全文获取类型
收费全文 | 413篇 |
免费 | 17篇 |
国内免费 | 50篇 |
专业分类
电工技术 | 7篇 |
综合类 | 21篇 |
化学工业 | 61篇 |
金属工艺 | 128篇 |
机械仪表 | 1篇 |
矿业工程 | 5篇 |
能源动力 | 8篇 |
轻工业 | 2篇 |
武器工业 | 1篇 |
无线电 | 25篇 |
一般工业技术 | 92篇 |
冶金工业 | 78篇 |
原子能技术 | 42篇 |
自动化技术 | 9篇 |
出版年
2023年 | 19篇 |
2022年 | 15篇 |
2021年 | 20篇 |
2020年 | 18篇 |
2019年 | 11篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 28篇 |
2012年 | 30篇 |
2011年 | 28篇 |
2010年 | 28篇 |
2009年 | 35篇 |
2008年 | 39篇 |
2007年 | 29篇 |
2006年 | 25篇 |
2005年 | 16篇 |
2004年 | 21篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有480条查询结果,搜索用时 78 毫秒
71.
Zhijin Chen Dexin Yu Shaojie Wang Na Zhang Chunhong Ma Zaijun Lu 《Nanoscale research letters》2009,4(7):618-626
Accurate diagnosis in early stage is vital for the treatment of Hepatocellular carcinoma. The aim of this study was to investigate
the potential of poly lactic acid–polyethylene glycol/gadolinium–diethylenetriamine-pentaacetic acid (PLA–PEG/Gd–DTPA) nanocomplexes
using as biocompatible molecular magnetic resonance imaging (MRI) contrast agent. The PLA–PEG/Gd–DTPA nanocomplexes were obtained
using self-assembly nanotechnology by incubation of PLA–PEG nanoparticles and the commercial contrast agent, Gd–DTPA. The
physicochemical properties of nanocomplexes were measured by atomic force microscopy and photon correlation spectroscopy.
The T1-weighted MR images of the nanocomplexes were obtained in a 3.0 T clinical MR imager. The stability study was carried out
in human plasma and the distribution in vivo was investigated in rats. The mean size of the PLA–PEG/Gd–DTPA nanocomplexes
was 187.9 ± 2.30 nm, and the polydispersity index was 0.108, and the zeta potential was −12.36 ± 3.58 mV. The results of MRI
test confirmed that the PLA–PEG/Gd–DTPA nanocomplexes possessed the ability of MRI, and the direct correlation between the
MRI imaging intensities and the nano-complex concentrations was observed (r = 0.987). The signal intensity was still stable within 2 h after incubation of the nanocomplexes in human plasma. The nanocomplexes
gave much better image contrast effects and longer stagnation time than that of commercial contrast agent in rat liver. A
dose of 0.04 mmol of gadolinium per kilogram of body weight was sufficient to increase the MRI imaging intensities in rat
livers by five-fold compared with the commercial Gd–DTPA. PLA–PEG/Gd–DTPA nanocomplexes could be prepared easily with small
particle sizes. The nanocomplexes had high plasma stability, better image contrast effect, and liver targeting property. These
results indicated that the PLA–PEG/Gd–DTPA nanocomplexes might be potential as molecular targeted imaging contrast agent. 相似文献
72.
采用传统的固相反应法制备了CGO(Ce0.8Gd0.2O1.9)固体电解质,研究了CuO烧结助剂对CGO的体密度、相组成、微观结构及电性能的影响。结果表明,加入CuO的样品的体密度随烧结温度的升高而增大,1300℃烧结的样品致密化程度最高,当烧结温度为1350℃时,样品有过烧现象。与纯的CGO相比,CuO的加入使样品的烧结温度降低了将近300℃,而且经高温烧结后仍为立方萤石结构,无新相生成。CGO交流阻抗谱与电导率分析表明,当CuO的掺杂量为1%(摩尔分数),烧结温度为1300℃时电导率最高,所以CuO作为烧结助剂不仅降低了烧结温度,使晶粒尺寸减小,同时还提高了电导率,因而CuO是很好的烧结助剂。 相似文献
73.
S. Mizusaki A. DouzonoT. Ohnishi T.C. OzawaH. Samata Y. NoroY. Nagata 《Journal of Alloys and Compounds》2012,510(1):141-146
The present study reveals that the correlation between the magnetic properties with composition x in the polycrystalline Ru2Mn1−xFexGe system. Hard ferromagnetic properties appeared at the intermediate composition between antiferromagnetic Ru2MnGe with soft ferromagnetic Ru2FeGe. Ru2Mn0.6Fe0.4Ge shows an anisotropic and negative magnetoresistance (MR) effect more than 8% although the both end materials are small MR effect less than 1%. These experimental results correlate the variation in MR ratio with that of coercive field as a function of x. Moreover, the correlation is shown at the boundary of magnetism between antiferromagnetic and ferromagnetic. Therefore, the present experimental results imply that the coexistence of antiferromagnetic and soft ferromagnetic leads to induce the MR effect in this system. 相似文献
74.
