全文获取类型
收费全文 | 184942篇 |
免费 | 10283篇 |
国内免费 | 5247篇 |
专业分类
电工技术 | 7315篇 |
技术理论 | 3篇 |
综合类 | 9109篇 |
化学工业 | 27339篇 |
金属工艺 | 10288篇 |
机械仪表 | 8975篇 |
建筑科学 | 9877篇 |
矿业工程 | 2669篇 |
能源动力 | 4029篇 |
轻工业 | 11979篇 |
水利工程 | 3345篇 |
石油天然气 | 4954篇 |
武器工业 | 783篇 |
无线电 | 22287篇 |
一般工业技术 | 28867篇 |
冶金工业 | 7699篇 |
原子能技术 | 1482篇 |
自动化技术 | 39472篇 |
出版年
2024年 | 451篇 |
2023年 | 1610篇 |
2022年 | 3064篇 |
2021年 | 4227篇 |
2020年 | 2985篇 |
2019年 | 2462篇 |
2018年 | 16875篇 |
2017年 | 16330篇 |
2016年 | 12622篇 |
2015年 | 4594篇 |
2014年 | 5376篇 |
2013年 | 6714篇 |
2012年 | 10059篇 |
2011年 | 16916篇 |
2010年 | 14790篇 |
2009年 | 11852篇 |
2008年 | 12993篇 |
2007年 | 13645篇 |
2006年 | 5890篇 |
2005年 | 5964篇 |
2004年 | 4321篇 |
2003年 | 3871篇 |
2002年 | 3307篇 |
2001年 | 2470篇 |
2000年 | 2375篇 |
1999年 | 2247篇 |
1998年 | 2052篇 |
1997年 | 1770篇 |
1996年 | 1597篇 |
1995年 | 1283篇 |
1994年 | 1013篇 |
1993年 | 817篇 |
1992年 | 658篇 |
1991年 | 510篇 |
1990年 | 415篇 |
1989年 | 324篇 |
1988年 | 282篇 |
1987年 | 196篇 |
1986年 | 162篇 |
1985年 | 142篇 |
1984年 | 103篇 |
1983年 | 76篇 |
1982年 | 71篇 |
1981年 | 62篇 |
1980年 | 52篇 |
1976年 | 55篇 |
1968年 | 50篇 |
1966年 | 45篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Yang C.W. Fang Y.K. Lin C.S. Tsair Y.S. Chen S.M. Wang W.D. Wang M.F. Cheng J.Y. Chen C.H. Yao L.G. Chen S.C. Liang M.S. 《Electronics letters》2003,39(21):1499-1501
A novel technique to form high-K dielectric of HfSiON by doping base oxide with Hf and nitridation with NH/sub 3/, sequentially, is proposed. The HfSiON gate dielectric demonstrates excellent device performances such as only 10% degradation of saturation drain current and almost 45 times of magnitude reduction in gate leakage compared with conventional SiO/sub 2/ gate at the approximately same equivalent oxide thickness. Additionally, negligible flatband voltage shift is achieved with this technique. Time-dependent dielectric breakdown tests indicate that the lifetime of HfSiON is longer than 10 years at V/sub dd/=2 V. 相似文献
152.
Y.K. Su H.C. Wang C.L. Lin W.B. Chen S.M. Chen 《Photonics Technology Letters, IEEE》2003,15(10):1345-1347
The brightness of AlGaInP light emitting diodes (LEDs) has been raised by a factor of 1.12 at 20 mA by sulfide passivation. Meanwhile, the sulfide also can decrease leakage current of AlGaInP LEDs at -2 V to nearly one thousandth of that in the as-fabricated device. The possible causes for the brightness increase of AlGaInP LEDs after sulfide treatment including surface roughness, reduction of Fresnel loss, and effective injection of carriers were demonstrated. 相似文献
153.
154.
155.
