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   295篇
  免费   16篇
电工技术   5篇
化学工业   117篇
金属工艺   4篇
机械仪表   8篇
建筑科学   7篇
能源动力   6篇
轻工业   68篇
水利工程   1篇
石油天然气   2篇
无线电   11篇
一般工业技术   46篇
冶金工业   16篇
原子能技术   6篇
自动化技术   14篇
  2024年   2篇
  2023年   1篇
  2022年   9篇
  2021年   10篇
  2020年   2篇
  2019年   5篇
  2018年   9篇
  2017年   7篇
  2016年   10篇
  2015年   8篇
  2014年   10篇
  2013年   13篇
  2012年   17篇
  2011年   21篇
  2010年   21篇
  2009年   11篇
  2008年   11篇
  2007年   19篇
  2006年   18篇
  2005年   8篇
  2004年   9篇
  2003年   6篇
  2002年   10篇
  2001年   4篇
  2000年   5篇
  1999年   4篇
  1998年   5篇
  1997年   5篇
  1996年   9篇
  1995年   4篇
  1994年   7篇
  1993年   3篇
  1992年   1篇
  1991年   5篇
  1990年   7篇
  1989年   3篇
  1988年   1篇
  1986年   2篇
  1985年   2篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1970年   1篇
  1969年   1篇
排序方式: 共有311条查询结果,搜索用时 15 毫秒
71.
Building equipment, energy-saving systems, and claims of inappropriate indoor thermal environments were analyzed in relation to the floor area using responses to a questionnaire survey of service managers of 157 buildings built in Osaka, Kyoto and Hyogo prefectures in Kinki area of Japan. Results show the following: (1) In smaller buildings (〈 5,000 m2), setting temperatures are higher in summer and lower in winter, effects of "uncomfortable radiation from windows" are greater, energy-saving systems decrease indoor thermal comfort, but claims of "hot" and "cold" are fewer; (2) Claims of "hot" and "cold" are unrelated to the setting temperature and whether the air-conditioning control system is central or local; (3) The adoption rates of mitigation of dress codes ("COOL-BIZ" and "WARM-BIZ") are higher than those of temperature mitigation of air conditioning.  相似文献   
72.
73.
The purpose of this study was to investigate the quantification performance of transmission Raman spectroscopy with univariate analysis. Model dosage forms containing acetaminophen and an excipient, lactose monohydrate, were prepared. The Raman spectra of the tablets were obtained using the modes of transmission, backscattering micro-spectroscopy, and wide area illumination. Calibration curves for quantification of acetaminophen in the tablets were created using peak heights of the Raman spectra. Of the three modes of measurement, the quantitative results by transmission had the highest correlation with those by conventional UV–vis methods. In the validation of quantification by the transmission mode with univariate analysis, a certain degree of daily variation was confirmed. Additionally, quantitative results using peak heights were compared with those of partial least squares (PLSs) multivariate analysis. The root mean square error of prediction (RMSEP) suggested that quantification using PLS provided better precision than the peak height method as expected. However, content uniformity test using large sample sizes by the Raman spectra is not required to be very highly predictive because they usually employ non-parametric criteria and include wide specification ranges. Therefore, univariate analysis using transmission Raman spectroscopy was a suitable quantitative method for conducting content uniformity tests of large sample sizes.  相似文献   
74.
75.
A method for obtaining mouse hepatocytes by infusing collagenase solution into the left ventricle was established. This technique was shown to be equivalent to the intra-portal infusion method and more practical, especially in postnatal mice with a small body size.  相似文献   
76.
To prepare organic solar cells with practical level of energy-conversion efficiency, the following strategies were adopted. By using HD as the photosensitizer, which is heterodimer consisting of a weak electron-donating 5, 10, 15, 20-tetra(2, 5-dimethoxyphenyl)porphyrinatozinc and a weak electron-accepting 5, 10, 15-triphenyl-20-(3-pyridyl)porphyrin, intramolecular photoinduced electron transfer is promoted resulting in effective charge separation. To create an energetically well-arranged system, the HD was placed between an electron-acceptor layer of PV (perylene-3, 4, 9, 10-tetracarboxyl-bis-benzimidazole) and strong electron-donor layer of MC (3-carboxymethyl-5-[(3-ethyl-2(3H)-benzothiazolylidine)ethylidene]-2-thioxo-4-thiazolidinone), where photoinduced intermolecular electron transfer from HD to PV and rapid injection of electrons from MC to HD suppress back electron transfer in the charge-separated HD. As a result of this, the three-layer solar cell Al/PV/HD/MC/Au showed fairly good photovoltaic properties, short-circuit photocurrent quantum yield of 49.2%, open-circuit photovoltage of 0.39 V, fill factor of 0.51, and energy conversion yield of 3.51% when irradiated with 445 nm monochromatic light of 12 μW cm−2 intensity transmitted through the Al/PV interface. Since the photocurrent hardly decreased with age, the photocurrent observed here is really from energy conversion and not from photocorrosion of Al electrode being occasionally responsible for the photocurrent.  相似文献   
77.
