全文获取类型
收费全文 | 2090篇 |
免费 | 145篇 |
国内免费 | 110篇 |
专业分类
电工技术 | 83篇 |
综合类 | 98篇 |
化学工业 | 265篇 |
金属工艺 | 116篇 |
机械仪表 | 82篇 |
建筑科学 | 50篇 |
矿业工程 | 20篇 |
能源动力 | 100篇 |
轻工业 | 132篇 |
水利工程 | 10篇 |
石油天然气 | 50篇 |
武器工业 | 4篇 |
无线电 | 457篇 |
一般工业技术 | 219篇 |
冶金工业 | 124篇 |
原子能技术 | 130篇 |
自动化技术 | 405篇 |
出版年
2024年 | 3篇 |
2023年 | 42篇 |
2022年 | 42篇 |
2021年 | 40篇 |
2020年 | 21篇 |
2019年 | 36篇 |
2018年 | 29篇 |
2017年 | 37篇 |
2016年 | 36篇 |
2015年 | 40篇 |
2014年 | 47篇 |
2013年 | 78篇 |
2012年 | 57篇 |
2011年 | 89篇 |
2010年 | 98篇 |
2009年 | 172篇 |
2008年 | 190篇 |
2007年 | 153篇 |
2006年 | 131篇 |
2005年 | 141篇 |
2004年 | 136篇 |
2003年 | 166篇 |
2002年 | 117篇 |
2001年 | 109篇 |
2000年 | 78篇 |
1999年 | 62篇 |
1998年 | 41篇 |
1997年 | 41篇 |
1996年 | 26篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1975年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有2345条查询结果,搜索用时 15 毫秒
131.
本研究利用固相反应法制备稀土硅酸盐氧基磷灰石Gd10-x(SiO4)6O3-1.5x(x=0,1,1.33)陶瓷材料,用XRD对所合成的Gd10-x(SiO4)6O3-1.5x粉末和烧结得到的块体材料进行分析表征。研究Gd10-x(SiO4)6O3-1.5x陶瓷材料的声子速度和弹性模量。另外,利用激光闪射法测量Gd10-x(SiO4)6O3-1.5x陶瓷材料的热扩散系数,进一步得到热导率。结果表明Gd10-x(SiO4)6O3-1.5x陶瓷材料平均声速小、弹性模量低,热导率低,其中Gd9(SiO4)6O1.5陶瓷材料的热导率最低。 相似文献
132.
Studies using advanced analytical techniques indicated that the reactiveelements (RE) segregate along the oxide grain boundaries and at theoxide–alloy interface during oxidation of -Al2O3forming alloys. The segregation results in inward oxygen diffusion along theoxide grain boundaries as the predominant transport process in the oxidegrowth. The present work establishes a mathematical model based on themechanisms of inward oxygen diffusion along the grain boundaries and oxidegrain coarsening. This model has been used to describe the oxidationkinetics of Y-doped Fe–Cr–Al alloys. The results showed a muchbetter agreement with the experimental data than the parabolic rate law. Byusing this model, the exponential number for the grain coarsening of aluminascales during oxidation was calculated to be 3. The activation energyfor oxygen diffusing along the grain boundaries was 450 kJ/mol. They arealso in good agreement with values reported in the literatures. 相似文献
133.
O.V. Borodin 《Journal of Nuclear Materials》2009,385(2):325-328
Structure evolution and degradation mechanisms during irradiation of 18Cr-10Ni-Ti steel (material of VVER-1000 reactor internals are investigated). Using accelerator irradiations with Cr3+ and Ar+ ions allowed studying effects of dose rate, different initial structure state and implanted ions on features of structure evolution and main mechanisms of degradation including low temperature swelling and embrittlement of the 18Cr-10Ni-Ti steel. It is shown that differences in dose rate at most irradiation temperatures mainly exert their influence on the duration of the swelling transient regime. Calculations of possible transmutation products during irradiation of this steel in a VVER-1000 spectrum were performed. It is shown that gaseous atoms (He and H), which are generated simultaneously with radiation defects, stabilize the elements of radiation microstructure and influence the swelling. The nature of deformation under different temperatures of irradiation and of mechanical testing is investigated. It is shown that the temperature sensitivity of swelling behaviour in the investigated steel, with different initial structures can be connected with the dynamic behaviour of point defect sinks. 相似文献
134.
