全文获取类型
收费全文 | 15284篇 |
免费 | 2295篇 |
国内免费 | 973篇 |
专业分类
电工技术 | 199篇 |
综合类 | 1004篇 |
化学工业 | 6846篇 |
金属工艺 | 998篇 |
机械仪表 | 325篇 |
建筑科学 | 649篇 |
矿业工程 | 344篇 |
能源动力 | 937篇 |
轻工业 | 597篇 |
水利工程 | 211篇 |
石油天然气 | 724篇 |
武器工业 | 77篇 |
无线电 | 1072篇 |
一般工业技术 | 3663篇 |
冶金工业 | 637篇 |
原子能技术 | 122篇 |
自动化技术 | 147篇 |
出版年
2024年 | 78篇 |
2023年 | 448篇 |
2022年 | 509篇 |
2021年 | 693篇 |
2020年 | 648篇 |
2019年 | 646篇 |
2018年 | 609篇 |
2017年 | 716篇 |
2016年 | 669篇 |
2015年 | 684篇 |
2014年 | 839篇 |
2013年 | 1019篇 |
2012年 | 1027篇 |
2011年 | 1073篇 |
2010年 | 709篇 |
2009年 | 897篇 |
2008年 | 727篇 |
2007年 | 906篇 |
2006年 | 858篇 |
2005年 | 741篇 |
2004年 | 640篇 |
2003年 | 594篇 |
2002年 | 483篇 |
2001年 | 431篇 |
2000年 | 425篇 |
1999年 | 251篇 |
1998年 | 188篇 |
1997年 | 174篇 |
1996年 | 150篇 |
1995年 | 120篇 |
1994年 | 101篇 |
1993年 | 67篇 |
1992年 | 97篇 |
1991年 | 74篇 |
1990年 | 82篇 |
1989年 | 79篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1959年 | 3篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
拒水粉是一种新型建筑防水材料,被称之为神奇的粉末。本文就如何利用粉体表面改性技术制备拒水粉,从理论上和具体的实验方法上作了详尽的说明。 相似文献
92.
轻质高效保温材料掺杂硅气凝胶 总被引:3,自引:0,他引:3
利用正硅酸甲脂(TMOS)为原料的溶胶-凝胶过程,摸索了不同反应条件下形成凝胶的规律,并选用TiO2粉末及玻璃纤维作为掺杂剂,采用超临界干燥处理制备出掺TiO2的硅气凝胶,通过对红外光谱以及不同温度和气压条件下热导率的测量,讨论了不同成份配比以及相应的热传输过程对材料热导率的影响。结果表明,密度为260kg/m^3的掺杂硅气凝胶在800K时的热导率为0.038w/m.k,是一种新型的轻质高效保温材 相似文献
93.
掺富勒烯SiO2气凝胶的制备与发光性质研究 总被引:3,自引:0,他引:3
本文利用溶胶-凝胶工艺成功地将富勒烯掺入了SiO2气凝胶的纳米孔洞中,在Ar^+离子激光激发下,观察到了很强的可见光发射,对该现象作了初步的解释。 相似文献
94.
采用简便方法计算气体通过多孔材料的流量。当层流时,流量与压差按线性关系计算;紊流时,应按幂函数关系计算。本文提出了计算公式。 相似文献
95.
溶胶-凝胶法制备磷钨酸-硅胶催化合成苹果酯 总被引:1,自引:1,他引:0
采用溶胶-凝胶法制备了一系列磷钨酸-硅胶催化剂(PW/SG),考察了该催化剂催化乙酰乙酸乙酯与乙二醇液相缩合制备苹果酯的反应性能。实验结果表明,PW质量分数为40%时的PW/SG催化剂表现出最佳的催化活性;40%PW/SG催化剂制备苹果酯的最佳工艺条件为:n(乙酰乙酸乙酯)∶n(乙二醇)=1∶1.2,催化剂用量占反应物质量的0.36%,带水剂环己烷用量占反应物体积的30%,反应温度383K,反应时间90min;在此条件下,乙酰乙酸乙酯的转化率可达95.5%,苹果酯的选择性大于97%;催化剂稳定性实验表明,经5次重复使用,40%PW/SG催化剂的活性基本保持不变,乙酰乙酸乙酯转化率稳定在95.0%左右。 相似文献
96.
