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   68998篇
  免费   8849篇
  国内免费   3564篇
电工技术   5926篇
技术理论   9篇
综合类   5252篇
化学工业   10108篇
金属工艺   4237篇
机械仪表   4536篇
建筑科学   5649篇
矿业工程   2457篇
能源动力   2244篇
轻工业   4505篇
水利工程   1652篇
石油天然气   3495篇
武器工业   807篇
无线电   8361篇
一般工业技术   7842篇
冶金工业   2902篇
原子能技术   1066篇
自动化技术   10363篇
  2025年   28篇
  2024年   1276篇
  2023年   1713篇
  2022年   2951篇
  2021年   3816篇
  2020年   2957篇
  2019年   2165篇
  2018年   2480篇
  2017年   2693篇
  2016年   2496篇
  2015年   3403篇
  2014年   4058篇
  2013年   4758篇
  2012年   5291篇
  2011年   5604篇
  2010年   4782篇
  2009年   4447篇
  2008年   4300篇
  2007年   3907篇
  2006年   3654篇
  2005年   3022篇
  2004年   2065篇
  2003年   1490篇
  2002年   1348篇
  2001年   1072篇
  2000年   1029篇
  1999年   927篇
  1998年   701篇
  1997年   567篇
  1996年   581篇
  1995年   413篇
  1994年   343篇
  1993年   247篇
  1992年   220篇
  1991年   124篇
  1990年   107篇
  1989年   80篇
  1988年   78篇
  1987年   44篇
  1986年   34篇
  1985年   30篇
  1984年   15篇
  1983年   12篇
  1982年   17篇
  1981年   10篇
  1980年   12篇
  1979年   7篇
  1976年   9篇
  1959年   9篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Soluble solids content (SSC) is an important quality trait of wax gourd, but reports about its regulatory genes are scarce. In this study, the SSC regulatory gene BhSSC2.1 in wax gourd was mined via quantitative trait locus (QTL) mapping based on high-density genetic mapping containing 12 linkage groups (LG) and bulked segregant analysis (BSA)-seq. QTL mapping and BSA-seq revealed for the first time that the SSC QTL (107.658–108.176 cM) of wax gourd was on Chr2 (LG2). The interpretable phenotypic variation rate and maximum LOD were 16.033% and 6.454, respectively. The QTL interval contained 13 genes. Real-time fluorescence quantitative expression analysis, functional annotation, and sequence analysis suggested that Bch02G016960, named BhSSC2.1, was a candidate regulatory gene of the SSC in wax gourd. Functional annotation of this gene showed that it codes for a NADP-dependent malic enzyme. According to BhSSC2.1 sequence variation, an InDel marker was developed for molecular marker-assisted breeding of wax gourd. This study will lay the foundation for future studies regarding breeding and understanding genetic mechanisms of wax gourd.  相似文献   
152.
In this paper, we investigated the electrical properties of the Metal-oxide-semiconductor gate stack of Ti/Al2O3/InP under different annealing conditions. A min...  相似文献   
153.
车灯座注塑模具设计   总被引:1,自引:1,他引:0  
通过对车灯座注塑模具的设计,阐述了模具浇注系统的设计方法,旨在降低模具的复杂程度和制造成本;详细介绍了组合式型腔、型芯的结构设计及模具的制造方法。  相似文献   
154.
The mechanical properties of hot rolled strip are the key index of product quality,and the soft sensing of them is an important decision basis for the control a...  相似文献   
155.
随着储能设备和电力驱动产品的激增,特别是电动汽车的大规模推广应用,全固态电池被认为是最有可能解决电动设备日益严峻的安全问题和高能量密度需求的策略之一.本文报道了一种Al4B2O9纳米棒改性的聚环氧乙烷(PEO)基固体聚合物电解质(ASPE),其具有高离子电导率、宽电化学窗口、良好的机械性能和阻燃性能.具体来说,因为Al...  相似文献   
156.
Dear editor, The basic concept of observability is used to express the possibility to recover the state from measurements in modern control theory [1-3].It is a...  相似文献   
157.
在分析了地物杂波回波特性的基础上,首先设计了动目标显示雷达模拟器的地物回波形成单元的组成方框图.结合方框图,得出了形成地物回波的基本要素:同步计数电路、计数比较电路、多普勒调制电路.最后结合雷达自身的特点,设计了动目标显示雷达模拟训练器地物回波形成单元的基本组成电路,并将其与雷达联机,取得良好的效果.  相似文献   
158.
Design of floating offshore wind turbines(FOWTs)needs reliable and innovative technologies to overcome the challenges on how to better predict the dynamic respo...  相似文献   
159.
In optical metrological protocols to measure physical quantities, it is, in principle, always beneficial to increase photon number n to improve measurement prec...  相似文献   
160.
Xu  Peng  Ni  YiKun  Liu  JingLong  Zhang  WeiRong  Liu  SiJian  Wang  LiZhen  Fan  YuBo 《中国科学:技术科学(英文版)》2021,64(5):1101-1106
Woodpeckers can withstand a fierce impact during pecking. Previous studies have focused on the biomechanical analysis of the pecking process, the properties of the beak and hyoid bone of woodpecker; however, the biological characteristics of the woodpecker brain are also important in resisting impact injuries. We employed impact experiments and biological analysis in normal and injured brains to reveal the impact-resistant biological characteristics of woodpecker brains, as well as the impact energy's biological effects on the woodpecker brain. The hoopoe, which has a similar size but only a slight pecking behavior, was selected as the control group to compare brain morphology and neuronal cells differences in normal brains between woodpecker and hoopoe by sectioning and staining. A loading device was designed to conduct a quantifiable impact energy to the woodpeckers' head. Four groups of woodpeckers were impacted with the same energy on the forehead, beak, tempus and occiput,respectively. Biological changes in the injured brains were evaluated by Nissl staining and enzyme-linked immunosorbent assay.The results showed that:(1) woodpeckers had a larger cerebellum and a higher density of Nissl bodies than hoopoe;(2) Nissl apoptosis appeared in the brain samples after the forehead and the occiput impact experiments, but no obvious Nissl body apoptosis was observed after impact on the tempus and the beak;(3) β-amyloid protein accumulated in the normal status woodpecker brain. This study reveals that: woodpecker brain morphology is well-adapted to impact, woodpecker heads display location-dependent protective performance, with beak and tempus regions having a better protective performance than the forehead and occiput, Nissl apoptosis appears in injured woodpecker brains, and that the accumulation of β-amyloid protein does not show a direct relationship with the injury state of woodpecker's brain tissue in our study.  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