全文获取类型
收费全文 | 518篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 310篇 |
晶体学 | 40篇 |
力学 | 23篇 |
数学 | 62篇 |
物理学 | 97篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 26篇 |
2021年 | 20篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 18篇 |
2014年 | 29篇 |
2013年 | 46篇 |
2012年 | 35篇 |
2011年 | 37篇 |
2010年 | 21篇 |
2009年 | 20篇 |
2008年 | 40篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 18篇 |
2004年 | 22篇 |
2003年 | 7篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1985年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有532条查询结果,搜索用时 9 毫秒
521.
Vivek Kumar P. Thakur A. K. Bhati R. P. Singh R. K. Bhowmik 《Hyperfine Interactions》2007,175(1-3):121-129
The spectroscopic quadrupole moments of the K π = 8? isomers in 170Hf and 172Hf, Q s ?=?4.91(17) b and 5.40(19) b, respectively and Q s ?=?4.92(17) b for K π ?=?23/2? in 171Hf have been measured using the time differential perturbed angular distribution technique. The nuclear reaction 160Gd(16O, xnγ) was used to excite the respective isomeric states and for the recoil implantation of Hf nuclei into the Hf foil. The quadrupole deformation for the 8? isomer and the ground state has the same value. The deformation corresponding to 23/2? isomeric state is observed to be reduced with respect to the ground state due to the i 13/2 neutron alignment. The results are in good agreement with the multi-quasiparticle calculations. 相似文献
522.
Redox enzymes catalyze major reactions in microorganisms to supply energy for life. Their use in electrochemical biodevices requires their integration on electrodes, while maintaining their activity and optimizing their stability. In return, such applicative development puts forward the knowledge on involved catalytic mechanisms, providing a direct electrode connection of the enzyme is fulfilled. Enzymes being large molecules with active site embedded in an insulating moiety, direct bioelectrocatalysis supposes strategies for specific orientation of the enzyme to be developed. In this review, we summarize recent advances during the past 3 years in the chemical modification of electrodes favoring direct electrocatalysis. We present the different methodologies used according to the electrode materials, including metals, carbon-based electrodes, or porous structures and discuss the gained insights into bioelectrocatalysis. We especially focus on enzyme engineering, which appears as an emerging strategy for enzyme anchoring. Remaining challenges will be discussed with regard to these later findings. 相似文献
523.
Balasubramanian Mariammal Adaikalam Shylaja Sundaravel Vivek Kumar Stephen Raja Rubina Raju Ranjith Kumar 《Journal of heterocyclic chemistry》2020,57(11):3882-3889
3-Amino-5-(thiazol-2-yl)-[1,1′-biaryl]-2,4-dicarbonitriles have been synthesized employing a facile one-pot pseudo four-component domino strategy. All these thiazole-tethered biaryls exhibited blue fluorescence under UV lamp. Based on the high relative quantum yield, three compounds namely, 4a , 4d , and 4i , were chosen to explore the metal interference studies. Against several metal ions, these three thiazole-tethered biphenyl probes were found to be effective fluorescent chemosensors for the selective and sensitive detection of Fe3+ ions with a lower detection limit of 0.18, 0.12, and 0.16 μM, respectively. 相似文献
524.
We demonstrate the realization of fundamental logic operations, as well as a memory element, with engineered delayed synthetic gene networks. Further, we investigate the effect of time delay in different kinds of processes, on the operational range of this biological logic gate. We show that this delay can either enhance or diminish logic behavior, depending on its functional form. Lastly, we show that the desired response to inputs can be induced, even in the absence of noise, by time delay alone. 相似文献
525.
Manisha M.Kodape Anand S.Aswar Nandkishor D.Gawhale Vivek T.Humne Bilal Ahmad Mir 《中国化学快报》2012,23(12):1339-1342
A facile aromatization of 3,4-dihydropyrimidin-2(1H)-ones using iodine in dimethyl sulfoxide under microwave irradiation was carried out which is more efficient and gives high yield in less time;presently it is the most important catalyst for dehydrogenation. 相似文献
526.
Substituted 3-formylchromones react with 2-phenyl-4-dimethylamino-1-thia-3-azabuta-1,3-diene (4) or thio-benzamide (7) by heating their toluene solution in a sealed tube to give novel substituted 3-(5-phenyl-3H-[1,2,4]dithiazol-3-yl)chromen-4-ones (6a-e) in high yields. 相似文献
527.
