全文获取类型
收费全文 | 512篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 5篇 |
综合类 | 1篇 |
化学工业 | 138篇 |
金属工艺 | 7篇 |
机械仪表 | 9篇 |
建筑科学 | 12篇 |
能源动力 | 14篇 |
轻工业 | 23篇 |
水利工程 | 3篇 |
无线电 | 58篇 |
一般工业技术 | 95篇 |
冶金工业 | 14篇 |
原子能技术 | 6篇 |
自动化技术 | 153篇 |
出版年
2023年 | 10篇 |
2022年 | 31篇 |
2021年 | 23篇 |
2020年 | 18篇 |
2019年 | 24篇 |
2018年 | 22篇 |
2017年 | 13篇 |
2016年 | 28篇 |
2015年 | 26篇 |
2014年 | 31篇 |
2013年 | 36篇 |
2012年 | 45篇 |
2011年 | 39篇 |
2010年 | 35篇 |
2009年 | 28篇 |
2008年 | 18篇 |
2007年 | 20篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 6篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有538条查询结果,搜索用时 15 毫秒
81.
Rui Xia Zhaofu Fei Nikita Drigo Felix D. Bobbink Zhangjun Huang Rokas Jasinas Marius Franckevi
ius Vidmantas Gulbinas Mounir Mensi Xiaodong Fang Cristina Roldn‐Carmona Mohammad Khaja Nazeeruddin Paul J. Dyson 《Advanced functional materials》2019,29(22)
Recent years have witnessed considerable progress in the development of solar cells based on lead halide perovskite materials. However, their intrinsic instability remains a limitation. In this context, the interplay between the thermal degradation and the hydrophobicity of perovskite materials is investigated. To this end, the salt 1‐(4‐ethenylbenzyl)‐3‐(3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctylimidazolium iodide (ETI), is employed as an additive in hybrid perovskites, endowing the photoactive materials with high thermal stability and hydrophobicity. The ETI additive inhibits methylammonium (MA) permeation in methylammonium lead triiodide (MAPbI3) occurring due to intrinsic thermal degradation, by inhibiting out‐diffusion of the MA+ cation, preserving the pristine material and preventing decomposition. With this simple approach, high efficiency solar cells based on the unstable MAPbI3 perovskite are markedly stabilized under maximum power point tracking, leading to greater than twice the preserved efficiency after 700 h of continuous light illumination and heating (60 °C). These results suggest a strategy to tackle the intrinsic thermal decomposition of MAI, an essential component in all state‐of‐the‐art perovskite compositions. 相似文献
82.
83.
84.
Gillian Butler Marius Collomb Brita Rehberger Roy Sanderson Mick Eyre Carlo Leifert 《Journal of the science of food and agriculture》2009,89(4):697-705
BACKGROUND: Different conjugated linoleic acid (CLA) isomers are known to have contrasting physiology or health effects and there is growing evidence that the profile of natural isomers in milk is influenced by the production system. This survey is the first to compare feeding regimes and concentrations of 14 CLA isomers in milk from three production systems in the UK. RESULTS: Total CLA and seven isomers (including C18:2 c9t11 which comprised > 80% of total) were significantly higher in milk from both organically certified and non‐certified low input (LI) systems compared with milk from conventional high input farms. Sampling date also affected concentrations of total CLA and nine isomers; being lowest in March and highest in August. Seasonal differences were greater in milk from LI herds, thought to be due to changes in herbage and/or stage of lactation. Multivariate analysis showed a strong positive relationship between several CLA isomers and increasing levels of fresh forage in the diet. CONCLUSIONS: These results add to the evidence on how management adjustment may improve the profile of CLA isomers in milk fat, although animal or human intervention studies are required to identify the effects of consuming milk with different CLA levels and isomer profiles on human health. Copyright © 2009 Society of Chemical Industry 相似文献
85.
