全文获取类型
收费全文 | 132616篇 |
免费 | 12049篇 |
国内免费 | 7196篇 |
专业分类
电工技术 | 9426篇 |
技术理论 | 8篇 |
综合类 | 10000篇 |
化学工业 | 20132篇 |
金属工艺 | 8532篇 |
机械仪表 | 8778篇 |
建筑科学 | 9965篇 |
矿业工程 | 4372篇 |
能源动力 | 4198篇 |
轻工业 | 8268篇 |
水利工程 | 2928篇 |
石油天然气 | 7887篇 |
武器工业 | 1462篇 |
无线电 | 14909篇 |
一般工业技术 | 14352篇 |
冶金工业 | 6631篇 |
原子能技术 | 1601篇 |
自动化技术 | 18412篇 |
出版年
2024年 | 502篇 |
2023年 | 1809篇 |
2022年 | 3496篇 |
2021年 | 5065篇 |
2020年 | 3792篇 |
2019年 | 3163篇 |
2018年 | 3533篇 |
2017年 | 4171篇 |
2016年 | 3855篇 |
2015年 | 5254篇 |
2014年 | 6734篇 |
2013年 | 7789篇 |
2012年 | 9206篇 |
2011年 | 9793篇 |
2010年 | 9237篇 |
2009年 | 8625篇 |
2008年 | 8497篇 |
2007年 | 8145篇 |
2006年 | 7724篇 |
2005年 | 6503篇 |
2004年 | 4939篇 |
2003年 | 4805篇 |
2002年 | 5267篇 |
2001年 | 4529篇 |
2000年 | 3094篇 |
1999年 | 2750篇 |
1998年 | 1810篇 |
1997年 | 1571篇 |
1996年 | 1519篇 |
1995年 | 1157篇 |
1994年 | 874篇 |
1993年 | 632篇 |
1992年 | 482篇 |
1991年 | 368篇 |
1990年 | 289篇 |
1989年 | 229篇 |
1988年 | 189篇 |
1987年 | 121篇 |
1986年 | 93篇 |
1985年 | 44篇 |
1984年 | 50篇 |
1983年 | 38篇 |
1982年 | 35篇 |
1981年 | 23篇 |
1980年 | 30篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1959年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
Kee S. Moon M. Levy Yong K. Hong H. Bakhru S. Bakhru 《Ferroelectrics Letters Section》2003,30(3):47-57
Advances in the fabrication of solid-solution single crystal relaxor ferroelectrics have made it possible to produce highly efficient piezoelectric crystals, and have attracted renewed interest in the use of these crystals for a new generation of piezoelectric transducers, actuators and sensors. Of particular interest is their incorporation into micro-electromechanical systems (MEMS). In this paper we report on the laser-induced wet chemical etching of lead zinc niobate-lead titanate (PZN-PT) in hydrochloric acid (HCl). Argon-ion laser radiation at power levels up to 4 W is focused to a spot diameter of about 15μm and results in the chemical etching of grooves at patterning speeds up to 5μm/sec. Crystal ion slicing, an ion-implant-based film separation technique, is used in combination with laser etching to form 5 to 10μm-thick patterned and freestanding films for incorporation into micro-electromechanical devices. 相似文献
3.
4.
实验研究了以工业硫酸亚铁及废硫酸为原料,分别采用NaClo_3、KClO_3、H_2O_2及(o_2+NaNO_2)为氧化剂成聚硫酸铁的条件。在以(O_2+NaNO_2)为氧化剂的合成过程中,发现添加微量助催化剂(型号为HG-1、HG-2和HG-3),对提高合成速度及反应过程的稳定性具有重大作用。 相似文献
5.
A human fibroblastic cell line transformed by the SV40-T antigen sequence and continuously cultured for 7 months displayed large periodic variations in cell proliferation. This contrasted with other characteristics of this cell line that remained constant: mosaic cell shape, absence of cell contact inhibition, and predominance of a hypodiploid population. Similar fluctuations in proliferative capacity were also found during the long-term growth of a transformed but nonimmortalized human fibroblastic line prior to senescence, and in the established hamster fibroblastic Nil cell line. This growth pattern suggests a recurrent stimulation of growth in these three transformed cell lines. The proliferation pattern from cultured transformed cells may thus be complex and requires further investigation. These variations presumably influence major cell functions. This observation has important implications for the analysis of data from such cell lines. 相似文献
6.
Yu‐Qing Cao Zhan Zhang Yan‐Xin Guo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1441-1444
A new efficient method for synthesising nitriles, important organic reagents, is reported in this paper. In an environmentally benign solvent‐free system, aryl carboxylic acids were converted into the corresponding nitriles via one‐pot reactions, by amidation with ethyl carbamate followed by dehydration with thionyl chloride, in excellent yields. The results showed that the method has the advantages of lower cost, higher yield, less pollution and greater ease of work‐up. Copyright © 2008 Society of Chemical Industry 相似文献
7.
8.
9.
10.