全文获取类型
收费全文 | 5305篇 |
免费 | 418篇 |
国内免费 | 283篇 |
专业分类
电工技术 | 471篇 |
技术理论 | 1篇 |
综合类 | 281篇 |
化学工业 | 612篇 |
金属工艺 | 1088篇 |
机械仪表 | 375篇 |
建筑科学 | 145篇 |
矿业工程 | 89篇 |
能源动力 | 285篇 |
轻工业 | 143篇 |
水利工程 | 27篇 |
石油天然气 | 110篇 |
武器工业 | 30篇 |
无线电 | 652篇 |
一般工业技术 | 744篇 |
冶金工业 | 388篇 |
原子能技术 | 58篇 |
自动化技术 | 507篇 |
出版年
2024年 | 28篇 |
2023年 | 100篇 |
2022年 | 178篇 |
2021年 | 200篇 |
2020年 | 174篇 |
2019年 | 173篇 |
2018年 | 144篇 |
2017年 | 204篇 |
2016年 | 201篇 |
2015年 | 225篇 |
2014年 | 295篇 |
2013年 | 305篇 |
2012年 | 329篇 |
2011年 | 351篇 |
2010年 | 270篇 |
2009年 | 352篇 |
2008年 | 327篇 |
2007年 | 322篇 |
2006年 | 294篇 |
2005年 | 195篇 |
2004年 | 188篇 |
2003年 | 176篇 |
2002年 | 166篇 |
2001年 | 152篇 |
2000年 | 145篇 |
1999年 | 103篇 |
1998年 | 74篇 |
1997年 | 74篇 |
1996年 | 56篇 |
1995年 | 29篇 |
1994年 | 27篇 |
1993年 | 16篇 |
1992年 | 29篇 |
1991年 | 9篇 |
1990年 | 23篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有6006条查询结果,搜索用时 15 毫秒
1.
Mastocytosis is a type of myeloid neoplasm characterized by the clonal, neoplastic proliferation of morphologically and immunophenotypically abnormal mast cells that infiltrate one or more organ systems. Systemic mastocytosis (SM) is a more aggressive variant of mastocytosis with extracutaneous involvement, which might be associated with multi-organ dysfunction or failure and shortened survival. Over 80% of patients with SM carry the KIT D816V mutation. However, the KIT D816V mutation serves as a weak oncogene and appears to be a late event in the pathogenesis of mastocytosis. The management of SM is highly individualized and was largely palliative for patients without a targeted form of therapy in past decades. Targeted therapy with midostaurin, a multiple kinase inhibitor that inhibits KIT, has demonstrated efficacy in patients with advanced SM. This led to the recent approval of midostaurin by the United States Food and Drug Administration and European Medicines Agency. However, the overall survival of patients treated with midostaurin remains unsatisfactory. The identification of genetic and epigenetic alterations and understanding their interactions and the molecular mechanisms involved in mastocytosis is necessary to develop rationally targeted therapeutic strategies. This review briefly summarizes recent developments in the understanding of SM pathogenesis and potential treatment strategies for patients with SM. 相似文献
2.
3.
In the present work, inter-diffusion of nickel and titanium and formation of Ni-Ti intermetallic compounds on Ti-6Al-4V substrate have been studied. Initially, nickel was electrodeposited on the alloy using a modified Watts bath solution at a current density of 2 A dm?2 for 1?h. The coated specimens were then heat treated for different durations at 750, 800 and 850 °C under argon atmosphere. The effects of temperature and time on the characteristics, hardness and wear resistance of intermetallic phases were investigated. The results showed that a multilayer structure was formed after heat treatment, an outer layer of residual nickel, an area of intermetallic layers with different compositions followed by a solid solution of Ni-Ti. It was also observed that an increase in time or temperature at first led to the formation of thicker intermetallic layers; however, after passing a critical point, the intermetallic layers seem to dissolve into the substrate. Furthermore, the wear rates of the diffusion treated samples were four times lower compared to Ti-6Al-4V alloy when sliding against AISI 52100 hardened steel. 相似文献
4.
F. Schröder R. M. Ward A. R. Walpole R. P. Turner M. M. Attallah J.-C. Gebelin 《Materials Science & Technology》2015,31(3):372-384
Linear friction welding of the Ti6Al4V alloy is studied. A new definition of the energy input rate is proposed, based on an integration over time of the in-plane force and velocity; a strong correlation with the upset rate is then found. The effective friction coefficient is estimated to be 0·5±0·1 for varying frequencies and amplitudes, with only a weak dependence on the processing conditions displayed. A model is proposed that accounts for both the conditioning and equilibrium stages of the process, which is shown to be in good agreement with the experimental data. The model is used to study the mechanism by which the flash is formed. A criterion is proposed by which the rippled nature of its morphology can be predicted. 相似文献
5.
6.
在保证优秀的音频质量下,提高音频编码的压缩效率是数字音频技术一直追求的目标,简单介绍目前最先进的音频编码HE-AAC V2的原理及应用,着重介绍其中用到的两种新技术频带复制(SBR)技术和参数立体声(PS)技术. 相似文献
7.
本文在液相合成(SrPb)TiO3粉的基础上,研究了升温速率、保温时间、烧结温度及降温方式对(SrPb)TiO3基陶瓷的V型PTC热敏特性的影响。实验表明:升温速率对其热敏特性影响不大,保温时间和烧结温度的作用是一致的,具有一最佳范围。而降浊方式对材料的热敏特性影响较大。综合各因素的影响,本配方中,样品的烧结制度定为:以200℃/h的速率升温,在1250℃保温1h,炉冷至950℃,保温0.5h,再 相似文献
8.
通过对LD(7Cr7Mo3V2Si)模具钢起塑性压缩变形后的金相组织观察研究,分析了变形参数、原始组织对变形后金相组织的影响。 相似文献
9.
10.
Masami Ikeda Susumu Fukumoto Hiroshi Takao Shinya Ohtsuka Eiichi Haginomori Masayuki Hikita 《Electrical Engineering in Japan》2002,141(4):16-24
This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043 相似文献