全文获取类型
收费全文 | 3843篇 |
免费 | 131篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 77篇 |
综合类 | 6篇 |
化学工业 | 976篇 |
金属工艺 | 64篇 |
机械仪表 | 59篇 |
建筑科学 | 285篇 |
矿业工程 | 17篇 |
能源动力 | 78篇 |
轻工业 | 607篇 |
水利工程 | 23篇 |
石油天然气 | 11篇 |
无线电 | 252篇 |
一般工业技术 | 515篇 |
冶金工业 | 468篇 |
原子能技术 | 27篇 |
自动化技术 | 513篇 |
出版年
2022年 | 41篇 |
2021年 | 49篇 |
2020年 | 38篇 |
2019年 | 51篇 |
2018年 | 52篇 |
2017年 | 39篇 |
2016年 | 86篇 |
2015年 | 75篇 |
2014年 | 133篇 |
2013年 | 181篇 |
2012年 | 169篇 |
2011年 | 149篇 |
2010年 | 144篇 |
2009年 | 160篇 |
2008年 | 165篇 |
2007年 | 149篇 |
2006年 | 164篇 |
2005年 | 128篇 |
2004年 | 115篇 |
2003年 | 102篇 |
2002年 | 62篇 |
2001年 | 52篇 |
2000年 | 64篇 |
1999年 | 48篇 |
1998年 | 66篇 |
1997年 | 52篇 |
1996年 | 37篇 |
1995年 | 33篇 |
1994年 | 47篇 |
1993年 | 41篇 |
1992年 | 36篇 |
1991年 | 38篇 |
1990年 | 42篇 |
1989年 | 43篇 |
1988年 | 36篇 |
1987年 | 49篇 |
1986年 | 31篇 |
1985年 | 53篇 |
1984年 | 54篇 |
1983年 | 39篇 |
1982年 | 33篇 |
1981年 | 43篇 |
1980年 | 50篇 |
1979年 | 39篇 |
1978年 | 39篇 |
1977年 | 50篇 |
1976年 | 48篇 |
1975年 | 33篇 |
1974年 | 39篇 |
1973年 | 31篇 |
排序方式: 共有3978条查询结果,搜索用时 15 毫秒
71.
Alrun A. Günther Michael Sawatzki Petr Formánek Daniel Kasemann Karl Leo 《Advanced functional materials》2016,26(5):768-775
Doping is a powerful tool to overcome contact limitations in short‐channel organic field‐effect transistors (OFETs) and has been successfully used in the past to improve the charge carrier injection in OFETs. The present study applies this familiar concept to the architecture of vertical organic field‐effect transistors (VOFETs), which are often severely limited by injection due to their very short channel lengths. The present study shows that the performance of p‐type VOFETs with pentacene as an active material can be significantly enhanced by the addition of the common p‐dopant C60F36 as a thin injection layer underneath the VOFET source electrode, resulting in an increase of On‐state current and On/Off ratio by one order of magnitude. The present study further investigates mixed injection layers of pentacene and the p‐dopant and finds that the improvement is less pronounced than for the pure dopant layers and depends on the concentration of dopant molecules in the injection layer. Through application of the transfer length method to equivalent OFET geometries, the present study is finally able to link the observed improvement to a decrease in transfer length and can thus conclude that this length is a crucial parameter onto which further improvement efforts have to be concentrated to realize true short‐channel VOFETs. 相似文献
72.
Thorsteinn Astradsson Felix Sellberg Ylva Tiblom Ehrsson Karl Sandstrm Gran Laurell 《International journal of molecular sciences》2022,23(11)
In this real-world study, the aims were to prospectively evaluate the expression of inflammatory proteins in serum collected from head and neck cancer patients before and after treatment, and to assess whether there were differences in expression associated with treatment modalities. The mixed study cohort consisted of 180 patients with head and neck cancer. The most common tumor sites were the oropharynx (n = 81), the oral cavity (n = 53), and the larynx (n = 22). Blood tests for proteomics analysis were carried out before treatment, 7 weeks after the start of treatment, and 3 and 12 months after the termination of treatment. Sera were analyzed for 83 proteins using an immuno-oncology biomarker panel (Olink, Uppsala, Sweden). Patients were divided into four treatment groups: surgery alone (Surg group, n = 24), radiotherapy with or without surgery (RT group, n = 94), radiotherapy with concomitant cisplatin (CRT group, n = 47), and radiotherapy with concomitant targeted therapy (RT Cetux group, n = 15). For the overall cohort, the expression levels of 15 of the 83 proteins changed significantly between the pretreatment sample and the sample taken 7 weeks after the start of treatment. At 7 weeks after the start of treatment, 13 proteins showed lower expression in the CRT group compared to the RT group. The majority of the inflammatory proteins had returned to their pretreatment levels after 12 months. It was clearly demonstrated that cisplatin-based chemoradiation has immunological effects in patients with head and neck cancer. This analysis draws attention to several inflammatory proteins that are of interest for further studies. 相似文献
73.
