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   6607篇
  免费   488篇
  国内免费   11篇
电工技术   121篇
综合类   3篇
化学工业   1706篇
金属工艺   175篇
机械仪表   224篇
建筑科学   177篇
矿业工程   17篇
能源动力   287篇
轻工业   1335篇
水利工程   64篇
石油天然气   44篇
无线电   397篇
一般工业技术   1096篇
冶金工业   652篇
原子能技术   49篇
自动化技术   759篇
  2024年   25篇
  2023年   78篇
  2022年   211篇
  2021年   350篇
  2020年   227篇
  2019年   288篇
  2018年   305篇
  2017年   332篇
  2016年   283篇
  2015年   207篇
  2014年   284篇
  2013年   526篇
  2012年   413篇
  2011年   448篇
  2010年   316篇
  2009年   353篇
  2008年   309篇
  2007年   261篇
  2006年   221篇
  2005年   140篇
  2004年   139篇
  2003年   137篇
  2002年   116篇
  2001年   78篇
  2000年   83篇
  1999年   85篇
  1998年   194篇
  1997年   148篇
  1996年   121篇
  1995年   69篇
  1994年   56篇
  1993年   53篇
  1992年   27篇
  1991年   16篇
  1990年   29篇
  1989年   17篇
  1988年   26篇
  1987年   11篇
  1986年   14篇
  1985年   13篇
  1984年   7篇
  1982年   6篇
  1981年   8篇
  1980年   7篇
  1978年   6篇
  1977年   6篇
  1976年   20篇
  1975年   7篇
  1974年   7篇
  1973年   6篇
排序方式: 共有7106条查询结果,搜索用时 15 毫秒
991.
Journal of Materials Science: Materials in Electronics - In this paper, CaWO4 nanoparticles were prepared by the hydrothermal method using the temperature of 100 (CaWO4-100), 120 (CaWO4-120), 140...  相似文献   
992.
Scientometrics - In this paper, we address the main differences of the scientific production between internal and external researcher groups of a synchrotron radiation facility. Through the...  相似文献   
993.
Chitin was used to prepare an alternative, eco–friendly and low–cost adsorbent by a simple pyrolysis process. The adsorbent, named chitin derived biochar, was characterized and applied to treat colored effluents containing methyl violet dye (MV). Pyrolysis using N2 flow rate of 0.25 L min?1, heating rate of 10 °C min?1 until 800 °C was suitable to prepare a chitin derived biochar with good characteristics. Chitin derived biochar presented surface area of 275.0 m2 g?1. The MV adsorption on the chitin derived biochar was favored in alkaline conditions and ambient temperature. The adsorption process presented fast kinetics and, the maximum adsorption capacity was higher than 1000 mg g?1. Chitin derived biochar can be used for 7 consecutive adsorption/desorption cycles maintaining the same adsorption capacity. Also, the material was suitable to treat colored effluents, reaching color removal percentage of 95%. In brief, it was demonstrated that chitin derived biochar is a low–cost and efficient material to treat colored effluents.  相似文献   
994.
Recently, stretchable micro-supercapacitors (MSCs) that can be easily integrated into electronic devices have attracted research and industrial attentions. In this work, three-dimensional (3D) stretchable MSCs with an octet-truss electrode (OTE) design have been demonstrated by a rapid digital light processing (DLP) process. The 3D-printed electrode structure is beneficial for electrode-electrolyte interface formation and consequently increases the number of ions adsorbed on the electrode surface. The designed MSCs can achieve a high capacitance as ≈74.76 mF cm−3 under 1 mA cm−3 at room temperature even under a high mechanical deformation, and can achieve 19.53 mF cm−3 under 0.1 mA cm−3 at a low temperature (−30 °C). Moreover, finite element analysis (FEA) reveals the OTE structure provides 8 times more contact area per unit volume at the electrode-electrolyte interface compared to the traditional interdigital electrode (IDE). This work combines structural design and 3D printing techniques, which provides new insights into highly stretchable MSCs for next-generation electronic devices.  相似文献   
995.
Journal of Materials Science - Flexible self-standing supercapacitor devices (FSSS) have attracted great attention in several areas due to their potential use in a wide range of applications, such...  相似文献   
996.
Journal of Materials Science - Organic–inorganic (O–I) hybrid nanocomposites have already been widely investigated in the optoelectronic industry and are emerging in the biomedical...  相似文献   
997.
Journal of Materials Science: Materials in Electronics - This study reports the electrical properties of Nd-doped cerium oxide (CeO2) films synthesized by microwave assisted hydrothermal using a...  相似文献   
998.
With recent advances in DNA technology, questions have arisen as to how this technology should be appropriately used. In this article, results obtained from a survey designed to elicit attitudes of college students to prenatal testing and gene therapy for human attributes and psychiatric conditions are reported. The eleven hypothetical disease phenotypes included schizophrenia, alcoholism, tendency toward violent behavior, attention deficit/hyperactivity disorder, depression requiring medical treatment, obesity, involvement in "dangerous" sports activities, homosexuality, borderline normal IQ (80-100), proportional short stature, and inability to detect perfect pitch. Most students supported prenatal genetic testing for psychiatric disorders and behavior that might result in harm to others (i.e., tendency towards violent behavior) and found prenatal genetic testing for human attributes less desirable. However, the lack of unilateral agreement or disagreement toward any one condition or attribute suggests the potential difficulties ahead in the quest for guidelines for the application of new technologies available to manipulate the human genome.  相似文献   
999.
Worldwide, fishways are increasingly criticized for failing to meet conservation goals. We argue that this is largely due to the dominance of diadromous species of the Northern Hemisphere (e.g., Salmonidae) in the research that underpins the concepts and methods of fishway science and management. With highly diverse life histories, swimming abilities and spatial ecologies, most freshwater fish species do not conform to the stereotype imposed by this framework. This is leading to a global proliferation of fishways that are often unsuitable for native species. The vast majority of fish populations do not undertake extensive migrations between clearly separated critical habitats, yet the movement of individuals and the genetic information they carry is critically important for population viability. We briefly review some of the latest advances in spatial ecological modelling for dendritic networks to better define what it means to achieve effective fish passage at a barrier. Through a combination of critical habitat assessment and the modelling of metapopulations, climate change‐driven habitat shifts, and adaptive gene flow, we recommend a conceptual and methodological framework for fishway target‐setting and monitoring suitable for a wide range of species. In the process, we raise a number of issues that should contribute to the ongoing debate about fish passage research and the design and monitoring of fishways.  相似文献   
1000.

The growth of density and circulation speed of railway transportation systems in urban areas increases the importance of the research issues of the produced environmental impacts. This study presents a field data analysis, obtained during monitoring campaigns of ground vibration, due to light railway traffic in urban areas, based on the artificial neural network (ANN) approach, using quantitative and qualitative predictors. Different ANN-based models, using those predictors, were evaluated/trained and validated. Using several criteria, including those that measures the possibility of ANN overfitting (RR2) and complexity (AIC), the best ANN model was successfully obtained for Lisbon area. This model, with 16 input elements (quantitative and qualitative predictors), 2 neurons on the hidden layer with a hyperbolic tangent sigmoid transfer function, and 1 neuron on the output layer considering a linear transfer function, has 0.9720 for the coefficient of determination and 0.5293 for the sum squared error.

  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