全文获取类型
收费全文 | 49093篇 |
免费 | 4547篇 |
国内免费 | 2568篇 |
专业分类
电工技术 | 3053篇 |
技术理论 | 6篇 |
综合类 | 3580篇 |
化学工业 | 7670篇 |
金属工艺 | 3281篇 |
机械仪表 | 3310篇 |
建筑科学 | 3895篇 |
矿业工程 | 1619篇 |
能源动力 | 1446篇 |
轻工业 | 3666篇 |
水利工程 | 1055篇 |
石油天然气 | 2772篇 |
武器工业 | 525篇 |
无线电 | 5381篇 |
一般工业技术 | 5228篇 |
冶金工业 | 2425篇 |
原子能技术 | 687篇 |
自动化技术 | 6609篇 |
出版年
2024年 | 221篇 |
2023年 | 816篇 |
2022年 | 1534篇 |
2021年 | 2128篇 |
2020年 | 1624篇 |
2019年 | 1337篇 |
2018年 | 1509篇 |
2017年 | 1658篇 |
2016年 | 1485篇 |
2015年 | 2136篇 |
2014年 | 2541篇 |
2013年 | 3161篇 |
2012年 | 3395篇 |
2011年 | 3570篇 |
2010年 | 3233篇 |
2009年 | 3110篇 |
2008年 | 3131篇 |
2007年 | 2950篇 |
2006年 | 2842篇 |
2005年 | 2418篇 |
2004年 | 1642篇 |
2003年 | 1381篇 |
2002年 | 1392篇 |
2001年 | 1133篇 |
2000年 | 1046篇 |
1999年 | 1007篇 |
1998年 | 754篇 |
1997年 | 567篇 |
1996年 | 532篇 |
1995年 | 443篇 |
1994年 | 357篇 |
1993年 | 237篇 |
1992年 | 205篇 |
1991年 | 144篇 |
1990年 | 124篇 |
1989年 | 74篇 |
1988年 | 87篇 |
1987年 | 52篇 |
1986年 | 39篇 |
1985年 | 36篇 |
1984年 | 31篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed using comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) on a series of agonists of thyroid hormone receptor beta (TRbeta), which may lead to safe therapies for non-thyroid disorders while avoiding the cardiac side effects. The reasonable q(2) (cross-validated) values 0.600 and 0.616 and non-cross-validated r(2) values of 0.974 and 0.974 were obtained for CoMFA and CoMSIA models for the training set compounds, respectively. The predictive ability of two models was validated using a test set of 12 molecules which gave predictive correlation coefficients (r(pred)(2)) of 0.688 and 0.674, respectively. The Lamarckian Genetic Algorithm (LGA) of AutoDock 4.0 was employed to explore the binding mode of the compound at the active site of TRbeta. The results not only lead to a better understanding of interactions between these agonists and the thyroid hormone receptor beta but also can provide us some useful information about the influence of structures on the activity which will be very useful for designing some new agonist with desired activity. 相似文献
62.
63.
ProxyServer中Cache的管理和使用 总被引:1,自引:0,他引:1
使用Cache可以减少Brower的等待时间和降低代理服务器和Internet的通信量,本文主要介绍了Proxy对Cache管理和使用。 相似文献
64.
Railway Engineering Science - Large eddy simulation is performed to study three-dimensional wave–current interaction with a square cylinder at different Reynolds numbers, ranging from 1,000... 相似文献
65.
With the development of cloud environments serving as a unified infrastructure, the resource management and energy consumption issues become more important in the operations of such systems. In this paper, we investigate adaptive model-free approaches for resource allocation and energy management under time-varying workloads and heterogeneous multi-tier applications. Specifically, we make use of measurable metrics, including throughput, rejection amount, queuing state, and so on, to design resource adjustment schemes and to make control decisions adaptively. The ultimate objective is to guarantee the summarized revenue of the resource provider while saving energy and operational costs. To validate the effectiveness, performance evaluation experiments are performed in a simulated environment, with realistic workloads considered. Results show that with the combination of long-term adaptation and short-term adaptation, the fluctuation of unpredictable workloads can be captured, and thus the total revenue can be preserved while balancing the power consumption as needed. Furthermore, the proposed approach can achieve better effect and efficiency than the model-based approaches in dealing with real-world workloads. 相似文献
66.
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
67.
The work presented in this paper focuses on improving coal loading performance of shear drum.Employing the similarity theory,we carried out a dimensional analysis of the correlation parameters which in... 相似文献
68.
69.
堵祖荫 《化学反应工程与工艺》1993,9(4):451-455
对于含有众多复什碳氢化合物的裂解汽油、裂解柴油和裂解燃料油等宽馏分以及氢、轻烃、大量水分的裂解气,采用虚拟组分以减少组分总数、用惰性气体描述水在烃类中的相行为,以物流混合和闪蒸过程组成一个闪蒸平衡级,并以逐级闪蒸计算来描述乙烯装置的裂解气分馏塔。 相似文献
70.
全电动注塑机的特点及应用领域 总被引:2,自引:1,他引:2
重点分析了全电动注塑机与全液压注塑机的不同之处,简单地概述了国内塑料工业发展落后的现状以及把我国建成注塑机生产强国的突破口。详细介绍了全电动注塑机的应用领域,并展望了全电动注塑机的发展。 相似文献