全文获取类型
收费全文 | 40966篇 |
免费 | 3111篇 |
国内免费 | 1906篇 |
专业分类
电工技术 | 2083篇 |
技术理论 | 3篇 |
综合类 | 5056篇 |
化学工业 | 5014篇 |
金属工艺 | 1476篇 |
机械仪表 | 1493篇 |
建筑科学 | 6638篇 |
矿业工程 | 2577篇 |
能源动力 | 1159篇 |
轻工业 | 3407篇 |
水利工程 | 2333篇 |
石油天然气 | 2308篇 |
武器工业 | 175篇 |
无线电 | 2189篇 |
一般工业技术 | 3360篇 |
冶金工业 | 2700篇 |
原子能技术 | 358篇 |
自动化技术 | 3654篇 |
出版年
2024年 | 164篇 |
2023年 | 549篇 |
2022年 | 953篇 |
2021年 | 1144篇 |
2020年 | 1035篇 |
2019年 | 950篇 |
2018年 | 842篇 |
2017年 | 1003篇 |
2016年 | 1139篇 |
2015年 | 1256篇 |
2014年 | 2156篇 |
2013年 | 2006篇 |
2012年 | 2555篇 |
2011年 | 2774篇 |
2010年 | 2197篇 |
2009年 | 2370篇 |
2008年 | 2142篇 |
2007年 | 2833篇 |
2006年 | 2584篇 |
2005年 | 2367篇 |
2004年 | 1990篇 |
2003年 | 1845篇 |
2002年 | 1581篇 |
2001年 | 1345篇 |
2000年 | 1131篇 |
1999年 | 923篇 |
1998年 | 648篇 |
1997年 | 552篇 |
1996年 | 480篇 |
1995年 | 450篇 |
1994年 | 342篇 |
1993年 | 287篇 |
1992年 | 232篇 |
1991年 | 150篇 |
1990年 | 172篇 |
1989年 | 146篇 |
1988年 | 121篇 |
1987年 | 94篇 |
1986年 | 66篇 |
1985年 | 59篇 |
1984年 | 50篇 |
1983年 | 24篇 |
1982年 | 24篇 |
1981年 | 33篇 |
1980年 | 28篇 |
1979年 | 31篇 |
1977年 | 17篇 |
1976年 | 18篇 |
1975年 | 20篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
32.
33.
Three-dimensionally ordered long-range macroporous carbon structures were prepared using commercially available phenolic resin
by utilizing sacrificial colloidal silica crystalline arrays as templates that were subsequently removed by HF etching after
pyrolysis in an argon atmosphere. SEM, TEM, and BET were employed to characterize the morphology and the surface area of the
porous carbon structures. The pore size (150–1000 nm) and BET surface area, which reflect pore volume (298.6 m2/g (1.32 cm3/g) ∼ 93.7 m2/g (0.12 cm3/g)), of the macroporous carbon structures produced were approximately proportional to the size (150–1000 nm) of the sacrificial
silica sphere templates used (annealing temp. 550°C). The achieved 550 nm porous carbon structures were examined to function
as potential catalyst carriers and were successfully impregnated with Ag or Pt-Ru on their inner walls after borohydride reduction
at room temperature. In addition, porous carbon patterns were fabricated using the ‘micromolding in capillary’ technique,
which has potential applications in the microreaction technology. 相似文献
34.
TESTS FOR FRACTIONAL INTEGRATION:A MONTE CARLO INVESTIGATION 总被引:1,自引:0,他引:1
Abstract. The performance of the Geweke-Porter-Hudak (GPH) test, the modified rescaled range (MRR) test and two Lagrange multiplier (LM) type tests for fractional integration in small samples is examined using Monte Carlo methods. Both the GPH and MRR tests are found to be robust to moderate autoregressive moving-average components, autoregressive conditional heteroskedasticity effects and shifts in the variance. However, these two tests are sensitive to large autoregressive moving-average components and shifts in the mean. It is also found that the LM tests are sensitive to deviations from the null hypothesis. As an illustration, the GPH test is applied to two economic data series. 相似文献
35.
