全文获取类型
收费全文 | 12056篇 |
免费 | 1576篇 |
国内免费 | 796篇 |
专业分类
电工技术 | 1043篇 |
综合类 | 814篇 |
化学工业 | 2036篇 |
金属工艺 | 654篇 |
机械仪表 | 701篇 |
建筑科学 | 926篇 |
矿业工程 | 382篇 |
能源动力 | 381篇 |
轻工业 | 1088篇 |
水利工程 | 336篇 |
石油天然气 | 519篇 |
武器工业 | 131篇 |
无线电 | 1615篇 |
一般工业技术 | 1580篇 |
冶金工业 | 463篇 |
原子能技术 | 154篇 |
自动化技术 | 1605篇 |
出版年
2024年 | 109篇 |
2023年 | 373篇 |
2022年 | 704篇 |
2021年 | 858篇 |
2020年 | 656篇 |
2019年 | 512篇 |
2018年 | 507篇 |
2017年 | 562篇 |
2016年 | 493篇 |
2015年 | 644篇 |
2014年 | 738篇 |
2013年 | 862篇 |
2012年 | 853篇 |
2011年 | 841篇 |
2010年 | 714篇 |
2009年 | 674篇 |
2008年 | 610篇 |
2007年 | 578篇 |
2006年 | 519篇 |
2005年 | 450篇 |
2004年 | 303篇 |
2003年 | 260篇 |
2002年 | 290篇 |
2001年 | 240篇 |
2000年 | 165篇 |
1999年 | 149篇 |
1998年 | 149篇 |
1997年 | 100篇 |
1996年 | 104篇 |
1995年 | 65篇 |
1994年 | 61篇 |
1993年 | 46篇 |
1992年 | 31篇 |
1991年 | 33篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1976年 | 5篇 |
1969年 | 3篇 |
1959年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
In this paper, the problem of delay-dependent robust H
∞ control for uncertain stochastic systems with state and input delays is investigated. The time delays are assumed to be bounded
and time varying and the uncertainties are assumed to be norm bounded. By using the Lyapunov functional method, a new delay-dependent
robust H
∞ control scheme is presented in terms of linear matrix inequalities (LMIs). Some numerical examples are given to illustrate
the effectiveness of the proposed approach.
This work is partially supported by the Natural Science Foundation of China (60674055, 60774047), and the Taishan Scholar
Programme of Shandong Province.
An erratum to this article can be found at 相似文献
42.
43.
为深入探究中风化花岗岩中嵌岩桩的竖向抗压承载特性,对12根嵌岩桩进行了单桩竖向抗压静载原位试验与ABAQUS有限元数值模拟,通过多种方法对嵌岩单桩极限承载力进行评价,明确中风化花岗岩中嵌岩桩竖向抗压承载性状。研究表明:12根中风化花岗岩中嵌岩桩并非表现出完全端承桩,而是呈摩擦型桩或摩擦端承桩的性状;中风化花岗岩地基中的嵌岩桩竖向抗压极限承载力较高,桩顶沉降小,满足工程对基础的承载要求;有限元模拟荷载-沉降曲线与实测荷载-沉降曲线走势吻合度较高,桩顶沉降误差较小;本试验条件下,桩端阻力占桩顶荷载的56.9%,桩侧摩阻力占比为43.1%,桩侧摩阻力在荷载传递过程中发挥较充分;有限元模拟得到的单桩极限承载力与指数函数模型的预测结果较为吻合,可用于嵌岩桩单桩竖向抗压极限承载力的预测,以及嵌岩桩承载性状和荷载传递规律的分析。 相似文献
44.
