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   168424篇
  免费   1268篇
  国内免费   193篇
电工技术   2553篇
综合类   119篇
化学工业   26611篇
金属工艺   9471篇
机械仪表   5715篇
建筑科学   3008篇
矿业工程   1887篇
能源动力   2703篇
轻工业   8818篇
水利工程   2729篇
石油天然气   8692篇
武器工业   12篇
无线电   14492篇
一般工业技术   38250篇
冶金工业   27797篇
原子能技术   6933篇
自动化技术   10095篇
  2018年   2978篇
  2017年   3092篇
  2016年   3345篇
  2015年   1672篇
  2014年   2954篇
  2013年   6338篇
  2012年   4311篇
  2011年   5397篇
  2010年   4420篇
  2009年   4894篇
  2008年   4940篇
  2007年   4868篇
  2006年   4141篇
  2005年   3819篇
  2004年   3634篇
  2003年   3520篇
  2002年   3450篇
  2001年   3463篇
  2000年   3361篇
  1999年   3212篇
  1998年   7019篇
  1997年   5149篇
  1996年   3822篇
  1995年   2916篇
  1994年   2593篇
  1993年   2720篇
  1992年   2254篇
  1991年   2304篇
  1990年   2409篇
  1989年   2315篇
  1988年   2313篇
  1987年   2190篇
  1986年   2246篇
  1985年   2292篇
  1984年   2206篇
  1983年   2135篇
  1982年   1980篇
  1981年   2193篇
  1980年   2053篇
  1979年   2269篇
  1978年   2431篇
  1977年   2430篇
  1976年   3095篇
  1975年   2244篇
  1974年   2307篇
  1973年   2342篇
  1972年   2155篇
  1971年   1911篇
  1970年   1701篇
  1969年   1632篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
The behavior of a superelastic Cu?14.2% Al?4%Ni single crystal in the case of high reversible strains under a longitudinal bending force was investigated. The effect of strain confinement along the crystal length was revealed and studied. The highest reversible strains (up to 10%) were shown to be confined within the central part of the bent crystal.  相似文献   
52.
53.
Technical Physics Letters - A new method for epitaxial growth of cadmium sulfide (CdS) films in the metastable cubic phase by atomic-layer deposition on silicon substrates with a buffer layer of...  相似文献   
54.
55.
The microstructure and properties of the functional coatings formed by impact friction processing of product surfaces with a flexible tool are studied. It is established that the processing produces a hard nanostructured surface layer with fragments up to 0.13 µm in size, as it is achieved by severe plastic deformation.  相似文献   
56.
Design and operation modes of double-junction monolithic lattice-matched solar cells based on the ZnSiP2/Si system of materials have been calculated. The effect of the photoactive region thickness and minority carrier lifetime in ZnSiP2 layers on the efficiency of conversion of the incident solar light energy into electrical power was determined. It is shown that solar cells based on ZnSiP2/Si heterostructures can provide efficiencies of 28.8% at AM1.5D, 100 mW/cm2, and 33.3% at AM1.5D, 200 W/cm2.  相似文献   
57.
Temperature history can have a significant effect on the strength of water-saturated chalk.In this study,hydrostatic stress cycles are applied to understand the mechanical response of chalk samples exposed to temperature cycling between each stress cycle,compared to the samples tested at a constant temperature.The total accumulated strain during a stress cycle and the irreversible strain are reported.Chalk samples from Kansas(USA)and Mons(Belgium),with different degrees of induration(i.e.amount of contact cementation),were used.The samples were saturated with equilibrated water(polar)and nonpolar Isopar H oil to quantify water weakening.All samples tested during 10 stress cycles with varying temperature(i.e.temperature cycled in between each stress cycle)accumulated more strain than those tested at constant temperatures.All the stress cycles were performed at 30℃.The two chalk types behaved similarly when saturated with Isopar H oil,but differently when saturated with water.When saturated with water,the stronger Kansas chalk accumulated more total strain and more irreversible strain within each stress cycle than the weaker Mons chalk.  相似文献   
58.
59.
Pokutnyi  S. I.  Dzyuba  V. P.  Amosov  A. V. 《Semiconductors》2019,53(16):2045-2048
Semiconductors - The optical properties of dielectric nanostructures strongly depend on dielectric nanoparticles (NP) polarizability which can take the high values even interacting with...  相似文献   
60.
Electrospark treatment of OT4-1 titanium alloy was performed sequentially with a STIM-20N hard-alloy electrode (TiC–20% Ni) and carbon-containing material (graphite and carbon-based composite materials). Kinetics of the mass transfer of the hard-alloy electrode was studied. The cathode mass loss during the first minute of the treatment was established. The kinetics results were processed using the methods of mathematical statistics. The erosion resistance of the applied carbon-containing materials was determined. Phase composition and relief of the coatings formed were analyzed. It was found that the application of the carbon-containing material increases the content of refractory phases in the coatings. Increase in the time of the treatment using the carbon-containing materials decreases the roughness of the coatings.  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