全文获取类型
收费全文 | 37661篇 |
免费 | 3785篇 |
国内免费 | 2186篇 |
专业分类
电工技术 | 3184篇 |
技术理论 | 3篇 |
综合类 | 3706篇 |
化学工业 | 3476篇 |
金属工艺 | 768篇 |
机械仪表 | 2405篇 |
建筑科学 | 2761篇 |
矿业工程 | 749篇 |
能源动力 | 708篇 |
轻工业 | 4476篇 |
水利工程 | 563篇 |
石油天然气 | 1462篇 |
武器工业 | 327篇 |
无线电 | 2902篇 |
一般工业技术 | 4392篇 |
冶金工业 | 1311篇 |
原子能技术 | 279篇 |
自动化技术 | 10160篇 |
出版年
2024年 | 181篇 |
2023年 | 586篇 |
2022年 | 1009篇 |
2021年 | 1227篇 |
2020年 | 1285篇 |
2019年 | 1172篇 |
2018年 | 1063篇 |
2017年 | 1331篇 |
2016年 | 1396篇 |
2015年 | 1491篇 |
2014年 | 2333篇 |
2013年 | 2351篇 |
2012年 | 2801篇 |
2011年 | 3145篇 |
2010年 | 2329篇 |
2009年 | 2328篇 |
2008年 | 2018篇 |
2007年 | 2446篇 |
2006年 | 2060篇 |
2005年 | 1678篇 |
2004年 | 1428篇 |
2003年 | 1244篇 |
2002年 | 1074篇 |
2001年 | 797篇 |
2000年 | 687篇 |
1999年 | 583篇 |
1998年 | 532篇 |
1997年 | 447篇 |
1996年 | 327篇 |
1995年 | 331篇 |
1994年 | 238篇 |
1993年 | 207篇 |
1992年 | 171篇 |
1991年 | 139篇 |
1990年 | 125篇 |
1989年 | 129篇 |
1988年 | 110篇 |
1987年 | 73篇 |
1986年 | 71篇 |
1985年 | 73篇 |
1984年 | 101篇 |
1983年 | 102篇 |
1982年 | 111篇 |
1981年 | 52篇 |
1980年 | 49篇 |
1979年 | 33篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1959年 | 13篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Muhammad Yazid Samatra Nor Qhairul Izzreen Mohd Noor Umi Hartina Mohamad Razali Jamilah Bakar Sharifudin Md. Shaarani 《Comprehensive Reviews in Food Science and Food Safety》2022,21(4):3153-3176
Gelatin is one of the most important multifunctional biopolymers and is widely used as an essential ingredient in food, pharmaceutical, and cosmetics. Porcine gelatin is regarded as the leading source of gelatin globally then followed by bovine gelatin. Porcine sources are favored over other sources since they are less expensive. However, porcine gelatin is religiously prohibited to be consumed by Muslims and the Jewish community. It is predicted that the global demand for gelatin will increase significantly in the future. Therefore, a sustainable source of gelatin with efficient production and free of disease transmission must be developed. The highest quality of Bovidae-based gelatin (BG) was acquired through alkaline pretreatment, which displayed excellent physicochemical and rheological properties. The utilization of mammalian- and plant-based enzyme significantly increased the gelatin yield. The emulsifying and foaming properties of BG also showed good stability when incorporated into food and pharmaceutical products. Manipulation of extraction conditions has enabled the development of custom-made gelatin with desired properties. This review highlighted the various modifications of extraction and processing methods to improve the physicochemical and functional properties of Bovidae-based gelatin. An in-depth analysis of the crucial stage of collagen breakdown is also discussed, which involved acid, alkaline, and enzyme pretreatment, respectively. In addition, the unique characteristics and primary qualities of BG including protein content, amphoteric property, gel strength, emulsifying and viscosity properties, and foaming ability were presented. Finally, the applications and prospects of BG as the preferred gelatin source globally were outlined. 相似文献
2.
Ya Gu Quanmin Zhu Hassan Nouri 《International Journal of Adaptive Control and Signal Processing》2022,36(1):138-154
This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(2):1306-1318
The effective and efficient utilization of low-calorific value (LCV) gases has gained increasing attention in scientific research and industrial fields. In this study, the combustion characteristics of three LCV gases in practical devices are analyzed by using a nonadiabatic perfectly stirred reactor model. The complete steady-state solution in the temperature-residence time parameter space is obtained with arc-length continuation. The stable operation region is quantified by the eigenvalue analysis. The transition of solution curves is quantified with heat loss coefficient. Five key system parameters are systematically investigated on their effects on stability limits. With the combustion performance being quantified by a combustion state index, a combustion state regulation method is proposed to find the optimal regulation path of system parameters. Active subspace method is further applied to shorten the regulation step by identifying the active direction. The proposed method and findings are useful for optimal regulation of burning LCV gases in industrial burners. 相似文献
4.
