全文获取类型
收费全文 | 20662篇 |
免费 | 2502篇 |
国内免费 | 1263篇 |
专业分类
电工技术 | 1494篇 |
技术理论 | 1篇 |
综合类 | 1533篇 |
化学工业 | 2998篇 |
金属工艺 | 1357篇 |
机械仪表 | 1431篇 |
建筑科学 | 1463篇 |
矿业工程 | 659篇 |
能源动力 | 688篇 |
轻工业 | 1706篇 |
水利工程 | 471篇 |
石油天然气 | 792篇 |
武器工业 | 221篇 |
无线电 | 2852篇 |
一般工业技术 | 2524篇 |
冶金工业 | 808篇 |
原子能技术 | 299篇 |
自动化技术 | 3130篇 |
出版年
2024年 | 143篇 |
2023年 | 410篇 |
2022年 | 812篇 |
2021年 | 1259篇 |
2020年 | 899篇 |
2019年 | 670篇 |
2018年 | 768篇 |
2017年 | 852篇 |
2016年 | 764篇 |
2015年 | 1052篇 |
2014年 | 1422篇 |
2013年 | 1511篇 |
2012年 | 1717篇 |
2011年 | 1761篇 |
2010年 | 1425篇 |
2009年 | 1320篇 |
2008年 | 1400篇 |
2007年 | 1224篇 |
2006年 | 1064篇 |
2005年 | 867篇 |
2004年 | 587篇 |
2003年 | 433篇 |
2002年 | 394篇 |
2001年 | 330篇 |
2000年 | 261篇 |
1999年 | 195篇 |
1998年 | 176篇 |
1997年 | 135篇 |
1996年 | 101篇 |
1995年 | 97篇 |
1994年 | 104篇 |
1993年 | 70篇 |
1992年 | 41篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 21篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1970年 | 4篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
用高能球磨采用两种方案制备了FeCo MnO体系,并用X射线衍射和振动样品磁强计对其结构和磁性质做了分析.发现采用直接氧化Mn而得到MnO的方法,所得体系的MnO较纯;而通过分解MnCO3得到MnO的体系,MnO纯度较低,有较多Mn3O4杂质,两种方法制备的FeCo MnO体系的矫顽力和剩磁比都比单纯FeCo体系的增加很多,且前一种方法比后一种方法制备的FeCo MnO体系的矫顽力和剩磁比较大.然后研究了球磨时间及退火处理对FeCo MnO体系矫顽力及剩磁比的影响,发现球磨时间为120h体系的矫顽力和剩磁比最大;经过退火处理后,体系的矫顽力和剩磁比都有较大幅度的增加. 相似文献
82.
83.
一种可靠多播认证方案及其C语言实现 总被引:1,自引:0,他引:1
贺堃 《信息安全与通信保密》2007,(6):226-227
传统的认证技术对于多播认证并不适用,因为多播认证有它自身的特殊要求。论文介绍了两种针对多播认证特点的解决方案,并结合两种方案的特点阐述了一种改进的适合可靠多播的认证方案,最后给出了C语言的实现。 相似文献
84.
The possible hypocholesterolaemic properties of milk and fermented milk products have been investigated in groups of albino rats given a basal diet, basal diet plus cholesterol, and basal diet plus cholesterol together with whole milk or standard or bifidus yogurt. The yogurts were fortified with skim milk powder, condensed whey or lactose-hydrolysed condensed whey. After 30 d, triacylglycerols, total cholesterol, HDL-cholesterol and LDL-cholesterol were measured in serum. Whole milk and ordinary yogurt had no hypocholesterolaemic effect, but standard yogurt containing lactose-hydrolysed condensed whey and all bifidus yogurts lowered serum cholesterol. In general, yogurts changed HDL-cholesterol little, but tended to raise triacylglycerols. There was marked lowering of LDL-cholesterol in rats given either type of yogurt fortified with whey proteins. This study has demonstrated in a rat model that bifidus yogurts and yogurts fortified with whey proteins can reduce total and LDL-cholesterol, and suggests that if they have the same effect in human subjects they have potential value in cholesterol-lowering diets. 相似文献
85.
An advanced integral-type pressurized water reactor (IPWR) with a maximum thermal power of 65 MW has been developed at the Korea Atomic Energy Research Institute (KAERI). This 65 MW IPWR enhances the safety and reliability by adopting inherent safety design characteristics and an advanced passive design feature. 相似文献
86.
In a complex social, political, economic, technological, and/or environmental context, corporate, military, government, and other organizations are often faced with collective decision-making situations. The rationale for group decision exercises is that the judgment of many will usually prove superior to the judgment of one. However, it has been shown that collective decision exercises are often highly dependent on matters of perspective, values and opinion, all of which - being essentially subjective in nature - are beyond the reach of existing formal decision technology. Furthermore, it can be expected that many collective decision exercises - particularly those of strategic import - will not lend themselves to the quantitative analysis instruments that have long dominated the management and decision science repertoire. This does not, however, mean that they must remain entirely and forever outside the bounds of scientific rationality. The ordering protocols which are currently available do not have enough technical mechanics to be relied upon to bring us to any satisfying resolution of a priori disputation. Hence, we propose an a priori ordering reference model that might support consensus-building in a multiple stakeholders context. In order to detect whether the subjective arguments are products of proper reasons or merely instances of raw rhetoric and to suggest how any logical or syntactical flaws might best be repaired, we propose logical ordering facilities and protocols for integrating procedural and instrumental provisions for a group-decision process with two lines of technical innovation: the superimpositional ordering function and the logical ordering support facilities. 相似文献
87.
Real-time homogenous translucent material editing 总被引:4,自引:0,他引:4
This paper presents a novel method for real-time homogenous translucent material editing under fixed illumination. We consider the complete analytic BSSRDF model proposed by Jensen et al. [ [JMLH01] ], including both multiple scattering and single scattering. Our method allows the user to adjust the analytic parameters of BSSRDF and provides high-quality, real-time rendering feedback. Inspired by recently developed Precomputed Radiance Transfer (PRT) techniques, we approximate both the multiple scattering diffuse reflectance function and the single scattering exponential attenuation function in the analytic model using basis functions, so that re-computing the outgoing radiance at each vertex as parameters change reduces to simple dot products. In addition, using a non-uniform piecewise polynomial basis, we are able to achieve smaller approximation error than using bases adopted in previous PRT-based works, such as spherical harmonics and wavelets. Using hardware acceleration, we demonstrate that our system generates images comparable to [ [JMLH01] ]at real-time frame-rates. 相似文献
88.
首先对3G室内分布系统特点进行介绍,然后对其设计过程中的关键问题进行分析,并给出在后续网络优化过程中的常见问题和相应解决方案。 相似文献
89.
提取系统的冲击响应函数(impulse response function,IRF)是测量雷达系统性能指标的前提,IRF来自理想点目标的雷达图像。对于低频超宽带合成孔径雷达(ultra wide band synthetic aperture radar,UWB SAR),参考点目标的电磁散射特性是频率和方位角的函数,不满足理想点目标的散射特性要求。本文从IRF的定义出发,结合低频UWBSAR系统处理模型,利用二维数字聚焦方法消除杂波的影响,同时利用低频电磁散射数值建模的方法计算参考点目标的电磁散射特性,最后给出了计算系统IRF的方法。 相似文献
90.