全文获取类型
收费全文 | 36646篇 |
免费 | 3223篇 |
国内免费 | 1949篇 |
专业分类
电工技术 | 3354篇 |
技术理论 | 1篇 |
综合类 | 3097篇 |
化学工业 | 6739篇 |
金属工艺 | 1598篇 |
机械仪表 | 2856篇 |
建筑科学 | 1779篇 |
矿业工程 | 1979篇 |
能源动力 | 1164篇 |
轻工业 | 3387篇 |
水利工程 | 1173篇 |
石油天然气 | 1639篇 |
武器工业 | 585篇 |
无线电 | 2618篇 |
一般工业技术 | 2380篇 |
冶金工业 | 2537篇 |
原子能技术 | 436篇 |
自动化技术 | 4496篇 |
出版年
2024年 | 76篇 |
2023年 | 377篇 |
2022年 | 697篇 |
2021年 | 967篇 |
2020年 | 1103篇 |
2019年 | 762篇 |
2018年 | 712篇 |
2017年 | 1013篇 |
2016年 | 1112篇 |
2015年 | 1283篇 |
2014年 | 2257篇 |
2013年 | 2092篇 |
2012年 | 2870篇 |
2011年 | 2977篇 |
2010年 | 2190篇 |
2009年 | 2110篇 |
2008年 | 2002篇 |
2007年 | 2533篇 |
2006年 | 2359篇 |
2005年 | 2053篇 |
2004年 | 1719篇 |
2003年 | 1555篇 |
2002年 | 1302篇 |
2001年 | 1116篇 |
2000年 | 864篇 |
1999年 | 758篇 |
1998年 | 526篇 |
1997年 | 459篇 |
1996年 | 367篇 |
1995年 | 310篇 |
1994年 | 279篇 |
1993年 | 172篇 |
1992年 | 187篇 |
1991年 | 118篇 |
1990年 | 110篇 |
1989年 | 88篇 |
1988年 | 80篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 36篇 |
1984年 | 35篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
81.
Temperature and pH‐responsive interpenetrating polymer network (IPN) hydrogels, constructed with poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA), by a sequential IPN method, were studied. The characterization of IPN hydrogels was investigated by Fourier‐transform infrared spectroscopy, differential scanning calorimetry (DSC) and swelling under various conditions. The IPN hydrogels exhibited relatively high swelling ratios, in the range 230–380 %, at 25 °C. The swelling ratios of the PMAA/PVA IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the amounts of freezing and non‐freezing water. The amount of free water increased with increasing PMAA content in the IPN hydrogels. Copyright © 2004 Society of Chemical Industry 相似文献
82.
林伟波 《水利水电科技进展》2006,26(2):59-61
以上海市淀北片河网闸门为例,开发了以基于Web的B/S结构为主、B/S与C/S相结合的河网闸门自动调度系统,介绍了该系统的整体框架和各子系统的功能。经实践检验,基于B/S与C/S相结合的闸门自动调度系统发挥了B/S与C/S各自的优点,提高了防洪决策的及时性和准确性。 相似文献
83.
84.
本文介绍了一个用户接口管理系统NUUIMS的设计和实现.重点叙述了该系统基于规范化目标用户接口模型的设计思想,系统组成及描述方法.文章也讨论了使用NUUIMS设计而成的用户接口的特点. 相似文献
85.
SIMULATION STUDIES OF THE REMOVAL OF WATER FROM ETHANOL BY A CATALYTIC DISTILLATION PROCESS 总被引:1,自引:0,他引:1
Christina B. Dirk-Faitakis Karl T. Chuang 《Chemical Engineering Communications》2005,192(11):1541-1557
A new approach based on catalytic distillation (CD) technology was proposed to remove water from ethanol. Isobutylene was introduced to react with water in the CD column. The commercial software simulation tool Aspen Plus was used to investigate the effects of key design factors such as operating pressure and temperature, reactant ratios, reflux and distillate to feed ratios, number of separation and reaction stages, and feed and reaction zone location. It was found that the CD technology offers potential advantages of reduced energy consumption and reduced capital cost over traditional approaches for the removal of water from ethanol. 相似文献
86.
Shuichi Yamamoto Teruaki Morihiro Koichi Ariyoshi Turkan Aktas 《Drying Technology》2005,23(6):1319-1330
As the surface properties of the drying materials are very important not only for the drying rate but also for the quality change during drying, the effects of surface concentration on the drying behavior of liquid foods (sugar solutions) were investigated by isothermal drying experiments and by numerical calculation experiments. The isothermal drying experiments with gelled sugar solution systems (sucrose and maltodextrin) were carried out at various relative humidity (RH) values (RH = 0 to 84%). Separate experiments were carried out for determination of the desorption isotherms.
The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.
When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased. 相似文献
The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.
When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased. 相似文献
87.
One of the problems encountered by automatic feeding devices, such as vibratory bowl feeders, in robotic assembly systems is nesting which leads to inseparability of parts and jamming. In this paper, we describe a design evaluation procedure to determine whether a part is prone to nesting and to quantify the degree of nesting. The proposed methodology reduces the 3-D protrusion-hole polyhedral containment problem of nesting to a 2-D polygon containment problem by employing a loop-based feature recognition scheme. Subsequently, the 3-D containment configuration is reconstructed from that of the 2-D by using a strategy calleddrop, pull and push. In this context, we introduce the notion of axis as a characteristic direction of a feature that facilitates the analysis of generalized 3-D polyhedral containment. The algorithms are applicable to generic B-Rep CAD data, and their time and space complexities are polynomial. 相似文献
88.
文章介绍了包钢连铸机结晶器液位、喷淋水、热坯压力等主要参数实现自动控制的过程,阐述了上述参数如何根据不同铸坯断面而改变,并针对钢厂开发新断面如何实现参数的切换提出解决办法. 相似文献
89.
变频器在暖通空调行业中的应用 总被引:1,自引:0,他引:1
本文提出中央空调系统的一种变频调速改造方案,介绍了该系统的结构组成及运行原理,对系统各部分的作用进行了讨论。 相似文献
90.