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991.
L. Zalazar C. A. I. Alonso R. E. De Castro A. Cesari 《Analytical and bioanalytical chemistry》2014,406(3):911-914
Immobilization of small proteins designed to perform protein–protein assays can be a difficult task. Often, the modification of reactive residues necessary for the interaction between the immobilized protein and the matrix compromises the interaction between the protein and its target. In these cases, glutathione-S-transferase (GST) is a valuable tag providing a long arm that makes the bait protein accessible to the mobile flow phase of the chromatography. In the present report, we used a GST fusion version of the 8-kDa protein serine protease inhibitor Kazal-type 3 (SPINK3) as the bait to purify anti-SPINK3 antibodies from a rabbit crude serum. The protocol for immobilization of GST-SPINK3 to glutathione–agarose beads was modified from previously reported protocols by using an alternative bifunctional cross-linker (dithiobis(succinimidyl propionate)) in a very simple procedure and by using simple buffers under physiological conditions. We concluded that the immobilized protein remained bound to the column after elution with low pH, allowing the reuse of the column for alternative uses, such as screening for other protein–protein interactions using SPINK3 as the bait. Figure
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992.
Cobalt Complexes with Pyrazole Ligands as Catalyst Precursors for the Peroxidative Oxidation of Cyclohexane: X‐ray Absorption Spectroscopy Studies and Biological Applications 下载免费PDF全文
Dr. Telma F. S. Silva Prof. Luísa M. D. R. S. Martins Prof. M. Fátima C. Guedes da Silva Dr. Maxim L. Kuznetsov Prof. Alexandra R. Fernandes Ana Silva Dr. Chun‐Jern Pan Dr. Jyh‐Fu Lee Prof. Bing‐Joe Hwang Prof. Armando J. L. Pombeiro 《化学:亚洲杂志》2014,9(4):1132-1143
[CoCl(μ‐Cl)(HpzPh)3]2 ( 1 ) and [CoCl2(HpzPh)4] ( 2 ) were obtained by reaction of CoCl2 with HC(pzPh)3 and HpzPh, respectively (HpzPh=3‐phenylpyrazole). The compounds were isolated as air‐stable solids and fully characterized by IR and far‐IR spectroscopy, MS(ESI+/?), elemental analysis, cyclic voltammetry (CV), controlled potential electrolysis, and single‐crystal X‐ray diffraction. Electrochemical studies showed that 1 and 2 undergo single‐electron irreversible CoII→CoIII oxidations and CoII→CoI reductions at potentials measured by CV, which also allowed, in the case of dinuclear complex 1 , the detection of electronic communication between the Co centers through the chloride bridging ligands. The electrochemical behavior of models of 1 and 2 were also investigated by density functional theory (DFT) methods, which indicated that the vertical oxidation of 1 and 2 (that before structural relaxation) affects mostly the chloride and pyrazolyl ligands, whereas adiabatic oxidation (that after the geometry relaxation) and reduction are mostly metal centered. Compounds 1 and 2 and, for comparative purposes, other related scorpionate and pyrazole cobalt complexes, exhibit catalytic activity for the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone under mild conditions (room temperature, aqueous H2O2). In situ X‐ray absorption spectroscopy studies indicated that the species derived from complexes 1 and 2 during the oxidation of cyclohexane (i.e., Ox‐ 1 and Ox‐ 2 , respectively) are analogous and contain a CoIII site. Complex 2 showed low in vitro cytotoxicity toward the HCT116 colorectal carcinoma and MCF7 breast adenocarcinoma cell lines. 相似文献
993.
Armando Zarrelli Marina DellaGreca Afef Ladhari Rabiaa Haouala Lucio Previtera 《Helvetica chimica acta》2013,96(6):1036-1045
Phytochemical investigation of the aerial parts of Gymnema sylvestre has led to the isolation of seven new triterpenes, six oleane types ( 5, 7 – 11 ) and a new lupane type ( 12 ), and of the six known analogues 1 – 4, 6 , and 13 . The structures and relative configurations of these compounds were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR spectroscopy and mass spectrometry, and by the comparison of their NMR data with those of related compounds. 相似文献
994.
