全文获取类型
收费全文 | 54446篇 |
免费 | 4664篇 |
国内免费 | 3262篇 |
专业分类
电工技术 | 4198篇 |
技术理论 | 1篇 |
综合类 | 3610篇 |
化学工业 | 9957篇 |
金属工艺 | 9101篇 |
机械仪表 | 2536篇 |
建筑科学 | 3932篇 |
矿业工程 | 1537篇 |
能源动力 | 2763篇 |
轻工业 | 2332篇 |
水利工程 | 883篇 |
石油天然气 | 2355篇 |
武器工业 | 453篇 |
无线电 | 5311篇 |
一般工业技术 | 7671篇 |
冶金工业 | 2510篇 |
原子能技术 | 422篇 |
自动化技术 | 2800篇 |
出版年
2024年 | 293篇 |
2023年 | 997篇 |
2022年 | 1477篇 |
2021年 | 1758篇 |
2020年 | 1773篇 |
2019年 | 1652篇 |
2018年 | 1555篇 |
2017年 | 1989篇 |
2016年 | 1878篇 |
2015年 | 2038篇 |
2014年 | 2981篇 |
2013年 | 3088篇 |
2012年 | 3825篇 |
2011年 | 4308篇 |
2010年 | 3171篇 |
2009年 | 3205篇 |
2008年 | 2955篇 |
2007年 | 3569篇 |
2006年 | 3457篇 |
2005年 | 2724篇 |
2004年 | 2297篇 |
2003年 | 1979篇 |
2002年 | 1676篇 |
2001年 | 1440篇 |
2000年 | 1270篇 |
1999年 | 946篇 |
1998年 | 796篇 |
1997年 | 684篇 |
1996年 | 567篇 |
1995年 | 484篇 |
1994年 | 347篇 |
1993年 | 317篇 |
1992年 | 266篇 |
1991年 | 149篇 |
1990年 | 114篇 |
1989年 | 111篇 |
1988年 | 59篇 |
1987年 | 30篇 |
1986年 | 31篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1976年 | 4篇 |
1959年 | 8篇 |
1957年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 223 毫秒
81.
凝汽器铜管FeSO4镀膜监测系统的开发 总被引:1,自引:0,他引:1
为了减缓凝汽器铜管的腐蚀,通常采用FeSO4造膜保护,而FeSO4膜质量很难控制,作者通过凝汽器铜管FeSO4镀膜成膜工艺,影响因素的深入研究,建立了以电化学响应为特征的镀膜控制系统,选择了相应的传感器,形成以计算机处理为核心的监测系统,应用表明,该系统方便,可靠。 相似文献
82.
Electrochemical investigations on low-Si alloyed steels with Si content ranging from 0.25 to 3.2 wt.% were carried out in a 0.1 M NaCl borate-buffered solution (pH 8.4) in reducing conditions at 90 °C. Silicon as an alloying element was proved to degrade at first the steel ability to passivate. For longer immersion times, protective effects developed more efficiently on the steel containing 3.2 wt.% silicon. Passive layers electrochemically formed in the transpassive domain on the steel containing 3.2% Si were shown to be significantly different from those grown at rest potential. 相似文献
83.
针对大口径螺旋焊管内涂层涂敷作业时,钢管内残留的涂料挥发份如何清除的问题,介绍了一种自行设计制造的内涂层涂敷挥发份吹除装置。 相似文献
84.
85.
A Oyane M Kasahara N Ichinose Y Yokoyama M Uchida A Ito 《武汉理工大学学报(材料科学英文版)》2005,20(B12):220-222
A synthetic polymer with a laminin-apatite composite layer on its surface would be useful as a percutaneous device. The preparation of such a composite was attempted in the present study using poly( ethylene terephthalate ) (PET) and polyethylene (PE) as the synthetic polymer. PET and PE plates and those pretreated with an oxygen plasma were alternately dipped in calcium and phosphate ion solutions, and then immersed in a metastable calcium phosphate solution supplemented with laminin ( LCP solution ). The PET and PE plates pretreated with an oxygen plasma formed a uniform and continuous layer of a laminin-apatite composite on their surfaces. In contrast, the PET and PE plates that had not been pretreated with an oxygen plasma did not form a continuous layer of a laminin-apatite composite on their surfaces. The hydrophilic functional groups on the PET and PE surfaces introduced by the plasma treatment were responsible for the successful laminin-apatite coruposite coating. 相似文献
86.
