全文获取类型
收费全文 | 219900篇 |
免费 | 16175篇 |
国内免费 | 9107篇 |
专业分类
电工技术 | 12082篇 |
技术理论 | 13篇 |
综合类 | 11696篇 |
化学工业 | 35532篇 |
金属工艺 | 12778篇 |
机械仪表 | 12585篇 |
建筑科学 | 14537篇 |
矿业工程 | 5583篇 |
能源动力 | 6650篇 |
轻工业 | 14615篇 |
水利工程 | 3619篇 |
石油天然气 | 12077篇 |
武器工业 | 1403篇 |
无线电 | 25346篇 |
一般工业技术 | 31628篇 |
冶金工业 | 15786篇 |
原子能技术 | 2688篇 |
自动化技术 | 26564篇 |
出版年
2024年 | 912篇 |
2023年 | 3484篇 |
2022年 | 6543篇 |
2021年 | 8802篇 |
2020年 | 6657篇 |
2019年 | 5402篇 |
2018年 | 6349篇 |
2017年 | 7018篇 |
2016年 | 6415篇 |
2015年 | 8090篇 |
2014年 | 10150篇 |
2013年 | 13533篇 |
2012年 | 13564篇 |
2011年 | 14647篇 |
2010年 | 12399篇 |
2009年 | 12067篇 |
2008年 | 11432篇 |
2007年 | 10791篇 |
2006年 | 10622篇 |
2005年 | 9133篇 |
2004年 | 6444篇 |
2003年 | 5505篇 |
2002年 | 5029篇 |
2001年 | 4679篇 |
2000年 | 4447篇 |
1999年 | 5104篇 |
1998年 | 5498篇 |
1997年 | 4542篇 |
1996年 | 4126篇 |
1995年 | 3162篇 |
1994年 | 2529篇 |
1993年 | 2058篇 |
1992年 | 1626篇 |
1991年 | 1353篇 |
1990年 | 1085篇 |
1989年 | 945篇 |
1988年 | 733篇 |
1987年 | 652篇 |
1986年 | 571篇 |
1985年 | 504篇 |
1984年 | 417篇 |
1983年 | 386篇 |
1982年 | 385篇 |
1981年 | 363篇 |
1980年 | 410篇 |
1979年 | 370篇 |
1978年 | 319篇 |
1977年 | 439篇 |
1976年 | 655篇 |
1975年 | 324篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
橡胶卷材挤出连续硫化生产线的结构特色与工作原理 总被引:1,自引:0,他引:1
介绍了橡胶防水防腐卷材挤出连续硫化生产线的结构、特点和工作原理;指出在目前国内同类设备中,该生产设备具有先进性,并可替代引进设备。 相似文献
92.
93.
Jian-Bo Yang 《国际自动化与计算杂志》2006,3(1):I0001-I0002
The UK-China Research Network on Intelligent Automation, Computing and Manufacturing has been established since September 2004 by grants from the Engineering and Physical Sciences Research Council (EPSRC) of the UK and the National Natural Science Foundation of China. The initiative of the network is motivated by the last visit of the UK Science Minister Lord Sainsbury to China to open the first UK-China Hi-Tech Forum and by the current EPSRC initiative to set up specific network programmes in collaboration with partners in China. 相似文献
94.
D. C. Peets R. Liang C. Stock W. J. L. Buyers Z. Tun L. Taillefer R. J. Birgeneau D. A. Bonn W. N. Hardy 《Journal of Superconductivity and Novel Magnetism》2002,15(6):531-534
We have grown cubic centimeter-size crystals of YBa2Cu3O x suitable for neutron studies, by a top-seeded melt-growth technique. Growth conditions were optimized with an eye toward maximizing phase purity. It was found that the addition of 2% Y2BaCuO5 and 0.5% Pt (by mass) were required to prevent melt loss and to obtain the highest crystallinity. A neutron diffraction study on a mosaic of six such crystals found that the final Y2BaCuO5 concentration was 5%, while other impurity phases comprised less than 1% by volume. The oxygen content was set to x = 6.5, the crystals were detwinned, and then carefully annealed to give the well-ordered ortho-II phase. The neutron study determined that 70% of the mosaic's volume was in the majority orthorhomic domain. The neutron (006) and (110) rocking curve widths were ~1° per crystal and ~2.2° for the mosaic, and the oxygen chain correlation lengths were >100 Å in the a- and b-directions and ~50 Å in the c-direction. 相似文献
95.
