全文获取类型
收费全文 | 6888篇 |
免费 | 663篇 |
国内免费 | 254篇 |
专业分类
电工技术 | 47篇 |
综合类 | 474篇 |
化学工业 | 2283篇 |
金属工艺 | 386篇 |
机械仪表 | 285篇 |
建筑科学 | 687篇 |
矿业工程 | 65篇 |
能源动力 | 67篇 |
轻工业 | 1947篇 |
水利工程 | 53篇 |
石油天然气 | 166篇 |
武器工业 | 43篇 |
无线电 | 233篇 |
一般工业技术 | 788篇 |
冶金工业 | 96篇 |
原子能技术 | 38篇 |
自动化技术 | 147篇 |
出版年
2024年 | 61篇 |
2023年 | 174篇 |
2022年 | 363篇 |
2021年 | 432篇 |
2020年 | 296篇 |
2019年 | 276篇 |
2018年 | 249篇 |
2017年 | 275篇 |
2016年 | 319篇 |
2015年 | 323篇 |
2014年 | 301篇 |
2013年 | 563篇 |
2012年 | 463篇 |
2011年 | 451篇 |
2010年 | 300篇 |
2009年 | 313篇 |
2008年 | 271篇 |
2007年 | 362篇 |
2006年 | 347篇 |
2005年 | 276篇 |
2004年 | 221篇 |
2003年 | 189篇 |
2002年 | 145篇 |
2001年 | 128篇 |
2000年 | 102篇 |
1999年 | 101篇 |
1998年 | 98篇 |
1997年 | 56篇 |
1996年 | 46篇 |
1995年 | 50篇 |
1994年 | 39篇 |
1993年 | 42篇 |
1992年 | 27篇 |
1991年 | 34篇 |
1990年 | 22篇 |
1989年 | 32篇 |
1988年 | 15篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1980年 | 8篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7805条查询结果,搜索用时 0 毫秒
941.
Samuel J. Bunce Yiming Wang Sheena E. Radford Andrew J. Wilson Carol K. Hall 《American Institute of Chemical Engineers》2021,67(3):e17101
Determining the structure of the (oligomeric) intermediates that form during the self-assembly of amyloidogenic peptides is challenging because of their heterogeneous and dynamic nature. Thus, there is need for methodology to analyze the underlying molecular structure of these transient species. In this work, a combination of fluorescence quenching, photo-induced crosslinking (PIC) and molecular dynamics simulation was used to study the assembly of a synthetic amyloid-forming peptide, Aβ16-22. A PIC amino acid containing a trifluormethyldiazirine (TFMD) group—Fmoc(TFMD)Phe—was incorporated into the sequence (Aβ*16–22). Electrospray ionization ion-mobility spectrometry mass-spectrometry (ESI-IMS-MS) analysis of the PIC products confirmed that Aβ*16–22 forms assemblies with the monomers arranged as anti-parallel, in-register β-strands at all time points during the aggregation assay. The assembly process was also monitored separately using fluorescence quenching to profile the fibril assembly reaction. The molecular picture resulting from discontinuous molecule dynamics simulations showed that Aβ16-22 assembles through a single-step nucleation into a β-sheet fibril in agreement with these experimental observations. This study provides detailed structural insights into the Aβ16-22 self-assembly processes, paving the way to explore the self-assembly mechanism of larger, more complex peptides, including those whose aggregation is responsible for human disease. 相似文献
942.
943.
Marijana Đaković 《Crystallography Reviews》2020,26(2):69-100
Designing crystalline solids with improved properties or performances remains a challenging task, despite great strides that have been made within the field of crystal engineering since its birth several decades ago. Herein, we are bringing examples that illustrate recent successes in taking supramolecular synthetic guidelines from the organic crystal engineering and adjusting those to metal-containing systems, particularly to the lower-dimensional ones. The versatility of calculated molecular electrostatic potential (MEP) as a new crystal engineering tool is demonstrated. 相似文献
944.
Seok Su Sohn Alisson Kwiatkowski da Silva Yuji Ikeda Fritz Krmann Wenjun Lu Won Seok Choi Baptiste Gault Dirk Ponge Jrg Neugebauer Dierk Raabe 《Advanced materials (Deerfield Beach, Fla.)》2019,31(8)
Severe lattice distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium‐ and high‐entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of lattice distortion. Here it is shown that a simple VCoNi equiatomic medium‐entropy alloy exhibits a near 1 GPa yield strength and good ductility, outperforming conventional solid‐solution alloys. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe lattice distortion, improves both yield stress and its sensitivity to grain size. In addition, the dislocation‐mediated plasticity effectively enhances the strength–ductility relationship by generating nanosized dislocation substructures due to massive pinning. The results demonstrate that severe lattice distortion is a key property for identifying extra‐strong materials for structural engineering applications. 相似文献
945.
《Journal of dairy science》2022,105(1):140-153
A multiparameter study was performed to evaluate the effect of fondaco, a traditional ripening cellar without any artificial temperature and relative humidity control, on the chemical, microbiological, and sensory characteristics of Protected Geographical Indication Canestrato di Moliterno cheese. Ripening in such a nonconventional environment was associated with lower counts of lactococci, lactobacilli, and total viable bacteria, and higher presence of enterococci, in comparison with ripening in a controlled maturation room. Moreover, fondaco cheese underwent accelerated maturation, as demonstrated by faster casein degradation, greater accumulation of free AA, and higher formation of volatile organic compounds. Secondary proteolysis, as assessed by liquid chromatography-mass spectrometry of free AA and low molecular weight peptides, did not show any qualitative difference among cheeses, but fondaco samples evidenced an advanced level of peptidolysis. On the other hand, significant qualitative differences were observed in the free fatty acid profiles and in the sensory characteristics. Principal component analysis showed a clear separation of the fondaco and control cheeses, indicating that ripening in the natural room conferred unique sensory features to the product. 相似文献
946.
