全文获取类型
收费全文 | 1615319篇 |
免费 | 26727篇 |
国内免费 | 7137篇 |
专业分类
电工技术 | 35014篇 |
综合类 | 6660篇 |
化学工业 | 276749篇 |
金属工艺 | 65817篇 |
机械仪表 | 46180篇 |
建筑科学 | 48498篇 |
矿业工程 | 11738篇 |
能源动力 | 50541篇 |
轻工业 | 126397篇 |
水利工程 | 16314篇 |
石油天然气 | 38037篇 |
武器工业 | 207篇 |
无线电 | 199936篇 |
一般工业技术 | 301318篇 |
冶金工业 | 216824篇 |
原子能技术 | 34394篇 |
自动化技术 | 174559篇 |
出版年
2021年 | 15715篇 |
2020年 | 12091篇 |
2019年 | 14825篇 |
2018年 | 18276篇 |
2017年 | 17713篇 |
2016年 | 22712篇 |
2015年 | 17750篇 |
2014年 | 28981篇 |
2013年 | 88400篇 |
2012年 | 38487篇 |
2011年 | 53077篇 |
2010年 | 45164篇 |
2009年 | 52754篇 |
2008年 | 48853篇 |
2007年 | 46523篇 |
2006年 | 47178篇 |
2005年 | 42382篇 |
2004年 | 43932篇 |
2003年 | 43654篇 |
2002年 | 42272篇 |
2001年 | 39621篇 |
2000年 | 37687篇 |
1999年 | 37766篇 |
1998年 | 62061篇 |
1997年 | 49517篇 |
1996年 | 41981篇 |
1995年 | 34658篇 |
1994年 | 31897篇 |
1993年 | 31879篇 |
1992年 | 27211篇 |
1991年 | 24439篇 |
1990年 | 24619篇 |
1989年 | 23686篇 |
1988年 | 22239篇 |
1987年 | 20448篇 |
1986年 | 19865篇 |
1985年 | 23126篇 |
1984年 | 22840篇 |
1983年 | 20799篇 |
1982年 | 19661篇 |
1981年 | 19849篇 |
1980年 | 18435篇 |
1979年 | 18848篇 |
1978年 | 18108篇 |
1977年 | 18607篇 |
1976年 | 20841篇 |
1975年 | 16240篇 |
1974年 | 15725篇 |
1973年 | 15831篇 |
1972年 | 13272篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
Popov N. N. Presnyakov D. V. Lar’kin V. F. 《Journal of Machinery Manufacture and Reliability》2020,49(3):232-236
Journal of Machinery Manufacture and Reliability - A device based on smart alloys has been designed for use in machine building items, in particular, in nuclear engineering, for preventing... 相似文献
122.
Bakirov Zh. B. Tanirbergenova A. A. 《Journal of Machinery Manufacture and Reliability》2020,49(3):263-271
Journal of Machinery Manufacture and Reliability - The problem of calculating the reliability and fatigue life of machine parts by the fatigue failure under random changes in the actual and limit... 相似文献
123.
Klimis?S.?NtalianisEmail author Anastasios?D.?Doulamis Nikolaos?D.?Doulamis Nikos?E.?Mastorakis Athanasios?S.?Drigas 《Journal of Signal Processing Systems》2015,80(2):153-161
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation. 相似文献
124.
125.
126.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations. 相似文献
127.
Norfariza Jamaluddin David C. Stuckey Arbakariya B. Ariff 《Critical reviews in food science and nutrition》2018,58(14):2453-2465
ABSTRACTBacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted. 相似文献
128.
Christoph Gottschalk Aiko Huckauf Arne Dübecke Florian Kaltner Matthias Zimmermann Ines Rahaus 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(7):1366-1383
The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment. 相似文献
129.
Poor aqueous solubility is one of the recurrent drawbacks of many compounds in medicinal chemistry. To overcome this limitation, the dilution of drug candidates from stock solutions of an organic solvent is common practice. However, the precise characterisation of these compounds in aqueous solutions is often neglected, leading to some uncertainties regarding the nature of the actual active species. In this communication, we demonstrate that two ruthenium complexes previously reported by our group for their chemotherapeutic potential against cancer, namely [Ru(DIP)2(sq)](PF6) and [Ru(DIP)2(3-methoxysq)](PF6), where DIP is 4,7-diphenyl-1,10-phenanthroline, sq=semiquinonate and 3-methoxysq=3-methoxysemiquinonate, form colloids in water-DMSO (1 % v/v) mixtures that are invisible to the naked eyes. [Ru(DIP)2(3-methoxysq)](PF6) was found to form a highly stable and monodispersed colloid with nanoaggregates of ∼25 nm. In contrast, [Ru(DIP)2(sq)](PF6) was found to form large reticulates of mostly spherical aggregates which size was found to increase over time. The difference in size and shape distribution of drug candidates is of tremendous significance as the study of their biological activity might be severely affected. Overall, we strongly believe that these observations should be taken into account by the scientific community working on the development of metal-based drugs with poor water solubility. 相似文献
130.