全文获取类型
收费全文 | 80424篇 |
免费 | 13065篇 |
国内免费 | 15179篇 |
专业分类
化学 | 37787篇 |
晶体学 | 1470篇 |
力学 | 3151篇 |
综合类 | 1716篇 |
数学 | 7319篇 |
物理学 | 21398篇 |
无线电 | 35827篇 |
出版年
2024年 | 323篇 |
2023年 | 1138篇 |
2022年 | 2415篇 |
2021年 | 2584篇 |
2020年 | 2379篇 |
2019年 | 2282篇 |
2018年 | 2181篇 |
2017年 | 2743篇 |
2016年 | 2767篇 |
2015年 | 3610篇 |
2014年 | 4339篇 |
2013年 | 5692篇 |
2012年 | 6113篇 |
2011年 | 6617篇 |
2010年 | 5921篇 |
2009年 | 6305篇 |
2008年 | 6735篇 |
2007年 | 6485篇 |
2006年 | 6110篇 |
2005年 | 5256篇 |
2004年 | 4311篇 |
2003年 | 3305篇 |
2002年 | 3231篇 |
2001年 | 3219篇 |
2000年 | 3006篇 |
1999年 | 1716篇 |
1998年 | 937篇 |
1997年 | 834篇 |
1996年 | 759篇 |
1995年 | 631篇 |
1994年 | 613篇 |
1993年 | 650篇 |
1992年 | 515篇 |
1991年 | 391篇 |
1990年 | 375篇 |
1989年 | 359篇 |
1988年 | 278篇 |
1987年 | 233篇 |
1986年 | 203篇 |
1985年 | 146篇 |
1984年 | 154篇 |
1983年 | 142篇 |
1982年 | 97篇 |
1981年 | 115篇 |
1980年 | 88篇 |
1979年 | 68篇 |
1978年 | 56篇 |
1977年 | 31篇 |
1976年 | 23篇 |
1965年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
943.
L. Fernandes C. Pagano Gonçalves da Silva 《Journal of Radioanalytical and Nuclear Chemistry》1993,172(2):313-318
The radiopharmaceutical201TlCl(thallium-201 chloride) is used in nuclear medicine for myocardial visualization. The solution of201TlCl was prepared using201Tl obtained by irradiating a natural mercury target with protons from the CV-28 cyclotron installed at IPEN-CNEN/SP. This solution was subjected to different quality control processes required for its use in medicine. Some of these controls concerned the determination of the radionuclidic impurities:200Tl,202Tl and203Hg; the chemical identification of201Tl+; the hydrazine concentration, mercury contamination and the presence of phosphate. Furthermore. the biological distribution in Wistar rats and tests for sterility, pyrogenicity and toxicity were carried out. It was verified that the solution obtained was in the form of thallous chloride. This radiopharmaceutical gave good heart images in animals but due to the high levels of200Tl and202Tl its use in humans is not possible unless enriched202Hg is used as target in the irradiation. 相似文献
944.
945.
946.
947.
聚苯胺导电复合物二次掺杂的基材效应 总被引:1,自引:0,他引:1
对十二烷基苯磺酸掺杂的聚苯胺与氯磺化聚乙烯或苯乙烯-丁二烯-苯乙烯三嵌段共聚物形成的复合物的二次掺杂进行了研究。二次掺杂的复合膜经反掺杂后的UV-Vis吸收光谱在580 ̄800nm处呈现宽的吸收,证实了二次掺杂后PAn主链的展开,同时表明PAn在CSPE中的展开较在SBS中更充分,ESR动态测试表明二次掺杂诱导主链的载流子间相互作用有2种方式;PAn/CSPE中的单极化子转变为双极化子;PAn/S 相似文献
948.
José Roberto Caetano da RochaLúcio Angnes Mauro Bertotti Koiti ArakiHenrique Eisi Toma 《Analytica chimica acta》2002,452(1):23-28
The modification of a glassy carbon surface by coating with an electrostatically assembled film of tetraruthenated cobalt porphyrin/(meso-tetra(4-sulphonatephenyl)porphyrinate zinc(II) yields an indicator electrode that allows the determination of nitrite to be performed with a limit of detection of 0.1 μM in a flow injection configuration. The dynamic range extends up to 1000 μM and the repeatability of the measurements was evaluated to be 1.5% with a throughput of 50 samples per hour. The efficiency of the bilayered film to mediate the electron transfer allows the determinations to be performed at a less positive potential (+0.75 V) with enhanced sensitivity. The coating also prevents the surface poisoning and its stability is maintained over several weeks. The same detector was used for determination of nitrate after reduction to nitrite in a reductor column containing copperised cadmium. This method was used for the determination of nitrate and nitrite in mineral water, saliva and cured meats, the results being in agreement with certified values and those obtained by using recommended procedures. 相似文献
949.
950.
Biflavonoids, widely distributed in natural plants, had strong biological activities including spasmolysis, peripheral vasodilatation, antibradykinin activity and antispasmogenic action against prostaglandin PGE1, inhibition of cyclic GMP and cyclic AMP phosphodiesterase and inhibition of hepatoma cells. Recently, some biflavonoids were demonstrated to enhance suppersion of lymphocyte proliferation, inhibition of phospholipaseCr1, anti-inflammatory activity, anti-HIV activity, anticompleme… 相似文献