Positivity - In this paper we consider Positive Definite functions on products $$\Omega _{2q}\times \Omega _{2p}$$ of complex spheres, and we obtain a condition, in terms of the coefficients in... 相似文献
995.
996.
The reactions of secondary alicyclic amines with the title substrate (PDTC) are subjected to a kinetic study in 44 wt.% aqueous ethanol, 25.0°C, ionic strength 0.2 M (KCl). Pseudo-first-order rate coefficients (kobs) are found under amine excess. Linear plots of [N]/kobs against 1/[N], where N is the free amine, are obtained for the reactions with piperidine, piperazine, 1-(2-hydroxyethyl)piperazine, and morpholine. The reaction with 1-formylpiperazine exhibits a linear plot of kobs against [N]2. These results are interpreted through a mechanism consisting of two tetrahedral intermediates: a zwitterionic ( T ±) and an anionic ( T ?), where the amine catalyzed proton transfer from T ± to T ? is partially rate determining for the four former reactions and is fully rate determining for the reaction of 1-formylpiperazine. The rate microcoefficients involved in the reaction scheme are either determined experimentally or estimated. Comparison with the corresponding microcoefficients reported for the same reactions in water reveals that the rate coefficient for formation of T ± from reactants (k1) is smaller and that for the reversal of this (k?1) is larger in aqueous ethanol compared to water, in agreement with the expected structure of the corresponding transition state. Bronsted-type plots are obtained for k1, k?1, and K1 (=k1/k?1) with slopes ca. 0.4, ?0.6, and 1.0, respectively. Comparison of the present stepwise reactions with the concerted ones found in the same aminolysis of O-ethyl 2,4,6,-(trinitrophenyl) dithiocarbonate indicates that T ± is so destabilized by the change of PhS by the 2,4,6-trinitrobenzenethio group that T ± no longer exists and becomes a transition state. © 1995 John Wiley & Sons, Inc. 相似文献
997.
998.
Controlling the surface chemistry of oxide systems has emerged an effective tool to obtain desirable nanostructures and macro properties. A relatively simple way to achieve this is by using dopants that are prone to segregate to the surfaces of the powders. In this work, we delineate the effect of Mg and Fe on SnO2 nanopowders focusing on the surface modifications caused by surface segregation. The effects of increasing the temperature of calcinations are particularly addressed to evaluate the surface modifications at high temperatures. The powders were studied by infrared spectroscopy, zeta potential measurements, X-ray diffraction, and specific surface area measurements. Since sintering is a high-temperature process strongly dependent on surface characteristics, we drawn a relationship between the final densities after sintering and the surface chemistry of the doped powders. Doped SnO2 pellets were sintered to over 95% of the theoretical density within a few seconds (fast firing) when significant surface modifications were observed. 相似文献
999.
I. Papaefstathiou U. Bilitewski M. D. Luque de Castro 《Analytical and bioanalytical chemistry》1997,357(8):1168-1173
A spectrophotometric method for the determination of acetaldehyde in liquid, semi-solid and solid food samples, employing
the coupling of a continuous flow configuration to a pervaporation unit, has been proposed. It is based on the reaction of
the analyte with fuchsin in acidic medium and subsequent formation of a coloured product (alkylsulphonic acid chromophore)
with sodium sulphite, which was monitored spectrophotometrically. Variable sensitivity was obtained by altering the pervaporation
temperature and the thickness of the membrane. The detection limits went down to 4.2 μg/mL and the precision was between 1.2
and 3.6%.
Received: 5 August 1996/Revised: 16 October 1996/Accepted: 18 October 1996 相似文献
1000.
C.E. Fellows C.C. Rodegheri U. Tauber K.H. Tsui M.P.P. de Castro C.E.M. Carvalho 《Applied physics. B, Lasers and optics》2004,78(3-4):421-424
This work reports the role of alpha particles generated by Americium (241Am) stripes placed inside the discharge channel in providing a bias ionized background plasma before, during, and after the discharge of the N2 TE UV laser (337.1 nm) circuit. The enhancement in stimulated radiation output characteristics in terms of gas pressure, charging voltage, and pulse width, with and without alpha particles, are shown. The increased laser yield is interpreted qualitatively through plasma impedance in the discharge circuit. PACS 42.60.By; 42.60.Lh 相似文献