Members of the genus Nepenthes are carnivorous plants that use the pitfall method of insect capture as a supplementary nutritional source. We extracted metagenomic DNA from the microbial community found in the pitcher fluid of Nepenthes and constructed a plasmid-based metagenomic library. An activity-based screening method enabled the isolation of two lipase genes, lip1 and lip2. Both Lip1 and Lip2 belong to a novel family or subfamily of lipases and show lipase activities in acidic conditions, such as those found in pitcher fluid. This study was conducted under the assumption that the secreted Lip1 and Lip2 were capable of enzymatic activity in the acidic pitcher fluid.  相似文献   
78.
Summary Hybrid liposomes were prepared from the mixture of dipalmitoyl phosphatidylcholine (DPPC) and di-2,4-octadecadiene phosphatidylcholine (DODPC), and their phase separation behaviours was analyzed. In hybrid liposome systems, two transition temperatures (18 and 41°C for DODPC and DPPC, respectively) were clearly observed by means of DSC and fluorescence techniques. These two transition temperatures were also found after polymerization of DODPC molecules in hybrid liposomes by the UV irradiation. These strongly suggest that DPPC and DODPC molecules do not dissolve well but form clusters in the membrane. This phase separation was directly confirmed by freeze-fracture TEM technique.  相似文献   
79.
The O+ desorption from reduced, oxygenated, and ion-bombarded TiO2(1 1 0) surfaces has been investigated during He+ irradiation. The O+ desorption is initiated by creation of an antibonding O 2s core hole state via quasi-resonant charge exchange with the He+ 1s state, followed by the intra-atomic Auger decay of the O 2s hole. Upon oxygenation of the reduced TiO2(1 1 0) surface, the O+ yield increases by one order of magnitude. The O2 molecule is dissociated at the vacancy site of bridging oxygen and the oxygen atoms either fill a vacancy site or chemisorb at a fivefold-coordinated Ti4+ site as an adatom. The latter is detected with much higher efficiency than the former. The O+ yield is increased during He+ bombardment of the reduced TiO2(1 1 0) surface due to formation of lower coordinated oxygen atoms. The oxygen species thus formed by ion bombardment or oxygenation are unstable on the surface and tend to diffuse into bulk vacancy sites or higher coordination surface sites even at room temperature.  相似文献   
80.
Although mouse Wnt-10b has been shown to play various roles in a wide range of biological actions, the effects on epithelial stem/progenitor cells in the skin have not been reported. In the present study, we investigated the effects of Wnt-10b on proliferation and differentiation of murine skin-derived CD34 and CD49f double-positive (CD34+CD49f+) cells, a supposed fraction as enriched epithelial stem/progenitor cells. The cells were prepared from dorsal skin samples obtained from young adult mice as α6 integrin (CD49f) and CD34 double-positive cells by fluorescent activated cell sorting (FACS), and they were cultured with or without Wnt-10b to investigate its effects on proliferation and differentiation. Involvement of canonical Wnt signaling pathway was confirmed by TOPFLASH assay, and differentiation of the CD34+CD49f+ cells was assessed by RT-PCR analysis and immunocytochemical examinations. The skin-derived CD34+CD49f+ cells were immunopositive for Lhx2 and expressed mRNA of classical markers for bulge stem cells, including Lhx2, keratin15, Sox9, S100a6, and NFATc1. Their proliferation was suppressed by Wnt-10b, and the markers for differentiated epithelial cells became to be expressed in the culture with Wnt-10b. These results suggest that Wnt-10b promotes differentiation of epithelial stem/progenitor cells in the skin.  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