全文获取类型
收费全文 | 720943篇 |
免费 | 10532篇 |
国内免费 | 2598篇 |
专业分类
电工技术 | 12941篇 |
综合类 | 1004篇 |
化学工业 | 107448篇 |
金属工艺 | 27654篇 |
机械仪表 | 20931篇 |
建筑科学 | 17489篇 |
矿业工程 | 3417篇 |
能源动力 | 19575篇 |
轻工业 | 61625篇 |
水利工程 | 7412篇 |
石油天然气 | 13600篇 |
武器工业 | 75篇 |
无线电 | 82784篇 |
一般工业技术 | 140876篇 |
冶金工业 | 140498篇 |
原子能技术 | 15581篇 |
自动化技术 | 61163篇 |
出版年
2021年 | 6440篇 |
2020年 | 4695篇 |
2019年 | 6002篇 |
2018年 | 10190篇 |
2017年 | 10073篇 |
2016年 | 10608篇 |
2015年 | 7283篇 |
2014年 | 12149篇 |
2013年 | 32791篇 |
2012年 | 19304篇 |
2011年 | 26714篇 |
2010年 | 20886篇 |
2009年 | 23694篇 |
2008年 | 24206篇 |
2007年 | 23932篇 |
2006年 | 20810篇 |
2005年 | 18977篇 |
2004年 | 18498篇 |
2003年 | 18234篇 |
2002年 | 17352篇 |
2001年 | 17465篇 |
2000年 | 16224篇 |
1999年 | 17195篇 |
1998年 | 44066篇 |
1997年 | 30941篇 |
1996年 | 23701篇 |
1995年 | 17823篇 |
1994年 | 15627篇 |
1993年 | 15428篇 |
1992年 | 11083篇 |
1991年 | 10493篇 |
1990年 | 10226篇 |
1989年 | 9968篇 |
1988年 | 9243篇 |
1987年 | 8314篇 |
1986年 | 8205篇 |
1985年 | 9056篇 |
1984年 | 8483篇 |
1983年 | 7595篇 |
1982年 | 7161篇 |
1981年 | 7246篇 |
1980年 | 6996篇 |
1979年 | 6721篇 |
1978年 | 6623篇 |
1977年 | 7726篇 |
1976年 | 10233篇 |
1975年 | 5653篇 |
1974年 | 5387篇 |
1973年 | 5522篇 |
1972年 | 4527篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Elli Ntakou Ralph Masiello Farnaz Farzan Shay Bahramirad Aleksi Paaso M.A. Nayeem Maigha Maigha Daniel Kushner 《The Electricity Journal》2019,32(4):45-49
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal. 相似文献
22.
John D. Rodney S. Deepapriya M. Cyril Robinson C. Justin Raj Suresh Perumal Byung Chul Kim S. Krishnan S. Jerome Das 《International Journal of Hydrogen Energy》2021,46(54):27585-27596
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting. 相似文献
23.
Stepanova L. N. Kuten M. M. Bobrov A. L. 《Russian Journal of Nondestructive Testing》2021,57(9):753-761
Russian Journal of Nondestructive Testing - The results of amplitude analysis of discrete acoustic emission signals from developing sources such as fatigue cracks are presented. The studies were... 相似文献
24.
Cell surface and secreted proteins provide essential functions for multicellular life. They enter the endoplasmic reticulum (ER) lumen co-translationally, where they mature and fold into their complex three-dimensional structures. The ER is populated with a host of molecular chaperones, associated co-factors, and enzymes that assist and stabilize folded states. Together, they ensure that nascent proteins mature properly or, if this process fails, target them for degradation. BiP, the ER HSP70 chaperone, interacts with unfolded client proteins in a nucleotide-dependent manner, which is tightly regulated by eight DnaJ-type proteins and two nucleotide exchange factors (NEFs), SIL1 and GRP170. Loss of SIL1′s function is the leading cause of Marinesco-Sjögren syndrome (MSS), an autosomal recessive, multisystem disorder. The development of animal models has provided insights into SIL1′s functions and MSS-associated pathologies. This review provides an in-depth update on the current understanding of the molecular mechanisms underlying SIL1′s NEF activity and its role in maintaining ER homeostasis and normal physiology. A precise understanding of the underlying molecular mechanisms associated with the loss of SIL1 may allow for the development of new pharmacological approaches to treat MSS. 相似文献
25.
