全文获取类型
收费全文 | 2146篇 |
免费 | 152篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 25篇 |
综合类 | 3篇 |
化学工业 | 491篇 |
金属工艺 | 37篇 |
机械仪表 | 46篇 |
建筑科学 | 69篇 |
矿业工程 | 2篇 |
能源动力 | 73篇 |
轻工业 | 561篇 |
水利工程 | 29篇 |
石油天然气 | 19篇 |
无线电 | 110篇 |
一般工业技术 | 287篇 |
冶金工业 | 284篇 |
原子能技术 | 21篇 |
自动化技术 | 242篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 83篇 |
2020年 | 63篇 |
2019年 | 69篇 |
2018年 | 84篇 |
2017年 | 71篇 |
2016年 | 79篇 |
2015年 | 66篇 |
2014年 | 97篇 |
2013年 | 134篇 |
2012年 | 131篇 |
2011年 | 129篇 |
2010年 | 108篇 |
2009年 | 101篇 |
2008年 | 126篇 |
2007年 | 82篇 |
2006年 | 73篇 |
2005年 | 80篇 |
2004年 | 64篇 |
2003年 | 42篇 |
2002年 | 47篇 |
2001年 | 30篇 |
2000年 | 41篇 |
1999年 | 48篇 |
1998年 | 113篇 |
1997年 | 70篇 |
1996年 | 38篇 |
1995年 | 39篇 |
1994年 | 23篇 |
1993年 | 22篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1974年 | 1篇 |
排序方式: 共有2299条查询结果,搜索用时 15 毫秒
31.
Jesú s Guardiola Soler Juan J. Prieto Marqu s M nica Garcí a Ruiz Guadalupe Ramos Caicedo 《Chemical Engineering Communications》2003,190(3):285-298
The purpose of the present work is to demonstrate the reliability of a digital image processing technique. A CCD (Charge Coupled Device) is used to perform an investigation on the bubble properties of a 2D gas-solid fluidized bed, and the aim of this study is to establish a criterion in order to reject all images that could not be interpreted as bubbles. This may lead to an alteration of the information obtained. The two-dimensional fluidized bed is 20 cm wide and at least 20 cm high, and the field of view of the camera is 12.54 cm wide and 12.99 cm high. In this way, bubbles could be totally or partially placed into this field of view so that a partial image of a bubble could be analyzed as a whole bubble. With this calibration, a geometric decision criterion for the rejection of nonbubble images was developed. 相似文献
32.
33.
Wei Li Mercedes Coughlin Robert L. Albright Richard H. Fish 《Reactive and Functional Polymers》1995,28(1)
We report on the synthesis and reactivity of a polymer-supported o-phenylenediamine hydrochloride ligand, PS-PDHC, using macroporous 6% crosslinked polystyrene-divinylbenzene beads. The PS-PDHC ligand was found to be highly selective to AuCl4− ions in strongly acidic solutions in the presence of other precious metal ions, PdCl42−, PtCl42−, RhCl63−, and RuCl52− (selectivity values: 2.5, Au/Pd; 7.5, Au/Pt; 7, Au/Rh; 2.2, Au/Ru) as well as other transition metal ions, Fe 3+, Cr3+, CU2+, Nit+, and Mn2+. The sorption capacity, selectivity, kinetics of removal and recovery, and solution isotherms have been determined for AuCl4− ions in competition with the above-mentioned metal ions. The relative ease of formation of the anionic complex in 0.5 M HCI, AuCl4− was thought to be the primary reason for its selective ability to bind to the PS-PDHC ligand by an anion-exchange mechanism. Therefore, the effect of the HCI concentration on the kinetics of AuCl4− ion removal from solution was also investigated to clearly show that raising the pH from 0 to 5 caused a dramatic decrease in rate. The AuCl4− ion can be recovered quantitatively from the PS-PDHC beads using a 5% thiourea solution in 0.1 M HCl, allowing the polymer-supported ligand to be reused. 相似文献
34.
