全文获取类型
收费全文 | 374483篇 |
免费 | 30181篇 |
国内免费 | 16302篇 |
专业分类
电工技术 | 21997篇 |
技术理论 | 46篇 |
综合类 | 26648篇 |
化学工业 | 62499篇 |
金属工艺 | 21883篇 |
机械仪表 | 23755篇 |
建筑科学 | 29144篇 |
矿业工程 | 12166篇 |
能源动力 | 10303篇 |
轻工业 | 25168篇 |
水利工程 | 7110篇 |
石油天然气 | 24131篇 |
武器工业 | 2969篇 |
无线电 | 40804篇 |
一般工业技术 | 41521篇 |
冶金工业 | 19035篇 |
原子能技术 | 3904篇 |
自动化技术 | 47883篇 |
出版年
2024年 | 1254篇 |
2023年 | 5547篇 |
2022年 | 9733篇 |
2021年 | 14448篇 |
2020年 | 10843篇 |
2019年 | 8818篇 |
2018年 | 10209篇 |
2017年 | 11538篇 |
2016年 | 10534篇 |
2015年 | 14518篇 |
2014年 | 18342篇 |
2013年 | 22050篇 |
2012年 | 24001篇 |
2011年 | 26611篇 |
2010年 | 23440篇 |
2009年 | 22240篇 |
2008年 | 21802篇 |
2007年 | 20750篇 |
2006年 | 21104篇 |
2005年 | 18691篇 |
2004年 | 12596篇 |
2003年 | 11242篇 |
2002年 | 10390篇 |
2001年 | 9250篇 |
2000年 | 9210篇 |
1999年 | 9906篇 |
1998年 | 7671篇 |
1997年 | 6509篇 |
1996年 | 6222篇 |
1995年 | 5118篇 |
1994年 | 4158篇 |
1993年 | 2839篇 |
1992年 | 2237篇 |
1991年 | 1701篇 |
1990年 | 1328篇 |
1989年 | 1072篇 |
1988年 | 896篇 |
1987年 | 543篇 |
1986年 | 428篇 |
1985年 | 269篇 |
1984年 | 214篇 |
1983年 | 152篇 |
1982年 | 135篇 |
1981年 | 83篇 |
1980年 | 103篇 |
1979年 | 52篇 |
1978年 | 21篇 |
1977年 | 25篇 |
1976年 | 33篇 |
1972年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
982.
Li Z.-M. Landheer D. Veilleux M. Conn D.R. Surridge R. Xu J.M. McDonald R.I. 《Photonics Technology Letters, IEEE》1992,4(5):473-476
The authors have developed a 2-D device simulator for heterostructure metal-semiconductor-metal (MSM) photodetectors. They have incorporated a model of multilayer optics into the simulator and used it to analyze the temporal response of a resonant-cavity enhanced heterostructure with a confining buffer layer and a distributed Bragg reflector (DBR). The authors show that through fine tuning the layer thicknesses, optical resonance enhancement of the light absorption can be obtained 相似文献
983.
984.
An aromatic diamine, CMOMDA, was synthesized and used as a chain extender for reaction injection molding (RIM) polyurethane–urea. The morphology and properties of CMOMDA-, DETDA-, and MDA-extended poly(ether–urethane–urea)s (PEUUs) were measured by IR, DSC, DMS, SEM, and tensile testing apparatus. Well-matched values of Ch and Xut,b/Ch were necessary for aromatic diamine-extended PEUU. DSC and SEM showed that the aggregation state of hard segments might undergo some changes with increasing hard-segment content. © 1994 John Wiley & Sons, Inc. 相似文献
985.
介绍了水包油型多彩涂料的组成、各组份的作用、生产工艺路线和工艺参数的选择。对多彩涂料的施工机具和方法作了简单介绍。 相似文献
986.
��Ȼ����������ϵͳ�ļ춨��У 总被引:6,自引:3,他引:3
当前我国管道天然气计量系以体积表示,就其计量器具而言,差压式流量计、容积式流量计和速变式流量计都有,但大流量计量大多仍采用标准孔板差压式流量计,其流量计量标准招待我国SY/T6143-1996《天然气流量的标准孔板计量方法》。文章介绍目前常用的三种流量计的优缺点比较;天然气标准孔板差压式流量计算机自动计量系统的检定,其中包括:标准孔板节流装置,静压、差压变送器、温度传感器、数据采集系统等组件的检定;以及计量器具的正确使用和维护。最后,文章指出目前流量计量的发展主要是二次仪表的发展,籍助应用计算机大大提高流量法的测量范围和准确度,但对用户来说,应选择性/价比合适的仪表,并要考虑所选用仪表要便于检定、维护,同时,计量检定部门则应跟上发展,为广大用户提供技术支持。 相似文献
987.
988.
M Pan J Suárez de Lezo A Medina M Romero E Hernández J Segura F Melian F Wangüemert M Landin F Benítez M Amat F Velasco A Torres 《Canadian Metallurgical Quarterly》1997,80(10):1336-1338
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation. 相似文献
989.
990.
K Hashimoto M Noshiro S Ohno T Kawamoto H Satakeda Y Akagawa K Nakashima A Okimura H Ishida T Okamoto H Pan M Shen W Yan Y Kato 《Canadian Metallurgical Quarterly》1997,1355(3):303-314
Malignant human gliomas are the most common forms of primary tumors in the central nerve system. Due to their location and invasive nature, treatment so far has been mainly palliative. Thus, understanding the molecular detail of tumor transformation and progression is crucial for developing effective therapeutic strategy for this fetal tumor. Among the genetic alternations found in these tumors, p53 inactivation and PDGF/PDGFR activation represent the early events, and the loss of chromosome 10 and gene amplification and rearrangement of EGFR represent the late events. Studies with both glioma cell lines and primary tumor tissues have strongly suggested that TGF-alpha and EGFR function as an important autocrine loop in supporting proliferation of human glioma, especially in high grade glioma, since elevated TGF-alpha expression is also found in these high grade tumors. Furthermore, down regulation of the expression of TGF-alpha by antisense constructs has been shown to inhibit several types of human tumor cell growth including glioma. Other means of therapeutic approaches using this autocrine loop as a target also include the use of monoclonal antibodies and their cytotoxic conjugated. Considerable understanding of the EGFR-mediated signal transduction pathways has become available recently, which including GRB2/mSOS1 mediated MAP kinase activation; JAK/STATs pathway; PLC-gamma pathway. However, much work still needs to be done before a specific component of these pathways can be applied for effective control of tumor growth in the clinic. 相似文献