全文获取类型
收费全文 | 527923篇 |
免费 | 5118篇 |
国内免费 | 928篇 |
专业分类
电工技术 | 9647篇 |
综合类 | 640篇 |
化学工业 | 82052篇 |
金属工艺 | 23951篇 |
机械仪表 | 17732篇 |
建筑科学 | 11561篇 |
矿业工程 | 4428篇 |
能源动力 | 11709篇 |
轻工业 | 38644篇 |
水利工程 | 6305篇 |
石油天然气 | 15300篇 |
武器工业 | 34篇 |
无线电 | 56407篇 |
一般工业技术 | 113708篇 |
冶金工业 | 84865篇 |
原子能技术 | 15601篇 |
自动化技术 | 41385篇 |
出版年
2021年 | 4641篇 |
2019年 | 4496篇 |
2018年 | 8317篇 |
2017年 | 8449篇 |
2016年 | 8885篇 |
2015年 | 5199篇 |
2014年 | 9087篇 |
2013年 | 22842篇 |
2012年 | 13688篇 |
2011年 | 17814篇 |
2010年 | 14220篇 |
2009年 | 16162篇 |
2008年 | 16651篇 |
2007年 | 16339篇 |
2006年 | 13955篇 |
2005年 | 12656篇 |
2004年 | 12468篇 |
2003年 | 12113篇 |
2002年 | 11782篇 |
2001年 | 11830篇 |
2000年 | 11410篇 |
1999年 | 11155篇 |
1998年 | 23678篇 |
1997年 | 17764篇 |
1996年 | 13838篇 |
1995年 | 11004篇 |
1994年 | 10101篇 |
1993年 | 10055篇 |
1992年 | 8097篇 |
1991年 | 8009篇 |
1990年 | 7998篇 |
1989年 | 7784篇 |
1988年 | 7529篇 |
1987年 | 6804篇 |
1986年 | 6831篇 |
1985年 | 7691篇 |
1984年 | 7180篇 |
1983年 | 6847篇 |
1982年 | 6252篇 |
1981年 | 6484篇 |
1980年 | 6207篇 |
1979年 | 6331篇 |
1978年 | 6371篇 |
1977年 | 6943篇 |
1976年 | 8424篇 |
1975年 | 5701篇 |
1974年 | 5663篇 |
1973年 | 5725篇 |
1972年 | 4967篇 |
1971年 | 4501篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
G. V. Martyusha S. A. Semenov T. A. Kartasheva N. V. Zubkova I. A. Timokhin 《Chemistry and Technology of Fuels and Oils》1992,28(8):468-469
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 8, pp. 29–30, August, 1992. 相似文献
992.
993.
994.
The cost of electricity and operating reliability in heavy industry can be key in determining which processes and plants survive in today's competitive market. This paper provides an insight into the planning and implementation of several significant cost saving and reliability improvements at a turn-of-the-century steel mill in Ohio. A clear understanding of what to look for and how to proceed with such projects should provide motivation for others considering similar improvements 相似文献
995.
It is shown that the unique coherence properties of mode-locked lasers can be exploited to provide new opportunities for high-speed data transmission. Using passive Mach-Zehnder optical delay stages, very high bit rate optical data streams constructed from asynchronously combined transmitters can be demultiplexed directly in the optical domain, without imposing restrictions on the source wavelength. Potential implementation and performance of the technique are discussed.<> 相似文献
996.
997.
Papain was immobilized on polymer supports with spacer arms of varying nature and length. As the length of the spacer arm increased, there was a marked increase in the extent of enzyme immobilization and activity of immobilized enzymes. When a long, flexible and hydrophilic polyethylene glycol spacer was introduced between the polystyrene backbone and the functional group used for immobilization, the extent of coupling and enzyme activity increased. Dependence of enzyme activity on the nature and extent of crosslinking and on the nature of the polymeric backbone was investigated. Hydrophilic polyacrylamide-based supports were found to be more efficient supports for immobilization compared to hydrophobic polystyrene-based supports. 相似文献
998.
This paper develops a method for simultaneously designing the power stage and controller for a switching power supply. The method utilizes a numerical optimization procedure, which facilitates computer-aided design. It is found that better performance can be achieved than with a traditional two-step design process, where the power stage and controller are designed sequentially. Optimization and simulation results for a buck power converter are presented to illustrate the design process and benefits 相似文献
999.
FE Nargang KP Künkele A Mayer RG Ritzel W Neupert R Lill 《Canadian Metallurgical Quarterly》1995,14(6):1099-1108
MOM22 is a component of the protein import complex of the mitochondrial outer membrane of Neurospora crassa. Using the newly developed procedure of 'sheltered disruption', we created a heterokaryotic strain harboring two nuclei, one with a null allele of the mom-22 gene and the other with a wild-type allele. Homokaryons bearing the mom-22 disruption could not be isolated, suggesting that mom-22 is an essential gene. The mutant nucleus can be forced to predominate in the heterokaryon through the use of specific nutritional and inhibitor resistance markers. Cultivation of the heterokaryon under conditions favoring the mutant nucleus resulted in selective depletion of MOM22. MOM22-depleted cells did not grow and contained mitochondria with an altered morphology and protein composition. Protein import into isolated, MOM22-depleted mitochondria was abolished for most precursor proteins destined for all subcompartments. In contrast, precursors of MOM19, MOM22 and MOM72 became inserted normally into the outer membrane, defining a novel MOM22-independent import pathway which remained intact in mutant mitochondria. Furthermore, the specific binding of the ADP/ATP carrier to the outer membrane was unaffected, but subsequent transport across the outer membrane did not occur. Our data show that MOM22 is an essential component of Neurospora cells specifically required for the biogenesis of mitochondria. 相似文献
1000.