74.
75.
76.
Chloride and Indium‐Chloride‐Complex Inorganic Ligands for Efficient Stabilization of Nanocrystals in Solution and Doping of Nanocrystal Solids 下载免费PDF全文
Vladimir Sayevich Chris Guhrenz Maria Sin Volodymyr M. Dzhagan Alexander Weiz Daniel Kasemann Eike Brunner Michael Ruck Dietrich R. T. Zahn Karl Leo Nikolai Gaponik Alexander Eychmüller 《Advanced functional materials》2016,26(13):2163-2175
Here, the surface functionalization of CdSe and CdSe/CdS core/shell nanocrystals (NCs) with compact chloride and indium‐chloride‐complex ligands is reported. The ligands provide not only short interparticle distances but additionally control doping and passivation of surface trap states, leading to enhanced electronic coupling in NC‐based arrays. The solids based on these NCs show an excellent electronic transport behavior after heat treatment at the relatively low temperature of 190 °C. Indeed, the indium‐chlorido‐capped 4.5 nm CdSe NC based thin‐film field‐effect transistor reaches a saturation mobility of μ = 4.1 cm2 (V s)?1 accompanied by a low hysteresis, while retaining the typical features of strongly quantum confined semiconductor NCs. The capping with chloride ions preserves the high photoluminescence quantum yield ( ≈ 66%) of CdSe/CdS core/shell NCs even when the CdS shell is relatively thin (six monolayers). The simplicity of the chemical incorporation of chlorine and indium species via solution ligand exchange, the efficient electronic passivation of the NC surface, as well as their high stability as dispersions make these materials especially attractive for wide‐area solution‐processable fabrication of NC‐based devices. 相似文献
77.
For honeybee colonies, it is crucial to collect nectar in an efficient way. Empiric experiments showed that the process of
decision making, which allows the colony to select the optimal nectar source, is based on individual decisions. These decisions
are made by returning nectar foragers, which alter their dancing behaviours based on the nectar source’s quality and based
on the experienced search time for a receiver bee. Nectar receivers, which represent a shared limited resource for foragers,
can modulate the foraging decisions performed by the colony. We investigated the interplay between foragers and receivers
by using a multi-agent simulation. Therefore, we implemented agents which are capable of a limited set of behaviours and which
spend energy according to their behaviour. In simulation experiments, we tested colonies with various receiver-to-forager
ratios and measured colony-level results like the emerging foraging patterns and the colony’s net honey gain. We show that
the number of receivers prominently regulates the foraging workforce. All tested environmental fluctuations are predicted
to cause energetic costs for the colony. Task-partitioning additionally influences the colony’s decision-making concerning
the question whether or not the colony sticks to a nectar source after environmental fluctuations. 相似文献
78.
79.
Karl Fraser Scott J. Harrison Geoff A. Lane Don E. Otter Yacine Hemar Siew-Young Quek Susanne Rasmussen 《Food chemistry》2012
Tea is the second most consumed beverage in the world and its consumption has been associated with numerous potential health benefits. Factors such as fermentation methods, geographical origin and season can affect the primary and secondary metabolite composition of tea. In this study, a hydrophilic interaction liquid chromatography (HILIC) method coupled to high resolution mass spectrometry in both positive and negative ionisation modes was developed and optimised. The method when combined with principal component analysis to analyse three different types of tea, successfully distinguished samples into different categories, and provided evidence of the metabolites which differed between them. The accurate mass and high resolution attributes of the mass spectrometric data were utilised and relative quantification data were extracted post-data acquisition on 18 amino acids, showing significant differences in amino acid concentrations between tea types and countries. This study highlights the potential of HILIC chromatography combined with non-targeted mass spectrometric methods to provide a comprehensive understanding of polar metabolites in plant extracts. 相似文献
80.
An NMR-based metabolomic assessment of cultured cobia health in response to dietary manipulation 总被引:1,自引:0,他引:1
Commercial aquaculture feeds rely heavily on fishmeal and fish oil, which can be expensive and ecologically unsustainable. To evaluate the efficacy of reduced fishmeal diets for outgrowth, a dietary study was conducted on the finfish cobia, Rachycentron canadum. NMR-based metabolomic techniques were used to assess the effect of decreasing dietary fishmeal on the health of the cobia. Filtered serum 1H NMR spectra analysed by principal components analysis (PCA) showed cobia fed reduced fishmeal diets were metabolically different than cobia on control diets. In particular, tyrosine and betaine increased in cobia fed reduced fishmeal diets while glucose decreased, suggesting that these cobia were not receiving the necessary nutritional components required for energy and growth. The formulated control diet contributed to enriched growth and significantly elevated lactate levels suggesting enhanced gut microflora metabolism in response to dietary components. The results show that NMR-based metabolomic analysis is a useful tool in aquaculture studies. 相似文献