全文获取类型
收费全文 | 19574篇 |
免费 | 2555篇 |
国内免费 | 1464篇 |
专业分类
电工技术 | 1977篇 |
综合类 | 2006篇 |
化学工业 | 2435篇 |
金属工艺 | 1120篇 |
机械仪表 | 1440篇 |
建筑科学 | 1411篇 |
矿业工程 | 691篇 |
能源动力 | 558篇 |
轻工业 | 1842篇 |
水利工程 | 523篇 |
石油天然气 | 671篇 |
武器工业 | 320篇 |
无线电 | 2100篇 |
一般工业技术 | 1645篇 |
冶金工业 | 1798篇 |
原子能技术 | 329篇 |
自动化技术 | 2727篇 |
出版年
2024年 | 129篇 |
2023年 | 432篇 |
2022年 | 962篇 |
2021年 | 1264篇 |
2020年 | 870篇 |
2019年 | 625篇 |
2018年 | 626篇 |
2017年 | 691篇 |
2016年 | 589篇 |
2015年 | 925篇 |
2014年 | 1068篇 |
2013年 | 1242篇 |
2012年 | 1545篇 |
2011年 | 1541篇 |
2010年 | 1443篇 |
2009年 | 1301篇 |
2008年 | 1296篇 |
2007年 | 1270篇 |
2006年 | 1075篇 |
2005年 | 950篇 |
2004年 | 643篇 |
2003年 | 432篇 |
2002年 | 398篇 |
2001年 | 377篇 |
2000年 | 326篇 |
1999年 | 149篇 |
1998年 | 402篇 |
1997年 | 226篇 |
1996年 | 162篇 |
1995年 | 103篇 |
1994年 | 96篇 |
1993年 | 93篇 |
1992年 | 24篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 28篇 |
1988年 | 29篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 15篇 |
1978年 | 4篇 |
1977年 | 36篇 |
1976年 | 90篇 |
1959年 | 7篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
11.
The low energy density of supercapacitors, especially supercapacitors based on aqueous electrolytes, is the main factor limiting their application, and the energy density is closely related to the operating potential window of the supercapacitor. The polymer electrolyte is the main contributor to the safe operation and good ion conductivity of the supercapacitor. In this study, a crosslinked quaternized poly(arylene ether sulfone) (PAES) membrane was prepared via crosslinking during membrane formation with a thermal-only treatment and applied in an electric double-layer capacitor (EDLC). The pre-prepared PAES membrane formed a polymer electrolyte with 1 mol/L Li2SO4 and was then fabricated into an EDLC single cell. The properties of both the membrane and ELDC were investigated. The preferred cPAES-N-0.2 polymer electrolyte showed an ionic conductivity of 1.18 mS/cm. The optimized EDLC exhibited a single-electrode gravimetric capacitance of 104.92 F/g at a current density of 1.0 A/g and a high operating potential window (1.5 V); it, thereby, achieved a high energy density of 8.20 W h/kg. The EDLC also exhibited excellent cycling properties over 3000 charge–discharge cycles. The crosslinked structures promoted the tensile strength and thermal stability of the PAES membranes; this was accompanied by a slight decrease in the ionic conductivity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47759. 相似文献
12.
13.
分析了设备对PCB电镀过程中孔中镀液更新之影响,为有效地利用设备条件改善孔中镀液的更新提供了一些方法及理论数据。 相似文献
14.
15.
基于联系国内外智能交通系统研究的具体实际,提出了建立城市智能交通实验研究中心的设想,并结合一个集成了视频和线圈信息采集方式的实验研究中心简单设计方案,对其所具有的基本功能作了初步研究和探讨。该系统兼具促进交流和有关培训等社会职能,可以作为国家智能交通事业发展过程中一种特殊的示范工程。 相似文献
16.
17.
CMP系统技术与市场 总被引:3,自引:1,他引:2
葛劢冲 《电子工业专用设备》2003,32(1):17-24
概述了CMP系统技术的发展历史、发展趋势以及在IC生产中的重要性,介绍了国外CMP设备主要制造厂家的设备型号和性能及CMP设备市场分布和需求,阐述了CMP系统技术的基础研究、关键技术和国内研究概况。 相似文献
18.
KJ Shon M Grilley R Jacobsen GE Cartier C Hopkins WR Gray M Watkins DR Hillyard J Rivier J Torres D Yoshikami BM Olivera 《Canadian Metallurgical Quarterly》1997,36(31):9581-9587
A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers). 相似文献
19.
The mycobacterial embCAB operon encodes arabinosyl transferases, putative targets of the antimycobacterial agent ethambutol (EMB). Mutations in embB lead to resistance to EMB in Mycobacterium tuberculosis. The basis for natural, intrinsic resistance to EMB in nontuberculous mycobacteria (NTM) is not known; neither is the practical implication of resistance to EMB in the absence of embB mutations in M. tuberculosis well understood. The conserved embB resistance-determining region (ERDR) of a collection of 13 strains of NTM and 12 EMB-resistant strains of M. tuberculosis was investigated. Genotypes were correlated with drug susceptibility phenotypes. High-level natural resistance to EMB (MIC, . or =64 microg/ml) was associated with a variant amino acid motif in the ERDR of M. abscessus, M. chelonae, and M. leprae. Transfer of the M. abscessus emb allele to M. smegmatis resulted in a 500-fold increase in the MICs. In M. tuberculosis, embB mutations were associated with MICs of > or =20 microg/ml while resistance not associated with an ERDR mutation generally resulted in MICs of < or =10 microg/ml. These data further support the notion that the emb region determines intrinsic and acquired resistance to EMB and might help in the reassessment of the current recommendations for the screening and treatment of infections with EMB-resistant M. tuberculosis and NTM. 相似文献
20.