全文获取类型
收费全文 | 459614篇 |
免费 | 4468篇 |
国内免费 | 882篇 |
专业分类
电工技术 | 7798篇 |
综合类 | 310篇 |
化学工业 | 69203篇 |
金属工艺 | 25880篇 |
机械仪表 | 17285篇 |
建筑科学 | 9445篇 |
矿业工程 | 4965篇 |
能源动力 | 8984篇 |
轻工业 | 26416篇 |
水利工程 | 6518篇 |
石油天然气 | 15544篇 |
武器工业 | 33篇 |
无线电 | 44537篇 |
一般工业技术 | 105729篇 |
冶金工业 | 68461篇 |
原子能技术 | 14497篇 |
自动化技术 | 39359篇 |
出版年
2021年 | 3989篇 |
2019年 | 3936篇 |
2018年 | 12408篇 |
2017年 | 12824篇 |
2016年 | 11232篇 |
2015年 | 4801篇 |
2014年 | 7800篇 |
2013年 | 17824篇 |
2012年 | 13003篇 |
2011年 | 19730篇 |
2010年 | 16760篇 |
2009年 | 17208篇 |
2008年 | 17635篇 |
2007年 | 18670篇 |
2006年 | 11105篇 |
2005年 | 11932篇 |
2004年 | 10981篇 |
2003年 | 10709篇 |
2002年 | 9508篇 |
2001年 | 8983篇 |
2000年 | 8957篇 |
1999年 | 8468篇 |
1998年 | 17680篇 |
1997年 | 13233篇 |
1996年 | 10266篇 |
1995年 | 7887篇 |
1994年 | 7292篇 |
1993年 | 7266篇 |
1992年 | 5972篇 |
1991年 | 5971篇 |
1990年 | 5844篇 |
1989年 | 5802篇 |
1988年 | 5593篇 |
1987年 | 5228篇 |
1986年 | 4976篇 |
1985年 | 5534篇 |
1984年 | 5285篇 |
1983年 | 5014篇 |
1982年 | 4632篇 |
1981年 | 4796篇 |
1980年 | 4669篇 |
1979年 | 4895篇 |
1978年 | 5075篇 |
1977年 | 5343篇 |
1976年 | 6559篇 |
1975年 | 4578篇 |
1974年 | 4558篇 |
1973年 | 4641篇 |
1972年 | 4015篇 |
1971年 | 3718篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Machine Learning - We propose a data-driven approach to quantify the uncertainty of models constructed by kernel methods. Our approach minimizes the needed distributional assumptions, hence,... 相似文献
152.
Sleptsov V. V. Kukushkin D. Yu. Kulikov S. N. Diteleva A. O. 《Russian Engineering Research》2021,41(5):416-418
Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor... 相似文献
153.
Refractories and Industrial Ceramics - The effect of the addition of 2 and 5 mol.% Dy2O3 during spark-plasma sintering at a compaction loading of 60 MPa in the range of 1200 – 1600°C on... 相似文献
154.
Gavshina O. V. Doroganov V. A. Doroganov E. A. Onishchuk V. I. Trepalina Yu. N. 《Refractories and Industrial Ceramics》2019,60(4):350-354
Refractories and Industrial Ceramics - Results of studying the rheotechnological properties of moldable refractory mixes based on bauxite suspensions plasticized with refractory clay are presented.... 相似文献
155.
V.A. Dekhtyarenko T.V. Pryadko D.G. Savvakin V.I. Bondarchuk G.S. Mogylnyy 《International Journal of Hydrogen Energy》2021,46(11):8040-8047
The influence of phase composition and microstructure of Ti42.75Zr27Mn20.25V10 alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature. 相似文献
156.
