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   157篇
  免费   4篇
  国内免费   5篇
化学工业   47篇
金属工艺   3篇
机械仪表   9篇
建筑科学   4篇
矿业工程   1篇
能源动力   9篇
轻工业   11篇
水利工程   1篇
无线电   6篇
一般工业技术   31篇
冶金工业   8篇
原子能技术   1篇
自动化技术   35篇
  2024年   1篇
  2023年   8篇
  2022年   14篇
  2021年   15篇
  2020年   12篇
  2019年   15篇
  2018年   16篇
  2017年   9篇
  2016年   12篇
  2015年   5篇
  2014年   9篇
  2013年   12篇
  2012年   8篇
  2011年   5篇
  2010年   2篇
  2009年   4篇
  2008年   1篇
  2006年   1篇
  2005年   1篇
  2004年   2篇
  2003年   1篇
  1999年   1篇
  1998年   3篇
  1996年   1篇
  1994年   1篇
  1988年   1篇
  1985年   1篇
  1984年   2篇
  1982年   1篇
  1981年   2篇
排序方式: 共有166条查询结果,搜索用时 15 毫秒
61.
62.
The current study aimed to investigate the palyno-morphological features of Asteraceous species from District Dera Ismail Khan, Khyber Pakhtunkhwa, Pakistan. A total of 13 species were collected, pressed, identified, and examined by using light and scanning electron microscopy. Both qualitative and quantitative pollen characters were observed, that is, equatorial and polar diameter, number of pores and colpi, exine thickness, exine sculpturing, pollen shape, and P/E ratio. Pollen shapes observed in studied taxa were spheroidal, suboblate, oblate-spheroidal, and lophate-spheroidal. The aperturation patterns of pollens vary from tricolporate to tetracolporate. The maximum polar and equatorial diameter of 75–100 (87.5 ± 13.6) μm and 87.5–117.5 (102.5 ± 16.4) μm, respectively, was recorded in Echinops echinatus, while minimum polar and equatorial diameter of 20–22.5 (21 ± 1.36) μm and 22.5–25 (23.5 ± 1.36) μm, respectively, was recorded in Aster subulatus. Six types of exine sculpturing patterns were observed; echinate, micro-echinate, echinate-microreticulate, microreticulate, echinate-perforate, and scabrate. Maximum exine thickness of 8.75 μm was recorded in E. echinatus and minimum of 1.25 μm in Launaea mucronata. The pollen morphology has valuable significance in understanding the taxonomy of different plant groups and plays a central role in the correct identification and classification of Asteraceous flora at species, generic, and tribe levels.  相似文献   
63.
The pollen morphology, with special reference to exine sculpture, of some species of the gymnosperms was assessed for the first time from the subalpine and alpine zones of western Himalayas northern Pakistan. The pollen of all these species is airborne and allergenic, so pollen morphology helps for identification of this allergenic pollen at specific level. Different morpho-palynological characteristics were analyzed including size range of pollen, polar and equatorial diameter ratio, exine ornamentation, sculpturing, exine thickness, pollen type, and shape. For accurate and quick identification of species, taxonomic key was made based on different morpho-palynological characteristics. The quantitative data were processed using SPSS software. Gymnospermal pollen includes inaperturate, rarely 1-colpate observed in (Cupressaceae), hexazonocolpate in (Ephedraceae), vesiculate, bissacate in (Pinaceae), and inaperturate in (Taxaceae). Different pollen shapes observed were prolate (4 spp), sub-spheroidal (7 spp), and oblate (1 spp). Variation was observed in exine sculpturing granular (4 spp), reticulate (1 spp), areolate-punctate (3 spp), and psilate (2 spp). This is based on the analysis of 10 plants belonging to four families of gymnosperms. Distinct pollen shape has emerged as the most diagnostic feature to separate some genera such as spheroidal in (Cupressaceae, Taxaceae), prolate and radiosymmetrical in (Ephedraceae), and bilateral in (Pinaceae). Exine thickness and sculpturing proved to be helpful at generic and specific levels. The results reinforced the significance of gymnospermal pollen morphological features which were used as aid for valuable taxonomic tool in plant systematics.  相似文献   
64.
