全文获取类型
收费全文 | 118139篇 |
免费 | 9796篇 |
国内免费 | 4956篇 |
专业分类
电工技术 | 7072篇 |
技术理论 | 7篇 |
综合类 | 7587篇 |
化学工业 | 20366篇 |
金属工艺 | 6473篇 |
机械仪表 | 7307篇 |
建筑科学 | 9634篇 |
矿业工程 | 3436篇 |
能源动力 | 3503篇 |
轻工业 | 7667篇 |
水利工程 | 2096篇 |
石油天然气 | 7285篇 |
武器工业 | 876篇 |
无线电 | 13402篇 |
一般工业技术 | 14271篇 |
冶金工业 | 5508篇 |
原子能技术 | 1289篇 |
自动化技术 | 15112篇 |
出版年
2024年 | 551篇 |
2023年 | 2026篇 |
2022年 | 3517篇 |
2021年 | 4862篇 |
2020年 | 3728篇 |
2019年 | 3141篇 |
2018年 | 3381篇 |
2017年 | 3916篇 |
2016年 | 3293篇 |
2015年 | 4680篇 |
2014年 | 5699篇 |
2013年 | 6768篇 |
2012年 | 7407篇 |
2011年 | 7959篇 |
2010年 | 6949篇 |
2009年 | 6628篇 |
2008年 | 6420篇 |
2007年 | 6077篇 |
2006年 | 6342篇 |
2005年 | 5512篇 |
2004年 | 3761篇 |
2003年 | 3286篇 |
2002年 | 3077篇 |
2001年 | 2801篇 |
2000年 | 2949篇 |
1999年 | 3159篇 |
1998年 | 2672篇 |
1997年 | 2276篇 |
1996年 | 2097篇 |
1995年 | 1825篇 |
1994年 | 1475篇 |
1993年 | 1056篇 |
1992年 | 860篇 |
1991年 | 678篇 |
1990年 | 492篇 |
1989年 | 437篇 |
1988年 | 353篇 |
1987年 | 245篇 |
1986年 | 167篇 |
1985年 | 97篇 |
1984年 | 65篇 |
1983年 | 49篇 |
1982年 | 63篇 |
1981年 | 39篇 |
1980年 | 35篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
31.
32.
In this article, we present a detailed theoretical analysis and a prototype implementation of a family of cameras designed with the explicit goal of detecting and removing interfering dynamic occluders in real time, during live capture, as opposed to fixing the resulting artifacts a posteriori. Such an early-acquisition approach improves efficiency: more valid samples are acquired faster without worrying about moving occluders. One option for designing a camera to be unaffected by moving occluders is to sample through the occluder, but true x-ray-like vision is technically impractical. Another option is to sample around the occluder using a camera with a large effective aperture, but such an approach requires a bulky acquisition device. Yet another possibility of sampling around an occluder is to rely on second and higher order reflected rays that indirectly sample surfaces not directly visible. However, devising an acquisition device sufficiently sensitive and efficient to capture large environments using reflected rays will remain challenging for the foreseeable future. 相似文献
33.
34.
35.
γ辐照保藏甜杏仁的研究 总被引:4,自引:0,他引:4
介绍了~(60)Co γ射线对甜杏仁杀虫灭菌的研究。结果表明,杀死甜杏仁表面上虫卵的适宜剂量为3.5kGy,常温下可保藏7个月以上,完好率为100%,微生物可减少99%以上。可安全越夏保存。辐照甜杏仁的主要化学成份未发生明显变化。 相似文献
36.
To investigate the association of human leukocyte antigen (HLA) with susceptibility and clinical manifestations of sarcoidosis. Fifty-five patients with sarcoidosis were studied by using allele group specific polymerase chain reaction technique (PCR). Our data show that: (1) the gene frequency of HLA-DR5 is significantly increased in patients with sarcoidosis, but that of HLA-DR7 decreased. (2) Gene frequencies of HLA-DR9 and HLA-DR5 are relatively increased in male patients and in patients with stage I and stage IIa, respectively. The results suggest that HLA-DR gene might contribute to the susceptibility as well as to the difference of clinical manifestations in sarcoidosis. 相似文献
37.
草酸二乙酯气相催化加氢合成乙二醇的研究 总被引:12,自引:0,他引:12
对草酸二乙酯气相催化加氢生成乙二醇反应进行了实验研究。研制了不含铬的铜基催化剂,并考察了催化剂的制备条件对反应结果的影响。结果表明,Cu/SiO_2质量比为0.67,活化温度为350℃时最佳。在上述催化剂制备的基础上,提出了最佳反应条件。 相似文献
38.
The effect of the atomic mobility on a film surface has been studied by using a three-dimensional atomistic thin-film deposition model which simulates three-dimensional thin-film images, surface profiles and cross-sectional area pictures. In addition, quantitative results of surface RMS roughness, average film thickness, atomic coordination number and its distribution, and solid fraction of the deposited thin films, were obtained from the simulations. When the film surface mobility increased from 0.3 to 3.0, RMS roughness decreased from 6.5 to 1.1, solid fraction increased from 0.27 to 0.56 and average film thickness decreased from 40 to 28, due to the reduction of the voids within the film. The full-width half magnitude of the atomic coordination distribution became narrower indicating the increased degree of crystallization. With increase in surface mobility crossing the boundary to 1.5, the film evolved from a porous or loose columnar structure with voids, to a densely packed fibrous grain structure which can be categorized by the zone structure models. 相似文献
39.
40.