全文获取类型
收费全文 | 108892篇 |
免费 | 11792篇 |
国内免费 | 7325篇 |
专业分类
电工技术 | 8815篇 |
技术理论 | 1篇 |
综合类 | 10227篇 |
化学工业 | 13271篇 |
金属工艺 | 6917篇 |
机械仪表 | 6603篇 |
建筑科学 | 7071篇 |
矿业工程 | 4113篇 |
能源动力 | 2967篇 |
轻工业 | 12305篇 |
水利工程 | 3339篇 |
石油天然气 | 3574篇 |
武器工业 | 1671篇 |
无线电 | 9648篇 |
一般工业技术 | 9063篇 |
冶金工业 | 12881篇 |
原子能技术 | 1590篇 |
自动化技术 | 13953篇 |
出版年
2024年 | 723篇 |
2023年 | 1870篇 |
2022年 | 4323篇 |
2021年 | 5488篇 |
2020年 | 3911篇 |
2019年 | 2706篇 |
2018年 | 2931篇 |
2017年 | 3363篇 |
2016年 | 3048篇 |
2015年 | 4692篇 |
2014年 | 5784篇 |
2013年 | 6820篇 |
2012年 | 8371篇 |
2011年 | 8692篇 |
2010年 | 8187篇 |
2009年 | 7517篇 |
2008年 | 7567篇 |
2007年 | 7294篇 |
2006年 | 6276篇 |
2005年 | 4884篇 |
2004年 | 3597篇 |
2003年 | 2516篇 |
2002年 | 2249篇 |
2001年 | 2076篇 |
2000年 | 1679篇 |
1999年 | 983篇 |
1998年 | 3211篇 |
1997年 | 1932篇 |
1996年 | 1256篇 |
1995年 | 746篇 |
1994年 | 616篇 |
1993年 | 667篇 |
1992年 | 167篇 |
1991年 | 155篇 |
1990年 | 173篇 |
1989年 | 154篇 |
1988年 | 122篇 |
1987年 | 114篇 |
1986年 | 98篇 |
1985年 | 81篇 |
1984年 | 31篇 |
1983年 | 36篇 |
1982年 | 57篇 |
1981年 | 81篇 |
1980年 | 93篇 |
1979年 | 31篇 |
1978年 | 25篇 |
1977年 | 183篇 |
1976年 | 315篇 |
1959年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
基于遗传算法的并发谈判在电子商务应用中具有独特的优势,但已有的研究尚未考虑议题之间的相关性、动态权重的变化规则依赖于对手信息的获取,极大地限制了其使用价值.对此,提出议题分组的方法以解决议题的相关性问题,而议题权重的变化则采取从历史资源中发掘知识的方法进行动态调整.构建了基于遗传算法的关联性议题并发谈判模型,给出了模型的形式化描述、谈判算法设计和动态权重更新方案.通过对模型的实验和比较分析,证实了该方案能够更方便地满足用户谈判的多样性需求,解决谈判中议题关联性的问题,而且能够快速、有效地得出最优谈判结果. 相似文献
192.
193.
轨道电路分路不良常见问题分析 总被引:2,自引:0,他引:2
马义不 《自动化与仪器仪表》2012,(1):110-111
轨道电路分路不良是比较常见的一种信号故障。由于缺少系统的原因分析,处理方法简单,尚未从根本上加以剖析、处理,因此事故未能完全控制。文章详细剖析轨道电路分路不良的常见问题以及一些应对措施,可以为解决轨道电路分路不良问题提供参考,为运输生产保驾护航。 相似文献
194.
A GROUP-CONTRIBUTION METHOD INVOLVING SPECIFIC GRAVITY AS A PARAMETER FOR ESTIMATING CRITICAL TEMPERATURES 总被引:2,自引:0,他引:2 下载免费PDF全文
A new group-contribution method involving specific gravity as a parameter is proposed for predicting criticaltemperature.Being appliable to all kinds of organic compounds,it gives an average percent deviation of 0.88%for 93 compounds and is particularly useful to those substances for which the normal boiling points are stillunknown. 相似文献
195.
