全文获取类型
收费全文 | 11040篇 |
免费 | 1765篇 |
国内免费 | 1208篇 |
专业分类
电工技术 | 1657篇 |
综合类 | 1540篇 |
化学工业 | 717篇 |
金属工艺 | 326篇 |
机械仪表 | 771篇 |
建筑科学 | 651篇 |
矿业工程 | 169篇 |
能源动力 | 218篇 |
轻工业 | 292篇 |
水利工程 | 271篇 |
石油天然气 | 325篇 |
武器工业 | 206篇 |
无线电 | 1639篇 |
一般工业技术 | 1442篇 |
冶金工业 | 349篇 |
原子能技术 | 167篇 |
自动化技术 | 3273篇 |
出版年
2024年 | 61篇 |
2023年 | 183篇 |
2022年 | 381篇 |
2021年 | 434篇 |
2020年 | 522篇 |
2019年 | 398篇 |
2018年 | 413篇 |
2017年 | 471篇 |
2016年 | 522篇 |
2015年 | 503篇 |
2014年 | 723篇 |
2013年 | 724篇 |
2012年 | 857篇 |
2011年 | 832篇 |
2010年 | 645篇 |
2009年 | 662篇 |
2008年 | 674篇 |
2007年 | 736篇 |
2006年 | 677篇 |
2005年 | 572篇 |
2004年 | 447篇 |
2003年 | 393篇 |
2002年 | 351篇 |
2001年 | 290篇 |
2000年 | 271篇 |
1999年 | 195篇 |
1998年 | 148篇 |
1997年 | 132篇 |
1996年 | 109篇 |
1995年 | 132篇 |
1994年 | 83篇 |
1993年 | 65篇 |
1992年 | 70篇 |
1991年 | 56篇 |
1990年 | 56篇 |
1989年 | 52篇 |
1988年 | 45篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1964年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
通过对发生腐蚀穿孔的BA-1104裂解炉对流段二次注汽过热炉管进行了宏观腐蚀形貌分析,对含裂纹部位进行了光学显微镜观察,断口进行扫描电镜观察以及对腐蚀产物的化学成分和金相组织分析,指出造成炉管腐蚀穿孔的决定性因素与操作温度及介质中存在的碱有关。进而提出了腐蚀控制与防范的措施,确保裂解炉的安全运行。 相似文献
122.
A methodology to improve the efficiency of stochastic methods applied to the optimization of chemical processes with a large number of equality constraints is presented. The methodology is based on two steps: (a) the optimization of the simulation step, which involves the optimum choice of design variables and subsystems to be simultaneously solved; (b) the optimization of the nonlinear programming (NLP) problem using stochastic methods. For the first step a flexible tool (SIMOP) is used, whereby different numerical procedures can be easily obtained, taking into account the problem formulation and specific characteristics, the need for specific initialization schemes and the efficient solution of systems of nonlinear equations. This methodology was applied to the optimization of a reactive distillation process for the production of ethylene glycol. Due to the complexity of the mathematical model, several different numerical procedures were generated, and their influence on the computational burden and on the reliability and accuracy of the optimization to reach the global optimum were studied. The results obtained suggest that in addition to the choice of design variables, the structure of subsystems associated to numerical procedures has a considerable impact on the performance of the optimizers. 相似文献
123.
J. Linares-Pérez R. Caballero-Águila I. García-Garrido 《International journal of systems science》2014,45(7):1548-1562
This paper addresses the optimal least-squares linear estimation problem for a class of discrete-time stochastic systems with random parameter matrices and correlated additive noises. The system presents the following main features: (1) one-step correlated and cross-correlated random parameter matrices in the observation equation are assumed; (2) the process and measurement noises are one-step autocorrelated and two-step cross-correlated. Using an innovation approach and these correlation assumptions, a recursive algorithm with a simple computational procedure is derived for the optimal linear filter. As a significant application of the proposed results, the optimal recursive filtering problem in multi-sensor systems with missing measurements and random delays can be addressed. Numerical simulation examples are used to demonstrate the feasibility of the proposed filtering algorithm, which is also compared with other filters that have been proposed. 相似文献
124.
We present ECOC-DRF, a framework where potential functions for Discriminative Random Fields are formulated as an ensemble of classifiers. We introduce the label trick, a technique to express transitions in the pairwise potential as meta-classes. This allows to independently learn any possible transition between labels without assuming any pre-defined model. The Error Correcting Output Codes matrix is used as ensemble framework for the combination of margin classifiers. We apply ECOC-DRF to a large set of classification problems, covering synthetic, natural and medical images for binary and multi-class cases, outperforming state-of-the art in almost all the experiments. 相似文献
125.
This paper presents a segment-based probabilistic approach to robustly recognize continuous sign language sentences. The recognition strategy is based on a two-layer conditional random field (CRF) model, where the lower layer processes the component channels and provides outputs to the upper layer for sign recognition. The continuously signed sentences are first segmented, and the sub-segments are labeled SIGN or ME (movement epenthesis) by a Bayesian network (BN) which fuses the outputs of independent CRF and support vector machine (SVM) classifiers. The sub-segments labeled as ME are discarded and the remaining SIGN sub-segments are merged and recognized by the two-layer CRF classifier; for this we have proposed a new algorithm based on the semi-Markov CRF decoding scheme. With eight signers, we obtained a recall rate of 95.7% and a precision of 96.6% for unseen samples from seen signers, and a recall rate of 86.6% and a precision of 89.9% for unseen signers. 相似文献
126.
This paper deals with a class of fuzzy stochastic differential equations (FSDEs) driven by a continuous local martingale under the Lipschitzian condition. Such equations can be useful in modeling hybrid systems, where the phenomena are simultaneously subjected to two kinds of uncertainties: randomness and fuzziness. The solutions of the FSDEs are the fuzzy stochastic processes, and their uniqueness is considered to be in a strong sense. Thus, the existence and uniqueness of solutions to the FSDEs under the Lipschitzian condition is first proven. Moreover, some asymptotic properties of the solutions to the FSDEs are investigated. Finally, an illustrating example on the interest term model is provided. 相似文献
127.
128.
A Monte Carlo method was used for a computer simulation of radiation-induced solid state polymerization. The propagation of polymer chains was simulated by means of self-avoiding random walks on a tetrahedral lattice. The initiation and termination of the chains were modelled by pseudorandom processes. The influence of conditions of the in-source process on the post-polymerization kinetics and on the degree of polymerization of the polymers was studied. 相似文献
129.
针对扫描的人脑组织MR图像边缘分辨率低、模糊性大的特点,本文提出了一种基于模糊Markov随机场和Gaussian曲线相结合的MR图像最佳阈值分割方法。该方法通过对图像的像素邻域属性的统计将模糊论引入其中,建立模糊Markov随机场,并利用Gaussian曲线对二维直方图最佳一维投影进行拟合,确定出图像中各脑组织的二维阈值点,在二维直方图上实现对脑组织的分割。通过实验表明,本算法能够有效提高脑组织的分辨率,对噪声的鲁棒性、结果区域的连通性相对于一维Otsu和二维Otsu算法都有了很大的提高。 相似文献
130.
李志萍 《电脑编程技巧与维护》2014,(4):6-8,17
运用随机游走模型提出了一种基于维基百科的语义相关度的计算方法。维基百科中包含了丰富的链接结构,这些链接结构一定程度上能够反应词条之间概念上的相关性,以内容链接和外部链接关系来计算基于维基百科的语义相关度,并在WS-353数据集上进行了实验,取得了较好的准确性。 相似文献