全文获取类型
收费全文 | 127188篇 |
免费 | 13342篇 |
国内免费 | 9038篇 |
专业分类
电工技术 | 10558篇 |
技术理论 | 3篇 |
综合类 | 11171篇 |
化学工业 | 17243篇 |
金属工艺 | 8084篇 |
机械仪表 | 9025篇 |
建筑科学 | 10478篇 |
矿业工程 | 4180篇 |
能源动力 | 4087篇 |
轻工业 | 10122篇 |
水利工程 | 3495篇 |
石油天然气 | 5410篇 |
武器工业 | 1683篇 |
无线电 | 14986篇 |
一般工业技术 | 12871篇 |
冶金工业 | 4773篇 |
原子能技术 | 2050篇 |
自动化技术 | 19349篇 |
出版年
2024年 | 584篇 |
2023年 | 1650篇 |
2022年 | 3602篇 |
2021年 | 5169篇 |
2020年 | 3756篇 |
2019年 | 3045篇 |
2018年 | 3251篇 |
2017年 | 3864篇 |
2016年 | 3614篇 |
2015年 | 5352篇 |
2014年 | 6878篇 |
2013年 | 7999篇 |
2012年 | 9634篇 |
2011年 | 10413篇 |
2010年 | 9859篇 |
2009年 | 9560篇 |
2008年 | 9800篇 |
2007年 | 9474篇 |
2006年 | 8816篇 |
2005年 | 7094篇 |
2004年 | 5214篇 |
2003年 | 4095篇 |
2002年 | 4114篇 |
2001年 | 3443篇 |
2000年 | 2732篇 |
1999年 | 1746篇 |
1998年 | 963篇 |
1997年 | 817篇 |
1996年 | 658篇 |
1995年 | 539篇 |
1994年 | 415篇 |
1993年 | 321篇 |
1992年 | 228篇 |
1991年 | 185篇 |
1990年 | 130篇 |
1989年 | 123篇 |
1988年 | 76篇 |
1987年 | 70篇 |
1986年 | 69篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 31篇 |
1982年 | 22篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1979年 | 9篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1959年 | 23篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
A novel fully conjugated polymer containing 1,10‐phenanthroline (DAPcDOD) was first synthesized by the polycondensation of 2,7‐dimethyl‐2,4,6‐octatriene‐1,8‐dial with 5,6‐diamine‐1,10‐phenanthroline. Three polymeric complexes were first prepared by the reaction of DAPcDOD with NiSO4, CoCl2, and FeSO4, respectively. The structures of the polymer and the complexes were characterized by IR, 1H‐NMR, and elemental analysis. The magnetic behaviors of these complexes were measured as a function of magnetic field strength (0–50 kOe) at 5 K and as a function of temperature (5–300 K) at a magnetic field strength of 30 kOe. The results show that DAPcDOD–Ni2+ and DAPcDOD–Co2+ were soft ferromagnets, whereas DAPcDOD–Fe2+ exhibited the features of an antiferromagnet. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
32.
33.
Woo Yong Sung Seung Min Lee Wal Jun Kim Jong Girl Ok Ho Young Lee Yong Hyup Kim 《Diamond and Related Materials》2008,17(6):1003-1007
Complementary electroplating combined with electrophoresis enhanced the field emission characteristics of emitters by improving the adhesions between CNT emitters and substrate. The emitting current of the CNT emitters prepared by our combined method increased nine times higher than that of CNT emitters prepared by electrophoresis only, since electroplating improved the adhesion of CNT emitters. During the life-time measurement for 10 h, the emitting current of CNT emitters fabricated by electrophoresis only was drastically decreased to 13% of the initial current, while that prepared by the combination of electrophoresis and successive electroplating decreased to 64% of the initial current. We suggest that our method is a promising approach for the efficient fabrication of reliable CNT emitters. 相似文献
34.
35.
化学镀Ni—P镀层的X射线衍射研究 总被引:2,自引:0,他引:2
根据X射线衍射分析结果,对化学镀高P(含P>11wt%或19at%)Ni-P镀层加热时效时,镀层成分和加热温度对结构转变的影响作了研究,结果表明,高P共晶、过共晶(含P>11wt%或19at%)合金的结构转变有如下特征:(1)相同加热时效条件下,Ni-P合金的结构转变与成分有密切关系:(2)对同一成分的过共晶合金,Ni-P合金的结构转变与时效温度密切相关;(3)过共晶合金在290~360℃温度范围内时效处理,出现Ni_xP_y介稳相,X射线衍射分析认为Ni_xP_y为Ni_(12)P_5。 相似文献
36.
Plasmapropertiesoflaser-ablatedSttargetinairWangXiang-Tai(王象泰);ManBao-Yuan(满宝元);WangGong-Tang(王公堂);FanXi-Jun(樊锡君);WangJun(王军)... 相似文献
37.
Tetsuhiko Kobayashi Nolven Guilhaume Jun Miki Naoyuki Kitamura Masatake Haruta 《Catalysis Today》1996,32(1-4):171-175
In an attempt to develop new catalysts for the formation of formaldehyde from methane, the promotion effect of Fe on SiO2 and that of Sn on WO3 have been studied. The formation of formaldehyde on silica can be appreciably enhanced by the impregnation of Fe, as far as iron loadings are kept below 0.1 atom.% (Fe/Si × 100). In the case of Sn---W---Ox catalysts, both the addition of Sn to WO3, and that of W on SnO2 were effective to the selective formaldehyde formation. Absorption spectra (UV-Vis) and ESR measurements revealed that tetrahedrally coordinated Fe3+ in the silica network plays an important role in the formation of formaldehyde. A thin surface layer consisting of W and Sn oxides can account for the selective formaldehyde formation on the Sn---W---Ox catalysts. 相似文献
38.
39.
Xiaolin Hu Jun Wang 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2007,37(3):528-539
This paper presents a recurrent neural-network model for solving a special class of general variational inequalities (GVIs), which includes classical VIs as special cases. It is proved that the proposed neural network (NN) for solving this class of GVIs can be globally convergent, globally asymptotically stable, and globally exponentially stable under different conditions. The proposed NN can be viewed as a modified version of the general projection NN existing in the literature. Several numerical examples are provided to demonstrate the effectiveness and performance of the proposed NN. 相似文献
40.
介绍了造成铁路油槽车底油收不尽的原因,一是节约意识差;二是设备设施陈旧或维护不够;三是操作不当。提出了增强节约意识,挖掘设备潜力,采用合理的吸油方法的对策。 相似文献