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   11185篇
  免费   981篇
  国内免费   447篇
电工技术   518篇
综合类   669篇
化学工业   1941篇
金属工艺   573篇
机械仪表   785篇
建筑科学   886篇
矿业工程   300篇
能源动力   339篇
轻工业   1044篇
水利工程   217篇
石油天然气   395篇
武器工业   53篇
无线电   1309篇
一般工业技术   1377篇
冶金工业   587篇
原子能技术   176篇
自动化技术   1444篇
  2024年   46篇
  2023年   197篇
  2022年   403篇
  2021年   467篇
  2020年   378篇
  2019年   283篇
  2018年   346篇
  2017年   379篇
  2016年   371篇
  2015年   479篇
  2014年   626篇
  2013年   741篇
  2012年   748篇
  2011年   802篇
  2010年   650篇
  2009年   705篇
  2008年   628篇
  2007年   563篇
  2006年   589篇
  2005年   463篇
  2004年   312篇
  2003年   307篇
  2002年   331篇
  2001年   255篇
  2000年   225篇
  1999年   229篇
  1998年   203篇
  1997年   127篇
  1996年   149篇
  1995年   107篇
  1994年   87篇
  1993年   66篇
  1992年   56篇
  1991年   52篇
  1990年   41篇
  1989年   32篇
  1988年   22篇
  1987年   17篇
  1986年   14篇
  1985年   13篇
  1984年   8篇
  1983年   10篇
  1981年   10篇
  1980年   9篇
  1979年   5篇
  1978年   6篇
  1977年   12篇
  1976年   14篇
  1973年   4篇
  1969年   4篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Polycystic ovary syndrome (PCOS) is the most common endocrine and metabolic disorder in reproductive-aged women, and it typically involves elevated androgen levels. Recently, it has been reported that human bone marrow mesenchymal stem cells (hBM-MSCs) can regulate androgen synthesis pathways. However, the details of the mechanism are still unclear. hBM-MSC-derived secreted factors (the secretome) are promising sources of cell-based therapy as they consist of various types of proteins. It is thus important to know which proteins interact with disease-implicated biomolecules. This work aimed to investigate which secretome components contain the key factor that inhibits testosterone synthesis. In this study, we fractionated hBM-MSC-conditioned media into three fractions based on their molecular weights and found that, of the three fractions, one had the ability to inhibit the androgen-producing genes efficiently. We also analyzed the components of this fraction and established a protein profile of the hBM-MSC secretome, which was shown to inhibit androgen synthesis. Our study describes a set of protein components present in the hBM-MSC secretome that can be used therapeutically to treat PCOS by regulating androgen production for the first time.  相似文献   
52.
Adiponectin administration to pregnant mice decreases nutrient transport and fetal growth. An adiponectin deficiency, on the other hand, as seen in obese women during pregnancy, alters fetal growth; however, the mechanism is unclear. To determine the role of adiponectin on placenta function and fetal growth, we used adiponectin knockout, adiponectin heterozygote that displays reduced adiponectin levels, and wild-type mice on a control diet or high fat/high sucrose (HF/HS) diet. Triglycerides (TGs) in the serum, liver, and placenta were measured using colorimetric assays. Gene expression was measured using quantitative RT-PCR. Adiponectin levels did not affect fetal weight, but it reduced adiponectin levels, increased fetal serum and placenta TG content. Wildtype dams on a HF/HS diet protected the fetuses from fatty acid overload as judged by increased liver TGs in dams and normal serum and liver TG levels in fetuses, while low adiponectin was associated with increased fetal liver TGs. Low maternal adiponectin increased the expression of genes involved in fatty acid transport; Lpl and Cd36 in the placenta. Adiponectin deficiency does not affect fetal growth but induces placental dysfunction and increases fetal TG load, which is enhanced with obesity. This could lead to imprinting effects on the fetus and the development of metabolic dysfunction in the offspring.  相似文献   
53.