75.
添加Gd对烧结Nd-Fe-B永磁材料磁性能与抗蚀性的影响 总被引:2,自引:1,他引:1
选择不同Gd添加量制备了(Pr-Nd)32.4-xGdxFebalCu0.25Al0.65B1.08永磁材料,研究了Gd元素添加对材料磁性能、抗腐蚀性能的影响.添加3%的Gd显著改善材料的抗蚀性,较大幅度提高内禀矫顽力,但使剩磁略有下降;随着Gd添加量进一步增大,材料抗蚀性继续提高,剩磁明显下降,内禀矫顽力亦开始出现下降的趋势.Gd添加一定程度上细化磁体晶粒,减少显微组织中孔隙、疏松等缺陷的存在,同时Gd进入富稀土相而提高其化学稳定性而使材料性能得以提高. 相似文献
76.
Er3+: Y0.5Gd0.5VO4激光晶体的生长和热学性质 总被引:1,自引:1,他引:0
用提拉法生长出Er3 : Y0.5Gd0.5VO4单晶,用电感耦合等离子体(ICP)光谱法测定晶体中Er3 原子数分数为0.83%,有效分凝系数为1.03.在30~1300℃测量了晶体a轴和c轴的热膨胀系数分别为2.08×10-6/℃,8.87×10-6/℃;测得晶体在25℃时的比热值为0.48J/(g·K).采用激光脉冲法测量了晶体的热扩散系数,并通过计算得出晶体的热导率,在25~200℃温度范围,晶体在<100方向上的热导率为6.1~4.9W/(m·K),在<001方向上的热导率为7.7~6.2W/(m·K). 相似文献
77.
78.
In this paper, the Gd2O3:Eu3+,Tb3+phosphors with different doping concentrations of Eu3+and Tb3+ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3:Eu3+,Tb3+phosphors were analyzed by means of X-ray powder diffraction (XRD), transmission electron mi-croscopy (TEM) and scanning electron microscopy (SEM). The photoluminescence (PL) properties of Gd2O3:Eu3+,Tb3+phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3+was fixed at 1 mol.%, the emis-sion intensity of Eu3+ions was degenerating with Tb3+content increasing, while when the Tb3+content was fixed at 1 mol.%, the emission intensity of Tb3+ions reached a maximum when the concentration of Eu3+was 2 mol.%, implying that the energy transfer from Eu3+to Tb3+took place. In addition, Tb3+could inspire blue-green light and the Eu3+could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials. 相似文献
79.
Gd对ZL205A合金显微组织和力学性能的影响 总被引:1,自引:0,他引:1
研究了不同质量分数Gd对ZL205A合金铸态及T6态显微组织和力学性能的影响.采用光学显微镜、荧光光谱仪和电子探针对制备的试样微观组织和元素分布进行分析,并利用电子拉伸试验机对铸锭的力学性能进行测试.结果表明:微量稀土元素Gd能细化ZL205A合金的晶粒,并与合金中的其他元素形成新相,能提高合金铸态和T6后的力学性能;当Gd加入量为0.06%时,综合力学性能最优,铸态时抗拉强度为192MPa,伸长率为11.1%;T6态时抗拉强度达到421.1MPa,伸长率为10.2%.但当Gd添加量过多时,合金的组织与性能均产生恶化. 相似文献
80.
采用X射线衍射、物理性能测试系统、显微硬度计及电化学工作站研究了经氩弧熔炼、1123 K均匀化热处理168 h的 Gd99.75Fe0.25合金的磁热效应及应用特性。结果表明:Gd99.75Fe0.25合金仍保持纯Gd的六方晶体结构;Gd99.75Fe0.25合金的居里温度为294 K,且在居里点附近发生铁磁到顺磁的二级相变,2和5 T外场下的最大磁熵变分别为4.99和9.37 J·kg-1·K-1,均大于纯Gd;Gd99.75Fe0.25合金的显微硬度(HV0.2)590 MPa,与纯Gd相当,但少量Fe的掺杂提高了Gd的耐蚀性。含少量Fe的Gd99.75Fe0.25合金具有大的磁热效应及良好的应用特性,是一种有很大应用潜力的室温磁致冷材料。 相似文献