M. Schulz R. Moshammer M. Dürr A. Hasan M.F. Ciappina 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(2):187-191
Recent developments on kinematically complete experiments on basic atomic fragmentation processes are reviewed. Comparisons between theoretical and experimental fully differential cross sections for single ionization of light atoms by charged particle impact are analyzed. Furthermore, a method developed very recently, four-particle Dalitz plots, is discussed in context of double ionization. The extraordinary power of these plots is their capability to provide a comprehensive picture of the momentum exchange between all four final-state particles in a single spectrum. 相似文献
135.
A. Kupliauskien? 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(2):266-269
A general expression for the cross section describing properties of the fluorescence radiation from polarized atoms excited by polarized electrons is obtained in the distorted wave (DW) approximation. The expression is presented in the form of multiple expansion over the state multipoles of all particles taking part in the two-step process. It is used to derive the alignment parameters of excited atom and angular distribution of emitted fluorescence. The polarization degree of radiation from the lowest autoionizing states following the excitation of non-polarized Na and K atoms by non-polarized electrons is calculated. 相似文献
136.
V. Švor?ík N. Kasálková K. Záruba L. Ba?áková V. Lisá H. Gbelcová A. Macková 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(11):1904-1910
Polyethylene (PE) was irradiated with inert Ar plasma, and the chemically active PE surface was grafted with Au nanoparticles. The composition and the structure of the modified PE surface were studied using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Changes in the surface wettability were determined from the contact angle measured in a reflection goniometer. The changes in the surface roughness and morphology were followed by atomic force microscopy (AFM). The modified PE samples were seeded with rat vascular smooth muscle cells (VSMC) or mouse NIH 3T3 fibroblasts, and their adhesion and proliferation were studied. We found that plasma discharge and Au grafting lead to dramatic changes in the surface morphology and roughness of PE. The Au nanoparticles were found not only on the sample surface, but also in the sample interior up to the depth of about 100 nm. In addition, plasma modification of the PE surface, followed with grafting Au-nanoparticles, significantly increased the attractiveness of the PE surface for the adhesion and growth of VSMC, and particularly for mouse embryonic 3T3 fibroblasts. 相似文献
137.
利用26S r DNA D1/D2区序列分析法鉴定了内蒙古牧区传统开菲尔发酵液中的酵母菌,为筛选可发酵特色乳酒的酵母菌奠定基础。对所分离纯化得的酵母菌进行菌落特征和细胞显微形态区分,在形态鉴定基础上,选择代表菌进行26S r DNA D1/D2区序列分子鉴定。结果表明,共分离到36株酵母菌,形态聚类为5类,经DNA提取、26S r DNA D1/D2区PCR扩增、酶切、基因序列分析和同源性比对,鉴定为5种分子类型的酵母菌,分别为胶红酵母菌(Rhodotorula mucilaginosa)、诞沫假丝酵母菌(Candida zeylanoides)、发酵毕赤酵母菌(Pichia fermentans)、酿酒酵母菌(Saccharomyces cerevisiae)、有孢圆酵母菌(Torulaspora delbrueckii)。传统开菲尔发酵液中分离到的酿酒酵母,具有可发酵特色乳酒的潜质。 相似文献
138.
139.
本研究对涨袋泡椒凤爪产品中的主要腐败菌及其生长特性进行了分析。采用传统的分离培养方法,筛选出主要的污染菌群,通过美兰染色镜检对细胞形态进行检测,利用26S rDNA D1/D2区序列测定及系统发育分析对分离菌株进行鉴定,采取ERIC-RAPD技术对分离菌株的分子遗传多态性进行分析,最后对优势菌株的生长特性进行研究。结果表明:从涨袋产品中共分离出40株酵母菌,分别编号为PJ1~PJ40,镜检发现所有菌株的细胞形态相同,均为椭圆形。经分子鉴定发现所分离菌株都为解脂耶氏酵母,且为两个基因分型,说明解脂耶氏酵母是该产品中的一种优势腐败菌,且污染源不同。同时,研究发现解脂耶氏酵母PJ1的最适生长pH值为4.5、最适生长温度为25℃、并且NaCl浓度的升高对该菌的生长起到一定的抑制作用。 相似文献
140.