全文获取类型
收费全文 | 245篇 |
免费 | 13篇 |
国内免费 | 36篇 |
专业分类
化学 | 175篇 |
力学 | 58篇 |
综合类 | 5篇 |
数学 | 10篇 |
物理学 | 46篇 |
出版年
2023年 | 3篇 |
2022年 | 21篇 |
2021年 | 14篇 |
2020年 | 19篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 12篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 15篇 |
2012年 | 9篇 |
2011年 | 15篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 6篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有294条查询结果,搜索用时 15 毫秒
81.
82.
《Journal of separation science》2018,41(5):1149-1155
Basalt fibers were functionalized with gold nanoparticles and characterized by scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. An in‐tube solid‐phase microextraction device was developed by packing the functionalized basalt fibers in a polyether ether ketone tube. The device was connected into high performance liquid chromatography equipment with a diode array detector to build online enrichment and analysis system. Eight polycyclic aromatic hydrocarbons were used as model analytes, important factors including sampling rate, sampling volume, organic solvent content in sample, and desorption time were investigated. Linear range (0.01–20 μg/L), detection limits (0.003–0.015 μg/L), and enrichment factors (130–1628) were given by the online analysis method. Relative standard deviations (n = 5) of extraction repeatability on one tube and tube‐to‐tube repeatability were less than 5.2 and 14.7%, respectively. The analysis method was applied to detect polycyclic aromatic hydrocarbons in environmental water samples, and relative recoveries ranged from 87 to 128%. 相似文献
83.
84.
采用高碘酸钠对棉织物表面进行选择性氧化生成醛基,选取乙二胺与醛基反应,通过膦氢化加成反应将阻燃剂亚磷酸二甲酯接枝到棉织物表面,最后通过三羟甲基三聚氰胺对棉织物表面进行接枝改性,制备了含三羟甲基三聚氰胺/乙二胺/亚磷酸二甲酯阻燃棉织物.通过傅里叶红外光谱(FTIR)对改性后棉织物的结构进行了表征,通过极限氧指数(LOI)测试研究了其阻燃性能,通过锥形量热测试研究了其燃烧行为,通过在40℃皂水中洗涤10次考察了其耐水性能,通过扫描电子显微镜测试了其表面及燃烧后炭层的形貌.研究结果表明,经表面改性后,棉织物的LOI值由(19.5±1.0)%提高到了(43.1±1.0)%,经耐水洗测试后,LOI值仅下降至(42.6±1.0)%,保持了非常好的阻燃性能,表明通过表面接枝方法制备的三羟甲基三聚氰胺/乙二胺/亚磷酸二甲酯阻燃棉织物具有非常好的耐水洗性能.表面阻燃改性提高了棉织物在燃烧过程中的成炭性能,形成的连续膨胀的炭层较好地保护了内部织物,抑制了织物的降解和燃烧,从而提高了棉织物的阻燃性能. 相似文献
85.
Suction Induced Effects on the Fabric of a Structured Soil 总被引:3,自引:0,他引:3
Azad Koliji Lyesse Laloui Olivier Cusinier Laurent Vulliet 《Transport in Porous Media》2006,64(2):261-278
This paper presents the mathematical modelling of the modification of the pore space geometry of a structured soil subjected
to suction increase. Structured soil concepts are first introduced considering different fabric units, such as aggregates
and fissures. The numerical modelling of the structural evolution is based on experimental test results in which the evolution
of the structure of the samples subjected to different suctions is determined using the mercury intrusion porosimetry technique.
From this information, the macro and micropore volume evolutions are determined. The results show that drying produces a reduction
in the soil total porosity which mainly corresponds to a reduction of the macropore volume. Associated with this phenomenon,
an increase in micropore volume is also observed. The proposed model divides pore size distribution into three pore classes
(micropores, macropores and non-affected areas). Using the concept of a suction-influenced domain, the proposed model is able
to reproduce the main observed fabric evolution between the saturated and dry states. 相似文献
86.
