全文获取类型
收费全文 | 117300篇 |
免费 | 10462篇 |
国内免费 | 6171篇 |
专业分类
电工技术 | 7826篇 |
技术理论 | 9篇 |
综合类 | 8513篇 |
化学工业 | 18359篇 |
金属工艺 | 7135篇 |
机械仪表 | 7317篇 |
建筑科学 | 8761篇 |
矿业工程 | 3646篇 |
能源动力 | 3379篇 |
轻工业 | 11066篇 |
水利工程 | 2467篇 |
石油天然气 | 6567篇 |
武器工业 | 1167篇 |
无线电 | 12847篇 |
一般工业技术 | 12531篇 |
冶金工业 | 5439篇 |
原子能技术 | 1377篇 |
自动化技术 | 15527篇 |
出版年
2024年 | 567篇 |
2023年 | 1920篇 |
2022年 | 3773篇 |
2021年 | 5074篇 |
2020年 | 3817篇 |
2019年 | 3099篇 |
2018年 | 3540篇 |
2017年 | 3902篇 |
2016年 | 3555篇 |
2015年 | 5029篇 |
2014年 | 6227篇 |
2013年 | 7305篇 |
2012年 | 8325篇 |
2011年 | 9030篇 |
2010年 | 8121篇 |
2009年 | 7540篇 |
2008年 | 7574篇 |
2007年 | 7085篇 |
2006年 | 6737篇 |
2005年 | 5540篇 |
2004年 | 3778篇 |
2003年 | 3187篇 |
2002年 | 3044篇 |
2001年 | 2507篇 |
2000年 | 2238篇 |
1999年 | 2228篇 |
1998年 | 1647篇 |
1997年 | 1395篇 |
1996年 | 1300篇 |
1995年 | 1142篇 |
1994年 | 883篇 |
1993年 | 598篇 |
1992年 | 459篇 |
1991年 | 391篇 |
1990年 | 315篇 |
1989年 | 236篇 |
1988年 | 199篇 |
1987年 | 131篇 |
1986年 | 116篇 |
1985年 | 71篇 |
1984年 | 65篇 |
1983年 | 43篇 |
1982年 | 36篇 |
1981年 | 40篇 |
1980年 | 38篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 18篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The texture effect on visual colour difference evaluation was investigated in this study. Five colour centers were selected and textured colour pairs were generated using scanned textile woven fabrics and colour‐mapping technique. The textured and solid colour pairs were then displayed on a characterized cathode ray tube (CRT) monitor for colour difference evaluation. The colour difference values for the pairs with texture patterns are equal to 5.0 CIELAB units in lightness direction. The texture level was represented by the half‐width of histogram, which is called texture strength in this study. High correlation was found between texture strength and visual colour difference for textured colour pairs, which indicates that an increasing of 10 units of texture strength in luminance would cause a decreasing of 0.25 units visual difference for the five colour centers. The ratio of visual difference between textured and solid colour pairs also indicates a high parametric effect of texture. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 341–347, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col. 相似文献
12.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry 相似文献
13.
14.
部分种子成分的特征X射线在等效生物材料中衰减的测定 总被引:6,自引:5,他引:1
用Si(Li)探测器实现了Na、Mg、S、Cl的特征X射线在有机膜中的相对衰减以及与O、K元素的特征X射线能量相当的X射线或轫致辐射在有机膜中的相对衰减,分别得出了它们减的数学描述,并把实验得到不同能量的X射线在有机膜中的质量吸收系数与Berkeley的OCG软件计算出的结果相比,相关都小于30%。 相似文献
15.
This paper investigates the issue of building software in the Internet environment, where local area network (LAN) based
systems are interconnected by links with different bandwidth and do not share file systems. The software is modeled as a directed
acyclic graph. Each node in the graph represents a logical step in processing the software while the edges describe the order
of execution. The problem is to construct the software at a particular LAN with minimum Internet communication cost. An optimal
polynomial algorithm, SOFTCON, with time complexity is presented, where and are the number of nodes and edges in the graph describing the software respectively, is the number of LANs in the Internet environment, and is the time complexity of the network flow algorithm on the flow network with nodes and edges transformed from the directed acyclic graph of the software.
Received: 6 December 1995 / 1 May 1996 相似文献
16.
Selhi H. Christopoulos C. Howe A.F. Hui S.Y.R. 《Energy Conversion, IEEE Transaction on》1996,11(2):287-297
The simulation of a complete induction motor drive is presented. The entire network is modelled using the transmission-line modelling (TLM) technique. The network is split into three sections which are solved independently and are joined together by link transmission-line models. Advantages of this approach are the explicit nature of the algorithm which remains unaltered irrespective of the network topology, unconditional stability, and straightforward modelling of switching elements. Results are presented for a complete drive which illustrate the capabilities and flexibility of the simulation technique 相似文献
17.
本文讨论了用辉光放电法制备氮化硅薄膜时衬底温度、射频功率和气体流量比对薄膜的电导率、介电常数和击穿强度的影响。通过优化生长条件,制备了优质非晶氮化硅薄膜,其介电常数为7.5、击穿强度为5.5MV/cm、电导率为10-13(Ωcm)-1。 相似文献
18.
2,3,4- or 2,3,5-trisubstituted furans were highly regioselectively formed from the cycloisomerization reaction of the same starting cyclopropenes 1 via the subtle choice of the transition metal halides. Under the catalysis of 5 mol % PdCl2(CH3CN)2, 2,3,5-trisubstituted furans 2 were given in 50-88% yields with 95-99% regioselectivities, while 2,3,4-trisubstituted furans 3 were formed in 78-96% yields with 99% regioselectivities under the catalysis of 5 mol % CuI. 相似文献
19.
20.