全文获取类型
收费全文 | 1707篇 |
免费 | 37篇 |
国内免费 | 7篇 |
专业分类
化学 | 1373篇 |
晶体学 | 13篇 |
力学 | 25篇 |
数学 | 210篇 |
物理学 | 130篇 |
出版年
2023年 | 15篇 |
2022年 | 36篇 |
2021年 | 41篇 |
2020年 | 44篇 |
2019年 | 33篇 |
2018年 | 28篇 |
2017年 | 19篇 |
2016年 | 58篇 |
2015年 | 44篇 |
2014年 | 48篇 |
2013年 | 92篇 |
2012年 | 135篇 |
2011年 | 111篇 |
2010年 | 64篇 |
2009年 | 44篇 |
2008年 | 122篇 |
2007年 | 137篇 |
2006年 | 106篇 |
2005年 | 107篇 |
2004年 | 84篇 |
2003年 | 75篇 |
2002年 | 70篇 |
2001年 | 20篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 22篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有1751条查询结果,搜索用时 0 毫秒
991.
We etablish a necessary and sufficient condition under which there exists a tangential and well graded star product, differential or not, on the dual
of a nilpotent Lie algebra
. We also give enlightening examples with explicit computations. 相似文献
992.
Within the field of single-entity electrochemistry through so-called impact experiments, the use of soft interfaces can be a valuable and advantageous complement to conventional solid microelectrodes, as recently demonstrated for both hard and soft micro- and nanoparticles. Additionally, this approach can offer a new platform for fundamental studies of key aspects of electronic and ionic transfers across liquid–liquid interfaces, with applications in relevant biological, technological and industrial systems. Experimental results with Interfaces between Two Immiscible Electrolyte Solutions (ITIES) are reviewed and discussed under the light of theoretical treatments are here revisited or developed. 相似文献
993.
Konstantina Vougogiannopoulou Angela Corona Enzo Tramontano Michael N. Alexis Alexios-Leandros Skaltsounis 《Molecules (Basel, Switzerland)》2021,26(2)
The ongoing pandemic of severe acute respiratory syndrome (SARS), caused by the SARS-CoV-2 human coronavirus (HCoV), has brought the international scientific community before a state of emergency that needs to be addressed with intensive research for the discovery of pharmacological agents with antiviral activity. Potential antiviral natural products (NPs) have been discovered from plants of the global biodiversity, including extracts, compounds and categories of compounds with activity against several viruses of the respiratory tract such as HCoVs. However, the scarcity of natural products (NPs) and small-molecules (SMs) used as antiviral agents, especially for HCoVs, is notable. This is a review of 203 publications, which were selected using PubMed/MEDLINE, Web of Science, Scopus, and Google Scholar, evaluates the available literature since the discovery of the first human coronavirus in the 1960s; it summarizes important aspects of structure, function, and therapeutic targeting of HCoVs as well as NPs (19 total plant extracts and 204 isolated or semi-synthesized pure compounds) with anti-HCoV activity targeting viral and non-viral proteins, while focusing on the advances on the discovery of NPs with anti-SARS-CoV-2 activity, and providing a critical perspective. 相似文献
994.
Dinesh Talwar Angela Gonzalez‐de‐Castro Ho Yin Li Jianliang Xiao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(17):5312-5316
A new strategy has been developed for the oxidant‐ and base‐free dehydrogenative coupling of N‐heterocycles at mild conditions. Under the action of an iridium catalyst, N‐heterocycles undergo multiple sp3 C H activation steps, generating a nucleophilic enamine that reacts in situ with various electrophiles to give highly functionalized products. The dehydrogenative coupling can be cascaded with Friedel–Crafts addition, resulting in a double functionalization of the N‐heterocycles. 相似文献
995.
Angela N. H. Creager 《Ambix》2017,64(4):343-359
This article examines the often-overlooked role of chemical ideas and practices in the history of modern biology. The first section analyses how the conventional histories of the life sciences have, through the twentieth century, come to focus nearly exclusively on evolutionary theory and genetics, and why this storyline is inadequate. The second section elaborates on what the restricted neo-Darwinian history of biology misses, noting a variety of episodes in the history of biology that relied on developments in – or tools from – chemistry, including an example from the author’s own work. The diverse ways in which biologists have used chemical approaches often relate to the concrete, infrastructural side of research; a more inclusive history thus also connects to a historiography of materials and objects in science. 相似文献
996.
We study the Dirichlet problem for the Hénon equation
where Ω is the unit ball in , with N ≥ 3, the power α is positive and is a small positive parameter. We prove that for every integer k ≥ 1 the above problem has a solution which blows up at k different points of ∂Ω as goes to zero. We also show that the ground state solution (which blows up at one point) is unique.
The first author is supported by the M.I.U.R. National Project “Metodi variazionali e topologici nello studio di fenomeni
non lineari” . The second author is supported by the M.I.U.R. National Project “Metodi variazionali ed equazioni differenziali
nonlineari”. 相似文献
997.
998.
Zhou Z Kümmerle R Qiu X Redwine D Cong R Taha A Baugh D Winniford B 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,187(2):225-233
(13)C NMR is a powerful analytical tool for characterizing polyethylene copolymer composition and sequence distribution. Accurate characterization of the composition and sequence distribution is critical for researchers in industry and academia. Some common composite pulse decoupling (CPD) sequences used in polyethylene copolymer (13)C NMR can lead to artifacts such as modulations of the decoupled (13)C NMR signals (decoupling sidebands) resulting in systematic errors in quantitative analysis. A new CPD method was developed, which suppresses decoupling sidebands below the limit of detection (less than 1:40,000 compared to the intensity of the decoupled signal). This new CPD sequence consists of an improved Waltz-16 CPD, implemented as a bilevel method. Compared with other conventional CPD programs this new decoupling method produced the cleanest (13)C NMR spectra for polyethylene copolymer composition and triad sequence distribution analyses. 相似文献
999.
Font-Sanchis E Céspedes-Guirao FJ Sastre-Santos A Fernandez-Lazaro F 《The Journal of organic chemistry》2007,72(9):3589-3591
The palladium-mediated coupling reaction between triorganoindium reagents and organic electrophiles is extended to the synthesis of heteroaromatic compounds. Both electron-rich and electron-poor heterocycles can act as the organic electrophile or as the organoindium derivative. 相似文献
1000.