土永磁制作,在实际检测中由于磁力不可控,存在偏置磁场不够强导致换能效率过低和磁力过强造成操作不方便等问题.提出一种偏置磁场磁力可控的电磁超声换能器,采用电磁铁与永磁铁相结合的方式,达到偏置磁场磁力可控的目的.通过有限元仿真和试验得出,提出的偏置磁场磁力可控的电磁超声换能器,在电磁铁处于关闭模式下,永磁铁能够提供基础磁场;采用增强模式或减弱模式,无被测物时,换能器下表面平均垂直磁通最大分别增强78.58%和减弱19.36%,而提离2 mm检测钢板时,换能器下方钢板表面平均垂直磁通最大分别增强52.99%和减弱38.02%;得出3种模式下,探头磁力随着提离距离缩小而增强的试验曲线;通过增强模式对铝板和钢板进行测厚试验,将检测信号幅值分别提高46.91%和62.01%.所设计的磁力可控电磁超声换能器不仅具有磁力可控的功能,还能够提高检测信号幅值. 相似文献
4.
5.
Haiyue Xu Ji Zou Weimin Wang Hao Wang Wei Ji Zhengyi Fu 《Journal of the European Ceramic Society》2021,41(1):635-645
Fully dense ceramics with retarded grain growth can be attained effectively at relatively low temperatures using a high-pressure sintering method. However, there is a paucity of in-depth research on the densification mechanism, grain growth process, grain boundary characterization, and residual stress. Using a strong, reliable die made from a carbon-fiber-reinforced carbon (Cf/C) composite for spark plasma sintering, two kinds of commercially pure α-Al2O3 powders, with average particle sizes of 220 nm and 3 μm, were sintered at relatively low temperatures and under high pressures of up to 200 MPa. The sintering densification temperature and the starting threshold temperature of grain growth (Tsg) were determined by the applied pressure and the surface energy relative to grain size, as they were both observed to increase with grain size and to decrease with applied pressure. Densification with limited grain coarsening occurred under an applied pressure of 200 MPa at 1050 °C for the 220 nm Al2O3 powder and 1400 °C for the 3 μm Al2O3 powder. The grain boundary energy, residual stress, and dislocation density of the ceramics sintered under high pressure and low temperature were higher than those of the samples sintered without additional pressure. Plastic deformation occurring at the contact area of the adjacent particles was proved to be the dominant mechanism for sintering under high pressure, and a mathematical model based on the plasticity mechanics and close packing of equal spheres was established. Based on the mathematical model, the predicted relative density of an Al2O3 compact can reach ~80 % via the plastic deformation mechanism, which fits well with experimental observations. The densification kinetics were investigated from the sintering parameters, i.e., the holding temperature, dwell time, and applied pressure. Diffusion, grain boundary sliding, and dislocation motion were assistant mechanisms in the final stage of sintering, as indicated by the stress exponent and the microstructural evolution. During the sintering of the 220 nm alumina at 1125 °C and 100 MPa, the deformation tends to increase defects and vacancies generation, both of which accelerate lattice diffusion and thus enhance grain growth. 相似文献
6.
7.
目的 为了更科学地研究和检验可穿戴产品的适合性,提出一种适合性检验方法,能够精确保留现实环境中的产品佩戴关系,并能将现实与虚拟的适合性检验研究相结合,得到合理的适合性检验结果.方法 以虚拟现实眼镜的适合性检验为例,通过高精度的三维测量技术将现实环境中的人、产品以及人—产品佩戴关系转化为三维虚拟信息,并以人—产品佩戴三维模型为参考基准对齐人和产品的虚拟模型,得到保留现实佩戴关系的人—产品佩戴模型组,再应用偏差分析法得出人—机佩戴区域的可视化适合性结果和统计数据,结合主观评价方法进一步分析产品的适合性.结论 虚实结合的产品适合性检验方法可在虚拟环境中高精度地保留现实环境中的人—产品佩戴关系,并能得到可视化的适合性检验结果,为检验和指导产品的适合性提供依据. 相似文献
8.
9.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
10.
VOCs是形成臭氧的重要前体物,加强VOCs治理是现阶段控制臭氧污染的有效途径.废气生物处理装置为满足新的排放要求改造前应先对废气组分进行分析,并筛选合适的菌种进行接种以降低后续提标装置的投资.可采用吸附技术或高级氧化技术对生物处理装置出气进行提标处理.提标工艺如采用吸附技术需考虑吸附剂脱附产生物质的再处理. 相似文献