全文获取类型
收费全文 | 90562篇 |
免费 | 16358篇 |
国内免费 | 9194篇 |
专业分类
化学 | 61594篇 |
晶体学 | 916篇 |
力学 | 5748篇 |
综合类 | 512篇 |
数学 | 10088篇 |
物理学 | 37256篇 |
出版年
2024年 | 344篇 |
2023年 | 2043篇 |
2022年 | 3293篇 |
2021年 | 3559篇 |
2020年 | 3927篇 |
2019年 | 3510篇 |
2018年 | 3216篇 |
2017年 | 2866篇 |
2016年 | 4582篇 |
2015年 | 4362篇 |
2014年 | 5320篇 |
2013年 | 6765篇 |
2012年 | 8209篇 |
2011年 | 8397篇 |
2010年 | 5547篇 |
2009年 | 5379篇 |
2008年 | 5782篇 |
2007年 | 5063篇 |
2006年 | 4763篇 |
2005年 | 3818篇 |
2004年 | 2941篇 |
2003年 | 2294篇 |
2002年 | 2107篇 |
2001年 | 1817篇 |
2000年 | 1604篇 |
1999年 | 1840篇 |
1998年 | 1592篇 |
1997年 | 1577篇 |
1996年 | 1563篇 |
1995年 | 1323篇 |
1994年 | 1150篇 |
1993年 | 996篇 |
1992年 | 858篇 |
1991年 | 783篇 |
1990年 | 643篇 |
1989年 | 502篇 |
1988年 | 370篇 |
1987年 | 308篇 |
1986年 | 323篇 |
1985年 | 261篇 |
1984年 | 151篇 |
1983年 | 117篇 |
1982年 | 100篇 |
1981年 | 57篇 |
1980年 | 42篇 |
1979年 | 15篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1957年 | 31篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
991.
A palladium catalyzed cross-coupling of fluorinated benzothiadiazoles (FBTs) with allyl chlorides is reported. The significant feature of this method is synthetic simplicity, providing a straightforward access to unsymmetrical and symmetrical alkylated FBT derivatives that are of interest in organic electronic and optoelectronic materials. 相似文献
992.
Guangwen Yang Wentao Wu Zhixiang Li Naiwu Chen Jian Qin Guoping Hu Yang Zhang Jian Li Shuhui Chen 《Tetrahedron letters》2018,59(6):532-536
hNav1.7 had received great interest in the past decade owing to its attractive mechanism of actions in pain processing pathway. More recently, we developed a series of efficacious hNav1.7 inhibitors for analgesic, which were characterized with a novel aminocyclohexene as pharmacophore. Herein, we reported our synthetic efforts to construct the unique scaffold, which can be rapidly accessed from readily available 7-azanorbornenes via an unexpected catalyst-free, LiAlH4 mediated tandem double bond migration-ring opening sequence. A probable mechanism was proposed to illuminate the good regio- and stereoselectivity. 相似文献
993.
994.
Nonlinear Dynamics - In this paper, we focus on the rational solutions for a combined (3 + 1)-dimensional generalized BKP equation. By using the symbolic computation with Maple,... 相似文献
995.
Nonlinear Dynamics - This paper aims at computing M-lump solutions for the $$(3+1)$$ -dimensional nonlinear evolution equation. These solutions in all directions decline to an identical state... 相似文献
996.
An efficient and widely applicable oxidation method of tribromomethyl carbinols in the presence of pyridinium chlorochromate has been developed with excellent yields up to 96%. This method was well applied for the oxidation of a variety of aromatic, aliphatic, and heterocyclic tribromomethyl carbinols. 相似文献
997.
Zhong Lvling Li Baolin Zhang Liang Ma Xinjie Chai Shouning 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(4):785-792
Russian Journal of Physical Chemistry A - A new mesoporous carbon containing nitrogen and copper was prepared by carbonizing a polymer obtained by blending p-phenylenediamine, copper(II) sulfate,... 相似文献
998.
Kun Chen Yong Cheng Yongzhi Chang Enqin Li Qing-Long Xu Can Zhang Xiaoan Wen Hongbin Sun 《Tetrahedron》2018,74(4):483-489
N-Substituted-3(10H)-acridones have been established as visible-light organic photocatalyst. These photosensitizers are efficient for oxidative coupling reaction of N-aryl tetrahydroisoquinolines with various nucleophiles. Notably, N-methyl-3(10H)-acridone (Ia) is stable and can be effectively prepared. It is a water-soluble and atom-economic catalyst, and thus holds promise for green chemical applications. Mechanistic studies confirm a single electron transfer (SET)-induced radical process and a rate-limiting step. Analysis of the photocatalytic reactivity?structure relationship reveals that the acridones are robust and tunable photosensitizers for photoredox catalysis. 相似文献
999.
Hong-Wei Sun Long Zhang Hui-Juan Zuo Ke-Jia Zhang Chun-Guang Ma 《International Journal of Theoretical Physics》2018,57(9):2695-2708
In this paper, we present an offline arbitrated quantum blind dual-signature protocol by using four-particle entangled Greenberger-Horne-Zeilinger(GHZ) states. By using the special relationship of four-particle GHZ states, we can not only support the security of quantum signature, but also guarantee the anonymity of the message owner. In our protocol, the authority of the arbitrator has been reduced, i.e., he will not help the receiver verify the signature in the verification. Compared with the previous quantum blind signature protocols, the presented arbitrator is offline. Finally, the security analysis and discussion are proposed. 相似文献
1000.