全文获取类型
收费全文 | 31673篇 |
免费 | 2356篇 |
国内免费 | 1361篇 |
专业分类
电工技术 | 1595篇 |
技术理论 | 6篇 |
综合类 | 2215篇 |
化学工业 | 5358篇 |
金属工艺 | 2018篇 |
机械仪表 | 1993篇 |
建筑科学 | 2423篇 |
矿业工程 | 951篇 |
能源动力 | 855篇 |
轻工业 | 1885篇 |
水利工程 | 609篇 |
石油天然气 | 2018篇 |
武器工业 | 196篇 |
无线电 | 3438篇 |
一般工业技术 | 3824篇 |
冶金工业 | 1702篇 |
原子能技术 | 422篇 |
自动化技术 | 3882篇 |
出版年
2024年 | 110篇 |
2023年 | 478篇 |
2022年 | 778篇 |
2021年 | 1105篇 |
2020年 | 847篇 |
2019年 | 703篇 |
2018年 | 802篇 |
2017年 | 892篇 |
2016年 | 880篇 |
2015年 | 1074篇 |
2014年 | 1471篇 |
2013年 | 1823篇 |
2012年 | 1905篇 |
2011年 | 2251篇 |
2010年 | 1985篇 |
2009年 | 1912篇 |
2008年 | 1857篇 |
2007年 | 1671篇 |
2006年 | 1642篇 |
2005年 | 1441篇 |
2004年 | 1063篇 |
2003年 | 1024篇 |
2002年 | 1070篇 |
2001年 | 1061篇 |
2000年 | 817篇 |
1999年 | 872篇 |
1998年 | 725篇 |
1997年 | 576篇 |
1996年 | 521篇 |
1995年 | 428篇 |
1994年 | 375篇 |
1993年 | 265篇 |
1992年 | 208篇 |
1991年 | 153篇 |
1990年 | 120篇 |
1989年 | 105篇 |
1988年 | 75篇 |
1987年 | 51篇 |
1986年 | 54篇 |
1985年 | 24篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 5篇 |
1976年 | 13篇 |
1970年 | 6篇 |
1966年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO2 : O2 : N2 = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
3.
Junwei Fu Zhengbiao Zhang Zhenping Cheng Jian Zhu Wei Zhang Xiulin Zhu 《Polymer Bulletin》2008,61(3):287-297
A novel reversible addition-fragmentation chain transfer (RAFT) reagent bearing triphenylamine (TPA)
group, 4-diphenylamino-dithiobenzoic acid benzyl ester (DDABE), was designed and synthesized. It was used
in the RAFT polymerizations of styrene (St) and methyl acrylate (MA) to prepare end-functionalized polymers.
The results of the polymerization showed that the RAFT polymerizations could be well controlled using DDABE
as the RAFT agent. Number-average molecular weight (Mn,GPC) increased linearly
with monomer conversion, and molecular weight distributions were relatively narrow (PDI<
1.50). The results of chain-extension reaction, 1H NMR spectra and UV/Vis
spectra confirmed that most of the polymers chains were end-capped by the functional triphenylamine
(TPA) groups. The effect of feed molar ratios of St/DDABE/AIBN on polymerization was investigated. 相似文献
4.
哈尔滨炼油厂MTBE装置试生产 总被引:4,自引:0,他引:4
介绍了哈尔滨炼油厂MTBE装置的工艺路线、新技术的应用及特点;催化剂的装填及应用情况;总结了生产过程中遇到的一系列问题及解决办法;探索了平稳生产的新徐径,以保证装置安全、平稳、长周期运行;同时对反应器操作温度、催化蒸馏塔操作压力、原料中醇烯比等因素对异丁烯转化率及MTBE产品的影响做了简单的总结。 相似文献
5.
6.
本文针对天然气井提高钻井速度问题,总结分析了盆地中部井身结构,水力、机械参数,聚合物钻井液,正注反挤固井等工艺技术对该地区钻速的影响。指出提高天然气井钻井速度,必须搞好系统工程,形成配套技术。 相似文献
7.
应用不同剂量的~(60)Coγ射线照射含NT株弓形虫包囊的鼠脑匀浆后,以0.4%胰蛋白酶液消化,使弓形虫缓殖子从包囊中释放出来,并用生理盐水作连续10倍稀释,使成为含不同数量缓殖子的悬液,将此悬液接种小鼠,用生物检测方法确定其感染性。另设未经照射处理的缓殖子悬液感染小鼠的对照组。结果表明,γ射线0.55kGy剂量为控制鼠脑中NT株弓形虫感染性的最小有效剂量。γ射线0.1kGy剂量对弓形虫缓殖子感染性无明显影响,而0.45kGy照射后,其感染性较前者下降了10~4倍。 相似文献
8.
9.
To pick up serum high risk lithogenic factors predisposing one to gallstone formation and protective factors against gallstone formation in gallbladder. We compared serum lipid and apolipoprotein level of patients with gallbladder stone (stone group) with that of patients without gallbladder stone (control group). The correlation between serum lipid, apolipoprotein level and bile lipid level, cholesterol saturated index (CSI), characteristics of lipidemia in different kinds of gallbladder stones were studied. The results showed that the increase of serum Apo A1, C2 and E level in the stone group was more significant than in the control group. But there was no statistical significance in TC, TG, LDL-C, HDL-C, Apo A2, B, C3 level between the stone and control groups. These results suggested that serum apolipoproteins perhaps are more sensitive parameters than serum lipids in distinguishing patients with stones from those without stones. There were different profiles of serum lipid and apolipoproteins in different chemical types of gallbladder stones. Increased level in serum LDL-C, Apo B and ratio of LDL-C/HDL-C were characterized by an index for cholesterol stone, otherwise that in serum TG and Apo C2 an index for pigment stones. There was a positive correlation between serum total cholesterol (TC) or Apo B, C2, C3 and cholesterol amount or CSI in gallbladder bile. Therefore, TC, Apo B, C2, C3 could be considered as high risk lithogenic factors. A positive correlation existed between serum HDL-C and lecithin in gallbladder or common bile duct (CBD) bile as well as between HDL-C and bile acids in CBD bile. Thus, HDL-C might be a protective factor against gallstone formation in gallbladder. 相似文献
10.
以氧化锰矿粉为原料,添加ZB粘结剂进行冷固成团,所得冷固团块不仅具有足够的机械强度,而且具有良好的耐湿性,适用于长距离运输和露天堆存,是一种可与块矿性能相媲美的优质炉料,为充分利用矿山及冶炼厂的锰矿粉找到了一条良好的途径. 相似文献