全文获取类型
收费全文 | 64353篇 |
免费 | 6462篇 |
国内免费 | 3652篇 |
专业分类
电工技术 | 4632篇 |
技术理论 | 2篇 |
综合类 | 4940篇 |
化学工业 | 10046篇 |
金属工艺 | 3793篇 |
机械仪表 | 4556篇 |
建筑科学 | 5007篇 |
矿业工程 | 2262篇 |
能源动力 | 1714篇 |
轻工业 | 5235篇 |
水利工程 | 1413篇 |
石油天然气 | 2982篇 |
武器工业 | 637篇 |
无线电 | 7659篇 |
一般工业技术 | 6795篇 |
冶金工业 | 2481篇 |
原子能技术 | 793篇 |
自动化技术 | 9520篇 |
出版年
2024年 | 332篇 |
2023年 | 1120篇 |
2022年 | 2395篇 |
2021年 | 3158篇 |
2020年 | 2504篇 |
2019年 | 1954篇 |
2018年 | 2151篇 |
2017年 | 2393篇 |
2016年 | 2241篇 |
2015年 | 3361篇 |
2014年 | 4077篇 |
2013年 | 4517篇 |
2012年 | 5017篇 |
2011年 | 5336篇 |
2010年 | 4624篇 |
2009年 | 4254篇 |
2008年 | 4063篇 |
2007年 | 3677篇 |
2006年 | 3358篇 |
2005年 | 2597篇 |
2004年 | 1936篇 |
2003年 | 1534篇 |
2002年 | 1632篇 |
2001年 | 1352篇 |
2000年 | 1020篇 |
1999年 | 907篇 |
1998年 | 605篇 |
1997年 | 469篇 |
1996年 | 450篇 |
1995年 | 368篇 |
1994年 | 267篇 |
1993年 | 209篇 |
1992年 | 138篇 |
1991年 | 98篇 |
1990年 | 81篇 |
1989年 | 88篇 |
1988年 | 51篇 |
1987年 | 30篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1977年 | 1篇 |
1966年 | 1篇 |
1959年 | 6篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
This paper proposes an evolutionary accelerated computational level set algorithm for structure topology optimization. It integrates the merits of evolutionary structure optimization (ESO) and level set method (LSM). Traditional LSM algorithm is largely dependent on the initial guess topology. The proposed method combines the merits of ESO techniques with those of LSM algorithm, while allowing new holes to be automatically generated in low strain energy within the nodal neighboring region during optimization. The validity and robustness of the new algorithm are supported by some widely used benchmark examples in topology optimization. Numerical computations show that optimization convergence is accelerated effectively. 相似文献
62.
63.
采用DCS的鼓风炉上料控制系统 总被引:3,自引:0,他引:3
介绍由欧陆NETWORK6000 DCS组成的鼓风炉自动控制上料系统的结构和功能。详述了组态软件及特点,上料系统软件编制等。 相似文献
64.
JI Fei 《数字社区&智能家居》2008,(34)
面向对象分析与设计,涉及的内容新、实践性强。文章着眼于高等职业院校,分析了课程体系、教学目标,以类模型图为例,阐述了抽象-实现-建模的三步教学法。 相似文献
65.
66.
This paper presents a novel ranking framework for content-based multimedia information retrieval (CBMIR). The framework introduces relevance features and a new ranking scheme. Each relevance feature measures the relevance of an instance with respect to a profile of the targeted multimedia database. We show that the task of CBMIR can be done more effectively using the relevance features than the original features. Furthermore, additional performance gain is achieved by incorporating our new ranking scheme which modifies instance rankings based on the weighted average of relevance feature values. Experiments on image and music databases validate the efficacy and efficiency of the proposed framework. 相似文献
67.
Due to the nature of distribution and self-organization, mobile ad hoc networks rely on cooperation between nodes to transfer information. One of the key factors to ensure high communication quality is an efficient assessment scheme for risks and trust of choosing next potential cooperative nodes. Trust model, an abstract psychological cognitive process, is one of the most complex concepts in social relationships, involving factors such as assumptions, expectations and behaviors. All of the above make it difficult to quantify and forecast trust accurately. In this paper, based on the theories of fuzzy recognition with feedback, SCGM(1, 1) model and Markov chain, we present a pattern of prediction making. The analysis and experimental computation show that this scheme is efficient in trust prediction for ad hoc networks. 相似文献
68.
This paper presents an integration technology for RF passives using benzocyclobutene (BCB)/metal multilayer interconnection
for system-in-package applications. This technology has been specially developed for RF subsystem packages in which a thick
polymer, BCB (more than 15 μm thick), is adopted as dielectric with lossy silicon as substrate for its excellent characteristics.
Both dry-etch BCB and photosensitive BCB are applied in this work, and their processes are briefly introduced and compared.
An RF power divider, an MIM capacitor, different types of RF inductors as well as a coupled microstrip based band-pass filter
are fabricated and measured at wafer level. The results show good electrical performances, and accordingly the passives are
well applicable in RF band. Moreover, the subsystem models including monolithic chips connected with passives are presented. 相似文献
69.
为满足实验室单克隆抗体的制备研究,本实验特对实验室常用的制备单抗的模拟抗原(Ac-NK16-Ahx-3)进行ELISA间接法检测,进而建立一种高效的检测方法。通过对不同稀释度待测抗体的免疫吸附测定,检测出它的最终灵敏度为0.078mg/mL,最佳二抗稀释倍数为300倍,其最佳拟合曲线为y=-0.0732x+0.6875,R2=0.8619。并且,通过统计学方法进行统计分析,确定出各实验组的相关性及变异系数,从而排除实验中的操作误差,最终可确定最佳的实验条件,并保证实验的准确性。 相似文献
70.
This paper deals with the theoretical prediction of global buckling loads for carbon fiber composite pyramidal truss core sandwich columns. Different from thin plate structures, transverse shear effect can not be neglected for sandwich structures. In addition, the attributes of the laminated face sheets are considered in the present paper. A zig-zag displacement approximation is made. Based on the principle of minimum potential energy, equilibrium equations and boundary conditions are derived via the variational method. The critical buckling loads under various boundary conditions are presented. In order to validate the reasonableness of the equivalent-core method, the strain energies stored in the actual discrete truss members and the equivalent continuous homogenous core layer are calculated respectively and compared, and a good agreement is obtained. The proposed analytical method is verified by comparing with the published theoretical predictions and experimental results. 相似文献