全文获取类型
收费全文 | 5836篇 |
免费 | 478篇 |
国内免费 | 728篇 |
专业分类
化学 | 3914篇 |
晶体学 | 69篇 |
力学 | 134篇 |
综合类 | 73篇 |
数学 | 1211篇 |
物理学 | 1641篇 |
出版年
2023年 | 37篇 |
2022年 | 60篇 |
2021年 | 81篇 |
2020年 | 100篇 |
2019年 | 114篇 |
2018年 | 112篇 |
2017年 | 139篇 |
2016年 | 159篇 |
2015年 | 110篇 |
2014年 | 176篇 |
2013年 | 334篇 |
2012年 | 274篇 |
2011年 | 282篇 |
2010年 | 211篇 |
2009年 | 300篇 |
2008年 | 314篇 |
2007年 | 337篇 |
2006年 | 277篇 |
2005年 | 269篇 |
2004年 | 227篇 |
2003年 | 218篇 |
2002年 | 172篇 |
2001年 | 166篇 |
2000年 | 142篇 |
1999年 | 141篇 |
1998年 | 120篇 |
1997年 | 112篇 |
1996年 | 112篇 |
1995年 | 103篇 |
1994年 | 94篇 |
1993年 | 52篇 |
1992年 | 79篇 |
1991年 | 62篇 |
1990年 | 53篇 |
1989年 | 49篇 |
1988年 | 38篇 |
1987年 | 33篇 |
1986年 | 33篇 |
1985年 | 22篇 |
1982年 | 47篇 |
1981年 | 160篇 |
1980年 | 171篇 |
1979年 | 149篇 |
1978年 | 189篇 |
1977年 | 150篇 |
1976年 | 170篇 |
1975年 | 26篇 |
1974年 | 42篇 |
1973年 | 109篇 |
1972年 | 63篇 |
排序方式: 共有7042条查询结果,搜索用时 46 毫秒
991.
992.
以Nd:YAG激光器的二倍频输出光为抽运光,其三倍频输出抽运的光学参量发生/放大器输出光为探测光,利用光学-光学双色双共振多光子离化光谱技术(OODR-MPI),获得了NO2分子在605—675nm探测光波长范围内的多光子离化激发谱. 通过对NO2分子离化机理的分析,确定了在此波长区间,NO2分子经1+3+1双共振多光子过程离化,离化通道为NO2(X2A1)hν
关键词:
2')" href="#">NO2
光学-光学双共振多光子离化谱
里德伯态
分子常数 相似文献
993.
994.
995.
996.
997.
Dr. Fa-Jie Chen Dr. Jianmin Gao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202201843
Cysteine bioconjugation serves as a powerful tool in biological research and has been widely used for chemical modification of proteins, constructing antibody-drug conjugates, and enabling cell imaging studies. Cysteine conjugation reactions with fast kinetics and exquisite selectivity have been under heavy pursuit as they would allow clean protein modification with just stoichiometric amounts of reagents, which minimizes side reactions, simplifies purification and broadens functional group tolerance. In this concept, we summarize the recent advances in fast cysteine bioconjugation, and discuss the mechanism and chemical principles that underlie the high efficiencies of the newly developed cysteine reactive reagents. 相似文献
998.
Mengjie Hu Haiquan Chen Mengxia Wang Gang Liu Chunhai Chen Guangtao Qian Youhai Yu 《Journal of polymer science. Part A, Polymer chemistry》2021,59(4):329-339
Polyimides (PI's) with low-dielectric constant and excellent organic solubility have broad application prospects in the electronic field. Herein, this study designed a series of novel, low dielectric, organic soluble PI films by creatively introducing fluorene and pyridine ring into diamine monomers. Because of the noncoplanar structure of fluorenyl and the polarization of pyridine ring, PI films achieved a low-dielectric constant (2.22–3.09 at 10 MHz) and excellent organic solubility. Even in some organic solvents with low-boiling points, these PI films still exhibited outstanding solubility. In addition, all the films possessed high-tensile strength (≈120 MPa) and excellent optical transparency (>70%, 450 nm). It was worth noting that the glass transition temperature of films was all above 280°C and 5% weight loss temperature (T5%) was at 486–553°C. In general, the novel high-performance low-dielectric PI films are expected to be used in the field of microelectronics. 相似文献
999.
Let x=(x',x')with x'∈Rk and x'∈R^N-k andΩbe a x'-symmetric and bounded domain in R^N(N≥2).We show that if 0≤a≤k-2,then there exists a positive constant C>0 such that for all x'-symmetric function u∈C0^∞(Ω)with∫Ω|■u(x)|^N-a|x'|^-adx≤1,the following uniform inequality holds1/∫Ω|x|^-adx∫Ωe^βa|u|N-a/N-a-1|x'|^-adx≤C,whereβa=(N-a)(2πN/2Γ(k-a/2)Γ(k/2)/Γ(k/2)r(N-a/2))1/N-a-1.Furthermore,βa can not be replaced by any greater number.As the application,we obtain some weighted Trudinger–Moser inequalities for x-symmetric function on Grushin space. 相似文献
1000.
Josué M. Silla Laize A.F. Andrade Matheus P. Freitas 《Magnetic resonance in chemistry : MRC》2019,57(7):373-379
The Perlin effect and its analog for fluorinated compounds (the fluorine Perlin-like effect) manifest on one-bond C─H (C─F for the fluorine Perlin-like effect) spin–spin coupling constants (SSCCs) in six-membered rings. These effects can be useful to probe the stereochemistry (axial or equatorial) of the C─H and C─F bonds, respectively. The origin of these effects has been debatable in the literature as being due to hyperconjugative interactions, dipolar effects, and induced current density. Accordingly, a variety of model compounds has been used to probe such effects since the cyclohexanone carbonyl group and the endocyclic heteroatom lone pairs play different roles on the above-mentioned effects. Thus, the 1JC─F SSCC in fluorinated lactams and lactones were theoretically studied to gain further insight on the nature of the fluorine Perlin-like effect. In addition, because the intramolecular α-effect has recently gained attention for its importance in the reactivity and stereoelectronic interactions in peroxide compounds, some fluorinated 1,2-dioxanes and 1,2-dithianes were studied to evaluate the role of the α-effect on the behavior of 1JC─F SSCCs. Differently from fluorinated ketones and ethers, the fluorine Perlin-like effect in the amides and esters cannot be explained by hyperconjugative or dipolar interactions alone, because the resonance in these groups affect the 1JC─F values. The O─O and S─S-containing systems exhibit a strong fluorine Perlin-like effect, but unlike the α-effect, this behavior cannot be explained neither by hyperconjugation nor by dipolar interactions alone; the spatial proximity of the C─F and O─O/S─S bonds is proposed to affect the magnitude of the 1JC─F SSCC. 相似文献