Jihyun Park Lee Ku Kwac Hong Gun Kim Kil-Young Park Ki Woo Koo Dong-Hwa Ryu Hye Kyoung Shin 《Molecules (Basel, Switzerland)》2022,27(17)
Lyocell is a biodegradable filament yarn obtained by directly dissolving cellulose in a mixture of N-methylmorpholine-N-oxide and a non-toxic solvent. Therefore, herein, lyocell fabrics were employed as eco-friendly carbon-precursor substitutes for use as electromagnetic interference (EMI) shielding materials. First, a lyocell fabric treated with polyacrylamide via electron beam irradiation reported in a previous study to increase carbon yields and tensile strengths was carbonized by heating to 900, 1100, and 1300 °C. The carbonization transformed the fabric into a graphitic crystalline structure, and its electrical conductivity and EMI shielding effectiveness (SE) were enhanced despite the absence of metals. For a single sheet, the electrical conductivities of the lyocell-based carbon fabric samples at the different carbonization temperatures were 3.57, 5.96, and 8.91 S m−1, leading to an EMI SE of approximately 18, 35, and 82 dB at 1.5–3.0 GHz, respectively. For three sheets of fabric carbonized at 1300 °C, the electrical conductivity was 10.80 S m−1, resulting in an excellent EMI SE of approximately 105 dB. Generally, EM radiation is reduced by 99.9999% in instances when the EMI SE was over 60 dB. The EMI SE of the three lyocell-based carbon fabric sheets obtained at 1100 °C and that of all the sheets of the sample obtained at 1300 °C exceeded approximately 60 dB. 相似文献
87.
Monyratanak Lim Sudtida Pliankarom Thanasupsin Nisakorn Thongkon 《Molecules (Basel, Switzerland)》2022,27(21)
Molecularly imprinted polymers@ethylenediamine-modified carbon dots grafted on cotton fabrics (MIPs@EDA-CDs/CF) and smartphone-based fluorescence image analysis were proposed and used for the first time for the detection of 17 α-methyltestosterone (MT). The EDA-CDs were synthesized and grafted on cotton fabric before coating with the MIPs. The MIPs were synthesized using the MT as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and azobisisobutyronitrile (AIBN) as an initiator. The MIPs@EDA-CDs/CF were characterized using FTIR, SEM-EDS, and RGB fluorescence imaging. The fluorescence images were also taken using a smartphone and the ImageJ program was used for RGB measurement. The Δ red intensity was linearly proportional to MT concentration in the range of 100 to 1000 μg/L (R2 = 0.999) with a detection limit of 44.4 μg/L and quantification limit of 134 μg/L. The MIPs@EDA-CDs/CF could be stored at 4 °C for a few weeks and could be reused twice. The proposed method could apply for the specific determination of MT in water and sediment samples along with satisfactory recoveries of 96–104% and an acceptable relative standard deviation of 1–6% at the ppb level. 相似文献
88.
Matsumoto H Yako H Minagawa M Tanioka A 《Journal of colloid and interface science》2007,310(2):678-681
Cationic biopolymer nanofiber fabrics were prepared from a chitosan/poly(ethylene oxide) blend solution by electrospray deposition. Their electrokinetic properties and DNA adsorption behavior were analyzed as a function of pH. The zeta potential was determined from streaming potential/streaming current measurements. The adsorption of DNA onto the fabrics was investigated by spectrophotoscopy. The adsorption behavior of DNA correlated well with the electrokinetic properties of the fabrics. This revealed that the electrokinetic approach was a useful option for characterization of novel nanofiber assemblies made by the electrostatic spray process. In addition, these results provided fundamental information about chitosan nanofiber fabrics for both biomedical and analytical applications. 相似文献
89.
In this work, n-alkyl chitosan (N-CTS) was obtained by alkylation modification of chitosan with n-butylaldehyde using Schiff alkali method. The etherifying agent 3-chloro-2-hydroxypropyl triethylammonium chloride (CHPTAC-ethyl) was synthesized from triethylamine and epichlorohydrin. The N-CTS and CHPTAC-ethyl were etherized to finally synthesize n-alkyl quaternary ammonium chitosan (N-CCTS). Scanning electron microscope, X-ray diffractometer, Fourier transform infrared, X-ray photoelectron spectroscopy, and 13CNMR were used to characterize the surface morphology and chemical structure. Viscosity method and spectrophotometry were used to determine its physical and chemical properties. The etherification reaction mechanism was studied systematically and the influence of reaction conditions on the degree of substitution and solubility of N-CCTS was investigated. The minimum inhibitory concentration (MIC) of N-CCTS against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was both 0.15 g/L, which was superior to the MIC value of natural chitosan. N-CCTS was used to finish rabbit hair fabric with citric acid as cross-linking agent and sodium hypophosphite as catalyst. The antibacterial and washing resistance of the product were investigated. After 25 times of washing, the antibacterial rate of N-CCTS against E. coli and S. aureus remained stable at about 90%, and the antibacterial rate was higher than that of N-CTS and natural chitosan, and it was a kind of natural polymer long-acting antibacterial finishing agent for rabbit hair fabric. 相似文献
90.