Dong-Soo Yoon Jae Sung Roh Sung-Man Lee Hong Koo Baik 《Journal of Electronic Materials》2003,32(8):890-898
The effect of a thin RuOx layer formed on the Ru/TiN/doped poly-Si/Si stack structure was compared with that on the RuOx/TiN/doped poly-Si/Si stack structure over the post-deposition annealing temperature ranges of 450–600°C. The Ru/TiN/poly-Si/Si
contact system exhibited linear behavior at forward bias with a small increase in the total resistance up to 600°C. The RuOx/TiN/poly-Si/Si contact system exhibited nonlinear characteristics under forward bias at 450°C, which is attributed to no
formation of a thin RuOx layer at the RuOx surface and porous-amorphous microstructure. In the former case, the addition of oxygen at the surface layer of the Ru film
by pre-annealing leads to the formation of a thin RuOx layer and chemically strong Ru-O bonds. This results from the retardation of oxygen diffusion caused by the discontinuity
of diffusion paths. In particular, the RuOx layer in a nonstoichiometric state is changed to the RuO2-crystalline phase in a stoichiometric state after post-deposition annealing; this phase can act as an oxygen-capture layer.
Therefore, it appears that the electrical properties of the Ru/TiN/poly-Si/Si contact system are better than those of the
RuOx/TiN/poly-Si/Si contact system. 相似文献
156.
JM Piepmeier DL Keefe MA Weinstein D Yoshida J Zielinski TT Lin Z Chen F Naftolin 《Canadian Metallurgical Quarterly》1993,32(3):422-30; discussion 430-1
Estramustine is an estradiol-based agent that has been shown to accumulate in human glioma cells, resulting in a concentration-dependent alteration in cell size and shape within minutes and an inhibition of proliferation over 3 to 6 days. We evaluated human glioblastoma cultures with [3H]thymidine incorporation assays to determine estramustine's early effects on deoxyribonucleic acid synthesis in these tumors. Because estramustine shares a common structural motif with other antimicrotubule drugs, we synthesized four A-ring conjugates of estrone that contained a carbamate moiety but lacked nitrogen mustard. These analogs were examined by [3H]thymidine incorporation and compared with vinblastine. Greater than 70% inhibition of [3H]thymidine incorporation occurred within 1 hour of treatment with estramustine at 10(-5) mol/L, which increased to 80% inhibition at 4 hours. Ethyl carbamate JE208 was nearly as effective as estramustine in inhibiting deoxyribonucleic acid synthesis, and both were more effective than vinblastine. The inhibitory effects of estramustine and estrone analogs were reversible; vinblastine was not reversible. Although estramustine and JE208 induced similar antiproliferative and morphological changes in glioblastoma cells that persisted for at least 4 days, there was a modest recovery of morphology and thymidine incorporation with JE208 after prolonged treatment. The common findings with estramustine and JE208 suggest that these agents may have a similar mechanism of action and form the basis for the investigation of new agents that may rapidly and reversibly inhibit glioblastoma. 相似文献
157.
In this study, the effect and side-effect of epidural injection with lappaconitine compound for post-operative analgesia was observed. One hundred and twenty patients were randomly divided into 4 groups. Lappaconitine compound (LB) consisted of 12 mg of lappaconitine and 22.5 mg of bupivacaine, was given to group A (the group of observation), and lappaconitine 12 mg, bupivacaine 22.5 mg and morphine 2 mg to group B, C and D respectively for control. All were given by epidural injection with single blind method during post-operative pain of incision operation. Result showed that the initiating of analgesia was quicker in group A and C than that in group B and D, and the efficacy was group D > A > C > B. There was significant difference between group A and B in the above two parameters, P < 0.01 and P < 0.05. The analgisia maintenence time of single injection was D > A > B > C, that of group D was significantly longer than that of group A (P < 0.01). It indicated that the epidural injection with LB was more rapid and potent than that with lappaconitine alone in post-operative analgesia, and the former had no side-effect, it was safer than morphine. 相似文献
158.
本文概述了离子注入过程中污染产生的原因和防止污染的措施,特别强调了对微粒污染和金属污染的防护以满足ULSI加工对离子注入的要求。 相似文献
159.
160.
Min-Shiang Hwang Chih-Wei Lin Cheng-Chi Lee 《Electronics letters》2002,38(23):1429-1431
An authenticated multiple-key agreement protocol is proposed. The protocol is not only secure against the unknown-key attack but also more efficient than other protocols. 相似文献