Corneliu Sergiu Stan Ioan Rosca Daniel Sutiman Marius Sebastian Secula 《中国稀土学报(英文版)》2012,30(5):401-407
The preparation of two highly luminescent europium(III) and terbium(III) complexes with succinimide(SI) and N-hydroxysuccinimide(NHSI) were reported,which were further investigated through elemental chemical analysis,thermal analysis,FT-IR,powder X-ray diffraction,SEM and fluorescence spectroscopy.Data collected through these analysis revealed the formation of the Eu(III) and Tb(III) complexes with the above mentioned ligands at a metal to ligand(M:L) molar ratio of 1:3.Interesting conclusions regarding the efficient sensitization through the coordination site of the lanthanide luminescent centers were retained from the photoluminescent spectra investigation.Strong luminescence emission was observed in case of Eu(III)-SI and Tb(III)-NHSI complexes while the corresponding Eu(III)-NHSI and Tb(III)-SI complexes exhibited no photo luminescent properties.Newly obtained luminescent lanthanide complexes may be of particular interest for various applications in optoelectronics. 相似文献
86.
Biodiesel production using enzymatic transesterification - Current state and perspectives 总被引:1,自引:0,他引:1
Biodiesel has attracted considerable interest in recent years as an alternative, biodegradable and nonpolluting transportation fuel. Conventional alkaline process for biodiesel production are energy-consuming and generate undesirable by-products such as soaps, that make difficult the separation and purification of biodiesel.Particular attention has been dedicated to the use of lipases as biocatalysts for biodiesel production due to their favorable conversion rate obtained in gentle conditions and relatively simple downstream processing steps for the purification of biodiesel and by-products. However, comparatively to conventional chemical processes, the major obstacles for enzymatic production of biodiesel remain the cost of lipases, the relatively slower reaction rate and lipases inactivation caused by methanol and glycerol.This review evaluates the current status and perspectives for enzymatic biodiesel production and indicates the key operational variables that influence lipase activity and stability together with the technological solutions for industrial implementation of enzymatic process. 相似文献
87.
88.
89.
Alemgena A. Araya Marius Huurman André A. A. Molenaar Lambert J. M. Houben 《Materials and Structures》2012,45(5):695-705
In many developing countries, where resources are at premium, thin asphalt layers or chip seals are widely used to provide
a durable all weather pavement surfacing. In such pavements the role of granular layers is very important in the general performance
of the structure. Pavement designs in these countries are empirical in nature and rely on simple input parameters like California
Bearing Ratio (CBR) values. Although widely applicable the traditional CBR test does not provide the mechanical properties
such as resilient and permanent deformation characteristics of granular road materials. This paper documents the characterization
technique developed to determine the mechanical behavior of granular (sub-) base materials based on CBR test using repeated
load cycles. The confining pressure developed in the complex CBR stress state is estimated using strain gauges. Finite Element
analysis has been attempted to model the repeated load CBR (RL-CBR) and derive an equivalent resilient modulus. Furthermore,
a large scale cyclic load triaxial test was carried out on coarse unbound granular materials (UGMs) to validate the result
of the RL-CBR. The RL-CBR test reasonably estimates the resilient modulus of UGMs which can be used as an input in mechanistic
pavement design analysis in the absence of triaxial testing facilities. 相似文献
90.
We have analyzed data published by others reporting the solubility of helium in liquid hydrogen, oxygen, and methane, and of nitrogen in liquid oxygen, to develop empirical correlations for the mole fraction of these pressurant gases in the liquid phase as a function of temperature and pressure. The data, compiled and provided by NIST, are from a variety of sources and covers a large range of liquid temperatures and pressures. The correlations were developed to yield accurate estimates of the mole fraction of the pressurant gas in the cryogenic liquid at temperature and pressures of interest to the propulsion community, yet the correlations developed are applicable over a much wider range. The mole fraction solubility of helium in all these liquids is less than 0.3% at the temperatures and pressures used in propulsion systems. When nitrogen is used as a pressurant for liquid oxygen, substantial contamination can result, though the diffusion into the liquid is slow. 相似文献