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861.
Well-crystalline CeO2 nanowires were prepared via a surfactant-assisted hydrothermal process. Reaction temperature and reaction time were changed for the determination of
optimal synthesis parameters. The as-obtained products were characterized by X-ray diffraction (XRD), high-resolution transmission
electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The results show that single crystal
CeO2 nanowires with high yield and good uniformity can be obtained hydrothermally at 180°C for 12 h with the aid of 2.0 g surfactant
(polyvinyl pyrrolidone, PVP). The role of PVP was then discussed and a possible growth mechanism was proposed. Moreover, room
temperature photoluminescence (PL) spectra were obtained for these CeO2 nanowires, which are believed to be related to the abundant defects in these nanostructures. 相似文献
862.
FuWei Yang Yan Liu GuoFang Zuo YuanCheng Zhu BingJian Zhang PingNing Hua 《科学通报(英文版)》2012,57(13):1590-1594
Fluorapatite protective films were prepared on marble substrates using a biomimetic method. By mimicking the mineralization mechanism of enamel, phosphorus and fluorine were introduced on the surface of the marble substrate. In the presence of a biological template, namely collagen, an integrated fluorapatite film was produced and the marble substrate was entirely covered. The prepared fluorapatite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. The performances of the fluorapatite films were evaluated by color changes, capillary water absorption, and acid resistance tests. The results revealed that the fluorapatite films had good compatibility with the marble substrate; the physical properties such as color and capillary water adsorption of the marble substrates were unchanged. The fluorapatite films also had good acid resistance and were stable even in heavy acid rain. 相似文献
863.
A numerical method to simulate the coupled oscillations of flexible structures in flowing fluids 总被引:1,自引:0,他引:1
A numerical method is developed to simulate the coupled phenomena in a fluid-flexible-structure system. Specifically, a two-dimensional
panel method is used to calculate the hydrodynamic forces and a modal superposition method is adopted to solve the governing
equation of an Eulerian beam. The stability boundary of a single flexible beam in a uniform flow is calculated and compared
with previous results to verify the validity of the code. The flow-induced flapping of a single and two flexible bodies for
S=1.0, U*=7.0 are investigated. For the flow-induced vibration of a single beam, the oscillation frequency is close to the secondary
natural frequency of a cantilever. For two parallel flexible beams, they oscillate in phase when the non-dimensional separating
distance H<0.25. When H>0.25, the out-of-phase mode occurs with a jump in frequency. When H>1, the interaction between the two beams decouples and the frequency and forces of each beam revert to behavior associated
with a single beam in the same flow. Simulations of coupled-flapping of two tandem flexible structures proved that the drag
acting on the upstream body is reduced while for that downstream drag is obviously increased when the structures are closely
arranged. The numerical results obtained in the present work are qualitatively consistent with early experimental results. 相似文献
864.
Oskar Michalski Ewa Bidzińska Michał Borowski Krystyna Dyrek Paweł Olko Liliana Stolarczyk Jan Swakoń Piotr Tomasik Elżbieta Wenda 《科学通报(英文版)》2010,55(31):3556-3561
Cornstarch heated in the range of 230–280°C depolymerized into pyrodextrins characterized by two-component EPR signals of relatively stable free radicals. These thermally generated radicals could serve as efficient scavengers for free radicals generated from pyrodextrins with the 200 Gy dose of γ-radiation. The most efficient traps/scavengers were produced from cornstarch at 250–280°C. IR data indicated incorporation of the OH groups to the pyrodextrins. These groups most probably originated from the OH· radicals formed by the radiolysis of water. EPR spectra provided evidence for trapping free radicals generated by γ-irradiation and for their subsequent annihilation on contact with pyrodextrins. Water affected radical processes occurring in pyrodextrins caused by γ-irradiation. 相似文献
865.
