全文获取类型
收费全文 | 551篇 |
免费 | 33篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 20篇 |
综合类 | 2篇 |
化学工业 | 168篇 |
金属工艺 | 16篇 |
机械仪表 | 3篇 |
建筑科学 | 9篇 |
能源动力 | 10篇 |
轻工业 | 19篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 88篇 |
一般工业技术 | 156篇 |
冶金工业 | 23篇 |
自动化技术 | 69篇 |
出版年
2024年 | 2篇 |
2023年 | 26篇 |
2022年 | 40篇 |
2021年 | 40篇 |
2020年 | 34篇 |
2019年 | 17篇 |
2018年 | 29篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 21篇 |
2014年 | 19篇 |
2013年 | 22篇 |
2012年 | 40篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 25篇 |
2008年 | 21篇 |
2007年 | 32篇 |
2006年 | 27篇 |
2005年 | 17篇 |
2004年 | 18篇 |
2003年 | 9篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有586条查询结果,搜索用时 0 毫秒
51.
52.
Ilham Zainal Abidin Catalin Mandache Gui Yun Tian Maxim Morozov 《NDT & E International》2009,42(7):599-605
In pulsed eddy current testing, repetitive excitation signals with different duty cycles have different spectral representations. This work studies the influence of duty cycle on the ability to detect holes and EDM notches beneath rivet heads in subsurface layers of stratified samples. Feature patterns for the integrity of rivet joints are proposed and verified. The proposed method has the added advantage in that no reference sample is needed while employing multiple pulse measurements, with different pulse widths. Experimental testing and modelling approaches are discussed in connection with defect depth quantification, which can be extended to the quantification of complex defects. 相似文献
53.
A detailed investigation into the isolation by extraction and the purification by crystallization of the enzyme urease from jack bean meal is presented with a view to developing a large-scale process. The effect of different extraction solvents and additives upon the resulting crystals is characterised in terms of crystal size, protein yield and protein purity. The enzymatic activity of urease is exploited in order to quantify the amount and purity of the protein obtained. The extraction procedure was optimised and all stages of the process were monitored in order to provide as detailed a picture as possible of the impact of different process stages upon the intermediate products. Almost all protein is extracted in a single extraction step. Further extraction steps using the same meal but fresh solvent yield only small additional protein yields. Less than 10% of total protein is extracted in a second step, less than 3% in a third extraction. Different solvents lead to clear differences in product quality, with no single solvent optimising all quality criteria. In addition, the point at which the acetone precipitant is introduced into the process has a clear influence on the product. Judicious choice of extraction conditions can significantly increase the size of the urease crystals at the cost of product purity, quantified by specific activity. High product purity (a maximum 138-fold increase in purity was observed with a maximum yield of 8.4%), in contrast, leads to smaller crystals. Comparison to the purest commercially available urease revealed a similar urease content. 相似文献
54.
55.
Muammer Y. Yaman Sergei V. Kalinin Kathryn N. Guye David S. Ginger Maxim Ziatdinov 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(25):2205893
The application of machine learning is demonstrated for rapid and accurate extraction of plasmonic particles cluster geometries from hyperspectral image data via a dual variational autoencoder (dual-VAE). In this approach, the information is shared between the latent spaces of two VAEs acting on the particle shape data and spectral data, respectively, but enforcing a common encoding on the shape-spectra pairs. It is shown that this approach can establish the relationship between the geometric characteristics of nanoparticles and their far-field photonic responses, demonstrating that hyperspectral darkfield microscopy can be used to accurately predict the geometry (number of particles, arrangement) of a multiparticle assemblies below the diffraction limit in an automated fashion with high fidelity (for monomers (0.96), dimers (0.86), and trimers (0.58). This approach of building structure-property relationships via shared encoding is universal and should have applications to a broader range of materials science and physics problems in imaging of both molecular and nanomaterial systems. 相似文献
56.
