全文获取类型
收费全文 | 931篇 |
免费 | 176篇 |
国内免费 | 75篇 |
专业分类
电工技术 | 46篇 |
综合类 | 79篇 |
化学工业 | 264篇 |
金属工艺 | 40篇 |
机械仪表 | 31篇 |
建筑科学 | 21篇 |
矿业工程 | 17篇 |
能源动力 | 28篇 |
轻工业 | 19篇 |
水利工程 | 13篇 |
石油天然气 | 19篇 |
武器工业 | 3篇 |
无线电 | 187篇 |
一般工业技术 | 158篇 |
冶金工业 | 41篇 |
原子能技术 | 2篇 |
自动化技术 | 214篇 |
出版年
2024年 | 7篇 |
2023年 | 44篇 |
2022年 | 34篇 |
2021年 | 41篇 |
2020年 | 53篇 |
2019年 | 56篇 |
2018年 | 44篇 |
2017年 | 62篇 |
2016年 | 55篇 |
2015年 | 52篇 |
2014年 | 60篇 |
2013年 | 66篇 |
2012年 | 70篇 |
2011年 | 65篇 |
2010年 | 62篇 |
2009年 | 64篇 |
2008年 | 54篇 |
2007年 | 37篇 |
2006年 | 41篇 |
2005年 | 29篇 |
2004年 | 45篇 |
2003年 | 13篇 |
2002年 | 26篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1182条查询结果,搜索用时 15 毫秒
1.
Yasuha Watanabe Prof. Kenzo Fujimoto 《Chembiochem : a European journal of chemical biology》2020,21(22):3244-3248
The regulation of DNAzyme activity is an important problem for its in vivo applications. We achieved photochemical regulation of DNAzyme activity by using reversible DNA photo-crosslinking of 3-cyanovinylcarbazole (CNVK). The ODN containing CNVK photo-crosslinked to a pyrimidine base in the complementary strand after a few seconds of photoirradiation, and its photoadduct was split by photoirradiation of another wavelength. The activity of photo-crosslinked DNAzyme with CNVK was completely inhibited (OFF state). In contrast, after 312 nm irradiation, DNAzyme activity was recovered upon addition of a substrate strand (ON state). In addition, the photo-crosslinked DNAzyme is prone to enzymatic digestion by exonuclease. This photochemical OFF to ON switching with reversible DNA photo-crosslinking was regulated at the desired time and position; therefore, it might be possible to use it for in vivo application. 相似文献
2.
Dealloyed nanoporous gold (np-Au) has applications as oxygen reduction catalysis in Li-air batteries and fuel cells, or as actuators to convert electricity into mechanical energy. However, it faces the challenges of coarsening-induced structure instability, mechanical weakness due to low relative densities, and slow dealloying rates. Here, monolithic np-Au is dealloyed from a single-phase Au25Ni75 solid-solution at a one-order faster dealloying rate, ultra-low residual Ni content, and importantly, one-third more relative density than np-Au dealloyed from conventional Au25Ag75. The small atomic radius and low dealloying potential of the sacrificing element Ni are intrinsically beneficial to fast produce high relative density np-Au, as predicted by a general model for dealloying of binary alloys and validated by experiments. Stable, durable, and reversible actuation of np-Au takes place under cyclic potential triggering in alkaline and acidic electrolytes with negligible coarsening-induced strain-shift. The thermal and mechanical robustness of bulk np-Au is confirmed by two-order slower ligament coarsening rates during annealing at 300 °C and 45 MPa macroscopic yielding strength distinctive from the typical early onset of plastic yielding. This article opens a rich direction to achieve high relative density np-Au which is essential for porous network connectivity, mechanical strength, and nanostructure robustness for electrochemical functionality. 相似文献
3.
4.