Shear-induced orientation of a rigid surfactant mesophase 总被引:1,自引:0,他引:1
Singh M Agarwal V De Kee D McPherson G John V Bose A 《Langmuir : the ACS journal of surfaces and colloids》2004,20(14):5693-5702
An optically clear, crystalline, gel-like mesophase is formed by the addition of water to a micellar solution consisting of a mixture of 0.85 M anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and a 0.42 M zwitterionic surfactant phosphatidylcholine (lecithin) in isooctane. At 25 degrees C and water to AOT molar ratio of 70, the system has a columnar hexagonal microstructure with randomly oriented domains. The shear-induced orientation and subsequent relaxation of this structure were investigated by rheological characterization and small-angle neutron scattering (SANS). The rheological response implies that the domains align under shear, and remain aligned for several hours after cessation of shear. Shear-SANS confirms this picture. The sheared gel mesophase retains its alignment as the temperature is increased to 57 degrees C, indicating the potential to conduct templated polymer and polymer-ceramic composite materials synthesis in aligned systems. 相似文献
528.
Baljinder Singh Rajinder Parshad R.K. Khajuria Santosh K. Guru Anup S. Pathania Rashmi Sharma Reena Chib Subrayashastry Aravinda Vivek K. Gupta Inshad A. Khan Shashi Bhushan Sandip B. Bharate Ram A. Vishwakarma 《Tetrahedron letters》2013
From an antimicrobial gram-positive actinomycete strain of Saccharomonospora azurea (MTCC11714) isolated from high altitude soil of Kargil (J&K, India), a new isocoumarin saccharonol B (2) along with two known compounds viz. saccharonol A (1) and piericidin A3 (3) was isolated and characterized. The structure of the new compound was established based on extensive 2D-NMR data. Saccharonol B (2) exhibited mild antimicrobial activity against a standard panel of microorganisms Staphylococcus aureus ATCC 29213, Candida albicans ATCC 90028, and Aspergillus fumigatus MTCC 1811 with MIC values in the range of 128–248 μg/mL. Saccharonol B (2) and piericidin A3 (3) showed selective cytotoxic activity against human pancreatic carcinoma cell line (MIAPaCa-2) with IC50 values of 9 and 8 μM, respectively. Mechanistic studies indicated that saccharonol B (2) arrests S-phase of the cell cycle and causes dose-dependent loss of mitochondrial potential in MIAPaCa-2 cells. 相似文献
529.
Samar Azizighannad Zhiqian Wang Zain Siddiqui Vivek Kumar Somenath Mitra 《Molecules (Basel, Switzerland)》2021,26(9)
Novel polyacrylamide gel electrolytes (PGEs) doped with nano carbons with enhanced electrochemical, thermal, and mechanical properties are presented. Carboxylated carbon nanotubes (fCNTs), graphene oxide sheets (GO), and the hybrid of fCNT/GO were embedded in the PGEs to serve as supercapacitor (SC) electrolytes. Thermal stability of the unmodified PGE increased with the addition of the nano carbons which led to lower capacitance degradation and longer cycling life of the SCs. The fCNT/GO-PGE showed the best thermal stability, which was 50% higher than original PGE. Viscoelastic properties of PGEs were also improved with the incorporation of GO and fCNT/GO. Oxygen-containing functional groups in GO and fCNT/GO hydrogen bonded with the polymer chains and improved the elasticity of PGEs. The fCNT-PGE demonstrated a slightly lower viscous strain uninform distribution of CNTs in the polymer matrix and the defects formed within. Furthermore, ion diffusion between GO layers was enhanced in fCNT/GO-PGE because fCNT decreased the aggregation of GO sheets and improved the ion channels, increasing the gel ionic conductivity from 41 to 132 mS cm−1. Finally, MnO2-based supercapacitors using PGE, fCNT-PGE, GO-PGE, and fCNT/GO-PGE electrolytes were fabricated with the electrode-specific capacitance measured to be 39.5, 65.5, 77.6, and 83.3 F·g−1, respectively. This research demonstrates the effectiveness of nano carbons as dopants in polymer gel electrolytes for property enhancements. 相似文献
530.
Attar Singh Vivek K. Gupta Rajnikant K. N. Goswami 《Crystal Research and Technology》1995,30(7):991-996
The title compound, C16H14O5, a furanocoumarin crystallizes in the triclinic space group P1 . The unit cell parameters are a = 7.852(2), b = 8.485(1), c = 11.095(1) Å; α = 105.90(1), β = 103.18(2), γ = 95.07(1)°. The structure has been solved by direct methods. Final R = 0.048 for 1943 observed reflections. The furanocoumarin system is almost planar. The epoxide ring makes a dihedral angle with the fused ring system of 98.21(11)°. Molecules are held together by C—H… O hydrogen bonds. 相似文献