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   299篇
  免费   19篇
电工技术   2篇
化学工业   67篇
金属工艺   4篇
机械仪表   8篇
建筑科学   14篇
能源动力   7篇
轻工业   41篇
无线电   17篇
一般工业技术   68篇
冶金工业   64篇
原子能技术   1篇
自动化技术   25篇
  2024年   1篇
  2023年   8篇
  2022年   8篇
  2021年   23篇
  2020年   13篇
  2019年   7篇
  2018年   6篇
  2017年   11篇
  2016年   8篇
  2015年   14篇
  2014年   16篇
  2013年   13篇
  2012年   16篇
  2011年   25篇
  2010年   12篇
  2009年   9篇
  2008年   6篇
  2007年   8篇
  2006年   4篇
  2005年   10篇
  2004年   5篇
  2003年   1篇
  2002年   1篇
  2001年   4篇
  2000年   4篇
  1999年   5篇
  1998年   17篇
  1997年   11篇
  1996年   6篇
  1995年   1篇
  1994年   5篇
  1992年   6篇
  1991年   4篇
  1990年   4篇
  1989年   2篇
  1987年   3篇
  1986年   3篇
  1985年   5篇
  1984年   3篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1967年   1篇
  1959年   1篇
排序方式: 共有318条查询结果,搜索用时 15 毫秒
81.
In close relationships, the association between negative beliefs about a partner and loving was found to be moderated by how that negative knowledge was organized. In general, evaluatively integrative organization (i.e., categorizing positive and negative beliefs together) was associated with more positive thoughts, feelings, and behaviors toward the partner when the negative content of beliefs was high and relationships were relatively long. Additional evidence suggests that compartmentalization (i.e., organizing positive and negative beliefs in separate categories) may be an effective strategy for handling negative beliefs about a partner in a new relationship. Findings for behavioral closeness raise the possibility that the nature of shared activities, as well as an individual's cognitive processes, may influence how knowledge about a relationship partner is organized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
82.
Establishing biological synthesis of nanoparticles is increasing nowadays in the field of nanotechnology. The search for an optimal source with durability, stability, capacity to withstand higher environmental conditions with excellent characteristics is yet to meet. Consequently, there is need to create an eco‐friendly strategy for metal nanoparticle synthesis. One approach investigated in this review is the use of biosurfactants to enhance the synthesis biologically. In comparison with the other technologies, biosurfactants are less toxic and exhibit higher properties. This method is different from the conventional practice like physical and chemical methods. Several research studies represented that the biosurfactant influences the production of nanoparticles about 2–50 nm. In this manner, the research towards the biosurfactant has raised. This review also addressed the feasibility of biosurfactant and their benefits in the synthesis of metallic nanoparticles. The findings from this review can recommend a conceivable use of biosurfactant as a source for metal nanoparticle synthesis.Inspec keywords: nanoparticles, microorganisms, nanotechnology, biotechnology, nanofabrication, durability, surfactants, reviewsOther keywords: biological synthesis, bacterial biosurfactants, environmental conditions, metallic nanoparticles synthesis, nanotechnology, durability, review, stability, size 2.0 nm to 50.0 nm  相似文献   
83.
The exploration of the synthetic space of halide perovskites hinges on an enormous number of parameters requiring time‐consuming experimentation to decouple and optimize. Here, the formation of the prototype material CH3NH3PbI3 (MAPbI3) is investigated at different time and length scales using multimodal in situ measurements to monitor the evolution of crystalline phases, morphology, and photoluminescence as a function of the lead precursors. Kinetically fast formation of crystalline precursor phases already during the spin‐coat deposition is observed using lead iodide (PbI2) or lead chloride (PbCl2) routes. These precursor phases most likely template final MAPbI3 film morphology. In particular, the emergence of the “needle‐like” structure is shown to appear before film annealing. In situ photoluminescence measurements suggest nanoscale nucleation followed by rapid nuclei densification and growth. Using this multimodal in situ approach, different formation pathways can be identified either via precursor phases in the PbI2 and PbCl2 routes or direct perovskite formation from molecular building blocks as observed in the lead acetate (PbAc2) route. Correlation of in situ results with photovoltaic device performance demonstrates the power of in situ multimodal techniques, paves the way to a fast screening of synthetic parameters, and ultimately leads to controlled synthetic procedures that yield high‐efficiency devices.  相似文献   
84.
85.
