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   507篇
  免费   0篇
  国内免费   5篇
电工技术   9篇
化学工业   124篇
金属工艺   21篇
机械仪表   3篇
建筑科学   9篇
矿业工程   1篇
能源动力   16篇
轻工业   50篇
水利工程   1篇
无线电   41篇
一般工业技术   78篇
冶金工业   60篇
原子能技术   11篇
自动化技术   88篇
  2022年   7篇
  2021年   12篇
  2020年   6篇
  2019年   6篇
  2018年   6篇
  2017年   7篇
  2016年   12篇
  2015年   6篇
  2014年   10篇
  2013年   31篇
  2012年   23篇
  2011年   39篇
  2010年   25篇
  2009年   31篇
  2008年   30篇
  2007年   21篇
  2006年   21篇
  2005年   20篇
  2004年   14篇
  2003年   10篇
  2002年   10篇
  2001年   6篇
  2000年   5篇
  1999年   4篇
  1998年   8篇
  1997年   18篇
  1996年   7篇
  1995年   8篇
  1994年   4篇
  1993年   4篇
  1992年   7篇
  1990年   3篇
  1989年   10篇
  1988年   4篇
  1987年   4篇
  1986年   3篇
  1985年   7篇
  1984年   4篇
  1983年   3篇
  1981年   4篇
  1979年   8篇
  1978年   4篇
  1977年   7篇
  1975年   3篇
  1974年   2篇
  1973年   7篇
  1972年   3篇
  1971年   2篇
  1970年   4篇
  1968年   2篇
排序方式: 共有512条查询结果,搜索用时 16 毫秒
101.
Cross-flow ultrafiltration (UF) and osmotic distillation (OD) were implemented on laboratory scale to obtain formulations of interest for food and/or pharmaceutical industry starting from the blood orange juice produced in the Calabria region. The freshly squeezed juice, after a depectinization step, was submitted to an UF process in order to recover natural antioxidants, such as hydroxycinnamic acids, hydroxybenzoic acids, flavanones, flavan-3-ols, and anthocyanins. The UF permeate, with an initial total soluble solids (TSS) content of 10.5°Brix, was concentrated by OD up to a final concentration of 61.4°Brix.  相似文献   
102.
Vitamin A deficiency is a public health issue in developing countries and promoting dietary carotenoids as precursors is a promising strategy. However, carotenoids present in numerous fruits and vegetables are unstable and poorly bioaccessible. This study evaluated these two parameters during in vitro digestion of carotenoids and retinoids from carrot juice, raw and cooked spinach, micronutrient-fortified flour and standards without food matrix. Standards were unstable whereas vitamin A from fortified flour and native food carotenoids were generally better protected by the food matrix (30–100% remaining versus 7–30% for standards). Hydrothermal cooking did not influence spinach carotenoid digestive stability but decreased their contents, phenomenon compensated by a significantly better micellarisation from 15-fold for β-carotene to 72-fold for lutein. Finally, carrot juice provided the greatest amount of bioaccessible provitamin A with 1850 μg/100 g dry matter (DM) versus 790 and 80 μg/100 g DM in cooked and raw spinach, respectively.  相似文献   
103.
介绍了最新的激光视觉传感技术在汽车、造船、管道和铁路车辆等领域的自动化电弧焊接和激光焊接中的应用.先进且可靠的数字激光传感系统保证了电弧或激光热源能准确地对中准焊缝.在焊接过程中能够根据所测量的间隙和错边等数据实时地调整焊接过程参数,并在线检测焊后的焊缝成形和表面缺陷.从而保证焊接质量,并提高生产效率,降低总体焊接生产成本.应用这些适合焊接的智能化激光视觉传感技术.可以有效地提高焊接产品的质量和价格的竞争力.  相似文献   
104.
This paper addresses the Euclidean location-allocation problem with an unknown number of facilities, and an objective of minimizing the fixed and transportation costs. This is a NP-hard problem and in this paper, a three-stage ant colony optimization (ACO) algorithm is introduced and its performance is evaluated by comparing its solutions to the solutions of genetic algorithms (GA). The results show that ACO outperformed GA and reached better solutions in a faster computational time. Furthermore, ACO was tested on the relaxed version of the problem where the number of facilities is known, and compared to existing methods in the literature. The results again confirmed the superiority of the proposed algorithm.  相似文献   
105.
