全文获取类型
收费全文 | 1576篇 |
免费 | 142篇 |
国内免费 | 111篇 |
专业分类
电工技术 | 14篇 |
综合类 | 68篇 |
化学工业 | 554篇 |
金属工艺 | 352篇 |
机械仪表 | 34篇 |
建筑科学 | 13篇 |
矿业工程 | 39篇 |
能源动力 | 30篇 |
轻工业 | 28篇 |
水利工程 | 2篇 |
石油天然气 | 79篇 |
武器工业 | 15篇 |
无线电 | 40篇 |
一般工业技术 | 194篇 |
冶金工业 | 179篇 |
原子能技术 | 154篇 |
自动化技术 | 34篇 |
出版年
2024年 | 7篇 |
2023年 | 31篇 |
2022年 | 44篇 |
2021年 | 61篇 |
2020年 | 60篇 |
2019年 | 55篇 |
2018年 | 61篇 |
2017年 | 65篇 |
2016年 | 47篇 |
2015年 | 64篇 |
2014年 | 73篇 |
2013年 | 167篇 |
2012年 | 119篇 |
2011年 | 101篇 |
2010年 | 65篇 |
2009年 | 90篇 |
2008年 | 61篇 |
2007年 | 100篇 |
2006年 | 77篇 |
2005年 | 72篇 |
2004年 | 65篇 |
2003年 | 47篇 |
2002年 | 59篇 |
2001年 | 46篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1976年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有1829条查询结果,搜索用时 15 毫秒
61.
《分离科学与技术》2012,47(9):2022-2040
Abstract 3-Phenyl-4-benzoyl-5-isoxazolone (HPBI) was synthesized and examined with regard to the synergistic solvent extraction behavior of zirconium(IV) and hafnium(IV) in the presence of various crown ethers (CEs), namely, 18-crown-6 (18C6), dicylohexano-18-crown-6 (DC18C6) and benzo-15-crown-5 (B15C5) from hydrochloric acid solutions. The results demonstrated that zirconium(IV) and hafnium(IV) were synergistically extracted into chloroform with mixtures of HPBI and CEs as ZrO(PBI)2 · CE and HfO(PBI)2 · CE, respectively. The complexation strength follows the order DC18C6 >18C6 > B15C5. The addition of CEs not only enhances the extraction efficiency of zirconium(IV) and hafnium(IV) but also significantly, especially in the presence of B15C5, improves the selectivity (Zr/Hf = 4.73) between these metal ions as compared to HPBI alone (Zr/Hf = 2.09). On the other hand, selectivity has been moderately decreased by the addition of 18C6 or DC18C6 to the metal-chelate system. 相似文献
62.
硫酸锆催化合成丁酸异戊酯的研究 总被引:10,自引:0,他引:10
以硫酸锆催化剂催化合成了丁酸异戊酯,确定了酯化反应优化条件。实验结果表明,催化剂的催化活性高,反应条件温和,方法复合,收率优良,催化剂可再生重复使用。 相似文献
63.
64.
以石油生焦为原料,硫酸和硝酸的混合酸为氧化剂,通过化学氧化制得炭质水性中间相,将炭质水性中间相于丙酮溶剂中浸泡7d形成炭质溶胶,然后用乙醇洗涤脱出其中的丙酮溶剂得到炭质醇溶胶,再将炭质醇溶胶与锆醇溶胶进行混合制得二元醇溶胶,随后进行超临界流体干燥得到二元气凝胶,二元气凝胶具有疏松的表观结构,由尺寸为3-15nm的颗粒组成,采用二元炭质-二氧化锆气凝胶前驱体,经氩气气氛下的碳热还原合成了Zr(C,O)纳米粉体,并采用XRD和TEM等分析测试技术和化学分析对二元气凝胶和由其制中得的Zr(C,O)纳米粒子的表面形貌和结构进行了表征,结果表明,前驱体制备工艺中,合成温度对Zr(C,O)的结构和化学组成性能有较大的影响。 相似文献
65.
