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981.
Exfoliated Pt-clay/Nafion nanocomposite membrane for self-humidifying polymer electrolyte fuel cells
Zhang W Li MK Yue PL Gao P 《Langmuir : the ACS journal of surfaces and colloids》2008,24(6):2663-2670
Monolayers of Pt nanoparticles of diameters of 2-3 nm with a high crystallinity were successfully anchored onto exfoliated nanoclay surfaces using a novel chemical vapor deposition process. Chemical bonding of Pt to the oxygen on the clay surface ensured the stability of the Pt nanoparticles, and hence, no leaching of Pt particles was observed after a prolonged ultrasonication and a rigorous mechanical agitation of Pt-clay in the Nafion solution during the membrane casting process. Systematic analysis using WAXD and TEM showed that the recasting process produced a new self-humidifying exfoliated Pt-clay/Nafion nanocomposite membrane with a high crystallinity and proton conductivity. In situ water production for humidification of the dry membranes without any external humidification was characterized by a combined water uptake and FTIR analysis of the as-prepared membrane after a single cell testing without using electrodes. The power density at 0.5 V of a single cell made of a Pt-clay/Nafion nanocomposite membrane was 723 mW/cm2, which is 170% higher than that made of a commercial Nafion 112 membrane of similar thickness. No compromise in mechanical properties was observed. 相似文献
982.
Shanshan Sun Litao Wang Jiasheng Wang Wenjing Lv Qinghua Yu Dong Pei Siqi Han Xingyu Li Miao Wang Sheng Liu Xiangao Quan Mei Lv 《Journal of separation science》2023,46(16):2200935
In this work, homochiral reduced imine cage was covalently bonded to the surface of the silica to prepare a novel high-performance liquid chromatography stationary phase, which was applied for the multiple separation modes such as normal phase, reversed-phase, ion exchange, and hydrophilic interaction chromatography. The successful preparation of the homochiral reduced imine cage bonded silica stationary phase was confirmed by performing a series of methods including X-ray photoelectron spectroscopy, thermogravimetric analysis, and infrared spectroscopy. From the extracted results of the chiral resolution in normal phase and reversed-phase modes, it was demonstrated that seven chiral compounds were successfully separated, among which the resolution of 1-phenylethanol reached the value of 3.97. Moreover, the multifunctional chromatographic performance of the new molecular cage stationary phase was systematically investigated in the modes of reversed-phase, ion exchange, and hydrophilic interaction chromatography for the separation and analysis of a total of 59 compounds in eight classes. This work demonstrated that the homochiral reduced imine cage not only achieved multiseparation modes and multiseparation functions performance with high stability, but also expanded the application of the organic molecular cage in the field of liquid chromatography. 相似文献
983.
The density functional theory was used to investigate the adsorption of CH4 and H2O on different rank coal surfaces.The coal rank is the dominant factor in affecting the adsorption capacity of coal.In order to better understand gas and water interaction with coal of different maturity,we developed fourteen coal models to represent the different rank coal.The interactions of CH4 and H2O with coal surfaces were studied and characterized by their adsorption energies,Mulliken charges and electrostatic potential surfaces.The results revealed that the interaction between coal and CH4 was weak physical adsorption,and that the interaction between coal and H2 O consisted of physical and chemical adsorption.Adsorption energy of coal–H2O system was larger than that of coal–CH4 on all rank coals,suggesting that the adsorption priority in the coal models is H2 O > CH4.Consequently,the injection of H2 O into the different rank coal could effectively enhance the coal bed methane(CBM) recovery. 相似文献
984.
In this article, we study the large time behavior of the 3-D isentropic compressible Navier-Stokes equation in the partial space-periodic domains, and simultaneously show that the related profile systems can be described by like Navier-Stokes equations with suitable"pressure" functions in lower dimensions. Our proofs are based on the energy methods together with some delicate analysis on the corresponding linearized problems. 相似文献
985.
