全文获取类型
收费全文 | 5078篇 |
免费 | 141篇 |
国内免费 | 86篇 |
专业分类
电工技术 | 22篇 |
综合类 | 117篇 |
化学工业 | 1792篇 |
金属工艺 | 143篇 |
机械仪表 | 180篇 |
建筑科学 | 68篇 |
矿业工程 | 24篇 |
能源动力 | 240篇 |
轻工业 | 450篇 |
水利工程 | 9篇 |
石油天然气 | 129篇 |
武器工业 | 14篇 |
无线电 | 340篇 |
一般工业技术 | 997篇 |
冶金工业 | 47篇 |
原子能技术 | 143篇 |
自动化技术 | 590篇 |
出版年
2024年 | 2篇 |
2023年 | 61篇 |
2022年 | 104篇 |
2021年 | 141篇 |
2020年 | 103篇 |
2019年 | 115篇 |
2018年 | 99篇 |
2017年 | 193篇 |
2016年 | 161篇 |
2015年 | 128篇 |
2014年 | 260篇 |
2013年 | 357篇 |
2012年 | 283篇 |
2011年 | 417篇 |
2010年 | 264篇 |
2009年 | 341篇 |
2008年 | 312篇 |
2007年 | 290篇 |
2006年 | 261篇 |
2005年 | 200篇 |
2004年 | 213篇 |
2003年 | 158篇 |
2002年 | 133篇 |
2001年 | 86篇 |
2000年 | 81篇 |
1999年 | 95篇 |
1998年 | 100篇 |
1997年 | 67篇 |
1996年 | 57篇 |
1995年 | 40篇 |
1994年 | 40篇 |
1993年 | 31篇 |
1992年 | 20篇 |
1991年 | 25篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有5305条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(12):16649-16655
Effective adhesion between AlOx and SiOx is important for protective coatings and high-k films under extreme operating conditions. Here, we study the chemo-mechanical behavior of the AlOx/SiOx interface and its delamination mechanism using all-atom reactive molecular dynamics simulations. The structure of the interface is examined by the formation of bridge oxygen and the distribution of nanopores. The cleavage of ionic bonds during delamination and the resulting adhesion strength of the system are quantified using pull-out simulations. The results reveal the dependence of the nanopores and ionic bond formation on the oxide structure. The ionic bond density at the interface increases as the oxidation of the aluminum surface proceeds, which directly increases the adhesion strength with SiOx. In particular, the global coordination distribution in the homogeneously grown oxide inhibits the formation of nanopores inside the aluminum substrate and contributes to extremely high adhesion strength. This reveals a fundamental relationship between physicochemical parameters and engineering mechanics for hetero-oxide structure design. 相似文献
2.
近年来,我国居民生活水平逐步提高,营养供给能力显著增强,高脂食物摄入量陡然增加。过量的脂肪摄入会破坏机体能量代谢和物质代谢平衡、引发系统炎症,诱导肥胖、糖尿病和非酒精性脂肪肝等慢性代谢疾病的发生。基于此,美国农业部和中国营养学会分别修订了各自的膳食指南,以期通过平衡膳食改善过量脂肪摄入诱发的系统炎症和代谢紊乱。药食同源作为平衡膳食的重要组成部分,其干预缓解肥胖发生和发展的作用效果及机制备受关注。本文从药食同源生物活性物质概念出发,聚焦其降脂减重的作用效果,从降低食欲、调节脂质吸收和代谢、干预脂肪细胞的功能、影响能量消耗和脂质储存、调节肠道屏障功能和改善肠道菌群等方面综述药食同源生物活性物质降脂减重的分子机制,并对其未来研究方向进行了展望,以期为功能性食品及药品领域的开发和综合利用提供理论依据。 相似文献
3.
