全文获取类型
收费全文 | 2856篇 |
免费 | 173篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 50篇 |
综合类 | 6篇 |
化学工业 | 762篇 |
金属工艺 | 86篇 |
机械仪表 | 71篇 |
建筑科学 | 178篇 |
矿业工程 | 2篇 |
能源动力 | 59篇 |
轻工业 | 191篇 |
水利工程 | 9篇 |
石油天然气 | 2篇 |
无线电 | 277篇 |
一般工业技术 | 621篇 |
冶金工业 | 232篇 |
原子能技术 | 11篇 |
自动化技术 | 476篇 |
出版年
2022年 | 33篇 |
2021年 | 57篇 |
2020年 | 40篇 |
2019年 | 56篇 |
2018年 | 69篇 |
2017年 | 82篇 |
2016年 | 85篇 |
2015年 | 99篇 |
2014年 | 100篇 |
2013年 | 163篇 |
2012年 | 149篇 |
2011年 | 198篇 |
2010年 | 126篇 |
2009年 | 135篇 |
2008年 | 139篇 |
2007年 | 132篇 |
2006年 | 128篇 |
2005年 | 97篇 |
2004年 | 73篇 |
2003年 | 75篇 |
2002年 | 52篇 |
2001年 | 55篇 |
2000年 | 45篇 |
1999年 | 46篇 |
1998年 | 80篇 |
1997年 | 59篇 |
1996年 | 62篇 |
1995年 | 42篇 |
1994年 | 24篇 |
1993年 | 42篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 21篇 |
1989年 | 25篇 |
1988年 | 26篇 |
1987年 | 17篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 16篇 |
1979年 | 22篇 |
1978年 | 21篇 |
1977年 | 24篇 |
1976年 | 19篇 |
1974年 | 16篇 |
1972年 | 11篇 |
1970年 | 11篇 |
排序方式: 共有3033条查询结果,搜索用时 0 毫秒
1.
Pavel Strunz Debashis Mukherji Přemysl Beran Ralph Gilles Lukas Karge Michael Hofmann Markus Hoelzel Joachim Rösler Gergely Farkas 《Metals and Materials International》2018,24(5):934-944
An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr2Re3 type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content. 相似文献
2.
A central event in the life of a cellular system is the interaction between the exterior and the interior compartments. Biochemical signals arrive at the cellular surface, bind to their membrane bound receptor followed by a conformational change triggering the release of an internal chemical or electrical signal.This basic principle is followed by all our perceptive abilities like sense of smell or taste, but also by different signal transduction pathways involved in nerve conductivity, vision, sense of touch or hearing. To follow and mimic this principle of parallel registration is one of the aims of modern nanobiotechnology. If we are able to specifically biofunctionalize small arrays of a solid surface, which could be an electrode or a semiconductor, this approach will enable us to build up devices called “biochips” or “biosensors” that allow the determination of bioactive molecules with high specificity at lowest concentrations. Potential pharmacological active substrates might be screened as well as new receptors may be determined. Applications in genomics as well as proteomics are realistic. The major prerequisite for such a broad spectrum of applications is the fabrication of receptive surfaces. Biomolecules have to be surface‐adsorbed in a highly reproducible, oriented and well organised fashion, a task which in biology is taken by the cellular membranes as external or internal receptive surfaces. The physical principles like hydrogen bonds, electrostatic or hydrophobic interactions that lead to such an organized surface are well known. To synthesize molecular building blocks and to position them onto an otherwise unspecific surface is one of the challenges of nanobiotechnology combining biological knowledge and chemical skills with biophysical techniques that allow to handle or analyze even single molecules. 相似文献
3.
The ability of oral lactobacilli to coaggregate with streptococci and actinomycetes was investigated. Of the 7 species of lactobacilli studied, only two were capable of coaggregation and the coaggregation was restricted to streptococci. Lactobacillus salivarius strains (2/4) coaggregated with Streptococcus salivarius, Streptococcus gordonii, Streptococcus crista and tufted Streptococcus sanguis II strains. Lactobacillus fermentum (2/3) coaggregated with S. gordonii and S. sanguis. The coaggregation between L. salivarius and S. salivarius, S. gordonii or tufted S. sanguis II strains was mediated by a protein on the surface of the lactobacilli and was not inhibited by lactose. The coaggregation between L. fermentum and the streptococci was mediated by protein on the surface of the streptococci and was inhibited by lactose. 相似文献
4.
5.
In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH(4+)-N to NO(3-)-N was readily achieved over a feed NH(4+)-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study. 相似文献
6.
Joachim Schummer 《Scientometrics》2007,70(3):669-692
Based on bibliometric methods, this paper describes the global institutionalization of nanotechnology research from the mid-1980s
to 2006. Owing to an extremely strong dynamics, the institutionalization of nanotechnology is likely to surpass those of major
disciplines in only a few years. A breakdown of the relative institutionalizations strengths by the main geographical regions,
countries, research sectors, disciplines, and institutional types provides a very diverse picture over the time period because
of different national science policies. The results allow a critical assessment of the different science policies based on
the relative institutionalizations strengths as well as the conclusion that the institutionalization process has run out of
control of individual governments who once induced the development. 相似文献
7.
8.
9.