全文获取类型
收费全文 | 11075篇 |
免费 | 586篇 |
国内免费 | 114篇 |
专业分类
电工技术 | 80篇 |
综合类 | 452篇 |
化学工业 | 5092篇 |
金属工艺 | 176篇 |
机械仪表 | 203篇 |
建筑科学 | 411篇 |
矿业工程 | 49篇 |
能源动力 | 39篇 |
轻工业 | 4101篇 |
水利工程 | 30篇 |
石油天然气 | 112篇 |
武器工业 | 40篇 |
无线电 | 211篇 |
一般工业技术 | 640篇 |
冶金工业 | 64篇 |
原子能技术 | 4篇 |
自动化技术 | 71篇 |
出版年
2024年 | 78篇 |
2023年 | 116篇 |
2022年 | 219篇 |
2021年 | 264篇 |
2020年 | 265篇 |
2019年 | 289篇 |
2018年 | 275篇 |
2017年 | 277篇 |
2016年 | 284篇 |
2015年 | 318篇 |
2014年 | 421篇 |
2013年 | 861篇 |
2012年 | 625篇 |
2011年 | 657篇 |
2010年 | 496篇 |
2009年 | 489篇 |
2008年 | 457篇 |
2007年 | 655篇 |
2006年 | 673篇 |
2005年 | 583篇 |
2004年 | 543篇 |
2003年 | 461篇 |
2002年 | 383篇 |
2001年 | 325篇 |
2000年 | 244篇 |
1999年 | 237篇 |
1998年 | 232篇 |
1997年 | 161篇 |
1996年 | 155篇 |
1995年 | 156篇 |
1994年 | 125篇 |
1993年 | 122篇 |
1992年 | 120篇 |
1991年 | 53篇 |
1990年 | 36篇 |
1989年 | 36篇 |
1988年 | 17篇 |
1987年 | 24篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1964年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Food Control》2015
A diverse range of genetic elements has been used to develop genetically modified organisms (GMOs) over the last 18 years. Screening methods that target few elements, such as the Cauliflower Mosaic Virus 35S promoter (P-35S) and Agrobacterium tumefaciens nopaline terminator (T-nos), are not sufficient to screen GMOs. In the present study, a multiplex PCR system for all globally commercialized GM soybean events was developed to easily trace the events. For this purpose, screening elements of 24 GM soybean events were investigated and 9 screening targets were selected and divided into three individual triplex PCR systems: P-35S, ribulose-1,5-bisphosphate carboxylase small subunit promoter of Arabidopsis thaliana, T-nos, T-35S, pea E9 terminator, open reading frame 23 terminator of A. tumefaciens, proteinase inhibitor II terminator of potato, acetohydroxy acid synthase large subunit terminator of A. thaliana, and the revealed 3′ flanking sequences of DP-305423-1. The specificity of the assays was confirmed using thirteen GM soybean events as the respective positive/negative controls. The limit of detection of each multiplex set, as determined using certified reference materials of specific GM events, ranged from 0.03 to 0.5%, depending upon target. Furthermore, 26 food samples that contained soybean ingredients, which were purchased from the USA, China, Japan, and Korea, were analyzed, 17 of which contained one or more GM soybean events. These results suggest that the developed screening method can be used to efficiently track and identify 24 GM soybean events in food and feed. 相似文献
2.
Inhibition of Spore Germination of Phakopsora Pachyrhizi Using Crude Extracts of Amaranthus Spinosus
The effectiveness of methanolic and n-hexane crude extracts of Amaranthus spinosus to inhibit the spore germination of Phakopsora pachyrhizi, a causal agent of soybean rust disease was studied. Both methanolic and n-hexane crude extracts inhibited spore germination at concentrations of 0.1% to 5.0%. Methanolic extract of the roots at a concentration of 2.5% inhibited 55% of spore germination, and this result was similar when higher concentration at 5% of methanolic and n-hexane extracts of the flowers was used. The presence of alkaloids, flavonoids, tannins, saponins, and terpenoids in the extract may be responsible for the inhibition. The extract was potential to be utilized as a botanical fungicide. 相似文献
3.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
4.
研究了某种环氧树脂阻尼灌封胶在热氧老化的作用下分子结构、硬度、断面形貌以及动态力学性能随时间的变化.傅立叶红外光谱图表明,所制备的样品环氧基团反应比较完全,热氧老化后试样表面由仲胺和环氧基团形成的酯键发生了部分断裂和氧化;邵氏硬度的增加、瓦向高温区移动则表明在老化过程中复杂的固化反应仍然继续进行;最大损耗因子(tanδmax)波动较小表明试样老化后分子结构几乎保持不变;SEM图片显示试样的冲击断裂由老化前的韧性转变为老化后的脆性断裂. 相似文献
5.
6.
L. T. MO M. HUURMAN S. P. WU A. A. A. MOLENAAR 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(9):823-831
Tensile fatigue behaviours of bitumen–stone adhesion were investigated using a dynamic mechanics analyser under stress‐controlled mode at two temperatures of 5 and 25°C and various controlled‐stress levels. Failure characteristics including interfacial failure and cohesive failure were examined using image analysis of fracture surfaces. Finite‐element analysis on stress distributions was conducted under different temperatures, film thickness and interfacial bonding conditions. A Coulomb–Mohr like criterion in combination with shear and normal stresses is proposed to deal with the extreme thin adhesive layer, which can be further simplified into an adhesive zone without significant loss of accuracy for stress analysis. 相似文献
7.
PMMA/PBA乳胶IPN阻尼材料的研究 总被引:3,自引:0,他引:3
用乳液聚合方法合成了一系列的互穿聚合物网络,其中包括:PMMA/PBA和P(MMA-co-PMA)/PBA乳胶互穿聚合物网络(LIPN),PMMA/PBA乳胶双向互穿聚合物网络(LBIPN)以及PMMA/PBA界面交联互穿聚合物网络(ICLIPN)。动态力学谱和拉伸试验结果表明:(1)PMMA/PBA互穿聚合物网络的两组分相容性和阻尼性能可通过MMA和PMA共聚来改善;(2)双向互穿技术是一种行之 相似文献
9.
10.