全文获取类型
收费全文 | 68324篇 |
免费 | 5787篇 |
国内免费 | 2961篇 |
专业分类
电工技术 | 3873篇 |
技术理论 | 10篇 |
综合类 | 4550篇 |
化学工业 | 11350篇 |
金属工艺 | 3647篇 |
机械仪表 | 3926篇 |
建筑科学 | 5412篇 |
矿业工程 | 1821篇 |
能源动力 | 1933篇 |
轻工业 | 5254篇 |
水利工程 | 1292篇 |
石油天然气 | 3629篇 |
武器工业 | 528篇 |
无线电 | 8267篇 |
一般工业技术 | 8484篇 |
冶金工业 | 3303篇 |
原子能技术 | 731篇 |
自动化技术 | 9062篇 |
出版年
2024年 | 210篇 |
2023年 | 1123篇 |
2022年 | 1831篇 |
2021年 | 2797篇 |
2020年 | 2208篇 |
2019年 | 1754篇 |
2018年 | 2013篇 |
2017年 | 2089篇 |
2016年 | 2044篇 |
2015年 | 2666篇 |
2014年 | 3347篇 |
2013年 | 3928篇 |
2012年 | 4364篇 |
2011年 | 4792篇 |
2010年 | 3936篇 |
2009年 | 3755篇 |
2008年 | 3736篇 |
2007年 | 3478篇 |
2006年 | 3325篇 |
2005年 | 2881篇 |
2004年 | 2145篇 |
2003年 | 1903篇 |
2002年 | 1744篇 |
2001年 | 1558篇 |
2000年 | 1700篇 |
1999年 | 2003篇 |
1998年 | 1708篇 |
1997年 | 1396篇 |
1996年 | 1377篇 |
1995年 | 1146篇 |
1994年 | 998篇 |
1993年 | 698篇 |
1992年 | 544篇 |
1991年 | 388篇 |
1990年 | 334篇 |
1989年 | 302篇 |
1988年 | 216篇 |
1987年 | 144篇 |
1986年 | 104篇 |
1985年 | 76篇 |
1984年 | 56篇 |
1983年 | 41篇 |
1982年 | 49篇 |
1981年 | 32篇 |
1980年 | 31篇 |
1979年 | 13篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 40 毫秒
941.
对农田水利规划设计的重要性进行了阐述,并分析、研究了小型农田水利规划设计的要点和标准,希望可以为我国水利工程建设提供一定的借鉴。 相似文献
942.
943.
944.
945.
马铃薯淀粉渣的羧甲基化研究 总被引:5,自引:0,他引:5
研究了马铃薯淀粉渣与氯乙酸进行羧甲基化反应的一般规律,考察了反应温度、反应时间、原料配比等因素对产物取代度的影响,通过正交试验,找到了最佳反应条件,并对产物性能进行了测试。 相似文献
946.
聚丙烯催化剂进展及应用 总被引:1,自引:0,他引:1
介绍了聚丙烯(PP)催化剂、工艺技术的进展及近十几年世界新开发的金属茂催化剂的结构、特点及用于生产问规聚丙烯的实例。金属茂催化剂用于PP生产,为开发高性能PP产品,提高市场竞争能力提供了可能。 相似文献
947.
Deutsch–Jozsa algorithm has been implemented via quantum adiabatic evolutions by Das et al. (Phys Rev A 65:062310, 2002) and Wei et al. (Phys Lett A 354:271, 2006). In the latter literature, the authors have shown a modified version of the adiabatic evolution which can improve the performance of the algorithm of S. Das et al’s to constant time. In this paper, we also improve the algorithm of S. Das et al’s in a constant time but by using a different construction of adiabatic evolution, i.e., adding ancillary qubits. The algorithm in this paper provides an alternative option to potential users. 相似文献
948.
In this paper, we first uncover a fact that a partial adiabatic quantum search with \(O(\sqrt{N/M})\) time complexity is in fact optimal, in which \(N\) is the total number of elements in an unstructured database, and \(M\) ( \(M\ge 1\) ) of them are the marked ones(one) \((N\gg M)\) . We then discuss how to implement a partial adiabatic search algorithm on the quantum circuit model. From the implementing procedure on the circuit model, we can find out that the approximating steps needed are always in the same order of the time complexity of the adiabatic algorithm. 相似文献
949.
This paper introduces a passive degassing mechanism using textured surfaces to trap and transport bubbles, and then using hydrophobic porous membranes to vent out bubbles in a microfluidic system. The bubble trapping ability is achieved by creating nanostructures to promote bubble nucleation and coalescence on the sidewalls of KOH-etched concave pits in a silicon substrate. The substrate, which is bonded with a porous membrane, is placed in a liquid system with chemically generated CO2 bubbles to examine the degassing ability. The results validate that the bubbles can be easily trapped on the surfaces with nanostructures, and then vented through the porous membrane. Our proposed approach possesses the advantage of simple fabrication, great structure robustness, and effective bubble trapping and removing abilities, which show their great potential as economic, passive means of preventing the gas byproducts from blocking surfaces and improving the efficiency of microfluidic systems during operations. 相似文献
950.
Duanping Sun Jing Lu Zuanguang Chen Yanyan Yu Yinbao Li 《Microfluidics and nanofluidics》2014,17(5):831-842
The formation of three-dimensional (3D) multicellular cell spheroids such as microspheres and embryoid bodies has recently gained much attention as a useful cell culture technique, but few studies have investigated the suitability of glass for spheroids formation and culture. In this work, we present a novel three-dimensional microfluidic device made of poly(dimethylsiloxane) (PDMS) and glass for the easy and rapid synthesis and culture of tumor spheroid. The cell culture unit is composed of an array of microwells on the bottom of a glass plate, bigger microwells and elastomeric microchannels on the top of a PDMS plate. Cell suspension can be easily introduced into the cell culture unit and exchange with the external liquid environment by the microfluidic channels. A single tumor spheroid can be formed and cultured in each glass cell culture chamber, the surface of which was modified with poly(vinyl alcohol) to render it to be resistant to cell adhesion. As the cell culture medium could be replaced, spheroids of the human breast cancer (MCF-7) cells were cultured on the chip for 3 days, reaching the diameters of about 150 μm. Furthermore, the MCF-7 cells were successfully cultured on the chip in 2D and 3D culture modes. Results have shown that glass is well suitable for multicellular tumor spheroids culture. The established platform provides a convenient and rapid method for tumor spheroid culture, which is also adaptable for anticancer drug screening and fundamental biomedical research in cell biology. 相似文献