Mitochondria play a crucial role in cell physiology and pathophysiology. In this context, mitochondrial dynamics and, subsequently, mitochondrial ultrastructure have increasingly become hot topics in modern research, with a focus on mitochondrial fission and fusion. Thus, the dynamics of mitochondria in several diseases have been intensively investigated, especially with a view to developing new promising treatment options. However, the majority of recent studies are performed in highly energy-dependent tissues, such as cardiac, hepatic, and neuronal tissues. In contrast, publications on mitochondrial dynamics from the orthopedic or trauma fields are quite rare, even if there are common cellular mechanisms in cardiovascular and bone tissue, especially regarding bone infection. The present report summarizes the spectrum of mitochondrial alterations in the cardiovascular system and compares it to the state of knowledge in the musculoskeletal system. The present paper summarizes recent knowledge regarding mitochondrial dynamics and gives a short, but not exhaustive, overview of its regulation via fission and fusion. Furthermore, the article highlights hypoxia and its accompanying increased mitochondrial fission as a possible link between cardiac ischemia and inflammatory diseases of the bone, such as osteomyelitis. This opens new innovative perspectives not only for the understanding of cellular pathomechanisms in osteomyelitis but also for potential new treatment options.  相似文献   
54.
健美操教学中美感教育的频数统计分析   总被引:1,自引:0,他引:1  
吕默 《电子科技》2011,24(10):140-142
健美操的产生与发展是一个渐进的过程,它起源于人类对人体健与美的追求,健美操的发展史与人类审美观的形成是密切相关的,而美感是健美操教学和研究中与美的本质紧密相关的一个重要的问题。文中从美感的定义出发,从美学、教育方法论等多个角度详细阐述了健美操教学中的美感教育,并进行了丰富的实践统计。  相似文献   
55.
This study describes the development process of Kor-Factor, which is a novel composite evaluation index that was developed to promote Korean domestic academic journals. As more data accumulate, the Kor-Factor’s optimization process was modified in an attempt to address possible drawbacks of the original form; the result is presented in this study. This study compares Kor-Factor with the Impact Factor, which is the most well-known single element evaluation index. We found that Kor-Factor demonstrates a better power of differentiation and a greater capacity to reflect the reputability of key journals. The modified Kor-Factor, which has been developed through an optimization process, reveals a greater power of differentiation than the original Kor-Factor; however, the modified version has less capacity to reflect reputability. The evaluation elements of the modified Kor-Factor are better and are more evenly reflected on the index value than those of the original version. Finally, we propose the establishment of an appropriate data measurement period for the actual application of the index.  相似文献   
56.
The synthetic indium-bearing zinc ferrite (IBZF) was activated mechanically using a tumbling mill under different rotation speeds, milling times, media fillings, and ball-to-material ratios. Subsequently, the changes in the physicochemical properties and leaching behavior of IBZF induced by mechanical activation were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR), M?ssbauer spectrometry, particle size analysis, and leaching tests in sulfuric acid. The results showed that different milling conditions could form different particle size distribution, morphologies, and crystal structures, which influenced indium extraction differently. In addition, the indium extractions from various activated samples were related closely to the changes of physicochemical properties induced by mechanical activation. The strengthening effect of mechanical activation in IBZF decomposition lies mainly in the damage of crystal structure besides the decrease of the particle size because the indium-leaching efficiencies increased significantly with the increase of the damage of the crystal structure when the particle size is kept constant.  相似文献   
57.
凝汽器管板和水室的防腐   总被引:1,自引:0,他引:1  
根据凝汽器水室和管板的腐蚀机理,提出用环氧煤沥青做防腐涂层。本文介绍了环氧煤沥青的主要成分、性能以及凝汽器用环氧煤沥青防腐的施工工艺及涂层质量的检测方法等。  相似文献   
58.
以上海市政工程设计研究总院为例,论述了与时俱进,增强科学发展需要解决的认识问题;分析了转变发展方式,谋求更大发展空间的工作重点;提出了加大政策引导和资源整合力度,抓好基层党建工作和企业文化建设的措施。  相似文献   
59.
为了在测量中高效使用频谱分析仪,需要对其进行优化设置。主要阐述了如何在测量过程中根据测试目的优化设置频谱分析仪相关参数和状态,以获得高的测量精度、快的测量速度和大的动态范围从而达到优化使用频谱分析仪、提高测量效能的目的。  相似文献   
60.
本文结合大型水电厂发电机局部放电在线监测的需要,研发了一套基于中性点耦合法的大型发电机局部放电在线监测系统,采用功能强大的计算机主流技术,与高性能模块化硬件结合而成,通过现场实测,验证了该系统的有效性。  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