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101.
A procedure for packing 15 cm × 1 mm id reverse-phase microbore columns with 3 μm silicas obtained from different manufacturers is described. The speed of analysis and detection limits are compared to those obtained with a 50 cm × 1 mm id column packed with 10 μm ODS. The effect of detector time constant on the system, and flow rates on column efficiency are also examined. 相似文献
102.
邻位吡啶自由基多通道分解反应的动力学和反应机理研究 总被引:1,自引:0,他引:1
Utilizing Gaussian94 program package, all species involved in decomposition reactions of o-pyridyl radical were optimized fully at B3LYP/6-311++G^** level. Intrinsic reaction coordinate calculations were employed to confirm the connections of the transition states and products, and transition states were ascertained by the number of imaginary frequency (0 or 1). The reaction mechanism was elucidated by the vibrational mode analysis and electronic population analysis, and the reaction rate constants were calculated with transition state theory. 相似文献
103.
A new copper(Ⅱ) compound with imino nitroxide radicals [Cu(IM-MeImz)2]·(SCN)2 (IM-meImz =2-(5-methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl) has been synthesized and characterized structurally and magnetically. It crystallizes in monoclinic, space group P21/c with a = 9.3604(7), b = 10.3012(7), c = 16.6684(12) (A), β = 105.0290(10)°, V = 1552.25(19)(A)3, C24H34CuN10O2S2, Mr = 622.27, Z = 2, Dc = 1.331 g/cm3, μ(MoKα) = 0.876 mm-1, F(000) =650, the final R = 0.0374 and wR = 0.1079. X-ray analysis demonstrates that the IM-MeImz ligand is coordinated to the copper(Ⅱ) ion as an unusual didentate chelate with a κ2 N(MeImz),O(IM) mode in the complex. The square-planar coordination sites at Cu(Ⅱ) are occupied by two O and two N atoms from the imino nitroxide radicals. The complex molecules are connected as a onedimensional polymer structure by intermolecular interactions. Magnetic measurements show that there are intramolecular antiferromagnetic interactions between the Cu(Ⅱ) ion and radicals. 相似文献
104.
The chromatographic behavior of phenols in reversed-phase mode liquid chromatography differs from that of non-ionic compounds such as alkyl alcohols, alkylbenzenes, halogenated benzenes, polyaromatic hydrocarbons, and aromatic acids. Therefore, the retention times of 61 phenols were measured in a system of an octadecyl bonded silica gel and acetonitrile/water mixtures. The logarithm of the capacity ratio (log k') was found to be a linear function of the hydrophobicity (log P) in acidic acetonitrile/water mixtures. This result was applied to a different octadecyl bonded silica gel. Eight phenols were selected as standard compounds, and their log k' values were measured in 0.05 M phosphoric acid in 10 to 90% acetonitrile/water mixtures. An empirical polynomial relation was obtained between the concentration of acetonitrile and the slope of the log k' vs log P curve. Finally the capacity ratio of all phenols were calculated in given eluents by the equations derived from the measurements of standard compounds and the calculated log P values. The difference between predicted capacity ratios and measured ones was within 10%. 相似文献
105.
In situ pulsed force mode scanning force microscopy (PFM-SFM) images of phase separated solid-supported lipid bilayers are discussed with the help of computer simulations. Simultaneous imaging of material properties and topography in a liquid environment by means of PFM-SFM is severely hampered by hydrodynamic damping of the cantilever. Stiffness and adhesion images of solid-supported membranes consisting of cholesterol, sphingomyelin, and 1,2-dioleyl-phosphatidylcholine obtained in aqueous solution exhibit contrast inversion of adhesion and stiff. ness images depending on parameters such as driving frequency, amplitude, and trigger setting. Simulations using a simple harmonic oscillator model explain experimental findings and give a deeper insight into the way PFM-SFM experiments have to be performed in order to obtain interpretable results and hence pave the way for reliable material contrast imaging at high speed. 相似文献
106.
以高校基础化学实验"从海带中提取碘""三草酸合铁(Ⅲ)酸钾的制备"为例,分别探讨了微视频技术在化学基本操作实验和综合设计型实验中的具体应用;此外,举例说明利用Flash软件制作的虚拟微视频可以在仪器分析实验中清晰地再现仪器真实操作中的每一个步骤,弥补了学生在实验前无法实际操作仪器的不足。实践证明,微视频技术的应用,丰富了基础化学实验教学模式,增强了学生自主学习的能力和动手能力,提高了实验成功率和实验教学效果。 相似文献
107.
