全文获取类型
收费全文 | 7859篇 |
免费 | 221篇 |
国内免费 | 127篇 |
专业分类
电工技术 | 123篇 |
综合类 | 343篇 |
化学工业 | 1163篇 |
金属工艺 | 420篇 |
机械仪表 | 194篇 |
建筑科学 | 90篇 |
矿业工程 | 43篇 |
能源动力 | 765篇 |
轻工业 | 121篇 |
水利工程 | 32篇 |
石油天然气 | 37篇 |
武器工业 | 9篇 |
无线电 | 736篇 |
一般工业技术 | 1634篇 |
冶金工业 | 151篇 |
原子能技术 | 208篇 |
自动化技术 | 2138篇 |
出版年
2024年 | 8篇 |
2023年 | 252篇 |
2022年 | 149篇 |
2021年 | 172篇 |
2020年 | 263篇 |
2019年 | 196篇 |
2018年 | 186篇 |
2017年 | 354篇 |
2016年 | 485篇 |
2015年 | 365篇 |
2014年 | 582篇 |
2013年 | 523篇 |
2012年 | 459篇 |
2011年 | 491篇 |
2010年 | 374篇 |
2009年 | 459篇 |
2008年 | 299篇 |
2007年 | 400篇 |
2006年 | 343篇 |
2005年 | 248篇 |
2004年 | 147篇 |
2003年 | 139篇 |
2002年 | 174篇 |
2001年 | 179篇 |
2000年 | 120篇 |
1999年 | 164篇 |
1998年 | 80篇 |
1997年 | 48篇 |
1996年 | 46篇 |
1995年 | 47篇 |
1994年 | 41篇 |
1993年 | 32篇 |
1992年 | 36篇 |
1991年 | 40篇 |
1990年 | 38篇 |
1989年 | 48篇 |
1988年 | 74篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1976年 | 6篇 |
1974年 | 8篇 |
1973年 | 12篇 |
排序方式: 共有8207条查询结果,搜索用时 31 毫秒
61.
《Journal of Network and Computer Applications》2012,35(5):1598-1605
Mobile wireless sensor networks (MWSNs), the continuous movement of sensor nodes, may cause complete disconnection of the network or at best a part of it. The design of such networks should guarantee that all sensor nodes at all times have a path to the sink node(s). Prolonging the lifetimes of the MWSNs is a crucial design issue but should not be at the expense of other essential functions such as connectivity. In this paper, we propose an energy efficient distributed framework for connectivity maintenance of MWSNs. In the proposed framework, sensor nodes of the MWSNs schedule and control their radio frequency (RF) modules based on dynamic coordinated reconstruction mechanism, some senor nodes may lose their connectivity with the network due to mobility, depletion of energy and/or incurred faults. Two protocols are developed to patch up the disconnection of the MWSNs. The first protocol reestablishes the network connection consuming far less energy than state-of-the-art alternatives. However, it is capable of reestablishing the connection when no more than 20% of the MWSN backbone nodes lose connection concurrently. The second protocol extends this limit to operate when up to 35% of the MWSN backbone nodes lose connection simultaneously. 相似文献
62.
《Journal of Network and Computer Applications》2012,35(6):2059-2067
RFID (Radio Frequency IDentification) based communication solutions have been widely used nowadays for mobile environments such as access control for secure system, ticketing systems for transportation, and sport events. These systems usually depend on readers that are not continuously connected to a secure backend system. Thus, the readers should be able to perform their duties even in offline mode, which generally requires the management by the readers of the susceptible data. The use of RFID may cause several security and privacy issues such as traceability of tag owner, malicious eavesdropping and cloning of tags. Besides, when a reader is compromised by an adversary, the solution to resolve these issues getting worse. In order to handle these issues, several RFID authentication protocols have been recently proposed; but almost none of them provide strong privacy for the tag owner. On the other hand, several frameworks have been proposed to analyze the security and privacy but none of them consider offline RFID system.Motivated by this need, in this paper, we first revisit Vaudenay's model, extend it by considering offline RFID system and introduce the notion of compromise reader attacks. Then, we propose an efficient RFID mutual authentication protocol. Our protocol is based on the use of physically unclonable functions (PUFs) which provide cost-efficient means to the fingerprint chips based on their physical properties. We prove that our protocol provides destructive privacy for tag owner even against reader attacks. 相似文献
63.
