全文获取类型
收费全文 | 2553篇 |
免费 | 112篇 |
国内免费 | 14篇 |
专业分类
化学 | 2109篇 |
晶体学 | 17篇 |
力学 | 39篇 |
数学 | 186篇 |
物理学 | 328篇 |
出版年
2023年 | 13篇 |
2021年 | 21篇 |
2020年 | 32篇 |
2019年 | 56篇 |
2018年 | 21篇 |
2017年 | 28篇 |
2016年 | 64篇 |
2015年 | 48篇 |
2014年 | 55篇 |
2013年 | 105篇 |
2012年 | 178篇 |
2011年 | 214篇 |
2010年 | 78篇 |
2009年 | 87篇 |
2008年 | 154篇 |
2007年 | 194篇 |
2006年 | 171篇 |
2005年 | 177篇 |
2004年 | 155篇 |
2003年 | 128篇 |
2002年 | 109篇 |
2001年 | 41篇 |
2000年 | 27篇 |
1999年 | 13篇 |
1998年 | 22篇 |
1997年 | 17篇 |
1996年 | 24篇 |
1995年 | 16篇 |
1994年 | 33篇 |
1993年 | 29篇 |
1992年 | 21篇 |
1991年 | 23篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 21篇 |
1984年 | 22篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 7篇 |
1974年 | 12篇 |
1973年 | 11篇 |
1971年 | 7篇 |
排序方式: 共有2679条查询结果,搜索用时 109 毫秒
1.
2.
Chuanli Wu Xiaohang Qiao Dr. Craig M. Robertson Prof. Simon J. Higgins Prof. Chenxin Cai Prof. Richard J. Nichols Dr. Andrea Vezzoli 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12127-12132
Polyoxometalates have been proposed in the literature as nanoelectronic components, where they could offer key advantages with their structural versatility and rich electrochemistry. Apart from a few studies on their ensemble behaviour (as monolayers or thin films), this potential remains largely unexplored. We synthesised a pyridyl-capped Anderson–Evans polyoxometalate and used it to fabricate single-molecule junctions, using the organic termini to chemically “solder” a single cluster to two nanoelectrodes. Operating the device in an electrochemical environment allowed us to probe charge transport through different oxidation states of the polyoxometalate, and we report here an efficient three-state transistor behaviour. Conductance data fits a quantum tunnelling mechanism with different charge-transport probabilities through different charge states. Our results show the promise of polyoxometalates in nanoelectronics and give an insight on their single-entity electrochemical behaviour. 相似文献
3.
The mechanical strength of individual polymer chains is believed to underlie a number of performance metrics in bulk materials, including adhesion and fracture toughness. Methods by which the intrinsic molecular strength of the constituents of a given polymeric material might be switched are therefore potentially useful both for applications in which triggered property changes are desirable, and as tests of molecular theories for bulk behaviors. Here we report that the sequential oxidation of sulfide containing polyesters (PE-S) to the corresponding sulfoxide (PE-SO) and then sulfone (PE-SO2) first weakens (sulfoxide), and then enhances (sulfone), the effective mechanical integrity of the polymer backbone; PE-S ∼ PE-SO2 > PE-SO. The relative mechanical strength as a function of oxidation state is revealed through the use of gem-dichlorocyclopropane nonscissile mechanophores as an internal standard, and the observed order agrees well with the reported bond dissociation energies of C–S bonds in each species and with the results of CoGEF modeling.The mechanical strength of individual polymer chains is believed to underlie a number of performance metrics in bulk materials, including adhesion and fracture toughness. 相似文献
4.
5.
