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151.
Richard K. Johnson Audrey Zink-Sharp Wolfgang G. Glasser 《Cellulose (London, England)》2011,18(6):1599-1609
Amidation and ionic complexation were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONc),
using octadecylamine (ODA) as the modifying compound. Effects of the two treatments on TONc with respect to degree of ODA
substitution, surface hydrophobicity, crystalline characteristics, and thermal decomposition properties were investigated,
respectively, with elemental analysis, contact angle measurements, X-ray diffraction spectroscopy, and thermogravimetric analysis.
Both treatments resulted in complete substitution of TONc surface carboxyl groups with ODA, transforming TONc surfaces from
hydrophilic to hydrophobic. A slightly greater than one-to-one ODA-to-carboxyl ratio was found for the ionic complexation
product, giving it a more hydrophobic character than the amidation product. Furthermore, the ionic complexation product was
found to be surprisingly stable in acidic environment and was able to resist dissociation at fairly low pH. TONc from both
treatments could be readily dispersed in organic solvents of wide-ranging polarities, making ionic complexation an equally
effective surface modification approach as amidation for the hydrophobization of TONc surfaces. It was also found, through
X-ray diffraction results that the crystalline structure of TONc was preserved even after the surface modification treatments.
Finally, the thermal stability of TONc was slightly increased as a result of the surface modification treatments as evidenced
by slight shifts to higher values of TONc thermal decomposition temperature. 相似文献
152.
Back JH Zhu Y Calabro A Queenan C Kim AS Arbesman J Kim AL 《Photochemistry and photobiology》2012,88(5):1165-1172
Macroautophagy is a cellular response to various environmental stresses that ensures lysosomal degradation of long-lived and damaged proteins and cellular organelles. It occurs through the formation of an autophagosome, which then fuses with a lysosome to form an autolysosome. Depending on the cellular context, autophagy may promote cancer cell survival or it may serve as a mechanism of tumor suppression. Herein, we show that resveratrol, a natural phytoalexin, induces premature senescence in human A431 SCC cells, and that resveratrol-induced premature senescence is associated with a blockade of autolysosome formation, as assessed by the absence of colocalization of LC3 and Lamp-2, markers for autophagosomes and lysosomes, respectively. Further, we show that resveratrol downregulates the level of Rictor, a component of mTORC2, leading to decreased RhoA-GTPase and altered actin cytoskeleton organization. Exogenous overexpression of Rictor restores RhoA-GTPase activity and actin cytoskeleton network, and decreases resveratrol-induced senescence-associated β-gal activity, indicating a direct role of Rictor in senescence induction. Rictor is overexpressed in UV-induced murine SCCs, whereas its expression is diminished by oral administration of resveratrol. These data indicate that resveratrol attenuates autophagic process via Rictor, and suggest that downregulation of Rictor may be a mechanism of tumor suppression associated with premature senescence. 相似文献
153.
Ekomié A Lefèvre G Fensterbank L Lacôte E Malacria M Ollivier C Jutand A 《Angewandte Chemie (International ed. in English)》2012,51(28):6942-6946
Iron made'em: iron(II) complexes such as FeCl(2) and [FeCl(2)(dppe)(2) ] (dppe=1,2-bisdiphenylphosphinoethane) are efficient precatalysts for the radical cyclization of unsaturated iodides and bromides in the presence of NaBH(4). Cyclic voltammetry studies suggests that the reaction occurs through a radical mechanism via an anionic hydrido iron(I) species as the key intermediate for the activation of the substrates by electron transfer. 相似文献
154.
155.
