全文获取类型
收费全文 | 23916篇 |
免费 | 1944篇 |
国内免费 | 1060篇 |
专业分类
电工技术 | 1133篇 |
技术理论 | 8篇 |
综合类 | 2357篇 |
化学工业 | 3776篇 |
金属工艺 | 587篇 |
机械仪表 | 742篇 |
建筑科学 | 4071篇 |
矿业工程 | 1544篇 |
能源动力 | 1029篇 |
轻工业 | 2055篇 |
水利工程 | 1454篇 |
石油天然气 | 1322篇 |
武器工业 | 128篇 |
无线电 | 667篇 |
一般工业技术 | 2179篇 |
冶金工业 | 2080篇 |
原子能技术 | 240篇 |
自动化技术 | 1548篇 |
出版年
2024年 | 80篇 |
2023年 | 304篇 |
2022年 | 753篇 |
2021年 | 945篇 |
2020年 | 816篇 |
2019年 | 687篇 |
2018年 | 612篇 |
2017年 | 624篇 |
2016年 | 765篇 |
2015年 | 824篇 |
2014年 | 1746篇 |
2013年 | 1653篇 |
2012年 | 1774篇 |
2011年 | 1865篇 |
2010年 | 1459篇 |
2009年 | 1436篇 |
2008年 | 1165篇 |
2007年 | 1553篇 |
2006年 | 1385篇 |
2005年 | 1174篇 |
2004年 | 1006篇 |
2003年 | 803篇 |
2002年 | 730篇 |
2001年 | 551篇 |
2000年 | 424篇 |
1999年 | 349篇 |
1998年 | 244篇 |
1997年 | 222篇 |
1996年 | 135篇 |
1995年 | 137篇 |
1994年 | 102篇 |
1993年 | 70篇 |
1992年 | 78篇 |
1991年 | 50篇 |
1990年 | 48篇 |
1989年 | 39篇 |
1988年 | 31篇 |
1987年 | 22篇 |
1986年 | 31篇 |
1985年 | 21篇 |
1984年 | 17篇 |
1983年 | 24篇 |
1982年 | 30篇 |
1980年 | 8篇 |
1966年 | 10篇 |
1964年 | 15篇 |
1960年 | 8篇 |
1957年 | 10篇 |
1956年 | 7篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
燕麦为西藏自治区典型牧草之一,由于种植区地域辽阔,灌溉试验结果受限,西藏燕麦主要种植区的灌溉定额尚不明确。本文在西藏燕麦主要种植区内选取28个典型站点进行资料收集,遵循农业气候相似原则进行区域划分,基于水量平衡法揭示了西藏燕麦主要种植区灌溉定额的空间分布特征,并根据统计学原理分析了其影响因素。研究表明:燕麦主要种植区的灌溉定额呈由西藏中部至东部呈现先递增后递减的趋势,50%水文年下的燕麦灌溉定额在56~265 mm之间变化。降雨量是影响研究区内燕麦灌溉定额的主要因素(R2为0.515),ET0次之(R2为0.152);其它气象因素中,日照时数对研究区燕麦灌溉定额影响较大(R2为0.462),且呈正相关关系;相对湿度对燕麦灌溉定额影响较小。西藏燕麦主要种植区的灌溉定额及其空间分布可为西藏自治区灌溉用水管理提供支撑。 相似文献
2.
3.
4.
Raquel Cano Jos L. Prez Liss Angarita Dvila ngel Ortega Yosselin Gmez Nereida Josefina Valero-Cedeo Heliana Parra Alexander Manzano Teresa Isabel Vliz Castro María P. Díaz Albornoz Gabriel Cano Joselyn Rojas-Quintero Maricarmen Chacín Valmore Bermúdez 《International journal of molecular sciences》2021,22(9)
Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disorder, affecting around 25% of the population worldwide. It is a complex disease spectrum, closely linked with other conditions such as obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome, which may increase liver-related mortality. In light of this, numerous efforts have been carried out in recent years in order to clarify its pathogenesis and create new prevention strategies. Currently, the essential role of environmental pollutants in NAFLD development is recognized. Particularly, endocrine-disrupting chemicals (EDCs) have a notable influence. EDCs can be classified as natural (phytoestrogens, genistein, and coumestrol) or synthetic, and the latter ones can be further subdivided into industrial (dioxins, polychlorinated biphenyls, and alkylphenols), agricultural (pesticides, insecticides, herbicides, and fungicides), residential (phthalates, polybrominated biphenyls, and bisphenol A), and pharmaceutical (parabens). Several experimental models have proposed a mechanism involving this group of substances with the disruption of hepatic metabolism, which promotes NAFLD. These include an imbalance between lipid influx/efflux in the liver, mitochondrial dysfunction, liver inflammation, and epigenetic reprogramming. It can be concluded that exposure to EDCs might play a crucial role in NAFLD initiation and evolution. However, further investigations supporting these effects in humans are required. 相似文献
5.
茯砖茶发酵、干燥过程中,烘房内温湿度稳定性和能源系统低能耗是保证茯砖茶品质与成本的重要因素。本文采用TRNSYS仿真与实验研究相结合的方法,对咸阳某茯砖茶厂实际使用的空气源热泵系统进行建模,通过研究各季节典型代表月烘房温湿度的波动情况,确定该空气源热泵系统在全年的运行状态是否满足工艺要求,在此基础上,对比了该系统在全年可运行季节代表月与该生产厂房早期使用的燃气锅炉系统的能耗仿真结果,对空气源热泵系统的节能与环保特性进行研究。结果表明:由于夏季送风质量流量过大且室外空气含湿量较高,7月烘房温湿度不满足工艺要求。热泵系统在1、4、10月的总标煤消耗量的平均值是锅炉系统的44.42%,平均CO2、SO2、NOx排放量分别为锅炉系统的34.13%、44.1%、40.60%。在茯砖茶发酵、干燥的过程中,相比于燃气锅炉系统,空气源热泵系统具有更好的节能与环保特性。 相似文献
6.
7.
Karolina Storesund Francine Amon Anne Steen‐Hansen Shayesteh Haghighatpanah Ida Larsson 《火与材料》2021,45(1):181-190
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
8.
9.
10.
Ergonomic interventions may potentially reduce MSDs, but the context of industries (barriers, ever-changing situations, dialogue processes) might play a significant role in the success of interventions. This study evaluates the effectiveness of ergonomic interventions including engineering/technical and organizational interventions, and the involvement of the stakeholders in reducing musculoskeletal risk factors/symptoms. A pre-post-test experimental study in non-randomized groups was performed over three years in a sector of a truck assembly plant. The mean age of the operators in the sector for the initial and second assessment time was 42.0 (±7.6) years and 39.0 (±8.7), respectively. The mean length of work experience in the current job was 15.2 (±7.2) years and 13.9 (±7.3) for the initial and second assessment times, respectively. Five engineering ergonomic solutions and organizational interventions were implemented after a comprehensive ergonomic analysis. The organizational interventions consisted mostly of transferring and redistributing the tasks, i.e., ergonomically balancing and redesigning of the workstations. Before performing the interventions, the findings of the ergonomic study were presented at several meetings to encourage the involvement of the stakeholders (including managers, engineers, and operators) in the interventions. This study showed that a combination of ergonomic measures—engineering and organizational interventions—could reduce physical workloads. Musculoskeletal symptoms decreased after interventions although the difference was not significant. 相似文献