全文获取类型
收费全文 | 15217篇 |
免费 | 1521篇 |
国内免费 | 1198篇 |
专业分类
电工技术 | 1178篇 |
综合类 | 1287篇 |
化学工业 | 1881篇 |
金属工艺 | 1016篇 |
机械仪表 | 718篇 |
建筑科学 | 1165篇 |
矿业工程 | 596篇 |
能源动力 | 725篇 |
轻工业 | 721篇 |
水利工程 | 361篇 |
石油天然气 | 2543篇 |
武器工业 | 87篇 |
无线电 | 1289篇 |
一般工业技术 | 1537篇 |
冶金工业 | 685篇 |
原子能技术 | 279篇 |
自动化技术 | 1868篇 |
出版年
2024年 | 47篇 |
2023年 | 218篇 |
2022年 | 422篇 |
2021年 | 472篇 |
2020年 | 462篇 |
2019年 | 441篇 |
2018年 | 399篇 |
2017年 | 450篇 |
2016年 | 526篇 |
2015年 | 557篇 |
2014年 | 775篇 |
2013年 | 950篇 |
2012年 | 1034篇 |
2011年 | 1243篇 |
2010年 | 906篇 |
2009年 | 907篇 |
2008年 | 819篇 |
2007年 | 931篇 |
2006年 | 940篇 |
2005年 | 833篇 |
2004年 | 715篇 |
2003年 | 555篇 |
2002年 | 521篇 |
2001年 | 407篇 |
2000年 | 346篇 |
1999年 | 317篇 |
1998年 | 251篇 |
1997年 | 237篇 |
1996年 | 184篇 |
1995年 | 190篇 |
1994年 | 182篇 |
1993年 | 172篇 |
1992年 | 121篇 |
1991年 | 77篇 |
1990年 | 71篇 |
1989年 | 59篇 |
1988年 | 47篇 |
1987年 | 29篇 |
1986年 | 32篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1960年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
为研究消费者的潜在需求,探讨了消费者的个性与产品特性之间的关系,建立了一种能够解释消费者基本行为原因的方法.对特性记录评估及诊断理论体系进行了阐述,以可视电话为例,分析了制造方、供应方和接受方3类用户之间的有效评估偏差及其产生的原因,得出了对可视电话感性评价的数据,验证了特性记录评估及诊断理论体系的有效性. 相似文献
992.
993.
Although many field investigations into pipe-jacking installation have been reported within the literature, there are few reports on the rebar stress in jacking pipes. This paper presents the field performance of concrete pipes during the jacking carried out under the Guan River in Jiangsu, China. Rebar stresses at two wings (the left and right side), the top crest, and the base in the longitudinal and circumferential directions for four different pipes were monitored. The maximum rebar stresses during the jacking were 37.1 MPa in the longitudinal direction and 36.6 MPa in the circumferential direction. However, the maximum rebar stresses after construction were only 18.5 MPa in the longitudinal direction and 20.3 MPa in the circumferential direction. A normalized jacking force “α” is proposed to evaluate the additional rebar stress in jacking pipes. The range of α is from 0.04 to 0.25. The relationship between the rebar stress and the construction procedure is presented and discussed. An excessive jacking force, an alignment deviation or an increased penetration rate would generate a large incremental rebar stress. 相似文献
994.
Frank A. Hoeberichts Jorge Perez‐Valle Consuelo Montesinos Jos M. Mulet María D. Planes Guillem Hueso Lynne Yenush Sukesh C. Sharma Ramn Serrano 《Yeast (Chichester, England)》2010,27(9):713-725
Glucose, in the absence of additional nutrients, induces programmed cell death in yeast. This phenomenon is independent of yeast metacaspase (Mca1/Yca1) and of calcineurin, requires ROS production and it is concomitant with loss of cellular K+ and vacuolar collapse. K+ is a key nutrient protecting the cells and this effect depends on the Trk1 uptake system and is associated with reduced ROS production. Mutants with decreased activity of plasma membrane H+‐ATPase are more tolerant to glucose‐induced cell death and exhibit less ROS production. A triple mutant ena1‐4 tok1 nha1, devoid of K+ efflux systems, is more tolerant to both glucose‐ and H2O2‐induced cell death. We hypothesize that ROS production, activated by glucose and H+‐ATPase and inhibited by K+ uptake, triggers leakage of K+, a process favoured by K+ efflux systems. Loss of cytosolic K+ probably causes osmotic lysis of vacuoles. The nature of the ROS‐producing system sensitive to K+ and H+ transport is unknown. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
995.
Rogério Cezar de Cerqueira Leite Manoel Regis Lima Verde Leal Luís Augusto Barbosa Cortez W. Michael Griffin Mirna Ivonne Gaya Scandiffio 《Energy》2009
Increasing use of petroleum, coupled with concern for global warming, demands the development and institution of CO2 reducing, non-fossil fuel-based alternative energy-generating strategies. Ethanol is a potential alternative, particularly when produced in a sustainable way as is envisioned for sugarcane in Brazil. We consider the expansion of sugarcane-derived ethanol to displace 5% of projected gasoline use worldwide in 2025. With existing technology, 21 million hectares of land will be required to produce the necessary ethanol. This is less than 7% of current Brazilian agricultural land and equivalent to current soybean land use. New production lands come from pasture made available through improving pasture management in the cattle industry. With the continued introduction of new cane varieties (annual yield increases of about 1.6%) and new ethanol production technologies, namely the hydrolysis of bagasse to sugars for ethanol production and sugarcane trash collection providing renewable process energy production, this could reduce these modest land requirements by 29–38%. 相似文献
996.
997.
In groupware tools, the activation of a function may affect other users who might have conflicting interests. We developed technical mechanisms to support users in resolving them. Contrary to current implementations of groupware tools, these mechanisms strengthen the position of the users who are affected by the activation of said functions. Supporting the visibility of a function's activation, and providing a channel for communication or means to intervene against the function's activation are approaches which constitute a framework to implement these mechanisms. We conclude with showing implementation examples of the framework and their evaluation in the POLITeam project. 相似文献
998.
就美国政府关于逐步削减HFC消费与生产的最新表态,对其背景、立场,美国政府所面临的尴尬局面及中国人该怎么办作了简短评述. 相似文献
999.
本文用简明的方法推导了直流线性和非线性电阻电路的位函数,对于含压控型电阻和流控型电阻的混合电路,引入了混合容度的概念,最后讨论了位函数的两个新应用:估计输入电阻、非线性规划的电路模拟。 相似文献
1000.
蒋友谅 《北京工业大学学报》1991,(2)
在薄板大挠度问题最小势能原理的一种新提法(势能密度中同时含有应变与应力函数的形式)的基础上,用线性Lagrange乘子法,解除包括薄膜和弯曲广义应力-广义应变关系在内的全部变分约束条件,建立了一个新的薄板大挠度问题三类变量广义势能原理。 相似文献