全文获取类型
收费全文 | 189554篇 |
免费 | 24499篇 |
国内免费 | 23342篇 |
专业分类
电工技术 | 18615篇 |
技术理论 | 8篇 |
综合类 | 13458篇 |
化学工业 | 38544篇 |
金属工艺 | 7754篇 |
机械仪表 | 12407篇 |
建筑科学 | 8734篇 |
矿业工程 | 2253篇 |
能源动力 | 5935篇 |
轻工业 | 13645篇 |
水利工程 | 2482篇 |
石油天然气 | 4129篇 |
武器工业 | 1954篇 |
无线电 | 28496篇 |
一般工业技术 | 20620篇 |
冶金工业 | 3950篇 |
原子能技术 | 3250篇 |
自动化技术 | 51161篇 |
出版年
2024年 | 663篇 |
2023年 | 3000篇 |
2022年 | 5061篇 |
2021年 | 7002篇 |
2020年 | 6504篇 |
2019年 | 5866篇 |
2018年 | 5388篇 |
2017年 | 7460篇 |
2016年 | 8251篇 |
2015年 | 9649篇 |
2014年 | 9371篇 |
2013年 | 12547篇 |
2012年 | 14548篇 |
2011年 | 16378篇 |
2010年 | 11861篇 |
2009年 | 11726篇 |
2008年 | 12936篇 |
2007年 | 14369篇 |
2006年 | 13798篇 |
2005年 | 11847篇 |
2004年 | 9977篇 |
2003年 | 7925篇 |
2002年 | 6081篇 |
2001年 | 4568篇 |
2000年 | 3847篇 |
1999年 | 3162篇 |
1998年 | 2598篇 |
1997年 | 2061篇 |
1996年 | 1628篇 |
1995年 | 1346篇 |
1994年 | 1191篇 |
1993年 | 892篇 |
1992年 | 724篇 |
1991年 | 577篇 |
1990年 | 491篇 |
1989年 | 360篇 |
1988年 | 278篇 |
1987年 | 172篇 |
1986年 | 169篇 |
1985年 | 226篇 |
1984年 | 197篇 |
1983年 | 139篇 |
1982年 | 195篇 |
1981年 | 97篇 |
1980年 | 96篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1977年 | 24篇 |
1976年 | 16篇 |
1959年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
We studied the rates of gelation and phase separation of poly(vinyl alcohol) (PVA) solutions in mixtures of dimethyl sulfoxide (DMSO) and water at 25 °C and found that both the rates show a maximum at a volume fraction of DMSO φDMSO=0.60 while gelation was not observed either in pure DMSO or pure water, suggesting that water-DMSO is a cononsolvent system for PVA. On the basis of the data by Cowie [Can J Chem 36 (1961) 2240] we concluded that the 1:2 stable complex between one DMSO molecule and two water molecules is the main cause of this cononsolvency. 相似文献
992.
采用两步溶胶–凝胶法制备出 ATO(掺锑氧化锡)-SiO_2复合抗静电薄膜。通过 DTA-TG、XRD、SEM 对 薄膜的结构和形貌进行了表征,结果表明:抗静电复合薄膜表面均匀致密。薄膜中 SiO_2为无定形结构,ATO 的衍射峰 与 SnO_2一致。研究了 SnO_2的含量对薄膜导电性能、结合强度和透过率的影响,发现随 SnO_2含量增加 ?(SnO_2/ SiO_2)从 5 至 12.5,薄膜的表面电阻降低(从 1010ù/□降低到 108ù/□),薄膜的结合强度下降,薄膜的透过率降低(从 89.0%降至 84.2%),结合三方面性能,得出最佳 SnO_2的配比为:?(SnO_2/ SiO_2)=10。 相似文献
993.
提出了在Visual FoxPro中开发通用信息管理系统的方法,介绍了如何使用Tree View控件来增强管理信息系统的灵活性和适应性。 相似文献
994.
995.
