全文获取类型
收费全文 | 90623篇 |
免费 | 7897篇 |
国内免费 | 5303篇 |
专业分类
电工技术 | 3796篇 |
技术理论 | 4篇 |
综合类 | 9728篇 |
化学工业 | 12538篇 |
金属工艺 | 6448篇 |
机械仪表 | 5786篇 |
建筑科学 | 18784篇 |
矿业工程 | 3587篇 |
能源动力 | 2271篇 |
轻工业 | 5040篇 |
水利工程 | 2360篇 |
石油天然气 | 4365篇 |
武器工业 | 891篇 |
无线电 | 5456篇 |
一般工业技术 | 9999篇 |
冶金工业 | 3653篇 |
原子能技术 | 529篇 |
自动化技术 | 8588篇 |
出版年
2024年 | 367篇 |
2023年 | 1301篇 |
2022年 | 2445篇 |
2021年 | 2697篇 |
2020年 | 2701篇 |
2019年 | 2171篇 |
2018年 | 2083篇 |
2017年 | 2629篇 |
2016年 | 2741篇 |
2015年 | 3012篇 |
2014年 | 5532篇 |
2013年 | 4660篇 |
2012年 | 6161篇 |
2011年 | 6857篇 |
2010年 | 5304篇 |
2009年 | 5752篇 |
2008年 | 5247篇 |
2007年 | 6225篇 |
2006年 | 5678篇 |
2005年 | 4947篇 |
2004年 | 4053篇 |
2003年 | 3662篇 |
2002年 | 3096篇 |
2001年 | 2588篇 |
2000年 | 2232篇 |
1999年 | 1853篇 |
1998年 | 1465篇 |
1997年 | 1240篇 |
1996年 | 943篇 |
1995年 | 806篇 |
1994年 | 763篇 |
1993年 | 495篇 |
1992年 | 456篇 |
1991年 | 369篇 |
1990年 | 295篇 |
1989年 | 214篇 |
1988年 | 163篇 |
1987年 | 86篇 |
1986年 | 64篇 |
1985年 | 73篇 |
1984年 | 54篇 |
1983年 | 54篇 |
1982年 | 65篇 |
1981年 | 21篇 |
1980年 | 64篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
采用独特的分离方法和途径,综合使用多种质谱分析技术,如电子轰击谱(EI/MS)、场解吸谱(FD/MS)、快速原子轰击谱(FAB/MS)、色/质联用等,对高档齿轮油的主剂-含磷极压剂的结构组成进行了较为详尽的分析研究,提出了复酯胺盐的结构组成。 相似文献
32.
33.
Keizo Uematsu Masayori Miyashita Jin-Young Kim Zenji Kato Nozomu Uchida 《Journal of the American Ceramic Society》1991,74(9):2170-2174
Green bodies prepared by compaction of alumina granules were made transparent by an immersion liquid technique, and the internal structure was characterized with an optical microscope to study the effect of forming pressure on the internal structure. Clear images obtained by the technique provide more detailed information than other existing methods for structures ranging from one to tens of micrometers. Intergranular pores were present between unfractured granules. Their sizes and concentration tended to decrease with increasing forming pressure. However, pores were clearly present even in the green body prepared at 600 MPa. A rod- and needlelike feature was also found and was concluded to correspond to a high-density region. The significance of large pores and high-density regions on processing as well as the details of the technique is discussed. 相似文献
34.
35.
John E. Lowther 《Journal of the American Ceramic Society》2002,85(1):55-58
Diamond and BN have common relatively soft precursor structures that are hexagonal. Electronic structure calculations have now revealed subtle energy differences between the two materials. Another hard material, stishovite, also has a relatively soft precursor phase, quartz, and here again electronic structure calculations have given insight into the nature of the phase transformation. On the other hand, with boron-related materials, the main focus is to connect basic icosahedra structures to produce a hard material. The structural aspects of these materials are examined and possible consequences for low- and high-coordination ultrahard nitrides considered. 相似文献
36.
本文针对结晶器与铸锭作相对移动的电渣重熔过程中对渣系的高温强度及塑性的要求,对10种CaF_2-CaO-MgO-Al_2O_3-SiO_2渣组成进行了渣的高温强度及塑性的测定,建立了渣组成—渣的岩相结构—渣高温强度及塑性间的对应关系,并选择出较合适的成分范围为CaF_2 35~60%,CaO 10~25%,Al_2O_3 10~20%,SiO_25~15%,MgO≈5%。对其中一个成分的渣进行了电渣热穿孔熔铸中空锭生产实验,并取得了良好的表面质量。 相似文献
37.
The object of this paper is to demonstrate the usefulness of the transalkylation reaction for determining chemical structural features of products derived from coal. For example, the method is applied to derivatized coals, coals modified by thermolysis, and materials physically or chemically separated from coals. Data are presented for the pyridine soluble and insoluble parts of two coals, an O-methylated coal, a Birch reduced coal, a solvent refined coal, and a coke. Similarities and differences in chemical make-up of these materials are discussed. 相似文献
38.
As part of a study of the possible application of polymerisable Langmuir-Blodgett (LB) films as ultra-fine-line e-beam resists, an investigation of the variation of film structure of 22-tricosenoic acid with differing deposition conditions has been made. Unexpected effects with significant implications for deposition speed and resist sensitivity have been observed, and the new techniques for film characterisation developed during the investigation have resulted in a revised model of deposition explaining the observed independence of the disorder causing optical scattering and the macroscopic features observed by polarised microscopy. 相似文献
39.
高速短程纺技术能生产三维卷曲短纤维,该技术的关键之一是热流体喷射装置。本文介绍了热流体喷射装置的演变与特点及它的加工机理和某些已应用的实际装置。 相似文献
40.
StructureandMagneticPropertiesofLaCo_(13-X)M_XIntermetallicCompoundsWUJianMin;LIFeng;TAILiChiandZHEMGQunStructureandMagneticP... 相似文献