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951.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(3):649-655
An adaptive controller for stabilization of unknown unstable steady states (spirals, nodes and saddles) of nonlinear dynamical systems is considered and its robustness under the changes of the location of the fixed point in the phase space is demonstrated. An analog electronic controller, based on a low-pass filter technique, is described. It can be easily switched between a stable and an unstable mode of operation for stabilizing either spirals/nodes or saddles, respectively. Numerical and experimental results for two autonomous systems, the damped Duffing–Holmes oscillator and the chaotic Lorenz system, are presented. 相似文献
952.
Emma Kushtina Oleg Zaikin Przemysław Różewski Bartłomiej Małachowski 《European Journal of Operational Research》2009
The decision about curriculum modification usually takes place at the knowledge level, mainly with consideration of individual academic staff competences and qualifications. However, traditional approaches to cost estimation of curriculum modification are focused on material resources only. In this paper we present a cost estimation method and decision model for curriculum modification in educational organizations. The proposed method works at the knowledge level and employs competence sets as knowledge representation models in educational organizations. Authors used the theory of hierarchical, multilevel systems in order to define the model of the decision-making process of curriculum modification and its dimension. Basing on this and also using a fuzzy competence model the cost estimation algorithm in the form of a group competences expansion algorithm is proposed. The algorithm focuses on the cost of staff competence expansion caused by the knowledge development process. 相似文献
953.
954.
955.
Exponential networked synchronization of master-slave chaotic systems with time-varying communication topologies 下载免费PDF全文
The networked synchronization problem of a class of master-slave chaotic systems with time-varying communication topologies is investigated in this paper. Based on algebraic graph theory and matrix theory, a simple linear state feedback controller is designed to synchronize the master chaotic system and the slave chaotic systems with a time- varying communication topology connection. The exponential stability of the closed-loop networked synchronization error system is guaranteed by applying Lyapunov stability theory. The derived novel criteria are in the form of linear matrix inequalities (LMIs), which are easy to examine and tremendously reduce the computation burden from the feedback matrices. This paper provides an alternative networked secure communication scheme which can be extended conveniently. An illustrative example is given to demonstrate the effectiveness of the proposed networked synchronization method. 相似文献
956.
Jon Zarate Gustavo Puras David Mecerreyes Haritz Sardon J. L. Pedraz 《Journal of polymer science. Part A, Polymer chemistry》2017,55(2):280-287
Non‐viral gene delivery vectors have emerged as potential alternatives in the field of gene therapy by replacing the biological viral vectors. DNA–cationic polymer complexes are one of the most promising systems to target many inborn or acquired diseases without the utilization of conventional drugs. Despite the excellent binding efficiency of cationic polymers, the gene transfection seems limited to date. In this work, a series of ammonium‐based block‐copolymers with different alkyl side chains (ethyl, butyl, and hexyl) and functionality (alcohol, amine, and alkyl) have been prepared to evaluate their capacity to deliver genetic material. First, different ionic liquid monomers with different pendent functional groups were prepared and characterized. Then, polyplexes elaborated with different polymers at several polymer DNA ratios (w/w) were characterized in terms of size, zeta potential, and DNA binding, release, and protection capacity. Finally, the transfection efficiency and cell viability was evaluated in ARPE19 cells. We found that only the systems containing the amine pendent group were able to transfect ARPE19 cell and, that this amine containing polymer was less cytotoxic even at high polymer/DNA ratios (30:1). In conclusion, our studies suggested that the proper selection of the pendent group substantially impacts overall transfection efficiency of cationic polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 280–287 相似文献
957.
Zaizai Tong Junyi Zhou Runsheng Huang Jie Zhou Runke Zhang Wangqian Zhuo Guohua Jiang 《Journal of polymer science. Part A, Polymer chemistry》2017,55(15):2477-2482
Dual photo‐ and pH‐responsive polymeric vesicles are constructed from a host–guest complex between a water‐soluble pillar[6]arene and an azobenzene ended functionalized poly(ε‐caprolactone). Reversible morphological transitions between vesicles and solid aggregates are achieved upon repeated UV stimulus and pH stimulus. Moreover, the polymeric vesicles present excellent cytocompatibility toward HepG2 cells and can be further applied for controlled release of a hydrophilic model drug, DOX?HCl. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2477–2482 相似文献
958.
For sonochemical processing on an industrial scale the traditional choice is either a batch or flow system. The former is straightforward in concept but it requires large scale powerful ultrasonic transducers capable of delivering high intensity ultrasound to large volumes of liquid. Unfortunately at the moment the cost and problems involved in building very large sonication devices for batch processes cannot justify the replacement of existing industrial processes. For this reason most sonochemists prefer some form of flow system where small quantities of reagents can be treated as they are pumped from a large vat of reagents through a smaller sonochemical reactor where high intensity ultrasound can be applied. In this short paper we draw attention to a problem which seems common in a number of papers dealing with such flow systems – a confusion between the terms continuous reactor and loop reactor. Further we emphasise the importance of calculating the actual amount of ultrasonic processing experienced by the reaction mixture within the sonication zone of a loop reactor during its operation. The parameters required for such a calculation are: ultrasonic processor volume (Rv in L), pump flow rate (Fr in L/min), stock solution volume in the reservoir (Sv in L) and the overall system operating time (So in min). 相似文献
959.
S. Mizzi R. W. Barber D. R. Emerson J. M. Reese S. K. Stefanov 《Continuum Mechanics and Thermodynamics》2007,19(5):273-283
This paper presents a new technique that combines Grad’s 13-moment equations (G13) with a phenomenological approach to rarefied
gas flows. This combination and the proposed solution technique capture some important non-equilibrium phenomena that appear
in the early continuum-transition flow regime. In contrast to the fully coupled 13-moment equation set, a significant advantage
of the present solution technique is that it does not require extra boundary conditions explicitly; Grad’s equations for viscous
stress and heat flux are used as constitutive relations for the conservation equations instead of being solved as equations
of transport. The relative computational cost of this novel technique is low in comparison to other methods, such as fully
coupled solutions involving many moments or discrete methods. In this study, the proposed numerical procedure is tested on
a planar Couette flow case, and the results are compared to predictions obtained from the direct simulation Monte Carlo method.
This test case highlights the presence of normal viscous stresses and tangential heat fluxes that arise from non-equilibrium
phenomena, which cannot be captured by the Navier–Stokes–Fourier constitutive equations or phenomenological modifications.
相似文献
960.
S. Tomasiello 《Nonlinear dynamics》2007,50(1-2):37-48
In this paper, the nonlinear planar response of a hinged–hinged buckled beam to a primary-resonance excitation of its first
vibration mode is computed by a new numerical scheme. The beam is subjected to an axial force beyond the critical load of
the first buckling mode and to a transverse harmonic excitation. The nonlinear dynamical problem is solved by deducing directly
the discretized equations governing the problem thanks to a new approach, here called DQ based approach, since it is based
on the application of the quadrature rules of the DQM. As it will be shown, for the problem here considered, the minimum number
of degrees of freedom to be retained to limit the numerical errors is four. Computer simulations of the dynamic behaviour
of the discretized system are conducted by means of the IDQ method, a method proposed and recently generalized by the author.
A sequence of supercritical period-doubling bifurcations leading to chaos, snapthrough motions and quasi-periodic motions
can be observed, similarly to some cases existing in literature. 相似文献