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   36020篇
  免费   2769篇
  国内免费   975篇
电工技术   1581篇
技术理论   4篇
综合类   1615篇
化学工业   6232篇
金属工艺   1568篇
机械仪表   1763篇
建筑科学   1892篇
矿业工程   773篇
能源动力   1241篇
轻工业   2364篇
水利工程   458篇
石油天然气   1060篇
武器工业   152篇
无线电   5571篇
一般工业技术   5207篇
冶金工业   2758篇
原子能技术   426篇
自动化技术   5099篇
  2024年   317篇
  2023年   569篇
  2022年   926篇
  2021年   1288篇
  2020年   1051篇
  2019年   846篇
  2018年   948篇
  2017年   1004篇
  2016年   892篇
  2015年   1116篇
  2014年   1447篇
  2013年   2154篇
  2012年   2031篇
  2011年   2366篇
  2010年   1876篇
  2009年   1912篇
  2008年   1963篇
  2007年   1767篇
  2006年   1601篇
  2005年   1290篇
  2004年   1137篇
  2003年   1203篇
  2002年   1414篇
  2001年   1190篇
  2000年   835篇
  1999年   728篇
  1998年   982篇
  1997年   696篇
  1996年   585篇
  1995年   478篇
  1994年   391篇
  1993年   334篇
  1992年   250篇
  1991年   222篇
  1990年   225篇
  1989年   199篇
  1988年   170篇
  1987年   153篇
  1986年   129篇
  1985年   127篇
  1984年   110篇
  1983年   75篇
  1982年   70篇
  1981年   59篇
  1980年   85篇
  1979年   49篇
  1978年   60篇
  1977年   58篇
  1976年   76篇
  1975年   43篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
石英晶体微天平的研究进展及应用   总被引:1,自引:0,他引:1  
介绍了石英晶体微天平的基本原理和结构,重点介绍了仪器研究进展及应用,包括常规石英晶体微天平(QCM)、耗散型石英晶体微天平(QCM-D)、阵列式石英晶体微天平与电化学石英晶体微天平(EQCM)。  相似文献   
62.
协同优化方法及铰接式自卸车系统设计协同优化模型   总被引:1,自引:1,他引:0  
对协同优化方法的基本思想、计算框架、研究现状及发展进行了分析论述,并将协同优化方法引入到铰接式自卸车(ADT)系统设计中,叙述了对铰接式自卸车进行协同优化的必要性,对ADT系统进行分解,建立协同优化模型,并提出协同优化方法的求解思路。  相似文献   
63.
64.
Mebendazole (MBZ) is a synthetic benzimidazole known for its antiparasitic properties. In recent years, growing evidence showed that MBZ was also used as an anti-tumor agent. However, whether (and to what extent) this drug treatment affected the male reproductive system was not well-understood. In this study, male C57BL/6 mice were injected with 40 mg/kg/day of MBZ. The treatment was for 3 and 7 days. Our results showed that the injected mice exhibited an abnormal spermatogenic phase with a significant decrease in sperm. We further detected microtubule disruption and transient functional destruction of the blood–testes barrier (BTB) in the MBZ-injected mice testes (BTB). Our data confirmed that MBZ suppressed the expression of the BTB junction-associated proteins and disrupted the Sertoli cells’ function in vivo. Moreover, MBZ-treated mice demonstrated an aberrant caspase-3 signalling pathway, which resulted in the apoptosis of the germ cells. Here, we present our data, indicating that MBZ impairs BTB by reducing the expression of the microtubules’ and BTB junction-associated proteins. The last leads to activating the caspase-3 pathway, which triggers extensive germ cell apoptosis.  相似文献   
65.
内啮合渐开线齿轮传动法隙计算的几何分析法   总被引:3,自引:0,他引:3  
通过几何分析的方法,导出了内啮合渐开线齿轮传动中心距略变小时,法向齿侧间隙的计算公式,供齿轮传动设计计算之用。  相似文献   
66.
67.
我国有机食品的现状及发展趋势   总被引:4,自引:0,他引:4  
介绍了有机食品的特点及对人与自然和谐发展的作用,并概述了我国有机食品的发展现状及趋势.  相似文献   
68.
Minoxidil is the most widely used treatment for hair growth, but has been associated with several side effects. In this study, we investigated the effects of heat-killed Enterococcus faecalis EF-2001 on hair loss prevention and regrowth using human dermal papilla cells and male C57BL/6 mice. To examine the effects of EF-2001, we used minoxidil as the positive control. In the in vitro experiments, EF-2001 treatment (75–500 μg/mL) led to the proliferation of human dermal papilla cells in a concentration-dependent manner. In the in vivo experiment, the topical application of 200 µL EF-2001 on the dorsal surface of C57BL/6 male mice led to hair growth. Changes in hair regrowth were examined by visual comparison and hematoxylin and eosin staining of skin sections. We also determined the expression levels of marker genes (Wnt) and growth factors (fibroblast growth factor, insulin growth factor 1, and vascular endothelial growth factor) in the skin tissues of the back of each mouse using a quantitative polymerase chain reaction. EF-2001 accelerated the progression of hair regrowth in mice and promoted hair-follicle conversion from telogen to anagen, likely by increasing the expression levels of growth factors and marker genes.  相似文献   
69.
Z He  J Liu  Y Qiao  CM Li  TT Tan 《Nano letters》2012,12(9):4738-4741
The bioanode is the defining feature of microbial fuel cell (MFC) technology and often limits its performance. In the current work, we report the engineering of a novel hierarchically porous architecture as an efficient bioanode, consisting of biocompatible chitosan and vacuum-stripped graphene (CHI/VSG). With the hierarchical pores and unique VSG, an optimized bioanode delivered a remarkable maximum power density of 1530 mW m(-2) in a mediator-less MFC, 78 times higher than a carbon cloth anode.  相似文献   
70.
In the past decade, capillary electrophoresis has demonstrated increasing utility for the quantitative analysis of single cells. New applications for the analysis of dynamic cellular properties demand sampling methods with sufficient temporal resolution to accurately measure these processes. In particular, intracellular signaling pathways involving many enzymes can be modulated on subsecond time scales. We have developed a technique to rapidly lyse an adherent mammalian cell using a single electrical pulse followed by efficient loading of the cellular contents into a capillary. Microfabricated electrodes were designed to create a maximum voltage drop across the flattened cell's plasma membrane at a minimum interelectrode voltage. The influence of the interelectrode distance, pulse duration, and pulse strength on the rate of cell lysis was determined. The ability to rapidly lyse a cell and collect and separate the cellular contents was demonstrated by loading cells with Oregon Green and two isomers of carboxyfluorescein. All three fluorophores were detected with a separation efficiency comparable to that of standards. Parallel comparison of electrical lysis to that produced by a laser-based lysis system revealed that the sampling efficiencies of the two techniques were comparable. Rapid cell lysis by an electrical pulse may increase the application of capillary electrophoresis to the study of cellular dynamics requiring fast sampling times.  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