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排序方式: 共有5085条查询结果,搜索用时 187 毫秒
71.
Hongyang Su Lanlan Chen Yizhen Chen Prof. Rui Si Yuting Wu Xiaonan Wu Dr. Zhigang Geng Prof. Wenhua Zhang Prof. Jie Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20591-20596
Efforts have been devoted to achieving a highly efficient artificial synthesis of ammonia (NH3). Reported herein is a novel Fe-MoS2 catalyst with Fe atomically dispersed onto MoS2 nanosheets, imitating natural nitrogenase, to boost N2 electroreduction into NH3 at room temperature. The Fe-MoS2 nanosheets exhibited a faradic efficiency of 18.8 % with a yield rate of 8.63 μg mgcat.−1 h−1 for NH3 at −0.3 V versus the reversible hydrogen electrode. The mechanism study revealed that the electroreduction of N2 was promoted and the competing hydrogen evolution reaction was suppressed by decorating the edge sites of S in MoS2 with the atomically dispersed Fe, resulting in high catalytic performance for the electroreduction of N2 into NH3. This work provides new ideas for the design of catalysts for N2 electroreduction and strengthens the understanding about N2 activation over Mo-based catalysts. 相似文献
72.
Summary Pressure and temperature have significant influence on retention in HPLC. This study investigates the effect of pressure and
temperature on the retention behavior of aromatic hydrocarbons (toluene, ethyl benzene, butyl benzene, pentyl benzene) and
polar, acidic and basic samples (phenol, acetophenone, N,N-dimethyl aniline, benzophenone) on a reversed phase column. The
effect has been studied on non-porous, tetradecyl (C14) coated silica particles. We found that the adsorption-induced decrease of the partial molar volume of the solutes investigated
was between ΔV
m
=5–15 cm3 mol−1. The increment of the decrease of the partial molar volume due to the addition of one CH2 group, for the homologous series of the aromatic hydrocarbons is approximately ΔV
CH2
=2.3 cm3mol−1.
Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001. 相似文献
73.
This paper reports the results on a study of ion chromatography (IC) behaviour on strong cationic exchange column of CH3-(CH2)n−1-NH2 (n=1-6) type linear monoamines. The eluents were mixtures of HCl-NaCl, HNO3-NaNO3, HClO4-NaClO4, H2SO4-Na2SO4, HClO4-NaClO4-CH3CN. Amines were revealed with an amperometric detector. The influence of different counter-ions on retention factors, k′, is discussed. Relationships between k′ and pE (E=sum of Na+ and H+ concentrations), and length of alkylic chain, and sensitivity coefficient S, are reported and discussed. The addition of acetonitrile (ACN) in the eluent was also taken into account. Suitable considerations are derived from these data. An example of monoamines separation is given. 相似文献
74.
The synthesis and basic photophysical characteristics of a novel green fluorescent polyvinylcarbazole polymer containing 4‐N,N‐dimethylaminoethyleneamino‐1,8‐naphthalimide side chains has been described. The ability to sense metal cations has been monitored by fluorescence emission spectroscopy. It is shown that the fluorescent intensity is very sensitive to the Fe2+ cations and the copolymer can be used as an homogeneous and heterogeneous fluorescent sensor for Fe2+ cations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
75.
用CoMFA和HQSAR两种QSAR方法研究了50个乙内酰脲类分子的定量构效关系.本研究从构象搜索所得的低能结构出发构建化合物分子的构象, 建立CoMFA模型,并进行了全空间搜索. HQSAR本质上是一种二维的QSAR方法,与CoMFA方法相比,该方法在数据处理方面,比CoMFA方法快捷,并且可重复性好.两种方法均得到了较好分析结果, CoMFA的交叉验证相关系数q2 值为0.815, HQSAR的q2值为0.893.这些方程有力地说明了该类分子在(R,R)-N-3,5-dinitrobenzoyl-1,2-diamine型手性固定相上拆分过程中的影响因素,对今后类似拆分的实验研究提供了理论支持. 相似文献
76.
Van der Avert P Podkolzin SG Manoilova O de Winne H Weckhuysen BM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(7):1637-1646
The catalytic destruction of carbon tetrachloride in the presence of steam, CCl(4) + 2 H(2)O-->4 HCl + CO(2), was investigated at 200-350 degrees C over a series of lanthanide (La, Ce, Pr and Nd) and alkaline-earth metal (Mg, Ca, Sr and Ba) oxide-based catalysts with kinetic experiments, Raman spectroscopy, X-ray photoelectron spectroscopy, IR spectroscopy, X-ray diffraction, and DFT calculations. This new catalytic reaction was achieved by combining destructive adsorption of CCl(4) on a basic oxide surface and concurrent dechlorination of the resulting partially chlorinated solid by steam. The combination of the two noncatalytic reactions into a catalytic cycle provided a rare opportunity in heterogeneous catalysis for studying the nature and extent of surface participation in the overall reaction chemistry. The reaction is proposed to proceed over a terminal lattice oxygen site with stepwise donation of chlorine atoms from the hydrocarbon to the surface and formation of the gas-phase intermediate COCl(2), which is readily readsorbed at the catalyst surface to form CO(2). In a second step, the active catalyst surface is regenerated by steam with formation of gas-phase HCl. Depending on the reaction conditions, the catalytic material was found to transform dynamically from the metal oxide state to the metal oxide chloride or metal chloride state due to the bulk diffusion of oxygen and chlorine atoms. A catalyst obtained from a 10 wt % La(2)O(3)/Al(2)O(3) precursor exhibited the highest destruction rate: 0.289 g CCl(4) h(-1) g(-1) catalyst at 350 degrees C, which is higher than that of any other reported catalyst system. 相似文献
77.
We report microscopic calculations of free energies and entropies for intramolecular electron transfer reactions. The calculation algorithm combines the atomistic geometry and charge distribution of a molecular solute obtained from quantum calculations with the microscopic polarization response of a polar solvent expressed in terms of its polarization structure factors. The procedure is tested on a donor–acceptor complex in which ruthenium donor and cobalt acceptor sites are linked by a four-proline polypeptide. The reorganization energies and reaction energy gaps are calculated as a function of temperature by using structure factors obtained from our analytical procedure and from computer simulations. Good agreement between two procedures and with direct computer simulations of the reorganization energy is achieved. The microscopic algorithm is compared to the dielectric continuum calculations. We found that the strong dependence of the reorganization energy on the solvent refractive index predicted by continuum models is not supported by the microscopic theory. Also, the reorganization and overall solvation entropies are substantially larger in the microscopic theory compared to continuum models. 相似文献
78.
79.
80.
Dielectric properties of plasma polymerized PVCa and composite PVCa:Au films had been analyzed in the frequency range from 10 to 105 Hz. In order to explain experimental data obtained the modification of Maxwell-Garnett and Bruggeman self-consistent models for the case of three-component composite has been done. The theoretical analysis performed allows to determine peculiarities of dielectric behavior of a three-component system, as well as to disclose the procedure of evaluation of third-component parameters. Results of this analysis are in agreement with experimental ones. 相似文献