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141.
FeO4^2—与ClO^—共存体系的氧化还原滴定分析法 总被引:1,自引:0,他引:1
在重铬酸钾容量法测Fe^2+和硫酸亚铁铵容量法测Cr(Ⅳ)的基础上,提出FeO4^2-与ClO^-共存体系的氧化还原滴定分析法。该方法实用、可靠、对样品分析,结果令人满意。 相似文献
142.
Combustion catalysts La0.8Sr0.2MnO3 supported on γ-Al2O3, α-Al2O3, cordierite (2MgO•2Al2O3•5SiO2) and ZrO2 were compared. Further investigation was focused on LSM/ γ-Al2O3 catalyst. It was observed that LSM/γ-Al2O3 catalyst loaded with 20% (mass fraction) LSM (La0.8Sr0.2MnO3 or corresponding oxides), heated at 750℃ or above, perovskite-type oxides were found by XRD examination, whereas, the same catalyst loaded with 10% or less LSM, perovskite oxides were absent, calcination temperature about 750℃ is necessary for the formation of perovskite structure in LSM/γ-Al2O3 catalysts. High activity of complete oxidation of xylen will be obtained when perovskite-type oxides.
Investigation of TPR showed that neat LSM or LSM/γ-Al2O3(20%) was reduced by H2-N2 mixed gas. Two degradation processes took place. In the first, reduced temperature peak was about 350 - 450℃. If reduction ended at 400℃, perovskite structure was retained, which may be due to the reduction of Mn3+to Mn2+ on the surface of LSM only. In the second process, perovskite structure was destroied, and La2O3, Mn2O3, Mn - Sr - O oxides could be obtained, which took place in the temperature range 685 - 750℃ and ended at 800℃. This was proved by TPR experiments (Fig. 3, 5) and XRD patterns (Fig. 4)
Catalysts LSM/γ-Al2O3(10% or 20%) heated at 500℃ have only one TPR peak, i. e. lower temperature peak. This is due to the absence of perovskite-type oxides in the catalysts. However, neat LSM or LSM/γ-Al2O3(20%) heated 750℃ or above, not only the first low temperature TPR peak but also the second peak, which is contributed by the perovskite-type oxides in these catalysts appeared. Therefore, the second TPR peak, i. e. the higher temperatue peak is a characteristic peak for perovskite-type oxides in the reduced process. When LSM/ γ-Al2O3 (10%) catalys is heated at 750℃, no perovskite-type oxides were detected by XRD, and the second reduction peak was absent also in TPR process. \
The order of the second reduction peak temperature(characteristic peak of perovskite - type ox- ides) is: neat LSM(750℃)> LSM/γ-Al2O3 20% (685-698℃) -deposited LSM/γ-Al2O3 (698℃) > LSM/γ-Al2O3 15% (677 - 680℃) >(LSM/γ-AL2O3 10% 620 - 630℃, for Mn - Al - O medium oxides on surface). It is correleted with the increasing of the effect of support sequentially.
When LSM/γ-Al2O3 catalysts were heated at 900℃, more stable phase, spinel MnAl2O4 appeared, which could be proved by TPR of model catalyst MnAl2O4/γ-Al2O3. 相似文献
Investigation of TPR showed that neat LSM or LSM/γ-Al2O3(20%) was reduced by H2-N2 mixed gas. Two degradation processes took place. In the first, reduced temperature peak was about 350 - 450℃. If reduction ended at 400℃, perovskite structure was retained, which may be due to the reduction of Mn3+to Mn2+ on the surface of LSM only. In the second process, perovskite structure was destroied, and La2O3, Mn2O3, Mn - Sr - O oxides could be obtained, which took place in the temperature range 685 - 750℃ and ended at 800℃. This was proved by TPR experiments (Fig. 3, 5) and XRD patterns (Fig. 4)
Catalysts LSM/γ-Al2O3(10% or 20%) heated at 500℃ have only one TPR peak, i. e. lower temperature peak. This is due to the absence of perovskite-type oxides in the catalysts. However, neat LSM or LSM/γ-Al2O3(20%) heated 750℃ or above, not only the first low temperature TPR peak but also the second peak, which is contributed by the perovskite-type oxides in these catalysts appeared. Therefore, the second TPR peak, i. e. the higher temperatue peak is a characteristic peak for perovskite-type oxides in the reduced process. When LSM/ γ-Al2O3 (10%) catalys is heated at 750℃, no perovskite-type oxides were detected by XRD, and the second reduction peak was absent also in TPR process. \
The order of the second reduction peak temperature(characteristic peak of perovskite - type ox- ides) is: neat LSM(750℃)> LSM/γ-Al2O3 20% (685-698℃) -deposited LSM/γ-Al2O3 (698℃) > LSM/γ-Al2O3 15% (677 - 680℃) >(LSM/γ-AL2O3 10% 620 - 630℃, for Mn - Al - O medium oxides on surface). It is correleted with the increasing of the effect of support sequentially.
When LSM/γ-Al2O3 catalysts were heated at 900℃, more stable phase, spinel MnAl2O4 appeared, which could be proved by TPR of model catalyst MnAl2O4/γ-Al2O3. 相似文献
143.
