全文获取类型
收费全文 | 28883篇 |
免费 | 1597篇 |
国内免费 | 726篇 |
专业分类
电工技术 | 1698篇 |
综合类 | 3007篇 |
化学工业 | 8086篇 |
金属工艺 | 1250篇 |
机械仪表 | 1893篇 |
建筑科学 | 1240篇 |
矿业工程 | 1119篇 |
能源动力 | 616篇 |
轻工业 | 1604篇 |
水利工程 | 337篇 |
石油天然气 | 2884篇 |
武器工业 | 160篇 |
无线电 | 1758篇 |
一般工业技术 | 1276篇 |
冶金工业 | 1803篇 |
原子能技术 | 282篇 |
自动化技术 | 2193篇 |
出版年
2024年 | 36篇 |
2023年 | 138篇 |
2022年 | 352篇 |
2021年 | 457篇 |
2020年 | 397篇 |
2019年 | 280篇 |
2018年 | 432篇 |
2017年 | 546篇 |
2016年 | 518篇 |
2015年 | 507篇 |
2014年 | 1729篇 |
2013年 | 1386篇 |
2012年 | 2049篇 |
2011年 | 1360篇 |
2010年 | 1331篇 |
2009年 | 1616篇 |
2008年 | 1675篇 |
2007年 | 2637篇 |
2006年 | 2909篇 |
2005年 | 2143篇 |
2004年 | 1152篇 |
2003年 | 1401篇 |
2002年 | 1025篇 |
2001年 | 884篇 |
2000年 | 834篇 |
1999年 | 735篇 |
1998年 | 532篇 |
1997年 | 398篇 |
1996年 | 317篇 |
1995年 | 261篇 |
1994年 | 208篇 |
1993年 | 166篇 |
1992年 | 128篇 |
1991年 | 107篇 |
1990年 | 72篇 |
1989年 | 55篇 |
1988年 | 59篇 |
1987年 | 51篇 |
1986年 | 42篇 |
1985年 | 67篇 |
1984年 | 47篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 17篇 |
1980年 | 28篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
崔忠兴 《腐蚀科学与防护技术》1994,6(4):361-363
油井缓蚀剂研究与应用崔忠兴(中原油田设计院,濮阳457001)1.前言中原油田已进入高含水期,油井系统腐蚀严重,直接影响了油田的正常生产l’].为了解决油井系统腐蚀问题,在中科院腐蚀所的专种“基础f,联合开发研制了!MC—SDeZS油井缓蚀剂.该剂以合成炔氧甲基胺和炔氧甲基季法盐衍生物,以这两种衍生物为主体成分复配辅助成分而成的水溶油分散吸附成股型缓蚀剂l’1.通过室内高温高压模拟评价试验.ZI口油井加药试验及测试表明l‘],平?... 相似文献
192.
本文研究了纳米CaCO3表面改性的影响因素,确定了最优改性剂和改性条件,并运用沉降实验、透射电镜(TEM)等表征手段对粉体的改性效果进行了分析。结果表明:以月桂酸钠为改性剂,用量为10%,pH值为7,改性时间为1h时,改性后的纳米CaCO3的亲油化度达到85.1%,能较好地分散于环己烷和二甲苯中。 相似文献
193.
194.
195.
J. R. Clearwater S. P. Foster S. J. Muggleston J. S. Dugdale E. Priesner 《Journal of chemical ecology》1991,17(2):413-429
The specific status ofCtenopseustis obliquana pheromone-types I, II, and III has been more fully examined. Females of types I and III produce a mixture of (Z)-8- and (Z)-5-tetradecenyl acetates (Z8-14:Ac, Z5-14: Ac). The previously reported different ratios of these two components in females of the two types (type I=8020, III=9010) have been reinvestigated. The median ratios of each type differed significantly, although there was some overlap in the ranges of these ratios. A field cage trial showed that males of type III are attracted to females of type I, so the observed differences may be ascribed to intraspecific variation. In contrast to females of types I or III, females of type II produce Z5-14Ac but no Z8-14Ac. The electroantennogram (EAG) profile of antennae of type II males shows a maximum response to Z5-14Ac, while the EAG profiles of types I and III show a strong response to Z8-14Ac. In wind tunnel tests using mixtures of these two compounds, type II males prefer blends consisting of all or mostly Z5-14: Ac, while type I males showed a preference to a mix of 70% Z8-14Ac plus 30% Z5-14Ac. We found that type I males are attracted to type I females when offered a choice between type I and type II females in a field cage test and that type II males similarly prefer type II females. Males of types I and II have specialist cells for Z8-14Ac and Z5-14Ac but differ with respect to relative densities of these cells and to further cell types responsive to other alkenyl acetates. Type IIC. obliquana is considered therefore a sibling species of types I and III. In addition, the amount of Z5-14Ac produced by type II females varied geographically. Females from the North Island produced significantly less (median=1.2 ng) Z5-14Ac than females from the South Island (median=2.2 ng). Type II populations in the North Island morphologically resembled sympatric type I, rather than type II from the South Island and are designated as type II (North Island). Type II (North Island) populations have so far been found only at Rukuhia (near Hamilton) and from Kerikeri. In contrast, type II populations are sympatric with type III populations over much of the South Island. In a field cage trial, males of types II and II (North Island) were attracted to females of both II and II (North Island). We tentatively ascribe the differences between type II and type II (North Island) to intraspecific variation. 相似文献
196.
Amy?Richards Chakra?WijesunderaEmail author Phil?Salisbury 《Journal of the American Oil Chemists' Society》2005,82(12):869-874
Lipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore
an important criterion by which oils are judged for usefulness in various food applications. In this study a method based
on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the
use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison
with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected
to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC-MS.
Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile
lipid oxidation products hexanal and trans,trans-2,4-heptadienal. The PV calculated using this formula correlated (R
2=0.73) with those measured by conventional methods.
Presented in part at the 96th Annual Meeting of the AOCS, 1–4 May 2005, Salt Lake City, UT. 相似文献
197.
哈氏合金设备的设计与施工 总被引:3,自引:0,他引:3
介绍哈氏合金的类型及耐腐蚀性能,从设计、成型、焊接和机械加工等方 面提出了制造哈氏合金设备的有关注意事项。 相似文献
198.
改性丙烯酸-环氧树脂纳米乳液的制备及应用 总被引:1,自引:0,他引:1
介绍了水性丙烯酸-环氧树脂纳米乳液的制备及其在油罐防腐工程中的应用。讨论了亲水侧链聚乙二醇相对分子质量大小对涂膜性能的影响以及乳化剂各组分的用量对乳液粒径的影响。 相似文献
199.
200.