Weikai Ding Yousef Sultan Shumei Li Wenjun Wen Bangjun Zhang Yiyi Feng Junguo Ma Xiaoyu Li 《International journal of molecular sciences》2022,23(11)
Previous studies have indicated that the harmful heavy metal lead (Pb) contamination in aquatic systems has caused intelligence development disorders and nervous system function abnormalities in juveniles due to the increased permeability of the blood–brain barrier. Ionic liquids (ILs) are considered “green” organic solvents that can replace traditional organic solvents. Studies have found the presence of ILs in soil and water due to chemical applications or unintentional leakage. Therefore, what would happen if Pb interacted with ILs in a body of water? Could ILs enable Pb to more easily cross the blood–brain barrier? Therefore, we examined the combined exposure of Pb and ILs in common carp at low concentration (18.3 mg L−1 of Pb(CH3COO)2•3 H2O and 11 mg L−1 of the IL 1-methyl-3-octylimidazolium chloride, 5% of their LC50) for 28 days in the present study. The result of a neurobehavioral assay showed that chronic exposure of lead at lower concentrations significantly altered fish movement and neurobehaviors, indicating that lead exposure caused neurotoxicity in the carp. Increases in the neurotransmitter dopamine levels and injuries in the fish brain accounted for neurobehavioral abnormalities induced by lead exposure. Moreover, we also found that lead could easily cross the blood–brain barrier and caused significant bioaccumulation in the brain. Particularly, our study indicated that the ionic liquid could not synergistically promote blood–brain barrier permeability and hence failed to increase the absorption of lead in the fish brain, suggesting that the combined exposure of lead and ILs was not a synergistic effect but antagonism to the neurotoxicity. The results of this study suggested that ILs could recede the Pb induced neurotoxicity in fish. 相似文献
45.
46.
Kun Zhu Chun Wu Xiaoyu Peng Xuantao Ji Siyuan Luo Yuchen Liu Xiaodong Wang 《International journal of molecular sciences》2022,23(11)
Monte Carlo simulations can quantify various types of DNA damage to evaluate the biological effects of ionizing radiation at the nanometer scale. This work presents a study simulating the DNA target response after proton irradiation. A chromatin fiber model and new physics constructors with the ELastic Scattering of Electrons and Positrons by neutral Atoms (ELSEPA) model were used to describe the DNA geometry and the physical stage of water radiolysis with the Geant4-DNA toolkit, respectively. Three key parameters (the energy threshold model for strand breaks, the physics model and the maximum distance to distinguish DSB clusters) of scoring DNA damage were studied to investigate the impact on the uncertainties of DNA damage. On the basis of comparison of our results with experimental data and published findings, we were able to accurately predict the yield of various types of DNA damage. Our results indicated that the difference in physics constructor can cause up to 56.4% in the DNA double-strand break (DSB) yields. The DSB yields were quite sensitive to the energy threshold for strand breaks (SB) and the maximum distance to classify the DSB clusters, which were even more than 100 times and four times than the default configurations, respectively. 相似文献
47.
文章介绍了如何通过A/D转化把录井参数波形转化为数字资料,并采用模式识别的方法自动识别油气层。准确地识别油层、油水同层、水层、干层等。将BP神经网络的识别方法应用于石油勘探,相比其他解释方法更科学。利用三层的前馈阶层网络对油气层自动识别,不仅缩减了工作量,而且还能精确了解解释结果。一个好的识别模型可以轻易地达到事半功倍的效果,实例证明利用BP神经网络判别油气层效果是令人满意的技术。 相似文献
48.
以HSK方程为基础,提出了一种利用岩心核磁共振实验数据计算阳离子交换容量Qv的方法.该方法与湿式化学阳离子交换容量分析法相比存在一定的误差.12块岩样数据显示,相对误差范围12%~95%,平均相对误差为55%.分别从溶液矿化度、核磁共振总孔隙度以及黏土束缚水T2截止值等参数出发,开展了核磁共振确定阳离子交换容量影响因素分析研究.黏土束缚水T2截止值是影响核磁共振计算阳离子交换容量的关键参数,黏土束缚水T2截止值是可变的,而不是传统意义上的3 ms.基于岩心核磁共振准确求取阳离子交换容量的前提是准确求取黏土束缚水T2截止值. 相似文献
49.
50.
直流电缆附件是直流输电系统的薄弱环节,为研究非线性电导对极性反转电压下电缆附件硅橡胶绝缘电荷积聚特性的影响,通过添加SiC颗粒制备具有非线性电导的硅橡胶复合材料试样,利用三电极法和表面电位测量系统获得试样的电导率和表面电荷特性。实验结果表明:由于试样中SiC晶粒的晶格振动引起载流子晶格散射,高温会造成试样电导率降低;试样表面电荷平面分布特性表明,电晕电压极性反转后,平板试样内部残留的原极性电荷与表面的异极性电荷提高了局部电场强度,使试样的电导率升高,加速了表面电荷向试样内部迁移和异极性电荷中和过程,抑制了表面电荷的积聚。 相似文献