首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   157061篇
  免费   14128篇
  国内免费   7467篇
电工技术   9548篇
技术理论   8篇
综合类   10610篇
化学工业   25403篇
金属工艺   9654篇
机械仪表   11000篇
建筑科学   12985篇
矿业工程   5220篇
能源动力   4456篇
轻工业   10334篇
水利工程   3020篇
石油天然气   10250篇
武器工业   1416篇
无线电   17947篇
一般工业技术   17783篇
冶金工业   7435篇
原子能技术   1695篇
自动化技术   19892篇
  2024年   719篇
  2023年   2812篇
  2022年   5179篇
  2021年   6955篇
  2020年   5390篇
  2019年   4306篇
  2018年   4596篇
  2017年   5351篇
  2016年   4850篇
  2015年   6784篇
  2014年   8196篇
  2013年   9746篇
  2012年   10494篇
  2011年   11419篇
  2010年   9895篇
  2009年   9505篇
  2008年   9307篇
  2007年   8564篇
  2006年   8574篇
  2005年   7280篇
  2004年   4611篇
  2003年   4145篇
  2002年   3877篇
  2001年   3533篇
  2000年   3269篇
  1999年   3585篇
  1998年   2845篇
  1997年   2359篇
  1996年   2301篇
  1995年   1950篇
  1994年   1583篇
  1993年   1082篇
  1992年   881篇
  1991年   647篇
  1990年   493篇
  1989年   414篇
  1988年   321篇
  1987年   207篇
  1986年   169篇
  1985年   102篇
  1984年   75篇
  1983年   67篇
  1982年   61篇
  1981年   44篇
  1980年   44篇
  1979年   28篇
  1976年   4篇
  1967年   3篇
  1959年   5篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
  Qing  Xu  Bin  Yu  Yang  Zhan  Wei  Zhao  Yu  Zheng  Jun  Ji  Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability...  相似文献   
32.
33.
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   
34.
35.
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   
36.
37.
In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota.  相似文献   
38.
39.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention.  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号