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   151篇
  免费   1篇
电工技术   1篇
综合类   2篇
化学工业   62篇
金属工艺   3篇
机械仪表   4篇
建筑科学   8篇
矿业工程   1篇
能源动力   1篇
轻工业   18篇
水利工程   1篇
石油天然气   1篇
无线电   11篇
一般工业技术   7篇
冶金工业   23篇
自动化技术   9篇
  2023年   1篇
  2022年   14篇
  2021年   10篇
  2020年   2篇
  2019年   4篇
  2018年   2篇
  2016年   3篇
  2015年   1篇
  2014年   4篇
  2013年   10篇
  2012年   5篇
  2011年   2篇
  2010年   8篇
  2009年   1篇
  2008年   9篇
  2007年   5篇
  2006年   6篇
  2005年   2篇
  2004年   5篇
  2003年   7篇
  2002年   6篇
  2001年   2篇
  2000年   4篇
  1999年   8篇
  1998年   3篇
  1997年   2篇
  1995年   1篇
  1994年   2篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1987年   4篇
  1986年   1篇
  1985年   3篇
  1983年   2篇
  1982年   1篇
  1980年   1篇
  1977年   4篇
  1976年   1篇
  1959年   1篇
排序方式: 共有152条查询结果,搜索用时 0 毫秒
21.
22.
Hydroxy fatty acids are important industrial materials. We isolated a microbial culture, Clavibacter sp. ALA2, which converts linoleic acid to many polyhydroxy fatty acids. Structures of the products were determined as: 12,13,17-trihydroxy-9(Z)-octadecenoic (THOA, main product), 12-[5-ethyl-2-tetrahydrofuranyl]-7,12-dihydroxy-9(Z)-dodecenoic (ETDDA), and 12-[5-ethyl-2-tetrahydrofuranyl]-12-hydroxy-9(Z)-dodecenoic (ETHDA) acid. The yield of THOA was 25% and the relative amount of the products were THOA/ETDDA/ETHDA =9:1.3:1. The structures of the hydroxy unsaturated fatty acids resemble those of plant self-defense substances.  相似文献   
23.
The self-assembled formation of a one-dimensional lanthanum salicylald imine coordination polymer was proved by the X-ray diffraction analysis of new l anthanum(Ⅲ) nitrate complex containing N,N’-bis(salicylidene)-1,5-pentanediami ne ligand(H2L) . It was obtained in situ in a one-step,metal-templated condensa tion of salicylaldehyde with 1,5-pentanediamine(cadaverine,biogenic polyamine) and characterized by microanalysis and spectroscopic(IR,ESI-MS,UV-Vis,and 1 H NMR) data. The [La(NO3) 3(μ-H2L) 2]∞ complex displayed 10-coordinate distorted bicapped dodecahedron geometry with unusual coordination pattern of undeprotonat ed salicylaldimines which acted as μ-bridging ditopic ligands using exclusivel y the oxygens as donor atoms with the nitrogen atoms not being involved in the c oordination environment.  相似文献   
24.
Conducted behavioral assessments of 38 toddlers during their 2nd yr of life during 10 small-group play sessions and during administration of developmental tests (the Bayley Scales of Infant Development). 34 of the Ss were also observed at age 3.5 yrs in a nursery school setting at follow-up. Results show that there was a significant increase in the consistency and range of reactions in the play groups over the year. There was a trend toward more lawful end-of-year association among responses elicited in the play sessions and the testing sessions. There was a marked end-of-year increase in the ability to predict later functioning in nursery school. It is concluded that although the phenomenon of the emergence of stable individual differences in functioning is real, it has yet to be explained. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
25.
This article is written on behalf of the Society for Industrial and Organizational Psychology (SIOP) to present its reactions to the "Principles for Education and Training at the Doctoral and Postdoctoral Level in Consulting Psychology/Organizational" (R. L. Lowman et al, Education and Training Committee, see record 2003-04049-003). An overview of the history and practice of industrial-organizational psychology is provided. The Consulting Principles are then compared with SIOP Education and Training Guidelines (SIOP Guidelines, 1985 and 1999), and recommendations are made for enhancements to the Consulting Principles. The primary recommendation is for the addition of a second tier of competencies focusing on the knowledge, skill, and abilities that underlie the types of work described in the Individual-, Group-, and Organizational-Level Competencies. As an alternative, the Consulting Principles could focus on consulting skills and refer to the appropriate APA divisions regarding specialty areas. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
26.
Heavy metals polluting the 100-year-old waste heap in Bolesław (Poland) are acting as a natural selection factor and may contribute to adaptations of organisms living in this area, including Trifolium repens and its root nodule microsymbionts—rhizobia. Exopolysaccharides (EPS), exuded extracellularly and associated with bacterial cell walls, possess variable structures depending on environmental conditions; they can bind metals and are involved in biofilm formation. In order to examine the effects of long-term exposure to metal pollution on EPS structure and biofilm formation of rhizobia, Rhizobium leguminosarum bv. trifolii strains originating from the waste heap area and a non-polluted reference site were investigated for the characteristics of the sugar fraction of their EPS using gas chromatography mass-spectrometry and also for biofilm formation and structural characteristics using confocal laser scanning microscopy under control conditions as well as when exposed to toxic concentrations of zinc, lead, and cadmium. Significant differences in EPS structure, biofilm thickness, and ratio of living/dead bacteria in the biofilm were found between strains originating from the waste heap and from the reference site, both without exposure to metals and under metal exposure. Received results indicate that studied rhizobia can be assumed as potentially useful in remediation processes.  相似文献   
27.