Reversible Flat to Rippling Phase Transition in Fe Containing Layered Battery Electrode Materials 下载免费PDF全文
《Advanced functional materials》2018,28(39)
Layered sodium transition metal oxides of NaTMO2 (TM = 3d transition metal) show unique capability to mix different compositions of Fe to the TM layer, a phenomenon that does not exist in LiTMO2. Here, a novel spontaneous TM layer rippling in the sodium ion battery cathode materials is reported, revealed by in situ X‐ray diffraction, Cs‐corrected scanning transmission electron microscopy, and density functional theory simulation, where the softening and distortion of FeO6 octahedra collectively drives the flat TM planes into rippled ones with inhomogeneous interlayer distance at high voltage. In such a rippling phase, charge and discharge of Na ions take different evolution pathways, resulting in an unusual hysteresis voltage loop. Importantly, upon discharge beyond a certain Na composition, the rippling TM layer will go back to flat, giving the reversibility of such structural evolution in the following cycles. 相似文献
5.
6.
Teh C. Ho 《American Institute of Chemical Engineers》2020,66(6):e16930
Metal sulfide catalysts for ultra-deep hydrodesulfurization of diesel generally lose a fraction of their catalytically active sites during reactor startup. The underlying mechanisms are discussed. A laboratory diagnostic tool consisting of three probe molecules is developed for testing metal sulfide catalysts' start-of-run (SOR) activity maintenance. It is found that a significant fraction of the active sites on a commercial supported catalyst are deactivated permanently, but this is not the case with a bulk metal sulfide catalyst. The SOR deactivation of the bulk catalyst is completely reversible, while that of the supported catalyst is partially reversible. The diagnostic tool may provide a basis for developing a high-throughput approach for evaluating and enhancing catalyst SOR stability, thereby increasing plant productivity. 相似文献
7.
8.
地质钻塔拆装机及机装可逆式钻塔 总被引:2,自引:1,他引:2
指出了目前钻塔拆装存在的缺点,提出了解决的新途径,研制成功了四腿钻塔拆装机及机装可逆式四腿管子钻塔,认为这是地质钻塔发展的新方向。 相似文献
9.
图像可逆信息隐藏作为信息隐藏的重要分支,发展至今已近三十年,因其独有的图像无损恢复能力,一直备受医学、司法、军事等重点领域的青睐。然而现有可逆信息隐藏研究成果繁多,迁移知识广泛,本文简要梳理可逆信息隐藏的发展脉络,在回顾经典算法的基础上,加以简化、注释,总结成功经验,展望潜在应用,以期为研究者提供一个按图索骥的探索路径。本文主要包括3个部分,分别为位图(Bitmap,BMP)图像的可逆信息隐藏(适用于空域嵌入操作)、JPEG (Joint Photographic Experts Group)图像的可逆信息隐藏(适用于频域和编码域嵌入操作)和鲁棒可逆水印(适用于扩展性研究)。通过近百篇高影响力文献的梳理可知,可逆研究的受众广泛、基础深厚,其严谨的数学定义和简明的机理论证是深受研究者推崇和坚持的重要原因。“干净、简明”的特点也是其能够与现实应用有效结合的强力抓手。增加可逆算法对于载体多样性的普适性研究,引入新的评价指标来导引算法与现实应用的融合,将是未来可开拓的方向。可逆信息隐藏技术能够恢复图像初始状态,其独特之处在于图像本身就是一个复杂语义的信息表达。这既要求可逆嵌入操作所施加的影响不能改变图像所表达的主要语义,又要求该操作是可消除的,保留溯源能力,将内容的信息表达权始终交由图像本身。这一特点不仅为敏感领域信息处理所亟需,也是其他常见领域并不排斥的。严格来说,一定程度上的复原本就是事物发展到一定阶段后的必然追求。据此,本文认为推广可逆研究与多学科融合解决更难、更广泛的问题,实现长远发展,是完全必要且可行的。 相似文献
10.
大林煤矿在对经过反向风门墙垛的风筒逆向隔断装置进行革新改造后,增强了逆向隔断装置的可靠性,降低了逆向隔断装置的破坏率,从而最大限度地提高了发生煤与瓦斯突出时逆向隔断风流的保险系数。 相似文献