全文获取类型
收费全文 | 23251篇 |
免费 | 792篇 |
国内免费 | 613篇 |
专业分类
电工技术 | 475篇 |
技术理论 | 1篇 |
综合类 | 882篇 |
化学工业 | 4708篇 |
金属工艺 | 3952篇 |
机械仪表 | 669篇 |
建筑科学 | 259篇 |
矿业工程 | 208篇 |
能源动力 | 275篇 |
轻工业 | 1424篇 |
水利工程 | 102篇 |
石油天然气 | 168篇 |
武器工业 | 141篇 |
无线电 | 1428篇 |
一般工业技术 | 5860篇 |
冶金工业 | 671篇 |
原子能技术 | 154篇 |
自动化技术 | 3279篇 |
出版年
2024年 | 31篇 |
2023年 | 189篇 |
2022年 | 473篇 |
2021年 | 561篇 |
2020年 | 345篇 |
2019年 | 323篇 |
2018年 | 333篇 |
2017年 | 447篇 |
2016年 | 780篇 |
2015年 | 1456篇 |
2014年 | 1490篇 |
2013年 | 1317篇 |
2012年 | 1294篇 |
2011年 | 2241篇 |
2010年 | 1943篇 |
2009年 | 1851篇 |
2008年 | 1634篇 |
2007年 | 1589篇 |
2006年 | 1071篇 |
2005年 | 1035篇 |
2004年 | 923篇 |
2003年 | 909篇 |
2002年 | 811篇 |
2001年 | 333篇 |
2000年 | 252篇 |
1999年 | 236篇 |
1998年 | 185篇 |
1997年 | 139篇 |
1996年 | 113篇 |
1995年 | 63篇 |
1994年 | 67篇 |
1993年 | 33篇 |
1992年 | 34篇 |
1991年 | 15篇 |
1990年 | 24篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1974年 | 5篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1958年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
MIL-STD-1553B总线标准为目前航空航天领域中广泛应用的一种数据通信标准,在卫星中的应用也十分广泛,为此,1553B总线模拟器也已逐渐成为星载软件开发、测试的必备辅助工具,但由于商用总线仿真卡存在着灵活性不够、不具备网络通信功能等缺点,不能完全满足星载软件研制的需要,而基于总线仿真卡进行再开发能够很好地解决这个问题;文中主要阐述了在Windows和VxWorks两种环境下基于总线仿真卡进行1553B总线模拟器再开发的设计方法和实践体会。 相似文献
82.
基于1553B和外部FLASH实现星上FPGA配置 总被引:1,自引:0,他引:1
太阳辐射监测仪作为某卫星载荷之一,其控制系统主要由DSP+FPGA组成,文章利用1553B和外部Flash实现了系统上电后自动配置FPGA;首先,利用1553B通讯芯片上传FPGA和DSP代码到外部RAM,并通过DSP烧写程序分别烧写到Flash的合理区域;系统上电后,DSP从Flash 0x0地址运行,初始化后运行FPGA配置程序,实现FPGA的动态配置;避免了FPGA跑飞后需要重新上电和归零,提高了系统的可靠性;省去了FPGA专用配置EPROM芯片,简化结构,降低了系统成本;实践证明,FPGA加载时间约2分钟,可定时加载或命令控制加载,该方法简单实用,适合星上载荷使用。 相似文献
83.
绩效管理是人力资源管理的核心,对企业实现战略目标有举足轻重的作用,绩效测评是绩效管理中必不可少的组成部分。本文讲述了一种全面客观的360度绩效测评法,并介绍了一套按照360度绩效测评模型构建的B/S办公系统,重点介绍了使用这套系统进行绩效测评的过程,以便通过信息化手段,有效的运用这一先进测评方法,为企业管理提供有益的支持。 相似文献
84.
在我国的变电所的分布不是非常集中,并且变电的设备也较多,因此精确管理难度和宏观调度都有很大的增加。WEB技术可以使得非常简单的浏览和开发信息,并且可以使得变电所之间的信息交流便得增加,因此电力信息自动化系统的WEB技术应用越来越广泛。 相似文献
85.
