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   2948篇
  免费   98篇
  国内免费   39篇
电工技术   92篇
综合类   39篇
化学工业   743篇
金属工艺   67篇
机械仪表   134篇
建筑科学   113篇
矿业工程   23篇
能源动力   90篇
轻工业   273篇
水利工程   26篇
石油天然气   10篇
武器工业   2篇
无线电   257篇
一般工业技术   409篇
冶金工业   250篇
原子能技术   44篇
自动化技术   513篇
  2024年   2篇
  2023年   12篇
  2022年   49篇
  2021年   65篇
  2020年   28篇
  2019年   56篇
  2018年   67篇
  2017年   46篇
  2016年   59篇
  2015年   62篇
  2014年   81篇
  2013年   167篇
  2012年   138篇
  2011年   207篇
  2010年   192篇
  2009年   202篇
  2008年   212篇
  2007年   177篇
  2006年   141篇
  2005年   164篇
  2004年   94篇
  2003年   101篇
  2002年   100篇
  2001年   61篇
  2000年   54篇
  1999年   41篇
  1998年   53篇
  1997年   45篇
  1996年   45篇
  1995年   33篇
  1994年   31篇
  1993年   44篇
  1992年   31篇
  1991年   21篇
  1990年   23篇
  1989年   14篇
  1988年   21篇
  1987年   19篇
  1986年   9篇
  1985年   22篇
  1984年   16篇
  1983年   19篇
  1982年   8篇
  1981年   17篇
  1980年   11篇
  1979年   6篇
  1977年   5篇
  1976年   4篇
  1974年   2篇
  1973年   3篇
排序方式: 共有3085条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
We have developed a unique device, a dynamic diamond anvil cell (dDAC), which repetitively applies a time-dependent load/pressure profile to a sample. This capability allows studies of the kinetics of phase transitions and metastable phases at compression (strain) rates of up to 500 GPa/s (approximately 0.16 s(-1) for a metal). Our approach adapts electromechanical piezoelectric actuators to a conventional diamond anvil cell design, which enables precise specification and control of a time-dependent applied load/pressure. Existing DAC instrumentation and experimental techniques are easily adapted to the dDAC to measure the properties of a sample under the varying load/pressure conditions. This capability addresses the sparsely studied regime of dynamic phenomena between static research (diamond anvil cells and large volume presses) and dynamic shock-driven experiments (gas guns, explosive, and laser shock). We present an overview of a variety of experimental measurements that can be made with this device.  相似文献   
15.

Obituaries

Grigorii Valentinovich Samsonov  相似文献   
16.
In cancer cells, cell-surface sialylation is altered, including a change in oligo/polysialic acid (oligo/polySia) structures. Since they are unique and rarely expressed in normal cells, oligo/polySia structures may serve as promising novel biomarkers and targets for therapies. For the diagnosis and treatment of the disease, a precise understanding of the oligo/polySia structures in cancer cells is necessary. In this study, flow cytometric analysis and gene expression datasets were obtained from sixteen different cancer cell lines. These datasets demonstrated the ability to predict glycan structures and their sialylation status. Our results also revealed that sialylation patterns are unique to each cancer cell line. Thus, we can suggest promising combinations of antibody and cancer cell for glycan prediction. However, the precise prediction of minor glycans need to be further explored.  相似文献   
17.
根据等效焓降法在热力系统计算时的特点,推导了循环函数法在回热系统中的局部定量计算方法,导出了回热系统局部定量计算的几个重要结论.最后,通过实例计算对所得结论进行了验证.验证结果表明,该方法在回热系统局部定量计算过程中具有简洁、准确、概念清晰等特点,适合推广.  相似文献   
18.
In the present report, we examine whether or not there are similar and different characteristics between biological molecular particles and non-living ones such as quark and leptons. While the Newton, Schrodinger, and Boltzmann equations and elementary particle theories describe only a narrow range of scales, the present statistic-fluid dynamic theory having only one arbitrary constant synthetically reveals masses as well as frequencies of various particles of quarks, leptons, W–Z bosons, Higgs boson, plank mass, hadrons, atoms, biological molecules, liquid droplets, living cells, biological organs, and stars. This is possible because each flexible particle is commonly generated by a mode in which a larger particle breaks up into two smaller ones through a gourd shape (gourdron) with two lumps rather than strings. These masses and frequencies dominated by the super-magic numbers, including the asymmetrically golden and symmetrically yamato ratios, can be derived by a quasi-stability principle weaker than neutral stability. The primordial mechanism underlying various types of symmetry breaking and the natural four forces including gravity is also revealed by this theory.  相似文献   
19.
20.
Effects of Bi doping in PbTe liquid-phase epitaxial layers grown by the temperature difference method under controlled vapor pressure (TDM-CVP) are investigated. For Bi concentrations in the solution, xBi, lower than 0.2 at.%, an excess deep-donor level (activation energy Ed≈0.03–0.04 eV) appears, and Hall mobility is low. In contrast, for xBi>0.2 at.%, Hall mobility becomes very high, while carrier concentration is in the range of 1017 cm−3. Inductive coupled plasma (ICP) emission analysis shows that, for xBi=1 at.%, Bi concentration in the epitaxial layer is as high as NBi=2.3–2.7 × 1019 cm−3. These results indicate that Bi behaves not only as a donor but also as an acceptor, and the nearest neighbor or very near donor-acceptor (D-A) pairs are formed, so that strong self-compensation of Bi takes place. Carrier concentration for highly Bi-doped layers shows a minimum at a Te vapor pressure of 2.2 × 10−5 torr for growth temperature 470°C, which is coincident with that of the undoped PbTe.  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