全文获取类型
收费全文 | 8687篇 |
免费 | 1286篇 |
国内免费 | 907篇 |
专业分类
化学 | 4622篇 |
晶体学 | 72篇 |
力学 | 405篇 |
综合类 | 41篇 |
数学 | 640篇 |
物理学 | 2952篇 |
无线电 | 2148篇 |
出版年
2024年 | 19篇 |
2023年 | 209篇 |
2022年 | 188篇 |
2021年 | 239篇 |
2020年 | 309篇 |
2019年 | 263篇 |
2018年 | 231篇 |
2017年 | 232篇 |
2016年 | 346篇 |
2015年 | 362篇 |
2014年 | 420篇 |
2013年 | 576篇 |
2012年 | 637篇 |
2011年 | 684篇 |
2010年 | 487篇 |
2009年 | 517篇 |
2008年 | 522篇 |
2007年 | 470篇 |
2006年 | 455篇 |
2005年 | 443篇 |
2004年 | 341篇 |
2003年 | 271篇 |
2002年 | 282篇 |
2001年 | 207篇 |
2000年 | 233篇 |
1999年 | 229篇 |
1998年 | 193篇 |
1997年 | 165篇 |
1996年 | 200篇 |
1995年 | 159篇 |
1994年 | 154篇 |
1993年 | 138篇 |
1992年 | 136篇 |
1991年 | 106篇 |
1990年 | 71篇 |
1989年 | 82篇 |
1988年 | 57篇 |
1987年 | 48篇 |
1986年 | 42篇 |
1985年 | 39篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1970年 | 6篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 492 毫秒
971.
972.
Minghao LiYanlong Gu 《Tetrahedron》2011,67(43):8314-8320
An electrophilic ring-opening reaction of 2-aryl-3,4-dihydropyran with many nucleophiles, such as thiophenols, thiols, benzenesulfinic acid, resorcin, 2-methylfuran, benzamide and allyltrimethylsilane, was developed. In the presence of an appropriate catalyst, a product that contains not only a moiety of the nucleophile but also a fragment of 1,3-dicarbonyl compound was obtained. 相似文献
973.
In this paper, we investigate the well-posedness of the real fractional Ginzburg–Landau equation in several different function spaces, which have been used to deal with the Burgers’ equation, the semilinear heat equation, the Navier–Stokes equations, etc. The long time asymptotic behavior of the nonnegative global solutions is also studied in details. 相似文献
974.
975.
Haixin Cui Jianfang Jiang Wei Gu Changjiao Sun Donglai Wu Tao Yang Guochen Yang 《Photochemistry and photobiology》2010,86(5):1135-1139
This study was conducted to investigate efficiency of TiO2nanomaterial as a novel environment-friendly disinfectant to control avian influenza (AI) by its photochemical sterilization ability. Anatase nano-TiO2sol, a neutral, viscous aqueous colloid of 1.6% TiO2, was synthesized from peroxotitanic acid solution according to the Ichinose method. Transmission electron microscope images showed that the TiO2particles were spindle-shaped with an average size of 50 nm. X-ray diffraction patterns revealed that the crystal phase of TiO2particles was anatase type with photocatalytic effect. A photocatalytic film of nano-TiO2sol was tested as a means of inactivating H9N2avian influenza virus (AIV). Inactivation capabilities were examined with 365 nm ultraviolet (UV) radiation under black light by adjusting the UV intensity, the UV irradiation time and the quantity of AIV. The titer change of AIV was determined by hemagglutination tests. Cytopathic effect of Madin Darby canine kidney (MDCK) cells was monitored by inverted fluorescence microscope. The results showed that anatase nano-TiO2sol significantly inactivated AIV under UV irradiation of 365 nm. The inactivation of AIV viruses reached up to 100%. Therefore, anatase nano-TiO2sol is a potentially environment-friendly antivirus agent to prevent AI. 相似文献
976.
Since Multivatriate Quadratic (MQ)-based Public Key Cryptosystem (MPKC) has been one of the hot research fields of post-quantum cryptography, it becomes important to analyze the security of new MPKC schemes. Wang et al. proposed a novel multivariate signature scheme with Hash-based Tame Transformation and Minus (HTTM) in 2011. For this extended MQ-based signature, we can transform it into an SFLASH variant by splitting and merging HT transformation, and solve an equivalent private key corresponding to the public key of HTTM. Thus, the adversary can forge legitimate signature for any message by using this equivalent private key. 相似文献
977.
Selective lipase-catalyzed acylation of 41-desmethoxyrapamycin has been achieved with a quaternary carboxylic acid avoiding the use of vinyl ester activation. Among the acyl donors investigated, the novel butanedione-monooxime and the N-acetylhydroxamate ester proved to be the most efficient donors, comparable in reactivity to the undesired vinyl ester and allowing selective, preparative acylation on gram scale in excellent yields. These new donors are proposed as sustainable and process-friendly alternatives to the widely used vinyl ester substrate activation in lipase-catalyzed acylations of secondary alcohols. 相似文献
978.
Fazuo Wang Tianjiao Zhu Min Zhang Aiqun Lin Weiming Zhu Qianqun Gu 《Magnetic resonance in chemistry : MRC》2010,48(2):155-158
Three new furan and pyran derivatives named aspericins A? C (1–3), as well as a known asperic acid (4), have been isolated from the marine‐derived fungus Rhizopus sp. 2‐PDA‐61. The complete 1H and 13C NMR assignments for the new compounds were carried out using 1H, 13C, DEPT, COSY, HMQC, HMBC, and NOESY NMR experiments. Compounds 1–3 were evaluated for their cytotoxic activities on P388, A549, HL‐60, and BEL‐7420 cell lines by the MTT and SRB methods. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
979.
980.