全文获取类型
收费全文 | 7383篇 |
免费 | 738篇 |
国内免费 | 205篇 |
专业分类
电工技术 | 467篇 |
综合类 | 839篇 |
化学工业 | 964篇 |
金属工艺 | 529篇 |
机械仪表 | 974篇 |
建筑科学 | 1334篇 |
矿业工程 | 364篇 |
能源动力 | 297篇 |
轻工业 | 641篇 |
水利工程 | 193篇 |
石油天然气 | 214篇 |
武器工业 | 79篇 |
无线电 | 275篇 |
一般工业技术 | 479篇 |
冶金工业 | 389篇 |
原子能技术 | 70篇 |
自动化技术 | 218篇 |
出版年
2024年 | 46篇 |
2023年 | 90篇 |
2022年 | 191篇 |
2021年 | 242篇 |
2020年 | 243篇 |
2019年 | 205篇 |
2018年 | 197篇 |
2017年 | 255篇 |
2016年 | 244篇 |
2015年 | 275篇 |
2014年 | 456篇 |
2013年 | 430篇 |
2012年 | 545篇 |
2011年 | 536篇 |
2010年 | 391篇 |
2009年 | 378篇 |
2008年 | 343篇 |
2007年 | 478篇 |
2006年 | 416篇 |
2005年 | 355篇 |
2004年 | 307篇 |
2003年 | 285篇 |
2002年 | 203篇 |
2001年 | 185篇 |
2000年 | 166篇 |
1999年 | 155篇 |
1998年 | 114篇 |
1997年 | 89篇 |
1996年 | 92篇 |
1995年 | 57篇 |
1994年 | 52篇 |
1993年 | 47篇 |
1992年 | 46篇 |
1991年 | 38篇 |
1990年 | 26篇 |
1989年 | 29篇 |
1988年 | 32篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有8326条查询结果,搜索用时 31 毫秒
61.
设计了基于三菱Q系列PLC以及InTouch的颗粒传送系统,提出自动颗粒传送系统的PLC程序设计方法,同时以InTouch为基础设计较为人性化的具有实时性的人机操作界面监控系统。主要阐述了上位机动态监视控制操作画面与下位机PLC数据处理系统结合,使得PLC的编程过程简单化从而使控制更为灵活,更使得PLC的功能得到拓展,其图形化交互式的人机界面,使操作更为简单。并具有实时及历史操作和报警记录。 相似文献
62.
回转窑运行轴线实时监测系统的原理与实现 总被引:3,自引:0,他引:3
回转窑运行轴线实时监测系统基于Labview软件平台,通过监测托轮位移来实现对回转窑运行轴线的监测,不仅能解决回转窑在生产实际中的动态测量难题,而且能实时反映回转窑的运行状况。 相似文献
63.
In studies of feeding by the bark beetle, Ips paraconfusus, two pine stilbenes (pinosylvin and pinosylvin methyl ether), ferulic acid glucoside, and enantiomers of the four most common sugars present in ponderosa pine phloem (sucrose, glucose, fructose, and raffinose) did not stimulate or reduce male feeding when assayed on wet -cellulose with or without stimulatory phloem extractives present. When allowed to feed on wet -cellulose containing sequential extracts (hexane, methanol, and water) of ponderosa pine phloem, methanol and water extractives stimulated feeding, but hexane extractives did not. Males confined in wet -cellulose containing aqueous or organic extracts of culture broths derived from phloem tissue and containing the root pathogen, Heterobasidion annosum, ingested less substrate than beetles confined to control preparations. In an assay using logs from uninoculated ponderosa pines, the mean lengths of phloem in the digestive tracts increased as time spent feeding increased. Males confined to the phloem of basal logs cut from ponderosa pines artificially inoculated with H. annosum ingested significantly less phloem than beetles in logs cut from trees that were (combined) mock-inoculated or uninoculated and did not contain the pathogen. However, individual pathogen-containing treatments were not significantly different from uninoculated controls. It was concluded that altered feeding rates are not a major factor which may explain why diseased ponderosa pines are colonized by I. paraconfusus. 相似文献
64.