Pedro Ideia Lorenzo Degli Esposti Carla Caseiro Miguel Alessio Adamiano Michele Iafisco Paula C. Castilho 《International Journal of Applied Ceramic Technology》2021,18(1):235-243
The conversion of food industry by-products to compounds with high added value is nowadays a significant topic, for social, environmental, and economic reasons. In this paper, calcium phosphate-based materials were obtained from black scabbardfish (Aphanopus carbo) bones and grey triggerfish (Balistes capriscus) skin, which are two of the most abundant fish by-products of Madeira Island. Different calcination temperatures between 400 and 1000°C were employed. Materials obtained from calcination of bones of black scabbard fish were composed by homogeneous mixtures of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and β-tricalcium phosphate (β-Ca3(PO4)2, β-TCP). Because of the high biocompatibility of HAp and the good resorbability of β-TCP, these natural biphasic materials could be very relevant in the field of biomaterials, as bone grafts. The ratio between HAp and β-TCP in the biphasic compound was dependent on the calcination temperature. Differently, the material obtained from skin of grey triggerfish contained HAp as the main phase, together with small amounts of other mineral phases, such as halite and rhenanite, which are known to enhance osteogenesis when used as bone substitutes. In both cases, the increase of calcination temperature led to an increase in the particles size with a consequent decrease in their specific surface area. These results demonstrate that from the fish by-products of the most consumed fishes in Madeira Island it is possible to obtain bioceramic materials with tunable composition and particle morphology, which could be promising materials for the biomedical field. 相似文献
26.
Abulyazied Dalia E. Alturki Asma M. Youness Rasha A. Abomostafa H. M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4077-4092
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized... 相似文献
27.
Automation and Remote Control - We consider multicriteria minimax optimization problems with criteria in the form of the maxima of functionals given by the induced norms of linear operators taking... 相似文献
28.
Viktoria M. S. Kjær Loukas Ieremias Dr. Viktorija Daugvilaite Dr. Michael Lückmann Prof. Thomas M. Frimurer Prof. Trond Ulven Prof. Mette M. Rosenkilde Dr. Jon Våbenø 《ChemMedChem》2021,16(17):2623-2627
The G protein-coupled receptor GPR183/EBI2, which is activated by oxysterols, is a therapeutic target for inflammatory and metabolic diseases where both antagonists and agonists are of potential interest. Using the piperazine diamide core of the known GPR183 antagonist (E)-3-(4-bromophenyl)-1-(4-(4-methoxybenzoyl)piperazin-1-yl)prop-2-en-1-one (NIBR189) as starting point, we identified and sourced 79 structurally related compounds that were commercially available. In vitro screening of this compound collection using a Ca2+ mobilization assay resulted in the identification of 10 compounds with agonist properties. To enable establishment of initial structure-activity relationship trends, these were supplemented with five in-house compounds, two of which were also shown to be GPR183 agonists. Taken together, our findings suggest that the agonist activity of this compound series is dictated by the substitution pattern of one of the two distal phenyl rings, which functions as a molecular efficacy-switch. 相似文献
29.
Claudia Paredes Francisco J. Martínez-Vázquez Hamada Elsayed Paolo Colombo Antonia Pajares Pedro Miranda 《Journal of the European Ceramic Society》2021,41(1):892-900
Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds. 相似文献
30.
Gladson S. Chrisben Prasad P. Siva Manickam Bhaskar 《Analog Integrated Circuits and Signal Processing》2021,109(3):571-583
Analog Integrated Circuits and Signal Processing - As the 5G era beckons in the world of communication and information technology, there is a surge in demand for battery-operated, mobile wireless... 相似文献