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991.
Distinct Role of Sesn2 in Response to UVB‐Induced DNA Damage and UVA‐Induced Oxidative Stress in Melanocytes
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Baozhong Zhao Palak Shah Lei Qiang Tong‐Chuan He Andrey Budanov Yu‐Ying He 《Photochemistry and photobiology》2017,93(1):375-381
Ultraviolet (UV) radiation, including both UVB and UVA irradiation, is the major risk factor for causing skin cancer including melanoma. Recently, we have shown that Sesn2, a member of the evolutionarily conserved stress‐inducible protein family Sestrins (Sesn), is upregulated in human melanomas as compared to melanocytes in normal human skin, suggesting an oncogenic role of Sesn2. However, the role of Sesn2 in UVB and UVA response is unknown. Here, we demonstrated that both UVB and UVA induce Sesn2 upregulation in melanocytes and melanoma cells. UVB induces Sesn2 expression through the p53 and AKT3 pathways. Sesn2 negatively regulates UVB‐induced DNA damage repair. In comparison, UVA induces Sesn2 upregulation through mitochondria but not Nrf2. Sesn2 ablation increased UVA‐induced Nrf2 induction and inhibits UVA‐induced ROS production, indicating that Sesn2 acts as an upstream regulator of Nrf2. These findings suggest previously unrecognized mechanisms in melanocyte response to UVB and UVA irradiation and potentially in melanoma formation. 相似文献
992.
Online background cleanup followed by high‐performance liquid chromatography with tandem mass spectrometry for the analysis of perfluorinated compounds in human blood
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Liangpo Liu Jianwen She Jie Zhang Meiping Tian Qingyu Huang Syed Ali Musstjab Akber Shah Eqani Heqing Shen 《Journal of separation science》2015,38(2):247-253
In this study, a novel method for the analysis of perfluorinated compounds in whole blood has been developed and validated. The method was developed by using a conventional reversed‐phase C18 column as a trapping column for the elimination of background contamination and high‐performance liquid chromatography with tandem mass spectrometry for the target compounds analysis. The trapping column provided fast online separation of the background contamination of perfluorinated compounds. In this developed method, the limits of detection for different perfluorinated compounds ranged from 0.06 to 0.14 ng/mL. It is notable that the limit of detection (0.07 ng/mL) for perfluorooctanoic acid was improved significantly after the elimination of background contamination. The method was also validated in terms of sensitivity, accuracy, and precision. The recoveries ranged from 66.8 to 111.9%, with relative standard deviations from 2.1 to 15.3%. Our preliminary data suggest that the novel method based on trapping column cleanup followed by high‐performance liquid chromatography with tandem mass spectrometry could be applied in studies on the human exposure to perfluorinated compounds. 相似文献
993.
Jens Heber Gerhard Knieper Hemangi M. Shah 《Proceedings of the American Mathematical Society》2007,135(3):845-849
Let be a Hadamard manifold of dimension whose sectional curvature satisfies and whose curvature tensor satisfies for suitable constants and . We show that is of constant sectional curvature provided is asymptotically harmonic. This was previously only known if admits a compact quotient.
994.
Montenegro EC Shah MB Luna H Scully SW de Barros AL Wyer JA Lecointre J 《Physical review letters》2007,99(21):213201
Time-of-flight mass spectrometry was used to investigate fragmentation and energy transfer processes in water by C ions at the distal part of the Bragg peak. Measurements of the positive ion fragments from ionization, electron capture, electron loss, transfer-loss and loss-ionization channels have allowed us for the first time (a) to obtain a quantitative determination of the energy lost by C ions in water and (b) to show that total water fragment ion production has a much flatter profile with projectile energy than would be expected if the water radical formation was assumed to follow the energy-loss profile obtained from available stopping power models. 相似文献
995.
A comparative study of suitably functionalized, highly soluble tetraceno[2,3-b]thiophenes (1-3) and pentacenes (4-6) that show higher photoxidative stability than that of unfunctionalized corresponding acenes is reported. The absorption and emission of 1-3 (Amax = 624-656 nm, lambda max = 634-672 nm, PhiF approximately 10%) and 4-6 (Amax = 672-704 nm, lambda max = 682-718 nm, PhiF approximately 10%) were found to be systematically red-shifted by the substitution in the order of the tert-butylethynyl < triisopropylsilylethynyl < phenylethynyl groups. The oxidation potentials of these compounds were similar (E1/2 approximately 0.70 V), except for 4, which showed lower oxidation potential (E1/2 approximately 0.63 V). 相似文献
996.