随着安全关键系统对计算性能要求的日趋提高,能够提供更强计算能力而又减少电子设备的体积、重量和功耗的多核处理器将在安全关键领域得到广泛应用.同步语言能够表达确定性并发行为且具有精确时间语义等特性,适用于安全关键软件的建模和验证.目前,同步语言SIGNAL编译器主要支持串行代码生成,较少关注多线程代码生成.提出一种同步语言SIGNAL多线程代码生成工具.首先将SIGNAL程序转换为经过时钟演算的S-CGA中间程序;之后将S-CGA中间程序转换为时钟数据依赖图以分析依赖关系;然后对时钟数据依赖图进行拓扑排序划分,并针对划分结果提出优化算法和基于流水线方式的任务划分方法;最后将划分结果转换为虚拟多线程结构并进一步生成可执行多线程C/Java代码.通过在多核处理器上的实验,验证了所提方法的有效性.  相似文献   
106.
Cellular senescence is recognized as a dynamic process in which cells evolve and adapt in a context dependent manner; consequently, senescent cells can exert both beneficial and deleterious effects on their surroundings. Specifically, senescent mesenchymal stromal cells (MSC) in the bone marrow (BM) have been linked to the generation of a supporting microenvironment that enhances malignant cell survival. However, the study of MSC’s senescence role in leukemia development has been straitened not only by the availability of suitable models that faithfully reflect the structural complexity and biological diversity of the events triggered in the BM, but also by the lack of a universal, standardized method to measure senescence. Despite these constraints, two- and three dimensional in vitro models have been continuously improved in terms of cell culture techniques, support materials and analysis methods; in addition, research on animal models tends to focus on the development of techniques that allow tracking leukemic and senescent cells in the living organism, as well as to modify the available mice strains to generate individuals that mimic human BM characteristics. Here, we present the main advances in leukemic niche modeling, discussing advantages and limitations of the different systems, focusing on the contribution of senescent MSC to leukemia progression.  相似文献   
107.
Understanding the regulation of the testicular endocrine function leading to testosterone production is a major objective as the alteration of endocrine function is associated with the development of many diseases such as infertility. In the last decades, it has been demonstrated that several endogenous molecules regulate the steroidogenic pathway. Among them, bile acids have recently emerged as local regulators of testicular physiology and particularly endocrine function. Bile acids act through the nuclear receptor FXRα (Farnesoid-X-receptor alpha; NR1H4) and the G-protein-coupled bile acid receptor (GPBAR-1; TGR5). While FXRα has been demonstrated to regulate testosterone synthesis within Leydig cells, no data are available regarding TGR5. Here, we investigated the potential role of TGR5 within Leydig cells using cell culture approaches combined with pharmacological exposure to the TGR5 agonist INT-777. The data show that activation of TGR5 results in a decrease in testosterone levels. TGR5 acts through the PKA pathway to regulate steroidogenesis. In addition, our data show that TGR5 activation leads to an increase in cholesterol ester levels. This suggests that altered lipid homeostasis may be a mechanism explaining the TGR5-induced decrease in testosterone levels. In conclusion, the present work highlights the impact of the TGR5 signaling pathway on testosterone production and reinforces the links between bile acid signaling pathways and the testicular endocrine function. The testicular bile acid pathways need to be further explored to increase our knowledge of pathologies associated with impaired testicular endocrine function, such as fertility disorders.  相似文献   
108.
Cubane molecules hold great potential for medicinal chemistry applications due to their inherent stability and low toxicity. In this study, we report the synthesis of a cubane derivative phosphoramidite for the incorporation of cubane into small interfering RNAs (siRNAs). Synthetic siRNAs rely on chemical modifications to improve their pharmacokinetic profiles. However, they are still able to mediate sequence-specific gene silencing via the endogenous RNA interference pathway. We designed a library of siRNAs bearing cubane at different positions within the sense and antisense strands. All siRNAs showed excellent gene-silencing activity, with IC50 values ranging from 45.4 to 305 pM. Incorporating the cubane modification in both the sense and antisense strand led to viable duplexes with good biological activity. To the best of our knowledge, this is the first report of siRNAs bearing a cubane derivative within the backbone.  相似文献   
109.
A detailed analysis of the microstructure of zinc oxide produced by thermal decomposition of zinc oxalate at temperatures in the range 328° to 650°C is described. Parameters describing the breadth and shape of X-ray diffraction line profiles were obtained by means of pattern decomposition, and a method based on the Voigt function was used to obtain information on the temperature dependence of the microstructure. It was found that the crystallites are prismatic, the dimensions increasing significantly with formation temperature, and that each contains one stacking fault, on average. The results of size determinations are in broad agreement with TEM and SEM measurements. The specific surface area of the crystallites, obtained by the BET method, is compared with the results of X-ray diffraction line-profile analysis, leading to a determination of the variation of "packing factor" with temperature. Results suggest a homogeneous crystallite growth in the initial sintering of the loosely packed zinc oxide powder.  相似文献   
110.
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