Poly(ethylene oxide) (PEO) star polymers were prepared by anionic polymerization of methacryloyl chloride and glyceryl trimethacrylate with sec‐butyllithium in cyclohexane. The ensuing polymers were grafted with poly(ethylene glycol) of molecular weight 400. The final product was washed with methylene chloride and analyzed with infrared spectroscopy, differential scanning calorimetry, and thermogravimetry. Star polymers of PEO were also prepared by anionic polymerization of glycidol with sec‐butyllithium in cyclohexane. The initiator was chosen so as to yield a polymer of 10,000 molecular weight. The resulting polymers were analyzed by nuclear magnetic resonance, infrared spectroscopy, and thermogravimetry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 322–327, 2003 相似文献
996.
主要论述了TMS320F240串行外设接口模块的特点,并通过与MCS5l单片机通信,实现液晶显示。 相似文献
997.
A. Kadashchuk A. Andreev H. Sitter N.S. Sariciftci Y. Skryshevski Y. Piryatinski I. Blonsky D. Meissner 《Advanced functional materials》2004,14(10):970-978
We report on photoluminescence (PL) and thermally stimulated luminescence (TSL) in highly ordered nanostructures of para‐sexiphenyl (PSP) grown by hot wall epitaxy (HWE). A low‐energy broad band is observed in the PL spectra that can be attributed to the emission from molecular aggregates. While the intrinsic exciton emission in steady‐state PL dominates at low temperatures, the emission from aggregates increases with elevating temperature and its magnitude depends sensitively on film preparation conditions. Time‐resolved PL measurements showed that the aggregate emission decays with a life‐time of ≈ 4 ns, which is approximately an order of magnitude larger than the lifetime of singlet excitons. TSL data suggests the presence of an energetically disordered distribution of localized states for charge carriers in PSP films, which results from an intrinsic disorder in this material. A low‐temperature TSL peak with the maximum at around 30 K evidences for a weak energy disorder in PSP films, and has been interpreted in terms of a hopping model of TSL in disordered organic materials. 相似文献
998.
Eiichi Haginomori Kenji Yoshimura Shunichi Kobayashi Sadanori Kaneko Takeshi Yokota Masayuki Ishikawa 《Electrical Engineering in Japan》1994,114(4):50-61
To cope with the high rate of increase of power demand in the main industrialized districts in Japan, 550-kV transmission systems covering the districts have been reinforced, with most of the main power plants connected directly to these systems. Through 550-/300-kV substations, the majority of power to the districts is supplied by 300-kV systems. To limit the excess short-circuit capacity in the 300-kV systems, they tend to be reconstructed as so-called radial networks. In radial networks with high short-circuit capacity and relatively small number of transmission lines connected to the substation busbars, the rate of rise of TRV can be far higher than standard value. This paper analyzes the transient recovery voltages (TRV) in such extra-high-voltage radial networks in Japan, together with the relevant stresses to circuit-breakers during fault clearings. Future system conditions have also been introduced. As the typical rate of rise of the TRV values, more than twice that of today's standard ones are probable. 相似文献
999.
丙烯酸酯与甲基丙烯酸酯的共聚及性能研究 总被引:22,自引:0,他引:22
采用悬浮聚合法,以丙烯酸-2-乙基-己酯与甲基丙烯酸十二酯为单体,合成了共聚型高吸油性树脂。研究了共聚单体的配比、交联剂用量、引发剂用量诸因素对高吸油性树脂的性能影响。制得的树脂可以吸其自身质量的11.8倍的煤油、14.7倍的苯、6.5倍的泵油。 相似文献
1000.
建立了高放废液中~(147)Pm的测定方法。用HDEHP萃取稀土,再用HDEHP萃淋树脂柱分离AM和稀土。然后用高效液相色谱法将~(147)Pm从Eu、Ce等其它稀土中分离出来,用液体闪烁法测量~(147)Pm的放射性活度。 相似文献