全文获取类型
收费全文 | 1532篇 |
免费 | 100篇 |
国内免费 | 86篇 |
专业分类
电工技术 | 62篇 |
综合类 | 63篇 |
化学工业 | 77篇 |
金属工艺 | 34篇 |
机械仪表 | 87篇 |
建筑科学 | 145篇 |
矿业工程 | 27篇 |
能源动力 | 44篇 |
轻工业 | 25篇 |
水利工程 | 40篇 |
石油天然气 | 310篇 |
武器工业 | 3篇 |
无线电 | 196篇 |
一般工业技术 | 60篇 |
冶金工业 | 13篇 |
原子能技术 | 132篇 |
自动化技术 | 400篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 19篇 |
2021年 | 35篇 |
2020年 | 27篇 |
2019年 | 22篇 |
2018年 | 34篇 |
2017年 | 44篇 |
2016年 | 65篇 |
2015年 | 50篇 |
2014年 | 90篇 |
2013年 | 88篇 |
2012年 | 82篇 |
2011年 | 128篇 |
2010年 | 98篇 |
2009年 | 116篇 |
2008年 | 83篇 |
2007年 | 83篇 |
2006年 | 84篇 |
2005年 | 80篇 |
2004年 | 53篇 |
2003年 | 42篇 |
2002年 | 55篇 |
2001年 | 36篇 |
2000年 | 30篇 |
1999年 | 49篇 |
1998年 | 36篇 |
1997年 | 37篇 |
1996年 | 34篇 |
1995年 | 23篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 15篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有1718条查询结果,搜索用时 15 毫秒
141.
银额盆地查干凹陷基本生油条件研究 总被引:19,自引:1,他引:18
从有机地球化学方面深入研究了银根-额济纳旗盆地查干凹陷的基本石油地质条件。查干凹陷下白垩统沉积时为一箕状断陷,沉积地层和烃源岩厚度变化大,主要烃源岩发育于下白垩统巴音戈壁组和苏红图组下段,厚约0~2400m。目前烃源岩有机碳含量为0.15%~2.66%,热解生油潜量为0.07~10.74mg/g,氯仿沥青"A"含量多数在0.022‰~3.757‰,总烃含量为0.049‰~2.527‰。有机质丰度变化大,但可溶有机质含量相对较高。有机质主要由无定型草本植物降解和藻类组成(占60%~80%),其中II1型有机质占50%以上,推测原始有机质类型较好。该凹陷地热梯度较高,目前烃源岩镜质组反射率在0.8%~2.0%,处于成熟生油-湿气阶段,饱和烃色谱和色质参数也表明烃源岩已成熟。TTI计算表明其主要烃源岩主要生油期为晚白垩世。综合分析认为下白垩统烃源岩属较好烃源岩,具有一定的生油气潜力。图5表3参5(陈建平摘) 相似文献
142.
王德兵 《重庆科技学院学报(社会科学版)》2001,16(1):4-6
江泽民同志提出的“双思”思想是对邓小平理论的继承和发展,都是指导中国特色社会主义建设发展的理论;二者具有一致性;都强调社会主义制度和共产党的领导是中国发展的前提和基础;经济发展是中心;都强调社会协调发展. 相似文献
143.
144.
145.
研究通信信号源的优化定位问题.随着通信环境的复杂程度不断增加,环境中的随机干扰源会造成通信源信号频谱混合大量非线性噪声,噪声会对信号源频谱形成干扰,噪声频带和定位信号频带叠加时,传统的线性滤波器是在抑制噪声时,有用信号真实性差,检测微弱的通信信号源变得很困难,造成定位误差较大.提出了一种含噪混合通信数据中信号源定位挖掘算法.根据粒子运动状态方程,实现通信信号的滤波处理,为信号源定位提供准确的数据基础.利用通信节点同心圆定位方法,完成信号源定位.实验结果表明,利用改进算法进行通信信号源定位挖掘,能够提高定位的准确性,减小定位误差范围. 相似文献
146.
147.
