全文获取类型
收费全文 | 229088篇 |
免费 | 31691篇 |
国内免费 | 25064篇 |
专业分类
化学 | 118034篇 |
晶体学 | 1889篇 |
力学 | 10976篇 |
综合类 | 1352篇 |
数学 | 22543篇 |
物理学 | 63165篇 |
无线电 | 67884篇 |
出版年
2024年 | 509篇 |
2023年 | 4601篇 |
2022年 | 5550篇 |
2021年 | 7719篇 |
2020年 | 7909篇 |
2019年 | 7269篇 |
2018年 | 6691篇 |
2017年 | 6456篇 |
2016年 | 9100篇 |
2015年 | 9698篇 |
2014年 | 11957篇 |
2013年 | 15534篇 |
2012年 | 18421篇 |
2011年 | 19277篇 |
2010年 | 14300篇 |
2009年 | 14233篇 |
2008年 | 14987篇 |
2007年 | 13717篇 |
2006年 | 13071篇 |
2005年 | 11395篇 |
2004年 | 8625篇 |
2003年 | 7152篇 |
2002年 | 6644篇 |
2001年 | 5742篇 |
2000年 | 5258篇 |
1999年 | 5392篇 |
1998年 | 4562篇 |
1997年 | 3970篇 |
1996年 | 3987篇 |
1995年 | 3534篇 |
1994年 | 3074篇 |
1993年 | 2651篇 |
1992年 | 2317篇 |
1991年 | 1955篇 |
1990年 | 1602篇 |
1989年 | 1243篇 |
1988年 | 968篇 |
1987年 | 795篇 |
1986年 | 744篇 |
1985年 | 656篇 |
1984年 | 469篇 |
1983年 | 408篇 |
1982年 | 321篇 |
1981年 | 230篇 |
1980年 | 168篇 |
1979年 | 101篇 |
1978年 | 100篇 |
1976年 | 95篇 |
1975年 | 94篇 |
1973年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
161.
Wang Hay Kan Chenxi Wei Dongchang Chen Tao Bo Bao‐Tian Wang Yan Zhang Yangchao Tian Jun‐Sik Lee Yijin Liu Guoying Chen 《Advanced functional materials》2019,29(17)
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes. 相似文献
162.
Yang Yueyi Wang Lide Chen Huang Wang Chong 《Analog Integrated Circuits and Signal Processing》2021,107(3):605-616
Analog Integrated Circuits and Signal Processing - Fault diagnosis of analog circuit is critical to improve safety and reliability in electrical systems and reduce losses. Traditional fault... 相似文献
163.
Monomeric sarcosine oxidase (mSOx) fusion with the silaffin peptide, R5, designed previously for easy protein production in low resource areas, was used in a biosilification process to form an enzyme layer electrode biosensor. mSOx is a low activity enzyme (10–20 U/mg) requiring high amounts of enzyme to obtain an amperometric biosensor signal, in the clinically useful range <1 mM sarcosine, especially since the Km is >10 mM. An amperometric biosensor model was fitted to experimental data to investigate dynamic range. mSOx constructs were designed with 6H (6×histidine) and R5 (silaffin) peptide tags and compared with native mSOx. Glutaraldehyde (GA) cross‐linked proteins retained ~5 % activity for mSOx and mSOx‐6H and only 0.5 % for mSOx‐R5. In contrast R5 catalysed biosilification on (3‐mercaptopropyl) trimethoxysilane (MPTMS) and tetramethyl orthosilicate (TMOS) particles created a ‘self‐immobilisation’ matrix retaining 40 % and 76 % activity respectively. The TMOS matrix produced a thick layer (>500 μm) on a glassy carbon electrode with a mediated current due to sarcosine in the clinical range for sarcosinemia (0–1 mM). The mSOx‐R5 fusion protein was also used to catalyse biosilification in the presence of creatinase and creatininase, entrapping all three enzymes. A mediated GC enzyme linked current was obtained with dynamic range available for creatinine determination of 0.1–2 mM for an enzyme layer ~800 nm. 相似文献
164.
165.
166.
167.
168.
169.
Highly dispersed palladium nanoclusters incorporated in amino‐functionalized silica spheres for the selective hydrogenation of succinic acid to γ‐butyrolactone 下载免费PDF全文
Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO2‐NH2) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO2‐NH2 catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO2‐NH2 catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
170.
Francesco Segatta David M. Rogers Naomi T. Dyer Ellen E. Guest Zhuo Li Hainam Do Artur Nenov Marco Garavelli Jonathan D. Hirst 《Molecules (Basel, Switzerland)》2021,26(2)
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains. 相似文献