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   69401篇
  免费   5638篇
  国内免费   2976篇
电工技术   3890篇
技术理论   10篇
综合类   4535篇
化学工业   11512篇
金属工艺   3582篇
机械仪表   3886篇
建筑科学   5375篇
矿业工程   1824篇
能源动力   1915篇
轻工业   5306篇
水利工程   1288篇
石油天然气   3662篇
武器工业   526篇
无线电   8235篇
一般工业技术   8509篇
冶金工业   4175篇
原子能技术   715篇
自动化技术   9070篇
  2024年   310篇
  2023年   1175篇
  2022年   2085篇
  2021年   2875篇
  2020年   2245篇
  2019年   1784篇
  2018年   2045篇
  2017年   2132篇
  2016年   2084篇
  2015年   2675篇
  2014年   3337篇
  2013年   3889篇
  2012年   4298篇
  2011年   4704篇
  2010年   3880篇
  2009年   3705篇
  2008年   3679篇
  2007年   3440篇
  2006年   3276篇
  2005年   2855篇
  2004年   2133篇
  2003年   1891篇
  2002年   1729篇
  2001年   1546篇
  2000年   1687篇
  1999年   2025篇
  1998年   1912篇
  1997年   1501篇
  1996年   1467篇
  1995年   1199篇
  1994年   1031篇
  1993年   733篇
  1992年   551篇
  1991年   403篇
  1990年   348篇
  1989年   324篇
  1988年   235篇
  1987年   167篇
  1986年   128篇
  1985年   95篇
  1984年   61篇
  1983年   44篇
  1982年   60篇
  1981年   38篇
  1980年   47篇
  1979年   13篇
  1977年   39篇
  1976年   62篇
  1974年   11篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
连铸钢液温度变化规律及控制的研究   总被引:2,自引:0,他引:2  
鲁开嶷 《冶金能源》1993,12(3):16-21
  相似文献   
32.
OBJECTIVE: To study the correlation of development and survival with amplification of c-erbB2 oncogene in endometrial carcinoma. METHODS: The amplification and expression of c-erbB2 oncogene were determined from formalin-fixed, paraffin-embedded tissues of 25 normal, 31 hyperplastic, and 72 malignant samples of the endometrium in 128 patients, using differential polymerase chain reaction (DPCR) and an immunohistochemical technique. RESULTS: Amplified c-erbB2 (2 to 12 copies) were found in two of 25 (8.0%) normal, 15 of 31 (48.4%) hyperplastic, and 45 of 72 (62.5%) malignant samples. When the results of DPCR were compared with those of the immunohistochemical method, the negative findings concide well with one another, i.e., nonamplification was associated with the absence of immunoreactivity. It was noted that the amplified c-erbB2 was found more significantly in complex and a typical hyperplasias than in simple hyperplasias. The high-level c-erbB2 amplification (at least five copies) was significantly correlated with the histological grade of endometrial carcinoma and vascular or lymphatic invasion. No correlation was seen between c-erbB2 amplification and overall survival in the present group of patients. CONCLUSIONS: The amplified c-erbB2 may play a potential role in the early development of some endometrial carcinomas. The high-level c-erbB2 amplification may identify a subset of aggressive endometrial carcinoma that involves vascular or lymphatic invasiveness and poor cell differentiation playing the role of a marker for clinical prognosis.  相似文献   
33.
本文介绍了一种基于公共存储器进行数据交换的高速数字图象处理系统.给出了公共存储器的设计,描述了处理器对公共存储器的进程同步控制.  相似文献   
34.
A new method for integrated design of passive and active elements is presented. Rather than the existing qualitative selection of parameters for passive elements, a quantitative approach is proposed that finds optimal active and passive parameters with respect to an H2/H performance requirement. This new approach automatically yields passive designs when the given performance limits are high enough and active (hybrid) designs when the given performance constraints are stringent. Furthermore, our algorithm finds the special performance requirement (the peak of the frequency response) that cannot be satisfied by any passive design. Hence this article shows how to determine when control is required rather than assuming a priori that it is or is not required. A simple design method given herein yields either passive, active, or hybrid designs depending only on the level of the performance constraints that are specified in the statement of the problem.  相似文献   
35.
We describe a novel "see-through" indium-tin-oxide contact on the n-side of a high power unstable resonator semiconductor laser (URSL) that allows direct observation of the cavity during high power operation. Under optimized annealing conditions this transparent ITO contact has a low enough specific contact resistivity to permit normal high power CW operation of the URSL and allows the observation of filamentation. This contact scheme is applicable to a wide range of semiconductor lasers and is especially appropriate for high power devices. The same structure can also be used to obtain a 2-D thermal map of the laser cavity.  相似文献   
36.
37.
观赏草在庭园中的设计与应用   总被引:2,自引:0,他引:2  
绿意 《园林》2005,(12):20-21
观赏草以其灵动的景观特质,草类特有的自然色调,飘逸的质感越来越受到设计师们的青睐,用于焦点、绿蒿、花镜、镶边均有不凡的表现,虽为草类,却有着灌木的功能。  相似文献   
38.
本文考察了ρ-混合噪声中ρ-混合随机信号的 Min-Max 检测问题.首先,将[5]中(?)-混合条件减弱为ρ-混合相依条件;其次,去掉了[5]中式(5)(?)r_n<∞的限制条件;第三,将[5]中常值的弱信号拓广到具有ρ-混合相依的随机信号,故本文改进了[5]中结果.  相似文献   
39.
40.
Microprocessor and other lC performance continues to improve at historic rates, with no visible end in sight for the next 10 years. However, we are starting to encounter a power wall. This is true for high-performance components as well as for low-power chips with a very limited energy budget offered by batteries. We need to find ways to manage power and energy consumption on all fronts-technology, design, and architecture-without compromising performance. Otherwise, we may face discontinuation of Moore's law for the semiconductor industry in the near future. This would be triggered not by any difficulty in the scaling of process technology but by formidable barriers posed by packaging and cooling, inefficacy of power delivery, and energy constraints dictated by battery technology, which is advancing at a very lukewarm pace  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