全文获取类型
收费全文 | 4706篇 |
免费 | 483篇 |
国内免费 | 212篇 |
专业分类
电工技术 | 35篇 |
技术理论 | 1篇 |
综合类 | 290篇 |
化学工业 | 2717篇 |
金属工艺 | 177篇 |
机械仪表 | 34篇 |
建筑科学 | 90篇 |
矿业工程 | 196篇 |
能源动力 | 63篇 |
轻工业 | 417篇 |
水利工程 | 38篇 |
石油天然气 | 367篇 |
武器工业 | 115篇 |
无线电 | 44篇 |
一般工业技术 | 375篇 |
冶金工业 | 393篇 |
原子能技术 | 31篇 |
自动化技术 | 18篇 |
出版年
2024年 | 15篇 |
2023年 | 45篇 |
2022年 | 83篇 |
2021年 | 125篇 |
2020年 | 126篇 |
2019年 | 116篇 |
2018年 | 103篇 |
2017年 | 147篇 |
2016年 | 200篇 |
2015年 | 180篇 |
2014年 | 269篇 |
2013年 | 300篇 |
2012年 | 351篇 |
2011年 | 352篇 |
2010年 | 261篇 |
2009年 | 283篇 |
2008年 | 234篇 |
2007年 | 294篇 |
2006年 | 291篇 |
2005年 | 257篇 |
2004年 | 216篇 |
2003年 | 190篇 |
2002年 | 175篇 |
2001年 | 139篇 |
2000年 | 124篇 |
1999年 | 108篇 |
1998年 | 75篇 |
1997年 | 54篇 |
1996年 | 43篇 |
1995年 | 34篇 |
1994年 | 41篇 |
1993年 | 31篇 |
1992年 | 25篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 24篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有5401条查询结果,搜索用时 15 毫秒
991.
以二甲基二烯丙基氯化铵(DMDAAC)和烯丙基缩水甘油醚(AGE)为原料,过硫酸钠为引发剂,合成了一种环保型双活性基固色剂P(DMDAAC-AGE).通过FT-IR、TG-DTA和SEM等表征了固色剂的结构和性能.讨论了影响固色剂P(DMDAAC-AGE)性能的主要因素.合成P(DMDAAC-AGE)的优化工艺条件为:单体n(AGE)∶n(DMDAAC)=1∶2,在水相介质中,反应混合液中总单体初始质量分数为30%,引发剂0.75%(对单体质量),引发剂和原料AGE的加料方式为连续滴加,80℃保温反应6 h.将合成的固色剂用于活性染料染棉织物的固色,湿摩擦牢度可达4级,干摩擦牢度可达4~5级,皂洗沾色牢度可达4级. 相似文献
992.
993.
994.
Kang‐Zhen Xu Hang Zhang Ping Liu Jie Huang Ying‐Hui Ren Bo‐Zhou Wang Feng‐Qi Zhao 《Propellants, Explosives, Pyrotechnics》2012,37(6):653-661
1,4‐Dihydro‐5H‐(dinitromethylene)‐tetrazole ammonium salt ((NH4)2DNMT), a high nitrogen energetic compound, was synthesized and structurally characterized by single‐crystal X‐ray diffraction. The thermal behavior of (NH4)2DNMT was studied with DSC and TG‐DTG methods. The kinetic equation of the thermal decomposition reaction is: dα/dT=1013.17/3β(1−α)−2 exp(−1.388×105/RT). The critical temperature of thermal explosion is 182.7 °C. The specific heat capacity of (NH4)2DNMT was determined and the molar heat capacity is 301 J mol−1 K−1 at 298.15 K. The adiabatic time‐to‐explosion of (NH4)2DNMT was calculated to be 277 s. The detonation velocity and detonation pressure were also estimated. All results showed that (NH4)2DNMT presents good performance. 相似文献
995.
Kawagoshi Y Fujisaki K Tomoshige Y Yamashiro K Qiao Y 《Journal of Bioscience and Bioengineering》2012,113(4):515-520
Anaerobic ammonium oxidation (anammox) bacteria have been detected in variety of marine environment in recent years, however, there have been only a few studies on their characteristics in the culture. The aim of this study is to reveal the effect of temperature on nitrogen removal ability and bacterial community in a culture of marine anammox bacteria (MAAOB). The MAAOB were cultured from the sediment of a sea-based waste disposal site at the North Port of Osaka Bay in Japan. The maximum nitrogen removal rate (NRR) was observed at 25°C in the MAAOB culture, and it decreased both at below 20°C and over 33°C. The activation energy of the MAAOB culture was calculated to be 54.6 kJ mol(-1) in the 5°C to 30°C range. No significant change in bacterial community according with temperature (5-37°C) was confirmed in the results of polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE). Meanwhile, a number of bacteria related to the oxidation-reduction reaction of sulfur were confirmed and it is speculated that they involved in the activity of MAAOB and nitrogen removal ability in the culture. 相似文献
996.
