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排序方式: 共有1511条查询结果,搜索用时 10 毫秒
921.
922.
XiaoFeng Huang QianBiao Zhao LingYan He Min Hu QiJing Bian Lian Xue YuanHang Zhang 《中国科学:化学(英文版)》2010,53(12):2593-2599
Secondary organic aerosol (SOA) is one of the major components of aerosols in the atmosphere and has not been well understood so far. Due to the complex chemical composition of organic aerosols, the identification of SOA has been a hotspot and difficult issue in the field of aerosol study. This study attempts to quantitatively identify SOA in winter of Shenzhen based on positive matrix factorization (PMF) analysis. Major sources were resolved and SOA was identified subsequently according to the characteristic ion fragments measured by highly time-resolved aerosol mass spectrometer measurement. It showed that in the winter of Shenzhen the average SOA concentration was 9.41 ± 6.33 μg/m3, accounting for 39.9 ± 21.8% of the total organic mass. Compared with primary organic aerosol (POA), the SOA concentrations had no large variation, suggestive of characteristics of regional secondary pollutants. The ratio of SOA/BC had pronounced diurnal variation, similar to that of O x (O3+NO2), indicating SOA formation was significantly controlled by activity of photochemistry in the atmosphere. The most effective period for SOA formation was from 9 am ~3 pm since the SOA/BC ratio increased by 122% during this period. This study provides a new technical method and a new idea for SOA investigation. 相似文献
923.
Yuhui Qu Wanyong Ma Xiufang Bian Hongwei Tang Weixing Tian 《International journal of quantum chemistry》2006,106(4):960-967
The geometry, electronic configurations, harmonic vibrational frequencies, and stability of the structural isomers of boron phosphide clusters have been investigated using density functional theory (DFT). CCSD(T) calculations show that the lowest‐energy structures are cyclic (IIt, IVs) with Dnh symmetry for dimers and trimers. The caged structure for B4P4 lie higher in energy than the monocyclic structure with D2d symmetry (VIs). The B–P bond dominates the structures for many isomers, so that one preferred dissociation channel is loss of the BP monomer. The hybridization and chemical bonding in the different structures are also discussed. Comparisons with boron nitride clusters, the ground state structures of BnPn (n = 2, 3) clusters are analogous to those of their corresponding BnNn (n = 2, 3) counterparts. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
924.
肝硬化患者血清铜,锌含量测定与分析 总被引:4,自引:0,他引:4
检测了30例肝硬化患者血清铜,锌含量,同时与30例健康人进行对照,结果显示,肝硬化患者血铜明显增高,血锌明显降低,与健康人对照组有显著差异。 相似文献
925.
Li Chunlin Fu Yilu Meng Ming Bian Guozhu Xie Yaning Hu Tiandou Zhang Jing 《化学物理学报(中文版)》2004,17(1):95-99
The Ni/CeO2 -ZrO2 -Al2O3 catalyst was prepared with the hydrothermal method. The catalytic performance for the CO2 reforming of CH4 reaction with or without small amount of steam was tested and the amount of coke deposition was measured. The XAFS of Ni K-edge was attained. The results show that the formation of CeAlO3 occurs in reaction,but the coke deposition is responsible for the deactivation of the catalyst. The addition of steam into feed gas can decrease the amount of coke deposition,and promote the stability. Due to the carbon atom penetration into the Ni lattice,for the catalyst sample after reaction without the addition of steam into feed gas,the coordination number of the first Ni-Ni shell decreases sharply. For the catalyst sample after reaction with the addition of steam in feed gas,the coordination numbers of the first Ni-Ni shell decrease slightly. It is due to the addition of steam into feed gas,which can suppress the coke formation and maintain the metallic structure of active Ni metal. 相似文献
926.
Lei?Yang Yi?Peng Fang?Bian Shi-ping?YanEmail author Dai-zheng?Liao Peng?Cheng Zong-hui?Jiang 《Journal of chemical crystallography》2005,35(7):555-559
A new dinuclear complex, [Cu2(TPA)2(o-phth)](ClO4)2 (TPA = tris(2-pyridylmethyl) amine, o-phth = terephthalato dianion), was synthesized and characterized by X-ray crystallography. The unit of dinuclear Cu(II) was bridged by terephthalato dianion. The complex crystallizes in triclinic space group P1, with a = 8.287(3) Å, b = 10.623(4) Å, c = 13.818(5) Å; α = 92.077(7)∘, β = 94.768(7)∘, γ = 90.352(6)∘; V = 1211.4(8) Å3; Z = 2; R1 = 0.0604, wR2 = 0.1707. In the temperature range 4–300 K, magnetic measurement shows that the exchange interaction of the two metal ions is weak ferromagnetic with J = 1.20 cm−1, g = 1.97. 相似文献
927.
928.
微量贵金属对Co/γ-Al_2O_3的作用及其结构表征Ⅱ.Co-M/γ-Al_2O_3的XAFS表征 总被引:1,自引:0,他引:1
采用XAFS方法分别对Co的近边结构和配位状态进行了详细的表征.XANES的结果表明,所有样品中Co均处于不对称的配位环境中,在吸收阈值处,形成了1s→4p吸收峰,并且该峰发生了分裂,尤其是Co/γ-Al2O3分裂现象最为明显.对于Co-M/γ-Al2O3(M=Pt,Pd,Rh),这种不对称性可能来源于Co的高度分散性及贵金属与Co之间的相互作用,而对于Co/γ-Al2O3,则与四面体配位的Co2+离子有关.EXAFS结果表明,含贵金属样品中,Co均以零价形式存在,和标样Co粉相比,Co-Co键长略有增加,而配位数较标样下降许多.配位数的下降,表明Co具有高度的分散性,而键长的增加可能是贵金属与Co的相互作用削弱了Co-Co键引起的. 相似文献
929.
930.
Formations of Active Species and By-Products in Water by Pulsed High-Voltage Discharge 总被引:1,自引:0,他引:1
Formations of active species and by-products are different from bubbling different gases in a pulsed high-voltage discharge
reactor. The identification of all the products and the formation rate determination of active species are quite important
as the process is applied to wastewater disposal. Serials of measurements were conducted to do the identifications and determinations
in this paper. Amounts of · OH all increased but that of H2O2 all decreased by bubbling gas. The · OH formation rate was 3.49 × 10−7, 3.56 × 10−7, 3.21 × 10−7 and 1.94 × 10−7 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen respectively, but it was 1.61 × 10−7 mol s−1 l−1 without bubbling. Without any bubbling, the H2O2 formation rate was up to 6.53 × 10−6 mol l−1 s−1, while it was 9.97 × 10−7, 1.663 × 10−7, 1.73 × 10−6 and 3.14 × 10−6 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen, respectively. NO2− and NO3− was detected in discharged water with bubbling nitrogenous gas. Their formation made the pH decreased. 相似文献