全文获取类型
收费全文 | 23142篇 |
免费 | 2023篇 |
国内免费 | 938篇 |
学科分类
工业技术 | 26103篇 |
出版年
2024年 | 49篇 |
2023年 | 427篇 |
2022年 | 578篇 |
2021年 | 928篇 |
2020年 | 790篇 |
2019年 | 655篇 |
2018年 | 722篇 |
2017年 | 800篇 |
2016年 | 689篇 |
2015年 | 901篇 |
2014年 | 1210篇 |
2013年 | 1337篇 |
2012年 | 1498篇 |
2011年 | 1593篇 |
2010年 | 1428篇 |
2009年 | 1275篇 |
2008年 | 1268篇 |
2007年 | 1217篇 |
2006年 | 1308篇 |
2005年 | 1214篇 |
2004年 | 728篇 |
2003年 | 620篇 |
2002年 | 564篇 |
2001年 | 510篇 |
2000年 | 512篇 |
1999年 | 645篇 |
1998年 | 506篇 |
1997年 | 415篇 |
1996年 | 373篇 |
1995年 | 339篇 |
1994年 | 258篇 |
1993年 | 161篇 |
1992年 | 137篇 |
1991年 | 116篇 |
1990年 | 92篇 |
1989年 | 71篇 |
1988年 | 55篇 |
1987年 | 28篇 |
1986年 | 32篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
针对能源互联网中的海量分布式设备和电动汽车的需求,利用C#和Java编程语言设计并开发面向能源互联网的能量管理系统。该系统采用典型B/S 架构,以Asp.Net动态网页开发技术和数据库技术为核心,由云端后台算法、云端服务器的MySQL数据库、前端的网页三大部分构成。详细介绍了软件平台的系统框架,分为上下两层。其中,上层为日前-实时协同的多时间尺度能量管理系统模块,下层包含分布式设备协调控制子系统和电动汽车协调控制子系统。最后,通过仿真算例分析,能量管理系统能对海量的分布式设备和电动汽车进行优化调度,验证了该软件的可移植性、有效性和实用性。 相似文献
82.
83.
乙酸与异丁醇酯化反应生产乙酸异丁酯,产生大量含异丁醇的废水,常规生化处理负荷重,浪费资源。采用PDMS复合膜分离回收酯化废水中的异丁醇,考察了异丁醇浓度对PDMS复合膜溶胀度及分离性能的影响,优化渗透汽化过程操作参数,研究了乙酸异丁酯对PDMS复合膜回收异丁醇效果的影响。结果表明,随着异丁醇浓度从1%增大到3%(质量),PDMS复合膜溶胀度先增大后趋于平稳,异丁醇的渗透通量呈增大趋势,分离因子保持在15左右;操作温度从30℃升至60℃时,渗透通量增大,异丁醇的分离因子下降,总表观活化能为33.87 kJ/mol;流速增加,Reynolds数增大,异丁醇渗透通量变化不大,但分离因子略有增大;微量乙酸异丁酯的存在可促进渗透汽化膜回收异丁醇。采用PDMS复合膜分离酯化废水中的异丁醇,回收率大于94.0%,渗余液中异丁醇浓度可降至0.1%(质量)左右。研究结果可为PDMS复合膜处理低浓度有机溶剂废水提供依据。 相似文献
84.
Hanyue Deng Jun Liao Junyu Piao Yong Zhang Simin He Qing Zhou Yi Li Long Zhang 《应用聚合物科学杂志》2020,137(38):49137
Photothermal effect has been widely used in many areas such as cancer therapy, photothermal energy harvesting, and laser ignition. However, exploring reliable and efficient free-standing energy converter for enhancing the photothermal performance is still a challenge. Herein, free-standing membrane based on two-dimensional MXene (Ti3C2) nanosheets and polytetrafluoroethylene (PTFE) was fabricated and characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry, which demonstrated a drastic temperature rise by laser irradiation and was further used as energy converter for enhancing the photothermal performance of laser ignition. Furthermore, the initiating power of the laser initiator can be largely reduced by adding a thin layer of MXene/PTFE membrane above the B/KNO3 cylinder. This work can give great promise for MXene-based membranes as the laser energy converter for reducing the initiating energy and promote the development of laser initiators with low initiating energy. 相似文献
85.
