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   40155篇
  免费   14944篇
  国内免费   31篇
电工技术   747篇
综合类   28篇
化学工业   16828篇
金属工艺   531篇
机械仪表   1079篇
建筑科学   1581篇
矿业工程   9篇
能源动力   1063篇
轻工业   7311篇
水利工程   314篇
石油天然气   62篇
武器工业   1篇
无线电   7541篇
一般工业技术   12107篇
冶金工业   1025篇
原子能技术   66篇
自动化技术   4837篇
  2024年   2篇
  2023年   85篇
  2022年   60篇
  2021年   400篇
  2020年   1553篇
  2019年   3268篇
  2018年   3212篇
  2017年   3533篇
  2016年   4016篇
  2015年   4062篇
  2014年   4087篇
  2013年   5283篇
  2012年   3086篇
  2011年   2802篇
  2010年   2957篇
  2009年   2837篇
  2008年   2363篇
  2007年   2136篇
  2006年   1886篇
  2005年   1556篇
  2004年   1488篇
  2003年   1327篇
  2002年   946篇
  2001年   650篇
  2000年   336篇
  1999年   163篇
  1998年   212篇
  1997年   174篇
  1996年   118篇
  1995年   93篇
  1994年   67篇
  1993年   61篇
  1992年   47篇
  1991年   42篇
  1990年   32篇
  1989年   43篇
  1988年   17篇
  1987年   26篇
  1986年   25篇
  1985年   20篇
  1984年   12篇
  1983年   7篇
  1982年   7篇
  1981年   7篇
  1980年   8篇
  1979年   2篇
  1978年   3篇
  1976年   7篇
  1971年   1篇
  1890年   1篇
排序方式: 共有10000条查询结果,搜索用时 44 毫秒
1.
Food Science and Biotechnology - The objective of this study was to develop a non-fermented probiotic milk that maintains its physicochemical properties, microbial properties, antioxidant activity,...  相似文献   
2.

Hydrological drought is assessed through river flow, which depends on river runoff and water withdrawal. This study proposed a framework to project future hydrological droughts considering agricultural water withdrawal (AWW) for shared socioeconomic pathway (SSP) scenarios. The relationship between AWW and potential evapotranspiration (PET) was determined using a deep belief network (DBN) model and then applied to estimate future AWW using projections of the twelve global climate models (GCMs). 12 GCMs were bias-corrected using the quantile mapping method, climate variables were generated, and river flow was estimated using the soil and water assessment tool (SWAT) model. The standardized runoff index (SRI) was used to project the changes in hydrological drought characteristics. The results revealed a higher occurrence of severe droughts in the future. Droughts would be more frequent in the near future (2021–2060) than in the far future (2061–2100) and more severe when AWW is considered. Droughts would also be more severe for SSP5-8.5 than for SSP2-4.5. The study revealed that the increased PET due to rising temperatures is the primary cause of the increased drought frequency and severity. The AWW will accelerate the drought severities in the future in the Yeongsan River basin.

  相似文献   
3.
利用改进的索氏提取回流法测量碳纤维原丝含油率.研究了溶剂回流温度、回流时间、环境湿度对测试结果的影响,结果表明:随着回流温度的提高,2小时内回流清洗效果不断增强,当回流温度大于54℃,次数大于12次,油剂清洗效果基本保持不变.可通过提高回流温度以提高单位时间内的回流次数,优化纤维含油率测试的准确性和测试效率.环境湿度对索氏提取测纤维含油率有显著影响:控制环境湿度在50~52%RH范围内,可将纤维吸潮质量变化控制在纤维质量的0.005%,油剂相对含量的0.2%~0.6%,可将测试稳定差值降低至≤0.05%,测试方法差值<0.1%,满足油剂测试工艺要求.回流时间≥2 h,回流温度≥54℃,测试环境湿度50~52%RH,索氏提取回流法油剂测试误差<0.05%.  相似文献   
4.
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production.  相似文献   
5.
6.
Amyloid precursor protein (APP) is a type 1 transmembrane glycoprotein, and its homologs amyloid precursor-like protein 1 (APLP1) and amyloid precursor-like protein 2 (APLP2) are highly conserved in mammals. APP and APLP are known to be intimately involved in the pathogenesis and progression of Alzheimer’s disease and to play important roles in neuronal homeostasis and development and neural transmission. APP and APLP are also expressed in non-neuronal tissues and are overexpressed in cancer cells. Furthermore, research indicates they are involved in several cancers. In this review, we examine the biological characteristics of APP-related family members and their roles in cancer.  相似文献   
7.
8.
9.
Jang  Hyun-Joo  Lee  Hyun-Jin  Yoon  Dong-Kyu  Ji  Da-Som  Kim  Ji-Han  Lee  Chi-Ho 《Food science and biotechnology》2018,27(1):219-225
Food Science and Biotechnology - This study aims to investigate antioxidative and antibacterial properties of fresh garlic (non-aged, NG) and aged garlic (AG) by-products extracted with distilled...  相似文献   
10.
Expanded graphite (EG) is introduced into poly(vinylidene fluoride) (PVDF) by melt mixing extrusion with water injection. The results demonstrate that the unfunctionalized EG in composite prepared with water injection exbibits better dispersion than that in the one prepared without water injection due to the promoting role of water during extrusion. Thus, the PVDF/EG composite with loading of 4 wt% prepared by water‐assisted mixing extrusion (WAME) exhibits electrical conductivity of about three orders of magnitude higher than the neat PVDF and one order of magnitude higher than the one prepared without water injection. Comparing to the neat PVDF, the thermal conductivity of the composites prepared with and without water injection is increased by 101.5% and 75.0%, respectively. The introduced EG leads to increased Young’s modulus and tensile strength especially for the composite prepared by WAME. The present work indicates that WAME can promote the dispersion of EG in PVDF matrix without any extra functionalization.  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