Yury V. Kissin 《Catalysis Letters》1993,19(2-3):181-187
An experimental technique is discussed for measuring relative reactivities of alkanes in the catalytic cracking of multi-component hydrocarbon mixtures over a heterogeneous, Y-zeolitebased catalyst at 250–350 °C. With the technique, ca. 0.1 l of an alkane mixture is evaporated and contacted with a catalyst, after which the mixture of reaction products and the unreacted feed enters the chromatographic column and is immediately analyzed. The technique is used to measure relative reactivities of 21 alkanes in a single experiment. The principal results of these experiments are similar to the results of single-component cracking: alkane reactivity rapidly increases with the increase of the carbon number, and methyl-branched alkanes are more reactive than linear alkanes. However, the variations in alkane reactivities as a function of their molecular weight and skeleton structure differ very significantly between single- and multicomponent experiments. 相似文献
36.
洪旭斌 《四川烹饪高等专科学校学报》2010,(3):67-69
潮汕地区是指粤东地区以讲潮州方言为主的区域,主要包括汕头、潮州和揭阳三个地区。近年来潮汕地区发展缓慢,这与人才相对匮乏不无关系,本文分析了潮汕企业人才现状,并提出了相应的对策。 相似文献
37.
针对目前某工厂主厂道由于受到重交通作用而造成水泥混凝土路面损坏严重的现状,笔者先从水泥混凝土路面主要病害的种类及其产生的原因着手加以分析,进而对在旧路面上半直接式加铺水泥混凝土和钢纤维水泥混凝施工技术进行了介绍和总结. 相似文献
38.
Changes in the liquid hold-up, ?, and the diameter of d, of a foam that are induced by perforated plates (PPs) and the contribution of PPs to foam-breaking were studied. A foaming system containing a dilute detergent solution in a column with mechanical agitation fitted with a rotating-disk foam-breaker (MFRD) was used. After the foam passed through the PPs, ? and d decreased and increased, respectively. The use of PPs to achieve a maximum reduction in ? and a maximum increase in d is confirmed. It is also demonstrated that use of PPs contributes not only to improving the foam-breaking performance of the MFRD, but also to power savings. 相似文献
39.
曹霞 《湖南纺织高等专科学校学报》2014,(1):34-38
在诗歌翻译中,译文会因为译者的不同在风格上表现出差异.然而,译文的质量不外乎经受形美、音美和意美的考量.译者应从本国读者的文化背景上结合时代的脉搏来进行“再创造”,做到形式、音律和意蕴的完美统一.歌德的诗歌《中德四季晨昏杂咏》(之八)的四种中文译本各有特色,均在不同程度上实现了“三美”的融合. 相似文献
40.
D. Banerjee G. K. Lai G. S. Upadhyaya 《Journal of Materials Engineering and Performance》1995,4(5):563-572
For production of fine-grained and corrosion-resistant tungsten carbide (WC) based cemented carbides, addition of chromium
carbide (Cr33C2) in small amounts is standard practice. No systematic study, however, has been made of the effects of large additions (maximum
6 wt % ) of Cr3C2 as a substitute for tungsten carbide. This study focuses on the effect of hard-phase substitution by C3C2 in WC-1OCo cemented carbide. An attempt is also made to modify the binder metal cobalt by partial or complete substitution
of nickel. Specimens were prepared using the standard liquid-phase sintering process and were tested for sintered porosity,
mechanical properties, corrosion resistance, and microstructural parameters. Results confirm the findings of earlier workers
regarding grain refinement and improvement of mechanical properties upon the addition of small amounts (<2 wt%) of Cr3C2. Modification of the binder phase improves indentation fracture toughness and corrosion resistance. Addition of Cr3C2 independent of the binder type improves corrosion resistance. 相似文献