Abstract Perceived air quality, Sick Building Syndrome (SBS) symptoms and productivity were studied in an existing office in which the air pollution level could be modified by introducing or removing a pollution source. This reversible intervention allowed the space to be classified as either non-low-polluting or low-polluting, as specified in the new European design criteria for the indoor environment CEN CR 1752 (1998). The pollution source was a 20-year-old used carpet which was introduced on a rack behind a screen so that it was invisible to the occupants. Five groups of six female subjects each were exposed to the conditions in the office twice, once with the pollution source present and once with the pollution source absent, each exposure being 265 min in the afternoon, one group at a time. They assessed the perceived air quality and SBS symptoms while performing simulated office work. The subject-rated acceptability of the perceived air quality in the office corresponded to 22% dissatisfied when the pollution source was present, and to 15% dissatisfied when the pollution source was absent. In the former condition there was a significantly increased prevalence of headaches (P= 0.04) and significantly lower levels of reported effort (P=0.02) during the text typing and calculation tasks, both of which required a sustained level of concentration. In the text typing task, subjects worked significantly more slowly when the pollution source was present in the office (P=0.003), typing 6.5% less text than when the pollution source was absent from the office. Reducing the pollution load on indoor air proved to be an effective means of improving the comfort, health and productivity of building occupants. 相似文献
148.
Norimasa Nukaga Hirofumi Ono Takuya Shida Hideaki Machida Toshie Suzuki Hiroshi Funakubo 《组合铁电体》2013,141(1):215-222
SrBi 2 Ta 2 O 9 thin films were prepared by ECR plasma enhanced metalorganic chemical vapor deposition (ECR-MOCVD) with a liquid-delivery system using one cocktail source without an additional solvent. The strontium-tantalum double alkoxide, Sr{Ta[OC 2 H 4 H(CH 3 ) 2 ](OC 2 H 5 ) 5 } 2 , was dissolved in stabilized trimethyl bismuth, Bi(CH 3 ) 3 / dioxane. This source system has been used in a conventional bubbling system. Deposition rate and the composition of the films were strictly controlled by the concentration and the composition of the cocktail source. Therefore, high reproducibility was realized by using this system. The constituent phase of the stoichiometric SBT film as-deposited at 500 C on a (111)Pt/TiO 2 /SiO 2 /Si substrate was a fluorite phase and transformed to the single phase of SBT by the post annealing at 800 C. It showed almost the same ferroelectricity as the stoichiometric composition film. 相似文献
149.
电镀层厚度是电镀工艺的重要指标,其与电镀金属材料、电镀电流强度、电镀时间等有关。本文设计的基于单片机的电镀层厚度记录仪,能准确的记录给定电镀金属材料和恒定电流强度的电镀层金属厚度。讨论电镀层厚度形成因素和记录方法,给出系统硬件设计方案和软件流程图。 相似文献
150.
Anne-Kathrin Kuehnel 《Information & Communications Technology Law》2008,17(2):107-124
Over the past few years, Microsoft has promoted a project called ‘Shared Source Initiative’, which allows certain customers (e.g., research institutions and independent software vendors) access to its source code on a restricted basis. As part of this initiative, Microsoft introduced some licences that appear to give unrestricted access to source code and closely resemble ‘traditional’ Open Source licences. In July 2007, two of these ‘shared source’ licenses (the Microsoft Community Licence and the Microsoft Permissive Licence) were submitted to the Open Source Initiative (OSI) and subsequently approved by the OSI as certified Open Source licences. Thus Microsoft's Shared Source Initiative and its partial embrace of Open Source appear to be a significant step towards closing the ideological rift between developers of proprietary software and the Free/Open Source software movement, and more than just another attempt to appease consumers and/or critics in terms of software transparency. By analysing the ‘evolution’ of Microsoft's Shared Source licences, this article aims to shed some light on the question what is needed for a ‘predator’ (i.e., proprietary, software developer) such as Microsoft to become ‘prey’ (i.e., be part of the Open Source community). This article concludes that, although Microsoft's efforts are to be lauded, it is highly unlikely that the company will embrace fully the Open Source philosophy in the near future. 相似文献