全文获取类型
收费全文 | 1307篇 |
免费 | 144篇 |
国内免费 | 71篇 |
专业分类
电工技术 | 16篇 |
综合类 | 87篇 |
化学工业 | 414篇 |
金属工艺 | 28篇 |
机械仪表 | 73篇 |
建筑科学 | 8篇 |
矿业工程 | 18篇 |
能源动力 | 29篇 |
轻工业 | 110篇 |
水利工程 | 3篇 |
石油天然气 | 73篇 |
武器工业 | 13篇 |
无线电 | 219篇 |
一般工业技术 | 317篇 |
冶金工业 | 32篇 |
原子能技术 | 20篇 |
自动化技术 | 62篇 |
出版年
2024年 | 4篇 |
2023年 | 22篇 |
2022年 | 50篇 |
2021年 | 74篇 |
2020年 | 39篇 |
2019年 | 50篇 |
2018年 | 35篇 |
2017年 | 56篇 |
2016年 | 75篇 |
2015年 | 69篇 |
2014年 | 71篇 |
2013年 | 105篇 |
2012年 | 68篇 |
2011年 | 90篇 |
2010年 | 52篇 |
2009年 | 74篇 |
2008年 | 60篇 |
2007年 | 91篇 |
2006年 | 65篇 |
2005年 | 70篇 |
2004年 | 39篇 |
2003年 | 39篇 |
2002年 | 47篇 |
2001年 | 42篇 |
2000年 | 18篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1973年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1522条查询结果,搜索用时 31 毫秒
51.
Theoretical investigation of voltage effect on magnetoresistance in an organic small molecule device
We theoretically study the voltage effect on organic magnetoresistance (OMAR) in a weak disordered small molecule device on the basis of the quantum dynamics. It is found that with the increase of the voltage, the OMAR effect is reduced. The results show a good agreement with the experimental data. In addition, the carrier density effect on OMAR has also been discussed. 相似文献
52.
Two unsymmetrical squaraines (USQs) with different donor (D) subunits as photovoltaic materials, namely USQ-11 and USQ-12, were designed and synthesized to investigate the effect of different D subunits on the optoelectronic properties of USQs for the first time. The two USQs compounds were characterized for optical, electrochemical, quantum chemical and optoelectronic properties. By changing the two different D subunits attached to the squaric acid core from 2,3,3-trimethylindolenine to 2-methylbenzothiazole, the HOMO energy levels could be tuned with a stepping of 0.07 eV, and quite different solid state aggregations (H- or J-aggregation) were observed in the thin film by UV-Vis absorption spectra, which were attributed to their distinct steric effects and dipole moments. Solution-processed bulk-heterojunction small molecule organic solar cells fabricated with the USQ-11/PC71BM (1:5, wt%) exhibited extremely higher PCE (4.27%) than that of the USQ-12/PC71BM (2.78%). The much enhanced PCE should be attributed to the simultaneously improved Voc, Jsc and FF. 相似文献
53.
Inhibition of yeast‐to‐filamentous growth transitions in Candida albicans by a small molecule inducer of mammalian apoptosis 下载免费PDF全文
The opportunistic fungal pathogen of humans Candida albicans is able to grow in different morphological forms such as round or oval yeasts and filamentous hyphae and pseudohyphae. Morphogenesis, the ability to switch between the yeast and filamentous growth forms, is important for adapting to new microenvironments in the human host and for pathogenesis. The molecular pathways governing morphogenesis are complex and incompletely understood. Previously, we identified several small organic molecules that specifically inhibit the initiation of hyphal growth in C. albicans without affecting cell viability or budded growth. One molecule from that screen is known to induce apoptosis in mammalian cells. In this study, we have screened additional inducers of mammalian apoptosis and identified BH3I‐1, as well as several structural derivatives of BH3I‐1, that act as specific inhibitors of morphogenesis under a variety of environmental conditions. Chemical epistasis experiments suggest that BH3I‐1 acts downstream of the hypha‐specific gene regulators Rfg1, Nrg1 and Ume6. 相似文献
54.