Dongsen Mao Guanzhong Lu Qingling Chen Zaiku Xie Yuxian Zhang 《Catalysis Letters》2001,77(1-3):119-124
A series of boria catalysts supported on titania–zirconia mixed oxide (B2O3/TiO2–ZrO2) with different boria loadings (8–20 wt%) were prepared and characterized by X-ray diffraction, adsorption of nitrogen, 11B magic angle spinning (MAS) NMR measurements and temperature-programmed desorption (TPD) of ammonia. The catalytic performance of B2O3/TiO2–ZrO2 for vapor-phase Beckmann rearrangement of cyclohexanone oxime to -caprolactam was studied at 300°C. It was found that the lactam selectivity increased with increasing of boria loading, whereas a maximum oxime conversion was obtained at the boria loading of 12 wt%. The acid sites of medium strength on the surface of the catalyst play an important role in the selective formation of lactam. 相似文献
66.
Federica Bondioli Anna Maria Ferrari Cristina Leonelli Cristina Siligardi Gian Carlo Pellacani 《Journal of the American Ceramic Society》2001,84(11):2728-2730
Nanosized zirconium oxide (ZrO2 ) powders were prepared by adding NaOH to a zirconyl chloride aqueous solution under microwave-hydrothermal conditions. The obtained results showed that the tetragonal polymorph increased with increasing NaOH concentration in the starting solution and reached the maximum value by using 1 M ZrOCl2 . The microwave-assisted hydrothermal synthesis is expected to be able to process continuously, and may lead to energy savings because of rapid heating to temperature and increased kinetics of crystallization. This method is very simple and can lead to powders with desirable characteristics such as very fine size, narrow size distribution, and good chemical homogeneity. 相似文献
67.
68.
《分离科学与技术》2012,47(9):1341-1344
The weight distribution coefficients (λM) of the most often occurring in zirconium salts ions (M(II), M(III) and M(IV)) have been determined in established earlier optimal conditions for separation of zirconium from hafnium by means of Diphonix® resin. Their values range from 21 (λZn(II)) to 1830 (λTi(IV)) and depend on the charge of M ion as well as on its radius. For ions of the highest λM (Ti(IV) and Fe(III)) their influence on hafnium – zirconium separation has been studied. Ti(IV) ions at concentration of 1% (in relation to Zr) has been found to noticeably affect separation of hafnium from zirconium by means of Diphonix® resin. 相似文献
69.
《分离科学与技术》2012,47(14):2140-2149
Hybrid ion-exchangers have been synthesized by modification of strongly acidic cation-exchange resin with zirconium hydrophosphate. The samples were investigated with scanning and transmission electron microscopy and standard contact porosimetry. Single nanoparticles and their aggregates have been found in the polymer. The nanoparticles in transport pores increase the electrical conductivity of ion-exchanger from 0.21 to 0.65 Ohm?1 m?1. The diffusion coefficient of Cd2+ ions reaches 2.43 × 10?11 m2 s?1 for initial resin and (2.50–4.34) × 10?11 m2 s?1 for nanocomposites. The inorganic constituent improves Cd2+ recovery from a solution, which contains also Ca2+ and Mg2+. The degree of Cd2+ removal is 18% for non-modified resin and 99% for the sample containing 38 mass% zirconium phosphate. 相似文献
70.
《Ceramics International》2020,46(12):19822-19826
Sodium Zirconium Phosphate (NaZr2(PO4)3, hereinafter NZP) and monazite are both potential materials for immobilization of nuclear waste. In this work, novel (1-x)Sr0.5Zr2(PO4)3-xNdPO4 composite ceramics (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) for simultaneously immobilizing the simulated fission product (FP) Sr and trivalent minor actinide (MA) Nd were prepared by one-step microwave sintering technique, in which Sr and Nd were immobilized into NZP and monazite type structures, respectively. The phase evolution and microstructure of the samples were investigated by X-ray diffraction (XRD), Raman, and backscattering scanning electron microscopy (BSE). The results showed that the expected composite ceramics were successfully obtained by one-step microwave sintering at 1050 °C for 2 h. The as-prepared samples consisted of Sr0.5Zr2(PO4)3 and NdPO4 phases, and the content of the two phases varied regularly as x changed, generally conforming to the designed nominal chemical composition. Importantly, the composite ceramics presented the homogenous and dense microstructure. The relative density of the composite ceramics was more than 95%, meanwhile, the Vickers-hardness of the samples was higher than 600 MPa. It was indicated that NZP-monazite type composite ceramics could be a potential matrix for the simultaneous immobilization of actinide and fission product. 相似文献