全文获取类型
收费全文 | 105833篇 |
免费 | 7575篇 |
国内免费 | 4346篇 |
专业分类
电工技术 | 6028篇 |
技术理论 | 26篇 |
综合类 | 8342篇 |
化学工业 | 13707篇 |
金属工艺 | 4961篇 |
机械仪表 | 7853篇 |
建筑科学 | 10959篇 |
矿业工程 | 5510篇 |
能源动力 | 3331篇 |
轻工业 | 8099篇 |
水利工程 | 2397篇 |
石油天然气 | 5132篇 |
武器工业 | 2426篇 |
无线电 | 10057篇 |
一般工业技术 | 6446篇 |
冶金工业 | 4511篇 |
原子能技术 | 425篇 |
自动化技术 | 17544篇 |
出版年
2024年 | 139篇 |
2023年 | 1066篇 |
2022年 | 2150篇 |
2021年 | 2942篇 |
2020年 | 2946篇 |
2019年 | 1953篇 |
2018年 | 1832篇 |
2017年 | 2704篇 |
2016年 | 3187篇 |
2015年 | 3581篇 |
2014年 | 7940篇 |
2013年 | 6026篇 |
2012年 | 7723篇 |
2011年 | 8654篇 |
2010年 | 6445篇 |
2009年 | 6748篇 |
2008年 | 6252篇 |
2007年 | 7544篇 |
2006年 | 6666篇 |
2005年 | 5843篇 |
2004年 | 4991篇 |
2003年 | 4502篇 |
2002年 | 3603篇 |
2001年 | 2983篇 |
2000年 | 2299篇 |
1999年 | 1733篇 |
1998年 | 1194篇 |
1997年 | 870篇 |
1996年 | 725篇 |
1995年 | 604篇 |
1994年 | 453篇 |
1993年 | 334篇 |
1992年 | 275篇 |
1991年 | 203篇 |
1990年 | 162篇 |
1989年 | 127篇 |
1988年 | 78篇 |
1987年 | 48篇 |
1986年 | 58篇 |
1985年 | 36篇 |
1984年 | 35篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Shraddha Parate Vikas Kumar Danishuddin Jong Chan Hong Keun Woo Lee 《International journal of molecular sciences》2021,22(10)
Heparanase (Hpse) is an endo-β-D-glucuronidase capable of cleaving heparan sulfate side chains. Its upregulated expression is implicated in tumor growth, metastasis and angiogenesis, thus making it an attractive target in cancer therapeutics. Currently, a few small molecule inhibitors have been reported to inhibit Hpse, with promising oral administration and pharmacokinetic (PK) properties. In the present study, a ligand-based pharmacophore model was generated from a dataset of well-known active small molecule Hpse inhibitors which were observed to display favorable PK properties. The compounds from the InterBioScreen database of natural (69,034) and synthetic (195,469) molecules were first filtered for their drug-likeness and the pharmacophore model was used to screen the drug-like database. The compounds acquired from screening were subjected to molecular docking with Heparanase, where two molecules used in pharmacophore generation were used as reference. From the docking analysis, 33 compounds displayed higher docking scores than the reference and favorable interactions with the catalytic residues. Complex interactions were further evaluated by molecular dynamics simulations to assess their stability over a period of 50 ns. Furthermore, the binding free energies of the 33 compounds revealed 2 natural and 2 synthetic compounds, with better binding affinities than reference molecules, and were, therefore, deemed as hits. The hit compounds presented from this in silico investigation could act as potent Heparanase inhibitors and further serve as lead scaffolds to develop compounds targeting Heparanase upregulation in cancer. 相似文献
2.
3.
Makoto Yamaguchi 《应用聚合物科学杂志》2021,138(14):50172
Perfluorosulfonic acid ionomer membranes have been widely used as proton conducting membranes in various electrochemical processes such as polymer electrolyte fuel cells and water electrolysis. While their thermal stability has been studied by thermogravimetry and analysis of low molecular weight products, their decomposition mechanism is little understood. In this study a newly developed methodology of thermal desorption and pyrolysis in combination with direct analysis in real time mass spectrometry is applied for Nafion membrane. An ambient ionization source and a high-resolution time-of-flight mass spectrometer enabled unambiguous assignment of gaseous products. Thermal decomposition is initiated by side chain detachment above 350°C, which leaves carbonyls on the main chain at the locations of the side chains. Perfluoroalkanes are released above 400°C by main chain scission and their further decomposition products dominate above 500 °C. DFT calculation of reaction energies and barrier heights of model compounds support proposed decomposition reactions. 相似文献
4.