Yao Qin Yajing You Guangzheng Jin Wei Zhu Yudan Zhu Qiutian Wang Xiaohua Lu Yijun Shi 《American Institute of Chemical Engineers》2022,68(4):e17581
Molecular dynamics simulations are performed to investigate the solid surface-induced microstructure and friction coefficient of glycerol aqueous solutions with different water contents confined in graphene and FeO nanoslits. Results show that the friction coefficient of glycerol aqueous solutions confined in both nanoslits presents similar nonlinear variation tendencies with increasing water content, but their lowest value and the corresponding water contents differ. Distinctive microstructures of the near-surface liquid layer induced by surfaces with different hydrophilicity are responsible for their difference in lubrication. The sliding primarily occurs at the solid–liquid interface for the hydrophobic graphene nanoslit owing to almost the same velocity difference in fluid molecules. By contrast, the sliding mainly occurs at the liquid–liquid interface for the hydrophilic FeO nanoslit because of the large velocity difference in fluid molecules. The weaker the interaction force at the sliding position, the lower the friction coefficient. 相似文献
947.
Leucokinins (LKs) constitute a family of neuropeptides identified in numerous insects and many other invertebrates. LKs act on G-protein-coupled receptors that display only distant relations to other known receptors. In adult Drosophila, 26 neurons/neurosecretory cells of three main types express LK. The four brain interneurons are of two types, and these are implicated in several important functions in the fly’s behavior and physiology, including feeding, sleep–metabolism interactions, state-dependent memory formation, as well as modulation of gustatory sensitivity and nociception. The 22 neurosecretory cells (abdominal LK neurons, ABLKs) of the abdominal neuromeres co-express LK and a diuretic hormone (DH44), and together, these regulate water and ion homeostasis and associated stress as well as food intake. In Drosophila larvae, LK neurons modulate locomotion, escape responses and aspects of ecdysis behavior. A set of lateral neurosecretory cells, ALKs (anterior LK neurons), in the brain express LK in larvae, but inconsistently so in adults. These ALKs co-express three other neuropeptides and regulate water and ion homeostasis, feeding, and drinking, but the specific role of LK is not yet known. This review summarizes Drosophila data on embryonic lineages of LK neurons, functional roles of individual LK neuron types, interactions with other peptidergic systems, and orchestrating functions of LK. 相似文献
948.
Multi-drug-resistant bacteria are becoming more prevalent, and treating these bacteria is becoming a global concern. One alternative approach to combat bacterial resistance is to use antimicrobial (AMPs) or host-defense peptides (HDPs) because they possess broad-spectrum activity, function in a variety of ways, and lead to minimal resistance. However, the therapeutic efficacy of HDPs is limited by a number of factors, including systemic toxicity, rapid degradation, and low bioavailability. One approach to circumvent these issues is to use lipidation, i.e., the attachment of one or more fatty acid chains to the amine groups of the N-terminus or a lysine residue of an HDP. In this review, we examined lipidated analogs of 66 different HDPs reported in the literature to determine: (i) whether there is a link between acyl chain length and antibacterial activity; (ii) whether the charge and (iii) the hydrophobicity of the HDP play a role; and (iv) whether acyl chain length and toxicity are related. Overall, the analysis suggests that lipidated HDPs with improved activity over the nonlipidated counterpart had acyl chain lengths of 8–12 carbons. Moreover, active lipidated peptides attached to short HDPs tended to have longer acyl chain lengths. Neither the charge of the parent HDP nor the percent hydrophobicity of the peptide had an apparent significant impact on the antibacterial activity. Finally, the relationship between acyl chain length and toxicity was difficult to determine due to the fact that toxicity is quantified in different ways. The impact of these trends, as well as combined strategies such as the incorporation of d- and non-natural amino acids or alternative approaches, will be discussed in light of how lipidation may play a role in the future development of antimicrobial peptide-based alternatives to current therapeutics. 相似文献
949.
《Ceramics International》2022,48(14):20096-20101
A series of Mn2+-doped Mg1-xMnxTa2O6 (x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) ceramics were synthesized by solid-state reaction method. The influence of introducing Mn–O bonds as a partial replacement for Mg–O bonds on the lattice and microwave dielectric properties was systematically investigated. XRD and Rietveld refinement confirm that Mn2+ occupies the 2a Wyckoff position and forms a pure trirutile phase. Moreover, based on the chemical bond theory, the dielectric constant is mainly affected by the ionicity of the Ta–O bond. The lattice and dielectric properties remain relatively stable with Mn2+ doping below 0.1, but excessive Mn2+ doping leads to pronounced distortion of the lattice, which is not beneficial for lattice stability and microwave dielectric properties. Introducing an appropriate amount of Mn–O bonds with high bond dissociation energy facilitates MgO6 octahedron stability, which improves the thermal stability of the lattice. Accordingly, the microwave dielectric properties for 0.06 Mn2+-doped MgTa2O6 ceramics were determined: εr = 28, Q × f = 105,000 GHz (at 7.5 GHz), τf = 19.5 ppm/°C. 相似文献
950.