Yue Li Fangfang Li Yanyan Zhu Xue Li Ziyuan Zhou Chunmei Liu Wenjing Zhang Mingsheng Tang 《Structural chemistry》2016,27(4):1165-1173
In this work, three possible reaction pathways (Path 1, Path 2 and Path 3) for the generation process of cyclic dipeptide from amino acid have been investigated in detail using density functional theory. Path 1 and Path 2 are the intramolecular reaction processes, while Path 3 involves the intermolecular reaction process that assisted with water molecule. Our calculated results indicate that Path 3 is more energy favorable than Path 1 and Path 2. There are four steps in Path 3 proceed from the amino acid to cyclic dipeptide. The first step is two adjacent amino acids to form precursor of dipeptide, the second step is the removal of water molecule of precursor of dipeptide for the formation of the linear dipeptide, the third step is generation of precursor of cyclic dipeptide associated with other hydrogen atom transfer, and the last step is another dehydration process to generate the final product of cyclic dipeptide. Moreover, the obtained results indicate that the generation mechanisms of different cyclic dipeptides are similar, and the energy barrier of the rate-determined step influenced somewhat by the hydrophilic or hydrophobic group linked to the Cα atom. Additionally, the potential energy profiles suggest that the generation reactions of the studied nine cyclic dipeptides are exothermic processes. The detailed mechanisms should be helpful for people to understanding the title reaction at the molecular level, and the proposed novel intermolecular process might provide valuable insights on rational improve reaction condition for this type of reaction. 相似文献
986.
987.
用非真空Bridgman方法制备了掺有Tb杂质的氟化铅(PbF2:Tb)晶体,闯杂浓度从0.008at.%至0.6at.%。在室温下测量了该晶体的吸收和发射光谱,发现该晶体在X-射线和紫外线激发下均能够发出比较强的荧光。FbF2:Tb晶体的光吸收起源于Tb^3 离子的4f-4f跃迁,而其光发射则源于Tb^3 离子的电子分别从其激发态^5D3和^5D4能级路迁到基态^7Fj(J=6,5,4,3,2)。 荧光强度随掺杂浓度的提高而提高,当Tb^3 离子浓度较低时,以^5D3→^7FJ跃迁发射为主,当Tb^3 离子浓度较高时,则以^5D4→^7FJ跃迁发射为主。在同一晶体中,发光强度随中心所占晶格位置的改变而改变,反映出Tb^3 离子在PbF2晶体中的分布具有分凝系数大于1的特征。推测Tb^3 离子在PbF2晶体中占据Pb格位,同时产生间隙F^-离子缺陷来平衡电价。 相似文献
988.
双反射膜双频He-Ne激光器双频特性及偏振特性的实验研究 总被引:2,自引:1,他引:1
本文对 5 MHz频差双反射膜双频 He- Ne激光器输出激光的双频特性及偏振特性进行了实验研究。研究结果表明 ,当磁场方向同反射膜的一个本征模方向基本重合时 ,有双频出现 ;当磁场方向同反射膜的一个本征模方向夹角在 45°左右时 ,无双频出现。输出激光的偏振方向由反射膜的本征模确定 ,其偏振非正交程度为 tgρ≤ 0 .0 0 87,椭圆化程度tgβ随激光管与磁场的相对角位置变化而发生变化。在合适的位置 ,tgβ可以小至 2 / 70 0。该种外差光源具有较好的偏振特性。 相似文献
989.
Population of Unstable Nuclides and Nuclear Temperature Extraction in 46.7MeV/u 12C Induced Reaction 下载免费PDF全文
XI Hong-Fei ZHAN Wen-Long ZHU Yong-Tai GUO Zhong-Yan HU Xiao-Qing LIU Guan-Hua ZHOU Jian-Qun YIN Shu-Zhi ZHAO You-Xong WEI Zhi-Yong FAN En-Jie 《中国物理C(英文版)》1993,17(4):294-299
The experiment results of unstable nucliaes decay by using the light charged particle correlation function obtained in 12C 46.7MeV/u+58Ni experiment are reported.Under the assumption of statistical equilibrium,the nuclear temperatures are extracted,and the influence of the reaction mechanism on the nuclear temperature are also investigated. 相似文献
990.
XU Zi-Zong GONG Zhu-Fang CHANG Jin SHI Chao-Shu SHEN Ding-Zhong YUAN Xiang-Long YIN Zi-Wen 《中国物理C(英文版)》1993,17(2):107-113
The spectra and decay times of a serious of Ce+3—doped BaF2 crystals have been determined.The results demonstrate that a BaF2 crystal with a proper amount of Ce+3 doped have some outstanding advantages:a near-blue fluorescence with quite fast decay time (80ns) replaces the slow component (600ns) and vary fast one (~0.8ns) of undoped BaF2.The intensity of the new component is comparable with the sum of the old ones. 相似文献