全文获取类型
收费全文 | 228295篇 |
免费 | 18264篇 |
国内免费 | 9112篇 |
专业分类
电工技术 | 12437篇 |
技术理论 | 24篇 |
综合类 | 14174篇 |
化学工业 | 38829篇 |
金属工艺 | 13142篇 |
机械仪表 | 14529篇 |
建筑科学 | 17648篇 |
矿业工程 | 7509篇 |
能源动力 | 6429篇 |
轻工业 | 13443篇 |
水利工程 | 3587篇 |
石油天然气 | 16649篇 |
武器工业 | 1651篇 |
无线电 | 25132篇 |
一般工业技术 | 27334篇 |
冶金工业 | 12813篇 |
原子能技术 | 2248篇 |
自动化技术 | 28093篇 |
出版年
2024年 | 992篇 |
2023年 | 3805篇 |
2022年 | 6488篇 |
2021年 | 9051篇 |
2020年 | 7080篇 |
2019年 | 6016篇 |
2018年 | 6733篇 |
2017年 | 7543篇 |
2016年 | 6757篇 |
2015年 | 8863篇 |
2014年 | 11252篇 |
2013年 | 13274篇 |
2012年 | 14216篇 |
2011年 | 15452篇 |
2010年 | 13427篇 |
2009年 | 12686篇 |
2008年 | 12356篇 |
2007年 | 11864篇 |
2006年 | 12360篇 |
2005年 | 10764篇 |
2004年 | 7273篇 |
2003年 | 6242篇 |
2002年 | 5474篇 |
2001年 | 4897篇 |
2000年 | 5451篇 |
1999年 | 6450篇 |
1998年 | 5442篇 |
1997年 | 4456篇 |
1996年 | 4192篇 |
1995年 | 3503篇 |
1994年 | 2815篇 |
1993年 | 1968篇 |
1992年 | 1540篇 |
1991年 | 1227篇 |
1990年 | 936篇 |
1989年 | 741篇 |
1988年 | 538篇 |
1987年 | 338篇 |
1986年 | 279篇 |
1985年 | 196篇 |
1984年 | 139篇 |
1983年 | 114篇 |
1982年 | 124篇 |
1981年 | 98篇 |
1980年 | 70篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
961.
962.
筛查基因突变的新技术——循环双脱氧指纹图谱法及其应用 总被引:2,自引:0,他引:2
建立了适用于大批量标本基因突变筛查的双脱氧指纹图谱法即ddF。该技术民测定DNA序列的双脱氧末端终止法及SSCP二者长处于一身,即只作一个双脱氧末端终止反应,然后将反应产物在与SSCP相同的电泳条件下进行聚丙烯酰胺凝胶电泳,这样有突变的样品不会漏检,阳性检出率高达100%。 相似文献
963.
研制成功了128×128元PtsiIRCCD,获得了清晰的室温目标热像。文章叙述了该摄像机驱动逻辑电路的设计、驱动方式的研究和视频信号、数字信号的处理。 相似文献
964.
965.
锌基复合材料研究进展 总被引:20,自引:0,他引:20
评述了锌基复合材料的发展和研究概况,着重介绍了锌基复合材料的制备工艺和性能研究现状,最后对锌基复合材料的研究方向和应用前景提出了一些设想和展望。 相似文献
966.
967.
Y. Liu W. Zhu O. K. Tan X. Yao Y. Shen 《Journal of Materials Science: Materials in Electronics》1996,7(4):279-282
A low-temperature plasma-enhanced chemical vapour deposition (PECVD) technique has been employed to produce ultrafine tin oxide powders. The structural features and phase transition of this material have been characterized using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction, infrared spectroscopy (IR) and transmission electron microscopy (TEM). The oxygen absorption behaviour and gassensing properties have been investigated by electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and electrical measurements. Thick film gas sensors made from such ultrafine SnO2 powders yield better sensitivities than those of normal undoped SnO2 gas sensors. A gas-sensing reaction mechanism is also proposed. 相似文献
968.
液相对流对固液界面稳定性的影响 总被引:1,自引:0,他引:1
以模型合金丁二腈-乙醇的强制性晶体生长为基础,利用自行研制的液相对流驱动装置,详细考查了液相自然对流及强迫对流作用下,模型合金平界面失稳的动态生长过程,证实了液相的流动加快了液相温度与浓度分布的均匀化,从而增强了液/固界面的稳定性。并且随流动速度的增加,界面稳定性提高。 相似文献
969.
C-reactive protein (CRP) is a prototypic acute phase protein in human and rabbit. Although it is structurally and functionally conserved from invertebrate to human, there are species-specific differences in patterns of expression and putative function. To further investigate the biological significance, regulation, and evolution of CRP, we isolated Xenopus CRP and subsequently derived and sequenced corresponding cDNA and the genomic clones. The structure and expression of Xenopus CRP were also compared to those of the other CRPs. Analyses of the amino acid sequence and the nucleotide sequence reveal that the mature Xenopus CRP is a 222-amino acid protein preceded by a 16-residue signal peptide. During development, Xenopus CRP is expressed, only when the liver appears, and therefore is not likely to play a role in early embryonic development. Compared to other species, Xenopus CRP is present at an intermediate low level of < 1 microgram/ml in the normal serum. Unlike human and rabbit CRP, Xenopus CRP is not induced by turpentine or heatshock treatment. The heatshock consensus sequence (Woo, P., Korenberg, J. R., and Whitehead, A. S. (1985) J. Biol. Chem. 265, 4136-4142) are not present in the Xenopus CRP gene. It is suggested that Xenopus CRP represents a transitional period in CRP evolution when host defenses switched from primitive innate immunity to a much more complex immune system. The constitutive functions of CRP gradually became less essential as the result of the development of a complex immune system. 相似文献
970.
Complements in serum and middle ear effusion were determined in 20 patients with secretory otitis media, and compared with those in the normal controls. The C5 and C1-INH in serum of the patients were significantly higher. On the contrary, C9 and B factor (Bf) were significantly lower, and the circulatory immunocomplex was also higher. In patients with secretory otitis media, the middle ear effusion levels of C3, C4 and C5 were significantly lower, and Bf and immunocomplex were significantly higher than those in serum. The results suggest that the ability of complements in clearing immunocomplex is low. Therefore, the immunocomplex may deposit in the mucosa of the middle ear. Thus the permeability of capillary will be increased, and the middle ear effusion occurs. 相似文献