全文获取类型
收费全文 | 7436篇 |
免费 | 656篇 |
国内免费 | 316篇 |
专业分类
电工技术 | 274篇 |
技术理论 | 2篇 |
综合类 | 748篇 |
化学工业 | 2613篇 |
金属工艺 | 272篇 |
机械仪表 | 797篇 |
建筑科学 | 563篇 |
矿业工程 | 162篇 |
能源动力 | 121篇 |
轻工业 | 762篇 |
水利工程 | 66篇 |
石油天然气 | 280篇 |
武器工业 | 137篇 |
无线电 | 222篇 |
一般工业技术 | 882篇 |
冶金工业 | 181篇 |
原子能技术 | 34篇 |
自动化技术 | 292篇 |
出版年
2024年 | 24篇 |
2023年 | 148篇 |
2022年 | 153篇 |
2021年 | 216篇 |
2020年 | 200篇 |
2019年 | 194篇 |
2018年 | 169篇 |
2017年 | 231篇 |
2016年 | 230篇 |
2015年 | 221篇 |
2014年 | 415篇 |
2013年 | 411篇 |
2012年 | 618篇 |
2011年 | 529篇 |
2010年 | 402篇 |
2009年 | 408篇 |
2008年 | 357篇 |
2007年 | 556篇 |
2006年 | 458篇 |
2005年 | 434篇 |
2004年 | 360篇 |
2003年 | 281篇 |
2002年 | 272篇 |
2001年 | 191篇 |
2000年 | 186篇 |
1999年 | 151篇 |
1998年 | 121篇 |
1997年 | 92篇 |
1996年 | 68篇 |
1995年 | 51篇 |
1994年 | 52篇 |
1993年 | 44篇 |
1992年 | 34篇 |
1991年 | 24篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有8408条查询结果,搜索用时 0 毫秒
1.
Poor aqueous solubility is one of the recurrent drawbacks of many compounds in medicinal chemistry. To overcome this limitation, the dilution of drug candidates from stock solutions of an organic solvent is common practice. However, the precise characterisation of these compounds in aqueous solutions is often neglected, leading to some uncertainties regarding the nature of the actual active species. In this communication, we demonstrate that two ruthenium complexes previously reported by our group for their chemotherapeutic potential against cancer, namely [Ru(DIP)2(sq)](PF6) and [Ru(DIP)2(3-methoxysq)](PF6), where DIP is 4,7-diphenyl-1,10-phenanthroline, sq=semiquinonate and 3-methoxysq=3-methoxysemiquinonate, form colloids in water-DMSO (1 % v/v) mixtures that are invisible to the naked eyes. [Ru(DIP)2(3-methoxysq)](PF6) was found to form a highly stable and monodispersed colloid with nanoaggregates of ∼25 nm. In contrast, [Ru(DIP)2(sq)](PF6) was found to form large reticulates of mostly spherical aggregates which size was found to increase over time. The difference in size and shape distribution of drug candidates is of tremendous significance as the study of their biological activity might be severely affected. Overall, we strongly believe that these observations should be taken into account by the scientific community working on the development of metal-based drugs with poor water solubility. 相似文献
2.
《Advanced Powder Technology》2020,31(2):746-754
Although many colloidal assembling systems have been reported, most systems suffer from severe aggregation under high solid concentrations, which can often be observed in typical hetero-aggregation system. In this study, we created a hetero-assembly system using concentrated (~50 vol%) suspensions by mixing large SiO2 particles modified with polyacrylic acid partially complexed with oleylamine (PAA-OAm) and small SiO2 particles modified with polyethyleneimine partially complexed with oleic acid (PEI-OA) in a non-aqueous solvent. We demonstrated that hetero-assembly is driven by the interactions between the uncomplexed carboxyl/amine groups of the PAA/PEI present on the particles, while severe aggregation is simultaneously prevented by the steric repulsions of the aliphatic oleyl chains. Comparison of the cross sections of the in-situ solidified hetero-assembled suspensions with those of ideally assembled structures which were reproduced by a simulation considering the statistical distribution of particles strongly supported successful particle assembling via the proposed approach. The results revealed that the OA content in the PEI-OA complex was the dominant factor that controlled the dispersion and assembling state of the binary particles. The significance of this study is that our findings will provide a class of colloidal dispersion state which binary particles were assembled in a high solid content suspension without forming strong aggregates. 相似文献
3.
