全文获取类型
收费全文 | 86871篇 |
免费 | 7886篇 |
国内免费 | 4408篇 |
专业分类
电工技术 | 5870篇 |
技术理论 | 6篇 |
综合类 | 6368篇 |
化学工业 | 13816篇 |
金属工艺 | 5166篇 |
机械仪表 | 5222篇 |
建筑科学 | 7455篇 |
矿业工程 | 2295篇 |
能源动力 | 2522篇 |
轻工业 | 5612篇 |
水利工程 | 1627篇 |
石油天然气 | 4486篇 |
武器工业 | 765篇 |
无线电 | 10329篇 |
一般工业技术 | 10494篇 |
冶金工业 | 3770篇 |
原子能技术 | 1006篇 |
自动化技术 | 12356篇 |
出版年
2024年 | 418篇 |
2023年 | 1457篇 |
2022年 | 2352篇 |
2021年 | 3489篇 |
2020年 | 2513篇 |
2019年 | 2168篇 |
2018年 | 2405篇 |
2017年 | 2654篇 |
2016年 | 2370篇 |
2015年 | 3343篇 |
2014年 | 4004篇 |
2013年 | 4893篇 |
2012年 | 5384篇 |
2011年 | 5745篇 |
2010年 | 5236篇 |
2009年 | 5038篇 |
2008年 | 5054篇 |
2007年 | 4850篇 |
2006年 | 5026篇 |
2005年 | 4198篇 |
2004年 | 3079篇 |
2003年 | 2967篇 |
2002年 | 3298篇 |
2001年 | 2876篇 |
2000年 | 2234篇 |
1999年 | 2338篇 |
1998年 | 1708篇 |
1997年 | 1460篇 |
1996年 | 1431篇 |
1995年 | 1198篇 |
1994年 | 936篇 |
1993年 | 721篇 |
1992年 | 611篇 |
1991年 | 431篇 |
1990年 | 306篇 |
1989年 | 257篇 |
1988年 | 219篇 |
1987年 | 136篇 |
1986年 | 79篇 |
1985年 | 76篇 |
1984年 | 48篇 |
1983年 | 35篇 |
1982年 | 45篇 |
1981年 | 24篇 |
1980年 | 30篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1959年 | 2篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
3.
4.
DCS的现状与发展趋势 总被引:1,自引:0,他引:1
钟霖田 《自动化与仪器仪表》1994,(3):1-6
叙述DCS的进展。目前的DCS正面临来自用户需求的挑战,为保住全球市场竞争优势,制造加工行业用户需要建立集过程控制数据与商业信息于一体的CIMS。未来DCS应具备服从国际标准的开放性和互换操作性。以ISP现场总线为基础的系统结构可能成为未来的DCS。提高应用水平有助于发展未来的DCS 相似文献
5.
本文提出新型布线算法,集李氏迷宫法与线搜索法的长处为一体,以饱和带法进行动态排序,以线搜索法确定借孔位置,然后用李氏法进行单层布线,获得最佳路径,从而达到线型好,布通率高的效果。 相似文献
6.
W. F. Flanagan Lijun Zhong B. D. Lichter 《Metallurgical and Materials Transactions A》1993,24(3):553-559
A model is proposed to explain transgranular-stress corrosion cracking (T-SCC) in face-centered cubic (fcc) materials. Crack
propagation is shown to be anisotropic, in that growth near {110} < 001> is discontinuous due to crack arrest by dislocation
blunting whereas growth away from this growth orientation is continuous. For the former case, renucleation of arrested cracks
involves active dissolution of shear bands at the crack tip, which changes the stress state at Lomer-Cottrell locks, causing
them to fail by cleavage. Once the crack is nucleated, its instantaneous macroscopic crack-growth velocity is considered to
be comprised of multiple nucleation of microcracks with intervening arrests. This microcracking results from the interaction
of the stress fields from neighboring cracks which are forming simultaneously, the crack-opening constraint due to ligaments
which act as “bridges” behind the crack front, and the localized dissolution at the microcrack tip which affectsK
IC and leads to the “cobblestone” appearance. Experimental evidence and theoretical considerations are presented to support
the model. The system studied was Cu-25 at. pct Au in 0.6 M NaCl solution at potentials between 300 and 400 mV (sce), which
precludes hydrogen embrittlement.
This article is based on a presentation made in the symposium “Quasi-Brittle Fracture” presented during the TMS fall meeting,
Cincinnati, OH, October 21–24, 1991, under the auspices of the TMS Mechanical Metallurgy Committee and the ASM/MSD Flow and
Fracture Committee. 相似文献
7.
8.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
9.
10.
Generalized difference control of parallel streams temperatures 总被引:1,自引:0,他引:1
A furnace with multiple parallel passes and multiple burners is commonly seen in petroleum refineries. In order to maintain the furnace running in a safe, stable, and high-efficiency state it is necessary to control the outlet temperatures of the multiple passes to be the same. Due to the fact that the process of the oil heating in such furnace is nonlinear, multivariable, time varying, has serious coupling among passes, has frequent dynamic changes and a large time delay, traditional control methods have trouble in controlling these temperatures, and some advanced control methods, including predictive control, adaptive control, and robust control, are usually too complex for convenient use. In this paper, a control technique, called differences control technique (DsCT), is proposed to distribute the stream flowrates such that the stream temperatures are as identical as possible. The principle of the proposed technique is explained and demonstrated, and the results of its application to a real-life petroleum refinery furnace are also reported. The DsCT technique has the following advantages: it does not need complicated design procedures, the controller structure is simple, it is easy to apply, and it can be canonically applied to furnaces with different number of passes. 相似文献