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   554233篇
  免费   94661篇
  国内免费   57729篇
电工技术   48630篇
技术理论   58篇
综合类   43541篇
化学工业   85713篇
金属工艺   42925篇
机械仪表   31004篇
建筑科学   41586篇
矿业工程   24688篇
能源动力   19276篇
轻工业   43084篇
水利工程   13912篇
石油天然气   34910篇
武器工业   6925篇
无线电   69959篇
一般工业技术   72583篇
冶金工业   26114篇
原子能技术   5171篇
自动化技术   96544篇
  2024年   3546篇
  2023年   9802篇
  2022年   15400篇
  2021年   20421篇
  2020年   19615篇
  2019年   26126篇
  2018年   28959篇
  2017年   31217篇
  2016年   29909篇
  2015年   32986篇
  2014年   35955篇
  2013年   38975篇
  2012年   40000篇
  2011年   38908篇
  2010年   34213篇
  2009年   29990篇
  2008年   27895篇
  2007年   26063篇
  2006年   25680篇
  2005年   22713篇
  2004年   18881篇
  2003年   16165篇
  2002年   14986篇
  2001年   13530篇
  2000年   13406篇
  1999年   14353篇
  1998年   12239篇
  1997年   10395篇
  1996年   9872篇
  1995年   8749篇
  1994年   7268篇
  1993年   5736篇
  1992年   5025篇
  1991年   3779篇
  1990年   2952篇
  1989年   2616篇
  1988年   2064篇
  1987年   978篇
  1986年   790篇
  1985年   534篇
  1984年   368篇
  1983年   288篇
  1982年   344篇
  1981年   269篇
  1980年   228篇
  1976年   286篇
  1975年   224篇
  1972年   251篇
  1971年   138篇
  1960年   206篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Multimedia Tools and Applications - With the rapid development of the Internet, the color digital image copyright protection is facing severe challenges. Simultaneously, the color digital images...  相似文献   
72.
以欧美标准中的单包容与全包容低温储罐中的钢制储罐抗震设计方法为分析对象,从抗震设防水准与目标、抗震设计反应谱以及抗震设计准则如地震作用调整系数、阻尼比、载荷组合、抗震许用应力、抗倾覆与滑移、晃动波高等方面进行分析对比,为欧美低温储罐抗震设计方法的工程应用提供参考。为实现抗震设防目标以及与该国(区域)建筑抗震以及荷载标准体系协调,欧美低温储罐抗震各设计准则均存在一定的差异,工程设计时应合理应用以避免安全隐患。  相似文献   
73.
根据玉米需肥特性设计氮磷钾比例,制备了含中微量元素的大量元素水溶肥料,产品氮、磷、钾比例为2∶1∶4,属于高钾中氮低磷型.在河北省安平县前子文村和浙江省新昌县孟家塘村玉米上开展了叶面喷施试验.结果表明:玉米生物学性能得到改善,玉米产量、出籽率、百粒重与容重得到提高;与空白对照相比,平均增产率为5.45%,平均纯增收896.40元/公顷,平均产投比为5.43∶1.  相似文献   
74.
Nowadays, oil pollution has become more serious, which causes great threats both to the ecological environment and human life. In this study, a novel type of multifunctional deacetylated cellulose acetate/polyurethane (d-MCA:MTPU) composite nanofiber membranes for oil/water separation are successfully fabricated by electrospinning, which show super-amphiphilicity in air, super-hydrophilicity in oil, and oleophobicity in water. All the d-MCA:MTPU composite nanofiber membranes with different mass ratios can be used as water-removing, oil-removing, and emulsion separation substance only by gravity driving force. The highest separation flux for water and oil reaches up to 37 000 and 74 000 L m−2 h−1, respectively, and all the separation efficiencies are more than 99%. They have outstanding comprehensive mechanics performance, which can be controlled by simply adjusting the mass ratios. They show excellent antifouling and self-cleaning ability, endowing powerful cyclic stability and reusability. Those results show that d-MCA:MTPU composite nanofiber membranes have great application prospects in oil/water separation.  相似文献   
75.
针对目前集成电路版图分析与设计课程存在教学方法老化、教学模式形式化等问题,本文以OBE-CDIO教育理念为指导,对”集成电路版图分析与设计”课程的课程教学模式、课程设计、项目式教学方式和课程考核方式等方面的改革进行有益的探索与实践。将工程教学认证中对学生的专业毕业要求作为制定教学目标的依据,将BB网络平台、ISO9001等现代化教学资源和质量标准融入课堂教学,采用OBE-CDIO能力教学理念指导课程设计,实现教学环节与考核环节的科学化与多元化,通过引入课程思政激发学生学习热情,树立社会主义核心价值观,全面地培养学生的综合版图分析与设计能力和素养。  相似文献   
76.
