全文获取类型
收费全文 | 1156篇 |
免费 | 77篇 |
国内免费 | 3篇 |
专业分类
化学 | 1022篇 |
晶体学 | 5篇 |
力学 | 5篇 |
数学 | 89篇 |
物理学 | 115篇 |
出版年
2023年 | 22篇 |
2022年 | 12篇 |
2021年 | 27篇 |
2020年 | 44篇 |
2019年 | 34篇 |
2018年 | 29篇 |
2017年 | 23篇 |
2016年 | 35篇 |
2015年 | 50篇 |
2014年 | 49篇 |
2013年 | 66篇 |
2012年 | 96篇 |
2011年 | 106篇 |
2010年 | 52篇 |
2009年 | 40篇 |
2008年 | 85篇 |
2007年 | 82篇 |
2006年 | 91篇 |
2005年 | 69篇 |
2004年 | 60篇 |
2003年 | 53篇 |
2002年 | 29篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1236条查询结果,搜索用时 223 毫秒
1.
2.
3.
Dr. Rebecca L. Greenaway Dr. Valentina Santolini Dr. Filip T. Szczypiński Dr. Michael J. Bennison Dr. Marc A. Little Andrew Marsh Dr. Kim E. Jelfs Prof. Andrew I. Cooper 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3718-3722
Molecular dumbbells with organic cage capping units were synthesised via a multi-component imine condensation between a tri-topic amine and di- and tetra-topic aldehydes. This is an example of self-sorting, which can be rationalised by computational modelling. 相似文献
4.
Robert G. Surbella III Korey P. Carter Trevor D. Lohrey Dallas Reilly Mark Kalaj Bruce K. McNamara Jon Schwantes Rebecca J. Abergel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(61):13819-13825
A new uranyl containing metal–organic framework, RPL-1 : [(UO2)2(C28H18O8)] . H2O (RPL for Radiochemical Processing Laboratory), was prepared, structurally characterized, and the solid-state photoluminescence properties explored. Single crystal X-ray diffraction data reveals the structure of RPL - 1 consists of two crystallographically unique three dimensional, interpenetrating nets with a 4,3-connected tbo topology. Each net contains large pores with an average width of 22.8 Å and is formed from monomeric, hexagonal bipyramidal uranyl nodes that are linked via 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (TCPB) ligands. The thermal and photophysical properties of RPL-1 were investigated using thermogravimetric analysis and absorbance, fluorescence, and lifetime spectroscopies. The material displays excellent thermal stability and temperature dependent uranyl and TCPB luminescence. The framework is stable in aqueous media and due to the large void space (constituting 76 % of the unit cell by volume) can sequester organic dyes, the uptake of which induces a visible change to the color of the material. 相似文献
5.
Dr. Darren M. C. Ould Dr. Rebecca L. Melen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):9835-9845
The past 20 years has seen significant advances in main group chemistry and their use in catalysis. This Minireview showcases the recent emergence of phosphorus and arsenic containing heterocycles as catalysts. With that, we discuss how the Group 15 compounds diazaphospholenes, diazaarsolenes, and their cationic counterparts have proven to be highly effective catalysts for a wide range of reduction transformations. This Minireview highlights how the initial discovery by Gudat of the hydridic nature of the P−H bond in these systems led to these compounds being used as catalysts and discusses the wide range of examples currently present in the literature. 相似文献
6.
7.
Longbo Li Andy T. Tek Rudy J. Wojtecki Rebecca Braslau 《Journal of polymer science. Part A, Polymer chemistry》2019,57(17):1821-1835
Internal plasticization of polyvinyl chloride (PVC) using thermal azide‐alkyne Huisgen dipolar cycloaddition between azidized PVC and electron‐poor acetylenediamides incorporating a branched glutamic acid linker resulted in incorporation of four plasticizing moieties per attachment point on the polymer chain. A systematic study incorporating either alkyl or polyethylene glycol esters provided materials with varying degrees of plasticization, with depressed Tg values ranging from ?1 °C to 62 °C. Three interesting trends were observed. First, Tg values of PVC bearing various internal plasticizers were shown to decrease with increasing chain length of the plasticizing ester. Second, branched internal plasticizers bearing triethylene glycol chains had lower Tg values compared to those with similar length long‐chain alkyl groups. Finally, thermogravimetric analysis of these internally plasticized PVC samples revealed that these branched internal plasticizers bearing alkyl chains are more thermally stable than similarity branched plasticizers bearing triethylene glycol units. These internal tetra‐plasticizers were synthesized and attached to PVC‐azide in three simple synthetic steps. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1821–1835 相似文献
8.
9.
10.
A Districtwide Study of Automaticity When Included in Concept‐Based Elementary School Mathematics Instruction 下载免费PDF全文
Daniel McGee Patrick Richardson Meredith Brewer Funda Gonulates Theodore Hodgson Rebecca Weinel 《School science and mathematics》2017,117(6):259-268
While conceptual understanding of properties, operations, and the base‐ten number system is certainly associated with the ability to access math facts fluently, the role of math fact memorization to promote conceptual understanding remains contested. In order to gain insight into this question, this study looks at the results when one of three elementary schools in a school district implements mandatory automaticity drills for 10 minutes each day while the remaining two elementary schools, with the same curriculum and very similar demographics, do not. This study looks at (a) the impact that schoolwide implementation of automaticity drills has on schoolwide computational math skills as measured by the ITBS and (b) the relationship between automaticity and conceptual understanding as measured by statewide standardized testing. The results suggest that while there may be an association between automaticity and higher performance on standardized tests, caution should be taken before assuming there are benefits to promoting automaticity drills. These results are consistent with those that support a process‐driven approach to automaticity based on familiarity with properties and strategies associated with the base‐ten number system; they are not consistent with those that support an answer‐driven approach to automaticity based on memorization of answers. 相似文献