全文获取类型
收费全文 | 28080篇 |
免费 | 4039篇 |
国内免费 | 2204篇 |
专业分类
电工技术 | 3465篇 |
综合类 | 3322篇 |
化学工业 | 2015篇 |
金属工艺 | 762篇 |
机械仪表 | 1752篇 |
建筑科学 | 1612篇 |
矿业工程 | 720篇 |
能源动力 | 457篇 |
轻工业 | 3243篇 |
水利工程 | 544篇 |
石油天然气 | 1908篇 |
武器工业 | 230篇 |
无线电 | 3610篇 |
一般工业技术 | 1792篇 |
冶金工业 | 1144篇 |
原子能技术 | 204篇 |
自动化技术 | 7543篇 |
出版年
2024年 | 76篇 |
2023年 | 414篇 |
2022年 | 801篇 |
2021年 | 917篇 |
2020年 | 925篇 |
2019年 | 855篇 |
2018年 | 764篇 |
2017年 | 875篇 |
2016年 | 1049篇 |
2015年 | 1207篇 |
2014年 | 1686篇 |
2013年 | 1555篇 |
2012年 | 2106篇 |
2011年 | 2290篇 |
2010年 | 1813篇 |
2009年 | 1851篇 |
2008年 | 1990篇 |
2007年 | 2317篇 |
2006年 | 2020篇 |
2005年 | 1690篇 |
2004年 | 1397篇 |
2003年 | 1212篇 |
2002年 | 964篇 |
2001年 | 753篇 |
2000年 | 633篇 |
1999年 | 454篇 |
1998年 | 307篇 |
1997年 | 239篇 |
1996年 | 220篇 |
1995年 | 202篇 |
1994年 | 174篇 |
1993年 | 117篇 |
1992年 | 85篇 |
1991年 | 58篇 |
1990年 | 62篇 |
1989年 | 54篇 |
1988年 | 51篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1965年 | 5篇 |
1961年 | 3篇 |
1959年 | 6篇 |
1957年 | 3篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
介绍了用AC8612气相色谱仪对六个汽油组分馏程分析的应用情况,结果表明:该方法的重复性和准确性都较好,与D86相比,结果满足方法的再现性要求,但对于差值大于3℃的点,应定期进行修正,以使结果更准确,该方法用于炼油厂各装置汽油组分馏出口的日常质量监测分析,可以提高分析效率并减少劳动强度。 相似文献
2.
Magalí Rey-Campos Beatriz Novoa Alberto Pallavicini Marco Gerdol Antonio Figueras 《International journal of molecular sciences》2021,22(6)
Mytimycins are cysteine-rich antimicrobial peptides that show antifungal properties. These peptides are part of the immune network that constitutes the defense system of the Mediterranean mussel (Mytilus galloprovincialis). The immune system of mussels has been increasingly studied in the last decade due to its great efficiency, since these molluscs, particularly resistant to adverse conditions and pathogens, are present all over the world, being considered as an invasive species. The recent sequencing of the mussel genome has greatly simplified the genetic study of some of its immune genes. In the present work, we describe a total of 106 different mytimycin variants in 16 individual mussel genomes. The 13 highly supported mytimycin clusters (A–M) identified with phylogenetic inference were found to be subject to the presence/absence variation, a widespread phenomenon in mussels. We also identified a block of conserved residues evolving under purifying selection, which may indicate the “functional core” of the mature peptide, and a conserved set of 10 invariable plus 6 accessory cysteines which constitute a plastic disulfide array. Finally, we extended the taxonomic range of distribution of mytimycins among Mytilida, identifying novel sequences in M. coruscus, M. californianus, P. viridis, L. fortunei, M. philippinarum, M. modiolus, and P. purpuratus. 相似文献
3.