《Ceramics International》2022,48(15):21483-21491
To battle the high open-circuit voltage deficit (VOC,def) in kesterite (Cu2ZnSnS4 or CZTS) solar cells, a current field of research relates to point defect engineering by cation substitution. For example, by partly replacing Cu with an element of a larger ionic radius, such as Ag, the degree of Cu/Zn disorder decreases, and likewise does the associated band tailing. In this paper, solution-processed (Ag1-xCux)2ZnSnS4 (ACZTS) samples are prepared through the aprotic molecular ink approach using DMSO as the solvent. The successful incorporation of silver into the CZTS lattice is demonstrated with relatively high silver concentrations, namely Ag/(Ag+Cu) ratios of 13% and 26%. The best device was made with 13% Ag/(Ag+Cu) and had an efficiency of 4.9%. The samples are compared to the pure CZTS sample in terms of microstructure, phase distribution, photoluminescence, and device performance. In the XRD patterns, a decrease in the lattice parameter c/a ratio is observed for ACZTS, as well as significant peak splitting with Ag addition for several of the characteristic kesterite XRD reflections. In addition to the improvement in efficiency, other advantageous effects of Ag-incorporation include enhanced grain growth and an increased band gap. A too high concentration of Ag leads to the formation of secondary phases such as SnS and Ag2S as detected by XRD. 相似文献
5.
6.
Currently, the efficient detection of fingerprints is essential for the crime investigations. Revealing fingerprints is commonly achieved with fluorescent organic compounds but they are not efficient for fingerprint detection on porous or reflective surfaces. In order to solve the problem of collecting fingerprints on porous/reflective surfaces, inorganic phosphors have been employed, since they have characteristics of variable color emission, afterglow, high chemical stability and nano-size, which allow the fingerprint detection on any porous or non-porous surfaces. Due to these last properties, this review presents a summary about the use of phosphorescent and fluorescent phosphors for the detection of latent fingerprints. First, we discussed the main physical and chemical characteristics of the fingerprints which permit their detection and collection from any surface. After this, we presented the main morphological, structural and luminescent properties of the phosphorescent and fluorescent phosphors that allow their use for fingerprint detection. Later, we demonstrated with pictures of fingerprints (with and without light emission from the phosphors deposited on them) that both, phosphorescent and fluorescent phosphors can be used to visualize fingerprints with high resolution and high contrast without interference of the background surface, which is ideal for its collection and registration in the Automated Fingerprint Identification System (AFIS). We believe that this review could be useful to understand how to select an appropriate phosphorescent or fluorescent material for fingerprint detection depending on the type of surface (porous or non-porous, reflective or not reflective) where the fingerprint is deposited. 相似文献
7.
During the service life of structural sealant glazing (SSG) facades, the load-bearing capacity of the silicone bonds needs to be guaranteed. Laboratory tests can assess the durability of SSG-systems based on mechanical characteristics of the bond after simultaneous exposure to both climatic and mechanical loads. This article studies how the material characteristics of two common structural sealants are affected by laboratory and field exposure. Dynamic mechanical analysis (DMA) confirms a reduction in the dynamic modulus of exposed silicone samples. Results from thermogravimetric analysis, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and small-angle X-ray scattering/wide-angle X-ray scattering show differences between the two sealants and indicate no/minor changes in the composition and morphology of the laboratory and field exposed sealants. Mechanical characterization methods, such as DMA, and tensile and shear testing of the structural bond, are shown to be sensitive toward the combined climatic and mechanical loadings, and are hence suitable for studying degradation mechanisms of structural sealants. 相似文献
8.
9.
10.
Structural health monitoring system based on multi-agent coordination and fusion for large structure
In practical applications of structural health monitoring technology, a large number of distributed sensors are usually adopted to monitor the big dimension structures and different kinds of damage. The monitored structures are usually divided into different sub-structures and monitored by different sensor sets. Under this situation, how to manage the distributed sensor set and fuse different methods to obtain a fast and accurate evaluation result is an important problem to be addressed deeply. In the paper, a multi-agent fusion and coordination system is presented to deal with the damage identification for the strain distribution and joint failure in the large structure. Firstly, the monitoring system is adopted to distributedly monitor two kinds of damages, and it self-judges whether the static load happens in the monitored sub-region, and focuses on the static load on the sub-region boundary to obtain the sensor network information with blackboard model. Then, the improved contract net protocol is used to dynamically distribute the damage evaluation module for monitoring two kinds of damage uninterruptedly. Lastly, a reliable assessment for the whole structure is given by combing various heterogeneous classifiers strengths with voting-based fusion. The proposed multi-agent system is illustrated through a large aerospace aluminum plate structure experiment. The result shows that the method can significantly improve the monitoring performance for the large-scale structure. 相似文献