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   465098篇
  免费   5159篇
  国内免费   1273篇
电工技术   8583篇
综合类   443篇
化学工业   71376篇
金属工艺   17785篇
机械仪表   13997篇
建筑科学   10989篇
矿业工程   2164篇
能源动力   11790篇
轻工业   42362篇
水利工程   4411篇
石油天然气   7715篇
武器工业   47篇
无线电   55367篇
一般工业技术   88817篇
冶金工业   89249篇
原子能技术   10097篇
自动化技术   36338篇
  2021年   3980篇
  2019年   3674篇
  2018年   6268篇
  2017年   6260篇
  2016年   6646篇
  2015年   4201篇
  2014年   7311篇
  2013年   20594篇
  2012年   11542篇
  2011年   15883篇
  2010年   12705篇
  2009年   14235篇
  2008年   15063篇
  2007年   15034篇
  2006年   13367篇
  2005年   11750篇
  2004年   11338篇
  2003年   11396篇
  2002年   11012篇
  2001年   11303篇
  2000年   10606篇
  1999年   10930篇
  1998年   27403篇
  1997年   19217篇
  1996年   14793篇
  1995年   11285篇
  1994年   10044篇
  1993年   9930篇
  1992年   7314篇
  1991年   6960篇
  1990年   7013篇
  1989年   6692篇
  1988年   6397篇
  1987年   5587篇
  1986年   5555篇
  1985年   6208篇
  1984年   5810篇
  1983年   5430篇
  1982年   5104篇
  1981年   5080篇
  1980年   4911篇
  1979年   4694篇
  1978年   4499篇
  1977年   5250篇
  1976年   7028篇
  1975年   3870篇
  1974年   3748篇
  1973年   3805篇
  1972年   3242篇
  1971年   2887篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
The role of myelin basic protein (MBP) T cell recognition in the induction of experimental allergic encephalomyelitis (EAE) has been well established in mice and rats. A remarkable restriction has been observed in T cell receptor (TCR) genes utilized by encephalitogenic T cell lines (TCLs) specific for immunodominant epitopes in these species. Pathological similarities between this animal model and multiple sclerosis (MS) has led to consider MBP as a major candidate autoantigen in this human disorder. Unlike in inbred strains of animals, the T cell response to MBP in humans is quite heterogenous with regard to fine epitope specificity. The existence of V alpha and/or V beta restriction in MBP-specific T cells, from MS patients and healthy controls, is still a matter of debate. In this study we generated 77 MBP-specific TCLs from nine healthy donors and showed that peptide 7-27 is one of the most frequently recognized epitopes. 37% of all epitope-specific TCLs recognized this peptide and p7-27 specific TCLs were generated from seven out of the nine subjects studied. A high level of in vivo clonal expansion was observed in p7-27-specific TCLs in several subjects, which however is not specific of this epitope since this phenomenon was also observed in p85-104- and 149-162-specific TCLs.  相似文献   
993.
Ferrite is a potential sorbent for flue gases such as CO2, H2S and SO2. This paper discusses the adsorption and decomposition of CO2 into carbon by hydrogen-activated waste ferrites prepared from Berkeley Pit acid mine water (Butte, MT). The decomposition effectiveness of these waste ferrites was studied at 300 °C and compared with the synthetic magnetite obtained from ferrous sulfate solution in our laboratory. The decomposition was measured by two methods: indirectly by measuring the adsorption rate of CO2 and directly by analysing the carbon deposited on the samples. The results indicated that the mixed waste ferrite had good affinity for the adsorption and decomposition. The CO2 decomposition data of both sorbents fitted the first-order reaction kinetics. Even though the surface area of the magnetite was higher than that of waste ferrite, the CO2 decomposition rate of the waste ferrite was estimated to be 2.5 times higher than that of magnetite under identical conditions. The carbon analysis deposited on the sample indicated that the CO2 was 100% decomposed into carbon and other carbon/hydrogen compounds by the waste ferrite, whereas the conversion was 43% by the magnetite. In terms of specific adsorption of carbon, ferrite was three to five times more efficient than magnetite.  相似文献   
994.
A chlorination process for recovering Zr from zircaloy scrap has been studied. Zircaloy chlorination was possible at temperatures as low as 220 °C. The scale microstructure and its effect on the zircaloy reactivity was analysed using Thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS) and scanning electron microscopy (SEM) techniques. A solid-solid phase transformation took place into the oxide scale during the zircaloy chlorination. Zirconium, as ZrCl4(g), was separated from the oxide scale and chlorides of Cr and Fe. The effect of the reaction temperature was also analysed.  相似文献   
995.
996.
997.
Experiments conducted at ground stations of the Quasar satellite communication network using both a null base as well as a base of around 2000 km is described. In experiments with a null base, the time scale transmission error was 1 nsec. Comparison of the results of collocation with data cbtained by the GLONASS system in the course of experiments using a 2100-km base demonstrated a divergence of the results of from 5 to 25 nsec. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 35–38, April, 1996.  相似文献   
998.
The laminar flame theory under the condition of minimum entropy production is presented. The equation of the temperature boundary layer is obtained for Le=0, and its general solution is found. It is shown that the mechanism of laminar flame propagation can be treated from the viewpoint of stationary thermal explosion in a cylindrical vessel of radius 2 as the critical regime in which the burnup is taken into account in an unusual form. Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 22–30, September–October, 1993  相似文献   
999.
Previous research demonstrated a contradiction effect: Although text currently being processed was locally coherent, readers were aware of inconsistencies between a protagonist's actions and characteristics of the protagonists that were described earlier in the text and subsequently backgrounded. In the present experiments, not only the critical characteristics but also the protagonist were backgrounded. When the protagonist was reintroduced into the narrative in the context of carrying out an inconsistent action, the contradiction effect again occurred. In Exps 1–3, we examined the effects of several variables on the onset of the effect. In Exp 4, we presented probes at various points in the passage with results that supported the conclusion that the critical characteristics had been backgrounded before the sentence that contradicted them. Results are discussed in terms of several recent models in which currently active representational elements serve as retrieval cues for other inactive, but highly related, elements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
1000.
The equivalent series resistance and reactance of the electrode-electrolyte interface impedance have both been used to detect the onset of signal amplitude induced nonlinearity. Using a theoretical model, it is shown that the choice of the most sensitive indicator depends on the phase angle of the “polarization” impedance and on the applied frequency  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