全文获取类型
收费全文 | 307575篇 |
免费 | 35660篇 |
国内免费 | 12075篇 |
专业分类
电工技术 | 16174篇 |
技术理论 | 27篇 |
综合类 | 18286篇 |
化学工业 | 61184篇 |
金属工艺 | 16005篇 |
机械仪表 | 17838篇 |
建筑科学 | 23395篇 |
矿业工程 | 8887篇 |
能源动力 | 8589篇 |
轻工业 | 23621篇 |
水利工程 | 4862篇 |
石油天然气 | 18836篇 |
武器工业 | 1982篇 |
无线电 | 36449篇 |
一般工业技术 | 41923篇 |
冶金工业 | 15230篇 |
原子能技术 | 2856篇 |
自动化技术 | 39166篇 |
出版年
2024年 | 1208篇 |
2023年 | 4581篇 |
2022年 | 7851篇 |
2021年 | 11070篇 |
2020年 | 9705篇 |
2019年 | 10030篇 |
2018年 | 10736篇 |
2017年 | 12075篇 |
2016年 | 11444篇 |
2015年 | 14249篇 |
2014年 | 16984篇 |
2013年 | 20376篇 |
2012年 | 19385篇 |
2011年 | 20415篇 |
2010年 | 18543篇 |
2009年 | 17466篇 |
2008年 | 16703篇 |
2007年 | 15925篇 |
2006年 | 16136篇 |
2005年 | 13884篇 |
2004年 | 10238篇 |
2003年 | 9723篇 |
2002年 | 9863篇 |
2001年 | 8602篇 |
2000年 | 7842篇 |
1999年 | 7916篇 |
1998年 | 6054篇 |
1997年 | 5015篇 |
1996年 | 4709篇 |
1995年 | 3928篇 |
1994年 | 3169篇 |
1993年 | 2199篇 |
1992年 | 1740篇 |
1991年 | 1355篇 |
1990年 | 1048篇 |
1989年 | 814篇 |
1988年 | 601篇 |
1987年 | 374篇 |
1986年 | 313篇 |
1985年 | 223篇 |
1984年 | 162篇 |
1983年 | 127篇 |
1982年 | 132篇 |
1981年 | 108篇 |
1980年 | 82篇 |
1979年 | 43篇 |
1978年 | 27篇 |
1977年 | 21篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
971.
972.
活动式水冷撇渣器是根据高炉冷却壁的工作原理设计的。第一台活动式水冷撇渣器于1993年2月27日在安钢4号高炉投入运行,使用寿命长达17个月零18天,通铁量达到40万t。这种活动式水冷撇渣器具有投产少,收益高,维修方便,安全可靠等优点。 相似文献
973.
DNA and amphiphilic N,N,N‐trimethyl‐N‐hexadecylammonium bromide (THAB) were stoichiometrically mixed together to produce a DNA–lipid complex, which was dissolved in dimethyl sulfoxide (DMSO) at 65°C and then crosslinked with isophorone diisocyanate (IPDI). The obtained organogel swelled reversibly in DMSO, responding to the variation of temperature. Interestingly, we observed that the gel exhibited a temperature‐dependent shape‐memory behavior. Above 65°C, whatever the shape the gel was deformed to, it could retain the new shape as the temperature was decreased to room temperature, while, when the gel was heated to 65°C again, it could recover its initial shape. The shape‐memory characteristic is supposedly originated from the transition between the close‐packed and the destroyed DNA/lipid conformation. The elastic urethane crosslinking bonds between base‐pair sites act as a fixing phase. The gel holds promise in its application as a gentle actuator. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 259–263, 2002 相似文献
974.
Polyurethane acrylate anionomer (PUAA)/silica composite gels were prepared by the sol‐gel reaction of tetraethoxysilane (TEOS) and methacryloxypropyl trimethoxysilane (MPTS) incorporated to PUAA gels by using a swelling method. The formation and structure of composites were confirmed by FTIR, X‐ray diffraction, and SEM. As a result, we found that silica components in composites are located within the ionic domains of their gels and interacted with PUAA via hydrogen bonding. This drastically enhanced the mechanical properties of the composites. Mechanical properties are also improved by MPTS, because MPTS improves the dispersibility and adhesion of silica components in PUAA/silica composite gels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2327–2334, 2002 相似文献
975.
976.
977.
The data obtained on inclusion types and concentrations has been analysed in the present part in terms of their effect on
filtration time and fluidity (measured by the length of solidified metal in quartz tubes). The dross, i.e., the oxide layer
that formed on the surface of the molten metal, was carefully collected and its mass determined; then it was examined in a
scanning electron microscope equipped with an energy-dispersive X-ray system. The results show that inclusions are not the
only parameter to be considered. More importantly, it is Al2O3 (films or particles), which seems to be the deciding factor.
It is found, however, that it is quite difficult to separate the individual role of each parameter using the porous disc filtration
apparatus (PoDFA) technique, i.e., sampling, without disturbing the molten metal. Sampling would introduce undesirable oxides
into the PoDFA crucible, resulting in an artificial increase in the filtration time. Increasing the holding periods of the
molten metal increases the quantity of dross. In all cases, the skimmed dross is wet, i.e., it contains an appreciable amount
of molten metal. The main types of oxides in the dross are MgO, MgAl2O4, Al4C3 and Al2O3.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
978.
本文简要介绍钽酸锂晶体及器件的一些特性,对用该材料制作的21.4MHz宽带滤波器的设计、制作和测试结果作了较详细的介绍,滤波器的带宽达225kHz,矩形系数(BW_(?0dB)/BW_(3dB)为2.66,带外衰减在50dB以上。该材料在做宽带滤波器和压控振荡器方面具有优越性。 相似文献
979.
本文简单地回顾了提高VLSI测试效率所采用的一些手段,讨论了在ASIC测试问题研究中出现的一些新观点、新方法、新动向,以及所取得的成果。在此基础上,文章阐明了ASIC测试技术的发展方向,并着重论述了可望在未来得到发展的,针对ASIC的功能测试方法。 相似文献
980.