全文获取类型
收费全文 | 86596篇 |
免费 | 6387篇 |
国内免费 | 2924篇 |
专业分类
电工技术 | 4347篇 |
技术理论 | 9篇 |
综合类 | 4649篇 |
化学工业 | 15514篇 |
金属工艺 | 4445篇 |
机械仪表 | 5234篇 |
建筑科学 | 7028篇 |
矿业工程 | 1985篇 |
能源动力 | 2480篇 |
轻工业 | 4902篇 |
水利工程 | 1447篇 |
石油天然气 | 4539篇 |
武器工业 | 488篇 |
无线电 | 10444篇 |
一般工业技术 | 11300篇 |
冶金工业 | 4899篇 |
原子能技术 | 831篇 |
自动化技术 | 11366篇 |
出版年
2024年 | 324篇 |
2023年 | 1314篇 |
2022年 | 2280篇 |
2021年 | 3099篇 |
2020年 | 2336篇 |
2019年 | 2028篇 |
2018年 | 2255篇 |
2017年 | 2518篇 |
2016年 | 2359篇 |
2015年 | 2942篇 |
2014年 | 4018篇 |
2013年 | 5072篇 |
2012年 | 5243篇 |
2011年 | 5519篇 |
2010年 | 4899篇 |
2009年 | 4716篇 |
2008年 | 4466篇 |
2007年 | 4403篇 |
2006年 | 4648篇 |
2005年 | 4133篇 |
2004年 | 2784篇 |
2003年 | 2499篇 |
2002年 | 2192篇 |
2001年 | 2019篇 |
2000年 | 2282篇 |
1999年 | 2566篇 |
1998年 | 2435篇 |
1997年 | 1917篇 |
1996年 | 1783篇 |
1995年 | 1462篇 |
1994年 | 1232篇 |
1993年 | 889篇 |
1992年 | 660篇 |
1991年 | 545篇 |
1990年 | 411篇 |
1989年 | 373篇 |
1988年 | 324篇 |
1987年 | 180篇 |
1986年 | 166篇 |
1985年 | 122篇 |
1984年 | 98篇 |
1983年 | 63篇 |
1982年 | 60篇 |
1981年 | 55篇 |
1980年 | 38篇 |
1979年 | 32篇 |
1978年 | 16篇 |
1977年 | 36篇 |
1976年 | 18篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
新会计准则对会计准则质量的影响 总被引:4,自引:0,他引:4
年初,国家财政部发布了新的会计准则,这是中国会计准则建设史上的重大事件。新会计准则体现出会计准则质量的几个重要标准,提高了中国会计准则的质量。同时,分析新会计准则质量方面仍存在的一些不足。 相似文献
82.
83.
催化精馏合成N-异丙基苯胺 总被引:3,自引:2,他引:1
在Joback基团贡献法估算反应的G ibbs函数的基础上,得到了异丙醇与苯胺合成N-异丙基苯胺的平衡常数与反应温度的关系式。研究了回流比、异丙醇与苯胺的摩尔比、塔釜操作温度、苯胺进料口位置距塔顶的距离对异丙醇与苯胺催化精馏合成N-异丙基苯胺的影响,确定了适宜的工艺条件:回流比2.5~3.5、异丙醇与苯胺的摩尔比1.5、塔釜操作温度223℃、苯胺进料口位置距塔顶300~400mm。在优化条件下,苯胺的转化率可达到99%,N-异丙基苯胺的选择性可达到99.5%,N-异丙基苯胺的质量分数可稳定在98.8%以上。 相似文献
84.