In this paper, we present a formulation of the quaternion constraint for rigid body rotations in the form of a standard perfect
bilateral mechanical constraint, for which the associated Lagrangian multiplier has the meaning of a constraint force. First,
the equations of motion of a scalable body are derived. A scalable body has three translational, three rotational, and one
uniform scaling degree of freedom. As generalized coordinates, an unconstrained quaternion and a displacement vector are used.
To the scalable body, a perfect bilateral constraint is added, restricting the quaternion to unit length and making the body
rigid. This way a quaternion based differential algebraic equation (DAE) formulation for the dynamics of a rigid body is obtained,
where the 7×7 mass matrix is regular and the unit length restriction of the quaternion is enforced by a mechanical constraint.
Finally, the equations of motion in the form of a DAE are linked to the Newton–Euler equations of motion of a rigid body.
The rigid body DAE formulation is useful for the construction of (energy) consistent integrators. 相似文献
64.
General competence trust among supply chain partners, referring to the trust that a partner holds the general ability of fulfilling contracts, is a critical factor to ensure effective cooperation in a supply chain, especially in the current financial crisis. The method of supply chain trust diagnosis (SCTD) is to evaluate whether or not a partner holds such competence. This research devotes to an early investigation on diagnosing competence trust of supply chain with the method of inductive case-based reasoning ensemble (ICBRE). The so-called supply chain trust diagnosis with inductive case-based reasoning ensemble consists of five levels, that is, information level, the level of ratios of general competence states, the level of inductive case-based reasoning, ensemble level, and diagnosis result level. Knowledge for diagnosing competence trust, which composes of a case base, is hidden in data represented by ratios of general competence states. Inductive approach is combined with randomness to construct diverse and good member methods of inductive case-based reasoning. Finally, simple voting is used to integrate outputs of member inductive case-based reasoning methods in order to produce the final diagnosis on whether or not a partner holds the general ability of fulfilling contracts. We statistically validated results of the method of supply chain trust diagnosis with inductive case-based reasoning ensemble by comparing them with those of multivariate discriminant analysis, logistic regression, single Euclidean case-based reasoning, and single inductive case-based reasoning. The results indicate that the method of supply chain trust diagnosis with inductive case-based reasoning ensemble significantly improves predictive capability of case-based reasoning in this problem and outperforms all the comparative models by group decision of several decision-making agents and non-strict assumptions like statistical methods. 相似文献
65.
This paper presents a short term load forecasting model based on Bayesian neural network (shorted as BNN) learned by the Hybrid Monte Carlo (shorted as HMC) algorithm. The weight vector parameter of the Bayesian neural network is a multi-dimensional random variable. In learning process, the Bayesian neural network is considered as a special Hamiltonian dynamical system, and the weights vector as the system position variable. The HMC algorithm is used to learn the weight vector parameter with respect to Normal prior distribution and Cauchy prior distribution, respectively. The Bayesian neural networks learned by Laplace algorithm and HMC algorithm and the artificial neural network (ANN) learned by the BP algorithm were used to forecast the hourly load of 25 days of April (Spring), August (Summer), October (Autumn) and January (Winter), respectively. The roots mean squared error (RMSE) and the mean absolute percent errors (MAPE) were used to measured the forecasting performance. The experimental result shows that the BNNs learned by HMC algorithm have far better performance than the BNN learned by Laplace algorithm and the neural network learned BP algorithm and the BNN learned by HMC has powerful generalizing capability, it can welly solve the overfitting problem. 相似文献
66.
We consider penetration of magnetic flux in the rare earth ceramic superconductors within the framework of a generalized Ginzburg-Landau theory, based on the coexistence of antiferromagnetism and superconductivity. We study vortex structure produced for a magnetic field close to
. We make a new prediction that may serve to test the theory experimentally. 相似文献
67.
Journal of Computational Electronics - Here we consider an informationally complete Wigner function approach to look at multiple atoms (qubits) coupled to a field mode. We consider the... 相似文献
68.
To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 103 nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nanoclusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc., properties at the membrane-water interface is attracting increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties. 相似文献
69.
In this paper we consider a conservative discretization of the two-dimensional incompressible Navier–Stokes equations. We propose an extension of Arakawa’s classical finite difference scheme for fluid flow in the vorticity–stream function formulation to a high order discontinuous Galerkin approximation. In addition, we show numerical simulations that demonstrate the accuracy of the scheme and verify the conservation properties, which are essential for long time integration. Furthermore, we discuss the massively parallel implementation on graphic processing units. 相似文献