全文获取类型
收费全文 | 21828篇 |
免费 | 1521篇 |
国内免费 | 2133篇 |
专业分类
化学 | 17053篇 |
晶体学 | 280篇 |
力学 | 280篇 |
综合类 | 101篇 |
数学 | 4928篇 |
物理学 | 2840篇 |
出版年
2024年 | 20篇 |
2023年 | 222篇 |
2022年 | 306篇 |
2021年 | 394篇 |
2020年 | 515篇 |
2019年 | 950篇 |
2018年 | 607篇 |
2017年 | 857篇 |
2016年 | 647篇 |
2015年 | 763篇 |
2014年 | 899篇 |
2013年 | 1694篇 |
2012年 | 1304篇 |
2011年 | 1250篇 |
2010年 | 986篇 |
2009年 | 1261篇 |
2008年 | 1443篇 |
2007年 | 1270篇 |
2006年 | 1111篇 |
2005年 | 1026篇 |
2004年 | 1015篇 |
2003年 | 879篇 |
2002年 | 1028篇 |
2001年 | 631篇 |
2000年 | 582篇 |
1999年 | 468篇 |
1998年 | 440篇 |
1997年 | 384篇 |
1996年 | 327篇 |
1995年 | 312篇 |
1994年 | 270篇 |
1993年 | 216篇 |
1992年 | 213篇 |
1991年 | 141篇 |
1990年 | 137篇 |
1989年 | 120篇 |
1988年 | 105篇 |
1987年 | 83篇 |
1986年 | 65篇 |
1985年 | 74篇 |
1984年 | 75篇 |
1983年 | 40篇 |
1982年 | 49篇 |
1981年 | 57篇 |
1980年 | 50篇 |
1979年 | 46篇 |
1978年 | 31篇 |
1976年 | 18篇 |
1974年 | 20篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(44):13929-13934
To satisfy the rapid development of portable and wearable electronics, it is highly desired to make batteries with both high energy densities and flexibility. Although some progress has been made in recent decades, the available batteries share critical problems of poor energy storage capacity and low flexibility. Herein, we have developed a silicon–oxygen battery fiber with high energy density and ultra‐high flexibility by designing a coaxial architecture with a lithiated silicon/carbon nanotube hybrid fiber as inner anode, a polymer gel as middle electrolyte and a bare carbon nanotube sheet as outer cathode. The fiber showed a high energy density of 512 Wh kg−1 and could effectively work after bending for 20 000 cycles. These battery fibers have been further woven into flexible textiles for a large‐scale application. 相似文献
912.
Maxime Guitet Pinglu Zhang Filipa Marcelo Coralie Tugny Jesús Jimnez‐Barbero Olivier Buriez Christian Amatore Virginie Mouris‐Mansuy Jean‐Philippe Goddard Louis Fensterbank Yongmin Zhang Sylvain Roland Mickaël Mnand Matthieu Sollogoub 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(28):7354-7359
913.
914.
915.
Yong-Dong Li Hao Zhao Nan Zhang 《International Journal of Solids and Structures》2013,50(22-23):3610-3617
The purpose of the present work is to study the mixed mode fracture of a piezoelectric–piezomagnetic composite with two un-coaxial cracks parallel to the interface and each in a layer. Methods of generalized dislocation simulation, Green’s function, Cauchy singular integral equation and Lobatto–Chebyshev collocation are combined together to get the numerical results of mechanical strain energy release rate (MSERR). Three kinds of effects are revealed by parametric studies, i.e., the free-surface effect, the shielding effect and the interference effect, and they are used to interpret the characteristics of COD and MSERR curves. In addition, the effects of shear loading, magnetic loading and electric loading on MSERR are also disclosed, respectively, by varying the corresponding loading factor. 相似文献
916.
