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81.
在光子晶体光纤典型的空气孔三角形排布图案中,将每个空气孔替换为一对孪生空气孔对,孪生空气孔对之间有确定的间距和固定的轴向,并由其形成包层的基本单元.在端面中心位置缺失一孪生空气孔对,由高折射率的背景材料将光场束缚于此形成纤芯.在包层中所有的孪生空气孔对按照三角形规则均匀排列.在这种新型结构中,由于所有孪生空气孔对都具有相同轴向而使得两个正交方向上的折射率不对称,从而导致双折射效应.本文利用有限差分法进行数值计算,所设计孪生空气孔对光子晶体光纤在两个正交方向上的折射率差Δneff可达到10-4.孪生空气孔对结构参量可在一定程度上影响双折射效果,增大空气孔或减小孪生空气孔对内部间距都可在一定程度上增大双折射效应. 相似文献
82.
本文探讨经阴道彩色多普勒超声、人绒毛膜促性腺激素β(β-hCG)在早期异位妊娠诊断中的价值。选取异位妊娠患者78例作为观察组,根据超声影像特征,其中环状征型、混合包块型和典型孕囊型分别为15例、24例和39例;选取正常妊娠者140例作为对照组。两组均行经阴道彩色多普勒超声检查,采用电化学发光法检查血清β-hCG水平。结果显示,与对照组比较,观察组子宫内膜厚度和血清β-hCG水平降低(P<0.05);环状征型、典型孕囊型和混合包块型患者血清β-hCG水平比较差异有统计学意义(P<0.05);血清β-hCG水平联合子宫内膜厚度预测异位妊娠的ROC曲线下面积为0.901(P<0.05)。经阴道彩色多普勒超声联合β-hCG在异位妊娠诊断中有较好的效果,同时异位妊娠患者β-hCG水平与彩超影像特征有一定关系。 相似文献
83.
钟丽 《广东微量元素科学》2017,24(6):55-57
目的了解妊娠期糖尿病专业治疗中行个体化营养膳食疗法对其妊娠结局以及血糖控制水平产生的影响。方法选择130例因妊娠期糖尿病进入江西省萍乡市人民医院的患者,以膳食疗法的差异分组:62例Ⅰ组施以常规膳食疗法,68例Ⅱ组则施以个体化营养膳食疗法,再对两组病例血糖值及其妊娠结局专业统计、观察。结果施以两种膳食疗法后,62例Ⅰ组FPG值(5.60±0.90)mmol/L,68例Ⅱ组(4.47±0.49)mmol/L,(P<0.05);同时Ⅱ组2h PG值及其妊娠结局等都优于Ⅰ组,(P<0.05)。结论对于患有糖尿病的妊娠期患者,通过施以个体化营养膳食疗法,可实现对妊娠结局的充分改善,值得推荐应用。 相似文献
84.
85.
《Physics letters. A》2020,384(10):126206
Experimental studies have demonstrated that both strain rate and temperature influence the mechanical behavior of nanostructured metals significantly. In this work, a theoretical model is developed to describe the strain-rate-dependent constitutive behavior of nanotwinned polycrystalline metals. The athermal flow stress and thermal-activated flow stress are both considered in modeling the plastic deformation of a nanotwinned metal. Numerical results are consistent with the experimental results, showing that the present model can well describe the strain rate-dependent deformation behavior of nanotwinned polycrystalline copper. Henceforth, the constitutive behaviors of nanotwinned copper at different strain rates and temperatures can be predicted, which will be useful for optimizing the dynamic mechanical properties at various temperatures for nanotwinned metals. 相似文献
86.
《Physics letters. A》2020,384(1):126036
In lung cancer, primary diagnosis is quite essential to guarantee human health. In this work, the capability of γ-graphyne and twin-graphene sheets to detect typical breath gases such as benzene, styrene, aniline, and o-toluidine is studied based on density functional theory. The results indicate that these gases are physisorbed on γ-graphyne and twin-graphene. Because of relatively low gas binding strength between gases and γ-graphyne and twin-graphene, these sheets can be proper for the practical gas sensors with a fast recovery rate. Both γ-graphyne and twin-graphene have semiconducting properties before and after gas adsorption. Adsorption of the gases decreases the energy band gap, and increases the electric dipole moment of γ-graphyne and twin-graphene. The electronic properties of twin-graphene are more sensitive than that of γ-graphyne to the presence of the considered gases. Hence, twin-graphene can be desirable and promising material for sensing typical breath gases to diagnose lung cancer. 相似文献
87.
Vi Tran Bernd Walkenfort Matthias Knig Mohammad Salehi Sebastian Schlücker 《Angewandte Chemie (International ed. in English)》2019,58(2):442-446
The design of a portable Raman/SERS‐LFA reader with line illumination using a custom‐made fiber optic probe for rapid, quantitative, and ultrasensitive point‐of‐care testing (POCT) is presented. The pregnancy hormone human chorionic gonadotropin (hCG) is detectable in clinical samples within only 2–5 s down to approximately 1.6 mIU mL?1. This acquisition time is several orders of magnitude shorter than those of existing approaches requiring expensive Raman instrumentation, and the method is 15‐times more sensitive than a commercially available lateral flow assay (LFA) as the gold standard. The SERS‐LFA technology paves the way for affordable, quantitative, and ultrasensitive POCT with multiplexing potential in real‐world applications, ranging from clinical chemistry to food and environmental analysis as well as drug and biowarfare agent testing. 相似文献
88.
89.
为克服现有的透射电镜试样双喷电解减薄仪的缺点,自制了双喷电解减薄装置。该系列装置完令透明,安装有放大镜,可以完全看清电解液的双喷状况,观察试样表面侵蚀减薄的全过程,随时洲整,从而得到大而多的薄区;双喷部件由玻璃制成,耐腐蚀性好;冰水混合物作冷却剂,准备方便而且长时川温度恒定对制得的多种材料的试样经过透射电镜实验,效果良好。 相似文献
90.
《Journal of separation science》2017,40(12):2620-2628
In this work, a fast and effective dispersive liquid–liquid microextraction was developed for the isolation and preconcentration of free 17 β‐estradiol, the main human estrogen, from real human urine samples. To optimize the extraction technique, few important parameters such as type and volume of extraction and dispersive solvents, centrifugation conditions, effect of salt addition, and extraction time were studied. Optimal conditions were obtained when injecting 600 μL mixture of tetrachloromethane as extraction solvent and ethanol as dispersive solvent (1:5, v/v) into 2 mL of urine containing 8% NaCl and following centrifugation at 10 000 rpm, thus reaching enrichment factor 28 and extraction recovery 98% for estradiol. Procedure was evaluated by means of high‐performance liquid chromatography with UV detection (λ = 280 nm) using a C‐18 column and methanol/water (60:40, v/v) as the mobile phase. The method was linear within the concentration range 1.0–250.0 mg/L (r = 0.9997) and provided a limit of detection of 0.25 mg/L. The proposed method was applied to the determination of free estradiol in real human pregnancy urine. 相似文献