全文获取类型
收费全文 | 153242篇 |
免费 | 12984篇 |
国内免费 | 9387篇 |
专业分类
电工技术 | 5749篇 |
技术理论 | 3篇 |
综合类 | 9187篇 |
化学工业 | 43362篇 |
金属工艺 | 13291篇 |
机械仪表 | 4973篇 |
建筑科学 | 5701篇 |
矿业工程 | 2506篇 |
能源动力 | 5765篇 |
轻工业 | 10101篇 |
水利工程 | 1177篇 |
石油天然气 | 6052篇 |
武器工业 | 911篇 |
无线电 | 17800篇 |
一般工业技术 | 20802篇 |
冶金工业 | 6266篇 |
原子能技术 | 2311篇 |
自动化技术 | 19656篇 |
出版年
2024年 | 377篇 |
2023年 | 2405篇 |
2022年 | 4048篇 |
2021年 | 5829篇 |
2020年 | 4514篇 |
2019年 | 4078篇 |
2018年 | 3571篇 |
2017年 | 4518篇 |
2016年 | 5067篇 |
2015年 | 5150篇 |
2014年 | 7502篇 |
2013年 | 8520篇 |
2012年 | 9791篇 |
2011年 | 12560篇 |
2010年 | 9744篇 |
2009年 | 11188篇 |
2008年 | 9543篇 |
2007年 | 10980篇 |
2006年 | 9924篇 |
2005年 | 7793篇 |
2004年 | 6414篇 |
2003年 | 5738篇 |
2002年 | 4630篇 |
2001年 | 3622篇 |
2000年 | 3250篇 |
1999年 | 2525篇 |
1998年 | 1958篇 |
1997年 | 1463篇 |
1996年 | 1366篇 |
1995年 | 1157篇 |
1994年 | 1074篇 |
1993年 | 813篇 |
1992年 | 686篇 |
1991年 | 571篇 |
1990年 | 476篇 |
1989年 | 388篇 |
1988年 | 261篇 |
1987年 | 221篇 |
1986年 | 232篇 |
1985年 | 195篇 |
1984年 | 174篇 |
1983年 | 139篇 |
1982年 | 149篇 |
1981年 | 161篇 |
1980年 | 192篇 |
1979年 | 108篇 |
1978年 | 90篇 |
1977年 | 102篇 |
1976年 | 103篇 |
1975年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Isothermal nucleic-acid amplification methods such as Loop-Mediated isothermal AMPlification (LAMP) are increasingly appealing alternatives to PCR for use in portable diagnostic system due to the low cost, weight, and power requirements of the instrumentation. As such, interest in developing new probes and other functionality based on the LAMP reaction has been intense. Here, we report on the development of duplexed LAMP assays for pathogen detection using spectrally unique Assimilating Probes. As proof of principle, we used a reaction for Salmonella enterica as a model coupled with a reaction for λ-phage DNA as an internal control, as well as a duplexed assay to sub-type specific quarantine strains of the bacterial wilt pathogen Ralstonia solanacearum. Detection limits for bacterial DNA analyzed in individual reactions was less than 100 genomic equivalents in all cases, and increased by one to two orders of magnitude when reactions were coupled in duplexed formats. Even so, due to the more robust activity of newly available strand-displacing polymerases, the duplexed assays reported here were more powerful than analogous individual reactions reported only a few years ago, and represent a significant advance for incorporation of internal controls to validate assay results in the field. 相似文献
113.
Catalytic Hydrocracking of a Bitumen‐Derived Asphaltene over NiMo/γ‐Al2O3 at Various Temperatures
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hydrocracking of a bitumen‐derived asphaltene over NiMo/γ‐Al2O3 was investigated in a microbatch reactor at varying temperatures. The molar kinetics of asphaltene cracking reaction was examined by fitting the experimental data. Below a defined temperature, the molar reaction showed the first‐order kinetic feature while at higher temperatures secondary reactions such as coke formation became significant, causing deviation of the reaction behavior from the proposed first‐order kinetic model. Selectivity analysis proved that dominant products varied from gases to liquids to gases with increasing temperature, shifting the dominant reaction from C–S bonds cleavage to C–C bonds cleavage. 相似文献
114.
115.
116.
117.
前期杂交优化后赤芝菌种经液体深层发酵后,提取灵芝菌丝体多糖,并过DEAE-Sepharose Fast Flow柱分离纯化,利用高效体积排阻色谱(HPSEC)检测多糖级分的纯度,采用完全酸水解PMP柱前衍生化RP—HPLC测定多糖级分的单糖组成,多角度光散射仪联用装置(SEC—MALLS)测定其绝对重均分子量(Mw),并且根据分子旋转半径与分子摩尔数的关系曲线斜率初步推断其空间构象。结果显示:分离纯化得到3个多糖级分GLMP1、GLMP2和GLMP3,HPSEC检测其峰面积百分比分别为93.58%,97.64%,99.19%,单糖组成分析结果表明GLMP1、GLMP2和GLMP3均含有甘露糖、鼠李糖、半乳糖醛酸、葡萄糖、半乳糖、木糖、阿拉伯糖和岩藻糖,但单糖摩尔比各异。SEC—MALLS测试GLMP1、GLMP2和GLMP3的Mw分别为4.526×105,4.603×104,3.760×103 g/mol,3个多糖级分构象可能均为高度紧缩且具有分支结构的聚合物。 相似文献
118.
119.
120.
Peng Jiang Jiafeng Lu Kun Li Xiquan Chen Ruiqi Dan 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(5):381-386
AbstractPreparation condition can affect the structure and the properties of nanofiber membrane. In order to explore suitable conditions to prepare the Fe3O4/PVDF nanofiber membrane with good hydrophobicity, the hydrophobicity of Fe3O4/PVDF nanofiber membranes obtained by electrospinning was investigated by changing preparation conditions like weight percentage of Fe3O4 nanoparticles, blending quality concentration of poly (vinylidene fluoride) (PVDF) and Fe3O4 nanoparticles, and positive voltage. And the variations of hydrophobicity of Fe3O4/PVDF nanofiber membranes modified by 1H, 1H, 2H, 2H-perfluorodecyl trimethoxysilane were studied. The results show that the hydrophobicity of Fe3O4/PVDF nanofiber membranes has changed under different preparation conditions. The contact angles of samples increased after a modification by 1H, 1H, 2H, 2H-perfluorodecyl trimethoxysilane, which indicates that the hydrophobicity of Fe3O4/PVDF nanofiber membranes has been enhanced. 相似文献