全文获取类型
收费全文 | 35743篇 |
免费 | 5347篇 |
国内免费 | 3812篇 |
专业分类
化学 | 18595篇 |
晶体学 | 272篇 |
力学 | 1938篇 |
综合类 | 227篇 |
数学 | 3537篇 |
物理学 | 10601篇 |
无线电 | 9732篇 |
出版年
2024年 | 104篇 |
2023年 | 912篇 |
2022年 | 1008篇 |
2021年 | 1345篇 |
2020年 | 1420篇 |
2019年 | 1273篇 |
2018年 | 1134篇 |
2017年 | 1130篇 |
2016年 | 1550篇 |
2015年 | 1556篇 |
2014年 | 1892篇 |
2013年 | 2510篇 |
2012年 | 2954篇 |
2011年 | 3002篇 |
2010年 | 2161篇 |
2009年 | 2171篇 |
2008年 | 2312篇 |
2007年 | 1980篇 |
2006年 | 1894篇 |
2005年 | 1627篇 |
2004年 | 1113篇 |
2003年 | 961篇 |
2002年 | 849篇 |
2001年 | 730篇 |
2000年 | 759篇 |
1999年 | 897篇 |
1998年 | 753篇 |
1997年 | 720篇 |
1996年 | 657篇 |
1995年 | 608篇 |
1994年 | 531篇 |
1993年 | 440篇 |
1992年 | 380篇 |
1991年 | 316篇 |
1990年 | 276篇 |
1989年 | 220篇 |
1988年 | 160篇 |
1987年 | 145篇 |
1986年 | 101篇 |
1985年 | 110篇 |
1984年 | 71篇 |
1983年 | 55篇 |
1982年 | 59篇 |
1981年 | 26篇 |
1980年 | 16篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1957年 | 7篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
931.
932.
A type of high visible-light active titanium oxinitride(TiO2-xNx) powder was prepared by a simple proc-ess:the calcination of the hydrated titanium dioxide at the atmosphere of ammonia-argon using a tu-bular electric furnace at high temperatures. The hydrated titanium dioxide was synthesized as the precursor of TiO2-xNx using titanic acid as raw material,which came from sulfate technique of produc-ing titanium white. The effects of temperature and reaction time on the nitrogen content,grain size and crystal structure were studied. The visible-light activity and photocatalysis capability of the powder were also investigated. 相似文献
933.
The electrochemical behavior and the interaction of alizarin red S (ARS) with calf thymus DNA was investigated on a bare glassy carbon electrode (GCE) and DNA modified GCE (DNA/GCE), respectively. ARS showed a pair of redox peaks at ?0.445 V and ?0.414 V on a bare GCE. On addition of DNA into the ARS solution, the peak current of ARS decreased and the peak potential positively shifted, but without new redox peaks appeared. The ARS reduction peak current increased with immersion time on a DNA/GCE. The results showed that ARS could interact with DNA molecules by intercalative binding mode. The equilibrium constant, binding number and the ratio of binding constant for oxidized and reduced ARS forms were obtained. The DNA damage was directly detected by appearance of guanosine and adenosine bases oxidation signal. The influence of experimental conditions on DNA damage extent was discussed in detail. 相似文献
934.
表面电沉积Ni—La2O3复合镀层的Fe26Cr1Mo不锈钢的氧化行为研究 总被引:3,自引:0,他引:3
Fe26Cr1Mo不锈钢在900℃氧化时,生成的氧化层在冷却过程中大量剥落,经表面共电沉积NiLa2O3复合镀层后,抗热循环能力明显提高。 相似文献
935.
双亲嵌段聚合物的合成与应用 总被引:8,自引:0,他引:8
本文介绍了双亲嵌段聚合物的合成方法,包括共溶剂法、聚合后功能化法、胶束聚合法、自由基界面聚合法等,以及双亲嵌段聚合物在乳液聚合、三次采油、医用高分子材料等方面的应用。 相似文献
936.
Lin Guo-qiang Xu Hai-jian Wu Bi-chi Guo Guong-zhong Zhou Wei-shan 《Tetrahedron letters》1985,26(9):1233-1236
All the four optical isomers of the oviposition attractant pheromone of the mosquito were synthesized via Sharpless asymmetric epoxidation. 相似文献
937.
938.
939.
混合三烃基锡衍生物的研究:X.甲基二环己基锡二硫代磷酸酯的合成及生… 总被引:4,自引:2,他引:4
合成了10种甲基二环己基锡-O,O-二烃基二硫代磷酸酯,利用IR,NMR,MS及元素分析确证了化合物的结构,生物活性测试结果表明,这类化合物具有较高的杀螨和除草活性。 相似文献
940.
A new separation matrix, consisting of polymer poly(N-isopropylacrylamide) (PNIPAM) and small molecule additive mannitol, was used for double-stranded (ds) DNA and plasmid DNA separation by capillary electrophoresis. The matrix had a low viscosity, which made it very easy to handle. The additive mannitol dramatically enhanced the sieving performance of PNIPAM in TBE buffer. The optimal mannitol concentration 6% in polymer solution, was determined with the consideration of both speed and resolution. A resolution of 0.95 was achieved on the separation of 271/281 bp in the phiX174/HaeIII digest by using 1.5% PNIPAM + 6% mannitol, while the supercoiled, linear and nicked conformers of lambda plasmid were separated in 1% PNIPAM + 6% mannitol, demonstrating the potential use of this new matrix for effective DNA separations. The dramatic impact of mannitol on sieving performance of PNIPAM solution was investigated. pH dependent self-coating ability of PNIPAM was revealed. The presence of mannitol in TBE buffer decreased the pH of the buffer, which led to more efficient self-coating ability of PNIPAM probable due to the formation of hydrogen bonds between PNIPAM molecules and silanol groups at the silica wall. 相似文献