EA Liberman AM Arzumanian MA Vladimirova LM Tsofina 《Canadian Metallurgical Quarterly》1976,21(3):476-481
"Zero-loop" of the molecular potential transformer of submitochondrial particles (SMP) is separated from the remaining electron transfer chain by rotenone, and its e.m.f. ET=0,003+RT/2F in [NADP X H] [NAD+]/[NADP+] [NAD X H] volts is used in the compensative method of measurement of the potential difference across the SMP membrane (delta USMP). The phospholipid membrane, measuring the concentration of the penetrating anions in the solution contained SMP, is used as "zero-indicators". This concentration drops monotonically with increase in delta USMP. Delta USMP is equal to ET when the addition of substrates of transhydrogenase reaction with definite ET does not change the potential across phospholipid membrane. 相似文献
196.
MA Bempong 《Canadian Metallurgical Quarterly》1976,14(1):6-14
In experiments carried out on Wistar rats ultrastructrual charges of hepatocytes were studied during long-term carcinogenesis due to N-Nitrosomorpholine administered as a 20 mg% solution in drinking water. Carcinoma usually developed after the 20th week of the experiment. The development of the tumour was preceded by early dystrophic changes and, later, by a precancerous posttoxic "glycogenosis". The structural alterations as observed during the precancerous stage were rather noncharacteristic so that they did not permit to disclose the exact point of neoplastic change of the hepatocytes. Nevertheless, the model of carcinogenesis as demonstrated here appears to be a rather standard one and seems to be suitable for studying oncological problems of general character. 相似文献
197.
MA Asher 《Canadian Metallurgical Quarterly》1976,7(3):583-591
Traumatic dislocations and subluxations of the upper extremity in children have been surveyed. The elbow joint is most commonly dislocated and is dislocated more frequently in children than in adults. Severe neurovascular injury may be associated with dislocation of this joint. The most common subluxation is that of the radial head, secondary to a "pulled elbow." Otherwise dislocations and subluxations of the upper extremity are uncommon in children, apparently because of the relative weakness of the epiphyseal plate. Most of these injuries are the result of predictable indirect forces. Principles of reduction and immobilization are based on the unique anatomic structure of the joint involved and the known anatomic disruption resulting from the trauma. 相似文献
198.
S Hatano MS Sadove DM Keane RE Boggs MA El-Naggar 《Canadian Metallurgical Quarterly》1976,25(10):457-463
Two hundred open heart cases anaesthetized with a combination of diazepam-ketamine using "Micro-Mini" drip administration technique were presented. The results were eminently desirable, and in the opinion of the authors are a notable improvement over other methods for all types of cardiovascular surgery including most advanced heart diseases. The advantages of this anaesthetic method for cardiovascular surgery are as follows: 1. Effects on cardiovascular system are minimal.--2. Respiratory depression is negligible.--3. There is no increase in salivation or muscle tone.--4. Induction and maintenance of anaesthesia are simple and smooth.--5. Anaesthesia can be maintained, using a high concentration of oxygen alone, by a slight increase in rate of ketamine administration whenever necessary.--6. Post-anaesthetic psychotomimetic effects are negligible.--7. Nearly 100% of patients have excellent amnesia.--8. It has a wide margin of safety.--9. This technique has proved highly acceptable to patients and surgeons. We feel ketamine should be used in small dosages continuously administered with either "Micro-Mini" drip infusion or infusion pump. Ketamine given in this fashion should be regarded as an analgesic. 相似文献
199.
S Hatano DM Keane RE Boggs MA El-Naggar MS Sadove 《Canadian Metallurgical Quarterly》1976,23(6):648-656
Two hundred open-heart cases were anaesthetized with a diazepam-ketamine combination. The results were excellent. A "Micro-Mini" drip technique insured low, even, but adequate dose levels of ketamine and less drug was used. Induction and maintenance are simple and smooth. Effects on the cardiovascular system and respiratory system are minimal. The margin of safety is wide and 100% oxygen can be used whenever needed. 相似文献
200.
Three convenience products--frozen, precooked chicken apple fritters, chicken breast fillets, and chicken patties--provided by one processor were subjectively evaluated by two taste panels of older adults, ranging in age from the sixties to middle eighties. The panelists represented a middle-income group maintaining private homes and a low-income group living in public housing. Both panels rated each product above "good" (score=4) or "fair" (score=3) on four acceptability factors and the overall score. Although mean scores of the low-income taste panel on all factors were generally higher for all products, the only significant difference (P less than .01) pertained to the appearance factor. Both panels indicated willingness to buy all three products. 相似文献