Thomas R. Savage Fernando Almeida-Trasvina Ehecatl A. del-Rio Chanona Robin Smith Dondga Zhang 《American Institute of Chemical Engineers》2021,67(11):e17358
With liquefied natural gas becoming increasingly prevalent as a flexible source of energy, the design and optimization of industrial refrigeration cycles becomes even more important. In this article, we propose an integrated surrogate modeling and optimization framework to model and optimize the complex CryoMan Cascade refrigeration cycle. Dimensionality reduction techniques are used to reduce the large number of process decision variables which are subsequently supplied to an array of Gaussian processes, modeling both the process objective as well as feasibility constraints. Through iterative resampling of the rigorous model, this data-driven surrogate is continually refined and subsequently optimized. This approach was not only able to improve on the results of directly optimizing the process flow sheet but also located the set of optimal operating conditions in only 2 h as opposed to the original 3 weeks, facilitating its use in the operational optimization and enhanced process design of large-scale industrial chemical systems. 相似文献
5.
6.
本文采用超星学习通线上教学平台,以 “高电压技术”课程为对象,实施了规模为120余人的线上线下混合式教学。基于线上教学和传统教学的优势互补,设计了“高电压技术”多个教学环节。归纳分析了混合式教学在各个教学环节取得的效果和问题,并根据学生反馈提出了持续性的改进措施。 相似文献
7.
Colleen Varaidzo Manyumwa
zlem Tastan Bishop 《International journal of molecular sciences》2021,22(6)
Carbonic anhydrases (CAs) have been identified as ideal catalysts for CO2 sequestration. Here, we report the sequence and structural analyses as well as the molecular dynamics (MD) simulations of four γ-CAs from thermophilic bacteria. Three of these, Persephonella marina, Persephonella hydrogeniphila, and Thermosulfidibacter takaii originate from hydrothermal vents and one, Thermus thermophilus HB8, from hot springs. Protein sequences were retrieved and aligned with previously characterized γ-CAs, revealing differences in the catalytic pocket residues. Further analysis of the structures following homology modeling revealed a hydrophobic patch in the catalytic pocket, presumed important for CO2 binding. Monitoring of proton shuttling residue His69 (P. marina γ-CA numbering) during MD simulations of P. hydrogeniphila and P. marina’s γ-CAs (γ-PhCA and γ-PmCA), showed a different behavior to that observed in the γ-CA of Escherichia coli, which periodically coordinates Zn2+. This work also involved the search for hotspot residues that contribute to interface stability. Some of these residues were further identified as key in protein communication via betweenness centrality metric of dynamic residue network analysis. T. takaii’s γ-CA showed marginally lower thermostability compared to the other three γ-CA proteins with an increase in conformations visited at high temperatures being observed. Hydrogen bond analysis revealed important interactions, some unique and others common in all γ-CAs, which contribute to interface formation and thermostability. The seemingly thermostable γ-CA from T. thermophilus strangely showed increased unsynchronized residue motions at 423 K. γ-PhCA and γ-PmCA were, however, preliminarily considered suitable as prospective thermostable CO2 sequestration agents. 相似文献
8.
纵观当今的发展格局,是科学技术高速发展的时代。随着5G时代的来临,网络技术在各个领域中扮演着越来越重要的角色。特别是在医疗方面,为医院的日常工作奠定了坚实的基础。今天就5G网络技术在医院只能服务中的应用展开谈论。 相似文献
9.
为解决沧州市涉地税源管理手段单一等问题,文中提出以测绘地理信息技术为支撑,通过对多源数据组织管理,建立风险分析指标,采用多种GIS空间分析方法构建了涉地风险税源识别模式并在沧州进行应用。结果表明:该模式能有效识别多种涉地风险,为涉地税源管理提供了支撑。 相似文献
10.
分析近年来RTO装置发生的安全事故,找出了该类环保装置存在的安全风险,并在储罐与污水池废气分类处理、在线废气浓度检测仪与废气切断阀的位置设置、新风稀释及风机控制、阻火器与爆破片、操作压力、储罐呼吸阀后采用非接触废气罩收集、风机材质等方面提出了建议。 相似文献