全文获取类型
收费全文 | 1362篇 |
免费 | 37篇 |
国内免费 | 2篇 |
专业分类
化学 | 821篇 |
晶体学 | 37篇 |
力学 | 46篇 |
数学 | 187篇 |
物理学 | 310篇 |
出版年
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 19篇 |
2017年 | 20篇 |
2016年 | 27篇 |
2015年 | 26篇 |
2014年 | 34篇 |
2013年 | 114篇 |
2012年 | 68篇 |
2011年 | 83篇 |
2010年 | 42篇 |
2009年 | 42篇 |
2008年 | 74篇 |
2007年 | 62篇 |
2006年 | 65篇 |
2005年 | 54篇 |
2004年 | 46篇 |
2003年 | 39篇 |
2002年 | 27篇 |
2001年 | 24篇 |
2000年 | 18篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 14篇 |
1993年 | 17篇 |
1992年 | 15篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 30篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 20篇 |
1976年 | 16篇 |
1975年 | 20篇 |
1974年 | 13篇 |
1973年 | 15篇 |
1971年 | 11篇 |
1959年 | 11篇 |
排序方式: 共有1401条查询结果,搜索用时 15 毫秒
1.
2.
Xuejing Li Xingwang Deng Dr. Anthony G. Coyne Prof. Rajavel Srinivasan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8018-8023
Herein, we report the meta-nitration of arenes bearing ortho/para directing group(s) using the iridium-catalyzed C−H borylation reaction followed by a newly developed copper(II)-catalyzed transformation of the crude aryl pinacol boronate esters into the corresponding nitroarenes in a one-pot fashion. This protocol allows the synthesis of meta-nitrated arenes that are tedious to prepare or require multistep synthesis using the existing methods. The reaction tolerates a wide array of ortho/para-directing groups, such as −F, −Cl, −Br, −CH3, −Et, −iPr −OCH3, and −OCF3. It also provides regioselective access to the nitro derivatives of π-electron-deficient heterocycles, such as pyridine and quinoline derivatives. The application of this method is demonstrated in the late-stage modification of complex molecules and also in the gram-scale preparation of an intermediate en route to the FDA-approved drug Nilotinib. Finally, we have shown that the nitro product obtained by this strategy can also be directly converted to the aniline or hindered amine through Baran's amination protocol. 相似文献
3.
Journal of Solid State Electrochemistry - Development of high-performance energy storage devices is a vital research area to meet the present-day energy demand. In the work carried toward the... 相似文献
4.
This study evaluates the larvicidal activity of Scoparia dulcis aqueous extract against dengue vector and determines its major chemical components. The extract was tested at various concentrations ranging from 0.1 to 2 mg/mL against Aedes aegypti larvae. The extracts displayed significant larvicidal efficacy against Ae. aegypt species after 24 h exposure revealing LC50 of 3.3835 (mg/mL) and LC90 of 5.7578 (mg/mL). Finger printing profile carried out by CAMAG automatic TLC sample applicator programmed through WIN CATS software revealed peaks with different Rf values for three different volumes injected: 16, 15 and 18 peaks were spotted for 3, 6 and 9 μL, respectively. Ascending order of Rf values was also ascertained for each peak recorded. This study clearly signifies that S. dulcis extract contains numerous compounds that are known to have larvicidal properties which clearly substantiates its efficacy on Ae. aegypti larvae. 相似文献
5.
Rukmanikrishnan Balasubramanian Ramalingam Srinivasan Kim Sam Soo Lee Jaewoong 《Cellulose (London, England)》2021,28(9):5577-5590
Cellulose - Sustainable food packaging films were developed using a combination of k-Carrageenan (k-C), hydroxyl ethyl cellulose (HEC), silicon dioxide (SiO2), and silver (Ag) nanoparticles. The... 相似文献
6.
Woldemedhin M. T. Srinivasan J. Kelly R. G. 《Journal of Solid State Electrochemistry》2021,25(10):2699-2700
Journal of Solid State Electrochemistry - 相似文献
7.
8.
Varadharaj Ravi Srinivasan 《Journal of Pure and Applied Algebra》2018,222(6):1372-1374
9.
Slow evaporation of an aqueous solution containing l-threonine and magnesium sulphate heptahydrate, results in the fractional crystallization of the less soluble l-threonine crystal and not any novel optoelectronic ‘magnesium sulfate admixtured l-threonine’ crystal as reported by Puhal Raj et al. in Optik, 124 (2013) 6887–6891. 相似文献
10.
Sangya Chitranshi Dr. B. Adinarayana Mainak Das Dr. Won-Young Cha Prof. Dr. Dongho Kim Prof. Dr. A. Srinivasan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(56):12911-12915
Three distinct conformational structures of carbaoctaphyrins were prepared by incorporating bis-4,4'-biphenyl units in the macrocyclic core. The free-base form adopts a figure-eight conformation, whereas the protonation triggers a conformational change with a pyrrole ring inversion and acquires an open-framework structure. The insertion of bis-RhI metal ion in the macrocyclic core affords a singly twisted conformational structure. Furthermore, the local aromaticity in the bis-4,4'-biphenyl ring dominates the overall macrocyclic aromaticity in all three forms, and thus adopts nonaromatic characteristics. These results are supported by spectral as well as theoretical studies, and they are unambiguously confirmed by X-ray crystal analyses. 相似文献