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   281397篇
  免费   4544篇
  国内免费   1933篇
电工技术   5780篇
技术理论   5篇
综合类   1220篇
化学工业   44896篇
金属工艺   11870篇
机械仪表   8307篇
建筑科学   7086篇
矿业工程   1712篇
能源动力   6129篇
轻工业   27393篇
水利工程   3086篇
石油天然气   6158篇
武器工业   244篇
无线电   29986篇
一般工业技术   52791篇
冶金工业   52803篇
原子能技术   5979篇
自动化技术   22429篇
  2021年   2612篇
  2019年   2265篇
  2018年   3603篇
  2017年   3570篇
  2016年   3909篇
  2015年   2962篇
  2014年   4819篇
  2013年   12088篇
  2012年   8126篇
  2011年   10886篇
  2010年   8615篇
  2009年   9217篇
  2008年   10073篇
  2007年   10217篇
  2006年   8980篇
  2005年   8015篇
  2004年   7165篇
  2003年   6774篇
  2002年   6749篇
  2001年   6882篇
  2000年   6426篇
  1999年   6405篇
  1998年   14770篇
  1997年   10788篇
  1996年   8222篇
  1995年   6182篇
  1994年   5632篇
  1993年   5521篇
  1992年   4274篇
  1991年   4067篇
  1990年   4136篇
  1989年   4078篇
  1988年   3793篇
  1987年   3264篇
  1986年   3281篇
  1985年   3664篇
  1984年   3515篇
  1983年   3252篇
  1982年   2863篇
  1981年   3091篇
  1980年   2830篇
  1979年   2994篇
  1978年   2878篇
  1977年   3092篇
  1976年   4056篇
  1975年   2577篇
  1974年   2393篇
  1973年   2429篇
  1972年   2065篇
  1971年   1852篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
992.
993.
Adjuvant-induced arthritis is an animal model of chronic inflammatory disease widely used in anti-inflammatory and immunosuppressive drugs testing. When the development and the inhibition of the induced arthritis are measured by the injected paw oedema, it is difficult to delineate the immunological contribution from the persistent non-specific primary section. To study the influence of volume and composition of the injected adjuvant upon the primary non-specific inflammation, we devised a 3X4 factorial experiment on a strain of inbred rats with a low susceptibility to adjuvant-induced arthritis. The injection of mineral oil alone produces a persistent oedema. The injection of mycobacteriae in suspension in saline induces a rapid inflammatory response followed by a fast decrease of the oedema. When complete adjuvant is used, there is always a very strong interaction between the effects of the two components of the adjuvant, i.e. the measured oedemas are much greater than the calculated values, For a given injected volume, the inflammation is maximum when the concentration of mycobacteriae is 2.5 mg/ml. All the rats injected with complete adjuvant present a transient oedema of the non-injected hind paw. This oedema is very small and proportional to the amount of mycobacteria injected.  相似文献   
994.
The electrical conductivity of hot-pressed polycrystalline aluminium nitride doped with oxygen and beryllium was measured as a function of temperature from 800 to 1200° C and over a range of nitrogen partial pressure from 102 to 105 Pa. The effect of beryllium dopant, the independence of conductivity from nitrogen partial pressure, and the observed activation energy suggested extrinsic electronic species or aluminium vacancies as charge carriers. Polarization measurements made with one electrode blocking to ionic species indicated that the aluminium nitride with oxygen impurity was an extrinsic electronic conductor.  相似文献   
995.
The martensitic transformation temperatures and the types of martensitic phases have been determined in a wide concentration range of technological interest for Cu-Al-Ni shape-memory alloys (SMAs) A stability diagram of martensitic phases as a function of alloy concentration has been determined. It is found that when the aluminum content increases, the transformation changes from β 3β3 to β 3γ3, with an intermediate concentration range where both martensites coexist due to a β 3γ3+β3 transformation. On the other hand, an increase of nickel content stabilizes the martensite β3, changing from a mixed β 3γ3 + β3 to a single β 3β3 transformation. Furthermore, linear relationships between M s and Al and Ni concentrations have been obtained for all types of martensitic phases.  相似文献   
996.
The effect of a range of organic additives on the thermal stability of poly(vinyl chloride), both with and without a chloroparaffin extender, was studied using a number of experimental techniques. Of the additives used the best overall balance was provided by pentaerythritol, which increased stability when the extender was present and had no effect when it was absent. The congo red test emerged as the most suitable technique, being consistent and inexpensive and able to screen several additives simultaneously. Isothermal differential thermal analysis correlated with the congo red test but required more expensive equipment, was time-consuming and demanded good mixing of the poly(vinyl chloride) compound to give reproducible results. Thermogravimetry was not sufficiently sensitive and the heat stability test was the least useful of all.  相似文献   
997.
998.
An analysis is made of the fluid flows in a plane slot permeable channel. It is shown that for large numbers R (suction) self-similar solutions exist.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 432–436, September, 1985.  相似文献   
999.
We report on the synthesis results obtained for some compositions in the Co(GaxIn1-x)2S4 family, whose intermediate member CoGaInS4 is shown to display a layered structure. This result is discussed and compared with the literature.  相似文献   
1000.
Thrombin-induced platelet malondialdehyde (MDA) formation and plasma malondialdehyde-like material (MDA-LM) were evaluated in 12 healthy subjects before and after 1 and 7 days from aspirin (1 g) ingestion. 24 hr after aspirin administration, platelet MDA was almost abolished while MDA-LM showed a 23% decrease. Platelet MDA and plasma MDA-LM returned to baseline values 7 days after aspirin ingestion. These data suggest that platelet cyclooxygenase pathway affects only in part plasma MDA-LM. The evaluation of plasma MDA-LM before and after aspirin could be useful for evaluating in vivo platelet cyclooxygenase activation.  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