全文获取类型
收费全文 | 31446篇 |
免费 | 3415篇 |
国内免费 | 1266篇 |
专业分类
电工技术 | 1931篇 |
技术理论 | 1篇 |
综合类 | 2275篇 |
化学工业 | 7992篇 |
金属工艺 | 575篇 |
机械仪表 | 1587篇 |
建筑科学 | 1114篇 |
矿业工程 | 671篇 |
能源动力 | 763篇 |
轻工业 | 7635篇 |
水利工程 | 250篇 |
石油天然气 | 921篇 |
武器工业 | 141篇 |
无线电 | 1666篇 |
一般工业技术 | 3451篇 |
冶金工业 | 1248篇 |
原子能技术 | 124篇 |
自动化技术 | 3782篇 |
出版年
2024年 | 125篇 |
2023年 | 520篇 |
2022年 | 808篇 |
2021年 | 1266篇 |
2020年 | 1185篇 |
2019年 | 1058篇 |
2018年 | 985篇 |
2017年 | 1128篇 |
2016年 | 1145篇 |
2015年 | 1235篇 |
2014年 | 1782篇 |
2013年 | 2153篇 |
2012年 | 2093篇 |
2011年 | 2179篇 |
2010年 | 1557篇 |
2009年 | 1723篇 |
2008年 | 1584篇 |
2007年 | 1981篇 |
2006年 | 1857篇 |
2005年 | 1543篇 |
2004年 | 1391篇 |
2003年 | 1181篇 |
2002年 | 994篇 |
2001年 | 780篇 |
2000年 | 676篇 |
1999年 | 571篇 |
1998年 | 451篇 |
1997年 | 367篇 |
1996年 | 294篇 |
1995年 | 274篇 |
1994年 | 235篇 |
1993年 | 183篇 |
1992年 | 190篇 |
1991年 | 137篇 |
1990年 | 111篇 |
1989年 | 66篇 |
1988年 | 45篇 |
1987年 | 44篇 |
1986年 | 38篇 |
1985年 | 43篇 |
1984年 | 29篇 |
1983年 | 18篇 |
1982年 | 20篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1974年 | 7篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
为解决震源在振动器提升后链条与销轴的断裂问题,应采用等张力原理对链条提升机构进行改进设计。经野外实践证明,这种机构基本上能够满足野外工作的要求。本文对目前所采用的机构形式可能存在的改进设计进行了分析。 相似文献
92.
含羧基的聚乙烯醇胺肟螯合纤维吸附钯的研究 总被引:4,自引:0,他引:4
研究了含羧基的聚乙烯醇胺肟(PVAAO-AAc)螯合纤维对钯的吸附,讨论了pH、温度、浓度、吸附时间对吸附率及回收率的影响。确定了最佳吸附条件,吸附钯的纤维用5%硫脲+0.10mol/L硝酸溶液可以解吸。 相似文献
93.
94.
Gelation Properties of Ovalbumin as Affected by Fatty Acid Salts 总被引:2,自引:0,他引:2
NAOKO YUNO-OHTA HIROKO TORYU TAKAHIKO HIGASA HIDEO MAEDA MITSUKO OKADA HIROYUKI OHTA 《Journal of food science》1996,61(5):906-910
The physicochemical properties of heat-induced ovalbumin (OVA) gels containing fatty acid salts (FAS) were investigated. Water-holding ability and transparency markedly increased in the presence of sodium caprate or sodium laurate. At 9% of the protein concentration transparent and hard gels formed; at 7%, transparent and soft gels formed. Scanning electron microscopy showed that the transparent gels had a more homogeneous structure than turbid gels without FAS. Differential scanning calorimetry indicated that denaturation temperature of OVA was decreased and the peaks became broader after addition of FAS. 相似文献
95.
The rapid discrimination of closely-related Saccharomyces cerevisiae strains can pose a significant problem to breweries, in particular where closely related strains are being used simultaneously to manufacture different products. In this study, two PCR approaches have been examined to assess their usefulness for the discrimination of brewery ale and lager yeast strains. PCR using arbitrary primers (RAPD PCR) was found unsuitable for such an application since the DNA profiles generated from brewery strains were generally found to be identical, due presumably to the close genetic relatedness of these yeasts. In contrast, PCR using δ sequence primers could rapidly differentiate between many ale and lager strains and characteristic profiles for these were generated. This method could also be applied directly to yeasts isolated from brewery worts or from active dried yeast preparations. Results of such analyses were available within the working day. 相似文献
96.
