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   2398篇
  免费   188篇
  国内免费   2篇
电工技术   30篇
综合类   2篇
化学工业   705篇
金属工艺   61篇
机械仪表   91篇
建筑科学   81篇
矿业工程   4篇
能源动力   57篇
轻工业   485篇
水利工程   33篇
石油天然气   26篇
无线电   129篇
一般工业技术   357篇
冶金工业   243篇
原子能技术   20篇
自动化技术   264篇
  2024年   7篇
  2023年   31篇
  2022年   83篇
  2021年   122篇
  2020年   87篇
  2019年   113篇
  2018年   118篇
  2017年   100篇
  2016年   108篇
  2015年   79篇
  2014年   110篇
  2013年   199篇
  2012年   146篇
  2011年   163篇
  2010年   118篇
  2009年   125篇
  2008年   102篇
  2007年   86篇
  2006年   62篇
  2005年   56篇
  2004年   47篇
  2003年   33篇
  2002年   48篇
  2001年   34篇
  2000年   22篇
  1999年   26篇
  1998年   73篇
  1997年   56篇
  1996年   53篇
  1995年   29篇
  1994年   18篇
  1993年   23篇
  1992年   14篇
  1991年   10篇
  1990年   8篇
  1989年   9篇
  1988年   7篇
  1987年   6篇
  1986年   9篇
  1985年   5篇
  1980年   3篇
  1979年   7篇
  1978年   4篇
  1977年   4篇
  1976年   8篇
  1973年   3篇
  1968年   3篇
  1967年   2篇
  1963年   1篇
  1957年   1篇
排序方式: 共有2588条查询结果,搜索用时 0 毫秒
1.
2.
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with...  相似文献   
3.
4.
The central nervous system (CNS) is the most complex structure in the body, consisting of multiple cell types with distinct morphology and function. Development of the neuronal circuit and its function rely on a continuous crosstalk between neurons and non-neural cells. It has been widely accepted that extracellular vesicles (EVs), mainly exosomes, are effective entities responsible for intercellular CNS communication. They contain membrane and cytoplasmic proteins, lipids, non-coding RNAs, microRNAs and mRNAs. Their cargo modulates gene and protein expression in recipient cells. Several lines of evidence indicate that EVs play a role in modifying signal transduction with subsequent physiological changes in neurogenesis, gliogenesis, synaptogenesis and network circuit formation and activity, as well as synaptic pruning and myelination. Several studies demonstrate that neural and non-neural EVs play an important role in physiological and pathological neurodevelopment. The present review discusses the role of EVs in various neurodevelopmental disorders and the prospects of using EVs as disease biomarkers and therapeutics.  相似文献   
5.
The term atmospheric residue describes the material at the bottom of the atmospheric distillation tower having a lower boiling point limit of about 340°C; the term vacuum residue (heavy petroleum fractions) refers to the bottom of the vacuum distillation, which has an atmospheric equivalent boiling point (AEBP) above 540°C. In this work, the objective is to evaluate the behavior of different kinds of Brazilian atmospheric and vacuum residues using molecular distillation. The Falling Film Molecular Distillator was used. For the results obtained through this process, a significant range of temperature can be explored avoiding the thermal decomposition of the material. So these results are very important to the refinery decisions and improvements. The Experimental Factorial Design results showed that the temperature has more influence on the process than the feed flow rate, when a higher percentage of distillate is required.  相似文献   
6.
In this paper we compare the dynamics on the centre manifold of the solutions of an ill-posed Boussinesq equation with a well-posed version. We show that the dynamics in the centre manifold of the ill-posed equation tracks the dynamics of the well-posed equation. Our results give partial justification to the long-wave perturbation theory.  相似文献   
7.
Female SJL mice are more susceptible than male mice to experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein (MBP)-specific T lymphocytes. In the present study, we examined mechanisms involved in this gender-related difference in disease susceptibility. MBP-specific T lymphocytes derived from spleens of males during the effector phase of adoptive EAE produced significantly higher levels of IL-10, an anti-inflammatory cytokine in EAE. A protective effect of testosterone was then shown. Females implanted with dihydrotestosterone pellets demonstrated a significantly less severe course of EAE as compared with females implanted with placebo pellets. Finally, MBP-specific T lymphocytes derived from dihydrotestosterone-implanted females produced significantly higher levels of IL-10 than those from placebo. Together these data indicate that testosterone exerts a protective effect in EAE that is mediated at least in part by enhanced production of IL-10 by autoantigen-specific T lymphocytes.  相似文献   
8.
This paper assesses the impacts of a GTL plant on the expansion of Brazil's oil refining segment. The GTL plant (50,000 bpd) was sized to start up operations in 2015, producing diesel and naphtha through the indirect route (FT-synthesis). This plant will consume the non-associated natural gas production from the recent discoveries at the Santos Basin (around 419 Bm3), and the associated gas production from the Campos Basin. Both basins are located in the Southeast of Brazil, the most populated, rich and industrialized region of the country. Two different criteria for refinery expansion were simulated in order to meet oil product demand scenarios. Findings show that depending on the refinery expansion criteria considered GTL will play a fundamental hole to meet the oil product demand forecast to Brazil in the next 10 years.  相似文献   
9.
A.V. Machado  M. van Duin 《Polymer》2005,46(17):6575-6586
Simple blending and dynamic vulcanisation of EPDM/PE blends using the resol/SnCl2 system was studied in an extruder using a series of sampling devices. The melting of the PE pellets occurs just in front of and in the first kneading zone. Upon complete melting of the PE phase, the EPDM/PE blends reach very quickly their final morphology. Crosslinking of the EPDM phase to high levels occurs already when the PE phase is not yet fully molten. The higher the EPDM content, the higher the viscous dissipation, the higher the melt temperature and, consequently, the higher the crosslinking rate. For the EPDM/PE (50/50; w/w) TPV a transition from continuous via co-continuous to fully dispersed EPDM is observed, which is driven by crosslinking. Although the degree of crosslinking of the EPDM rubber is very high, this does not prevent phase inversion of the blend. The EPDM/PE interface is rather blurred, because PE crystalline lamellae are growing into the EPDM domains, probably because of the high compatibility between PE and EPDM (60 wt% of ethene). This study shows that dynamic vulcanisation in extruders proceeds quite differently from that in batch kneaders, where melting, mixing and crosslinking are separated in time. In extruders mass and heat transport, melting of the thermoplastic, morphology development (including dispersion and phase inversion), distribution and dissolution of (crosslinking) chemicals and crosslinking of the rubber do not occur as independent phenomena, but mutually and/or continuously interact.  相似文献   
10.
The combination of the techniques of expert systems and neural networks has the potential of producing more powerful systems, for example, expert systems able to learn from experience. In this paper, we address the combinatorial neural model (CNM), a kind of fuzzy neural network able to accommodate in a simple framework the highly desirable property of incremental learning, as well as the usual capabilities of expert systems. We show how an interval-based representation for membership grades makes CNM capable of reasoning with several types of uncertainty: vagueness, ignorance, and relevance commonly found in practical applications. In addition, we show how basic functions of expert systems such as inference, inquiry, censorship of input information, and explanation may be implemented. We also report experimental results of the application of CNM to the problem of deforestation monitoring of the Amazon region using satellite images  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