The coupling of reaction and diffusion between neighboring active sites in the catalyst pore leads to the spatiotemporal fluctuation in component concentration, which is very important to catalyst performance and hence its optimal design. Molecular dynamics simulation with hard-sphere and pseudo-particle modeling has previously revealed the non-stochastic concentration fluctuation of the reactant/product near isolated active site due to such coupling, using a simple model reaction of A → B in 2D pores. The topic is further developed in this work by studying the concentration fluctuation due to such coupling between neighboring active sites in 3D pores. Two 3D pore models containing an isolated active site and two adjacent active sites were constructed, respectively. For the isolated site, the concentration fluctuation intensifies for larger pores, but the product yield decreases, and for a given pore size, the product yield reaches a peak at a certain reactant concentration. For two neighboring sites, their distance (d) is found to have little effect on the reaction, but significant to the diffusion. For the same reaction competing at both sites, larger d leads to more efficient diffusion and better overall performance. However, for sequential reactions at the two sites, higher overall performance presents at a smaller d. The results should be helpful to the catalyst design and reaction control in the relevant processes. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(6):4062-4074
In this work, coupling effects of water content, temperature, oxygen density, and polytetrafluoroethylene (PTFE) loading on oxygen transport through an ionomer thin film on a platinum surface in a catalyst layer of a proton exchange membrane (PEM) fuel cell are investigated using molecular dynamics approach. Taguchi orthogonal algorithm is employed to comprehensively analyze the coupling effects in a limited number of cases. It is found that the effect of operation temperature is the weakest among the four factors, which has the smallest effect index 14.4. Coupling effects including the PTFE loadings on the oxygen transfer through the ionomer thin film is uncovered. Less PTFE loadings should be beneficial for the oxygen transfer. The chemical potential gradient is considered as the major driven force for the oxygen transport through the ionomer thin film, and oxygen density is the dominating factor, significantly affecting the chemical potential in the thin film. 相似文献
5.
Pengcheng Li Xiuxia Xu Junjie Zhao Pragati Awasthi Xusheng Qiao Jincheng Du Xianping Fan Guodong Qian 《中国稀土学报(英文版)》2022,40(2):169-192
Significant developments have been made in the past few decades for lanthanide(Ln)ions doped fluorosilicate glass-ceramics(Flusi-GCs).As novel generation of luminescence materials with a wide range of applications,Flusi-GCs as a single host combine the advantages of glass and ceramics/crystals as well as fluorides and silicates.In this review,the chemical design principles and experimental procedures of Flusi-GCs are summarized in detail.Flusi-GCs are categorized as those containing PbxCd1-xF2,RF3(R=Y,La,Gd),MF2(M=Ca,Sr,Ba),xMF2-yRF3(R=Y,La-Lu),mAF-nRF3(A=Li,Na,K),KTF3(T=Zn,Mn)and K2 SiF6 nanocrystals(NCs).Theoretical breakthroughs mainly by molecular dynamic(MD)simulation have been recapitulated as efficient routes for composition-design,nano-crystallization-prediction,and performance-optimization of Flusi-GCs containing target fluoride NCs.Essential research progresses pertaining photonic applications have been made in random lasers,communication amplifiers,optical fibers,spectral converters,white light-emitting-diodes(WLEDs),and thermal sensors.In the end,we propose three future research directions for Flusi-GCs. 相似文献
6.
Inhibition of protein misfolding and aggregation is a great challenge in the field of biochemical and biopharmaceutical engineering. Alzheimer's disease (AD) is a protein-misfolding disease, and the interactions between 40-amino-acid-residue β-amyloid peptide (Aβ40) and its N-terminal truncated peptide Aβ11-40 demonstrate that Aβ11-40 may play an important role in the pathological process of AD. However, the effect of inhibitors on Aβ11-40 aggregation and on the cross-amyloid aggregation (co-assembly) between Aβ40 and Aβ11-40 has never been studied. Herein, coaggregation and seeding interactions between Aβ40 and Aβ11-40 as well as the effect of epigallocatechin gallate (EGCG), a small molecule inhibitor, on the cross-amyloid aggregation have been investigated by extensive analyses. It is found that Aβ11-40 participates in the aggregation of Aβ40 and leads to the formation of coaggregates that contain less β-sheet structures than pure Aβ40 aggregates. The aggregation kinetics along with morphologies and secondary structures of the coaggregates are also significantly affected by the Aβ40/Aβ11-40 ratio. EGCG accelerates the nucleation of Aβ40 but retards that of Aβ11-40 by affecting their elongation and secondary nucleation processes in solution and on solid surfaces. Meanwhile, EGCG makes the conformations of the seeding-induced Aβ aggregates more compact, especially for the homologous seedings. Isothermal titration calorimetry measurement indicates that hydrophobic interactions mainly contribute to the inhibition of the two Aβ isoforms by EGCG. The findings of this research have provided new insights into Aβ aggregation and the effect of an important inhibitor and the results would benefit in the development of potent inhibitors against co-assembly of different amyloid proteins. 相似文献
7.