Targeted editing of intronic-splicing silencer enhancement of SMN2 Exon 7 inclusion by CRISPR/Case 9
LIUCHENG WU YI WANG LILI DU GUIQING JI RUI ZHOU ZEYI ZHAO JUN CHEN SHUNXING ZHU 《Biocell》2021,45(6):1501-1507
Spinal muscular atrophy (SMA) is an autosomal recessive hereditary neuromuscular disease. Exon 7 and 8 of survival of motor neuron 1 (SMN1) gene or only exon 7 homology deletion leads to the failure to produce a full-length SMN gene. The copy number of SMN2 gene with high homology of SMN1 affects the degree of disease and was the target gene for targeting therapy, in which splicing silencer in intron 7 was the key to suppress the inclusion of exon 7. In this study, we projected to use CRISPR/Case 9 for the targeted editing of intronic-splicing silencer (ISS) sequence to promote the inclusion of SMN2 exon 7 and increase the production of SMN2 full-length (FL) gene expression. It happens that there was a protospacer adjacent motif (PAM) at one end of the ISS sequence according to the design of sgRNA. The recombinant vector of sgRNA HSMN2 CRISPR/Case 9 was constructed and transfected into HEK293 cells. Sequencing results showed that the ISS sequence could be edited accurately and targeting in the predicted direction, in which deleting small fragments, inserting small amounts and mutation. Quantitative analysis of RT-PCR products by restriction enzyme of DdeI digestion showed that the FL of SMN2 increased by 8% (P < 0.05). In the primary cultured chondrocytes of SMA mice, in which sgRNA HSMN2 CRISPR/Case9 recombinant vector transfection could increase the SMN2 FL gene by 23% (P < 0.05) and significantly improve SMN protein levels (P < 0.05). CRISPR/Case 9 is an effective tool for gene editing and therapy of hereditary diseases, but it is rarely reported in the treatment of SMA diseases. This study shows that CRISPR/Case 9 was first used for the precision target of ISS sequence editing, which can effectively promote the production of SMN2 FL gene expressions, in which there was an important clinical reference value. 相似文献
4.
Marc De Doncker Chloé De Graeve Dr. Jorick Franceus Dr. Koen Beerens Prof. Vladimír Křen Dr. Helena Pelantová Dr. Ronny Vercauteren Prof. Dr. Tom Desmet 《Chembiochem : a European journal of chemical biology》2021,22(23):3319-3325
The substantial increase in DNA sequencing efforts has led to a rapid expansion of available sequences in glycoside hydrolase families. The ever-increasing sequence space presents considerable opportunities for the search for enzymes with novel functionalities. In this work, the sequence-function space of glycoside hydrolase family 94 (GH94) was explored in detail, using a combined approach of phylogenetic analysis and sequence similarity networks. The identification and experimental screening of unknown clusters led to the discovery of an enzyme from the soil bacterium Paenibacillus polymyxa that acts as a 4-O-β-d -glucosyl-d -galactose phosphorylase (GGalP), a specificity that has not been reported to date. Detailed characterization of GGalP revealed that its kinetic parameters were consistent with those of other known phosphorylases. Furthermore, the enzyme could be used for production of the rare disaccharides 4-O-β-d -glucosyl-d -galactose and 4-O-β-d -glucosyl-l -arabinose. Our current work highlights the power of rational sequence space exploration in the search for novel enzyme specificities, as well as the potential of phosphorylases for rare disaccharide synthesis. 相似文献
5.
6.
7.
8.
《全球能源互联网(英文)》2022,5(6):618-626
A novel image sequence-based risk behavior detection method to achieve high-precision risk behavior detection for power maintenance personnel is proposed in this paper. In this method, the original image sequence data is first separated from the foreground and background. Then, the free anchor frame detection method is used in the foreground image to detect the personnel and correct their direction. Finally, human posture nodes are extracted from each frame of the image sequence, which are then used to identify the abnormal behavior of the human. Simulation experiment results demonstrate that the proposed algorithm has significant advantages in terms of the accuracy of human posture node detection and risk behavior identification. 相似文献
9.
本文阐述了多轴正逆向制造发展趋势,基地建设的必要性,以五轴加工中心、五轴仿真模拟面板、三维扫描仪、3D打印机等为主的加工、逆向、快速成形先进前沿设备,形成多元化的先进制造实习链,满足、丰富实训内容,提升学生社会就业竞争力。 相似文献
10.
Chao Peng Tian Zhang Deliris N Ortiz‐Ortiz Apoorva Vishwakarma Hazel A Barton Abraham Joy 《Polymer International》2019,68(7):1255-1262
Each year, thousands of patients die from antimicrobial‐resistant bacterial infections that fail to respond to conventional antibiotic treatment. Antimicrobial polymers are a promising new method of combating antibiotic‐resistant bacterial infections. We have previously reported the synthesis of a series of narrow‐spectrum peptidomimetic antimicrobial polyurethanes that are effective against Gram‐negative bacteria, such as Escherichia coli; however, these polymers are not effective against Gram‐positive bacteria, such as Staphylococcus aureus. With the aim of understanding the correlation between chemical structure and antibacterial activity, we have subsequently developed three structural variants of these antimicrobial polyurethanes using post‐polymerization modification with decanoic acid and oleic acid. Our results show that such modifications converted the narrow‐spectrum antibacterial activity of these polymers into broad‐spectrum activity against Gram‐positive species such as S. aureus, however, also increasing their toxicity to mammalian cells. Mechanistic studies of bacterial membrane disruption illustrate the differences in antibacterial action between the various polymers. The results demonstrate the challenge of balancing antimicrobial activity and mammalian cell compatibility in the design of antimicrobial polymer compositions. © 2019 Society of Chemical Industry 相似文献