全文获取类型
收费全文 | 108705篇 |
免费 | 26777篇 |
国内免费 | 6686篇 |
专业分类
化学 | 97481篇 |
晶体学 | 702篇 |
力学 | 6600篇 |
综合类 | 519篇 |
数学 | 11096篇 |
物理学 | 25770篇 |
出版年
2023年 | 4865篇 |
2022年 | 2888篇 |
2021年 | 4503篇 |
2020年 | 6692篇 |
2019年 | 4575篇 |
2018年 | 4161篇 |
2017年 | 2425篇 |
2016年 | 8062篇 |
2015年 | 8087篇 |
2014年 | 8127篇 |
2013年 | 9513篇 |
2012年 | 8786篇 |
2011年 | 6987篇 |
2010年 | 7321篇 |
2009年 | 7235篇 |
2008年 | 5180篇 |
2007年 | 4510篇 |
2006年 | 3668篇 |
2005年 | 3161篇 |
2004年 | 2535篇 |
2003年 | 1939篇 |
2002年 | 1716篇 |
2001年 | 1558篇 |
2000年 | 1434篇 |
1999年 | 1595篇 |
1998年 | 1355篇 |
1997年 | 1250篇 |
1996年 | 1302篇 |
1995年 | 1211篇 |
1994年 | 1088篇 |
1993年 | 1074篇 |
1992年 | 865篇 |
1991年 | 731篇 |
1990年 | 611篇 |
1989年 | 557篇 |
1988年 | 481篇 |
1987年 | 447篇 |
1986年 | 376篇 |
1985年 | 398篇 |
1984年 | 308篇 |
1977年 | 361篇 |
1976年 | 411篇 |
1975年 | 513篇 |
1974年 | 520篇 |
1973年 | 341篇 |
1972年 | 396篇 |
1971年 | 375篇 |
1970年 | 567篇 |
1969年 | 431篇 |
1968年 | 453篇 |
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
21.
Hao Lu Xiaodong Wang Hang Wang Andong Zhang Xinming Zheng Na Yu Zheng Tang Xinjun Xu Yahui Liu Ya-Nan Chen Zhishan Bo 《中国科学:化学(英文版)》2022,65(3):594-601
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs. 相似文献
22.
Prof. Dr. Peter Hess 《Chemphyschem》2022,23(6):e202100880
In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials. 相似文献
23.
Edward G. Sheetz Zhao Zhang Alyssa Marogil Minwei Che Dr. Maren Pink Dr. Veronica Carta Prof. Dr. Krishnan Raghavachari Prof. Dr. Amar H. Flood 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201584
The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3−). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3−, by cyanostar macrocycles that are size-complementary to the inorganic BF4− progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R−BF3− anions. 相似文献
24.
25.
根据教育部颁布的《普通高中物理课程标准(2017年版)》,在上海市物理教育教学基地(上海高校“立德树人”人文社会科学重点研究基地)的大力支持下,由上海市教育委员会组织编写的上海高中物理非统编教材进行了正式使用前的试教试用活动,此教材是在上海高中物理“二期课改”教材的基础上全面改写而成的.单元教学设计已成为当前教学设计的焦点问题,以《物理·必修》(第三册)静电场单元为例,详细阐述了“教学问题链”的设计理念,希望与广大一线教师交流试教试用的心得与反思,推动新课改课堂转型. 相似文献
26.
Zhang Ya-Li Han Rong-Sheng Chen Liang 《International Journal of Theoretical Physics》2021,60(4):1384-1398
International Journal of Theoretical Physics - In this work, we give an analytical derivation of the reduced density matrix between two qubits in a cavity field, which is described by the quantum... 相似文献
27.
Geometriae Dedicata - We show that an n-dimensional surface whose entropy is close to that of an n-dimensional plane is close in Hausdorff distance to some n-dimensional plane at every scale.... 相似文献
28.
Journal of Visualization - Forecast calibration methods based on historical similar atmospheric state are effective means weather forecast accuracy. Conventional approaches search similar forecasts... 相似文献
29.
30.
Reza Kordnezhadian Bing-Yu Li Armir Zogu Dr. Joachim Demaerel Prof. Dr. Wim M. De Borggraeve Dr. Ermal Ismalaj 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201491
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015. 相似文献