Bas van Genabeek Brigitte A. G. Lamers Craig J. Hawker E. W. Meijer Will R. Gutekunst Bernhard V. K. J. Schmidt 《Journal of polymer science. Part A, Polymer chemistry》2021,59(5):373-403
Precise oligomeric materials constitute a growing area of research with implications for various applications as well as fundamental studies. Notably, this field of science which can be termed macro-organic chemistry, draws inspiration from both traditional polymer chemistry and organic synthesis, combining the molecular precision of organic chemistry with the materials properties of macromolecules. Discrete oligomers enable access to unprecedented materials properties, for example, in self-assembled structures, crystallization, or optical properties. The degree of control over oligomer structures resembles many biological systems and enables the design of materials with tailored properties and the development of fundamental structure–property relationships. This Review highlights recent developments in macro-organic chemistry from synthetic concepts to materials properties, with a focus on self-assembly and molecular recognition. Finally, an outlook for future research directions is provided. 相似文献
6.
Varsha J. Thombare Craig A. Hutton 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):5052-5056
Peptide macrocyclization is often a slow process, plagued by epimerization and cyclodimerization. Herein, we describe a new method for peptide macrocyclization employing the AgI‐promoted transformation of peptide thioamides. The AgI has a dual function: chemoselectively activating the thioamide and tethering the N‐terminal thioamide to the C‐terminal carboxylate. Extrusion of Ag2S generates an isoimide intermediate, which undergoes acyl transfer to generate the native cyclic peptide, resulting in a rapid, traceless macrocylization process. Cyclic peptides are furnished in high yields within 1 hour, free of epimerization and cyclodimerization. 相似文献
7.
Dr. Sevan D. Houston Dr. Hui Xing Prof. Paul V. Bernhardt Timothy J. Vanden Berg Dr. John Tsanaktsidis Dr. G. Paul Savage Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(11):2735-2739
The scope and limitations of Eaton's rhodium(I)-catalyzed valence isomerization of cubane to cyclooctatetraene (COT) were investigated in the context of functional group tolerability, multiple substitution modes and the ability of cubane-alcohols to undergo one-pot tandem Ley–Griffith Wittig reactions in the absence of a transition metal catalyst. 相似文献
8.
9.
Raghida Bou Zerdan Zhishuai Geng Benjaporn Narupai Yvonne J. Diaz Morgan W. Bates David S. Laitar Biswas Souvagya Antony K. Van Dyk Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2020,58(14):1989-1997
The utility of pentafluorophenyl esters for the selective introduction of functional units and branch points in well-defined poly(acrylic acid) (PAA) derivatives is demonstrated using a combination of controlled radical polymerization and postpolymerization modification. Reversible addition-fragmentation chain transfer enables the synthesis of well-defined copolymers—poly(pentafluorophenyl acrylate-co-tert-butyl acrylate)—with the active ester repeat units serving as attachment points for reaction with primary amines, specifically tris(2-(t-butoxycarbonyl)ethyl)methyl amine (Behera's amine). Deprotection using trifluoroacetic acid removes both the backbone and side chain t-butyl esters to give a series of branched PAA derivatives containing novel tricarboxylic acid side chains that are well suited to complexation and multidentate interactions. Surprisingly, the active ester homopolymer is shown to have the highest reactivity with Behera's amine when compared to copolymers with lower incorporation of pentafluorophenyl esters, suggesting an intriguing interplay of neighboring group effects and steric interactions. The ability to tune the efficiency of postpolymerization modification gives a library of PAA derivatives. 相似文献
10.
Madeleine A. Dallaston Dr. Sevan D. Houston Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(52):11966-11970
With the burgeoning interest in cage motifs for bioactive molecule discovery, and the recent disclosure of 1,4-cubane-dicarboxylic acid impact sensitivity, more research into the safety profiles of cage scaffolds is required. Therefore, the impact sensitivity and thermal decomposition behavior of judiciously selected starting materials and synthetic intermediates of cubane, bicyclo[1.1.1]pentane (BCP), and bicyclo[2.2.2]octane (BCO) were evaluated via hammer test and sealed cell differential scanning calorimetry, respectively. Iodo-substituted systems were found to be more impact sensitive, whereas hydroxymethyl substitution led to more rapid thermodecomposition. Cubane was more likely to be impact sensitive with these substituents, followed by BCP, whereas all BCOs were unresponsive. The majority of derivatives were placed substantially above Yoshida thresholds—a computational indicator of sensitivity. 相似文献