Crosslinking of polyolefin elastomer (POE, ENGAGE™ 8480) with Dicumyl Peroxide (DCP) can have effects on its crystallization dynamics, crystal structure, and properties. The POE crosslinked uniformly has significantly lower crystalline ability than the one with only amorphous phase crosslinked, which, in turn, has weaker crystalline ability than neat POE. The crystallinity and melting point depend on how the POE is crosslinked. The neat POE and POE crosslinked in amorphous phase only, are investigated with DSC and in-situ tensile/synchrotron radiation (WAXD/SAXS). In situ tensile/synchrotron X-ray during a uniaxial stretching process indicates that severe crystal fragmentation is observed at a strain around 45%, and with further increase in strain. The stress in the crosslinked POE is significantly larger than neat POE. For both samples, crystal orientation increases sharply within the strain range up to 88% where orientation-induced new crystals aligned in stretching direction are observed. The long period increases more in stretching direction for the crosslinked POE, consistent with larger stress in this sample, and the stress difference is more pronounced at large strains (27.3 vs. 10.9 MPa at a strain 435%). Permanent set of the crosslinked POE is smaller, consistent with less oriented crystals observed after the test for permanent set.  相似文献   
77.
Parkinson’s disease (PD) is a neurodegenerative disorder that affects 1% of the population over the age of 60. Diabetes Mellitus (DM) is a metabolic disorder that affects approximately 25% of adults over the age of 60. Recent studies showed that DM increases the risk of developing PD. The link between DM and PD has been discussed in the literature in relation to different mechanisms including mitochondrial dysfunction, oxidative stress, and protein aggregation. In this paper, we review the common microRNA (miRNA) biomarkers of both diseases. miRNAs play an important role in cell differentiation, development, the regulation of the cell cycle, and apoptosis. They are also involved in the pathology of many diseases. miRNAs can mediate the insulin pathway and glucose absorption. miRNAs can also regulate PD-related genes. Therefore, exploring the common miRNA biomarkers of both PD and DM can shed a light on how these two diseases are correlated, and targeting miRNAs is a potential therapeutic opportunity for both diseases.  相似文献   
78.
Novel TiC-based composites were synthesized by reactive hot-pressing at 1800 °C for 1 h with ZrB2 addition as a sintering aid for the first time. The effects of ZrB2 contents on the phase composition, microstructure evolution, and mechanical properties were reported. Based on the reaction and solid solution coupling effects between ZrB2 and TiC, the product ZrC may be partially or completely dissolved into the TiC matrix, and then phase separation within the miscibility gap is observed to form lamellar nanostructured ZrC-rich (Zr, Ti)C. The TiC-10 mol.% ZrB2 (starting batch composition) exhibits good comprehensive mechanical properties of hardness 27.7 ± 1.3 GPa, flexural strength 659 ± 48 MPa, and fracture toughness of 6.5 ± 0.6 MPa m1/2, respectively, which reach or exceed most TiC-based composites using ceramics as sintering aids in the previous reports.  相似文献   
79.
The degradation behavior of implants is significantly important for bone repair. However, it is still unprocurable to spatiotemporally regulate the degradation of the implants to match bone ingrowth. In this paper, a magneto-controlled biodegradation model is established to explore the degradation behavior of magnetic scaffolds in a magnetothermal microenvironment generated by an alternating magnetic field (AMF). The results demonstrate that the scaffolds can be heated by magnetic nanoparticles (NPs) under AMF, which dramatically accelerated scaffold degradation. Especially, magnetic NPs modified by oleic acid with a better interface compatibility exhibit a greater heating efficiency to further facilitate the degradation. Furthermore, the molecular dynamics simulations reveal that the enhanced motion correlation between magnetic NPs and polymer matrix can accelerate the energy transfer. As a proof-of-concept, the feasibility of magneto-controlled degradation for implants is demonstrated, and an optimizing strategy for better heating efficiency of nanomaterials is provided, which may have great instructive significance for clinical medicine.  相似文献   
80.
张向举  韩广欣  姚超 《河南化工》2021,38(10):23-25
锂离子电池负极浆料中添加N-甲基吡咯烷酮(NMP),在极片加热干燥时不能完全除去.残留的NMP吸附在石墨表面,使得SEI膜与石墨结合不牢固.研究了其对电池性能的影响,结果显示,在电池的循环过程中,SEI膜逐渐脱落,导致电池循环寿命缩短,但对电池的容量、内阻、倍率、存储等初期性能不影响.  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