全文获取类型
收费全文 | 28738篇 |
免费 | 2713篇 |
国内免费 | 1570篇 |
专业分类
电工技术 | 1828篇 |
技术理论 | 2篇 |
综合类 | 2554篇 |
化学工业 | 4591篇 |
金属工艺 | 1271篇 |
机械仪表 | 1645篇 |
建筑科学 | 2152篇 |
矿业工程 | 644篇 |
能源动力 | 636篇 |
轻工业 | 3222篇 |
水利工程 | 631篇 |
石油天然气 | 1255篇 |
武器工业 | 237篇 |
无线电 | 3192篇 |
一般工业技术 | 2943篇 |
冶金工业 | 1128篇 |
原子能技术 | 342篇 |
自动化技术 | 4748篇 |
出版年
2024年 | 117篇 |
2023年 | 389篇 |
2022年 | 815篇 |
2021年 | 1044篇 |
2020年 | 829篇 |
2019年 | 631篇 |
2018年 | 771篇 |
2017年 | 836篇 |
2016年 | 762篇 |
2015年 | 1098篇 |
2014年 | 1521篇 |
2013年 | 1792篇 |
2012年 | 2115篇 |
2011年 | 2247篇 |
2010年 | 2166篇 |
2009年 | 2009篇 |
2008年 | 2085篇 |
2007年 | 2031篇 |
2006年 | 1757篇 |
2005年 | 1511篇 |
2004年 | 1099篇 |
2003年 | 861篇 |
2002年 | 892篇 |
2001年 | 722篇 |
2000年 | 620篇 |
1999年 | 469篇 |
1998年 | 371篇 |
1997年 | 273篇 |
1996年 | 225篇 |
1995年 | 207篇 |
1994年 | 162篇 |
1993年 | 135篇 |
1992年 | 96篇 |
1991年 | 87篇 |
1990年 | 70篇 |
1989年 | 59篇 |
1988年 | 32篇 |
1987年 | 24篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 7篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1969年 | 4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
11.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry 相似文献
12.
We consider the effect of multiple fibers on wavelength division multiplexing networks without wavelength conversion. We study networks with dynamic wavelength routing and develop accurate analytical models to compare various possible options using single- and multiple-fiber networks. We use results of an analytical model and simulation-based studies to evaluate the blocking performance and cost of multifiber networks. The number of fibers required providing high performance in multifiber networks and their costs are compared. A case is made for using multiple fibers in each link with fewer wavelengths instead of using a single fiber with many wavelengths. In particular, we show that a network with four fibers per link and with four wavelengths on each fiber without any wavelength conversion on any node yields similar same performance as the networks with one fiber per link and 16 wavelengths per fiber on each link and with full wavelength conversion capability on all nodes. In addition, the multifiber network may also offer the cost advantage depending on the relative cost of components. We develop a parametric cost model to show that multiple fibers in each link are an attractive option. Finally, such multifiber networks also has fault tolerance, with respect to a single fiber failure, already built into the system. 相似文献
13.
含缺陷压力管道经缺陷评定合乎使用后,其疲劳寿命的估计具有重要的工程意义。将整个含缺陷压力管道作为一个整体,分析了含缺陷压力管道的疲劳裂纹扩展特点,提出了相应的含缺陷压力管道疲劳寿命的计算过程,并在基于可靠性评价的基础上,给出了核压力管道的可接受失效概率,最终得到了含缺陷核压力管道疲劳寿命预测方法。 相似文献
14.
15.
16.
Polyaryloxydiphenylsilanes were prepared from phosphorus‐containing diols and diphenydichlorolsilane through solution polymerization. With a stoichiometric imbalance in feed monomers, the resulting polymers exhibited moderate melting points and good processing properties. The polymers prepared showed initial decomposition temperatures above 340 °C, excellent thermal stability, high char yields at 850 °C and very high limited oxygen index values of 56–59. The polymers' char yields and their (P + Si) contents showed linear relationships. © 2003 Society of Chemical Industry 相似文献
17.
介绍温度采集仪调理电路的结构及工作原理,简单介绍在系统可编程模拟器件ispPAC10的基本结构,并借助于PAC Designer软件详细描述ispPAC10实现温度采集仪数据放大器具体方法和步骤。与传统的模拟电路设计方法相比,运用isp技术实现的温度采集仪调理电路具有简洁可靠、开发周期短等特点。 相似文献
18.
新产品研发是建陶企业可持续发展的核心 总被引:2,自引:0,他引:2
新世纪我国建陶企业在整个国民经济的带动下将进一步发展,入世后经济全球化的市场竞争格局,建陶企业只有走新产口研发之路,严格企业管理,才会在日趋激烈的市场竞争中得以生存和可持续发展。 相似文献
19.
20.
To determine whether there is any correlation between sudden decrease in barometric pressure and onset of labor, a non-experimental, retrospective study at a 948-bed tertiary care hospital was done. Pregnant patients of 36 weeks gestation or more who presented with spontaneous onset of labor during the 48 hours surrounding the 12 occurrences of significant drop in barometric pressure in 1992 were included in the study. Significantly more occurrences of onset of labor were identified in the 24 hours after a drop in barometric pressure than were identified in the 24 hours prior to the drop in barometric pressure (P < 0.05). Therefore, the overall number of labor onsets increased in the 24 hours following a significant drop in barometric pressure. 相似文献