Delf-Magnus Kummerfeld Carsten A. Raabe Juergen Brosius Dingding Mo Boris V. Skryabin Timofey S. Rozhdestvensky 《International journal of molecular sciences》2021,22(7)
Prader-Willi syndrome (PWS) is a neurogenetic multifactorial disorder caused by the deletion or inactivation of paternally imprinted genes on human chromosome 15q11-q13. The affected homologous locus is on mouse chromosome 7C. The positional conservation and organization of genes including the imprinting pattern between mice and men implies similar physiological functions of this locus. Therefore, considerable efforts to recreate the pathogenesis of PWS have been accomplished in mouse models. We provide a summary of different mouse models that were generated for the analysis of PWS and discuss their impact on our current understanding of corresponding genes, their putative functions and the pathogenesis of PWS. Murine models of PWS unveiled the contribution of each affected gene to this multi-facetted disease, and also enabled the establishment of the minimal critical genomic region (PWScr) responsible for core symptoms, highlighting the importance of non-protein coding genes in the PWS locus. Although the underlying disease-causing mechanisms of PWS remain widely unresolved and existing mouse models do not fully capture the entire spectrum of the human PWS disorder, continuous improvements of genetically engineered mouse models have proven to be very powerful and valuable tools in PWS research. 相似文献
8.
In this work,a molecular-level kinetic model was built to simulate the vacuum residue (VR) coking pro-cess in a semi-batch laboratory-scale reaction kettle.A series of reaction rules for heavy oil coking were summarized and formulated based on the free radical reaction mechanism.Then,a large-scale molecular-level reaction network was automatically generated by applying the reaction rules on the vacuum residue molecules.In order to accurately describe the physical change of each molecule in the reactor,we cou-pled the molecular-level kinetic model with a vapor-liquid phase separation model.The vapor-liquid phase separation model adopted the Peng-Robinson equation of state to calculate vapor-liquid equilib-rium.A separation efficiency coefficient was introduced to represent the mass transfer during the phase separation.We used six sets of experimental data under various reaction conditions to regress the model parameters.The tuned model showed that there was an excellent agreement between the calculated val-ues and experimental data.Moreover,we investigated the effect of reaction temperature and reaction time on the product yields.After a comprehensive evaluation of the reaction temperature and reaction time,the optimal reaction condition for the vacuum residue coking was also obtained. 相似文献
9.
目的制备分子印迹聚合物,为敌百虫的分离富集提供参考。方法以敌百虫为模板,3-氨基三丙基乙氧基硅烷(3-aminotripropylethoxysilane,APTES)为功能单体,正硅酸乙酯(ethyl orthosilicate,TEOS)为交联剂,采用溶胶-凝胶法制备分子印迹聚合物。将制备的印迹聚合物作为固相萃取填料应用于实际样品中敌百虫的分离富集,结合高效液相色谱法(high performance liquid chromatography,HPLC)对白菜、甘蓝、西红柿中的敌百虫含量进行测定。结果该方法可有效去除基质干扰,检出限为0.92μg/kg,回收率在87.66%~100.0%之间,RSD≤4.5%。结论本实验为实际样品的前处理提供了新思路,为敌百虫的检测发展了新方法,有望广泛应用于实际样品中敌百虫的分离检测中。 相似文献
10.
《工程(英文)》2020,6(1):10-19
Neospora caninum (N. caninum), a cyst-forming protozoan parasite, is a major cause of bovine abortions and neonatal mortality worldwide. N. caninum has a broad intermediate host range, and its sexual cycle occurs exclusively in canids. Another species of Neospora, Neospora hughesi (N. hughesi), has been identified and causes myeloencephalitis in horses. Although molecular epidemiology studies are in their infancy, the 18S ribosomal RNA (rRNA) and ITS1 regions within the small subunit ribosomal RNA (ssuRNA) and an N. caninum species-specific DNA probe (pNc5) have been used extensively to differentiate Neospora from other closely related apicomplexan parasites. While these repetitive regions have higher sensitivity and specificity than housekeeping or antigen genes, they suffer from low discriminatory power and fail to capture intra-species diversity. Similarly, although multiple minisatellite or microsatellite marker studies have shown clear geographic substructures within Neospora, strains are often misclassified due to a convergence in the size of different alleles at microsatellite loci, known as homoplasy. Only one strain, N. caninum Liverpool (Nc-Liv), has been genome sequenced and compared with its closest relative, Toxoplasma gondii (T. gondii). Hence, detailed population genomics studies based on whole-genome sequences from multiple strains worldwide are needed in order to better understand the current population genetic structure of Neospora, and ultimately to determine more effective vaccine candidates against bovine neosporosis. The aim of this review is to outline our current understanding of the molecular epidemiology and genomics of Neospora in juxtaposition with the closely related apicomplexan parasites Hammondia hammondi and T. gondii. 相似文献