首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2142篇
  免费   95篇
  国内免费   15篇
电工技术   27篇
综合类   6篇
化学工业   522篇
金属工艺   72篇
机械仪表   62篇
建筑科学   36篇
矿业工程   2篇
能源动力   126篇
轻工业   85篇
水利工程   12篇
石油天然气   7篇
无线电   298篇
一般工业技术   523篇
冶金工业   166篇
原子能技术   15篇
自动化技术   293篇
  2023年   37篇
  2022年   71篇
  2021年   77篇
  2020年   64篇
  2019年   65篇
  2018年   73篇
  2017年   76篇
  2016年   81篇
  2015年   51篇
  2014年   78篇
  2013年   168篇
  2012年   103篇
  2011年   118篇
  2010年   97篇
  2009年   90篇
  2008年   84篇
  2007年   77篇
  2006年   73篇
  2005年   42篇
  2004年   46篇
  2003年   37篇
  2002年   40篇
  2001年   38篇
  2000年   24篇
  1999年   26篇
  1998年   43篇
  1997年   45篇
  1996年   32篇
  1995年   24篇
  1994年   32篇
  1993年   29篇
  1992年   16篇
  1991年   20篇
  1990年   10篇
  1989年   8篇
  1988年   9篇
  1987年   11篇
  1986年   19篇
  1985年   19篇
  1984年   25篇
  1983年   16篇
  1982年   16篇
  1981年   22篇
  1980年   17篇
  1979年   17篇
  1978年   16篇
  1977年   16篇
  1976年   14篇
  1975年   8篇
  1972年   5篇
排序方式: 共有2252条查询结果,搜索用时 15 毫秒
101.
Journal of Polymer Research - In this study, we prepared graphene oxide-based styrene/acrylic elastomeric disks (GSAE) from sugarcane bagasse/ferrocene (GO) and styrene/acrylic emulsion (SAE) to...  相似文献   
102.
Silicon - In this paper, for the first time, the performance evaluation of negative capacitance single-active layer double-gate (NC-SALDG) TFT is presented. In the proposed NC-SALDG TFT, amorphous...  相似文献   
103.
In this study, a porous silk fibroin (SF) scaffold was modified with soluble eggshell membrane protein (SEP) with the aim of improving the cell affinity properties of the scaffold for tissue regeneration. The pore size and porosity of the prepared scaffold were in the ranges 200–300 μm and 85–90%, respectively. The existence of SEP on the scaffold surface and the structural and thermal stability were confirmed by energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The cell culture study indicated a significant improvement in the cell adhesion and proliferation of mesenchymal stem cells (MSCs) on the SF scaffold modified with SEP. The cytocompatibility of the SEP‐conjugated SF scaffold was confirmed by a 3‐(4,5‐dimethyltriazol‐2‐y1)‐2,5‐diphenyl tetrazolium assay. Thus, this study demonstrated that the biomimic properties of the scaffold could be enhanced by surface modification with SEP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40138.  相似文献   
104.
105.
The connectivity of wireless networks is commonly analyzed using static geometric graphs. However, with half-duplex radios and due to interference, static or instantaneous connectivity cannot be achieved. It is not necessary, either, since packets take multiple time slots to propagate through the network. For example, if a packet traverses a link in one time slot, it is irrelevant if the next link is available in that time slot also, but it is relevant if the next hop exists in the next time slot. To account for half-duplex constraints and the dynamic changes in the transmitting set of nodes due to MAC scheduling and traffic loads, we introduce a random multi-digraph that captures the evolution of the network connectivity in a dynamic fashion. To obtain concrete results, we focus on Poisson networks, where transmitters form a Poisson point process on the plane at all time instants. We first provide analytical results for the degree distribution of the graph and derive the distributional properties of the end-to-end connection delay using techniques from first-passage percolation and epidemic processes. Next, we prove that under some assumptions, the delay scales linearly with the source–destination distance even in the presence of interference. We also provide simulation results in support of the theoretical results.  相似文献   
106.
