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991.
助剂SiO2对CO2加氢制二甲醚催化剂Cu-ZnO/HZSM-5性能的影响 总被引:6,自引:1,他引:6
考察了助剂SiO2对CO2加氢合成二甲醚催化剂Cu-ZnO/HZSM-5性能的影响,并用X射线衍射、程序升温还原和X射线光电子能谱等手段对催化剂进行了表征. 结果表明,加入少量的SiO2即可显著提高CO2的转化率、二甲醚的选择性以及二甲醚和甲醇的总选择性,并降低副产物CO的选择性,同时改善催化剂的稳定性; 但SiO2加入量大时,催化活性反而降低. SiO2的存在可使焙烧后催化剂的晶型结构发生改变,促进CuO和ZnO的分散,并提高CuO的还原温度. SiO2的加入抑制了反应过程中催化剂上Cu0和ZnO晶粒的长大,对活性物种Cu0有稳定作用,从而有利于提高催化剂的活性和稳定性. 相似文献
992.
993.
Adsorption of ethane in a slit shaped micropore system has been studied by Monte Carlo molecular simulation by considering
this hydrocarbon as a two interacting sites molecule. Ethane adsorption in pore sizes from 0.41 to 1.66 nm was simulated at
303 K. Microscopic characteristics of the adsorbed phase have been studied for pores of different size, comparing two density
profiles: the molecule centre of mass profile and the molecular interaction site profile. Averaged angle distribution of molecule
positions with respect to the slit plane across the pore width has been also obtained by simulation. These results were related
to ethane molecule packing efficiency, which is also related to the adsorption capacity in terms of the adsorbed phase density.
Packing efficiency presents an oscillation shape as the result of the adsorbate disorder inside the pore.
Pressure influence on the adsorption has been studied by following pore filling by simulation. When pore condensation takes
place and for pressures above condensation, fluid-fluid interactions are determinant in molecule disorder observed between
the two adsorbed layers. 相似文献
994.
Xinhuan Yan Junqing Sun Yongbin Fang Zhenyuan Xu Wenjing Wang 《Frontiers of Chemistry in China》2006,1(1):41-44
The Pt-Sn-B/carbon nanotubes (CNTs) catalyst was prepared by impregnation-chemical reduction method. Its catalytic performance
was evaluated by liquid-phase hydrogenation of chloronitrobenzene (CNB). The results showed that the catalyst had higher catalytic
performance than common hydrogenation catalysts. The conversion of CNB could reach 99.9%, and the dechlorination of chloroaniline
(CAN) was less than 1.9% when catalyzed by Pt-Sn-B/CNTs and more than 8.0% when catalyzed by common hydrogenation catalysts.
X-ray diffraction and selected area electron diffraction analysis showed that Pt-Sn-B/CNTs had an amorphous alloy structure
that can improve catalytic performance. Transmission electron micrograph image showed that the catalyst particles were highly
distributed on the surface of CNTs. The hydrodechlorination of CNB was mainly affected by the unique structure of CNTs and
the nature of the amorphous metals on the surface of CNTs. The relationship between the interaction of CNTs and amorphous
metals and the catalytic performance of the catalyst is also discussed.
Translated from the Chinese Journal of Catalysis, 2005, 26(3) (in Chinese) 相似文献
995.
996.
Jinglai Zhang Yonghong Li Junfeng Li Xing Chen Zexing Cao 《International journal of quantum chemistry》2009,109(5):1116-1126
The density functional theory (DFT) and the complete active space self‐consistent‐field (CASSCF) method have been used for full geometry optimization of carbon chains C2nH+ (n = 1–5) in their ground states and selected excited states, respectively. Calculations show that C2nH+ (n = 1–5) have stable linear structures with the ground state of X3Π for C2H+ or X3Σ? for other species. The excited‐state properties of C2nH+ have been investigated by the multiconfigurational second‐order perturbation theory (CASPT2), and predicted vertical excitation energies show good agreement with the available experimental values. On the basis of our calculations, the unsolved observed bands in previous experiments have been interpreted. CASSCF/CASPT2 calculations also have been used to explore the vertical emission energy of selected low‐lying states in C2nH+ (n = 1–5). Present results indicate that the predicted vertical excitation and emission energies of C2nH+ have similar size dependences, and they gradually decrease as the chain size increases. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 相似文献
997.
铁氧化还原蛋白在多壁碳纳米管上的固定、表征及直接电子转移 总被引:4,自引:0,他引:4
将来源于Spinacia Oleracea的铁氧化还原蛋白(ferredoxin, SOFd)固定在多壁碳纳米管(CNT)表面, 紫外-可见及红外光谱表明, SOFd在CNT表面没有变性, 仍保持原来的二级空间结构. 循环伏安结果表明, SOFd在CNT表面能进行有效和稳定的直接电子转移反应, 伏安曲线上出现一对良好的、几乎对称的氧化还原峰, 式量电位E0'为(-570.4±1.5) mV (vs. SCE, 0.1 mol/L磷酸盐缓冲液), 且不随扫速和溶液pH值的变化而变化. SOFd直接电子转移的表观速率常数ks为(0.73±0.04) s-1. 相似文献
998.
999.
大气颗粒物中总碳含量的测量不确定度评定 总被引:1,自引:0,他引:1
分析了元素分析仪测定大气颗粒物中碳质组分的测量不确定度来源,对总碳含量的测量不确定度进行了评估。测定咖啡碱标准样品中的碳含量,称样量为1 500~2 500μg时,测定结果为(49.27±0.26)%;测定大气颗粒物样品中的总碳含量,样品面积为3.14 cm2时,测定结果为(106±3)μg/cm2。 相似文献
1000.
Pt/C和Pt/CNTs电极的电化学稳定性研究 总被引:1,自引:0,他引:1
采用恒电位氧化法研究了Pt/C和Pt/CNTs电极的电化学稳定性. 相同条件下, Pt/C电极的氧化电流大约为Pt/CNTs电极的2倍; 120 h氧化后, Pt/C电极Pt的电化学表面积下降了21.3%, 而Pt/CNTs电极仅下降了7.6%, 表明Pt/CNTs电极性能衰减较慢. X射线光电子能谱(XPS)分析表明, Pt/C的载体碳黑表面氧增加量大于Pt/CNTs中碳纳米管(CNTs)表面氧的增加量, 说明碳黑的被氧化程度较高, 电化学稳定性差; Pt的表面化学状态没有发生变化; 碳纳米管本身的抗电化学氧化性也大于碳黑. 所以, 载体的被氧化程度不同是两种电极性能衰减不同的主要原因之一, 并且排除了Pt表面状态的影响. 相似文献