针对单轴传动滚切式双边剪生产过程中出现的薄钢板经双边剪剪后出现“错牙”及“飞边”的问题,从多个方面入手对薄钢板出现“错牙”及“飞边”的原因进行了分析对比,提出了相应的解决方案,对今后滚切式双边剪的设计、制造及安装调试有借鉴和参考价值。 相似文献
96.
文章通过分析多相流模拟井的实际工作要求 ,提出了简单实用的流量自动控制模型。应用成型的计算机数据采集和控制模块及稳定可靠的流量控制部件 ,实现了各相流量的自动控制过程。该流量自动控制系统调节精度高、速度快、整体造价低 ,在实际应用中取得了良好的效果。 相似文献
97.
98.
J.Z. ZhaoT.S. Chen 《International Journal of Heat and Mass Transfer》2002,45(11):2265-2276
The inertia effect on the onset of thermal instability in natural convection flow over heated horizontal and inclined flat plates embedded in fluid-saturated porous media is analyzed. The linear non-parallel flow model is employed in the instability analysis, which takes into account the streamwise variation as well as the transverse variation of the disturbance amplitude functions. The set of partial differential equations for the disturbance amplitude functions are converted to a system of homogeneous linear ordinary differential equations with homogeneous boundary conditions by the local non-similarity method. The resulting eigenvalue problem is then solved by an implicit finite-difference method. Representative neutral stability curves and critical Rayleigh numbers are presented. It has been found that as the angle of inclination relative to the horizontal increases, the surface heat transfer rate increases, whereas the flow becomes more stable to the vortex mode of instability. Also, as the inertia effect, expressed in terms of Forchheimer number, Fr, increases, the heat transfer rate decreases, but the flow becomes more stable. It is demonstrated that the non-parallel flow model predicts a more stable flow than the parallel flow model. 相似文献
99.
Y. G. Wang H. Q. Ye K. H. Kuo X. J. Feng S. Z. Long G. L. Lao 《Journal of Materials Science》1991,26(23):6325-6330
The microstructures of unhydrated calcium aluminosulphate Ca4Al6SO16 and Ca3SrAl6SO16 have been studied by high-resolution electron microscopy (HREM). The results showed that twinning and twinned slabs could be introduced taking the [1 1 2] direction as the twin axis so that it seems to be coincident with the law of twinning formed in body-centred cubic structures. A previously reported superlattice with a repeat period twice that of the fundamental structure along the 〈1 1 0〉 direction has also been found in both matrix and twin variants. The close intergrowth of Ca3SrAl6SO16 and another phase, possibly Sr3Al2O6 existing as an inclusion between these two twin variants, was determined and clearly revealed by electron diffraction and HREM images. The coherent interphase boundaries and orientation relationship between them can also be deduced. 相似文献
100.
Triton polymers are commercial surfactants whose molecular weight distributions are conventionally determined by means of high-performance liquid chromatography (HPLC). However, in the case of the important octylphenol ethoxylates [p-C8H17-C6H4-O-(CH2CH2O)n-H], HPLC cannot resolve individual oligomers of high molecular weight Triton surfactants (e.g., greater than 2000 u or so; u = unified atomic mass unit). In this paper, we show that laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD/FT/ICR/MS) provides a simple and accurate measure of such Triton surfactant molecular weight distributions up to at least 3500 u, based on a single-shot laser pulse measurement of a few seconds duration. Comparison of LD/FT/ICR/MS and HPLC molecular weight distributions of low molecular weight surfactants shows that laser desorption/ionization produces minimal fragmentation and thus offers an accurate measure of the relative abundances of the neutral oligomers, without the need for prior chromatographic separation of the components. Moreover, for all Triton polymer molecular weight distributions (700-3000 u), LD/FT/ICR/MS provides much more highly resolved profiles of oligomer relative abundances. Finally, LD/FT/ICR/MS reveals the presence of poly(ethylene oxide) side products of the polymerization process, which are not observed by HPLC with conventional ultraviolet absorption detection. 相似文献