全文获取类型
收费全文 | 99034篇 |
免费 | 10960篇 |
国内免费 | 6721篇 |
专业分类
电工技术 | 8145篇 |
技术理论 | 2篇 |
综合类 | 8830篇 |
化学工业 | 14075篇 |
金属工艺 | 6238篇 |
机械仪表 | 7112篇 |
建筑科学 | 8186篇 |
矿业工程 | 3408篇 |
能源动力 | 2814篇 |
轻工业 | 8265篇 |
水利工程 | 2691篇 |
石油天然气 | 4369篇 |
武器工业 | 1213篇 |
无线电 | 11654篇 |
一般工业技术 | 9769篇 |
冶金工业 | 4089篇 |
原子能技术 | 1450篇 |
自动化技术 | 14405篇 |
出版年
2024年 | 390篇 |
2023年 | 1736篇 |
2022年 | 3595篇 |
2021年 | 4850篇 |
2020年 | 3607篇 |
2019年 | 2787篇 |
2018年 | 2815篇 |
2017年 | 3294篇 |
2016年 | 2948篇 |
2015年 | 4547篇 |
2014年 | 5638篇 |
2013年 | 6715篇 |
2012年 | 7706篇 |
2011年 | 8334篇 |
2010年 | 7486篇 |
2009年 | 7389篇 |
2008年 | 7234篇 |
2007年 | 6744篇 |
2006年 | 6043篇 |
2005年 | 4900篇 |
2004年 | 3290篇 |
2003年 | 2410篇 |
2002年 | 2278篇 |
2001年 | 2055篇 |
2000年 | 1698篇 |
1999年 | 1254篇 |
1998年 | 869篇 |
1997年 | 712篇 |
1996年 | 663篇 |
1995年 | 602篇 |
1994年 | 477篇 |
1993年 | 368篇 |
1992年 | 251篇 |
1991年 | 232篇 |
1990年 | 169篇 |
1989年 | 129篇 |
1988年 | 104篇 |
1987年 | 72篇 |
1986年 | 53篇 |
1985年 | 40篇 |
1984年 | 21篇 |
1983年 | 34篇 |
1982年 | 27篇 |
1981年 | 23篇 |
1980年 | 38篇 |
1979年 | 23篇 |
1976年 | 4篇 |
1965年 | 3篇 |
1959年 | 16篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
32.
33.
34.
This calibration device of radio comprehensive tester is studied and established in this paper. It solves the verification and
calibration of a large number of general-purpose radio comprehensive testers. The calibration device consists of four calibration sub-
systems and calibration software system, including RF generator, audio generator, audio analyzer and RF analyzer. It also researches
on the configuration of standard equipment and analyzes the uncertainty of the calibration devices, ensuring accurate and reliable val-
ue transfer. 相似文献
35.
36.
对于郑州航空港老丈八沟桥桩基工程拆除,选择了全套筒拔桩法、冲击破桩法和钢护筒明挖法3种不同的方案,对各方案的工期和造价进行比较,优选了钢护筒明挖法,对钢护筒结构进行了设计,对施工工序进行了合理性分析。 相似文献
37.
Kazuo Tsubota Stephen C. Pflugfelder Zuguo Liu Christophe Baudouin Hyo Myung Kim Elisabeth M. Messmer Friedrich Kruse Lingyi Liang Jimena Tatiana Carreno-Galeano Maurizio Rolando Norihiko Yokoi Shigeru Kinoshita Reza Dana 《International journal of molecular sciences》2020,21(23)
Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint. 相似文献
38.
39.
To realize joint optimization of spatial diversity and equalization combining in the intersymbol interference (ISI) channel, an iterative equalization combining algorithm is proposed. The proposed algorithm uses the coefficients of Turbo equalization to calculate the combination weights without estimating the signal to noise ratio in each diversity branch. The equalized symbols from different diversity branches are combined, and the extrinsic information output from the decoder is fed back to the equalizers, so as to exchange soft information between the equalizers and the decoder. The performance of the proposed algorithm is analyzed using the extrinsic information transfer (EXIT) chart and verified by simulations. Results show that our approach fully exploits time domain information from the multipath channel and spatial domain information from multi receiving antennas, which efficiently improve the performance of the receiver in the severe ISI channel. 相似文献
40.
在模具加工刀路编制时,很多用户会将C reo设计模型导入M aster C A M、C im atron等软件中进行加工刀路编制,往往引起很多数据转换的问题。文中采用C reo软件的一个加工模块N C A ssem bly进行无缝衔接,完成刀路编制。并结合一个实例进行了工艺分析,进而实现粗加工和精加工。 相似文献