全文获取类型
收费全文 | 63710篇 |
免费 | 5478篇 |
国内免费 | 2804篇 |
专业分类
电工技术 | 3376篇 |
技术理论 | 2篇 |
综合类 | 3312篇 |
化学工业 | 12807篇 |
金属工艺 | 1897篇 |
机械仪表 | 2249篇 |
建筑科学 | 3765篇 |
矿业工程 | 5831篇 |
能源动力 | 5561篇 |
轻工业 | 4492篇 |
水利工程 | 262篇 |
石油天然气 | 17904篇 |
武器工业 | 271篇 |
无线电 | 1262篇 |
一般工业技术 | 3239篇 |
冶金工业 | 3288篇 |
原子能技术 | 632篇 |
自动化技术 | 1842篇 |
出版年
2024年 | 207篇 |
2023年 | 828篇 |
2022年 | 1659篇 |
2021年 | 2222篇 |
2020年 | 2341篇 |
2019年 | 1953篇 |
2018年 | 1724篇 |
2017年 | 1810篇 |
2016年 | 2312篇 |
2015年 | 2222篇 |
2014年 | 3961篇 |
2013年 | 3802篇 |
2012年 | 4922篇 |
2011年 | 5059篇 |
2010年 | 3387篇 |
2009年 | 3310篇 |
2008年 | 2815篇 |
2007年 | 3563篇 |
2006年 | 3833篇 |
2005年 | 3169篇 |
2004年 | 2724篇 |
2003年 | 2412篇 |
2002年 | 2058篇 |
2001年 | 1879篇 |
2000年 | 1596篇 |
1999年 | 1268篇 |
1998年 | 968篇 |
1997年 | 841篇 |
1996年 | 661篇 |
1995年 | 549篇 |
1994年 | 440篇 |
1993年 | 317篇 |
1992年 | 258篇 |
1991年 | 203篇 |
1990年 | 175篇 |
1989年 | 159篇 |
1988年 | 60篇 |
1987年 | 45篇 |
1986年 | 41篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 18篇 |
1981年 | 61篇 |
1980年 | 35篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 5篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
11.
A feasibility analysis methodology adopted from reactive distillation is applied to membrane reactors. A model is formulated to depict the reactive liquid phase composition on the retentate side of a continuous type membrane reactor. The effects of both the chemical reaction kinetics and the membrane mass transfer kinetics on the feasible products are elucidated by means of retentate phase diagrams and bifurcation analysis. The proposed method can be applied to various membrane processes, independent of the specific structure of the membrane. Two quaternary reaction systems are considered to illustrate the methodology. In the first hypothetical system, it is shown how selective membranes can influence the sequence of effective volatilities which in turn affects the feasible products of the system. In the second example of practical importance, i.e. the heterogeneously catalysed synthesis of propyl acetate coupled with permeation through a porous polycarbonate membrane, the dusty gas model is applied to describe the component fluxes through the membrane. For the latter reaction system, the existence of reactive arheotrope is demonstrated. Arheotropes represent mass transfer controlled feasible products of membrane separation process. 相似文献
12.
�Ĵ������Ȼ�����������б�����Դ̽�� 总被引:11,自引:0,他引:11
本文应用天然气中甲烷、乙烷的碳同位素,甲烷的氢同位素,汞含量及天然气成分等指标,探讨了四川盆地天然气成因分类;并结合地质情况对气源层进行了探讨。 相似文献
14.
分析了电石法PVC生产链中电石炉烟气及电厂烟气二氧化硫的排放情况,指出利用电石炉烟气中的CO合成氨、再将合成氨用于燃煤电厂烟气的"氨法"脱硫是具有较大应用潜力的循环经济产业链。 相似文献
15.
Hydrate formation rate plays an important role in making hydrates for the storage and transport of natural gas. Micellar surfactant solutions were found to increase gas hydrate formation rate and storage capacity. With the presence of surfactant, hydrate could form quickly in a quiescent system and the energy costs of hydrate formation reduced. Surfactants (an anionic surfactant, a non‐ionic surfactant and their mixtures) and liquid hydrocarbons (cyclopentane and methylcyclohexane) were used to improve hydrate formation. The experiments of hydrate formation were carried out in the pressure range 3.69–6.82 MPa and the temperature range 274.05–277.55 K. The experimental pressures were kept constant during hydrate formation in each experimental run. The effect of anionic surfactant (sodium dodecyl sulphate (SDS)) on natural gas storage in hydrates is more pronounced compared to a non‐ionic surfactant (dodecyl polysaccharide glycoside (DPG)). The induction time of hydrate formation was reduced with the presence of cyclopentane (CP). Cyclopentane and methylcyclohexane (MCH) could increase hydrate formation rate, but reduced hydrate storage capacity The higher methylcyclohexane concentration, the lower the hydrate storage capacity. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
16.
A. Hofmann 《低温学》2004,44(3):159-165
An intermediate refrigeration with boil-off gas cooled shields using the boil-off gas stream is an alternative method to the conventional intermediate refrigeration with a cryogenic liquid.By using an analytical calculation method relations are derived, which enable complete predictions about the effectiveness of an intermediate refrigeration with boil-off gas cooled shields as a function of the number of shields for the different stored cryogenic liquids. For this theoretical derivation however, the restrictive assumption must be made that the thermal conductivity of the used insulation material has a constant value between the considered temperature boundaries.For purposes of a more exact calculation a numerical method is therefore suggested, which takes into consideration that the thermal conductivity is temperature-dependent. For a liquid hydrogen storage vessel with a perlite-vacuum insulation e.g., the effectiveness of one shield and its equilibrium temperature are given as a function of the position of the shield in the insulation space. 相似文献
17.
介绍了Shell渣油气化装置将渣油原料改为天然气时控制系统的改造方案。提出的改造思路不但可用于Shell渣油气化,也可用于德士古渣油气化的油改气工程中。 相似文献
18.
19.
煤气吹扫时惰性气体抑爆用量的优选 总被引:1,自引:0,他引:1
运用惰性气体消防抑爆理论,采用数学积分法计算出吹扫煤气设施时抑爆所需最少惰性气体需要量. 相似文献
20.
新型迷宫式气锚及其应用 总被引:6,自引:1,他引:5
新型迷宫式气锚将重力分离原理和离心分离原理有机地结合在一起,其基本型气锚主要由上、下两级组成。上级为离心式螺旋气锚,下级为重力分离式和离心分离式综合气锚,可使油气流经同一长度锚筒时,达到双倍的分离效果。可根据油井气量的大小(气液比值)组成任意级数,实现油气的高效分离。还可对低产能井、沉没度易出现负值的油井进行油气分离,维持油井一定时间的生产。现场28口井的应用表明,新型迷宫式气锚油气分离效果理想,能有效地提高泵效,平均泵效由原来的28.9%提高到43.8%。 相似文献