L Weber H Kuhtz L Böhling A Brockhinke A Chrostowska A Dargelos A Mazière HG Stammler B Neumann 《Dalton transactions (Cambridge, England : 2003)》2012,41(34):10440-10452
A series of 1,4-phenylenes X-C(6)H(4)-BDB with a 1,3,2-benzodiazaborolyl (BDB) and a phosphorus based end group [X = PPh(2) (2), P(O)Ph(2) (3), P(S)Ph(2) (4), P(Se)Ph(2) (5), P(AuCl)Ph(2) (6) and P(Me)Ph(2) (7)] as well as 2-(2')thienyl-1,3,2-benzodiazaboroles with a second end group X [X = PPh(2) (8), P(S)Ph(2) (9), P(Se)Ph(2) (10) and P(Me)Ph(2) (11)] in the 5' position were synthesised using established methodologies. Molecular structures of 2-9 and 11 were determined by X-ray diffraction. Compounds 3, 4, 6, 7, 9 and 11 show intense blue luminescence in cyclohexane, toluene, chloroform, dichloromethane and tetrahydrofuran with pronounced solvatochromism. Thereby Stokes shifts in the range of 8950-10?440 cm(-1) and quantum yields up to 0.70 were observed in dichloromethane solutions. In contrast to this, for the selenides 5 and 10 quantum yields are small (<0.1). The absorption maxima (298-340 nm) are well reproduced by TD-DFT computations (B3LYB/G-311G(d,p)) and arise from strong HOMO-LUMO transitions. With the exception of 5 and 10 the HOMOs of the molecules under study are mainly located on the benzodiazaborole group. In 5 and 10 the HOMOs are on the selenium atoms. The LUMOs of all new neutral molecules are mainly represented by the phenylene or thiophene bridge. In the phosphonium cations the LUMOs have additional contributions from the phosphonium unit. 相似文献
156.
Kirk Haller Audrey Lee-St.John Meera Sitharam Ileana Streinu Neil White 《Computational Geometry》2012,45(8):385-405
Motivated by constraint-based CAD software, we develop the foundation for the rigidity theory of a very general model: the body-and-cad structure, composed of rigid bodies in 3D constrained by pairwise coincidence, angular and distance constraints. We identify 21 relevant geometric constraints and develop the corresponding infinitesimal rigidity theory for these structures. The classical body-and-bar rigidity model can be viewed as a body-and-cad structure that uses only one constraint from this new class.As a consequence, we identify a new, necessary, but not sufficient, counting condition for minimal rigidity of body-and-cad structures: nested sparsity. This is a slight generalization of the well-known sparsity condition of Maxwell. 相似文献
157.
Audrey Malagon 《Journal of Pure and Applied Algebra》2012,216(10):2213-2224
This paper presents a method for computing the Killing form of an isotropic Lie algebra defined over an arbitrary field based on the Killing form of a subalgebra containing its anisotropic kernel. This approach allows for streamlined formulas for many Lie algebras of types and and yields a unified formula for all Lie algebras of inner type , including the anisotropic ones. 相似文献
158.
Charlier N Neyrinck AM Beghein N Delzenne NM Gallez B 《Magnetic resonance imaging》2009,27(4):565-569
The aim of the present study was to evaluate the usefulness of electron paramagnetic resonance (EPR) spectroscopy and imaging in assessing the phagocytic activity of the liver after administration of India ink. We conducted experiments on livers from control rodents and from rodents in which the Kupffer cell population had been depleted by pretreatment with gadolinium chloride. The EPR signal intensity recorded in liver homogenates was about two times lower in GdCl(3) treated rats than in control rats. EPR imaging carried out on precision-cut liver slices indicated a good correlation between the depletion of Kupffer cells and the EPR signal intensity. 相似文献
159.
Wyatt Cole Stephanie L. Hemmingson Audrey C. Eisenberg Catherine A. Ulman Joseph M. Tanski Yutan D. Y. L. Getzler 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(1):65-69
Four 2,2′‐bisindolylmethanes (BIMs), a useful class of polyindolyl species joined to a central carbon, were synthesized using salicylaldehyde derivatives and simple acid catalysis; these are 2‐[bis(3‐methyl‐1H‐indol‐2‐yl)methyl]‐6‐methylphenol, (IIa), 2‐[bis(3‐methyl‐1H‐indol‐2‐yl)methyl]‐4,6‐dichlorophenol, (IIb), 2‐[bis(3‐methyl‐1H‐indol‐2‐yl)methyl]‐4‐nitrophenol, (IIc), and 2‐[bis(3‐methyl‐1H‐indol‐2‐yl)methyl]‐4,6‐di‐tert‐butylphenol, (IId). BIMs (IIa) and (IIb) were characterized crystallographically as the dimethyl sulfoxide (DMSO) disolvates, i.e. C26H24N2O·2C2H6OS and C25H20Cl2N2O·2C2H6OS, respectively. Both form strikingly similar one‐dimensional hydrogen‐bonding chain motifs with the DMSO solvent molecules. BIM (IIa) packs into double layers of chains whose orientations alternate every double layer, while (IIb) forms more simply packed chains along the a axis. BIM (IIa) has a remarkably long c axis. 相似文献
160.