Optically active hybrid particles consisting of chiral organic component and inorganic component integrate the individual advantages of the components in one entity. This article reports a new type of optically active hybrid particles constructed by helical substituted polyacetylene and octavinyl polyhedral oligomeric silsesquioxane (OvPOSS). The hybrid particles were prepared in a two-step process. First, helical substituted polyacetylene with pendent vinyl groups was synthesized and named as macromonomer (MM). Then, hybrid particles were prepared from MM and OvPOSS by free radical suspension polymerization, in which OvPOSS acted simultaneously as comonomer and crosslinking agent. OvPOSS and MM together constituted a crosslinked network and formed spherical, porous hybrid particles. The resulting hybrid particles exhibited the desired optical activity, according to circular dichroism spectroscopy measurement. As an organic/inorganic hybrid molecule itself, OvPOSS moderately improved the thermostability of the organic component and meanwhile increased the porosity of the hybrid particles. It also helped to tune the surface morphology of the hybrid particles. The present study provides a novel class of optically active hybrid particles, and the preparation strategy may further work as a versatile platform for developing novel chiral hybrid materials. 相似文献
86.
Sheng WANG Jun WANG Yingjie XU Weihong ZHANG Jihong ZHU 《Frontiers of Mechanical Engineering》2020,15(2):319-327
Frontiers of Mechanical Engineering - Lattice structures have numerous outstanding characteristics, such as light weight, high strength, excellent shock resistance, and highly efficient heat... 相似文献
87.
Fabrication and performance of the castor oil (CO)-based hyperbranched acrylate (C20AA) UV-curable coatings are highlighted in this work. Herein, C20AA was obtained through a facile reaction of a castor oil-based hyperbranched polyol (C20) with acrylic acid. FT-IR and 1H NMR spectra confirmed the synthesis of the target C20AA. Subsequently, the as-prepared C20AA was employed for crosslinking a commercialized linear polyurethane acrylate (PUA) UV-curable oligomer. Specifically, by varying the content of C20AA over the range of 0, 20, 40, and 60 wt%, a series of UV-curable coatings were prepared and coded as C20AA-0, C20AA-20, C20AA-40, and C20AA-60, respectively, which were further cured under UV irradiation. The effect of C20AA loadings on the UV-curing efficiency and final polymer performance were investigated. Consequently, the tensile strength, Shore D hardness, pencil hardness, gel content, water resistance, and glass-transition temperature of the UV-cured coatings were greatly improved upon the addition of C20AA. Impressively, with the incorporation of 40 wt% C20AA, the resultant UV-cured coating exhibited highest double bond conversion, superior chemical resistance, and good flexibility. Additionally, all of the coatings showed outstanding transparency and good surface microstructures. 相似文献
88.
黄冈大别山世界地质公园拥有4大类12亚类53处地质遗迹资源,为中国自太古代以来的中央造山带形成演化的天然实验室,大别山地区旅游资源丰富。游客量和旅游收入逐年稳步增加,但公园旅游客源地空间的集中程度高,以湖北省武汉市游客为主,外省游客以周边地区居多。游客出游距离以短程为主。旅游业向着多元化和融合创新的全域旅游发展,而地学旅游资源产品单一化对于大众游客缺乏吸引力,以地学旅游为核心的旅游形式和内容需要再进一步开发。通过昂普分析,提出了具体的地学旅游资源开发对策与措施,旅游产业融合产业创新,提高公园旅游一体化服务水平,打造地质与人文一体旅游,发展以世界级地质公园地学旅游为主的多元化旅游活动和旅游产品,打造有效的地学旅游宣传推广体系。公园作为地学和文化综合旅游目的地,应加强区域间旅游合作建设,拓宽公园旅游市场。 相似文献
89.
90.
荷兰建筑师鲁迪·奥恩哈克是高密度可持续设计的理论研究与实践的代表人物之一。文章对鲁迪·奥恩哈克的密度研究方法以及相关的设计实践进行简要介绍,希望可以引起读者的思考。 相似文献