首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   198篇
  免费   15篇
电工技术   1篇
综合类   1篇
化学工业   44篇
机械仪表   4篇
建筑科学   5篇
能源动力   7篇
轻工业   14篇
石油天然气   2篇
无线电   40篇
一般工业技术   52篇
冶金工业   15篇
自动化技术   28篇
  2023年   5篇
  2022年   3篇
  2021年   7篇
  2020年   6篇
  2019年   11篇
  2018年   5篇
  2017年   4篇
  2016年   7篇
  2015年   6篇
  2014年   12篇
  2013年   16篇
  2012年   11篇
  2011年   8篇
  2010年   11篇
  2009年   7篇
  2008年   6篇
  2007年   9篇
  2006年   6篇
  2005年   7篇
  2004年   8篇
  2003年   5篇
  2002年   6篇
  2001年   5篇
  2000年   3篇
  1999年   1篇
  1998年   4篇
  1996年   1篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1990年   1篇
  1987年   2篇
  1984年   2篇
  1983年   1篇
  1982年   3篇
  1981年   2篇
  1980年   3篇
  1979年   1篇
  1977年   1篇
  1976年   3篇
  1975年   3篇
  1974年   1篇
  1972年   2篇
  1960年   1篇
排序方式: 共有213条查询结果,搜索用时 218 毫秒
31.
The surfaces of NaY zeolite particles were modified by the alkylsilylation of n-octadecyltrichlorosilane (OTS). Two kinds of modified NaY zeolites were prepared; one with its external surface partially and the other fully covered with alkylsilyl groups. Since the size of OTS is bigger than the pore diameter of NaY, it is attached on the external surface, leaving the internal pore accessible to adsorbate molecules. As a result of alkylsilylation, the adsorption properties of these sorbents were improved. The adsorption properties of these materials were tested by their reaction in a mixture of paraquat and blue dye. The results demonstrate that the alkysilylated NaY materials are capable of simultaneous adsorption of paraquat and blue dye. Paraquat was selectively adsorbed into the internal pore of the zeolite whereas the dye on the externally attached alkylsilyl groups of the sorbent; displaying the unique bimodal amphiphilic character of the alkylsilylated NaY zeolites.  相似文献   
32.
SYNAPT~(TM) G2 HDMS质谱分析系统是沃特世公司第二代基于高效离子淌度(ion mobility spectrometry,IMS,也称离子迁移)技术的高性能四极杆-飞行时间质谱仪。通过两种技术的结合与升级,SYNAPT G2 HDMS不仅能按离子的质荷比分离检测,还可根据离子的大小、形状等将其分离。因此,此质谱系统不但可以提高传统质谱数据的准确性,更可以提供样品形态信息,从而得到样品活性、结构状态等信息。其在蛋白组学、代谢组学、糖及脂类分析、医学标志物发掘、药物开发与质控、食品安全检测、环境安全检测等方面有着广泛的应用空间,并已经表现出良好的性能优势,成为各领域工作者的有力的分析工具。本文简要介绍该系统的性能特点及应用。  相似文献   
33.
34.
Androgen disrupting chemicals (ADCs) are endocrine disrupting chemicals (EDCs) that mimic or antagonize the effect of physiological androgens. Microarray-based detection of altered gene expression can be used as a biomarker of EDC exposure. Therefore, the purpose of this study was to identify and compare gene expression profiles of the androgen 11-ketotestosterone (11-KT), the antiandrogen flutamide (FLU), and the antiandrogenic fungicide vinclozolin (VIN), on Qurt medaka (Oryzias latipes). Biologically effective concentrations for 11-KT (100 microg/L), VIN (100 microg/L), and FLU (1000 microg/L) determined in range-finding studies were used for exposures. The oligonucleotide microarray included 9379 probes for EDC-affected genes, medaka cDNAs, sequences from the medaka genome project, and the UniGene database. We found that treatment with FLU, VIN, and 11-KT caused significant (false discovery rate = 0.01) differential expression of at least 87, 82, and 578 genes, respectively. Two sets of responsive genes are associated to vertebrate sex differentiation and growth, and 50 genes were useful in discriminating between ADC classes. The discriminating capacity was confirmed by a remarkable similarity of the antiandrogenic expression profiles of VIN and FLU, which were distinct from the androgenic profile of 11-KT. Gene expression profiles characterized in this study allow for reliable screening of ADC activity.  相似文献   
35.
Introduction: Resorbable synthetic scaffolds are promising for different indications, especially in the context of bone regeneration. However, they require additional biological components to enhance their osteogenic potential. In addition to different cell types, autologous blood-derived matrices offer many advantages to enhance the regenerative capacity of biomaterials. The present study aimed to analyze whether biologization of a PCL-mesh coated using differently centrifuged Platelet rich fibrin (PRF) matrices will have a positive influence on primary human osteoblasts activity in vitro. A polymeric resorbable scaffold (Osteomesh, OsteoporeTM (OP), Singapore) was combined with differently centrifuged PRF matrices to evaluate the additional influence of this biologization concept on bone regeneration in vitro. Peripheral blood of three healthy donors was used to gain PRF matrices centrifuged either at High (710× g, 8 min) or Low (44× g, 8 min) relative centrifugal force (RCF) according to the low speed centrifugation concept (LSCC). OP-PRF constructs were cultured with pOBs. POBs cultured on the uncoated OP served as a control. After three and seven days of cultivation, cell culture supernatants were collected to analyze the pOBs activity by determining the concentrations of VEGF, TGF-β1, PDGF, OPG, IL-8, and ALP- activity. Immunofluorescence staining was used to evaluate the Osteopontin expression of pOBs. After three days, the group of OP+PRFLow+pOBs showed significantly higher expression of IL-8, TGF-ß1, PDGF, and VEGF compared to the group of OP+PRFHigh+pOBs and OP+pOBs. Similar results were observed on day 7. Moreover, OP+PRFLow+pOBs exhibited significantly higher activity of ALP compared to OP+PRFHigh+pOBs and OP+pOBs. Immunofluorescence staining showed a higher number of pOBs adherent to OP+PRFLow+pOBs compared to the groups OP+PRFHigh+pOBs and OP+pOBs. To the best of our knowledge, this study is the first to investigate the osteoblasts activity when cultured on a PRF-coated PCL-mesh in vitro. The presented results suggest that PRFLow centrifuged according to LSCC exhibits autologous blood cells and growth factors, seem to have a significant effect on osteogenesis. Thereby, the combination of OP with PRFLow showed promising results to support bone regeneration. Further in vivo studies are required to verify the results and carry out potential results for clinical translation.  相似文献   
36.
