全文获取类型
收费全文 | 12843篇 |
免费 | 1447篇 |
国内免费 | 929篇 |
专业分类
电工技术 | 513篇 |
综合类 | 1114篇 |
化学工业 | 2911篇 |
金属工艺 | 701篇 |
机械仪表 | 519篇 |
建筑科学 | 1281篇 |
矿业工程 | 1132篇 |
能源动力 | 691篇 |
轻工业 | 1318篇 |
水利工程 | 700篇 |
石油天然气 | 682篇 |
武器工业 | 62篇 |
无线电 | 649篇 |
一般工业技术 | 1330篇 |
冶金工业 | 762篇 |
原子能技术 | 341篇 |
自动化技术 | 513篇 |
出版年
2024年 | 30篇 |
2023年 | 175篇 |
2022年 | 321篇 |
2021年 | 407篇 |
2020年 | 429篇 |
2019年 | 394篇 |
2018年 | 391篇 |
2017年 | 486篇 |
2016年 | 519篇 |
2015年 | 536篇 |
2014年 | 747篇 |
2013年 | 915篇 |
2012年 | 945篇 |
2011年 | 1077篇 |
2010年 | 719篇 |
2009年 | 704篇 |
2008年 | 667篇 |
2007年 | 784篇 |
2006年 | 751篇 |
2005年 | 584篇 |
2004年 | 519篇 |
2003年 | 490篇 |
2002年 | 396篇 |
2001年 | 326篇 |
2000年 | 299篇 |
1999年 | 285篇 |
1998年 | 208篇 |
1997年 | 172篇 |
1996年 | 157篇 |
1995年 | 144篇 |
1994年 | 136篇 |
1993年 | 89篇 |
1992年 | 97篇 |
1991年 | 51篇 |
1990年 | 62篇 |
1989年 | 43篇 |
1988年 | 32篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 24篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1959年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Yu. V. Balaban-Irmenin N. G. Fokina 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(4):228-232
The reliability of heat-supply systems is determined primarily by internal corrosion of the pipelines. The concentration of
oxygen in the water exerts a major influence on the corrosion. In systems with a standard oxygen content, OéDF-Zn is a highly
effective corrosion inhibitor. However, there are systems in which the quality of deaeration of the make-up water of the heat-supply
system is low (or deaeration is nonexistent), and the concentration of oxygen is considerably above the standard value. Classed
among these systems, for example, are the HWS systems, which are incorporated into closed heat-supply systems. The oxygen
concentration in these systems is analyzed to assess the situation.
__________
Translated from élektricheskie Stantsii, No. 6, June 2007, pp. 35–39. 相似文献
33.
L. Serra-Majem L. Bassas R. Garcí a-Glosas L. Ribas C. Ingl s I. Casals P. Saavedra A. G. Renwick 《Food Additives & Contaminants》2003,20(12):1097-1104
Cyclamate and its metabolite cyclohexylamine affect male fertility in high dose animal studies, but this affect has not been investigated in epidemiological studies. This paper reports the first epidemiological study designed to investigate the possibility of a relationship between cyclamate and cyclohexylamine and male fertility in humans, in which 405 cases of clinically defined infertility in men and 379 controls were surveyed. Semen evaluation, urine analysis for cyclamate and cyclohexylamine and dietary questionnaires were compared between cases and controls. No evidence was found of a significant association between cyclamate intake and male infertility; neither high cyclamate nor high cyclohexylamine excretion were associated with elevated risk. The lack of association remained after adjusting by age, area of residence, education, total energy intake and other variables. No significant correlations were observed between cyclamate intake, metabolism or excretion, and sperm count and motility. The results demonstrate no effect of cyclamate or cyclohexylamine on male fertility at the present levels of cyclamate consumption. 相似文献
34.
Resin cure following mold filling is an essential element in resin transfer molding. To fabricate a composite part with high dimensional stability and minimize residual stress, uniform resin cure should be achieved. This study considers a three-part resin system composed of epoxy, hardener and accelerator. The cure kinetics can be controlled by the accelerator concentration at the injection gate. A numerical method that can predict degree of cure distribution based on accelerator concentration at the gate was proposed. The degree of cure distribution is obtained by solving the resin flow, heat transfer, accelerator concentration and cure problems sequentially. Utilizing this numerical method, an optimal variation of accelerator concentration during mold filling was sought by solving a constrained optimization problem. The effect of accelerator control on degree of cure distribution was investigated and its validity was examined for two different geometries. 相似文献
35.
PH值对化学沉积制备CdS薄膜性质的影响 总被引:3,自引:1,他引:2
实验研究了pH值对化学沉积制备CdS薄膜性质的影响。表明:在柠檬酸钠作为络合剂的体系中随着溶液中氨水浓度的提高CdS薄膜会发生相变,从立方相变为六方相,即当氨水浓度为0.31M时,得到立方相的CdS薄膜;而当氨水的浓度大于0.51M时,得到六方相的CdS薄膜。氨水浓度的提高也使得CdS薄膜的形貌有了很大的改善,且制备得到的CdS薄膜从富CA变为富S,但是薄膜仍是n型。氨水浓度对CdS薄膜的光学性质也有很大的影响,随着氨水浓度的提高所得到的CdS薄膜的禁带宽度增大。 相似文献
36.
37.
39.
G. Lange 《Materialwissenschaft und Werkstofftechnik》2003,34(1):80-85
Failures by notch induced fatigue fractures Notches produce local stress concentrations and promote the formation of fatigue cracks. Characteristic types of notches as a result of design, manufacturing and operation are presented and remedial measures are discussed. Examples demonstrate the effect of different kinds of notches on various components. 相似文献
40.
Yilmaz Muslu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1991,51(4):449-460
A dispersed flow model previously developed to study substrate utilization in unsaturated media was experimentally verified and its practical application was considered. For this purpose, measurements were made using tap water and a synthetic feed solution. The importance of the change in fluid regime as regards to the simultaneous transport and reaction within biological filters were demonstrated. The effect of drop formation and the breakage of liquid jets inside the filters on substrate utilization was also shown. 相似文献