全文获取类型
收费全文 | 13654篇 |
免费 | 851篇 |
国内免费 | 110篇 |
专业分类
电工技术 | 205篇 |
综合类 | 61篇 |
化学工业 | 3533篇 |
金属工艺 | 347篇 |
机械仪表 | 489篇 |
建筑科学 | 515篇 |
矿业工程 | 21篇 |
能源动力 | 951篇 |
轻工业 | 1276篇 |
水利工程 | 188篇 |
石油天然气 | 224篇 |
武器工业 | 4篇 |
无线电 | 1378篇 |
一般工业技术 | 2527篇 |
冶金工业 | 490篇 |
原子能技术 | 95篇 |
自动化技术 | 2311篇 |
出版年
2024年 | 70篇 |
2023年 | 268篇 |
2022年 | 587篇 |
2021年 | 892篇 |
2020年 | 751篇 |
2019年 | 812篇 |
2018年 | 911篇 |
2017年 | 827篇 |
2016年 | 807篇 |
2015年 | 474篇 |
2014年 | 748篇 |
2013年 | 1366篇 |
2012年 | 902篇 |
2011年 | 947篇 |
2010年 | 663篇 |
2009年 | 594篇 |
2008年 | 418篇 |
2007年 | 355篇 |
2006年 | 302篇 |
2005年 | 192篇 |
2004年 | 174篇 |
2003年 | 152篇 |
2002年 | 119篇 |
2001年 | 91篇 |
2000年 | 90篇 |
1999年 | 81篇 |
1998年 | 137篇 |
1997年 | 114篇 |
1996年 | 96篇 |
1995年 | 68篇 |
1994年 | 51篇 |
1993年 | 59篇 |
1992年 | 46篇 |
1991年 | 38篇 |
1990年 | 40篇 |
1989年 | 32篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 34篇 |
1985年 | 27篇 |
1984年 | 27篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 24篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
101.
Behrooz Zareh-Desari Behnam Davoodi Ali Vedaei-Sabegh 《International Journal of Material Forming》2017,10(2):193-203
Multi-point forming is a novel flexible process that is economically suitable for both rapid prototyping and batch production of sheet metal parts. This technique is established based on altering rigid dies by matrices of adjustable punch elements. In this paper, the basic principle of this technique is implemented on deep drawing process. A reconfigurable die was constructed to investigate the multi-point deep drawing process. AA 2024-O Aluminum alloy was designated as test material. The formed specimens were evaluated in terms of dimpling defect, rupture, thickness distribution and dimensional accuracy. The onset of rupture was predicted by integrating the forming limit diagram of employed material with finite element Code. The predicted results were in a reasonable agreement with the experimental tests. It was found that for complete elimination of dimpling defect and acquiring maximum drawing depth, the proper allocation of elastic layer parameters such as thickness and hardness was crucial. The conducted investigations indicated that, in general, dimensional accuracy of formed parts was acceptable. However, for areas with sharp changes in geometry such as corners and side walls, deviation from desired geometry was evident. This phenomenon was remarkably dominant for manufactured parts utilizing softer elastic layer. 相似文献
102.
Ali Eshaghi Mohammad Mashreghi Mahere Rezazade Bazaz Masoud HomayouniTabrizi Majid Darroudi 《IET nanobiotechnology / IET》2017,11(5):517
The aim of this study is to introduce natural‐based polymers, chitosan and starch, to design a remedial nanocomposite, comprising of cerium oxide nanoparticles and silver nanoparticles, to investigate their effects in accelerating wound healing and in wound microbial load. Cerium oxide nanoparticles synthesized in starch solution added to the colloidal dispersion of synthesized silver nanoparticles in chitosan to make a three‐component nanomaterial. Mice were anaesthetized and two parallel full‐thickness round wounds were excised under aseptic conditions with the help of sterile dermal biopsy punch. Furthermore, effects of silver‐chitosan and silver‐cerium‐chitosan nanocomposite had evaluated on rate of wound closure and collagen density and on microbial load of wound in full‐thickness model. Results showed that both silver chitosan and silver‐cerium‐chitosan had significant impact on acceleration of wound closure and collagen content and on reduction of wound microbial load in comparison with control group, which was, received no treatments. However, the silver‐cerium‐chitosan nanocomposite is more potent than silver‐chitosan group and control group in wound closure. The wound healing effects of silver‐cerium‐chitosan nanocomposite are due to unique features of its three components and this nanocomposite promises impressive remedies for clinical application.Inspec keywords: wounds, nanocomposites, nanomedicine, nanoparticles, proteins, cerium, silver, polymers, colloids, patient treatmentOther keywords: biopolymer‐based nanocomposite wound dressing, wound healing properties, wound microbial load, natural‐based polymers, chitosan, remedial nanocomposite, cerium oxide nanoparticles, nanoceria, silver nanoparticles, starch solution, three‐component nanomaterial, synthesised silver nanoparticles, ketamine intraperitoneal injection, silver‐cerium‐chitosan nanocomposite, wound closure, collagen density, wound healing effects, wound care, aseptic conditions, sterile dermal biopsy punch, Ag‐Ce 相似文献
103.