Ge-Sb-Se硫系玻璃被认为是极佳的红外传输材料和有潜力的非线性光学材料.在光学设计中,玻璃的线性折射率(n)及其热光系数(ζ)是关键技术参数.以预测和调控Ge-Sb-Se玻璃的n和ζ为目的,考察了玻璃的n,ζ,密度(d)和体积膨胀系数(β)与化学参数dSe和拓扑网络结构参数r的内在联系.研究发现,玻璃的n随d的增加而增大;ζ随β的增大而近似线性减小;β随dSe的减小或r的增大而减小;当Ge含量固定时, d随dSe的减小或r的增大而增大,当Sb含量固定时, d在dSe=0时具有最小值.基于实测d和n,拟合获得了Ge, Sb和Se元素在2—12μm波段的摩尔折射度(R_i),分别为R_(Ge)=10.16—10.50 cm~3/mol,RSb=16.71—17.08 cm~3/mol和RSe=11.15—11.21 cm~3/mol,根据d和R_i计算得到的n与实测值的偏差小于1%.基于实测ζ和β,拟合得到了Ge, Sb和Se元素在2—12μm波段的摩尔折射度温度系数(φ_i),分别为φ_(Ge)=21.1—22.6 ppm/K,φ_(Sb)=7.2—8.4 ppm/K和φ_(Se)=90.2—94.2 ppm/K,根据β和φ_i计算得到的ζ与实测值的偏差小于6 ppm/K. 相似文献
144.
本文研究修正的相场晶体(MPFC)方程的二阶无条件能量稳定数值格式.首先,利用标量辅助变量(SAV)法和二阶向后欧拉(BDF2)公式,得到了一个数值格式;其次,给出了能量耗散定律,严格证明了该数值格式是质量守恒的,唯一可解的,无条件能量稳定的;最后,通过数值实例验证了格式的精度和稳定性. 相似文献
145.
基于非分散红外(NDIR)技术的土壤剖面二氧化碳浓度的测定 总被引:1,自引:0,他引:1
为了探索土壤剖面CO2浓度以及不同土壤层(腐殖质H层、A层、B层、C层)土壤呼吸的变化规律,应用非分散红外(NDIR)技术的新方法,持续不间断的测量土壤剖面二氧化碳浓度。实验所用的主要仪器为硅基非分散红外测量仪,能在高湿、高粉尘、污垢及其他恶劣环境中进行光谱数据采集。通过2013年全年光谱测定值的采集,并应用梯度法模型计算不同深度土壤碳通量,同时利用LI-8100碳通量自动监测系统持续监测的土壤碳通量值进行回归分析。结果显示:土壤剖面CO2浓度呈现明显的梯度变化,即随着土壤深度的增加,土壤CO2浓度增大;梯度法模型得出的不同土壤层的土壤呼吸模拟值与实测土壤呼吸值之间具有较好的线性相关,H,A,B,C层的模型预测的决定系数(R2)分别为0.906 9,0.718 5,0.838 2,0.903 0,均方根误差(RMSE)分别为0.206 7,0.104 1,0.015 6,0.009 6。均达到了较好的预测结果,表明该方法对定量分析不同土壤层碳通量是可行的。该方法具有清晰揭示土壤CO2在不同土壤层之间的传输规律,以及有助于分析不同土壤层土壤呼吸特性的优点,能为全球土壤剖面碳通量计算提供基础数据,是一种具有发展前途的传感器。 相似文献
146.
为研究NH4F含量及煅烧工艺对氧化铝相变及α-Al2O3微观形貌的影响,向Al(OH)3粉体中引入不同质量分数的NH4F,经不同条件煅烧后获得Al2 O3粉体样品.采用X射线衍射仪和扫描电子显微镜进行物相分析和晶相形貌观察.结果表明,NH4F的引入可以显著降低Al2 O3的相变温度,含量5.0; NH4F的Al(OH)3在900℃保温2.5h全部转变为α-Al2O3,这比传统的转变温度低200~ 250℃.同时,随着NH4F含量的增加,α-Al2O3晶粒形貌由颗粒状变为平面六角片状.但是平面六角片状α-Al2 O3在1200℃是不稳定的,长时间煅烧时,α-Al2O3晶体又"熔解"为小颗粒晶粒. 相似文献
147.
研究了对偶超导模型的大n涡旋。 基于变分原理得出了Abelian Higgs模型在n=90—110的近似涡旋解析解, 并计算了涡旋张力对n的依赖性。 发现, 每根涡旋的张力大致随n线性增长。 期望该解对理解Abelian Higgs模型中的大量子数涡旋的墙行为具有一定价值。 The large n vortices in the dual superconductor model was investigated. An approximate analytical solution was obtained for n fold quantized vortices with n=90—110 by variationally solving the AbelianHiggs model, and the vortex tension was calculated as a function of n. It was found that the vortex tension rises linearly as n grows. It is hoped that our solution shines light on the understanding of the wall behavior of the large n vortices in Abelian Higgs model. 相似文献
148.
149.
150.
阻抑动力学同步荧光法测定环境水样中苯胺 总被引:3,自引:0,他引:3
在稀硫酸介质和CTMAB存在下 ,痕量苯胺对溴酸钾氧化荧光素的反应具有灵敏的阻抑作用 ,荧光素的氧化产物有强荧光 ,但其激发光谱和发射光谱严重重叠 ,文章采用同步荧光光谱法减小了谱带重叠 ,获得了很好的灵敏度和选择性 ,据此建立了阻抑动力学同步荧光法测定苯胺的新方法。方法的线性范围是 0~10 μg·L- 1 ,检测限为 0 3μg·L- 1 。用于环境水样和实验室废水中苯胺含量的测定 ,结果满意 相似文献