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   461245篇
  免费   5401篇
  国内免费   1211篇
电工技术   8679篇
综合类   579篇
化学工业   70773篇
金属工艺   18055篇
机械仪表   14379篇
建筑科学   10728篇
矿业工程   2320篇
能源动力   10740篇
轻工业   42875篇
水利工程   4668篇
石油天然气   8158篇
武器工业   98篇
无线电   54367篇
一般工业技术   86681篇
冶金工业   86135篇
原子能技术   10184篇
自动化技术   38438篇
  2021年   3760篇
  2019年   3651篇
  2018年   6274篇
  2017年   6276篇
  2016年   6654篇
  2015年   4206篇
  2014年   7188篇
  2013年   19821篇
  2012年   11559篇
  2011年   15732篇
  2010年   12462篇
  2009年   13930篇
  2008年   14853篇
  2007年   14910篇
  2006年   13444篇
  2005年   12058篇
  2004年   11632篇
  2003年   11324篇
  2002年   11072篇
  2001年   10942篇
  2000年   10563篇
  1999年   10569篇
  1998年   24924篇
  1997年   17749篇
  1996年   13926篇
  1995年   10858篇
  1994年   9686篇
  1993年   9459篇
  1992年   7509篇
  1991年   6978篇
  1990年   6995篇
  1989年   6663篇
  1988年   6419篇
  1987年   5612篇
  1986年   5559篇
  1985年   6421篇
  1984年   6085篇
  1983年   5485篇
  1982年   5186篇
  1981年   5376篇
  1980年   5080篇
  1979年   4905篇
  1978年   4798篇
  1977年   5479篇
  1976年   6876篇
  1975年   4338篇
  1974年   4196篇
  1973年   4341篇
  1972年   3549篇
  1971年   3295篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
In order to protect Ni–Cr alloys from high-temperature corrosion, a new heat-resistant glass-ceramic coating was developed with a glass matrix synthesized on the basis of a composite R x O–Al2O3–SiO2–TiO2 (R–Li, Na+, K+, Mg2+, Ca2+, Ba2+) system. The special features of the formation of crystalline phases in the glasses in heat treatment and the optimum regime for the formation of a glass ceramic structure are described.Translated from Steklo i Keramika, No. 3, pp. 30–32, March, 1996.  相似文献   
994.
995.
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   
996.
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   
997.
998.
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   
999.
Zage  W.M. Zage  D.M. 《Software, IEEE》1993,10(4):75-81
Design-quality metrics that are being developed for predicting the potential quality and complexity of the system being developed are discussed. The goal of the metrics is to provide timely design information that can guide a developer in producing a higher quality product. The metrics were tested on projects developed in a university setting with client partners in industry. To further validate the metrics, they were applied to professionally developed systems to test their predictive qualities. The results of applying two design metrics and a composite metric to data from a large-scale industrial project are presented  相似文献   
1000.
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   
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