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991.
992.
Most biopolymers exist in a plasticized state, whether it is naturally with water or unnaturally with glycerol or other suitable polyol, to make a flexible material. We have found that the extent to which a biopolymer can be plasticized is dependent on its molecular and higher order structures outside of simply molecular weight. Lactalbumin, ovalbumin, corn zein, wheat gluten, and feather keratin were plasticized with glycerol from very low to very high amounts. The conformation of the proteins was monitored with Fourier transform-infrared (FT-IR) spectroscopy and X-ray powder diffraction (XRD) and correlated with the tensile modulus. Protein conformational changes were pronounced for polar proteins with a low amount of cysteine. FT-IR showed that the conformational changes resulted in ordering of the protein at low to moderate plasticization levels. For proteins with little resistance to conformational changes, additional small-scale ordering occurred around the glass transition, as observed in XRD. Accurate comparison of plasticized proteins was dependent on knowing whether or not the protein was glassy or rubbery at room temperature as no differences arose in the glassy state. The transition from glassy to rubbery behavior with plasticization level can be found from modulus, FT-IR, and XRD data. 相似文献
993.
994.
Shaabani A Soleimani E Sarvary A Rezayan AH 《Bioorganic & medicinal chemistry letters》2008,18(14):3968-3970
A three-component reaction of an isocyanide, a dialkyl acetylenedicarboxylate, and tetronic acid in dichloromethane at room temperature afforded 4H-furo[3,4-b]pyran derivatives. These compounds are closely related with ring systems, TAN-2483B, TAN-2483A, and FD-211 which have a broad spectrum of biological activity. 相似文献
995.
Massah AR Adibi H Khodarahmi R Abiri R Majnooni MB Shahidi S Asadi B Mehrabi M Zolfigol MA 《Bioorganic & medicinal chemistry》2008,16(10):5465-5472
Silica sulfuric acid catalyzes efficiently the reaction of sulfonamides with both carboxylic acid anhydrides and chlorides under solvent-free and heterogeneous conditions. All the reactions were done at room temperature and the N-acylsulfonamides were obtained with high yields and purity via an easy work-up procedure. This method is attractive and is in a close agreement with green chemistry. These compounds were also investigated for antibacterial activity, including Gram-positive cocci and Gram-negative bacilli, and carbonic anhydrase II inhibitory activity. 相似文献
996.
Venigalla Purnachandra Rao Ernst Hegner Syed Wajih Ahmad Naqvi Pratima Mohan Kessarkar Syed Masood Ahmad Datta Suryanarayana Raju 《Palaeogeography, Palaeoclimatology, Palaeoecology》2008,260(3-4):347-358
Phosphorites from the Murray Ridge, NW Arabian Sea comprise nodules, bioclasts, and bone fragments. The nodules are made up of a homogeneous, light-colored phosphate nucleus consisting of Rivulariacean filamentous cyanobacteria and a thin dark-grey colored phosphate cortex showing abundant microbial filaments and microborings. The bioclasts comprise of 14–14.5 Ma old planktonic foraminifers, accepted as the time of deposition. Spherical to ovoid-shaped apatite microparticles resembling fossil bacteria are distinct components in the bioclasts. Bone fragments exhibit apatite fillings. The nodules and bone fragments consist entirely of carbonate fluorapatite (CFA) with low Al, K, and Th concentrations suggesting absence of continental detritus. Shale-normalized REE patterns of the samples support a seawater-derived composition. The highly uniform initial Nd values of − 4.8 to − 5.1 are interpreted as the seawater value at the onset of phosphatization 14 Ma ago. In contrast, 87Sr/86Sr ratios show a large range of 0.709055 to 0.709124 corresponding to unusually young stratigraphic ages of 1 to 3 Ma. The data are interpreted as evidence for post-depositional Sr exchange of the recrystallizing phosphorites with fluids isotopically not much different from modern seawater. It is concluded that the phosphorites formed under oxic, shallow-water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of CFA during early diagenesis at the sediment–water interface on different substrates. 相似文献
997.