《Ceramics International》2021,47(23):32699-32709
Digital light processing (DLP)-based ceramic stereolithography has attracted significant attentions due to the high printing speed and high dimensional accuracy of DLP printers. However, undesired dropping of unfinished ceramic parts during printing, owing to inadequate adhesion between the first cured layer and the substrate of the building platform, still remains a challenge. In this study, the relationship between the adhesion properties of ultraviolet (UV)-curable alumina (α-Al2O3) suspensions and the functionalities and structures of UV-curable acrylate monomers was investigated. With an increase in the proportions of monofunctional monomers, the adhesion abilities of UV-curable alumina suspensions enhanced because of reduced volume shrinkage, however, inferior curing performances were observed due to a decrease in the double bond densities. Furthermore, the large-volume branched chain structures in monofunctional monomers and ethyoxyl groups in polyfunctional monomers effectively decreased the volume contraction, improving the adhesion performances of UV-curable alumina suspensions and facilitating the conversion of double bonds to provide excellent curing properties, further guaranteeing strong adhesion of these suspensions to the substrate. 相似文献
4.
《Ceramics International》2022,48(17):24953-24964
5.
Covalent triazine frameworks (CTFs) have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties. However, the usually highly hydrophobic nature of CTFs, which originates from their overall aromatic backbone, leads to limitations of CTFs for applications in aqueous media. In this study, we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica (SBA-15) for efficient photocatalysis in aqueous medium. A thiophene-containing CTF was directly synthesized in mesopores of SBA-15. Due to the high surface area and the added hydrophilic properties by silica, the hybrid material demonstrated excellent adsorption of organic molecules in water. This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water, but also for efficient photocatalysis in solvent-free and solid state. Furthermore, the reusability, stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media. 相似文献
6.
7.
8.
水溶液全循环法尿素装置中压分解"三种工艺"的比较 总被引:1,自引:0,他引:1
以生产数据结合理论计算的方法系统地比较、分析了水溶液全循环法尿素装置中中压分解“三种工艺”的热能利用、甲铵分解率、总氨蒸出率、水平衡量、一分加热器生产能力等方面的情况,提出应用和配置预分离-预蒸馏工艺的方法,评论该工艺在水溶液全循环法中的地位和作用。 相似文献
9.
聚合物降解产物伤害与糖甙键特异酶破胶技术 总被引:22,自引:1,他引:21
综述了钻井,完井,尤其是水力压裂作业中产生的多糖类聚合物伤害和应用糖甙键特异酶破胶,解除多糖类聚合物伤害的技术。第一节报道了聚合物降解产物造成的伤害,指出冻胶破胶液粘度低并不代表压裂液已从充填裂缝中充分返排,氧化破胶剂和普通酶破胶剂不能使多糖类聚合物充分降解,产生的大分子量,水不溶的降解产物可对地层造成伤害,消除伤害的办法是采用对糖甙键有特异性的各种水解酶作压裂液破胶剂或伤害地层处理剂。第二节报道了各种聚合物(纤维素,瓜尔胶,淀粉)糖甙键特异酶降解聚合物的机理。第三节报道了糖甙键特异酶(主要针对瓜尔胶)的应用性能测试及结果,包括岩心流动实验,含糖量和分子量测定,传导性测试。第四节介绍了糖甙键特异酶消除聚合物伤害和用作压裂液破胶剂的现场应用,包括选井原则,实施工艺要点及3个典型井例。 相似文献
10.