Adsorption of nitrate and monovalent phosphate anions from aqueous solutions on mono, di‐ and tri‐ammonium‐functionalised mesoporous SBA‐15 silica was investigated. The adsorbents were prepared via a post‐synthesis grafting method, using either 3‐aminopropyltrimethoxysilane (N‐silane) or [1‐(2‐aminoethyl)‐3‐aminopropyl]trimethoxysilane (NN‐silane) or 1‐[3‐(trimethoxysilyl)‐propyl]‐diethylenetriamine (NNN‐silane), followed by acidification in HCl solution to convert the attached surface amino groups to positively charged ammonium moieties. The nominal loading of amino moieties on the SBA‐15 surface was varied from 5% to 20% as organoalkoxysilane/silica molar ratio. The adsorption experiments were conducted batchwise at room temperature. Results showed that adsorption capacity increased with increasing the concentration of monoammonium groups on the SBA‐15 adsorbent. Nitrate adsorption capacity increased from 0.34 to 0.66 mmol ${\rm NO}_{3}^{{-} } /{\rm g}$ adsorbent while phosphate adsorption capacity increased from 0.34 to 0.63 mmol ${\rm H}_{2} {\rm PO}_{4}^{{-} } /{\rm g}$ adsorbent when the molar ratio organoalkoxysilane/silica was varied from 5% to 20%, respectively. Also, for the same organoalkoxysilane/silica molar ratio of 10%, the adsorption capacity increased with the increase of the number of protonated amines in the functional groups. Therefore, maximum adsorption capacities of 0.80, 1.16 and 1.38 mmol ${\rm NO}_{3}^{{-} } /{\rm g}$ adsorbent and 0.72, 0.82 and 1.17 mmol ${\rm H}_{2} {\rm PO}_{4}^{{-} } /{\rm g}$ adsorbent were obtained using mono‐, di‐ and triammonium functionalised SBA‐15 adsorbents, respectively. © 2011 Canadian Society for Chemical Engineering 相似文献
997.
Ananta Kumar MishraSaswata Bose Tapas KuilaNam Hoon Kim Joong Hee Lee 《Progress in Polymer Science》2012,37(6):842-869
Proton-exchange membrane fuel cells have emerged as a promising emission free technology to fulfill the existing power requirements of the 21st century. Nafion® is the most widely accepted and commercialized membrane to date and possesses excellent electrochemical properties below 80 °C, under highly humidified conditions. However, a decrease in the proton conductivity of Nafion® above 80 °C and lower humidity along with high membrane cost has prompted the development of new membranes and techniques. Addition of inorganic fillers, especially silicate-based nanomaterials, to the polymer membrane was utilized to partially overcome the aforementioned limitations. This is because of the lower cost, easy availability, high hydrophilicity and higher thermal stability of the inorganic silicates. Addition of silicates to the polymer membrane has also improved the mechanical, thermal and barrier properties, along with water uptake of the composite membranes, resulting in superior performance at higher temperature compared to that of the virgin membrane. However, the degrees of dispersion and interaction between the organic polymer and inorganic silicates play vital roles in improving the key properties of the membranes. Hence, different techniques and solvent media were used to improve the degrees of nanofiller dispersion and the physico-chemical properties of the membranes. This review focuses mainly on the techniques of silicate-based nanocomposite fabrication and the resulting impact on the membrane properties. 相似文献
998.
999.
1000.
以蓖麻油酸甲酯为起始原料,与N,N-二甲基-1,3-丙二胺和溴化苄、溴乙烷通过酰胺化反应和季铵化反应生成了新型蓖麻油基季铵盐,其结构经FTIR、1HNMR、13CNMR及ESI-MS进行了确证。采用抑菌圈直径法对目标产物的抑菌性能进行了测试,结果表明,两种季铵盐均有一定的抑菌活性,N,N-二甲基-N-乙基-蓖麻油酸酰胺丙基溴化铵的抑菌活性略强于N,N-二甲基-N-苄基-蓖麻油酸酰胺丙基溴化铵。 相似文献