全文获取类型
收费全文 | 905篇 |
免费 | 32篇 |
国内免费 | 6篇 |
专业分类
化学 | 732篇 |
晶体学 | 6篇 |
力学 | 4篇 |
数学 | 114篇 |
物理学 | 87篇 |
出版年
2023年 | 11篇 |
2022年 | 31篇 |
2021年 | 24篇 |
2020年 | 19篇 |
2019年 | 21篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 43篇 |
2015年 | 35篇 |
2014年 | 42篇 |
2013年 | 62篇 |
2012年 | 58篇 |
2011年 | 74篇 |
2010年 | 36篇 |
2009年 | 30篇 |
2008年 | 57篇 |
2007年 | 43篇 |
2006年 | 51篇 |
2005年 | 48篇 |
2004年 | 29篇 |
2003年 | 24篇 |
2002年 | 30篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1965年 | 7篇 |
排序方式: 共有943条查询结果,搜索用时 0 毫秒
1.
Europium (Eu+) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu+ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal
was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal
amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions.
The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both
experimentally and theoretically. 相似文献
2.
Ying Chen Anita E. Tavakley Tate M. Mathiason T. Andrew Taton 《Journal of polymer science. Part A, Polymer chemistry》2006,44(8):2604-2614
Photocrosslinkable poly(vinylbenzophenone)‐containing polymers were synthesized via a one‐step, Friedel–Crafts benzoylation of polystyrene‐containing starting materials [including polystyrene, polystyrene‐block‐poly(tert‐butyl acrylate), polystyrene‐block‐poly(ethylene oxide), polystyrene‐block‐poly(methyl methacrylate), and polystyrene‐block‐poly(n‐butyl acrylate)] with benzoyl trifluoromethanesulfonate as a benzoylation reagent. The use of this mild reagent (which required no added Lewis acid) permitted polymers with well‐defined compositions and narrow molecular weight distributions to be synthesized. Micelles formed from one of these benzoylated polymers, [polystyrene0.25‐co‐poly(vinylbenzophenone)0.75]115‐block‐poly(acrylic acid)14, were then fixed by the irradiation of the micelle cores with UV light. As the irradiation time was increased, the pendent benzophenone groups crosslinked with other chains in the glassy micelle cores. Dynamic light scattering, spectrofluorimetry, and Fourier transform infrared spectroscopy were all used to verify the progress of the crosslinking reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2604–2614, 2006 相似文献
3.
Triorganotin(IV) and triorganolead(IV) derivatives of the types Me3Sn(SCZ) and Ph3Pb(SCZ) (where SCZ? is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and 1H, 13C and 119Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper. 相似文献
4.
Kinetics of oxidation of lactose, maltose, cellobiose and melibiose has been studied by hexacyanoferrate(III) in the presence of ammonia. A general mechanism involving the formation of intermediate enodiol anion has been suggested. The effects of dielectric constant and salts have been studied in detail. The oxidation products have been characterised by descending paper chromatography. Compensation effects have been observed. 相似文献
5.
Anita Tabacco Vignati 《Annali di Matematica Pura ed Applicata》1994,166(1):145-153
Sia D il dominio di Siegel e Hn il gruppo di Heisenberg. Si considera il sistema ortogonale ottenuto dai monomi normalizzati delta palla unitaria di
n+1 tramite la trasformata di Cayley. La trasformata di Fourier di tali funzioni ristrette ad Hn viene esplicitamente calcolata. Rispetto alla base di Hermite di L2(
n
), si ottengono operatori di rango uno espressi in termini di funzioni di Laguerre. 相似文献
6.
John A. Montgomery Anita T. Shortnacy Sarah D. Clayton 《Journal of heterocyclic chemistry》1977,14(2):195-197
The reaction of the trimethylsilyl derivative of 4,6-dichloroimidazo[4,5-c]pyridine with 2,3,5-tri-O-benzoyl- D -ribofuranosyl bromide gave four nucleosides-the α- and β-anomers of the 1-isomer and the α- and β-anomers of the 3-isomer (3.9:2.7:1.5:1). In contrast, the fusion reaction of 4,6-dichloroimidazo[4,5-c ]pyridine with 1,2,3,5-tetra-O-acetyl-β- D -ribofuranose gave a high yield of the 1-β-isomer, which was converted to the known 3-deazaadenosine (4-amino-l-β- D -ribofuranosylimidazo[4,5-c]pyridine). 相似文献
7.
Douglas O. Spry Anita R. Bhala Wayne A. Spitzer Noel D. Jones John K. Swartzendruber 《Tetrahedron letters》1984,25(24):2531-2534
The major product from the thermolysis and photolysis of C(3)-azido cephem 2 is the ring expanded 1,4,6-thiadiazepine azetidinone. 相似文献
8.
Virendra Singh Anita Rampal S. N. Biswas K. Datta 《Letters in Mathematical Physics》1980,4(2):131-134
The solution of a difference equation in the form of an infinite continued fraction is used to obtain a class of exact solutions for the eigenfunctions and eigenvalues of doubly anharmonic oscillators described by potentials of the type (1/2)2x2+(1/4)x4+(1/6)x6, n>0, provided certain constraints on the couplings are satisfied. The class is denumerably infinite but not complete. 相似文献
9.
A high-performance liquid chromatographic procedure is described for the quantitative determination of epinephrine, norepinephrine, and dopamine in human plasma. The method, which is based on adsorption of the catecholamines to alumina and, after liberation, separation on a microparticulate bonded strong cation-exchange resin and amperometric detection, has been optimized to give complete baseline separation of the substances of interest. Dihydroxybenzylamine, a nonendogenous catecholamine, is used as the internal standard. The detection limit is about 0.1 pmol for dopamine. Analysis of data obtained for norepinephrine and epinephrine from a total of 59 plasma samples showed a good correlation to the corresponding values obtained with a radioenzymatic method. Some results from normal and pathological conditions are compared. 相似文献
10.
Gredson Keiff Souza Andr Gallo Luiza Hauser Novicki Heitor Rodrigues Neto Eneida de Paula Anita Jocelyne Marsaioli Luis Fernando Cabea 《Molecules (Basel, Switzerland)》2022,27(13)
The drugs delivery system in the treatment of diseases has advantages such as reduced toxicity, increased availability of the drug, etc. Therefore, studies of the supramolecular interactions between local anesthetics (LAs) butamben (BTB) or ropivacaine (RVC) complexed with 2-hydroxypropyl-β-cyclodextrin (HP-βCD) and carried in Stealth liposomal (SL) are performed. 1H-NMR nuclear magnetic resonance (DOSY and STD) were used as the main tools. The displacements observed in the 1H-NMR presented the complexion between LAs and HP-βCD. The diffusion coefficients of free BTB and RVC were 7.70 × 10−10 m2 s−1 and 4.07 × 10−10 m2 s−1, and in the complex with HP-βCD were 1.90 × 10−10 m2 s−1 and 3.64 × 10−10 m2 s−1, respectively, which indicate a strong interaction between the BTB molecule and HP-βCD (98.3% molar fraction and Ka = 72.279 L/mol). With STD-NMR, the encapsulation of the BTB/HP-βCD and RVC/HP-βCD in SL vesicles was proven. Beyond the saturation transfer to the LAs, there is the magnetization transfer to the hydrogens of HP-βCD. BTB and RVC have already been studied in normal liposome systems; however, little is known of their behavior in SL. 相似文献