Zainal Abidin Ali Muhammad Aidil Roslan Rosiyah Yahya Wan Yusoff Wan Sulaiman Rustam Puteh 《IET nanobiotechnology / IET》2017,11(2):152
In this study, larvicidal activity of silver nanoparticles (AgNPs) synthesised using apple extract against fourth instar larvae of Aedes aegypti was determined. As a result, the AgNPs showed moderate larvicidal effects against Ae. aegypti larvae (LC50 = 15.76 ppm and LC90 = 27.7 ppm). In addition, comparison of larvicidal activity performance of AgNPs at high concentration prepared using two different methods showed that Ae. aegypti larvae was fully eliminated within the duration of 2.5 h. From X‐ray diffraction, the AgNP crystallites were found to exhibit face centred cubic structure. The average size of these AgNPs as estimated by particle size distribution was in the range of 50–120 nm. The absorption maxima of the synthesised Ag showed characteristic Ag surface plasmon resonance peak. This green synthesis provides an economic, eco‐friendly and clean synthesis route to Ag.Inspec keywords: silver, nanofabrication, X‐ray diffraction, zoology, particle size, nanoparticles, biomedical materials, nanomedicineOther keywords: time 2.5 h, size 50 nm to 120 nm, silver nanoparticle, larvicidal property, instar larvae, Aedes aegypti, larvicidal effect, larvicidal activity performance, X‐ray diffraction, nanoparticle particle size distribution, absorption maxima, silver surface plasmon resonance peak 相似文献
104.
Tuomas Haggren Ali Shah Anton Autere Joona-Pekko Kakko Veer Dhaka Maria Kim Teppo Huhtio Zhipei Sun Harri Lipsanen 《Nano Research》2017,10(8):2657-2666
Light management and electrical isolation are essential for the majority of optoelectronic nanowire (NW) devices.Here,we present a cost-effective technique,based on vapor-phase deposition of parylene-C and subsequent annealing,that provides conformal encapsulation,anti-reflective coating,improved optical properties,and electrical insulation for GaAs nanowires.The process presented allows facile encapsulation and insulation that is suitable for any nanowire structure.In particular,the parylene-C encapsulation functions as an efficient antireflection coating for the nanowires,with reflectivity down to <1% in the visible spectrum.Furthermore,the parylene-C coating increases photoluminescence intensity,suggesting improved light guiding to the NWs.Finally,based on this process,a NW LED was fabricated,which showed good diode performance and a clear electroluminescence signal.We believe the process can expand the fabrication possibilities and improve the performance of optoelectronic nanowire devices. 相似文献
105.
106.
107.
108.
109.
Two dimensional axisymmetric and three-dimensional VOF simulations of gas/liquid transient flow were performed using a multiphase flow algorithm based on the finite-volume method. The results for motion of a multiple bubbles of a heterogeneous sizes aligned horizontally and perpendicular to a hot surface incorporating thermocapillary forces in a rotating liquid in a zero-gravity environment have been presented for the first time. No bubbles broke in any of the cases observed. The results also show that collision and agglomeration of bubbles of unequal sizes diameter are different from those of similar size diameters presented from earlier research work of Alhendal et al. Acta Astronaut. 117, 484–496 (2015). Different flow patterns such as thermocapillary bubble migration, collision, and stream function were observed and presented for the 2-D and 3-D models. 相似文献
110.