全文获取类型
收费全文 | 118165篇 |
免费 | 9786篇 |
国内免费 | 4965篇 |
专业分类
电工技术 | 7072篇 |
技术理论 | 7篇 |
综合类 | 7584篇 |
化学工业 | 20363篇 |
金属工艺 | 6469篇 |
机械仪表 | 7307篇 |
建筑科学 | 9633篇 |
矿业工程 | 3436篇 |
能源动力 | 3504篇 |
轻工业 | 7676篇 |
水利工程 | 2096篇 |
石油天然气 | 7284篇 |
武器工业 | 876篇 |
无线电 | 13409篇 |
一般工业技术 | 14283篇 |
冶金工业 | 5507篇 |
原子能技术 | 1289篇 |
自动化技术 | 15121篇 |
出版年
2024年 | 552篇 |
2023年 | 2026篇 |
2022年 | 3518篇 |
2021年 | 4864篇 |
2020年 | 3728篇 |
2019年 | 3142篇 |
2018年 | 3382篇 |
2017年 | 3916篇 |
2016年 | 3294篇 |
2015年 | 4682篇 |
2014年 | 5700篇 |
2013年 | 6773篇 |
2012年 | 7410篇 |
2011年 | 7962篇 |
2010年 | 6950篇 |
2009年 | 6631篇 |
2008年 | 6420篇 |
2007年 | 6078篇 |
2006年 | 6341篇 |
2005年 | 5513篇 |
2004年 | 3766篇 |
2003年 | 3286篇 |
2002年 | 3078篇 |
2001年 | 2801篇 |
2000年 | 2948篇 |
1999年 | 3159篇 |
1998年 | 2671篇 |
1997年 | 2274篇 |
1996年 | 2099篇 |
1995年 | 1825篇 |
1994年 | 1473篇 |
1993年 | 1056篇 |
1992年 | 860篇 |
1991年 | 677篇 |
1990年 | 491篇 |
1989年 | 436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 15 毫秒
31.
32.
研究了具有低表面能的氟聚合物聚四氟乙烯(PTFE),经60Coγ射线辐照后表面状态的变化,以及其对液体介质蒸馏水的润湿性。较详细地论述了辐照后表面粗糙度、结晶度以及表面化学基因等不同因素对PTFE表面润湿性的影响。通过对PTFE及其表面的红外、X光衍射,表面粗糙度的分析,弄清了辐照后PTFE表面化学基团的改变对有机氟聚合物表加的润湿性影响很大,而粗糙度和结晶度的变化对润湿性影响较小。 相似文献
33.
An analytical expression for both band-to-band and band-trap-band indirect tunnelings is used to study the gate-induced drain leakage (GIDL) current of MOSFETs measured before and after hot-carrier stress. The voltage and temperature dependence of GIDL are characterized. Both results show that interface traps situated near the midgap participate in the conduction of GIDL, and band-trap-band indirect tunneling could be the major mechanism. This is further supported by the fact that the percentage increase in GIDL induced by hot-carrier stress is about the same as the corresponding increase in interface-trap density. On the other hand, under low-field conditions, trap-assisted Poole–Frenkle emission dominates over tunneling for temperatures even well below room temperature. 相似文献
34.
Clinical manifestations and peripheral blood lymphocyte subset changes were studied in patients with myasthenia gravis (MG) to elucidate the mechanism of clinical improvement following treatment, with thymectomy (Tx) or glucocorticoid (GC) therapy. The changes found were: 1. There was a significant increase in percentages of CD3+, CD29+ CD4+ cells and CD4/CD8 ratio and a significant decrease in percentages of CD8+ and CD16,56+ cells in patients who had never been treated with any immune therapy. 2. After Tx or GC therapy, CD3+ and CD4+, CD29+ cells were decreased, but the number CD19+ and CD16, CD56 cells did not change. 3. Tx had a special effect on CD8+ cells. In most of the patients who showed clinical improvement after Tx, CD8+ cells were increased and CD4/CD8 ratio wad decreased. 4. Anti-acetylcholine receptor (AChRAb) titers were markedly decreased after GC therapy. These results indicate that there were obvious abnormalities in cell-mediated immunity in addition to those in humoral immunity in myasthenia gravis. These abnormalities tended to be normalized after Tx or GC therapy. 相似文献
35.
36.
37.
It is demonstrated for the first time that long nanowires with radii as small as 30 nm can be manufactured with a conventional coupler fabrication rig. The temporal deterioration of nanowire optical properties has been studied and correlated with its mechanical behaviour. The original transmission properties have been restored by a post-fabrication treatment. 相似文献
38.
Ten-user truly asynchronous gigabit OCDMA transmission experiment with a 511-chip SSFBG en/decoder 总被引:8,自引:0,他引:8
Hamanaka T. Xu Wang Naoya Wada Nishiki A. Kitayama K. 《Lightwave Technology, Journal of》2006,24(1):95-102
A ten-user truly asynchronous gigabit coherent-optical-code-division-multiple-access (OCDMA) transmission was experimentally demonstrated without using any timing coordination. The enabling technologies are a record-length 511-chip superstructured-fiber-Bragg-grating (SSFBG) en/decoder and a supercontinuum (SC)-based optical-thresholding technique to significantly suppress the signal interference beat noise as well as the multiple-access-interference (MAI) noise. 相似文献
39.
40.
A simple and novel ultra-wideband microstrip-fed antenna with dual band-notched characteristic is presented. By etching a pair of asymmetrical spurlines on the feedline, two notched bands of 600 MHz (3.95? 4.55 GHz) and 650 MHz (5.35?6.0 GHz) are achieved. Measured results show that this antenna operates from 2.5 to 12.0 GHz for voltage standing wave ratio less than 2, except two frequency notched bands of 3.95?4.55 GHz and 5.35?6.0 GHz. Moreover, this antenna has good omnidirectional radiation patterns in the H-plane. 相似文献