Proton-detected solid-state NMR spectroscopy of fully protonated proteins at 40 kHz magic-angle spinning 总被引:3,自引:0,他引:3
Zhou DH Shah G Cormos M Mullen C Sandoz D Rienstra CM 《Journal of the American Chemical Society》2007,129(38):11791-11801
Remarkable progress in solid-state NMR has enabled complete structure determination of uniformly labeled proteins in the size range of 5-10 kDa. Expanding these applications to larger or mass-limited systems requires further improvements in spectral sensitivity, for which inverse detection of 13C and 15N signals with 1H is one promising approach. Proton detection has previously been demonstrated to offer sensitivity benefits in the limit of sparse protonation or with approximately 30 kHz magic-angle spinning (MAS). Here we focus on experimental schemes for proteins with approximately 100% protonation. Full protonation simplifies sample preparation and permits more complete chemical shift information to be obtained from a single sample. We demonstrate experimental schemes using the fully protonated, uniformly 13C,15N-labeled protein GB1 at 40 kHz MAS rate with 1.6-mm rotors. At 500 MHz proton frequency, 1-ppm proton line widths were observed (500 +/- 150 Hz), and the sensitivity was enhanced by 3 and 4 times, respectively, versus direct 13C and 15N detection. The enhanced sensitivity enabled a family of 3D experiments for spectral assignment to be performed in a time-efficient manner with less than a micromole of protein. CANH, CONH, and NCAH 3D spectra provided sufficient resolution and sensitivity to make full backbone and partial side-chain proton assignments. At 750 MHz proton frequency and 40 kHz MAS rate, proton line widths improve further in an absolute sense (360 +/- 115 Hz). Sensitivity and resolution increase in a better than linear manner with increasing magnetic field, resulting in 14 times greater sensitivity for 1H detection relative to that of 15N detection. 相似文献
997.
Shah AR Oehmen CS Harper J Webb-Robertson BJ 《Computational Biology and Chemistry》2007,31(2):138-142
A significant challenge in homology detection is to identify sequences that share a common evolutionary ancestor, despite significant primary sequence divergence. Remote homologs will often have less than 30% sequence identity, yet still retain common structural and functional properties. We demonstrate a novel method for identifying remote homologs using a support vector machine (SVM) classifier trained by fusing sequence similarity scores and subcellular location prediction. SVMs have been shown to perform well in a variety of applications where binary classification of data is the goal. At the same time, data fusion methods have been shown to be highly effective in enhancing discriminative power of data. Combining these two approaches in the application SVM-SimLoc resulted in identification of significantly more remote homologs (p-value<0.006) than using either sequence similarity or subcellular location independently. 相似文献
998.
Coulometric titration, an electrochemical method for measuring oxidation isotherms, has been used to characterize the redox properties of V2O5 and Mg3(VO4)2 between 823 and 973 K. V2O5 shows distinct regions in the isotherms corresponding to equilibrium with mixtures of V2O3 and V2O4 and of V2O4 and V2O5. From this data, the enthalpies for oxidation of V2O3 to V2O4 and for V2O4 to V2O5 are shown to be -380 +/- 10 and -285 +/- 20 kJ mol-1 O2, respectively. Oxidation isotherms for Mg3(VO4)2 exhibit a single step between the oxidized sample (all V+5) and a completely reduced sample (all V+3). The enthalpy of oxidation is found to increase with the oxidation state of the sample, from -370 +/- 30 kJ mol-1 O2 at an O:V ratio of 1.5 to -460 +/- 10 kJ mol-1 O2 at an O:V ratio of 2.5. 相似文献
999.
Here, we report a new class of highly chemoselective reactions between squarate derivatives and the amino acid cysteine or unprotected peptides with a N-terminus cysteine that proceed most efficiently in entirely aqueous solution at neutral pH. Kinetic and structural studies reveal that the presence of hydrogen bonding in water is primarily responsible for both the high yield and fast rate of the reaction. 相似文献
1000.
We propose an accurate method to predict interfacial tension between water and nonpolar fluids by using Cahn gradient theory. The only necessary elements are (i) a water contact energy function and (ii) an equation of state (EoS) for the nonpolar fluid, chosen here as the Peng-Robinson EoS. The contact energy, a function of the fluid (adsorbate) surface density, is related to interfacial tension (IFT) by means of the Gibbs adsorption equation. Examining a large number of IFT data, we observe that the water contact energy is a universal function of adsorbate's surface density when proper scaling variables are used: it depends neither on adsorbate nor on temperature. A corresponding-states principle appears to govern the interfacial behavior between water and any nonpolar compound that is sparingly soluble in water. A predictive method (without any adjustable parameter) is therefore available for estimating IFT between water and any nonpolar fluid, whether the fluid is in supercritical or in subcritical states. The method performs well when the adsorbate is sparingly soluble in water, but slightly overestimates IFTs when the adsorbate's solubility in water is significant (e.g., CO2 and H2S). A similar behavior should also hold for interfaces involving a solid substrate. 相似文献