Luis Carlos da Silva Ramos Joao Shogiro Tango Angelo Savi Nilson Roberto Leal 《Journal of the American Oil Chemists' Society》1984,61(12):1841-1843
Thirty-six castorbean varieties were surveyed for oil and fatty acid composition, in order to determine variability of these
seed compounds. A large variability of seed oil percentage was observed, ranging from 39.6 to 59.5%. Concerning the fatty
acids, little variability was observed for ricinoleic acid, which was the most abundant in the oil, ranging from 83.65 to
90.00%. The other fatty acids appeared in small concentrations and showed a small range: 0.87 to 2.35, 0.68 to 1.84, 2.96
to 5.64, 3.19 to 5.98, and 0.34 to 0.91%, for palmitic, stearic, oleic, linoleic, and linolenic acid, respectively. Non-significant
correlations were observed between fatty acids and seed oil percentage. However, significant correlations were observed among
fatty acid concentrations: positive and negative ones. These significant correlations could be associated with the biosynthetic
pathways of the fatty acids, which are not fully elucidated. They suggest, however, that selection for a particular fatty
acid will tend to increase those positively correlated, and decrease those negative ones. Selection and plant breeding techniques
could then be applied to modify the oil content of the castorbean seeds, considering the variability observed. For the fatty
acid composition, however, the variability was not large enough to make substantial changes in their concentrations by selection
procedures. More varieties should be surveyed to find out if such variability is available. 相似文献
35.
M. Victoria Ruiz‐Mndez lvaro E. Ramos‐Hinojosa 《European Journal of Lipid Science and Technology》2003,105(7):346-350
Two‐phase decanter olive pomace (TPOP) is the by‐product of a centrifugation system, used to produce olive oil, that separates olive oil and moist pomace. The water content in these olive pomaces is about 70%, while it was 45‐50% in the olive pomace stemming from three‐phase systems (oil, water, and pomace) and 30% in the old press system. The aim of this work is focused on quantification and changes undergone during olive pomace storage in ponds of esters of fatty acids with short‐chain linear alcohols, which can be considered as a refining loss. The results indicate that oil deterioration increases very rapidly, in particular when oil is extracted from the TPOP surface. Special attention should be paid to the storage of TPOP, establishing a maximum of 2 months in all cases. 相似文献
36.
Eduardo Arias-Marín Luis F. Ramos De Valle Oliverio Rodríguez-Fernndez Jesús Rodríguez-Velzquez 《乙烯基与添加剂工艺杂志》1995,1(4):217-222
The effect of elemental sulfur (S8) and tetramethyl thiuram disulfide (TMTD) on the chemical crosslinking of PVC is studied. The tensile strength, elongation at break, and gel content of crosslinked and uncrosslinked PVC molded samples, cured at different times in hot air, are evaluated. It was found that crosslinking PVC with TMTD improves its mechanical properties, and adding S8 produces a slight improvement. Also, the S8 presence accelerated the PVC/TMTD crosslinking reaction when the crosslinking reaction was carried out under shear forces, but not when the curing was done in hot air, where the S8 retards the process. 相似文献
37.
Antonio G. González Ignacio A. Jiménez Mercedes P. Núñez Angel G. Ravelo Isabel L. Bazzocchi Orlando M. Muñoz Marcelino A. Aguilar 《Journal of chemical ecology》1994,20(4):823-830
Three new dihydro--agarofuran sesquiterpenes from two species ofMaytenus were isolated and their structures were elucidated by means of1H and13C NMR studies. The differences and similarities noted in the chemical content of the dihydro--agarofuran sesquiterpenes from the fourMaytenus species from Chile are in line with the taxonomic characterization of these species; their geographical distribution is also given. 相似文献
38.
39.
40.
Roberto R. Expósito Guillermo L. Taboada Sabela Ramos Juan Touriño Ramón Doallo 《Personal and Ubiquitous Computing》2013,17(8):1709-1719
Cloud computing is posing several challenges, such as security, fault tolerance, access interface singularity, and network constraints, both in terms of latency and bandwidth. In this scenario, the performance of communications depends both on the network fabric and its efficient support in virtualized environments, which ultimately determines the overall system performance. To solve the current network constraints in cloud services, their providers are deploying high-speed networks, such as 10 Gigabit Ethernet. This paper presents an evaluation of high-performance computing message-passing middleware on a cloud computing infrastructure, Amazon EC2 cluster compute instances, equipped with 10 Gigabit Ethernet. The analysis of the experimental results, confronted with a similar testbed, has shown the significant impact that virtualized environments still have on communication performance, which demands more efficient communication middleware support to get over the current cloud network limitations. 相似文献