Manjin Kim Qinfen Gu Tanveer Hussain Yahia Ali Trevor B. Abbott Kazuhiro Nogita 《International Journal of Hydrogen Energy》2021,46(53):27096-27106
With superior properties of Mg such as high hydrogen storage capacity (7.6 wt% H/MgH2), low price, and low density, Mg has been widely studied as a promising candidate for solid-state hydrogen storage systems. However, a harsh activation procedure, slow hydrogenation/dehydrogenation process, and a high temperature for dehydrogenation prevent the use of Mg-based metal hydrides for practical applications. For these reasons, Mg-based alloys for hydrogen storage systems are generally alloyed with other elements to improve hydrogen sorption properties. In this article, we have added Na to cast Mg–La alloys and achieved a significant improvement in hydrogen absorption kinetics during the first activation cycle. The role of Na in Mg–La has been discussed based on the findings from microstructural observations, crystallography, and first principles calculations based on density functional theory. From our results in this study, we have found that the Na doped surface of Mg–La alloy systems have a lower adsorption energy for H2 compared to Na-free surfaces which facilitates adsorption and dissociation of hydrogen molecules leading to improvement of absorption kinetic. The effect of Na on the microstructure of these alloys, such as eutectic refinement and a density of twins is not highly correlated with absorption kinetics. 相似文献
157.
Bellendir E. N. Aleksandrov A. V. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(2):149-154
Power Technology and Engineering - The major results from the survey and geotechnical monitoring during the leveling of the model foundation of the Zagorsk PSP-2 in test site No. 3 are presented.... 相似文献
158.
Influence of Wheel Blunting on the Machining Precision in CNC Plunge Grinding: Digital Twin Analysis
Akintseva A. V. Pereverzev P. P. Prokhorov A. V. Omel’chenko S. V. 《Russian Engineering Research》2022,42(7):726-730
Russian Engineering Research - The machining precision in grinding a flexible shaft by sharp and blunt wheels is compared for a CNC system with a specified cycle of radial supply velocities. To... 相似文献
159.
Roselle Barretto Rania Marie Buenavista Jared Lou Rivera Shuyu Wang P.V. Vara Prasad Kaliramesh Siliveru 《International Journal of Food Science & Technology》2021,56(7):3125-3137
The demand for food production has been constantly increasing due to rising population. In developed countries, for example, the emergence of regional production of old grains that are rarely utilized, along with the production of commonly consumed grains, has gained importance in recent years. These grains, known collectively as ancient or heirloom grains, have offered both farmers and consumers novel ways of cultivation and products with interesting taste, characteristics and nutritional value. Among the 30 000 plant species known, only five cereals currently provide more than 50% of the world's energy intake – bread wheat (Triticum aestivum), rice (Oryza sativa), sorghum (Sorghum bicolor), millets (Panicum sp.) and maize (Zea mays). The excessive utilization of these selected species has a great potential to cause genetic losses and difficulty in bridging future agricultural demands. Teff (Eragrostis tef), an ancient grain extensively cultivated in countries like Eritrea and Ethiopia, provides promising alternatives for new food uses since its nutritional value is significantly higher than most others cereal grains. The absence of gluten allows flexibility in food utilization since it can be directly substituted to gluten-containing products. The grain also offers an excellent balance of essential amino acids and minerals, which can fulfil the recommended daily intake and eliminates the need for fortification and enrichment. This review provides a general overview of the physical properties and nutritional composition of teff grains related to processing and applications in the food and feed industries. The current status of teff utilization, as well as the challenges in production and commercialization, and future opportunities is presented and discussed. 相似文献
160.
P. Carrasqueira H. Rocha J. M. Dias T. Ventura B. C. Ferreira M. C. Lopes 《International Transactions in Operational Research》2023,30(1):206-223
Radiation therapy is a technology-driven cancer treatment modality that has experienced significant advances over the last decades, due to multidisciplinary contributions that include engineering and computing. Recent technological developments allow the use of noncoplanar volumetric modulated arc therapy (VMAT), one of the most recent photon treatment techniques, in clinical practice. In this work, an automated noncoplanar arc trajectory optimization framework designed in two modular phases is presented. First, a noncoplanar beam angle optimization algorithm is used to obtain a set of noncoplanar irradiation directions. Then, anchored in these directions, an optimization strategy is proposed to compute an optimal arc trajectory. The computational experiments considered a pool of twelve difficult head-and-neck tumor cases. It was possible to observe that, for some of these cases, the optimized noncoplanar arc trajectories led to significant treatment planning quality improvements, when compared with coplanar VMAT treatment plans. Although these experiments were done in a research environment treatment planning software (matRad), the conclusions can be of interest for a clinical setting: automated procedures can simplify the current treatment workflow, produce high-quality treatment plans, making better use of human resources and allowing for unbiased comparisons between different treatment techniques. 相似文献