Novel polyurethane insulating coatings were prepared from the reaction of glycerin‐terminated polyurethane prepolymers (GPUPs) and a blocked isocyanate curing agent (BIC). The GPUPs were prepared from the reaction of one equivalent of polycaprolactone polyol (CAPA 210) with an excess amount of 4,4′‐methylene bis(phenyl isocyanate) (MDI) and subsequent reaction of the NCO‐terminated polyurethane with glycerin. The BIC was prepared from the reaction of trimethylol propane (TMP), toluene diisocyanate (TDI) and N‐methylaniline (NMA). The polyols and curing agent were characterized by conventional methods while the curing condition was optimized via gel content measurements. The curing kinetics of the polyurethane coating were investigated and the kinetic parameters derived. The crosslink densities of the samples were determined via the equilibrium swelling method, using the Flory–Rehner equation. The relationships between the crosslink density and the electrical, physical, mechanical and dynamic mechanical properties of the coatings were also studied. Copyright © 2005 Society of Chemical Industry 相似文献
87.
A series of new alternating aromatic poly(ester‐imide)s were prepared by the polycondensation of the preformed imide ring‐containing diacids, 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl (2a) and 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl (2b) with various aromatic dihydroxy compounds in the presence of pyridine and lithium chloride. A model compound (3) was also prepared by the reaction of 2b with phenol, its synthesis permitting an optimization of polymerization conditions. Poly(ester‐imides) were fully characterized by FTIR, UV‐vis and NMR spectroscopy. Both biphenylene‐ and binaphthylene‐based poly(ester‐imide)s exhibited excellent solubility in common organic solvents such as tetrahydrofuran, m‐cresol, pyridine and dichloromethane. However, binaphthylene‐based poly(ester‐imide)s were more soluble than those of biphenylene‐based polymers in highly polar organic solvents, including N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide and dimethyl sulfoxide. From differential scanning calorimetry thermograms, the polymers showed glass‐transition temperatures between 261 and 315 °C. Thermal behaviour of the polymers obtained was characterized by thermogravimetric analysis, and the 10 % weight loss temperatures of the poly(ester‐imide)s was in the range 449–491 °C in nitrogen. Furthermore, crystallinity of the polymers was estimated by means of wide‐angle X‐ray diffraction. The resultant poly(ester‐imide)s exhibited nearly an amorphous nature, except poly(ester‐imide)s derived from hydroquinone and 4,4′‐dihydroxybiphenyl. In general, polymers containing binaphthyl units showed higher thermal stability but lower crystallinity than polymers containing biphenyl units. Copyright © 2005 Society of Chemical Industry 相似文献
88.
以C9油与甲基丙烯酰氧乙基三甲基氯化胺的共聚物P(C9-DMC)为乳化剂制备苯/丙阳离子乳胶粒,并以其为模板,利用直接包覆法制备了由17 nm左右微晶体堆成的ZrO2空心微球。所制得的样品采用FT-IR、XRD、TEM和SEM等进行了表征。 相似文献
89.
如何利用循环体诸如初值、终值、步长和下标式等数学对象的诸如恒等、正负、单调性一类的数学特征,按照严格推导出来的简单规则,绕过各种复杂的数据依赖关系图及其上诸如拓扑排序或等价变换等复杂的操作,直接从事向量化处理,这是极富实用价值的研究方向.文献[2,3,5]给出的可原形/准原形算法,以及本文的可反原形与拟离散性,正是这样的捷径.它们能使相当部分的常见循环,直接向量化. 相似文献
90.
研究了用固体润滑石墨、碳化硅、二硫化钼等填料改性的聚苯硫醚 (PPS)涂层的耐磨性能。实验结果表明 ,聚苯硫醚复合涂层具有优良的耐磨性 ;加入适量 ( 3 0 % )的石墨、碳化硅等固体润滑剂 (石墨 :碳化硅 =2∶3 ) ,可以有效提高涂层的耐磨性能 ,而二硫化钼和三氧化二铬的减摩效果更佳 相似文献