Jalil Badraghi Ali Akbar Moosavi-Movahedi Ali Akbar Saboury Reza Yousefi Ahmad Sharifzadeh Jun Hong Thomas Haertlé Amir Niasari-Naslaji Nader Sheibani 《International journal of biological macromolecules》2009,45(5):511-517
Sodium dodecyl sulfate (SDS) at low concentrations considerably enhanced insulin aggregation and reduced the chaperone-like activity of purified camel αS1-casein (αS1-CN). These observed changes were the result of repulsive electrostatic interactions between both negative charged head groups of SDS and αS1-CN, and the net negative charge of insulin molecules, resulting in the greater exposure of hydrophobic patches of insulin and its enhanced aggregation. In contrast, enhanced hydrophobic interactions were primarily responsible for the conformational changes observed in insulin and αS1-CN at high SDS concentrations, resulting in increased binding of SDS and αS1-CN to insulin and its reduced aggregation. 相似文献
998.
Khalid Mahmood Zia Mehdi Barikani Ijaz Ahmad Bhatti Mohammad Zuber Mohammad Barmar 《Carbohydrate polymers》2009,77(1):54-58
Chitin based polyurethane (PU) elastomers constituted on 4,4´-diphenylmethane diisocyanate (MDI), poly(ε-caprolactone) (PCL) and extended with blends of chitin/1,4-butane diol were synthesized via two step polymerization technique. The synthesized samples were irradiated for 50, 100 and 200 h in an UV exposure chamber as such the spectral distribution of the light is good match for terrestrial solar radiation. The crystalline behavior of the irradiated PU samples were investigated by X-ray diffraction (XRD), differential scanning calorimetery (DSC) and dynamic mechanical thermal analysis (DMTA) techniques. The effect of irradiation time and chitin contents on crystallinity were studied and investigated. The maximum decrease in the crystalline behavior of samples after irradiation observed by XRD, DSC and tan δ peaks were found for the PU samples extended with lower contents of chitin (chitin/BDO; 0/100). In comparison with irradiation times the 200 h irradiation showed maximum change in the crystalline behavior. 相似文献
999.
Moradi Ahmad B. Conesa Héctor M. Robinson Brett Lehmann Eberhard Kuehne Guido Kaestner Anders Oswald Sascha Schulin Rainer 《Plant and Soil》2009,320(1-2):243-254
Chronic atmospheric nitrogen deposition affects the cycling of carbon (C) and nitrogen (N) in forest ecosystems, and thereby alters the stable C isotopic abundance of plant and soil. Three successional stages, disturbed, rehabilitated and mature forests were studied for their responses to different nitrogen input levels. N-addition manipulative experiments were conducted at low, medium and high N levels. To study the responses of C cycling to N addition, the C concentration and 13C natural abundances for leaf, litter and soil were measured. Labile organic carbon fractions in mineral soils were measured to quantify the dynamics of soil organic C (SOC). Results showed that three-year continuous N addition did not significantly increase foliar C and N concentration, but decreased C/N ratio and enriched 13C in N-rich forests. In addition, N addition significantly decreased microbial biomass C, and increased water soluble organic C in surface soils of N-rich forests. This study suggests that N addition enhances the water consumption per unit C assimilation of dominant plant species, restricts SOC turnover in N-poor forests at early and medium successional stages (thus favored SOC sequestration), and vice versa for N-rich mature forests. 相似文献
1000.
Ginny D. Ho John Anthes Ana Bercovici John P. Caldwell Kuo-Chi Cheng Xiaoming Cui Ahmad Fawzi Xiomara Fernandez William J. Greenlee John Hey Walter Korfmacher Sherry X. Lu Robbie L. McLeod Fay Ng April Smith Torhan Zheng Tan Deen Tulshian Geoffrey B. Varty Xiaoying Xu Hongtao Zhang 《Bioorganic & medicinal chemistry letters》2009,19(9):2519-2523
The discovery of 1 as a high-affinity ligand for the nociceptin receptor has led to the synthesis of a series of tropane (8-methyl-8-azabicyclo[3.2.1]octane) derivatives as optimized ligands. These compounds exhibit high affinity for the nociceptin receptor, moderate to excellent selectivity over the opioid μ receptor, and behave as full agonists. In this Letter, we present the synthesis and highlight the structure–activity relationship of tropane derivatives culminating in the identification of 24 and 32 as potent and orally active antitussive and anxiolytic agents. The in vitro and in vivo activities, pharmacokinetic profile, and the hPXR activity, which predicts the potential 3A4 induction in human, are disclosed. 相似文献