The Biot's acoustics theory, which describes acoustic wave propagation in a porous medium, and computer simulation techniques were utilized to model the behavior of acoustic waves entering and leaving a mixing zone in a miscible displacement in porous media. The results indicate that the angles of waves produced by a mixing zone are equal to angles of waves produced by an abrupt fluid-fluid interface. Therefore, acoustic methods and a relationship between the incident, reflection, and transmission angles can be used to determine the location and thickness of the mixing zone during a miscible displacement process in porous media. 相似文献
97.
Michael W. Anderson 《Topics in Catalysis》1996,3(1-2):195-220
The power of solid-state NMR for the interrogation of porous catalytic materials is illustrated using three examples. First,
for the investigation of catalytic processes occurring within the confines of a microporous catalyst NMR is shown to reveal
both the details of shape-selectivity and the nature of internal surface species. Second, NMR is shown to be a powerful short-range
tool to reveal precise structural information on highly disordered microporous titanosilicates. Despite long-range disorder
the short-range order is maintained and can be easily studied. Finally, the same utility of probing short-range chemical phenomena
is shown to be crucial for the investigation of novel-ordered-amorphous-mesoporous materials known generically as M41S. This
class of material is currently one of the most important with potential catalytic application. 相似文献
98.
An FTIR experiment especially designed to study the growth of an organosilane layer at the interface between a solution and a flat silica surface is presented. High sensitivity is achieved by using the attenuated total reflection (ATR) technique in a liquid flow cell. The ATR crystal, either silicon or germanium, is covered with a very thin silica layer. Chemical reactions of a mono-and a di-hydrolyzable silane with the silica substrate have been investigated. The grafting of a submonolayer of the first reagent has been monitored by following the C-H and SiO-H vibrations. The density of grafted molecules has been estimated and information on the nature of the chemical bonding has been achieved. Evidence for the chain-polymerization of the dihydrolyzable silane at the substrate/solution interface has been inferred from the appearance of a Si-O-Si absorption band. 相似文献
99.
Konstantinos D Demadis 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(6):630-640
Dendrimers have attracted immense attention during the last decade due to their interesting properties both from a basic and an applied research viewpoint. Encapsulation of metal nanoparticles for catalysis, drug delivery and light harvesting are only some applications of dendrimers that are breaking new ground. A novel application of dendrimer technology is described in the present paper that relates to industrial water treatment. Industrial water systems often suffer from undesirable inorganic deposits. These can form either in the bulk or on metallic surfaces, such as heat exchangers or pipelines. Silica (SiO2) scale formation and deposition is a major problem in high‐silica‐containing cooling waters. Scale prevention rather than removal is highly desired. In this paper, benchtop screening tests on various silica inhibition chemistries are reported, with emphasis on materials with a dendrimeric structure. Specifically, the inhibition properties of commercially available STARBURST® polyaminoamide (PAMAM) dendrimers generations 0.5, 1, 1.5, 2, and 2.5 are investigated in detail together with other commonly‐used scale inhibitors. Experimental results show that inhibition efficiency largely depends on structural features of PAMAM dendrimers such as generation number and nature of the end groups. PAMAM dendrimers are effective inhibitors of silica scale growth at 40 ppm dosage levels. PAMAM dendrimers also act as silica nucleators, forming SiO2–PAMAM composites. This occurs because the SiO2 formed by incomplete inhibition interacts with cationic PAMAM‐1 and ‐2. The general scope of silica formation and inhibition in industrial waters is also discussed. Copyright © 2005 Society of Chemical Industry 相似文献
100.
Wu Songping 《Microelectronics Journal》2007,38(1):41-46
The preparation of ultra fine nickel-copper bimetallic powder with two-stage chemical reduction method was investigated. Reductive sugar and hydrazine hydrate were employed as reducing agent in different reductive stage, respectively. Reaction of CuSO4·5H2O with reductive sugar at 70 °C gives cuprous oxide and copper particles, then as-prepared mixture and nickelous hydroxide were reduced by hydrazine hydrate, and nickel-copper powder having excellent dispersibility was prepared. Influences of nickel added on composition and dispersibility of powder were studied. TG/DTG/DTA of nickel-copper powder, which is stable in room temperature, were discussed with thermal analyzer. Relation of nickel content to oxidation temperature was investigated. Ni-Cu bimetallic powder particles have a fully coated structure when nickel content is up to 30%. As-prepared nickel-copper powder was applied in base metal electrode-multilayer ceramic capacitor (BME-MLCC). The end termination has high adhesion force, fairly good densification, low resistivity, excellent solderibility behavior and resistance behavior to soldering. 相似文献