L. Vanderkelen J. M. Van Herreweghe K. G. A. Vanoirbeek G. Baggerman B. Myrnes P. J. Declerck I. W. Nilsen C. W. Michiels L. Callewaert 《Cellular and molecular life sciences : CMLS》2011,68(6):1053-1064
Lysozymes are antibacterial effectors of the innate immune system in animals that hydrolyze peptidoglycan. Bacteria have evolved
protective mechanisms that contribute to lysozyme tolerance such as the production of lysozyme inhibitors, but only inhibitors
of chicken (c-) and invertebrate (i-) type lysozyme have been identified. We here report the discovery of a novel Escherichia coli inhibitor specific for goose (g-) type lysozymes, which we designate PliG (periplasmic lysozyme inhibitor of g-type lysozyme).
Although it does not inhibit c- or i-type lysozymes, PliG shares a structural sequence motif with the previously described
PliI and MliC/PliC lysozyme inhibitor families, suggesting a common ancestry and mode of action. Deletion of pliG increased the sensitivity of E. coli to g-type lysozyme. The existence of inhibitors against all major types of animal lysozyme and their contribution to lysozyme
tolerance suggest that lysozyme inhibitors may play a role in bacterial interactions with animal hosts. 相似文献
866.
867.
Jean-Pierre Vilardaga Guillermo Romero Peter A. Friedman Thomas J. Gardella 《Cellular and molecular life sciences : CMLS》2011,68(1):1-13
The parathyroid hormone (PTH) receptor type 1 (PTHR), a G protein-coupled receptor (GPCR), transmits signals to two hormone
systems—PTH, endocrine and homeostatic, and PTH-related peptide (PTHrP), paracrine—to regulate different biological processes.
PTHR responds to these hormonal stimuli by activating heterotrimeric G proteins, such as GS that stimulates cAMP production. It was thought that the PTHR, as for all other GPCRs, is only active and signals through
G proteins on the cell membrane, and internalizes into a cell to be desensitized and eventually degraded or recycled. Recent
studies with cultured cell and animal models reveal a new pathway that involves sustained cAMP signaling from intracellular
domains. Not only do these studies challenge the paradigm that cAMP production triggered by activated GPCRs originates exclusively
at the cell membrane but they also advance a comprehensive model to account for the functional differences between PTH and
PTHrP acting through the same receptor. 相似文献
868.
An approach of three-dimensional seismic ray tracing is presented, which is derived from adopting two-dimensional linear traveltime
interpolation (LTI). By adjusting the forward process using the partition of grid interface, and backward step by considering
more directions, the new approach is suitable for the application of three-dimensional models. The calculation results show
that, with the same accuracy, the improved 3-D method is much faster than the method of traditional LTI directly applied in
the three-dimensional case. 相似文献
869.
谭平山是中国近代史上有建树、有影响的民主革命家.辛亥革命时,他追随孙中山加入同盟会;五四运动后,他在陈独秀的帮助下建立中共广东支部.在第一次国共合作中,在轰轰烈烈的农民运动中,在著名的南昌起义中,都留下了他不可磨灭的历史功绩.他组建中华革命党,创建三民主义同志联合会,组织中国国民党革命委员会,参加新政协,特别是在响应中共“五一”口号、开展新政协运动中,他的主张和影响为民革和各民主党派接受中国共产党领导、协商建国,发挥了积极的作用. 相似文献
870.
To investigate the feasibility of using complex networks in the study of linguistic typology, this paper builds and explores 15 lin-guistic complex networks based on the dependency syntactic treebanks of 15 languages. The results show that it is possible to classify human languages by means of the following main parameters of complex networks: (a) average degree of the node, (b) cluster coefficients, (c) average path length, (d) network centralization, (e) diameter, (f) power exponent of degree distribution, and (g) the determination coefficient of power law distributions. The precision of this method is similar to the results achieved by means of modern word order typology. This paper tries to solve two problems of current linguistic typology. First, the language sample of a typological study is not real text; second, typological studies pay too much attention to local language structures in the course of choosing typological parameters. This study performs better in global typological features of language and not only enhances typological methods, but it is also valuable for developing the applications of complex networks in the humanities, social, and life sciences. 相似文献