Analysis and architecture design of variable block-size motion estimation for H.264/AVC 总被引:1,自引:0,他引:1
Ching-Yeh Chen Shao-Yi Chien Yu-Wen Huang Tung-Chien Chen Tu-Chih Wang Liang-Gee Chen 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(3):578-593
Variable block-size motion estimation (VBSME) has become an important video coding technique, but it increases the difficulty of hardware design. In this paper, we use inter-/intra-level classification and various data flows to analyze the impact of supporting VBSME in different hardware architectures. Furthermore, we propose two hardware architectures that can support traditional fixed block-size motion estimation as well as VBSME with less chip area overhead compared to previous approaches. By broadcasting reference pixel rows and propagating partial sums of absolute differences (SADs), the first design has the fewer reference pixel registers and a shorter critical path. The second design utilizes a two-dimensional distortion array and one adder tree with the reference buffer that can maximize the data reuse between successive searching candidates. The first design is suitable for low resolution or a small search range, and the second design has advantages of supporting a high degree of parallelism and VBSME. Finally, we propose an eight-parallel SAD tree with a shared reference buffer for H.264/AVC integer motion estimation (IME). Its processing ability is eight times of the single SAD tree, but the reference buffer size is only doubled. Moreover, the most critical issue of H.264 IME, which is huge memory bandwidth, is overcome. We are able to save 99.9% off-chip memory bandwidth and 99.22% on-chip memory bandwidth. We demonstrate a 720-p, 30-fps solution at 108 MHz with 330.2k gate count and 208k bits on-chip memory. 相似文献
85.
Six genotypes of sweet potato commercially available in Taiwan, including TNG57, TNG66, TNG68, TYY1, RP and WP, were used as samples in this study of the effects of steaming and kneading with pre-steaming treatments on the antioxidant components and antioxidant properties of methanolic extracts. Steam treatment increased the total phenols contents of all genotypes (2–13 times), flavonoids content of RP (1.3 times) and anthocyanins contents of RP and WP (5–6 times). Steam treatment also increased the reducing power and scavenging DPPH radical effect of sweet potato flours. For the methanolic extracts of steamed and kneaded flours, reducing powers were 0.02–1.70 at 5.0 mg ml−1 and the scavenging effects on DPPH radicals were 19–92% at 2.5 mg ml−1. Both showed the order of RP > WP > TYY1 and TNG66 > TNG57 and TNG68. However, the chelating effect of the six genotypes at 1.0 mg ml−1 ranged from 50% to 73%. Contents of total phenols, flavonoids, and anthocyanins of sweet potato flours were significantly positively correlated with the reducing power and scavenging DPPH radical effects. After steaming and kneading treatments, RP showed the highest increase in the contents of total phenols, flavonoids and anthocyanins among the six genotypes studied. 相似文献
86.
实验室的质量监督(上) 总被引:4,自引:0,他引:4
质量监督是实验室保持人员能力,进行自我完善,日常渐进的重要手段,是持续改进的重要组成部分,也是实验室管理工作的难点,本文给出质量监督的目的、对象、方法、记录等. 相似文献
87.
88.
Szu-Wei Huang Jenn-Gwo Hwu 《Electron Devices, IEEE Transactions on》2003,50(7):1658-1664
A cost-effective technique was introduced to prepare ultrathin aluminum oxide (Al/sub 2/O/sub 3/) gate dielectrics with equivalent oxide thickness (EOT) down to 14 /spl Aring/. Al/sub 2/O/sub 3/ was fabricated by anodic oxidation (anodization) of ultrathin Al films at room temperature in deionized water and then furnace annealed at 650/spl deg/C in N/sub 2/ ambient. Both dc and dac (dc superimposed with ac) anodization techniques were investigated. Effective dielectric constant of k/spl sim/7.5 and leakage current of 2-3 orders of magnitude lower than SiO/sub 2/ are observed. The conduction mechanism in Al/sub 2/O/sub 3/ gate stack is shown to be Fowler-Nordheim (F-N) tunneling. Saturated current behavior in the inversion region of MOS capacitor is observed. It is found that the saturation current is sensitive to interface state capacitance and can be used as an efficient way to evaluate the Al/sub 2/O/sub 3/ gate stack/Si-substrate interfacial property. An optimal process control for preparing Al/sub 2/O/sub 3/ gate dielectrics with minimized interface state capacitance via monitoring the inversion saturation current is demonstrated. 相似文献
89.
90.
分析了设备对PCB电镀过程中孔中镀液更新之影响,为有效地利用设备条件改善孔中镀液的更新提供了一些方法及理论数据。 相似文献