全文获取类型
收费全文 | 2938篇 |
免费 | 98篇 |
国内免费 | 14篇 |
专业分类
化学 | 2244篇 |
晶体学 | 20篇 |
力学 | 34篇 |
数学 | 334篇 |
物理学 | 418篇 |
出版年
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 47篇 |
2020年 | 46篇 |
2019年 | 47篇 |
2018年 | 38篇 |
2017年 | 31篇 |
2016年 | 75篇 |
2015年 | 70篇 |
2014年 | 74篇 |
2013年 | 180篇 |
2012年 | 189篇 |
2011年 | 222篇 |
2010年 | 152篇 |
2009年 | 143篇 |
2008年 | 222篇 |
2007年 | 234篇 |
2006年 | 175篇 |
2005年 | 197篇 |
2004年 | 137篇 |
2003年 | 104篇 |
2002年 | 95篇 |
2001年 | 64篇 |
2000年 | 49篇 |
1999年 | 37篇 |
1998年 | 28篇 |
1997年 | 27篇 |
1996年 | 42篇 |
1995年 | 15篇 |
1994年 | 20篇 |
1993年 | 24篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 22篇 |
1989年 | 12篇 |
1988年 | 20篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 18篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1966年 | 3篇 |
排序方式: 共有3050条查询结果,搜索用时 15 毫秒
1.
Dr. Yolimar Gil Dr. Alejandro Castro-Alvarez Dr. Pablo Fuentealba Prof. Evgenia Spodine Dr. Daniel Aravena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202200336
Enhancement of axial magnetic anisotropy is the central objective to push forward the performance of Single-Molecule Magnet (SMM) complexes. In the case of mononuclear lanthanide complexes, the chemical environment around the paramagnetic ion must be tuned to place strongly interacting ligands along either the axial positions or the equatorial plane, depending on the oblate or prolate preference of the selected lanthanide. One classical strategy to achieve a precise chemical environment for a metal centre is using highly structured, chelating ligands. A natural approach for axial-equatorial control is the employment of macrocycles acting in a belt conformation, providing the equatorial coordination environment, and leaving room for axial ligands. In this review, we present a survey of SMMs based on the macrocycle belt motif. Literature systems are divided in three families (crown ether, Schiff-base and metallacrown) and their general properties in terms of structural stability and SMM performance are briefly discussed. 相似文献
2.
Peralta Cecilia Mariana Acosta Gimena Henestrosa Cecilia Gil Raúl Andrés Fernández Liliana Patricia 《Journal of Analytical Chemistry》2022,77(3):308-317
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,... 相似文献
3.
Dr. Antonio M. Rodríguez Dr. Pilar Prieto Prof. Antonio de la Hoz Prof. Ángel Díaz-Ortiz D. Raúl Martín Prof. José I. García 《ChemistryOpen》2015,4(3):308-317
The aim of this work was to determine the parameters that have decisive roles in microwave-assisted reactions and to develop a model, using computational chemistry, to predict a priori the type of reactions that can be improved under microwaves. For this purpose, a computational study was carried out on a variety of reactions, which have been reported to be improved under microwave irradiation. This comprises six types of reactions. The outcomes obtained in this study indicate that the most influential parameters are activation energy, enthalpy, and the polarity of all the species that participate. In addition to this, in most cases, slower reacting systems observe a much greater improvement under microwave irradiation. Furthermore, for these reactions, the presence of a polar component in the reaction (solvent, reagent, susceptor, etc.) is necessary for strong coupling with the electromagnetic radiation. We also quantified that an activation energy of 20–30 kcal mol−1 and a polarity (μ) between 7–20 D of the species involved in the process is required to obtain significant improvements under microwave irradiation. 相似文献
4.
5.
6.
7.
Sung Hwan Koo Dong Jun Li Taeyeong Yun Dong Sung Choi Kyung Eun Lee Gil Yong Lee Youngtak Oh Joonwon Lim Suchithra Padmajan Sasikala Ho Jin Lee In Ho Kim Hong Ju Jung Rishabh Jain Sang Ouk Kim 《Particle & Particle Systems Characterization》2019,36(7)
Efficient water electrolysis catalyst is highly demanded for the production of hydrogen as a sustainable energy fuel. It is reported that cobalt derived nanoparticle (CoS2, CoP, CoS|P) decorated reduced graphene oxide (rGO) composite aerogel catalysts for highly active and reliable hydrogen evolution reaction electrocatalysts. 7 nm level cobalt derived nanoparticles are synthesized over graphene aerogel surfaces with excellent surface coverage and maximal expose of active sites. CoS|P/rGO hybrid aerogel composites show an excellent catalytic activity with overpotential of ≈169 mV at a current density of ≈10 mA cm?2. Accordingly, efficient charge transfer is attained with Tafel slope of ≈52 mV dec?1 and a charge transfer resistance (Rct) of ≈12 Ω. This work suggests a viable route toward ultrasmall, uniform nanoparticles decorated graphene surfaces with well‐controlled chemical compositions, which can be generally useful for various applications commonly requiring large exposure of active surface area as well as robust interparticle charger transfer. 相似文献
8.
Dr. Felipe L. Coelho Eduarda S. Gil Dr. Paulo F. B. Gonçalves Dr. Leandra F. Campo Dr. Paulo H. Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8157-8162
In this work, a series of 2-chalcogenylindoles was synthesized by an efficient methodology, starting from chalcogenoalkynes, including a previously unreported tellurium indole derivative. For the first time, these 2-substituted chalcogenylindoles were obtained in the absence of metal catalyst or base, under thermal conditions only. In addition, the results described herein represent a methodology with inverse regioselectivity for the chalcogen functionalization of indoles. 相似文献
9.
Gil Tae Hwang 《Tetrahedron letters》2004,45(18):3543-3546
We describe the design and properties of a pyrene-labeled deoxyuridine that can be inserted efficiently into oligodeoxynucleotides using phosphoramidite chemistry. An oligonucleotide incorporating the pyrene-labeled deoxyuridine is a sensitive fluorescence probe that can discriminate between perfect and single-base-mismatched pairing by changes in its fluorescence intensity. 相似文献
10.
Inequalities satisfied by the zeros of the solutions of second-order hypergeometric equations are derived through a systematic use of Liouville transformations together with the application of classical Sturm theorems. This systematic study allows us to improve previously known inequalities and to extend their range of validity as well as to discover inequalities which appear to be new. Among other properties obtained, Szegő's bounds on the zeros of Jacobi polynomials for , are completed with results for the rest of parameter values, Grosjean's inequality (J. Approx. Theory 50 (1987) 84) on the zeros of Legendre polynomials is shown to be valid for Jacobi polynomials with |β|1, bounds on ratios of consecutive zeros of Gauss and confluent hypergeometric functions are derived as well as an inequality involving the geometric mean of zeros of Bessel functions. 相似文献