De-duplication using biometrics has gained much attention from research communities as it provides a unique identity for each and every individual among the large population.De-duplication is the process of removing the instances of multiple enrollments by the same person using the person’s biometric data.An important issue in the large-scale de-duplication applications is the speed of matching and the accuracy of the matching because the number of persons to be enrolled runs into millions.This paper presents an efficient method to improve the accuracy of fingerprint de-duplication in de-centralized manner.De-duplication accuracy decreases because of the noise present in the data,which would cause improper slap fingerprint segmentation.In this paper,an attempt is made to remove the noise present in the data by using binarization of slap fingerprint images and region labeling of desired regions with 8-adjacency neighborhood.The distinct feature of this technique is to remove the noise present in the data for an accurate slap fingerprint segmentation and improve the de-duplication accuracy.Experimental results demonstrate that the fingerprint segmentation rate and de-duplication accuracy are improved significantly.  相似文献   
107.
In this paper a fuzzy interactive method is proposed for efficient management of multipurpose multireservoir problems. The proposed method provides an option to decision maker (DM) to work in an interactive manner to achieve the conflicting objectives as close to their desired values as is practically feasible. In each iteration, fuzzy membership functions of various objectives are framed and combined into a single objective using the product operator. The single objective nonlinear optimization model thus framed in each iteration is numerically solved using genetic algorithm. The solution provides the values of the objectives which can be actually achieved keeping in view their aspired values as provided by DM. At the end of each iteration, DM has the option to modify the aspired values of one or more objectives keeping in view the results obtained by the algorithm thus far. The algorithm is stopped when DM feels satisfied with the results. The working of the proposed method has been demonstrated on the mathematical model of a realistic multipurpose multireservoir system taken from literature.  相似文献   
108.
In the present investigation, Cu-0.6Cr-0.005Zr-0.0045Ti alloy was subjected to different heat treatment and thermomechanical treatment (TMT) to simulate the conditions experienced during brazing and forming, respectively. Grain coarsening was observed in the samples subjected to heat treatment, and grain refinement was observed in the samples subjected to TMT. Tensile tests conducted with these samples at room temperature and 600 °C have shown that Cu-Cr-Zr-Ti alloy was susceptible to dynamic embrittlement (DE). However, the observation was limited to coarse-grained samples (280-350 μm) at 600 °C. On the other hand, the fine-grained samples (20-40 μm) showed good ductility. Electron microscopy studies conducted on the tensile-tested specimens prone to DE indicated the presence of sulfur on the fractured surface and intergranular segregation of sulfur. Therefore, it can be inferred from the results that DE due to sulfur can occur in Cu-Cr-Zr-Ti alloy at elevated temperature for coarse-grained samples.  相似文献   
109.
Editor's note:Standardized design and test practices enable automation. This article describes a methodology and corresponding tool set that combines automated support for IEEE Std 1500 and test data compression in one.—Erik Jan Marinissen, IMEC  相似文献   
110.
The nucleon optical model is widely used to calculate the elastic scattering cross-sections and polarizations. The only requirement, in using the optical model for a reliable prediction of the nuclear data is the unique set of optical model parameters (OMP). The uncertainties in the OMP lead to uncertainties in calculated cross-sections and thus the deficiency in the model itself. To our knowledge, there is no technique, to estimate the limits of variation of OMP to establish good fits with consequent reduction of optical model deficiency between these limits. In this paper, we propose D-optimal criterion and the technique of Determinant Inequalities developed by us to simulate OMP with reduced optical model deficiency. Our technique enables one to simulate the limits of variation of the OMP with the existing covariance data. The simulation of these limits would aid to establish good fits among the OMP. Further, the variation in the range of deficiency in the optical model can be ascertained well in advance. We demonstrate the utility of our technique to the OMP of 239Pu.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号