Dr. Chun-Xiao Li Qian Ning Wenxuan Zhao Hou-Ji Cao Yi-Ping Wang Prof. Dr. Hong Yan Prof. Dr. Chang-Sheng Lu Prof. Dr. Yong Liang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2699-2706
The convenient cross-coupling of sp2 or sp3 carbons with a specific boron vertex on carborane cage represents significant synthetic values and insurmountable challenges. In this work, we report an Rh-catalyzed reaction between o-carborane and N-acyl-glutarimides to construct various Bcage−C bonds. Under the optimized condition, the removable imine directing group (DG) leads to B(3)− or B(3,6)−C couplings, while the pyridyl DG leads to B(3,5)−Ar coupling. In particular, an unexpected rearrangement of amide reagent is observed in pyridyl directed B(4)−C(sp3) formation. This scalable protocol has many advantages, including easy access, the use of cheap and widely available coupling agents, no requirement of an external ligand, base or oxidant, high efficiency, and a broad substrate scope. Leveraging the RhI dimer and twisted amides, this method enables straightforward access to diversely substituted and therapeutically important carborane derivatives at boron site, and provides a highly valuable vista for carborane-based drug screening. 相似文献
917.
918.
919.
Hui Mei Wenjia Han Jianglin Hu Se Xiao Yizhu Lei Rui Zhang Wanlin Mo Guangxing Li 《应用有机金属化学》2013,27(3):177-183
This work describes a highly efficient unstrained C(sp3)―N bond activation approach for synthesis of N,N‐dimethylacetamide (DMAc) via catalytic carbonylation of trimethylamine using a PdCl2/bipy (bipy = 2,2′‐bipyridine)/Me4NI catalyst system. A low Pd catalyst dosage (1.0 mol%) is sufficient for high selectivity (98.1%) and yield (90.8%), with a turnover number (TON) of 90.0 mmol of DMAc obtained per mmol of PdCl2 employed under mild reaction conditions. The influence of reaction parameters such as catalyst precursor dosage, ligand type and promoter on activity is investigated. This work also discusses in detail the halide promoter's role in the reaction, and provides a plausible mechanism based on the intermediates methyl iodide and acetyl iodide. Analyses indicate that the carbonylation of trimethylamine may proceed through an active intermediate acetyl iodide formed by carbonylation of methyl iodide generated from the decomposition of the promoter Me4NI under reaction conditions. The formation of acetyl iodide favors the cleaving efficiency of the inert unstrained C(sp3)―N bond of trimethylamine. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
920.
Rosenani A. Haque Abbas Washeel Salman Srinivasa Budagumpi Amirul Al‐Ashraf Abdullah Zena A. Abdul Hameed Al‐Mudaris Amin M. S. Abdul Majid 《应用有机金属化学》2013,27(8):465-473
A series of Ag(I) complexes ( 6 , 7 , 8 , 9 ) derived from imidazol‐2‐ylidenes was synthesized by reacting Ag2O with an o‐, m‐, p‐xylyl or 1,3,5‐triazine‐linked imidazolium salts ( 1 , 2 , 3 , 4 ) and then characterizing these using various spectro‐analytical techniques. Additionally, triazine‐linked bis‐imidazolium salt 5 was characterized using the single‐crystal X‐ray diffraction method. Complexes 6–9 were formed from the N‐heterocyclic carbene ligand precursors 1–3 as PF6‐ salts in good yields. Conversely, salt 5 does not form Ag(I) complex even under various reaction conditions. Using ampicillin as a standard, complexes 6–9 were tested against bacteria strains Escherichia coli and Staphylococcus aureus as Gram‐negative and Gram‐positive bacteria, respectively, showing potent antimicrobial activities against the tested bacteria even at minimum inhibition concentration and bacterial concentration levels. Furthermore, the potential anticancer activities of the reported complexes were evaluated against the human colorectal cancer (HCT 116) cell lines, using 5‐fluorouracil as a standard drug. The highest anticancer activities were observed for complex 8 with an IC50 value of 3.4 μm , whereas the lowest was observed for complex 9 with an IC50 value of 18.1 μm . Copyright © 2013 John Wiley & Sons, Ltd. 相似文献