全文获取类型
收费全文 | 911篇 |
免费 | 43篇 |
国内免费 | 3篇 |
专业分类
化学 | 724篇 |
晶体学 | 32篇 |
力学 | 12篇 |
数学 | 50篇 |
物理学 | 139篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 21篇 |
2018年 | 32篇 |
2017年 | 19篇 |
2016年 | 24篇 |
2015年 | 43篇 |
2014年 | 25篇 |
2013年 | 59篇 |
2012年 | 66篇 |
2011年 | 50篇 |
2010年 | 28篇 |
2009年 | 32篇 |
2008年 | 39篇 |
2007年 | 55篇 |
2006年 | 43篇 |
2005年 | 47篇 |
2004年 | 32篇 |
2003年 | 26篇 |
2002年 | 40篇 |
2001年 | 21篇 |
2000年 | 18篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1969年 | 2篇 |
排序方式: 共有957条查询结果,搜索用时 15 毫秒
101.
Vijay Singh Jun-Jie Zhu Manoj Tiwari Manish Soni Mahendra Aynayas Seok-Hee Hyun R. Narayanan Manoj Mohapatra V. Natarajan 《Journal of Non》2009,355(50-51):2491-2495
Strong blue-green light emitting Eu doped SrAl2O4 phosphor was synthesized by a low-temperature initiated, self-propagating and gas producing combustion process in a very short time (<5 min). The prepared powder was characterized by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy. The excitation spectrum shows a peak at 397 nm. Upon excitation at 397 nm, the emission spectrum exhibits a well defined broad band with maximum at 493 nm corresponding to 4f65d → 4f7 transition. Electron paramagnetic resonance (EPR) measurements at X-band showed low field signals due to Eu2+ ions in SrAl2O4:Eu. 相似文献
102.
Prabhakaran R Kalaivani P Poornima P Dallemer F Paramaguru G Vijaya Padma V Renganathan R Huang R Natarajan K 《Dalton transactions (Cambridge, England : 2003)》2012,41(31):9323-9336
One pot synthesis of three structurally different Ni(II) thiosemicarbazone complexes 1, 2 and 3 were obtained from the reaction between [NiCl(2)(PPh(3))(2)], 1,2-bis(diphenylphosphino)ethane, and [H(2)-(Sal-tsc)]. The obtained products were characterized by various spectral and analytical techniques. From the X-ray crystallographic analysis, an unexpected N-arylation on the coordinated salicylaldehydethiosemicarbazone was found in complex 2. The comparative biological evolutions such as DNA/protein binding, antioxidant, cytotoxicity (MTT, LDH, and NO) and cellular uptake studies have been examined for [Ni(Sal-tsc)(PPh(3))] (1) and [(Ni(Sal-tsc))(2)(μ-dppe)] (3). When comparing the cytotoxicity of the complexes, 1 exhibited higher activity than 2 and 3 and by comparing with standard cis-platin, both of them were found to exhibit better activity under identical conditions. 相似文献
103.
Schellinger JG Kudupudi A Natarajan A Du W DeNardo SJ Gervay-Hague J 《Organic & biomolecular chemistry》2012,10(8):1521-1526
Multivalent single chain variable fragments (scFv) show increased affinity to tumor-associated antigens compared to monovalent scFv and intact monoclonal antibodies (mAb). Multivalent constructs can be derived from self-associating or covalent scFv with covalent constructs offering improved in vivo and in vitro stability. Covalent attachment of scFv can be achieved using genetically engineered expression vectors that afford scFv with site specific cysteine functionality. Expression vectors for di-scFv-C wherein the cysteine is located in the center of two scFv have also been developed for attaching chemically reactive linkers. In the example illustrated here, the di-scFv-C is derived from a mAb directed against the MUC1 epitope, which is presented on cancer cells. To achieve multivalency, a chemical crosslinking strategy utilizing various azide and multi-alkyne functionalized polyethylene glycol (PEG) linkers was implemented. Conjugation was achieved by attachment of these linkers to the scFv thiol functionality. Chemoselective ligation was employed to covalently link different protein conjugates via copper(I) catalyzed azide alkyne 1,3-dipolar cycloaddition reaction (CuAAC) chemistry. Ligations were achieved in >70% yield using a specific set of linkers as determined by SDS-PAGE and densitometry. ELISA showed increased tumor binding of a tetravalent scFv providing a versatile chemical crosslinking strategy for construction of multivalent and bi-specific immunoconjugates that retain biological activity and have potential application in pre-targeted radioimmunotherapy and imaging. 相似文献
104.
Bonneau D Lobino M Jiang P Natarajan CM Tanner MG Hadfield RH Dorenbos SN Zwiller V Thompson MG O'Brien JL 《Physical review letters》2012,108(5):053601
We demonstrate fast polarization and path control of photons at 1550?nm in lithium niobate waveguide devices using the electro-optic effect. We show heralded single photon state engineering, quantum interference, fast state preparation of two entangled photons, and feedback control of quantum interference. These results point the way to a single platform that will enable the integration of nonlinear single photon sources and fast reconfigurable circuits for future photonic quantum information science and technology. 相似文献
105.