Reactive mixing in a wavy torus reactor (WTR) has been examined experimentally. Its performances are compared to these of two other reactors: a plane torus reactor (PTR) and a baffled stirred tank reactor (BSTR). hydrodynamics of mixing has been studied using a plug flow model with axial dispersion for the WTR and PTR. The effect of axial dispersion on the kinetic of a chemical reaction was then analysed for the WTR, PTR and BSTR. Mixing times were slightly longer for the WTR due to a weaker axial dispersion. We also noticed an improvement of the convertion rate for low dissipated power. 相似文献
65.
Theories of plant chemical defenses discriminate between quantitative digestibility reducers (e.g., tannins) and qualitative toxins (e.g., alkaloids). Since the differential effect on taste of these compounds is poorly known, we recorded ingestive responses of a primate species, Microcebus murinus, to four tannin-rich plant extracts and to quinine, by using the behavioral method of the two-bottle test. The efficiency of tannic extracts at precipitating protein was measured with the blue BSA method. Inhibition taste thresholds for tannins added to a moderately sweet solution varied between 0.25 and 2 g/l. The threshold for quinine hydrochloride was 0.32 g/l. The profiles of the response/concentration curves established for these astringent and bitter substances were similar, with maximal inhibition of consumption occurring for near-threshold concentrations. The large amounts of quinine required to deter this small-bodied species from feeding were unexpected, given its unspecialized frugivorous/insectivorous diet. We propose that the taste responses of Microcebus to tannins have been shaped in relation to the widespread occurrence of efficient polyphenols in food plants, while low responsiveness to quinine reflects a low risk of ingesting toxic alkaloids when feeding on ripe fruits and insects. 相似文献
66.
The axial and radial distributions of solid and gas holdups were investigated in an air‐water‐glass bead circulating fluidized bed (GLSCFB) using a new ultrasonic technique, with a new method based on signal fluctuations. The cross‐sectional averaged gas and solid holdups measured at two axial positions appear to be similar at all studied operating conditions. The radial non‐uniformity decreases with increasing liquid velocity but does not change with an increasing solid circulating rate. The radial distribution of gas holdup was more uniform for 1.3 mm beads than for 433 µm glass beads. 相似文献
67.
68.
William E. Cooper Jr. 《Journal of chemical ecology》1991,17(5):849-863
The ability to discriminate prey chemicals from control substances and the presence of a poststrike elevation in tongue-flicking (PETF) rate are experimentally demonstrated in the lacertid lizard,Podarcis muralis, The tongue-flick attack score, a composite index of response strength, was significantly higher in response to integumental chemicals from cricket than to cologne or distilled water. The cricket chemicals additionally elicited a significantly greater rate of tongue-flicking and higher proportion of attacks by the lizards than did control stimuli. PETF combined with apparent searching movements strongly suggest the presence of strike-induced chemosensory searching (SICS). Experimental evidence indicates that both PETF and SICS occur in insectivorous representatives of three families of actively foraging autarchoglossan lizards, suggesting their widespread occurrence in such lizards. The adaptive roles of chemosensory behavior in the foraging behavior of P.Muralis are discussed. It is proposed that these lizards may form chemical search images and that PETF and SICS may have been present in the lacertilian ancestors of snakes. 相似文献
69.
气固下行流化床反应器Ⅱ气固两相的流动规律 总被引:1,自引:1,他引:1
气固下行流化床反应器气固两相流动过程是比较复杂的,沿轴向气固两相运动可分为第一加速、第二加速和恒速3个运动段,沿径向局部气体速度、颗粒速度和颗粒浓度都具有不同程度的不均匀性。而这种不均匀性是由气固两相顺重力场湍动运动所决定的。和循环床提升管相比,下行管反应器气固两相沿径向分布的不均匀性得到有效地改善,气固可以实现超短接触操作,因而是一种新型高效气固超短接触反应器 相似文献
70.
搅拌装置在化工厂中应用很广,在磷肥、钛白粉装置中(15kt/a)使用较多,仅钛白粉装置中就大约有40-50台,如增稠结晶器,中和槽等,搅拌操作所涉及的因素极为复杂,浆叶形式的选择,从力学的观点来说,迄今研究不够,本文就搅拌装置产生的轴向力问题进行了初步研究。 相似文献