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   1627篇
  免费   85篇
  国内免费   2篇
电工技术   7篇
综合类   1篇
化学工业   417篇
金属工艺   22篇
机械仪表   32篇
建筑科学   45篇
矿业工程   1篇
能源动力   56篇
轻工业   287篇
水利工程   14篇
石油天然气   7篇
无线电   169篇
一般工业技术   249篇
冶金工业   148篇
原子能技术   14篇
自动化技术   245篇
  2024年   4篇
  2023年   27篇
  2022年   99篇
  2021年   94篇
  2020年   50篇
  2019年   58篇
  2018年   54篇
  2017年   45篇
  2016年   61篇
  2015年   47篇
  2014年   76篇
  2013年   111篇
  2012年   99篇
  2011年   126篇
  2010年   79篇
  2009年   64篇
  2008年   84篇
  2007年   63篇
  2006年   40篇
  2005年   43篇
  2004年   38篇
  2003年   34篇
  2002年   26篇
  2001年   16篇
  2000年   19篇
  1999年   21篇
  1998年   58篇
  1997年   37篇
  1996年   30篇
  1995年   17篇
  1994年   14篇
  1993年   15篇
  1992年   7篇
  1991年   2篇
  1990年   6篇
  1989年   5篇
  1988年   7篇
  1987年   5篇
  1986年   5篇
  1985年   4篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   5篇
  1978年   4篇
  1977年   4篇
  1975年   2篇
  1971年   1篇
  1964年   1篇
排序方式: 共有1714条查询结果,搜索用时 15 毫秒
51.
52.
The use of the laser beam‐induced current (LBIC) technique in photovoltaic devices is widespread, but its use in photoelectrochemical cells, such as dye‐sensitized solar cells (DSSCs), is limited due to the configuration of these devices. The main reason is the very slow response time of DSSCs in the decay process, and therefore LBIC scans take too long to perform. We have designed a procedure published in the literature to correct the photocurrent values obtained by the LBIC technique, based on an algorithm that uses a decreasing mono‐exponential model. This work presents a study of the decay measurements in DSSCs using several functions, in order to improve the algorithm designed. It concludes that functions such as a decreasing bi‐exponential or Becquerel function generate better fits to experimental data. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
53.
This study is aimed at the thermal analysis of sealant mortar (usually a mixtures of bentonite and cemem with addition of sand) used in geothermal cooling and heating. In particular, thermal conductivity and diffusivity measurements were performed on differem sealant mixtures by using Hot Disk thermal constants analyzer in order to identify the interesting thermal properties of grouting materials. The grouting materials that we considered are of porous nature and, if used in the presence of groundwater, have different levels of imbibitions. It is important to know the thermal behavior of these materials at different water content. A first set of measurements was performed on a not-tinted material at room temperature; then the samples were led to saturation conditions by contact capillary imbibitions with a cotton wool layer moistened in water. The determination of thermal conductivity in these test conditions appears to be critical compared to the measuremems on non-timed sample. The thermal conductivity tests have revealed how the thermal behavior of the samples analyzed is essentially determined by the density and water content of the material: in fact, the thermal conductivity increases of two to three times the value of the not-tinted material.  相似文献   
54.
55.
Widespread trends of abandonment have strongly affected Mediterranean mountains after the Second World War, triggering spontaneous recolonisation of forests. A diachronic analysis of the landscape in a Natura 2000 site (Tuscany, Italy) was carried out using digital aerial photographs (1954, 2013) and a GIS-based methodology, focusing on territories above 1300 m a.s.l. The detected variations of total areas, patch shape, patch dimensions and selected metrics showed a notable shift of the vegetation towards woody types and a drastic reduction of open grasslands, some with high conservation value, accompanied by a strong increase in patch number, surface and edge. A decrease of SDI and SEI diversity indices was also observed. Considering that fragmentation is one of the main causes threatening habitats and species, our results point out a clear necessity for a monitoring programme and suitable actions aimed at improving the status of biodiversity-rich montane grasslands.  相似文献   
56.
Synthetic calcium phosphates (CaPs) are the most widely accepted bioceramics for the repair and reconstruction of bone tissue defects. The recent advancements in materials science have prompted a rapid progress in the preparation of CaPs with nanometric dimensions, tailored surface characteristics, and colloidal stability opening new perspectives in their use for applications not strictly related to bone. In particular, the employment of CaPs nanoparticles as carriers of therapeutic and imaging agents has recently raised great interest in nanomedicine. CaPs nanoparticles, as well as other kinds of nanoparticles, can be engineered to specifically target the site of the disease (cells or organs), thus minimizing their dispersion in the body and undesired organism-nanoparticles interactions. The most promising and efficient approach to improve their specificity is the ‘active targeting’, where nanoparticles are conjugated with a targeting moiety able to recognize and bind with high efficacy and selectivity to receptors that are highly expressed only in the therapeutic site. The aim of this review is to give an overview on advanced targeted nanomedicine with a focus on the most recent reports on CaP nanoparticles-based systems, specifically designed for the active targeting. The distinctive characteristics of CaP nanoparticles with respect to the other kinds of nanomaterials used in nanomedicine are also discussed.  相似文献   
57.
58.
This study aimed to evaluate the physicochemical characteristics and sensory attributes of beef burgers with the addition of pea fibre as a partial substitute of meat or fat. Three formulations were prepared: control (CON) – similar to the commercial formulation; fibre/less meat (FLM)—5% meat reduction and addition of 1% pea fibre; fibre/less fat (FLF)—7% fat reduction and addition of 1% pea fibre. Non-significant differences were obtained for pH, colour parameters (L* and b*), texture profile, cooking loss and size reduction among formulations. Moreover, sensory analysis with consumers of beef burgers did not indicate differences among the formulations for all the analysed attributes. Therefore, pea fibre is a promising partial replacer for meat and fat in beef burgers due to the preservation of technological parameters and sensory acceptance.  相似文献   
59.
A diet based on sunflower cake for lambs was assayed in order to reuse biodiesel industrial by-products with the aim of reducing livestock costs and evaluating their influence on meat quality. To achieve these goals, sixteen male lambs were fed diets containing different levels of sunflower cake (control, 5%, 10% and 15%). Afterwards, their semimembranosus muscles were analysed by two-dimensional electrophoresis coupled to mass spectrometry and their functional protein association was examined using STRING. Structural and metabolic proteins in the lambs’ proteomes changed significantly according to their diet. Fifteen proteins showed significant changes caused by the inclusion of sunflower cake, and the most differentially abundant structural proteins were detected in 2-DE gels from the lambs. Differentially abundant metabolic proteins such as ENO3 (enolase 3), MDH1 (malate dehydrogenase) and ALDH1A1 (retinal dehydrogenase) have been proposed as biomarkers of quality parameters in other species.  相似文献   
60.
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