Carica papaya is an economically vivacious plant of tropical and subtropical regions, cultivated in over 50 countries across the world with 6.8 million tons production. Papaya holds a broad spectrum of phytochemicals, including polysaccharides, vitamins, minerals, enzymes, proteins, glycosides, saponins, flavonoids, and phytosterols. These bioactive components are responsible for the pharmacological properties of this auspicious plant and demonstrate its importance in daily intake and alimentation. Additionally, it is an excellent aid to digestion and also hydrolyzing gluten, which is an important aspect for dyspeptic and celiac disease patients. Papaya acts as an antioxidant, antimicrobial, anticarminative, anticancer, and has hepato-protective, immunological, and other therapeutic attributes. The seed and pulp of papaya have bacteriostatic effects against several enteropathogens, such as Bacillus subtilus and E. coli. In the current review, pharmacological attributes, nutritional value of papaya, and medicinal properties of its various parts have been elaborated to provide collective information on this multipurpose commercial plant. Moreover, its role in the production of alcohol and carboxymethyl cellulose is also the limelight of the article. Furthermore, the present review article summarizes the literature pertaining to its pharmakinetics and also allies its health claims. Yet, the authors are still of the view that further research needs to be conducted for meticulousness.  相似文献   
65.
Titanium dioxide nanofibers were synthesized using electrospinning technique. The nanofibers were porous with an average diameter and length of ~150 nm and 200 μm, respectively. Humidity-sensing devices were fabricated by lithographically defined aluminum electrodes on top of the nanofibers deposited on silicon dioxide grown thermally on a silicon substrate. The performance of a TiO2 nanofiber humidity sensor was tested by AC and DC electrical measurements at 40–90% relative humidity. The response and the recovery time were 1 s and 4 s, respectively, between 40% and 90% relative humidity. The sensitivity of the TiO2 humidity sensor in the range of 40–90% RH was 150 MΩ/%RH and 20 MΩ/%RH at 10 Hz and 100 Hz, respectively. The excellent sensing characteristics are attributed to the porous nature and the small diameter of the nanofibers.  相似文献   
66.
The novel coronavirus disease, caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), rapidly spreading around the world, poses a major threat to the global public health. Herein, we demonstrated the binding mechanism of PF-07321332, α-ketoamide, lopinavir, and ritonavir to the coronavirus 3-chymotrypsin-like-protease (3CLpro) by means of docking and molecular dynamic (MD) simulations. The analysis of MD trajectories of 3CLpro with PF-07321332, α-ketoamide, lopinavir, and ritonavir revealed that 3CLpro–PF-07321332 and 3CLpro–α-ketoamide complexes remained stable compared with 3CLpro–ritonavir and 3CLpro–lopinavir. Investigating the dynamic behavior of ligand–protein interaction, ligands PF-07321332 and α-ketoamide showed stronger bonding via making interactions with catalytic dyad residues His41–Cys145 of 3CLpro. Lopinavir and ritonavir were unable to disrupt the catalytic dyad, as illustrated by increased bond length during the MD simulation. To decipher the ligand binding mode and affinity, ligand interactions with SARS-CoV-2 proteases and binding energy were calculated. The binding energy of the bespoke antiviral PF-07321332 clinical candidate was two times higher than that of α-ketoamide and three times than that of lopinavir and ritonavir. Our study elucidated in detail the binding mechanism of the potent PF-07321332 to 3CLpro along with the low potency of lopinavir and ritonavir due to weak binding affinity demonstrated by the binding energy data. This study will be helpful for the development and optimization of more specific compounds to combat coronavirus disease.  相似文献   
67.