Heavy water or deuterium oxide (D2O) comprises deuterium, a hydrogen isotope twice the mass of hydrogen. Contrary to the disadvantages of deuterated perovskites, such as shorter recombination lifetimes and lower/invariant efficiencies, the serendipitous effect of D2O as a beneficial solvent additive for enhancing the power conversion efficiency (PCE) of triple-A cation (cesium (Cs)/methylammonium (MA)/formaminidium (FA)) perovskite solar cells from ≈19.2% (reference) to 20.8% (using 1 vol% D2O) with higher stability is reported. Ultrafast optical spectroscopy confirms passivation of trap states, increased carrier recombination lifetimes, and enhanced charge carrier diffusion lengths in the deuterated samples. Fourier transform infrared spectroscopy and solid-state NMR spectroscopy validate the N–H2 group as the preferential isotope exchange site. Furthermore, the NMR results reveal the induced alteration of the FA to MA ratio due to deuteration causes a widespread alteration to several dynamic processes that influence the photophysical properties. First-principles density functional theory calculations reveal a decrease in PbI6 phonon frequencies in the deuterated perovskite lattice. This stabilizes the PbI6 structures and weakens the electron–LO phonon (Fröhlich) coupling, yielding higher electron mobility. Importantly, these findings demonstrate that selective isotope exchange potentially opens new opportunities for tuning perovskite optoelectronic properties.  相似文献   
37.
Energy self‐sufficiency is an inspirational design feature of biological systems that fulfills sensory functions. Plants such as the “touch‐me‐not” and “Venus flytrap” not only sustain life by photosynthesis, but also execute specialized sensory responses to touch. Photosynthesis enables these organisms to sustainably harvest and expend energy, powering their sensory abilities. Photosynthesis therefore provides a promising model for self‐powered sensory devices like electronic skins (e‐skins). While the natural sensory abilities of human skin have been emulated in man‐made materials for advanced prosthetics and soft‐robotics, no previous e‐skin has incorporated phototransduction and photosensory functions that could extend the sensory abilities of human skin. A proof‐of‐concept bioelectronic device integrated with natural photosynthetic pigment‐proteins is presented that shows the ability to sense not only touch stimuli (down to 3000 Pa), but also low‐intensity ultraviolet radiation (down to 0.01 mW cm‐2) and generate an electrical power of ≈260 nW cm‐2. The scalability of this device is demonstrated through the fabrication of flexible, multipixel, bioelectronic sensors capable of touch registration and tracking. The polysensory abilities, energy self‐sufficiency, and additional nanopower generation exhibited by this bioelectronic system make it particularly promising for applications like smart e‐skins and wearable sensors, where the photogenerated power can enable remote data transmission.  相似文献   
38.
Unlike traditional water splitting in an aqueous medium, direct decomposition of atmospheric water is a promising way to simultaneously dehumidify the living space and generate power. Here, a tailored superhygroscopic hydrogel, a catalyst, and a solar cell are integrated into a humidity digester that can break down ambient moisture into hydrogen and oxygen, creating an efficient electrochemical cell. The function of the hydrogel is to harvest moisture from ambient humidity and transfer the collected water to the catalyst. Barium titanate and vertical 2D MoS2 nanosheets are integrated as the catalyst: the negatively polarized cathode can enhance the electron transport and attract H+ to the MoS2 surface for water reduction, while water oxidation takes place at the positively polarized anode. By employing this mechanism, it is possible to maintain the relative humidity in a medium-sized room at <60% without any additional energy input, and a stable current of 12.5 mA cm−2 is generated by the humidity digester when exposed to ambient light.  相似文献   
39.
Combining high-throughput experiments with machine learning accelerates materials and process optimization toward user-specified target properties. In this study, a rapid machine learning-driven automated flow mixing setup with a high-throughput drop-casting system is introduced for thin film preparation, followed by fast characterization of proxy optical and target electrical properties that completes one cycle of learning with 160 unique samples in a single day, a > 10 ×  improvement relative to quantified, manual-controlled baseline. Regio-regular poly-3-hexylthiophene is combined with various types of carbon nanotubes, to identify the optimum composition and synthesis conditions to realize electrical conductivities as high as state-of-the-art 1000 S cm−1. The results are subsequently verified and explained using offline high-fidelity experiments. Graph-based model selection strategies with classical regression that optimize among multi-fidelity noisy input-output measurements are introduced. These strategies present a robust machine-learning driven high-throughput experimental scheme that can be effectively applied to understand, optimize, and design new materials and composites.  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号