全文获取类型
收费全文 | 20968篇 |
免费 | 1706篇 |
国内免费 | 956篇 |
专业分类
电工技术 | 1048篇 |
技术理论 | 4篇 |
综合类 | 1386篇 |
化学工业 | 3967篇 |
金属工艺 | 1259篇 |
机械仪表 | 1186篇 |
建筑科学 | 1542篇 |
矿业工程 | 556篇 |
能源动力 | 524篇 |
轻工业 | 1292篇 |
水利工程 | 338篇 |
石油天然气 | 1318篇 |
武器工业 | 120篇 |
无线电 | 2377篇 |
一般工业技术 | 2683篇 |
冶金工业 | 1064篇 |
原子能技术 | 216篇 |
自动化技术 | 2750篇 |
出版年
2024年 | 90篇 |
2023年 | 385篇 |
2022年 | 553篇 |
2021年 | 789篇 |
2020年 | 631篇 |
2019年 | 553篇 |
2018年 | 583篇 |
2017年 | 675篇 |
2016年 | 549篇 |
2015年 | 762篇 |
2014年 | 930篇 |
2013年 | 1177篇 |
2012年 | 1252篇 |
2011年 | 1329篇 |
2010年 | 1235篇 |
2009年 | 1247篇 |
2008年 | 1139篇 |
2007年 | 1117篇 |
2006年 | 1092篇 |
2005年 | 995篇 |
2004年 | 676篇 |
2003年 | 659篇 |
2002年 | 688篇 |
2001年 | 557篇 |
2000年 | 525篇 |
1999年 | 639篇 |
1998年 | 517篇 |
1997年 | 426篇 |
1996年 | 390篇 |
1995年 | 341篇 |
1994年 | 301篇 |
1993年 | 200篇 |
1992年 | 158篇 |
1991年 | 130篇 |
1990年 | 79篇 |
1989年 | 102篇 |
1988年 | 57篇 |
1987年 | 30篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Isolation and evaluation of endophytic Streptomyces endus OsiSh‐2 with potential application for biocontrol of rice blast disease 下载免费PDF全文
994.
995.
Zhen Zeng Tong Lyu Xin Jia Yue Chen Yingmin Lyu 《International journal of molecular sciences》2022,23(8)
During the growth cycle of lilies, assimilates undergo a process of accumulation, consumption and reaccumulation in bulbs and are transported and allocated between aboveground and underground organs and tissues. The sink–source relationship changes with the allocation of assimilates, affecting the vegetative growth and morphological establishment of lilies. In this study, the carbohydrate contents in different tissues of five critical stages during lily development were measured to observe the assimilates allocation. The results showed bulbs acted as the main source to provide energy before the budding stage (S3); after the flowering stage (S4), bulbs began to accumulate assimilates as a sink organ again. During the period when the plant height was 30cm with leaf-spread (S2), leaves mainly accumulated assimilates from bulbs through the symplastic pathway, while when leaves were fully expanded, it transformed to export carbohydrates. At the S4 stage, flowers became a new active sink with assimilates influx. To further understand the allocation of assimilates, 16 genes related to sugar transport and metabolism (ST genes) were identified and categorized into different subfamilies based on the phylogenetic analysis, and their protein physicochemical properties were also predicted. Tissue-specific analysis showed that most of the genes were highly expressed in stems and petals, and it was mainly the MST (monosaccharide transporter) genes that were obviously expressed in petals during the S4 stage, suggesting that they may be associated with the accumulation of carbohydrates in flowers and thus affect flower development process. LoSWEET14 (the Sugar will eventually be exported transporters) was significantly correlated with starch in scales and with soluble sugar in leaves. Sugar transporters LoHXT6 and LoSUT1 were significantly correlated with soluble sugar and sucrose in leaves, suggesting that these genes may play key roles in the accumulation and transportation of assimilates in lilies. In addition, we analyzed the expression patterns of ST genes under different abiotic stresses, and the results showed that all genes were significantly upregulated. This study lays a solid foundation for further research on molecular mechanism of sink–source change and response to abiotic stresses in lilies. 相似文献
996.
The total polyphenol content and the antioxidant activity of kudingcha made from Ilex kudingcha C.J. Tseng were determined by Folin–Ciocalteu reagent, and DPPH, FRAP, and TEAC methods, respectively. The crude extract (CE) of kudingcha and its four fractions of chloroform (CfF), ethyl acetate (EaF), n-butanol (nBF), and water (WtF) were prepared and subjected to antioxidant evaluation and analysis by high performance liquid chromatography. The extracts of kudingcha contained large amounts of caffeoylquinic acid (CQA) derivatives, including 3-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA, and showed potent antioxidant activity. The antioxidant activities of CE and its fractions decreased in the order of EaF > nBF > CE > WtF > CfF, according to the DPPH assay and FRAP assay, which were the same, with the exception of the rank order of CfF and WtF, as the TEAC assay. Furthermore, a satisfactory correlation between total polyphenol content and antioxidant activity was observed. 相似文献
997.
针对同步闪蒸汽提发酵新过程,开发了侧环式反应器,并采用混合模型,利用计算流体力学(CFD)技术模拟了侧环式反应器气液两相的流场.模拟结果表明,侧环具有脱气作用,随着通气量增大,气液两相接触变差,传质效果下降,这与实验现象一致. 相似文献
998.
999.
食品的低温高压处理技术及其研究进展 总被引:7,自引:0,他引:7
文中介绍了低温高压处理技术的基本原理、应用范围和研究进展。在 0~ 6 32 4MPa范围内 ,高压下水的冻结点均较常压下的低 ,并在低于 0℃的温度下形成一个水的不冻结区域。高压还使水的体积收缩、温度升高。低温高压处理技术可应用于食品杀菌和抑酶、高压冻结和高压解冻、低温高压不冻结贮藏。低温高压具有比常温高压更好的杀菌效果 ;高压冻结和高压解冻可缩短食品冻结和解冻的时间、改善冻藏食品的品质 ;低温高压下的不冻结贮藏能更好地保持食品原有的风味和质地 相似文献
1000.
为了提高木薯淀粉的发酵产脂能力,采用正交实验和均匀设计法对木薯淀粉酶法水解工艺进行了优化,结果表明α-淀粉酶量、糖化酶量和液化温度对木薯淀粉水解有显著影响。当淀粉酶量为756 U/g,糖化酶量为602 U/g,液化温度为92°C,其水解DE值达到97.3%。以该水解液进行皮状丝胞酵母B3(T.cutaneum B3)油脂发酵时,其生物量和油脂产量分别为16.38 g/L和7.22 g/L,比葡萄糖作为碳源的生物量和油脂产量高46.25%和41.12%,利用木薯淀粉水解液作为新型发酵碳源生产微生物油脂是一种理想的途径。 相似文献