By means of plasma polymerization, positively charged, nanometre-thin coatings can be applied to implant surfaces. The aim of the present study was to quantify the adhesion of human bone cells in vitro and to evaluate the bone ongrowth in vivo, on titanium surfaces modified by plasma polymer coatings. Different implant surface configurations were examined: titanium alloy (Ti6Al4V) coated with plasma-polymerized allylamine (PPAAm) and plasma-polymerized ethylenediamine (PPEDA) versus uncoated. Shear stress on human osteoblast-like MG-63 cells was investigated in vitro using a spinning disc device. Furthermore, bone-to-implant contact (BIC) was evaluated in vivo. Custom-made conical titanium implants were inserted at the medial tibia of female Sprague-Dawley rats. After a follow-up of six weeks, the BIC was determined by means of histomorphometry. The quantification of cell adhesion showed a significantly higher shear stress for MG-63 cells on PPAAm and PPEDA compared to uncoated Ti6Al4V. Uncoated titanium alloyed implants showed the lowest BIC (40.4%). Implants with PPAAm coating revealed a clear but not significant increase of the BIC (58.5%) and implants with PPEDA a significantly increased BIC (63.7%). In conclusion, plasma polymer coatings demonstrate enhanced cell adhesion and bone ongrowth compared to uncoated titanium surfaces.  相似文献   
86.
Tetrahedral DNA hybrids with tetrakis(p‐hydroxyphenyl)methane cores hybridize in a sequence‐specific fashion at much higher temperatures than isolated linear duplexes. Dinucleotide DNA arms suffice to induce the formation of a solid at room temperature; this demonstrates the strength of multivalent binding. The graphic shows a view of a modeled assembly.

  相似文献   

87.
In structural dynamics coupled systems with unbounded deformable members are characterized by radiation damping. Typically, the unbounded subsystem is described in the frequency domain; either numerically or analytically by means of dynamical stiffness matrices. Recent papers describe a matrix-valued rational interpolation of the dynamical stiffness and straightforward transformation into the time-domain. In addition, the asymptotic behaviour has been considered, too, by adding fractional derivatives. However, the matrices involved in this process are unsymmetric even if the original dynamical stiffnesses are symmetric. The approach presented in this paper maintains the symmetry a priori without any numerical operations by simply using a rational approximation with a matrix-valued numerator but a scalar-valued denominator and contains some further numerical advantages. The method is demonstrated by treating an infinite beam on an elastic foundation.  相似文献   
88.
Electronic Markets - Multi-sided platforms in healthcare often focus their business model on standardizing care for wide-spread, chronic diseases. However, there is a lack of knowledge surrounding...  相似文献   
89.
We present the development and characterization of a low-cost fiber-optic colorimetric gas sensor for ammonia combined with the electronic circuitry for measurement control and RFID communication. The gas sensor detects ammonia using a 300?μm polyolefin fiber coated with a gas-sensitive polymer film. The spectral and time-dependent sensitivity of various polymer films was tested in transmission measurements at λ?=?590?nm. A prototype of the gas sensor was tested under realistic measurement conditions, i.e. battery-driven and in a completely autonomous mode. The sensor system showed good sensitivity to the ammonia concentrations and response times in the order of minutes. The achievable power consumption was below 100?μW. Bromophenol blue-based films showed a strong reaction to ammonia, with saturation concentrations around 1,000?ppm and response times of about 15?s to 100?ppm. The colorimetric reaction was simulated using a simple kinetic model which was in good agreement with the experimental results.  相似文献   
90.
The presented work focuses on the investigations of a metallo-porphyrin and its gasochromic behavior to different gases. Gasochromic materials change their color while they are exposed to a certain gas. So they offer the possibility to develop highly selective chemical gas sensors and gas sensing systems. The focus of this work is the characterization of the metallo-porphyrin 5, 10, 15, 20-tetraphenylporphyrin-zinc (ZnTPP). Nonetheless, there is a wide range of other possible metallo-porphyrins. When embedded into a polymeric matrix (PVC) a color change to the toxic gas NO2 can be detected. To develop a stand-alone gas sensor, the porphyrin/PVC matrix is deposited onto a planar optical waveguide. The color change of the porphyrin dye can be detected in the evanescent field of the optical waveguide. Therefore, the light of a high power LED is coupled into the waveguide. The color change of the porphyrin is detectable with photodiodes as a variation of the out-coupled light intensity. The sensor shows no unwished sensitivities to CO2 and CO and only low to NH3. NO2 is detectable with a resolution of 1?ppm.  相似文献   
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