全文获取类型
收费全文 | 494548篇 |
免费 | 20518篇 |
国内免费 | 10892篇 |
专业分类
化学 | 258458篇 |
晶体学 | 6026篇 |
力学 | 27274篇 |
综合类 | 545篇 |
数学 | 67716篇 |
物理学 | 165939篇 |
出版年
2022年 | 3350篇 |
2021年 | 5485篇 |
2020年 | 6565篇 |
2019年 | 6649篇 |
2018年 | 14629篇 |
2017年 | 15100篇 |
2016年 | 13649篇 |
2015年 | 8528篇 |
2014年 | 10822篇 |
2013年 | 20152篇 |
2012年 | 22434篇 |
2011年 | 32219篇 |
2010年 | 21186篇 |
2009年 | 20804篇 |
2008年 | 26750篇 |
2007年 | 29299篇 |
2006年 | 16091篇 |
2005年 | 19759篇 |
2004年 | 15089篇 |
2003年 | 13623篇 |
2002年 | 11406篇 |
2001年 | 11672篇 |
2000年 | 9310篇 |
1999年 | 7613篇 |
1998年 | 6546篇 |
1997年 | 6215篇 |
1996年 | 5897篇 |
1995年 | 5433篇 |
1994年 | 5445篇 |
1993年 | 4780篇 |
1992年 | 5444篇 |
1991年 | 5405篇 |
1990年 | 5069篇 |
1989年 | 4642篇 |
1988年 | 4623篇 |
1987年 | 4524篇 |
1986年 | 4197篇 |
1985年 | 5435篇 |
1984年 | 5618篇 |
1983年 | 4532篇 |
1982年 | 4611篇 |
1981年 | 4499篇 |
1980年 | 4404篇 |
1979年 | 4497篇 |
1978年 | 4848篇 |
1977年 | 4703篇 |
1976年 | 4737篇 |
1975年 | 4299篇 |
1974年 | 4415篇 |
1973年 | 4505篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
21.
JETP Letters - Using the spectroscopic data on the 235UF6 and 238UF6 molecules and on the lasing frequencies of CF4 and para-H2 lasers and recent results, a method has been proposed to increase the... 相似文献
22.
Knyazev Yu. V. Kazak N. V. Gavrichkov V. A. Polukeev S. I. Ovchinnikov S. G. 《JETP Letters》2022,116(8):567-573
JETP Letters - Changes in the magnetic properties of FeBO3 single crystals in the course of spin crossover occurring with increasing pressure up to 63 GPa are studied both experimentally and... 相似文献
23.
Chemistry of Heterocyclic Compounds - 2-Imino-2,5-dihydrofurans are a highly valuable class of heterocyclic compounds that show versatile biological activity and are used in diverse fields of... 相似文献
24.
Zhengcheng Wang Shangyan Zhou Wei Liao Qian Zhou Meida Chen Jin Long Prof. Qingmei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202201987
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field. 相似文献
25.
Hua Saixiang Zhu Huichao Wang Xiao Wu Mingyuan Wu Qingyun Liu Jiuyi Yang Jianjun Zhang Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,... 相似文献
26.
Siberian Mathematical Journal - Let $ \{(A_{i},B_{i})\}_{i=1}^{m} $ be a set pair system. Füredi, Gyárfás, and Király called it $ 1 $ -cross intersecting if $... 相似文献
27.
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
28.
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
29.
Wang Rong Li Xu Zhou Youshi Cao Shuxuan Xu Honghao Han Wenjuan Zhang Yuxia Liu Junhai 《Journal of Russian Laser Research》2022,43(4):476-481
Journal of Russian Laser Research - We demonstrate a passively-mode-locked Pr3+: LuLiF4 laser operated at the 604 nm orange wave-length, using monolayer graphene as a saturable absorber. The... 相似文献
30.