全文获取类型
收费全文 | 6585篇 |
免费 | 846篇 |
国内免费 | 366篇 |
专业分类
电工技术 | 384篇 |
综合类 | 499篇 |
化学工业 | 1223篇 |
金属工艺 | 354篇 |
机械仪表 | 310篇 |
建筑科学 | 521篇 |
矿业工程 | 183篇 |
能源动力 | 229篇 |
轻工业 | 663篇 |
水利工程 | 154篇 |
石油天然气 | 340篇 |
武器工业 | 51篇 |
无线电 | 814篇 |
一般工业技术 | 832篇 |
冶金工业 | 269篇 |
原子能技术 | 79篇 |
自动化技术 | 892篇 |
出版年
2024年 | 19篇 |
2023年 | 159篇 |
2022年 | 290篇 |
2021年 | 417篇 |
2020年 | 318篇 |
2019年 | 288篇 |
2018年 | 292篇 |
2017年 | 321篇 |
2016年 | 276篇 |
2015年 | 309篇 |
2014年 | 370篇 |
2013年 | 471篇 |
2012年 | 488篇 |
2011年 | 431篇 |
2010年 | 363篇 |
2009年 | 322篇 |
2008年 | 348篇 |
2007年 | 279篇 |
2006年 | 253篇 |
2005年 | 227篇 |
2004年 | 172篇 |
2003年 | 207篇 |
2002年 | 259篇 |
2001年 | 233篇 |
2000年 | 136篇 |
1999年 | 114篇 |
1998年 | 72篇 |
1997年 | 60篇 |
1996年 | 58篇 |
1995年 | 55篇 |
1994年 | 35篇 |
1993年 | 36篇 |
1992年 | 20篇 |
1991年 | 27篇 |
1990年 | 19篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有7797条查询结果,搜索用时 531 毫秒
1.
Xiaozhen Li Chao Yin Si Si Liew Chun-Sing Lee Kanyi Pu 《Advanced functional materials》2021,31(46):2106154
Optical imaging has played a pivotal role in deciphering in vivo bioinformatics but is limited by shallow penetration depth and poor imaging performance owing to interfering tissue autofluorescence induced by concurrent photoexcitation. The emergence of near-infrared (NIR) self-luminescence imaging independent of real-time irradiation has timely addressed these problems. There are two main kinds of self-luminescent agents, namely inorganic and organic luminophores. Inorganic luminophores usually suffer from long-term biotoxicity concerns resulting from potential heavy-metal ions leakage and nonbiodegradability, which hinders their further translational application. In contrast, organic luminophores, especially organic semiconducting luminophores (OSLs) with good biodegradable potential, tunable design, and outstanding optical properties, are preferred in biological applications. This review summarizes the recent progress of OSLs used in NIR afterglow, chemiluminescence, and bioluminescence imaging. Molecular manipulation and nanoengineering approaches of OSLs are discussed, with emphasis on strategies that can extend the emission wavelength from visible to NIR range and amplify luminescence signals. This review concludes with a discussion of current challenges and possible solutions of OSLs in the self-luminescence field. 相似文献
2.
Nowadays, oil pollution has become more serious, which causes great threats both to the ecological environment and human life. In this study, a novel type of multifunctional deacetylated cellulose acetate/polyurethane (d-MCA:MTPU) composite nanofiber membranes for oil/water separation are successfully fabricated by electrospinning, which show super-amphiphilicity in air, super-hydrophilicity in oil, and oleophobicity in water. All the d-MCA:MTPU composite nanofiber membranes with different mass ratios can be used as water-removing, oil-removing, and emulsion separation substance only by gravity driving force. The highest separation flux for water and oil reaches up to 37 000 and 74 000 L m−2 h−1, respectively, and all the separation efficiencies are more than 99%. They have outstanding comprehensive mechanics performance, which can be controlled by simply adjusting the mass ratios. They show excellent antifouling and self-cleaning ability, endowing powerful cyclic stability and reusability. Those results show that d-MCA:MTPU composite nanofiber membranes have great application prospects in oil/water separation. 相似文献
3.
4.
5.
Yuanfang Tao Xin Ji Dr. Jian Zhang Yue Jin Nannan Wang Prof. Yubing Si Prof. Weili Zhao 《Chembiochem : a European journal of chemical biology》2020,21(21):3131-3136
Near-infrared (NIR) fluorescent probes are very significant for detecting cysteine in biological systems. Herein, we report a highly selective and sensitive NIR turn-on fluorescent probe (BDP-NIR) based on BODIPY with large Stokes shift (105 nm) for detecting Cys. We clarified the sensing mechanism based on the different thiol-induced SNAr substitution/rearrangement reaction of the probe with cysteine and homocysteine/glutathione, which leads to the corresponding amino- and thiol-BODIPY dyes with distinct photophysical properties. Moreover, a novel mechanism of fluorescence quenching was demonstrated by density functional theory calculation. The reason for the fluorescence quenching of the probe might be intersystem crossing (from singlet to triplet excited state). Moreover, BDP-NIR had a high linear dynamic range of 0–500 μM, which was promising for detecting cysteine quantificationally. Significantly, BDP-NIR was capable of sensing endogenous cysteine in living cells and in vivo. 相似文献
6.
Carbohydrates and their conjugates play important roles in many biological processes including fertilization, differentiation, development, immune response, and infection. Their activities are largely dependent on the properties of terminal mono‐ or disaccharides. Galactose, mannose, fucose, glucose, sialic acid, etc., are commonly used as powerful scaffolds installed on drug molecules for targeting specific tissues including brain, liver, and cancers, and as epitopes for enhancing the targeting of various vaccines. This review focuses on the influence of their structural variations, including changes in sugar type, substituent groups and their positions, as well as length of linker portion, on the targeting of drugs or their efficacy. Particular attention is paid to the targeting properties of mono‐ and disaccharides applied in drug design and discovery. 相似文献
7.
8.
雷斯 《石油化工腐蚀与防护》2006,23(5):35-37,41
文章介绍了中国石油化工股份有限公司齐鲁石化分公司胜利炼油厂第二常减压蒸馏装置的总体情况,分析总结了装置在2000-2005年期间停工闲置及开工运行过程中设备腐蚀情况和防护中所做的工作,可供相似类型、相似状态的装置借鉴。 相似文献
9.
激光熔覆Ni基B4C合金涂层的组织与性能研究 总被引:7,自引:0,他引:7
利用5kW连续波CO2激光器对16Mn钢基材表面预置的含20 vol%B4CP的Ni基合金复合粉末进行激光熔覆得到Ni基B4C合金涂层(NiB4c),研究了NiB4c涂层的组织形貌与相组成,并用单纯的镍基合金涂层(Ni60)进行了显微硬度及滑动磨损性能的对比试验。结果表明,NiB4C涂层由涂层下部的胞状晶和涂层中上部的树状枝晶及其间的共晶组织所组成,其组成相为γ-Ni,γ-(Ni,Fe)固溶体和(Cr,Fe)7C3,CrB,Ni3B,Fe2B,Fe23(C,B)6等化合物,涂层中存在未熔的B4C颗粒。激光熔覆NiB4c涂层比Ni60涂层具有较高的硬度和耐磨性,并分析了NiB4C涂层的强化机理。 相似文献
10.