Interleukin-10 (IL-10) is a vital regulatory cytokine, which plays a constructive role in maintaining immune tolerance during an alloimmune inflammation. Our previous study highlighted that IL-10 mediated immunosuppression established the immune tolerance phase and thereby modulated both microvascular and epithelial integrity, which affected inflammation-associated graft malfunctioning and sub-epithelial fibrosis in rejecting allografts. Here, we further investigated the reparative effects of IL-10 on microvasculature and epithelium in a mouse model of airway transplantation. To investigate the IL-10 mediated microvascular and epithelial repair, we depleted and reconstituted IL-10, and monitored graft microvasculature, airway epithelium, and associated repair proteins. Our data demonstrated that both untreated control allografts and IL-10 (−) allografts showed a significant early (d6) increase in microvascular leakiness, drop-in tissue oxygenation, blood perfusion, and denuded airway epithelium, which is associated with loss of adhesion protein Fascin-1 and β-catenin on vascular endothelial cells at d10 post-transplantation. However, IL-10 (+) promotes early microvascular and airway epithelial repair, and a proportional increase in endothelial Fascin-1, and β-catenin at d10 post-transplantation. Moreover, airway epithelial cells also express a significantly higher expression of FOXJ1 and β-catenin in syngrafts and IL-10 (+) allografts as compared to IL-10 (−) and untreated controls at d10 post-transplantation. Collectively, these findings demonstrated that IL-10 mediated microvascular and epithelial changes are associated with the expression of FOXJ1, β-catenin, and Fascin-1 proteins on the airway epithelial and vascular endothelial cells, respectively. These findings establish a potential reparative modulation of IL-10 associated microvascular and epithelial repair, which could provide a vital therapeutic strategy to facilitate graft repair in clinical settings.  相似文献   
68.
In numerous encryption frameworks, the first information is changed into encoded form by applying nonlinear substitutions and affecting diffusion. The goal of the nonlinear change is to accomplish high level of randomness in the image content. The choice of the source of randomness is critical because the success in cryptanalysis is demarked by the characteristics identified in the encrypted data. The chaotic frameworks show random conduct that is suitable for encryption applications where nonlinear transformations are needed in the middle of plaintext and the scrambled information. The application of nonlinear functional chaos-based system with embedded chaotic systems and binary chaotic sequences can prompt randomness and diffusion in the information. In addition to the high state of randomness, the requirement for various round keys is needed in a run of the mill substitution–permutation process. The proposed strategy kills the requirement for different round keys, which is suitable for high-speed communication frameworks. The measurable analyses performed on the proposed nonlinear algorithm which show improvement in encryption quality and safety against numerous brute-force and statistical attacks. Also, the proposed framework demonstrates high safety against differential and linear cryptanalysis.  相似文献   
69.
This research investigates the impacts of proactiveness, openness to experience, and extraversion on innovative performance among engineers. The work also examines the mediating role of knowledge sharing. Using a person–situation interaction perspective, the study further explores the moderating role of perceived organizational support (POS) in personality–knowledge sharing relationships. Data collected from engineers (N = 183) across various public and private engineering firms in Pakistan reveal that knowledge sharing mediated the relationship of proactiveness and extraversion with innovative performance. In addition, highly proactive and extraverted engineers are more likely to share knowledge when the POS is high. Contrary to the expectations, engineers who highly exhibit openness to experience are less likely to share knowledge under high POS. These findings provide significant contributions to the theory and practice of engineering management by highlighting the essential link of personality traits with knowledge sharing and innovation among engineers.  相似文献   
70.
Load balancing and task partitioning are important components of distributed computing. The optimum performance from the distributed computing system is achieved by using effective scheduling and load balancing strategy. Researchers have well explored CPU, memory, and I/O-intensive tasks scheduling, and load balancing techniques. But one of the main obstacles of the load balancing technique leads to the ignorance of applications having a mixed nature of tasks. This is because load balancing strategies developed for one kind of job nature are not effective for the other kind of job nature. We have proposed a load balancing scheme in this paper, which is known as Mixed Task Load Balancing (MTLB) for Cluster of Workstation (CW) systems. In our proposed MTLB strategy, pre-tasks are assigned to each worker by the master to eliminate the worker’s idle time. A main feature of MTLB strategy is to eradicate the inevitable selection of workers. Furthermore, the proposed MTLB strategy employs Three Resources Consideration (TRC) for load balancing (CPU, Memory, and I/O). The proposed MTLB strategy has removed the overheads of previously proposed strategies. The measured results show that MTLB strategy has a significant improvement in performance.  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