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991.
992.
The temperature-dependence of the electrical resistance of Al-Zn 78 wt.% was measured during linear cooling of the samples in the range of eutectoidal decomposition. The resulting resistancevs. temperature curves were analysed by: deriving the temperature-dependence of the volume fractionx(T) of theη precipitate; fitting the theoretical functionx(T)=x h (T)+x c (T) following from numerical integration of the reaction rate equations for the simultaneously occurring homogeneous (H) and cellular (C) precipitation processes. As a result, the activation energiesE h andE c , the JMA exponentsn h andn c , the rate constantsk h andk c , and the critical temperaturesT o of the two processes were estimated. 相似文献
993.
Apparent molar volumes of aqueous solutions of argon and xenon have been calculated using a previously developed comprehensive equation of state for nonelectrolyte systems. The equation consists of a virial expansion truncated after the fourth virial coefficient and a closed-form term approximating higher coefficients. Mixing rules are based on the composition dependence of virial coefficients, which is known from statistical mechanics. The equation accurately represents vapor-liquid and gas-gas equilibria for the Ar+H2O and Xe+H2O systems over wide ranges of pressure and temperature using two binary parameters. With the binary parameters determined from phase equilibrium data, the equation accurately predicts apparent molar volumes V in the near-critical and far-from-critical regions. Apart from reproducing experimental V data, the equation reveals remarkable maxima of V as a function of pressure and temperature in the near-critical region. The implications of this equation with respect to the Ar–H2O potential are discussed via the second virial coefficient. 相似文献
994.
Summary A new Schiff base ligand, N,N-bis(l-ferrocenyl-1-oxo-3-methyl)propenylethylenediamine (H2L) and its copper(II), zinc(II), cobalt(II), nickel(II), cadmium(II) and manganese(II) complexes have been prepared, and the structure of the copper complex has been determined by single crystal X-ray techniques and refined to R = 0.041 for 7403 independent reflections. The copper atom is situated in a distorted planar environment. The dihedral angle between planes of two chelating rings which do not contain the metal is 33.5°. Two substituted Cp rings are conjugated with two chelating acacim rings. The iron-centroid forms an angle of 179.4°. The Cp rings are twisted from the eclipsed conformation. 相似文献
995.
多维核磁共振技术的飞速发展议得其在生物大分子结构测定方面的应用已经达到可以与【射线晶体学并驾齐驱的地步.蛋白质结构堆积紧密,较适合于用核磁共振方法给出确定的结构.与蛋白质不同的是多肽的柔性较大,在溶液中可能存在多种构象,核磁共振实验给出的只是平均信息*.利用核磁,(振数据构建分子结构模型常用的方法有距离几何、分子动力学等,在由核磁共振NOESZ得到的距离信息足够多时可以给出较好的结果问.由于多肽本身的特点:柔性较大,由核磁共振得到的距离信息较少等,利用距离几何、分子动力学方法进行构象搜索时容易陷入… 相似文献
996.
Min Jiang Junliang Chen Dr. Yuanyuan Ma Prof. Wei Luo Prof. Jianping Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9320-9327
Recently, the frequency of combining MXene, which has unique properties such as metal-level conductivity and large specific surface area, with silicon to achieve excellent electrochemical performance has increased considerably. There is no doubt that the introduction of MXene can improve the conductivity of silicon and the cycling stability of electrodes after elaborate structure design. However, most exhaustive contacts can only improve the electrode conductivity on the plane. Herein, a MXene@Si/CNTs (HIEN-MSC) composite with hierarchical interpenetrating electroconductive networks has been synthesized by electrostatic self-assembly. In this process, the CNTs are first combined with silicon nanoparticles and then assembled with MXene nanosheets. Inserting CNTs into silicon nanoparticles can not only reduce the latter‘s agglomeration, but also immobilizes them on the three-dimensional conductive framework composed of CNTs and MXene nanosheets. Therefore, the HIEN-MSC electrode shows superior rate performance (high reversible capacity of 280 mA h−1 even tested at 10 A g−1), cycling stability (stable reversible capacity of 547 mA h g−1 after 200 cycles at 1 A g−1) and applicability (a high reversible capacity of 101 mA h g−1 after 50 cycles when assembled with NCM622 into a full cell). These results may provide new insights for other electrodes with excellent rate performance and long-cycle stability. 相似文献
997.