The aim of the presented work was to evaluate the effect of modification of titanium dioxide nanoparticles with noble metals and their oxides on selected mammalian cells. The in vitro cytotoxicity studies of titanium dioxide (TiO2) nanoparticles modified with Au, Ag, Pd, Ag2O, and PdO with reference to the unmodified TiO2 nanoparticles were presented. The evaluation of cytotoxic activity of the tested nanocomposite particles was carried out using three cell lines: Caco-2 colorectal epithelial adenocarcinoma cells, BJ normal human skin fibroblasts, and L929 mouse fibroblasts. The in vitro studies included determination of cell viability after 24 and 48 hours of exposure to the nanocomposite particles, using the MTT assay, as well as flow cytometry with Annexin V-FITC staining. Our results indicate that irrespectively of the kind of cell line and assay used, nanoparticles of unmodified titanium dioxide as well as those with addition of gold and palladium have a slight impact on cell viability at the investigated concentration range (10-200 μg/mL). Nanoparticles with addition of silver (Ag and Ag2O), were found to have significantly higher toxic effect, the level of which varied depending on the cell line and assay used.  相似文献   
28.
Within this paper, it is explored how two-dimensional Ti2C sheets addition affects silicon carbide matrix composites in terms of the microstructure and mechanical properties. In order to consolidate the powder mixtures, powder metallurgy processing followed by Spark Plasma Sintering was performed to prepare the sinters. According to our knowledge, this is the first attempt to apply delaminated MXene phases as a reinforcing phases of ceramic matrix composites. The delaminated MXene phases were characterized using a high-resolution transmission microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). Significant improvement of the fracture toughness and hardness for the composites reinforced with 1.5?wt% 2D Ti2C compared to the reference sample were observed. It is expected that the applied reinforcing phase will have an influence on the fracture mechanism, and so this has also been investigated. Two of the main mechanisms of crack propagations (crack deflection and bridging) were observed.  相似文献   
29.
Alkylphospholipids are synthetic analogues of endogenous phosphatidylcholines with a remarkable ability: induce the selective apoptosis of exponentially growing tumor cells. One hypothesis concerning their mechanism of action is the inhibition of cytidine triphosphate:phosphocholine cytidyltransferase (CCT), which would significantly suppress the phosphatidylcholine biosynthesis to trigger apoptosis. Herein, homology modeling, docking simulations, and the analyses of molecular interaction fields are used to suggest the most probable binding modes of four alkylphospholipids (edelfosine, erucylphosphocholine, perifosine, and miltefosine) and lysophosphatidylcholine at the catalytic domain of human CCT. All compounds display bind modes in agreement with the corresponding groups found in the CCT substrate, phosphocholine, while their binding strengths are increased because of the interaction of the alkyl chains with hydrophobic residues from the M domain of the protein. Analyses of the geometry of the CCT binding‐site also suggest that small groups, such as benzyl/2‐phenylethyl ethers or equivalent heterocycles, could replace the O‐methyl group in edelfosine to yield even better inhibitors. It is believed this study can guide the development of new alkylphospholipids with an improved profile for the inhibition of phosphatidylcholine biosynthesis, a critical component for cell cycle progression that can be explored in cancer chemotherapy. Practical Applications: Studies focusing on the interactions between small ligands and their protein targets are decisive for the comprehension of how conformational changes in the macromolecular structure dictates the biological activity and, consequently, how they can be explored in drug discovery. Most of the current studies on alkylphospholipids focuses on their physicochemical interactions with cholesterol and sphingolipids in lipid rafts that, because of the variability and complexity of the membrane phases, hardly can provide structural data in the X‐ray crystallography assays necessary for molecular modeling studies. Therefore, by exploring the inhibition of human cytidine triphosphate:phosphocholine cytidyltransferase as an alternative and, probably, complementary hypothesis to the membrane rafts, a helpful strategy can be provided to overcome the clinical limitations of alkylphospholipids.  相似文献   
30.
If and only if each single cue uniquely defines its target, an independence model based on fragment theory can predict the strength of a combined dual cue from the strengths of its single cue components. If the single cues do not each uniquely define their target, no single monotonic function can predict the strength of the dual cue from its components; rather, what matters is the number of possible targets. The probability of generating a target word was .19 for rhyme cues, .14 for category cues, and .97 for rhyme-plus-category dual cues. Moreover, some pairs of cues had probabilities of producing their targets of .03 when used individually and 1.00 when used together, whereas other pairs had moderate probabilities individually and together. The results, which are interpreted in terms of multiple constraints limiting the number of responses, show why rhymes, which play a minimal role in laboratory studies of memory, are common in real-world mnemonics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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