全文获取类型
收费全文 | 4325篇 |
免费 | 188篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 43篇 |
综合类 | 6篇 |
化学工业 | 963篇 |
金属工艺 | 47篇 |
机械仪表 | 91篇 |
建筑科学 | 339篇 |
矿业工程 | 12篇 |
能源动力 | 128篇 |
轻工业 | 448篇 |
水利工程 | 46篇 |
石油天然气 | 11篇 |
武器工业 | 1篇 |
无线电 | 270篇 |
一般工业技术 | 713篇 |
冶金工业 | 519篇 |
原子能技术 | 16篇 |
自动化技术 | 862篇 |
出版年
2023年 | 32篇 |
2022年 | 45篇 |
2021年 | 63篇 |
2020年 | 54篇 |
2019年 | 82篇 |
2018年 | 93篇 |
2017年 | 87篇 |
2016年 | 112篇 |
2015年 | 74篇 |
2014年 | 144篇 |
2013年 | 312篇 |
2012年 | 191篇 |
2011年 | 288篇 |
2010年 | 214篇 |
2009年 | 218篇 |
2008年 | 217篇 |
2007年 | 222篇 |
2006年 | 172篇 |
2005年 | 175篇 |
2004年 | 130篇 |
2003年 | 108篇 |
2002年 | 120篇 |
2001年 | 70篇 |
2000年 | 86篇 |
1999年 | 86篇 |
1998年 | 90篇 |
1997年 | 90篇 |
1996年 | 87篇 |
1995年 | 56篇 |
1994年 | 53篇 |
1993年 | 51篇 |
1992年 | 52篇 |
1991年 | 34篇 |
1990年 | 36篇 |
1989年 | 38篇 |
1988年 | 32篇 |
1987年 | 40篇 |
1986年 | 34篇 |
1985年 | 37篇 |
1984年 | 53篇 |
1983年 | 44篇 |
1982年 | 40篇 |
1981年 | 33篇 |
1980年 | 33篇 |
1979年 | 21篇 |
1978年 | 29篇 |
1977年 | 22篇 |
1976年 | 27篇 |
1975年 | 26篇 |
1973年 | 14篇 |
排序方式: 共有4515条查询结果,搜索用时 15 毫秒
1.
Emma Layton Anna-Marie Fairhurst Sam Griffiths-Jones Richard K. Grencis Ian S. Roberts 《International journal of molecular sciences》2020,21(23)
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota. 相似文献
2.
3.
Bill Robert Fleck Martin Troya Javier Mayerhofer Tanja Wimmer Manuel 《Software and Systems Modeling》2019,18(2):1017-1046
Software and Systems Modeling - Many model transformation scenarios require flexible execution strategies as they should produce models with the highest possible quality. At the same time,... 相似文献
4.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows. 相似文献
5.
Guangyan Li W. Ian Hamilton Ged Morrisroe Theresa Clarke 《Cognition, Technology & Work》2006,8(1):30-40
A study was carried out using simulation to investigate driver responses to lineside signals and signs at various approach
speeds. The objectives of the study were: (1) to find out whether train speed would significantly affect signal/sign reading;
(2) to examine at which point certain types of signs or signals could be detected or recognised, and (3) to determine a speed
cut-off level above which certain types of signs or signals are no longer recognisable or detectable. Fifty-seven train drivers
from 12 Train Operating Companies in the UK participated in the trials. Twenty different types of lineside signs and ten types
of signals were tested under six different approach speeds ranging from 100 to 350 km/h (62–218 mph). Driver performance measures
were ‘time remaining to the signal/sign’ at the point of detection or recognition, and reading error rate. The results showed
a significant influence of train speed on driver responses to lineside signals/signs and demonstrated a non-linear relationship
between driver responses to signals/signs and approach speed. This has been used to estimate a maximum approach speed limit
within which a specific signal or sign can be correctly detected or recognised. The findings and implications of the study
are discussed in the paper. 相似文献
6.
Calum MacNeil Jaimie T A Dick Ewan Bigsby Robert W Elwood W Ian Montgomery Chris N Gibbins David W Kelly 《Water research》2002,36(1):75-84
In freshwaters. Gammarus spp. are more sensitive to organic pollution than Asellus spp. and the relative abundance of the two taxa has been proposed as a pollution index. We tested the validity of this by examining the relationship between the Gammarus: Asellus (G : A) ratio and (1) a suite of physico-chemical variables. (2) established biotic (average score per taxon, ASPT) and richness (species richness (S) and Ephemeroptera, Plecoptera and Trichoptera families richness (EPT family richness)) indices generated from the macroinvertebrate community. In addition, we investigated a suspected biotic interaction, predation, between Gammarus and Asellus. Both univariate and multivariate analyses showed that the G: A ratio was sometimes responsive to changes in parameters linked to organic pollution, such as BOD5 and nitrate levels. However, the G : A ratio also appeared responsive to variables not directly linked to organic pollution, such as conductivity and distance from source. There were significant positive correlations among the G : A ratio and the ASPT, S and EPT, indicating that changes in the relative abundances of Gammarus and Asellus were reflected in changes in the pollution sensitivity and richness of the wider macroinvertebrate community. A laboratory experiment revealed significant predation of Asellus aquaticus juveniles by Gammarus duebeni celticus adults, but no reciprocal predation. We propose that the G: A ratio may be useful as a crude measure of organic pollution that could supplement more complex indices in a multimetric approach to pollution monitoring or be used for monitoring individual sites, where a simple technique is required for monitoring purposes over a period of time. Also, we urge recognition of the possible role of biotic interactions among taxa used in the generation of pollution indices. 相似文献
7.
如今,通信、计算和先进消费型系统中的复杂设计越来越容易受到最后时刻的设计变更、性能要求的不断攀升以及相关标准演进的影响。设计师必须保持灵活性,以便能够将关键元件的选择推迟到开发过程的后期来进行。 相似文献
8.
9.
Halo effects in rating specific pieces of work, as in educational grading, have received little attention. Grades awarded by 2 independent graders to undergraduate projects were analyzed with a correlated uniqueness model. Grades showed substantial halo despite being awarded by expert assessors at the time of reading the work. There was greater halo between different grades applying to the same section of the project than between grades applying to different sections. Supervisors who had regular contact with the student whose work they were grading showed no more halo than other graders. More reliable graders showed less within-section halo than graders of lower reliability but equal between-sections halo. The halo effects observed cannot be entirely attributable to a unitary general impression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.