全文获取类型
收费全文 | 27274篇 |
免费 | 1779篇 |
国内免费 | 909篇 |
专业分类
电工技术 | 1587篇 |
技术理论 | 5篇 |
综合类 | 3379篇 |
化学工业 | 4014篇 |
金属工艺 | 749篇 |
机械仪表 | 1740篇 |
建筑科学 | 3293篇 |
矿业工程 | 875篇 |
能源动力 | 679篇 |
轻工业 | 1670篇 |
水利工程 | 517篇 |
石油天然气 | 875篇 |
武器工业 | 236篇 |
无线电 | 1879篇 |
一般工业技术 | 3791篇 |
冶金工业 | 705篇 |
原子能技术 | 215篇 |
自动化技术 | 3753篇 |
出版年
2024年 | 82篇 |
2023年 | 331篇 |
2022年 | 639篇 |
2021年 | 866篇 |
2020年 | 631篇 |
2019年 | 554篇 |
2018年 | 515篇 |
2017年 | 669篇 |
2016年 | 755篇 |
2015年 | 788篇 |
2014年 | 1661篇 |
2013年 | 1789篇 |
2012年 | 2155篇 |
2011年 | 1791篇 |
2010年 | 1595篇 |
2009年 | 1733篇 |
2008年 | 1580篇 |
2007年 | 1638篇 |
2006年 | 1427篇 |
2005年 | 1199篇 |
2004年 | 1002篇 |
2003年 | 905篇 |
2002年 | 747篇 |
2001年 | 642篇 |
2000年 | 511篇 |
1999年 | 384篇 |
1998年 | 304篇 |
1997年 | 226篇 |
1996年 | 1183篇 |
1995年 | 603篇 |
1994年 | 421篇 |
1993年 | 72篇 |
1992年 | 64篇 |
1991年 | 80篇 |
1990年 | 64篇 |
1989年 | 60篇 |
1988年 | 47篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 39篇 |
1984年 | 46篇 |
1983年 | 23篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
11.
The n-type thermoelectric Bi1.9Lu0.1Te3 was prepared by microwave-solvothermal method and spark plasma sintering. The magnetic field and temperature dependences of transverse magnetoresistance measured within temperature 2–200 K interval allow finding the peculiarities characteristic for strongly disordered and inhomogeneous semiconductors. The first peculiarity is due to appearance of linear-in-magnetic field contribution to the total magnetoresistance reflected in a crossover from quadratic magnetoresistance at low magnetic fields to linear magnetoresistance at high magnetic fields. The linear magnetoresistance can result from the Hall resistance picked up from macroscopically distorted current paths due to local variations in stoichiometry of the compound studied. The second peculiarity is that both linear magnetoresistance magnitude and crossover field are functions of carrier mobility which is in agreement with the Parish and Littlewood model developed for disordered and inhomogeneous semiconductors. An increase in the mobility due to a decrease in temperature is accompanied by an increase in the magnetoresistance magnitude and a decrease in the crossover field. Finally, the third peculiarity is related to the remarkable deviation of the total magnetoresistance measured at various temperatures from the Kohler's rule. Presence of strong inhomogeneity and disorder in the Bi1.9Lu0.1Te3 structure concluded from the magnetoresistance peculiarities can be responsible for the remarkable reduction in the total thermal conductivity of this compound. 相似文献
12.
13.
14.
This article reviews the four innovation governance approaches (the precautionary principle, responsible innovation, permissionless innovation, and the innovation principle), including definitions, important attributes, and weaknesses found in each approach, and when utilizing an affinity diagram as a tool of analysis, identifies their distinctive characteristics and common relationships. A discussion section summarizes the paper’s findings and offers insights into where there is common relationships for further possible convergence between two innovation governance approaches – responsible innovation and permissionless innovation – that conceptually share substantially more in common than they contrast with each other. For addressing this challenge, the study recommends the following policy proposals: embrace artificial intelligence/machine learning/data analytics for risk management and regulatory adaptability; consider “soft law”as an option to public regulation; and substitute corporate citizenship for corporate social responsibility. 相似文献
15.
