全文获取类型
收费全文 | 920411篇 |
免费 | 12189篇 |
国内免费 | 2179篇 |
专业分类
电工技术 | 17328篇 |
综合类 | 1272篇 |
化学工业 | 141148篇 |
金属工艺 | 35628篇 |
机械仪表 | 28269篇 |
建筑科学 | 22231篇 |
矿业工程 | 5444篇 |
能源动力 | 23991篇 |
轻工业 | 77767篇 |
水利工程 | 9986篇 |
石油天然气 | 18250篇 |
武器工业 | 101篇 |
无线电 | 105055篇 |
一般工业技术 | 180514篇 |
冶金工业 | 167345篇 |
原子能技术 | 20031篇 |
自动化技术 | 80419篇 |
出版年
2021年 | 7839篇 |
2019年 | 7539篇 |
2018年 | 12908篇 |
2017年 | 12946篇 |
2016年 | 13623篇 |
2015年 | 8917篇 |
2014年 | 14930篇 |
2013年 | 42347篇 |
2012年 | 23527篇 |
2011年 | 32312篇 |
2010年 | 25693篇 |
2009年 | 28925篇 |
2008年 | 29782篇 |
2007年 | 29561篇 |
2006年 | 26039篇 |
2005年 | 23750篇 |
2004年 | 22842篇 |
2003年 | 22456篇 |
2002年 | 21640篇 |
2001年 | 21229篇 |
2000年 | 20392篇 |
1999年 | 20687篇 |
1998年 | 48999篇 |
1997年 | 35363篇 |
1996年 | 27819篇 |
1995年 | 21380篇 |
1994年 | 19269篇 |
1993年 | 18923篇 |
1992年 | 14600篇 |
1991年 | 13844篇 |
1990年 | 13729篇 |
1989年 | 13281篇 |
1988年 | 12757篇 |
1987年 | 11365篇 |
1986年 | 11175篇 |
1985年 | 12926篇 |
1984年 | 11720篇 |
1983年 | 11039篇 |
1982年 | 10084篇 |
1981年 | 10344篇 |
1980年 | 9692篇 |
1979年 | 9703篇 |
1978年 | 9411篇 |
1977年 | 10778篇 |
1976年 | 13757篇 |
1975年 | 8428篇 |
1974年 | 8108篇 |
1973年 | 8324篇 |
1972年 | 6909篇 |
1971年 | 6383篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
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
92.
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
93.
94.
Ana Clara Sabbione Santiago Suárez María Cristina Añón Adriana Scilingo 《International Journal of Food Science & Technology》2019,54(5):1506-1513
In this study, amaranth flour was used as an ingredient to prepare gluten-free cookies. The production process and attributes of amaranth cookies were characterised, and the potential use of amaranth flour as a functional ingredient was analysed. Cookies exhibited a non-uniform reddish brown colour and a cookie factor ratio of 4.5 ± 0.6. Storage studies indicated that after 3 weeks at room temperature cookies presented slight variations in the texture. Simulated gastrointestinal digestion of this product was able to release peptides capable of exerting potential antithrombotic and antihypertensive activities, IC50 values of 0.22 ± 0.04 and 0.23 ± 0.03 mg mL−1 protein, respectively. This work demonstrates for the first time that food made with amaranth flour exerts potential antithrombotic and antihypertensive activity. In conclusion, these amaranth cookies could be an alternative way of incorporating potentially health beneficial products for people who choose a conscious diet, including coeliac or vegan consumers. 相似文献
95.
96.
In this paper, we present an aero‐structural model of a tethered swept wing for airborne wind energy generation. The carbon composite wing has neither fuselage nor actuated aerodynamic control surfaces and is controlled entirely from the ground using three separate tethers. The computational model is efficient enough to be used for weight optimisation at the initial design stage. The main load‐bearing wing component is a nontypical “D”‐shaped wing‐box, which is represented as a slender carbon composite shell and further idealised as a stack of two‐dimensional cross section models arranged along an anisotropic one‐dimensional beam model. This reduced 2+1D finite element model is then combined with a nonlinear vortex step method that determines the aerodynamic load. A bridle model is utilised to calculate the individual forces as a function of the aerodynamic load in the bridle lines that connect the main tether to the wing. The entire computational model is used to explore the influence of the bride on the D‐box structure. Considering a reference D‐box design along with a reference aerodynamic load case, the structural response is analysed for typical bridle configurations. Subsequently, an optimisation of the internal geometry and laminate fibre orientations is carried out using the structural computation models, for a fixed aerodynamic and bridle configuration. Aiming at a minimal weight of the wing structure, we find that for the typical load case of the system, an overall weight savings of approximately 20% can be achieved compared with the initial reference design. 相似文献
97.
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
98.
99.
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
100.