全文获取类型
收费全文 | 28150篇 |
免费 | 1860篇 |
国内免费 | 1007篇 |
专业分类
电工技术 | 1085篇 |
技术理论 | 1篇 |
综合类 | 1337篇 |
化学工业 | 6134篇 |
金属工艺 | 894篇 |
机械仪表 | 1073篇 |
建筑科学 | 941篇 |
矿业工程 | 1841篇 |
能源动力 | 2420篇 |
轻工业 | 1433篇 |
水利工程 | 147篇 |
石油天然气 | 5956篇 |
武器工业 | 105篇 |
无线电 | 1240篇 |
一般工业技术 | 1776篇 |
冶金工业 | 2309篇 |
原子能技术 | 263篇 |
自动化技术 | 2062篇 |
出版年
2024年 | 87篇 |
2023年 | 364篇 |
2022年 | 614篇 |
2021年 | 799篇 |
2020年 | 861篇 |
2019年 | 740篇 |
2018年 | 743篇 |
2017年 | 805篇 |
2016年 | 913篇 |
2015年 | 867篇 |
2014年 | 1603篇 |
2013年 | 1840篇 |
2012年 | 1937篇 |
2011年 | 2306篇 |
2010年 | 1487篇 |
2009年 | 1444篇 |
2008年 | 1293篇 |
2007年 | 1476篇 |
2006年 | 1428篇 |
2005年 | 1364篇 |
2004年 | 1184篇 |
2003年 | 1092篇 |
2002年 | 904篇 |
2001年 | 778篇 |
2000年 | 674篇 |
1999年 | 643篇 |
1998年 | 522篇 |
1997年 | 421篇 |
1996年 | 373篇 |
1995年 | 363篇 |
1994年 | 222篇 |
1993年 | 169篇 |
1992年 | 144篇 |
1991年 | 106篇 |
1990年 | 92篇 |
1989年 | 63篇 |
1988年 | 38篇 |
1987年 | 46篇 |
1986年 | 36篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 15篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1974年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
Javier M. Grau JosM. Bisang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(1):105-110
This paper describes the parameters that are important in the industrial practice of silver removal from photographic fixers. The experiments were performed under potentiostatic control using synthetic solutions. The current efficiency was analysed as a function of the cathodic potential taking into account the deposit quality. A cathodic potential of ?0.5 V against a saturated calomel electrode is recommended. The conditions to prevent the darkening of the electrodeposit were investigated. The determination of silver concentration in the solution was made by direct potentiometry. The results obtained with synthetic fixers were corroborated by making the silver deposition from commercial fixers in an electrochemical reactor with rotating cylinder electrode intercalated in an electrolytic flow circuit in order to simulate practical conditions. 相似文献
13.
14.
15.
R.H. Ericksen 《Polymer》1985,26(5):733-746
Creep of Kevlar 29, Kevlar 49 and PRD 49-III fibres was investigated. The fibres exhibited transient creep and the strain-time relationship was represented by a logarithmic time law. The creep strain recovered with time when the load was removed. Upon reloading to the same creep stress the strain-time relationship was again logarithmic but the creep rate was reduced. Modulus measurements were made during the creep test and these showed that the modulus increased with time. This result indicated a crystallite rotation mechanism which could account for the experimentally observed creep strain. Creep in PRD 49-III fibres exhibited a small temperature dependence over the temperature range 20°C to 150°C. The apparent creep activation energy was consistent with the range of values reported for hydrogen bonding. This suggests one possible creep mechanism in which the combined action of stress and thermal activation causes rearrangement of intercrystalline bonds in the crystallite boundaries resulting in boundary creep. Boundary creep allows crystallite rotation which produces the macroscopic creep strain. Boundary creep is discussed in terms of the fibre morphology and a model of delayed elasticity. 相似文献
16.
Emmanuel O. Egbogah Richard A. Dawe 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(3):132-144
Recent studies have suggested the possibility of spontaneous emulsification as a mechanism for enhanced oil recovery (EOR). The discussions have, however, remained essentially qualitative. A study was therefore undertaken to estimate quantitatively the contribution of spontaneous emulsification as an EOR mechanism. The tests were conducted on several bulk liquid/liquid systems as well as by displacement experiments in unconsolidated synthetic sand packs. Spontaneous emulsification was found to be a mechanism for EOR: the estimated extra contribution to EOR due to this mechanism was found to be significant in laboratory scale displacement experiments. Tertiary recovery was always greater when spontaneous emulsification was evident than otherwise. Results of tests on bulk liquid/liquid systems indicate that the occurrence or absence of spontaneous emulsification can be correlated with the values of ‘partition parameter’. It may be concluded that higher oil recoveries may be achieved in chemical EOR processes where interface mass transfer (and the accompanying spontaneous emulsification) occurs. The evaluation of efficiency of residual oil mobilisation through the capillary number theory (with and without spontaneous emulsification) is also discussed. Displacement tests with spontaneously emulsifying systems showed that residual oil left behind a conventional waterflood was mobilised in a range of capillary numbers much less than that which applies to low-tension waterfloods. 相似文献
17.
确定异常高压气藏地质储量和可采储量的新方法 总被引:7,自引:1,他引:6
基于文献[1]的定容,封闭,异常高压气藏的物质平衡方程式,提出了确定异常高压气藏原始地质储量,可采储量和采收率的新方法,通过实例的应用和对比表明,提供的新方法是适用的有效的。 相似文献
18.
用于重离子核反应实验测量的纵向电场气体电离室 总被引:1,自引:0,他引:1
本文报道了一种新型的大动态范围,多叠层探测器系统组件之一的纵向电场气体电离室的构造,性能和在中能得离子核反应实验中的应用。 相似文献
19.
经试验发现应用一种化学肥料硫酸铵可以显著提高乌拉嘎金矿石的浮选回收率。闭路试验尾矿工艺矿物学鉴定证明,以硫酸铵作为调整剂的浮选过程中,微细粒单体金和金与石英边生体被有效回收。 相似文献
20.
Reviews the book, The chemically dependent: Phases of treatment and recovery edited by Barbara C. Wallace (see record 1992-98403-000). While this book is ambitious, interesting, educational, and useful, it is also disappointing, repetitious, and incomplete. Because it tries to accomplish so much, it may appear to have succeeded too little. This book is organized around, and explicative of, several basic ideas which might have been controversial if not heretical had this book been published ten years ago. Section I, purporting to link specific "phases of recovery" to particular forms and functions of treatment, will certainly be useful for novice clinicians but falls short of its overstated goals and is thereby disappointing. Section II is a collection of moderately redundant chapters describing the etiology and treatment of substance abusers from the viewpoints of psychoanalytic, psychodynamic, ego psychology, and object-relations theorists and therapists. Section III focuses on cognitive-behavioral, self-help, and relapse-prevention treatments. Section IV is quite uneven in quality of writing and applicability of content, and could have benefited from closer editorial scrutiny or selectivity. The final section focuses on special needs of particular subpopulations of substance abusers: African-Americans, prison inmates, HIV/AIDS patients, persons who are homeless, those who have been sexually and physically abused, and others. According to the reviewer this is not the best book on substance abuse treatment, but it does present some clinically useful ideas and it is worth reading. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献