As a symbol of sharing economy, ride-hailing services have spread to Asia, where various forms of services have been established according to the existing socio-technical regimes, including legal, policy, and environmental concerns. China, in particular, has accepted ride-hailing services by revising existing institutions. This study analyzes China’s acceptance of ride-hailing services in the socio-technical system context set up for legacy services. Simulation modeling, combined with transition theory and an agent-based model, is used to analyze the data. This study calculates consumer disutility based on mobility market share, reflecting consumer preference, and predicts the sustainability of ride-hailing services. The simulation results conclude that legalization and socio-technical context are of importance for sustainable mobility. 相似文献
16.
Zhijiang Li Yingping Zheng Liqin Cao Lei Jiao Yanfei Zhong Caiyi Zhang 《Color research and application》2020,45(4):656-670
Image color clustering is a basic technique in image processing and computer vision, which is often applied in image segmentation, color transfer, contrast enhancement, object detection, skin color capture, and so forth. Various clustering algorithms have been employed for image color clustering in recent years. However, most of the algorithms require a large amount of memory or a predetermined number of clusters. In addition, some of the existing algorithms are sensitive to the parameter configurations. In order to tackle the above problems, we propose an image color clustering method named Student's t-based density peaks clustering with superpixel segmentation (tDPCSS), which can automatically obtain clustering results, without requiring a large amount of memory, and is not dependent on the parameters of the algorithm or the number of clusters. In tDPCSS, superpixels are obtained based on automatic and constrained simple non-iterative clustering, to automatically decrease the image data volume. A Student's t kernel function and a cluster center selection method are adopted to eliminate the dependence of the density peak clustering on parameters and the number of clusters, respectively. The experiments undertaken in this study confirmed that the proposed approach outperforms k-means, fuzzy c-means, mean-shift clustering, and density peak clustering with superpixel segmentation in the accuracy of the cluster centers and the validity of the clustering results. 相似文献
17.
The main purpose of this paper is to survey some recent progresses on control theory for stochastic distributed parameter systems, i.e., systems governed by stochastic differential equations in infinite dimensions, typically by stochastic partial differential equations. We will explain the new phenomenon and difficulties in the study of controllability and optimal control problems for one dimensional stochastic parabolic equations and stochastic hyperbolic equations. In particular, we shall see that both the formulation of corresponding stochastic control problems and the tools to solve them may differ considerably from their deterministic/finite-dimensional counterparts. More importantly, one has to develop new tools, say, the stochastic transposition method introduced in our previous works, to solve some problems in this field. 相似文献
18.
Qilin Liu Feng Ding 《International Journal of Adaptive Control and Signal Processing》2021,35(10):1970-1989
The identification of the Hammerstein–Wiener (H-W) systems based on the nonuniform input–output dataset remains a challenging problem. This article studies the identification problem of a periodically nonuniformly sampled-data H-W system. In addition, the product terms of the parameters in the H-W system are inevitable. In order to solve the problem, the key-term separation is applied and two algorithms are proposed. One is the key-term-based forgetting factor stochastic gradient (KT-FFSG) algorithm based on the gradient search. The other is the key-term-based hierarchical forgetting factor stochastic gradient (KT-HFFSG) algorithm. Compared with the KT-FFSG algorithm, the KT-HFFSG algorithm gives more accurate estimates. The simulation results indicate that the proposed algorithms are effective. 相似文献
19.
Yumio Yato 《Journal of Nuclear Science and Technology》2019,56(4):311-316
When UF6 is handled in leak tight system, the amount of uranium compound formed on the surface of containers, valves, and others in UF6 handling facilities is not so significant for a short term that special attention has not been given to this problem. The present work was done to throw some more light on this problem based on the recent experiment. We discuss the possibility that the intermolecular transfer of a fluorine atom from UF6 to UF5 may participate in the formation of uranium compound. The discussion includes also the unique features contained in the experimental result, the reaction processes assumed in this problem, and the derivation of a rate equation for expressing the deposition of uranium compound. Furthermore, we propose a new method for determining nonlinear parameters included in a governing differential equation having two variables for expressing the deposition of uranium compound from experimental raw data. 相似文献
20.