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951.
Improvement of tundish shape and optimization of flow control devices for sequence casting heavy steel ingots 下载免费PDF全文
The metallurgical effect of a round tundish used to cast heavy steel ingots in machine works at present was evaluated through water modeling experiments. The flow control devices of the improved oval tundish, which was used instead of the round tundish, had been optimized. The results show that the residence time of the round tundish is short, its inclusion removal efficiency is too low, and it has more dead zones and an unreasonable flow field. Compared with the round tundish, the improved oval tundish with the optimized weir and dam has a better effect:its minimum residence time is prolonged by 38.1 s, the average residence time is prolonged by 233.4 s, its dead volume fraction decreases from 26% to 15%, and the ratio of plug volume fraction to dead volume fraction increases from 0.54 to 1.27. The inclusion removal efficiency also increases by 17.5%. 相似文献
952.
Investigation on the explosive welding mechanism of corrosion-resisting aluminum and stainless steel tubes through finite element simulation and experiments 下载免费PDF全文
Guo-fa Sui Jin-shan Li Hong-wei Li Feng Sun Tie-bang Zhang Heng-zhi Fu 《矿物冶金与材料学报》2012,19(2):151-158
To solve the difficulty in the explosive welding of corrosion-resistant aluminum and stainless steel tubes, three technologies were proposed after investigating the forming mechanism through experiments. Then, a 3D finite element model was established for systematic simulations in the parameter determination. The results show that the transition-layer approach, the coaxial initial assembly of tubes with the top-center-point the detonation, and the systematic study by numerical modeling are the key technologies to make the explosive welding of LF6 aluminum alloy and 1Cr18Ni9Ti stainless steel tubes feasible. Numerical simulation shows that radial contraction and slope collision through continuous local plastic deformation are necessary for the good bonding of tubes. Stand-off distances between tubes (D1 and D2) and explosives amount (R) have effect on the plastic deformation, moving velocity, and bonding of tubes. D1 of 1 mm, D2 of 2 mm, and R of 2/3 are suitable for the explosive welding of LF6-L2-1Cr18Ni9Ti three-layer tubes. The plastic strain and moving velocity of the flyer tubes increase with the increase of stand-off distance. More explosives (R>2/3) result in the asymmetrical distribution of plastic strain and non-bonding at the end of detonation on the tubes. 相似文献
953.
This paper deals with the stabilization of the nonholonomic systems with strongly nonlinear uncertainties. The objective is
to design an output feedback law such that the closed-loop system is globally asymptotically regulated at the origin. The
systematic strategy combines the input-state scaling technique with the backstepping technique. A novel switching control
strategy based on the output measurement of the first subsystem is employed to make the subsystem far away from the origin.
The simulation demonstrates the effectiveness of the proposed controller. 相似文献
954.
Software systems are a typical kind of man-made complex systems. Understanding their evolutions can lead to better software
engineering practices. In this paper, the authors use complex network theory as a tool to analyze the evolution of object-oriented
(OO) software from a multigranularity perspective. First, a multi-granularity software networks model is proposed to represent
the topological structures of a multi-version software system from three levels of granularity. Then, some parameters widely
used in complex network theory are applied to characterize the software networks. By tracing the parameters’ values in consecutive
software systems, we have a better understanding about software evolution. A case study is conducted on an open source OO
project, Azureus, as an example to illustrate our approach, and some underlying evolution characteristics are uncovered. These
results provide a different dimension to our understanding of software evolutions and also are very useful for the design
and development of OO software systems. 相似文献
955.
This paper considers the problem of minimizing the VaR and CTE of an insurer’s retained risk by controlling the combinational
quota-share and stop-loss reinsurance strategy. With a constrained reinsurance premium, the authors give the explicit reinsurance
forms and the minimal VaR and CTE of retained risk in the case of quota-share after stop-loss reinsurance and the case of
stop-loss after-quota-share reinsurance respectively. Finally, the authors conclude that the quota-share after stop-loss is
a better reinsurance strategy than stop-loss after quota-share to minimize the VaR and CTE with a same constrained reinsurance
premium. And the pure stop-loss reinsurance is preferred for an insurer with a high level regulatory requirement. 相似文献
956.
The objective of this paper is to study the issue of design efficiency for minimum projection uniformity designs. The results
show that for orthogonal arrays with strength two, the minimum projection uniformity criterion is a good surrogate for the
design efficiency criterion proposed by Cheng, Deng and Tang (2002). 相似文献
957.
This paper discusses the H
∞ control problem for a class of linear stochastic systems driven by both Brownian motion and Poisson jumps. The authors give
the basic theory about stabilities for such systems, including internal stability and external stability, which enables to
prove the bounded real lemma for the systems. By means of Riccati equations, infinite horizon linear stochastic state-feedback
H
∞ control design is also extended to such systems. 相似文献
958.
Preventing rumor spreading on small-world networks 总被引:1,自引:0,他引:1
Since the spreading of harmful rumors can deeply endanger a society, it is valuable to investigate strategies that can efficiently
prevent hazardous rumor propagation. To conduct this investigation, the authors modify the SIR model to describe rumor propagation
on networks, and apply two major immunization strategies, namely, the random immunization and the targeted immunization to
the rumor model on a small-world network. The authors find that when the average degree of the network is small, both two
strategies are effective and when the average degree is large, neither strategy is efficient in preventing rumor propagation.
In the latter case, the authors propose a new strategy by decreasing the credibility of the rumor and applying either the
random or the targeted immunization at the same time. Numerical simulations indicate that this strategy is effective in preventing
rumor spreading on the small-world network with large average degree. 相似文献
959.
A general complex delayed dynamical network model with asymmetric coupling matrix is considered in this paper. For reducing
the conservativeness of synchronization criteria, several novel synchronization stability conditions are presented by using
delay decomposition methods. Numerical examples which are widely used to study delay-dependent synchronization stability are
given to illustrate the effectiveness of the proposed methods. 相似文献
960.
José Afonso de Oliveira Amarildo Jorge da Silva 《Systemic Practice and Action Research》2011,24(6):565-574
The context of this analysis is the golden years of the decade of the 1960s that served as a backdrop for consolidating capitalism
and the globalized world. The aim is to analyze, understand and establish possible connections between the arts in general
and the world in which modern society operates. This is a theoretical essay anchored in theoretical assumptions of sociology,
arts and the culture of the globalized world and built on the practical experience of these researchers. We use the interpretative
approach and technique of hermeneutic phenomenology to give meaning to historical events and the cultural and artistic implications
of these events in the rise of science and technology. A systemic examination supports the relationship between art, culture,
science and technology. The evidence shows that artistic and cultural issues are essential to make sense of life in society
and in the absence of such basis, the world would be meaningless and humans would lose a sense of direction. It can be concluded
that the arts are becoming increasingly relevant as the virtual world becomes large-scale and truly global, and that the development
of science and technology benefits from the rise of the cultural and artistic world of today. Finally, the correspondence
between the artistic and cultural world and the current scientific and technological development confirms the emergence of
a globalized, digitalised (virtual) knowledge society. 相似文献