Xiang Pu Hanguang Wang Ping Zou Guangtu Wang Guizhou Yue Kuan Liu Li Cheng Juhua Feng Huixian Zhang Qianming Huang Hanbing Rao 《大学化学》1986,36(1):2002053-0
The crop science of Sichuan Agricultural University is an authorized first-class discipline. As the strategic supporting department for innovative talent cultivation in agriculture and forestry major, we are facing a long-term challenge in reforming the teaching mode for basic course-organic chemistry and cultivating talented students with solid basic knowledge and strong sense of innovation. Herein a thorough survey was performing to establish the executable teaching programs for this course during the "Double-First Class Universities Plan" period. A multidimensional teaching resource library for organic chemistry course was also constructed. The new classroom teaching mode "Interest cultivation-Creative thought development-Autonomous and Cooperative learning", along with a stepwise practice teaching mode "Foundation skills-Integrated application-Innovative trial" was proposed and practiced among thirty-five majors including agriculture, forestry and veterinary, to improve the quality for innovative talent cultivation and support our first-class discipline construction. This research could probably serve as a reference for congeneric agricultural university. 相似文献
108.
With the combination of the the stoichiometric displacement model for retention (SDM-R) in reversed phase liquid chromatography (RPLC) and the stoichiometric displacement model for adsorption (SDM-A) in physical chemistry,the total number of moles of the re-solvated methanol of stationary phase side.nr,and that of solute side in the mobile phase,q,corresponding the one mole of the desorbing solute,were separately determined and referred as the characterization parameters of the contributions of the adsorption mechanism and partition mechanism to the solute retention,respectively.A chromatographic system of insulin,using mobile phase consisting of the pseudo-homologue of alcohols(methanol,ethanol and 2-propanol)-water and trifluoroacetic acid was employed.The maximum number of the methanol layers on the stationary phase surface was found to be 10.6,only 3 of which being valid in usual RPLC,traditionally referred as a volume process in partition mechanism.However,it still follows the SDM-R.Both of q and nr of insulin were found not to be zero,indicating that the retention mechanism of insulin is a mixed mode of partition mechanism and adsorption mechanism.When methanol is used as the organic modifier,the ratio of q/nr was 1.13,indicating the contribution to insulin retention due to partition mechanism being a bit greater than that due to adsorption mechanism.A linear relationship between q,or nr and the carbon number of the pseudo-homologue in the mobile phase was also found.As a methodology for investigating the retention mechanism retention and behavior of biopolymers.a homologue of organic solvents as the organic modifier in mobile phase has also been explored. 相似文献
109.
喜树碱类抗肿瘤药物作用模式的柔性分子对接研究 总被引:3,自引:0,他引:3
研究采用柔性分子对接技术,将15个喜树碱类化合物对接到拓扑异构酶I (Topo I)-DNA切割复合物中,从原子水平和分子力场角度阐明了喜树碱类抗肿瘤药 物与DNA,Topo I的相互作用机制。研究发现,喜树碱分子插入Topp I-DNA复合物 的切割位点,并与Asn722,Asp533,Lys532和Lys720形成氢键作用网络。定量构效 关系研究进一步表明喜树碱分子可以与Topo I-DNA切割复合物形成电荷迁移作用。 该对接模型系统解释了喜树碱类化合物的构效关系、定点突变等诸多实验事实,为 下一步设计、合成新型高效的喜树碱类衍生物打下了坚实基础。 相似文献
110.
The voltammetric behavior of the LMF-Mg(II) complex with DNA at a mercury electrode is reported for the first time. In NH3–NH4Cl buffer (pH=9.10), the adsorption phenomena of the LMF–Mg(II) complex were observed by linear sweep voltammetry. The mechanism of the electrode reaction was found to be a reduction of LMF in the complex, and the composition of the LMF–Mg(II) complex is 2:1. In the presence of calf thymus DNA (ctDNA), the peak current of LMF–Mg(II) complex decreased considerably, and a new well-defined adsorptive reduction peak appeared at −1.63 V (vs. SCE). The electrochemical kinetic parameters and the binding number of LMF–Mg(II) with ctDNA were also obtained. Moreover, the new peak currents of LMF–Mg(II)–DNA system increased linearly correlated to the concentration of DNA in the 4.00×10−7–2.60×10−6 g ml−1 range when the concentrations of LMF–Mg(II) complex was fixed at 5.00×10−6 mol l−1, with the detection limits of 2.33×10−7 g ml−1. An electrostatic interaction was suggested by electrochemical method. 相似文献