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   166篇
  免费   6篇
  国内免费   1篇
电工技术   2篇
综合类   2篇
化学工业   40篇
金属工艺   4篇
机械仪表   7篇
建筑科学   2篇
能源动力   7篇
轻工业   26篇
水利工程   3篇
石油天然气   1篇
无线电   8篇
一般工业技术   38篇
冶金工业   16篇
自动化技术   17篇
  2023年   4篇
  2022年   5篇
  2021年   10篇
  2020年   3篇
  2019年   4篇
  2018年   10篇
  2017年   4篇
  2016年   9篇
  2015年   5篇
  2014年   11篇
  2013年   23篇
  2012年   6篇
  2011年   7篇
  2010年   10篇
  2009年   7篇
  2008年   12篇
  2007年   8篇
  2006年   5篇
  2005年   3篇
  2004年   2篇
  2003年   2篇
  2002年   3篇
  2001年   1篇
  2000年   2篇
  1999年   2篇
  1996年   5篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1991年   2篇
  1986年   1篇
  1971年   1篇
  1969年   1篇
排序方式: 共有173条查询结果,搜索用时 31 毫秒
31.
Ground water is the main type of water used in aquaculture farming in Armenia. Ground water arrives under pressure from a depth of about 100–180 m.  相似文献   
32.
The efficiency of using nanostructured silver in technological processes of making red wine has been studied with the purpose of substituting sulfur dioxide. For preparation of research objects, we used dry wine material of red grape variety "Saperavi". After completion of malolactic fermentation, the second racking the wine material off the lees and its treatment with antiseptics were carried out. Sulfur dioxide (Kadifit) and different doses of nanostructured silver were used. Microbiological investigation was performed on the presence of lactic bacteria after completion of malolactic fermentation and racking off the lees. The investigation of phenolic compounds was conducted at the following stages of technological processes: (1) after completion of alcoholic fermentation and racking off the lees; (2) after completion of malolactic fermentation; (3) after the second racking off the lees and treatment with antiseptics. By means of the HPLC analysis, the amounts ofcatechins, phenolcarbonic acids and flavonols were determined. It has been established that after conduction of malolactic fermentation in the process of racking the wine material off the lees and storage, the application of 0.6 mg/L of nano-silver for blocking of lactic-acid bacteria and inhibition of oxidation of phenolic compounds has the same effect as sulfitization with 50 mg/L of Kadifit.  相似文献   
33.
34.
A series of A-ring modified oleanolic and ursolic acid derivatives including C28 amides (3-oxo-C2-nicotinoylidene/furfurylidene, 3β-hydroxy-C2-nicotinoylidene, 3β-nicotinoyloxy-, 2-cyano-3,4-seco-4(23)-ene, indolo-, lactame and azepane) were synthesized and screened for their cytotoxic activity against the NCI-60 cancer cell line panel. The results of the first assay of thirty-two tested compounds showed that eleven derivatives exhibited cytotoxicity against cancer cells, and six of them were selected for complete dose–response studies. A systematic study of local SARs has been carried out by comparative analysis of potency distributions and similarity relationships among the synthesized compounds using network-like similarity graphs. Among the oleanane type triterpenoids, C2-[4-pyridinylidene]-oleanonic C28-morpholinyl amide exhibited sub-micromolar potencies against 15 different tumor cell lines and revealed particular selectivity for non-small cell lung cancer (HOP-92) with a GI50 value of 0.0347 μM. On the other hand, superior results were observed for C2-[3-pyridinylidene]-ursonic N-methyl-piperazinyl amide 29, which exhibited a broad-spectrum inhibition activity with GI50 < 1 μM against 33 tumor cell lines and <2 μM against all 60 cell lines. This compound has been further evaluated for cell cycle analysis to decipher the mechanism of action. The data indicate that compound 29 could exhibit both cytostatic and cytotoxic activity, depending on the cell line evaluated. The cytostatic activity appears to be determined by induction of the cell cycle arrest at the S (MCF-7, SH-SY5Y cells) or G0/G1 phases (A549 cells), whereas cytotoxicity of the compound against normal cells is nonspecific and arises from apoptosis without significant alterations in cell cycle distribution (HEK293 cells). Our results suggest that the antiproliferative effect of compound 29 is mediated through ROS-triggered apoptosis that involves mitochondrial membrane potential depolarization and caspase activation.  相似文献   
35.
Combining aminoglycosides and loop diuretics often serves as an effective ototoxic approach to deafen experimental animals. The treatment results in rapid hair cell loss with extended macrophage presence in the cochlea, creating a sterile inflammatory environment. Although the early recruitment of macrophages is typically neuroprotective, the delay in the resolution of macrophage activity can be a complication if the damaged cochlea is used as a model to study subsequent therapeutic strategies. Here, we applied a high dose combination of systemic gentamicin and furosemide in C57 BL/6 and CBA/CaJ mice and studied the ototoxic consequences in the cochlea, including hair cell survival, ribbon synaptic integrity, and macrophage activation up to 15-day posttreatment. The activity of macrophages in the basilar membrane was correlated to the severity of cochlear damage, particularly the hair cell damage. Comparatively, C57 BL/6 cochleae were more vulnerable to the ototoxic challenge with escalated macrophage activation. In addition, the ribbon synaptic deterioration was disproportionately limited when compared to the degree of outer hair cell loss in CBA/CaJ mice. The innate and differential otoprotection in CBA/CaJ mice appears to be associated with the rapid activation of cochlear macrophages and a certain level of synaptogenesis after the combined gentamicin and furosemide treatment.  相似文献   
36.