Ni59Zr20Ti16Si2Sn3 amorphous material was deposited by a vacuum plasma spraying technique onto steel and copper substrates in order to investigate their behaviour in a corrosive environment. For comparison, the same alloy was prepared as amorphous ribbons by melt spinning. The amorphous nature of the coatings and ribbons was characterized by XRD, DSC and TEM, while XPS and AES analyses were performed to understand the origin of passivation and mode of corrosion. The corrosion behaviour of the coating was studied in H2SO4 and HCl solutions open to air at room temperature. Potentiodynamic polarisation and galvanic coupling tests were carried out on the substrate and the coating. It was found that the formation of Zr-, Ti- and Si-rich passive oxide layers provide a high corrosion resistance in H2SO4 solution while the breakdown of the passive layer by chloride ion adsorption was responsible for pitting corrosion of the Ni59Zr20Ti16Si2Sn3 amorphous ribbons in HCl solution. Galvanic corrosion was the dominant corrosion mechanism for the coating/copper hybrid structure, in contrast to the Ni59Zr20Ti16Si2Sn3 amorphous coating, which efficiently protected the steel substrate in the corrosive environment. 相似文献
86.
Effect of atmospheric pollutants on the corrosion of high power electrical conductors: Part 1. Aluminium and AA6201 alloy 总被引:2,自引:0,他引:2
Rosa Vera 《Corrosion Science》2006,48(10):2882-2900
The aim of this study was to evaluate the joint effect of marine and industrial pollutants on the atmospheric corrosion of aluminium and its AA6201 alloy. Weight loss was determined after 4, 11, 16 and 24 months exposure being morphology and attack intensity analysed through SEM-EDX. Both materials showed the most intense attack for the highest SO2 contents. Good correlation among weight loss, attack depth and tensile strength to rupture with time and with pollutant contents was determined for both materials in most sites. The cause for low aggressiveness of the heaviest Cl− polluted atmosphere on aluminium was electrochemically demonstrated. 相似文献
87.
Taxonomy for protective ability of rust layer using its composition formed on weathering steel bridge 总被引:2,自引:0,他引:2
For a quantitative evaluation of the protectiveness of a rust layer formed on a weathering steel bridge, the relationship between the corrosion rate of the bridge and the composition of the rust layers formed on the girders was first investigated. These corrosion rates were clearly classified by the protective ability index (PAI) of α/γ∗ and (β + s)/γ∗, where α, γ∗, β and s are the mass ratio of crystalline α-FeOOH, the total of γ-FeOOH, β-FeOOH and the spinel-type iron oxide (mainly Fe3O4), β-FeOOH and spinel-type iron oxide, analyzed by XRD, respectively. The inequality of the former index α/γ∗ > 1 expressed the protectiveness criterion of the rust layer, while that of the latter index, (β + s)/γ∗< 0.5 or > 0.5, classified the corrosion rate of the non-protective rust layer. The PAI is useful for a quantitative evaluation of the protectiveness of a rust layer formed on a weathering steel bridge and is an important item for the corrosion assessment of the bridge. 相似文献
88.
F. Zucchi A. Frignani V. Grassi G. Trabanelli C. Monticelli 《Corrosion Science》2007,49(12):4542-4552
The formation of stannate and permanganate–phosphate conversion coatings on AZ31 magnesium alloy was investigated in situ by EIS measurements and their protective performances were studied by different electrochemical techniques in diluted (0.05 M) sodium sulphate solution.The influence that short or long treatment times exert on the performances of such conversion coatings is discussed. While permanganate–phosphate baths always built layers characterized by penetrating cracks, long stannate baths produced layers without interconnected porosity, but were defective. This accounted for the initial greater protectiveness achieved with the stannate treatment; nevertheless, the easy penetration of the electrolytic solution through such a layer quickly decreased its corrosion resistance. 相似文献
89.
Asmaa A. Zidan Mohammed Al-Hawwas Griffith B. Perkins Ghada M. Mourad Catherine J. M. Stapledon Larisa Bobrovskaya Xin-Fu Zhou Plinio R. Hurtado 《International journal of molecular sciences》2021,22(1)
Elucidation of the biological functions of extracellular vesicles (EVs) and their potential roles in physiological and pathological processes is an expanding field of research. In this study, we characterized USC–derived EVs and studied their capacity to modulate the human immune response in vitro. We found that the USC–derived EVs are a heterogeneous population, ranging in size from that of micro–vesicles (150 nm–1 μm) down to that of exosomes (60–150 nm). Regarding their immunomodulatory functions, we found that upon isolation, the EVs (60–150 nm) induced B cell proliferation and IgM antibody secretion. Analysis of the EV contents unexpectedly revealed the presence of BAFF, APRIL, IL–6, and CD40L, all known to play a central role in B cell stimulation, differentiation, and humoral immunity. In regard to their effect on T cell functions, they resembled the function of mesenchymal stem cell (MSC)–derived EVs previously described, suppressing T cell response to activation. The finding that USC–derived EVs transport a potent bioactive cargo opens the door to a novel therapeutic avenue for boosting B cell responses in immunodeficiency or cancer. 相似文献