Reza Mirzaeitalarposhti Michael Scott Demyan Frank Rasche Maxim Poltoradnev Georg Cadisch Torsten Müller 《Nutrient Cycling in Agroecosystems》2015,102(2):265-283
Development of spectroscopic prediction models via partial least squares regression (PLSR) suggests that model performance is highly affected by means of calibration and nature of the dataset. This study compares the predictive performance of PLSR models obtained by cross-validation and independent validation to quantify physico-chemical soil properties from their mid-infrared diffuse reflectance Fourier transform spectra (midDRIFTS) across two contrasting regions, Kraichgau (K) and Swabian Alb (SA), in Southwest Germany. We evaluated the capability of midDRIFTS-PLSR models for predicting total carbon (TC), organic carbon (TOC), inorganic carbon (TIC), nitrogen (TN), mineral N (Nmin), C:N ratio, hot water extractable C and N (CHWE, NHWE), microbial biomass C and N (Cmic, Nmic), pH, bulk density, and clay, silt and sand contents of 126 soil samples. Based on calibrated models, most soil properties were predicted successfully using either calibration approach with residual prediction deviations ≥3 and R2 > 0.9, except for Nmin, C/N ratio, pH, bulk density and sand. However, predictive performance of generic independent validation derived models (GIC) of test set was considerably higher than generic cross-validation models. Validation using GIC models gave relatively the same predictive performance with those obtained in calibration except for Nmin. Validation of region specific cross-validated models, however, resulted in successful predictions only for TC, TIC, TOC and TN in SA and TC and TIC and TOC in K. Our results show the superiority of independent validation over both generic and region specific cross-validation as a robust tool for predicting soil properties without further laboratory measurements. 相似文献
57.
Pu Hu Zheyi Zou Xingwei Sun Da Wang Jun Ma Qingyu Kong Dongdong Xiao Lin Gu Xinhong Zhou Jingwen Zhao Shanmu Dong Bing He Maxim Avdeev Siqi Shi Guanglei Cui Liquan Chen 《Advanced materials (Deerfield Beach, Fla.)》2020,32(14):1907526
There is a long-standing consciousness that the rhombohedral NASICON-type compounds as promising cathodes for Li+/Na+ batteries should have inactive M1(6b) sites with ion (de)intercalation occurring only in the M2 (18e) sites. Of particular significance is that M1 sites active for charge/discharge are commonly considered undesirable because the ion diffusion tends to be disrupted by the irregular occupation of channels, which accelerates the deterioration of battery. However, it is found that the structural stability can be substantially improved by the mixed occupation of Na+/Zn2+ at both M1 and M2 when using NaV2(PO4)3 (NVP) as a cathode for Zn-ion batteries. The results of atomic-scale scanning transmission electron microscopy, analysis of ab initio molecular dynamics simulations, and an accurate bond-valence-based structural model reveal that the improvement is due to the facile migration of Zn2+ in NVP, which is enabled by a concerted Na+/Zn2+ transfer mechanism. In addition, significant improvement of the electronic conductivity and mechanical properties is achieved in Zn2+-intercalated ZnNaV2(PO4)3 in comparison with those of Na3V2(PO4)3. This work not only provides in-depth insight into Zn2+ intercalation and dynamics in NVP unlocked by activating the M1 sites, but also opens a new route toward design of improved NASICON cathodes. 相似文献
58.
Bazhenov M Lonjers P Skorheim S Bedard C Dstexhe A 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1952):3802-3819
Rhythmic local field potential (LFP) oscillations observed during deep sleep are the result of synchronized electrical activities of large neuronal ensembles, which consist of alternating periods of activity and silence, termed 'up' and 'down' states, respectively. Current-source density (CSD) analysis indicates that the up states of these slow oscillations are associated with current sources in superficial cortical layers and sinks in deep layers, while the down states display the opposite pattern of source-sink distribution. We show here that a network model of up and down states displays this CSD profile only if a frequency-filtering extracellular medium is assumed. When frequency filtering was modelled as inhomogeneous conductivity, this simple model had considerably more power in slow frequencies, resulting in significant differences in LFP and CSD profiles compared with the constant-resistivity model. These results suggest that the frequency-filtering properties of extracellular media may have important consequences for the interpretation of the results of CSD analysis. 相似文献
59.
Martensitic Phase Transformation and Deformation Behavior of Fe–Mn–C–Al Twinning‐Induced Plasticity Steel during High‐Pressure Torsion 下载免费PDF全文
60.
We have successfully prepared mono- and bi-functionalized multiwall carbon nanotubes (MWCNT) with thiophene, amine and thiophene-amine groups. The dispersion of nanotubes has been enhanced and stable optimized dispersions in organic solvents were obtained. These functionalized nanotubes have been successfully incorporated into bulk heterojunction (BHJ) organic photovoltaic (OPV) cells with a poly (3-hexyl thiophene) (P3HT) and [6, 6]-phenyl-C(61)-butyric acid methyl ester (PCBM) photoactive blended layer. The incorporation of MWCNT with different functional groups, in the active layer, results in different cell performance with respect to a reference cell. A maximum power conversion efficiency of 2.5% is achieved with the inclusion of thiophene functionalized nanotubes. This improvement in the device performance is attributed to an extension of the exciton dissociation volume and charge transport properties through the nanotube percolation network in P3HT/CNT, PCBM/CNT or both phases. This is believed to be due to more efficient dispersion of the functionalized nanotubes within the photoactive composite layer. 相似文献