Organic semiconductors are the focus of numerous studies; they are used in electronic devices. Modern research involves the production of neuromorphic organic materials, including those based on liquid crystal materials. The purpose of this work involves the theoretical modeling of molecules (the “core with branches” type) to construct a discotic mesophase capable of performing the functions of a neuromorphic material. For this purpose, the conductivity of crystal porphine, which can act as the nucleus of a molecule of the “core with branches” type, was investigated. The Marcus theory charge mobility values for the hole and electron were 0.148 and 0.088 cm2/V·s, respectively (the MOO method for calculating transfer integrals), and 0.561 and 0.160 cm2/V·s (DIPRO method). Based on TD-HF (HF-3c level of theory) calculations, possible structures of molecules for the formation of a discotic mesophase are proposed.  相似文献   
37.
An investigation of the effects of some additives on zinc electrowinning from a weak acidic sulphate electrolyte prepared from an industrial waste product has been carried out. Experiments were done in the presence of additives such as aluminium sulphate, animal glue and an extract of horse-chestnut nuts (HCE), used alone or in different mixtures.Using a rotating disc electrode (RDE) and cyclic voltammetry, the influence of the additives on the polarization curves and on the voltammograms was studied. SEM was used to determine the structure and the morphology of deposits.The results indicated that the additives tested exert a beneficial effect on the quality of the zinc deposits. They increase the cathodic polarization and promote levelling. Al2(SO4)3 influences the reduction of zinc ions, increasing the nucleation overpotential and the deposition rate of zinc on the cathode. The conjoint use of Al2(SO4)3, animal glue and HCE results in smooth, slightly bright deposits, showing a beneficial effect of the mixture on zinc electrodeposition. The analysis of deposit purity suggested that the additives inhibit the discharge rate of impurity metal ions, such as copper and lead, whose deposition is diffusion controlled.  相似文献   
38.
The article introduces an experimental system which produces multilingual semantic translations from relatively short texts from a given context. The system was conceived as an investigation instrument whose characteristics are the following: —the elaboration of a single analyzer and generator able to receive, in the form of data, specific information concerning national language, within the limits of a given area of application; —the use of exclusively semantic internal representation, whose formation is derived from “frames” (an object is defined as a list of “attribute-value” couples, permitting recursion); —a single knowledge-base is used for each natural language as initial data (the grammar transmitted was of a semantic-syntacticatn type); —the structure of grammar used in computer language processing being rarely as well adapted to analysis as to generation, the system itself is provided with the possibility of transforming and reorganizing the information for more efficient use at one stage of processing (thus, theatns are used directly in analysis, whereas for the purposes of generation they are “explored” and their information reorganized); —to produce a text, the use of general structuring principles (independent of language) are experimented with. These principles are given in the form of metarules. The application of these metarules to the restructured grammar of a natural language produces specific structuration rules, peculiar to this language. Although the system was conceived for any conceptual area or language, the present knowledge-base of the system (the experimental support) is based on a collection of elementary exercises in three-dimensional geometry written in Rumanian and in French. She does research in the CNRS group C.F. Picard headed by Professor Pitrat, University of Paris 6.  相似文献   
39.
The use of vivid packaging colors is a strategy to attract consumers' attention and interest. In this context, the awareness of harmful effects caused by the use of synthetic colorants has led to an increasing interest in naturally derived alternatives. The use of carotenoids as colorants for polymeric materials represents an environmentally friendly way of obtaining colored packaging. The incorporation of carotenoids extracts rich in bixin, lycopene, and β‐carotene into poly(lactic acid) films was evaluated, where the presence of carotenoids (100 μg/g) reduced oxygen permeability and presented a lubricant effect, increasing films elasticity up to 50%. No effect on films crystallinity was observed. Carotenoids reduced films transparency and bixin was the most stable carotenoid at dark and light conditions. The color stability of films, evaluated through kinetic parameters of color degradation, presented Chroma half‐life times (40 °C/light) of 111, 51, and 5 days for bixin, lycopene, and β‐carotene, respectively. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46585.  相似文献   
40.
Few studies have measured lower limb muscle activation during high knee flexion or investigated the effects of occupational safety footwear. Therefore, our understanding of injury and disease mechanisms, such as knee osteoarthritis, is limited for these high-risk postures. Peak activation was assessed in eight bilateral lower limb muscles for twelve male participants, while shod or barefoot. Transitions between standing and kneeling had peak quadriceps and tibialis anterior (TA) activations above 50% MVC. Static kneeling and simulated tasks performed when kneeling had peak TA activity above 15% MVC but below 10% MVC for remaining muscles. In three cases, peak muscle activity was significantly higher (mean 8.9% MVC) when shod. However, net compressive knee joint forces may not be significantly increased when shod. EMG should be used as a modelling input when estimating joint contact forces for these postures, considering the activation levels in the hamstrings and quadriceps muscles during transitions.

Practitioner Summary: Kneeling transitional movements are used in activities of daily living and work but are linked to increased knee osteoarthritis risk. We found peak EMG activity of some lower limb muscles to be over 70% MVC during transitions and minimal influence of wearing safety footwear.  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