全文获取类型
收费全文 | 43777篇 |
免费 | 4881篇 |
国内免费 | 1962篇 |
专业分类
电工技术 | 1276篇 |
综合类 | 2841篇 |
化学工业 | 10554篇 |
金属工艺 | 5668篇 |
机械仪表 | 2450篇 |
建筑科学 | 2595篇 |
矿业工程 | 1997篇 |
能源动力 | 1528篇 |
轻工业 | 2176篇 |
水利工程 | 820篇 |
石油天然气 | 3999篇 |
武器工业 | 260篇 |
无线电 | 2660篇 |
一般工业技术 | 5641篇 |
冶金工业 | 4346篇 |
原子能技术 | 739篇 |
自动化技术 | 1070篇 |
出版年
2024年 | 224篇 |
2023年 | 1053篇 |
2022年 | 1278篇 |
2021年 | 1639篇 |
2020年 | 1855篇 |
2019年 | 1713篇 |
2018年 | 1381篇 |
2017年 | 1615篇 |
2016年 | 1594篇 |
2015年 | 1608篇 |
2014年 | 2416篇 |
2013年 | 2776篇 |
2012年 | 3098篇 |
2011年 | 2980篇 |
2010年 | 2238篇 |
2009年 | 2312篇 |
2008年 | 1971篇 |
2007年 | 2605篇 |
2006年 | 2474篇 |
2005年 | 2210篇 |
2004年 | 1782篇 |
2003年 | 1758篇 |
2002年 | 1446篇 |
2001年 | 1172篇 |
2000年 | 1092篇 |
1999年 | 853篇 |
1998年 | 692篇 |
1997年 | 542篇 |
1996年 | 485篇 |
1995年 | 369篇 |
1994年 | 287篇 |
1993年 | 212篇 |
1992年 | 181篇 |
1991年 | 145篇 |
1990年 | 118篇 |
1989年 | 99篇 |
1988年 | 53篇 |
1987年 | 56篇 |
1986年 | 40篇 |
1985年 | 49篇 |
1984年 | 52篇 |
1983年 | 35篇 |
1982年 | 20篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1959年 | 4篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
建(构)筑物机械拆除方法综述 总被引:1,自引:0,他引:1
介绍了几种常用的建(构)筑物机械拆除方法,对其工作原理、特点、应用条件及局限性加以分析和说明。 相似文献
22.
The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd-Fe-B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd-rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0.0015% at 1073K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523-723K for 1h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet. 相似文献
23.
本文通过对立式旋风水膜除尘器除尘性能的模型试验,揭示了几个主要参数对其除尘性能的影响,确定了合理的取值范围,对该种除尘器的设计和应用提供了依据。 相似文献
24.
本文探讨了影响中厚板厚度波动的因素,结合安钢中板厂2800mm轧机按合同轧制一批交货重量不大于理论重量船板的生产实践,总结了实际生产中实现高精度厚度控制的有效方法。 相似文献
25.
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
26.
Sabha Kesraoui-Ouki Christopher R. Cheeseman Roger Perry 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(2):121-126
This paper assesses the potential of natural zeolite utilization as a low-cost ion-exchange and sorbent material in pollution control and recovery of metals. The improvement of the purity of natural zeolites coupled with their chemical modification capabilities in order to provide specific properties may provide a cost-effective alternative for the treatment of heavy metal contaminated soil and water. The application of natural zeolites in industrial pollution control is becoming important and the level of technical effort is increasingly expanding. The extent of application is unlikely to be related solely to their low cost, but also to improved properties and performance characteristics, which will advance the practical implementation of natural zeolites' technology. 相似文献
27.
J. Weise Dr.‐Ing. O. Yezerska M. Busse M. Haesche V. Zanetti‐Bueckmann M. Schmitt 《Materialwissenschaft und Werkstofftechnik》2007,38(11):901-906
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated. 相似文献
28.
中厚板矫直技术的发展 总被引:13,自引:0,他引:13
本文介绍中厚板产生不平直度的原因,中厚板矫直机的种类,3各种新型矫直机,矫直机产能的确认及中厚板矫直技术的发展。 相似文献
29.
A number of copolymers were synthesised by condensing the 2,4-dinitrophenylhydrazone of resacetophenone with substituted benzoic acids/ phenols and formaldehyde in the presence of sodium hydroxide or hydrochloric acid. The decomposition temperature, solubility and viscosity of the polymers have been determined. The ion-exchange properties have been studied by using a batch equilibrium method. The distribution of a number of metal ions between an aqueous solution and the resin have been measured. A wide range of pH and variable ionic strengths have been investigated. 相似文献
30.
Although the gas metal arc welding (GMAW) process is widely used for joining metals, its planning is still a cumbersome task. The planning procedure involves many complex interrelationships among the process variables and depends heavily on empirical knowledge. Therefore, a solution method that allows a convenient way to represent the domain knowledge and evaluate the process variable relationships is needed. Further, the lack of a strong domain theory to quantify these interrelationships is a deficiency in the planning of the GMAW process. This paper presents a solution method that overcomes this deficiency and introduces a convenient knowledge representation scheme. The solution method considers the planning procedure to be a constraint satisfaction problem (CSP). The AC-4 algorithm is used to obtain arc consistency among nodes in the constraint network and the PC-4 algorithm is applied to obtain path consistency in the network. A modified version of the AC-4 algorithm is developed to reduce the search space and correspondingly reduce the computation time. An example is presented to demonstrate the capability of the method and its potential to reduce lead time. 相似文献