全文获取类型
收费全文 | 5520篇 |
免费 | 48篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 38篇 |
综合类 | 5篇 |
化学工业 | 348篇 |
金属工艺 | 218篇 |
机械仪表 | 63篇 |
建筑科学 | 98篇 |
矿业工程 | 86篇 |
能源动力 | 75篇 |
轻工业 | 233篇 |
水利工程 | 24篇 |
石油天然气 | 4篇 |
无线电 | 288篇 |
一般工业技术 | 442篇 |
冶金工业 | 3302篇 |
原子能技术 | 34篇 |
自动化技术 | 311篇 |
出版年
2021年 | 39篇 |
2020年 | 23篇 |
2019年 | 31篇 |
2018年 | 29篇 |
2017年 | 29篇 |
2016年 | 40篇 |
2015年 | 27篇 |
2014年 | 51篇 |
2013年 | 155篇 |
2012年 | 73篇 |
2011年 | 106篇 |
2010年 | 95篇 |
2009年 | 104篇 |
2008年 | 90篇 |
2007年 | 111篇 |
2006年 | 109篇 |
2005年 | 70篇 |
2004年 | 68篇 |
2003年 | 65篇 |
2002年 | 57篇 |
2001年 | 57篇 |
2000年 | 70篇 |
1999年 | 132篇 |
1998年 | 1006篇 |
1997年 | 564篇 |
1996年 | 426篇 |
1995年 | 239篇 |
1994年 | 196篇 |
1993年 | 242篇 |
1992年 | 60篇 |
1991年 | 66篇 |
1990年 | 58篇 |
1989年 | 71篇 |
1988年 | 59篇 |
1987年 | 58篇 |
1986年 | 67篇 |
1985年 | 56篇 |
1984年 | 32篇 |
1983年 | 36篇 |
1982年 | 31篇 |
1981年 | 44篇 |
1980年 | 46篇 |
1979年 | 28篇 |
1978年 | 34篇 |
1977年 | 97篇 |
1976年 | 170篇 |
1975年 | 28篇 |
1974年 | 33篇 |
1973年 | 33篇 |
1972年 | 24篇 |
排序方式: 共有5569条查询结果,搜索用时 15 毫秒
1.
John D. Rodney S. Deepapriya M. Cyril Robinson C. Justin Raj Suresh Perumal Byung Chul Kim S. Krishnan S. Jerome Das 《International Journal of Hydrogen Energy》2021,46(54):27585-27596
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting. 相似文献
2.
Chemical engineering systems often involve a functional porous medium, such as in catalyzed reactive flows, fluid purifiers, and chromatographic separations. Ideally, the flow rates throughout the porous medium are uniform, and all portions of the medium contribute efficiently to its function. The permeability is a property of a porous medium that depends on pore geometry and relates flow rate to pressure drop. Additive manufacturing techniques raise the possibilities that permeability can be arbitrarily specified in three dimensions, and that a broader range of permeabilities can be achieved than by traditional manufacturing methods. Using numerical optimization methods, we show that designs with spatially varying permeability can achieve greater flow uniformity than designs with uniform permeability. We consider geometries involving hemispherical regions that distribute flow, as in many glass chromatography columns. By several measures, significant improvements in flow uniformity can be obtained by modifying permeability only near the inlet and outlet. 相似文献
3.
4.
Modeling ion implantation of HgCdTe 总被引:2,自引:0,他引:2
H. G. Robinson D. H. Mao B. L. Williams S. Holander-Gleixner J. E. Yu C. R. Helms 《Journal of Electronic Materials》1996,25(8):1336-1340
Ion implantation of boron is used to create n on p photodiodes in vacancy-doped mercury cadmium telluride (MC.T). The junction
is formed by Hg interstitials from the implant damage region diffusing into the MC.T and annihilating Hg vacancies. The resultant
doping profile is n+/n-/p, where the n+ region is near the surface and roughly coincides with the implant damage, the n- region is where Hg vacancies have been annihilated revealing a residual grown-in donor, and the p region remains doped by
Hg vacancy double acceptors. We have recently developed a new process modeling tool for simulating junction formation in MC.T
by ion implantation. The interstitial source in the damage region is represented by stored interstitials whose distribution
depends on the implant dose. These interstitials are released into the bulk at a constant, user defined rate. Once released,
they diffuse away from the damage region and annihilate any Hg vacancies they encounter. In this paper, we present results
of simulations using this tool and show how it can be used to quantitatively analyze the effects of variations in processing
conditions, including implant dose, annealing temperature, and doping background. 相似文献
5.
6.
JB Kamien WK Bickel BJ Smith GJ Badger JR Hughes 《Canadian Metallurgical Quarterly》1997,58(4):983-991
The percentage of long-term survivors after intensive chemotherapy and the outcome of MDS patients who achieve partial remission (PR) with intensive chemotherapy (IC) are not known. Between 1981 and 1996 we treated 99 patients with de novo MDS who had high-risk MDS or progression to AML, with IC. 41 (41%) achieved CR, 16 (16%) achieved partial remission (PR), 26 (26%) had failure, and 16 (16%) died in aplasia. Eight of the patients who achieved CR were autografted, three were allografted and the remaining cases received moderate consolidation chemotherapy. After IC, the 16 PR patients fulfilled the criteria for RA in 15 cases and CMML in one case. Median PR duration was 17 months, and three PR were > 3 years (39, 50+, 82+ months). Median actuarial survival of patients who achieved PR and CR was 18 months and 20 months from the onset of IC, respectively (difference not significant). Of the 71 patients treated before 1993, with sufficient follow-up, 10 (14%) had survived > 4 years (long-term survivors). Four of them were alive in first CR after 49+ to 110+ months and probably cured, two were alive in PR after 50+ and 82+ months and four had died after 49-78 months. Long-term survivors were characterized by a significantly higher incidence of RAEB-T at diagnosis, and with normal or favourable cytogenetic findings. In patients with RAEB-T at diagnosis included before 1993, 8/23 (35%) cases who had no unfavourable karyotype had survived > 4 years. Our findings suggest that MDS patients who achieve PR with IC, and not only those who achieve CR, can benefit from this type of treatment. The percentage of long-term survivors remains low, however, and is almost restricted to patients with RAEB-T at diagnosis and no unfavourable karyotype. 相似文献
7.
8.
9.
We have compared the duration of motor block produced by four local anaesthetics administered into a chronically implanted subarachnoid catheter in rabbits. Each group (n = 6) received four different doses of amethocaine, bupivacaine, lignocaine or procaine, and the duration of the resulting motor block was assessed. Dose-response curves were plotted for each drug. As a measure of activity of the anaesthetics, we used the dose of each drug required to produce block of 60-min duration (D60 min) and the correlation between D60 min and different drug properties was examined. An inverse linear correlation (r = 0.995; P < 0.01) was observed between log D60 min and the log of the partition coefficient of the local anaesthetics. No correlation was found between the effect and degree of protein binding, pKa or molecular weight. These results suggest that, in spinal anaesthesia, the partition coefficient could be used as a predictor of the duration of anaesthetic action. 相似文献
10.
Bound-state beta decay of highly ionized atoms 总被引:1,自引:0,他引:1