《Organic Electronics》2014,15(7):1592-1597
A p-type small molecule bearing dicarboxylic acid functional group (–COOH) is synthesized and evaluated for field-effect transistor properties. We discover and report for the first time, that the –COOH groups assist in the passivation of surface traps on the dielectric layer and simultaneously facilitate the self-assembly of the molecules via inter-molecular hydrogen bonding resulting in crystalline active channels. A 9-fold decrease in the threshold voltage was observed for the transistors made using the –COOH functionalized molecule, QT-DA, compared to its ester analogue, QT-ES, providing an evidence of surface passivation. This resulted in an increase in the hole mobility of QT-DA by up to 2 orders of magnitude. It was shown that QT-DA adopts a vertical alignment with respect to the substrate due to preferential interaction between the –COOH groups and the SiO2 surfaces. 相似文献
55.
Jan Meiss Markus HummertAnnette Petrich Steffen PfuetznerKarl Leo Moritz Riede 《Solar Energy Materials & Solar Cells》2011,95(2):630-635
We present the material 2,3,10,11-tetrabutyl-1,4,9,12-tetraphenyl-diindeno[1,2,3-cd:1′,2′,3′-lm] perylene (Bu4-Ph4-DIP) as alternative green donor for bulk heterojunction small molecule organic solar cells (SMOSC). It is shown that Bu4-Ph4-DIP exhibits suitable absorption characteristics to be a potential material to fill the absorption gap between the commonly used standard absorbers ZnPc and C60.Devices with bulk heterojunctions of Bu4-Ph4-DIP:C60 display very high open circuit voltages of 0.99 V, high fill factors of up to 57%, and experiments yield promising efficiencies of η>2%. Such green-blue absorbing SMOSC are characterized by current voltage and external quantum efficiency measurements, and material properties are studied. It is shown that the devices are responsive to substrate heating, and that different donor-acceptor mixing ratios can increase device performance. Possible influences of mixing ratio and heating on device morphology and electrical properties are discussed. 相似文献
56.
水分侵入是造成复合绝缘子高温硫化硅橡胶伞裙、护套材料老化的主要因素之一。为了获得能够准确描述水分子在硅橡胶中扩散的扩散模型和扩散特性,使用固体核磁共振(nuclear magnetic resonance,NMR)技术,分析了水分子在硅橡胶中的存在状态;并通过称重法试验,获得了水分子在硅橡胶中扩散时硅橡胶的增重曲线。研究表明,水分子在硅橡胶中存在"自由态"和"结合态"两种不同的状态。固体核磁共振和称重法的试验结果都表明,水分子在硅橡胶中的扩散过程符合Langmuir扩散模型,而不符合经典的Fick扩散模型。同时研究了水分子扩散过程的影响因素,结果发现:自由态水分子的含量随温度的升高而增加,结合态水分子的含量随温度的升高而降低,且温度对扩散系数的影响符合经典的Arrhenius方程;硅橡胶中的氢氧化铝(ATH)填料含量的增加会导致结合态水分子含量的增加,但ATH含量对自由态水分子含量的影响不显著。 相似文献
57.
58.
为了定量研究温度、炉渣成分、钢液成分对转炉磷分配比和平衡磷含量的影响,基于共存理论建立转炉炼钢六元渣系的组元活度计算模型和磷分配比LP计算模型,将磷分配比模型计算结果与转炉炼钢实测磷分配比进行对比,发现两者吻合较好。定量计算结果表明,当炉渣碱度为3.8时,钢液温度从1 640升到1 680 ℃,平衡磷质量分数从0.011 5%增加至0.019 8%。同时定量计算了炉渣碱度及氧化铁含量变化对平衡磷含量的影响,但实际炉渣控制需要考虑炉渣黏度、铁损及炉衬侵蚀。转炉吹炼终点钢中元素含量数量级较小,计算表明终点成分变化对磷活度系数的影响不大,各元素对脱磷的影响主要体现在冶炼初期和过程。 相似文献
59.
60.