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991.
992.
采用甘氨酸-硝酸盐(GNP)法合成了新型中温固体氧化物燃料电池(IT-SOFC)的阴极材料Gd1-xSrxCoO3-δ(x=0~0.5)和Gd0.8Sr0.2Co1-yFeyO3-δ(y=0~1),所合成的初始粉体在800℃下煅烧12h后均形成了钙钛矿结构的单相固溶体。研究发现,Gd0.8Sr0.2CoO3-δ(GSC)的电导率在600℃时达到了559S·cm^-1,由Ce0.8Gd0.2O2-δ(GDC)电解质和GSC-25GDC材料组成的对称电极在600℃和700℃的界面阻抗分别为0.170Ω·cm^2和0.064Ω·cm^2,活化能仅为87.8kJ·mol^-1,预示其可以作为ITSOFC较为理想的阴极备选材料;随着Fe3+离子含量的增加,Gd0.8Sr0.2Co1-yFeyO3-δ系列阴极材料的热膨胀系数显著降低,但其电导率也急速下降;此外,通过调整Gd0.8Sr0.2CoO3-δ与GDC的比例可以制备出热膨胀系数与GDC电解质匹配、性能良好的Gd0.8Sr0.2CoO3-δ/GDC复合阴极材料。 相似文献
993.
994.
XUE Yan-feng XU Da-peng ZHANG Guang-qiang ZHOU Xian-feng DING Zhanhui LIU Xiao-mei SU Wen-hui 《高等学校化学研究》2008,24(2):135-137
ZrSiO4 and coesite were obtained under high-pressure and high-temperature from the nano precursor of a-SiO2 and ZrO2. XRD and Raman measurements indicate that ZrSiO4 was formed at a temperature higher than 920 ℃ under a pressure of 3.6 GPa. As the pressure increased to 3.9 GPa, the ZrSiO4 formation temperature was reduced to 815 ℃. The formation temperature for coesite was 990 ℃ under 3.9 GPa. The lower formation temperature for ZrSiO4, as compared to that for coesite, provided an experimental evidence that the coesite in the Earth's surface usually occurs as inclusions in ZrSiO4. 相似文献
995.
ZHUANG Quan-chao FAN Xiao-yong XU Jin-mei WEI Guo-zhen DONG Quan-feng SUN Shi-gang 《高等学校化学研究》2008,24(4):511-515
The formation process of solid electrolyte interphase(SEI) film on spinel LiMn2O4 electrode surface was studied by electrochemical impedance spectroscopy(EIS) during the initial storage in 1 mol/L LiPF6-EC:DMC:DEC electrolyte and in the subsequent first charge-discharge cycle. It has been demonstrated that the SEI film thickness increased with the increase of storage time and spontaneous reactions occurring between spinel LiMn2O4 electrode and electrolyte can be prevented by the SEI film. In the first charge-discharge cycle succeeding the storage, the electrolyte oxidation coupled with Li-ion insertion is evidenced as the main origin to increase the resistance of SEI film. The results also confirm that the variations of the charge transfer resistance(Rot) with the electrode potential(E) can be well described using a classical equation. 相似文献
996.
<正>(译自APS News,2001年10月)19世纪的仪器几乎没有一个像巴贝(Charles Babbage,1791~1871)的计算器一样,对现代科技有如此大的影响力,其中最著名的是分析机(Analytical Engine),它是机械操作的数字计算器,几乎有着现在计算机中的每一要素。巴贝的概念最先于1837年提出,说明一个巨大的铜装置,以蒸汽为动力,做为一般用途的机械计算器,激励了19世纪一些最伟大心智的人,但他并未能成功说 相似文献
997.
聚碳酸酯(PC)与聚酯做成合金后可发生酯交换反应,影响材料的性能及稳定性,采用几种不同的手段去量化这二者之间的反应,为阻燃合金配方的设计提供指导作用。利用差式扫描量热仪(DSC)和静态热分析仪(TMA)对PC与聚酯之间的反应程度进行判别及量化。结果表明,酯交换反应程度越小时,DSC和TMA测试结果是DSC测得?t_m和?t_c越小,TMA测得的平均线性膨胀系数越大。 相似文献
999.
A Fractional element model describes a special kind of viscoelastic material. Its stress is proportional to the fractional-order derivative of strain. Physically the mechanical analogies of fractional elements can be represented by spring-dashpot fractal networks. We introduce a constitutive operator in the constitutive equations of viscoelastic materials. To derive constitutive operators for spring-dashpot fractal networks, we use Heaviside operational calculus, which provides explicit answers not otherwise obtainable simply. Then the series-parallel formulas for the constitutive operator are derived. Using these formulas, a constitutive equation of fractional element with 1/2-order derivative is obtained. Finally we find the way to derive the constitutive equations with other fractional-order derivatives and their mechanical analogies. 相似文献
1000.
The mechanics of cardiovascular stents during the process of expansion are very important for stent function and safety. In general, finite element method (FEM) or experi- ments are major methods used to ascertain mechanical prop- erties of the stent. In this paper, we develop a theoretical model of the tubular stent, derive formulas for the axial forces and moments on the stent end, and propose formu- las for the plastic limit pressure vs. the stent's radius during expansion. Examples covering different geometrical param- eters and material parameters are provided, and the plastic limit pressures calculated by FEM and the present method are compared, proving that the present formulas are acceptable and meaningful for the design and innovation of the stent. 相似文献