全文获取类型
收费全文 | 3083篇 |
免费 | 92篇 |
国内免费 | 391篇 |
专业分类
化学 | 3087篇 |
晶体学 | 20篇 |
力学 | 4篇 |
综合类 | 14篇 |
数学 | 106篇 |
物理学 | 335篇 |
出版年
2024年 | 1篇 |
2023年 | 80篇 |
2022年 | 65篇 |
2021年 | 96篇 |
2020年 | 107篇 |
2019年 | 84篇 |
2018年 | 97篇 |
2017年 | 142篇 |
2016年 | 139篇 |
2015年 | 90篇 |
2014年 | 158篇 |
2013年 | 480篇 |
2012年 | 256篇 |
2011年 | 170篇 |
2010年 | 136篇 |
2009年 | 150篇 |
2008年 | 159篇 |
2007年 | 195篇 |
2006年 | 176篇 |
2005年 | 152篇 |
2004年 | 146篇 |
2003年 | 92篇 |
2002年 | 69篇 |
2001年 | 26篇 |
2000年 | 30篇 |
1999年 | 40篇 |
1998年 | 30篇 |
1997年 | 28篇 |
1996年 | 19篇 |
1995年 | 27篇 |
1994年 | 26篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有3566条查询结果,搜索用时 31 毫秒
171.
Venkatanarayana Pappula Ramachandra Reddy DonthiriChandra Mohan Darapaneni Adimurthy Subbarayappa 《Tetrahedron letters》2014
Synthesis of β-bromostyrenes from styrene bromohydrins using H-β-zeolite as catalyst under moderate conditions is reported. The catalyst could be regenerated and reused up to three consecutive cycles. 相似文献
172.
Use of the calcium-ethylenediamine and sodium-liquid ammonia reduction systems for the ring opening of dihydropyran derivatives was studied. (Z)-Alkenyl alcohols and (E)-alkenyl alcohols were stereoselectively synthesized respectively. 相似文献
173.
Vera I. Filyakova Nadezhda S. Boltacheva Marina G. Pervova Valery N. Charushin 《Mendeleev Communications》2021,31(3):388-389
- Download : Download high-res image (44KB)
- Download : Download full-size image
174.
- Download : Download high-res image (193KB)
- Download : Download full-size image
175.
Christian A. Malapit Donald R. Caldwell Irungu K. Luvaga Dr. Jonathan T. Reeves Dr. Ivan Volchkov Dr. Nina C. Gonnella Dr. Zhengxu S. Han Dr. Carl A. Busacca Prof. Dr. Amy R. Howell Dr. Chris H. Senanayake 《Angewandte Chemie (International ed. in English)》2017,56(24):6999-7002
β-Ketonitriles bearing a quaternary carbon at the 2-position were prepared through Rh-catalyzed addition of aryl boronic acids to 2,2-disubstituted malononitriles. In contrast to the previously described transnitrilative cyanation of aryl boronic acids with dialkylmalononitriles, the present reaction avoids retro-Thorpe collapse of the intermediate addition product through the use of a milder base. The reaction was amenable to a variety of aryl boronic acids and disubstituted malononitriles, providing a diverse array of β-ketonitriles. The products could be further derivatized to valuable chiral α,α-disubstituted-β-aminonitriles through addition reactions to the corresponding N-tert-butanesulfinyl imines. 相似文献
176.
Simulation of near-infrared photodiode detectors based on β-FeSi_2/4H-SiC heterojunctions 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper,we propose a near-infrared p-type β-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide(β-FeSi2) as the active region for the first time.The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature.The results show that the photodetector has a good rectifying character and a good response to near-infrared light.Interface states should be minimized to obtain a lower reverse leakage current.The response spectrum of the β-FeSi2/4H-SiC detector,which consists of a p-type β-FeSi2 absorption layer with a doping concentration of 1×1015cm-3 and a thickness of 2.5 μm,has a peak of 755 mA/W at 1.42 μm.The illumination of the SiC side obtains a higher responsivity than that of the β-FeSi2 side.The results illustrate that the β-FeSi2/4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices. 相似文献
177.
Dr. Subhabrata Chaudhury Dr. Penchala Narasimharao Meka Dr. Monimoy Banerjee Caitlin N. Kent Prof. Dr. Brian S. J. Blagg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(59):14747-14764
The 90 kDa heat shock proteins (Hsp90) are molecular chaperones that are responsible for the folding and/or trafficking of ∼400 client proteins, many of which are directly associated with cancer progression. Consequently, inhibition of Hsp90 can exhibit similar activity as combination therapy as multiple signaling nodes can be targeted simultaneously. In fact, seventeen small-molecule inhibitors that bind the Hsp90 N-terminus entered clinical trials for the treatment of cancer, all of which exhibited pan-inhibitory activity against all four Hsp90 isoforms. Unfortunately, most demonstrated undesired effects alongside induction of the pro-survival heat shock response. As a result, isoform-selective inhibitors have been sought to overcome these detriments. Described herein is a structure-based approach to design Hsp90β-selective inhibitors along with preliminary SAR. In the end, compound 5 was shown to manifest ∼370-fold selectivity for Hsp90β versus Hsp90α, and induced the degradation of select Hsp90β-dependent clients. These data support the development of Hsp90β-selective inhibitors as a new paradigm to overcome the detriments associated with pan-inhibition of Hsp90. 相似文献
178.
Jihen Mahfoudh Christelle Delaite Souhir Abid Rachid El Gharbi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1002-1008
A series of random polyesteramides (PEAs) within a range of molar composition from 90/10 to 10/90 were synthesized by a direct melt polycondensation of lactic acid and β-alanine. Their structures were fully characterized by NMR spectroscopy. The resulting copolymers are amorphous; they are thermally stable to temperatures up to 254°C, and present increasing glass transition temperatures at increasing amide content. The copolymers were also characterized by FTIR and viscosimetry measurements. 相似文献
179.
Yakun Wang Qinghe Gao Nan Li Yifan Chen Jingwen Cui Feiyu Gao Qingwei Meng 《Tetrahedron》2018,74(30):4126-4133
A facile and efficient protocol for α-benzoyloxylation and α-hydroxylation of β-keto amides by phase-transfer catalysis is presented. This methodology provides mild and practical access to a variety ofα-oxygenated β-keto amides. Furthermore, α-benzoyloxylation products can be easily converted into α-hydroxylation compounds, which are useful synthetic precursors of biological targets. 相似文献
180.
Phthalimide derivatives as nitrogen nucleophiles with α,β‐unsaturated aldehydes for asymmetric aza‐Michael additions have been reported. The reactions proceed smoothly to afford corresponding Michael adducts in good yields (up to 98%) and enantioselectivities (up to 95% ee). 相似文献