Ackerman Steven J.; Hilsenroth Mark J.; Knowles Eric S. 《Canadian Metallurgical Quarterly》2005,42(2):225
The present study examines the concurrent and predictive relationships between therapist psychodynamic-interpersonal activity and therapist-rated alliance. Ratings from 45 patient and therapist dyads engaged in short term psychodynamic psychotherapy from a point early (3rd or 4th session) and late (the session at which 90% of the treatment was completed) in treatment were used. The results suggest that therapists who have positive views of the alliance early in treatment also have positive views of the alliance later in treatment. Therapists who used psychodynamic-interpersonal activities early in treatment also made use of psychodynamic-interpersonal activities later in treatment. Moreover, the use of psychodynamic-interpersonal activities early in treatment was positively related to both global and specific aspects of therapist-rated alliance late in treatment. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
97.
KS Min AR Khan MK Kwon YJ Jung Z Yun Y Kiso 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(8):909-915
The performance of a laboratory‐scale anaerobic acidogenic fermenter fed with a mixture of blended kitchen food‐waste and primary sludge from a sewage treatment plant was investigated for the production of volatile fatty acids (VFA). The operating variables for acidogenic fermentation were kitchen food‐waste content (10 and 25 wt %), hydraulic retention time (HRT: 1, 3 and 5 days), temperature (ambient: 18 ± 2 °C, and mesophilic: 35 ± 2 °C) and pH (varied from 5.2 to 6.7). The experimental results indicated that effluent VFA concentrations and VFA production rates were higher at ambient temperature than at mesophilic conditions. The net amount of VFA with 10 wt % food‐waste increased up to 920 mg dm?3 with an increase of HRT, but contrasting results (a decrease of 2610 mg dm?3) were found due to the conversion of VFA into biogas in the case of 25 wt % food‐waste, which increased significantly at HRT of 3–5 days. In terms of biogas composition (CO2 and CH4), the organic matter was converted into CO2 through the oxidative pathway by facultative species at low temperature while mesophilic temperature and optimum pH (6.3–7.8) played a pivotal role in increasing rate of conversion of VFA into biogas by methanogenesis. Rates of VFA production and their conversion are dependent on the food‐waste content in the mixture. Yet, the higher concentration of food‐waste (25% compared with 10%) did not produce VFA proportionally due to the increased rate of conversion of VFA into gaseous products. The maximum VFA production rate (0.318 g VFAproduced g?1 VSfed day?1) was achieved in the 10 wt % food‐waste at ambient temperature and at a 5‐day HRT. Copyright © 2005 Society of Chemical Industry 相似文献
98.
用对苯二甲酸残渣合成混合苯二甲酸二丁酯的研究 总被引:1,自引:0,他引:1
以脱除轻组分的对苯二甲酸(TA)残渣与正丁醇为原料,通过酯化反应并对粗产物进行常压和减压蒸馏后制得混合苯二甲酸二丁酯.考察了压力、温度、时间及醇酸比(正丁醇与TA残渣中二元酸的摩尔比)等反应条件对酯化产物收率的影响.结果表明,最佳工艺条件为:反应压力0.5 MPa,反应温度230℃,醇酸比2.8:1.0,反应时间5 h.在此条件下,酯化产物的收率最高,约为93%.制得的混合苯二甲酸二丁酯的产品质量基本符合工业常用增塑剂邻苯二甲酸二丁酯的质量要求. 相似文献
99.
同步电动机转子时常由于磁极松动,导致电机振动现象严重.本文以烧结厂1#抽烟机转子检修为例对同步电机的转子检修进行探讨,很好的解决了这个问题.同时为同步电机转子检修提供了一整套检修方法. 相似文献
100.
自然灾害链及其断链减灾框架构建 总被引:1,自引:0,他引:1
基于灾害的链式理论及断链减灾思想,构建了自然灾害孕源断链减灾框架,并提出了减灾措施,对减灾措施的任务要点进行了阐述,从而正确的预测和有效的防治灾害链。 相似文献