Dr. Guanzhao Wu Yangxue Liu Hossein Rouh Liulei Ma Yao Tang Sai Zhang Peng Zhou Jia-Ying Wang Shengzhou Jin Dr. Daniel Unruh Dr. Kazimierz Surowiec Prof. Dr. Yanzhang Ma Prof. Dr. Guigen Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(30):8013-8020
The first asymmetric catalytic approach to multilayer 3D chirality has been achieved by using Suzuki-Miyaura cross-couplings. New chiral catalysts were designed and screened under various catalytic systems that proved chiral amide-phosphines to be more efficient ligands than other candidates. The multilayer 3D framework was unambiguously determined by X-ray structural analysis showing a parallel pattern of three layers consisting of top, middle and bottom aromatic rings. The X-ray structure of a catalyst complex, dichloride complex of Pd-phosphine amide, was obtained revealing an interesting asymmetric environment nearby the Pd metal center. Three rings of multilayer 3D products can be readily changed by varying aromatic ring-anchored starting materials. The resulting multilayer products displayed strong luminescence under UV irradiation and strong aggregation-induced emission (AIE). In the future, this work would benefit not only the field of asymmetric synthesis but also materials science, in particular polarized organic electronics, optoelectronics and photovoltaics. 相似文献
998.
Ao Yu Guoming Ma Jintian Jiang Yajing Hu Mingming Su Wangtao Long Shixin Gao Dr. Hsien-Yi Hsu Dr. Ping Peng Prof. Fang-Fang Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(40):10405-10412
Inspired by the spongy bone structures, three-dimensional (3D) sponge-like carbons with meso-microporous structures are synthesized through one-step electro-reduction of CO2 in molten carbonate Li2CO3−Na2CO3−K2CO3 at 580 °C. SPC4-0.5 (spongy porous carbon obtained by electrolysis of CO2 at 4 A for 0.5 h) is synthesized with the current efficiency of 96.9 %. SPC4-0.5 possesses large electrolyte ion accessible surface area, excellent wettability and electronical conductivity, ensuring the fast and effective mass and charge transfer, which make it an advcanced supercapacitor electrode material. SPC4-0.5 exhibits a specific capacitance as high as 373.7 F g−1 at 0.5 A g−1, excellent cycling stability (retaining 95.9 % of the initial capacitance after 10000 cycles at 10 A g−1), as well as high energy density. The applications of SPC4-0.5 in quasi-solid-state symmetric supercapacitor and all-solid-state flexible devices for energy storage and wearable piezoelectric sensor are investigated. Both devices show considerable capacitive performances. This work not only presents a controllable and facile synthetic route for the porous carbons but also provides a promising way for effective carbon reduction and green energy production. 相似文献
999.
Michał Terlecki Dr. Szymon Sobczak Dr. Michał K. Leszczyński Prof. Andrzej Katrusiak Prof. Janusz Lewiński 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(55):13757-13764
Understanding the factors governing the formation of supramolecular structures and phase transitions between various forms of molecular crystals is pivotal for developing dynamic, stimuli-responsive materials and polymorph-controlled syntheses. Here, we investigate the pressure-induced dynamic of both the intrinsic molecular structure and the supramolecular network of a predesigned polyhedral oxo-centered zinc cluster incorporating monoanionic N,N’-diphenylformamidinate and featuring N-bonded phenyl groups in close proximity to the primary coordination sphere. We demonstrate that the model oxo cluster is prone to undergoing pressure-induced conformational transformations of the secondary coordination sphere and simultaneous stepwise (initially every second polyhedral molecule undergoes the conformational transformations) and reversible transitions from an ambient phase α to high-pressure phases β and γ, as single-crystal-to-single-crystal events. The observed phase transitions illustrate the key role of an interplay between the low-energy conformation perturbations and cooperative intra- and intermolecular noncovalent interactions. 相似文献
1000.