Karthik Vikram Siva Shanmugam J. Scott Parent Ralph A. Whitney 《European Polymer Journal》2012,48(4):841-849
Solid-state rheometry and model compound reactions are used to investigate free radical reactions of N-arylmaleimide coagents with saturated and unsaturated polymers. N,N′-m-phenylene dimaleimide (BMI) is shown to provide superior cross-link densities over diacrylate and diallyl coagents for all of the polymers studied, including linear low density polyethylene (LLDPE), poly(ethylene oxide) (PEO), cis-poly(butadiene) (PBD) and cis-poly(isoprene) (PIP). Studies of the N-phenylmaleimide (NPM) + cis-cyclooctane system show that C–H bond addition to yield N-aryl-2-alkylsuccimide grafts is the predominant reaction pathway, as opposed to maleimide homopolymerization. In contrast, peroxide-initiated reactions of cis-cyclooctene with small NPM concentrations generate highly alternating poly(cycloctene-alt-N-phenylmaleimide) in high yield, indicating that unsaturated mers in materials such as PBD engage maleimides in an efficient alternating copolymerization between electron-rich and electron-deficient monomer pairs. Factors that affect the reactivity of different polymers in these C–H bond additions and alternating copolymerizations are discussed. 相似文献
106.
Deepak?D.?Dicholkar Lalit?K.?Patil Vilas?G.?Gaikar Shekhar?KumarEmail author U.?Kamachi Mudali R.?Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):739-743
The high performance liquid chromatography and gas chromatography methods were investigated for their applicability in determining
micro-level concentrations of tri-n-butyl phosphate (TBP). A high performance liquid chromatograph (HPLC) equipped with refractive
index detector was used in determining TBP up to 2 ppm concentration level in the aqueous nitric acid solutions. The gas chromatography
incorporated with Thermionic Detector (NPD) and Flame Photometric Detector (FPD) were examined for their potential in analyzing
TBP in organic phase up to sub-ppm level. The results indicated that HPLC-RI technique is well suited for direct analysis
of aqueous phase. For organic phase analysis, gas chromatographic methods with the TID and FPD were suitable but performance
of detectors deteriorated often due to fouling. 相似文献
107.
Biplab Das Shekhar Kumar P. Mondal U. Kamachi Mudali R. Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):1161-1171
Red-oil is a mixture of nonspecific composition consisting of extractant, degradation products, nitrated solvent and unidentified
red-coloured nitro-organics. Red-oil formation is coupled with decomposition of extractant and diluent into gases of explosive
nature. If ignited or incinerated, these gases may cause rapid pressurization and endanger the integrity of containment. Such
an event occurred at Tomsk-7 facility in 1993. To ensure safe operation, red-oil formation has to be avoided in the fuel cycle
facilities by a careful combination of several independent measures like strict control over temperature, limiting organic
entrainment in the aqueous streams (which are to be concentrated by evaporation) and control over acidity of aqueous phases.
Since tri-iso amyl phosphate (TiAP) has much lower aqueous solubility as compared to TBP, it is visualized as alternate solvent for PUREX
process. In this work, TiAP red-oil was synthesized and characterized. 相似文献
108.
L. Natarajan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):287-292
In this work, the multiplet splitting in terms of a spin-dependent model is analyzed. The spin-polarized and unpolarized single
configuration Dirac-Fock-Slater wavefunctions have been used in the evaluation of the total energies of highly ionized argon
with different L shell population The transition energies of hollow argon atom with initial configurations 1s
0
1/22s
m
1/22p
n
1/22p
l
3/2 with m = 0 to 2 and n + l varying from 6 to 1 are reported in this work. The calculations have been carried out by taking into account a relativistic
exchange potential in the Dirac-Slater potential. To account for the correlation effects, a correction term has also been
considered perturbatively. The present calculations show that the spin-polarized technique which is mainly applied to the
ground states of atoms may also be applied to atoms ionized in the inner shells with a good degree of accuracy.
Received 5 December 2000 and Received in final form 9 April 2001 相似文献
109.
Single crystals of L‐Prolinium tartrate (C5H10NO2)+ (C4H5O6)‐, a new organic non‐linear optical material of size: 15 × 10 × 10 mm3 were grown using submerged seed solution growth method. Characterization of the crystals was made using single crystal X‐ray diffraction and density determination. Spectroscopic, thermal, optical and mechanical studies were carried out. These studies show that the crystals are thermally stable upto 161°C, transparent for the fundamental and second harmonic generation of Nd: YAG (λ = 1064 nm) laser and possess good mechanical strength. Second harmonic generation (SHG) conversion efficiency was investigated to explore the NLO characteristics of this material using Kurtz and Perry method and it was found that the SHG conversion efficiency is about 90% of that of the standard KDP crystals. Laser damage threshold study was also carried out. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
110.
R. V. Krishnakumar M. Subha Nandhini S. Natarajan K. Sivakumar Babu Varghese 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1149-1150
The glycine molecule in the title compound, Na(NO3)·C2H5NO2, exists in the zwitterionic form. The Na atom exhibits eightfold coordination and the polyhedron may be visualized as a distorted hexagonal bipyramid. The glycine molecules are linked through head-to-tail hydrogen bonds and are found `sandwiched' between the Na(NO3) layers. 相似文献