全文获取类型
收费全文 | 397412篇 |
免费 | 14171篇 |
国内免费 | 6654篇 |
专业分类
电工技术 | 11727篇 |
技术理论 | 9篇 |
综合类 | 10994篇 |
化学工业 | 61904篇 |
金属工艺 | 22707篇 |
机械仪表 | 17819篇 |
建筑科学 | 14688篇 |
矿业工程 | 6139篇 |
能源动力 | 7316篇 |
轻工业 | 21537篇 |
水利工程 | 6881篇 |
石油天然气 | 16986篇 |
武器工业 | 1061篇 |
无线电 | 39657篇 |
一般工业技术 | 75880篇 |
冶金工业 | 38966篇 |
原子能技术 | 10448篇 |
自动化技术 | 53518篇 |
出版年
2023年 | 2475篇 |
2022年 | 5482篇 |
2021年 | 7518篇 |
2020年 | 5709篇 |
2019年 | 5326篇 |
2018年 | 21414篇 |
2017年 | 20979篇 |
2016年 | 17428篇 |
2015年 | 7626篇 |
2014年 | 9986篇 |
2013年 | 14807篇 |
2012年 | 16305篇 |
2011年 | 24048篇 |
2010年 | 20588篇 |
2009年 | 18158篇 |
2008年 | 19386篇 |
2007年 | 19775篇 |
2006年 | 11164篇 |
2005年 | 10868篇 |
2004年 | 9143篇 |
2003年 | 9033篇 |
2002年 | 8389篇 |
2001年 | 7596篇 |
2000年 | 6958篇 |
1999年 | 6346篇 |
1998年 | 9462篇 |
1997年 | 7165篇 |
1996年 | 5697篇 |
1995年 | 4525篇 |
1994年 | 3933篇 |
1993年 | 3787篇 |
1992年 | 3268篇 |
1991年 | 3149篇 |
1990年 | 3218篇 |
1989年 | 3054篇 |
1988年 | 2970篇 |
1987年 | 2776篇 |
1986年 | 2759篇 |
1985年 | 2765篇 |
1984年 | 2611篇 |
1983年 | 2527篇 |
1981年 | 2576篇 |
1979年 | 2706篇 |
1978年 | 2883篇 |
1977年 | 2863篇 |
1976年 | 3514篇 |
1975年 | 2684篇 |
1974年 | 2710篇 |
1973年 | 2756篇 |
1972年 | 2562篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Gina Cavaliere Giovanna Trinchese Nadia Musco Federico Infascelli Chiara De Filippo Vincenzo Mastellone Valeria Maria Morittu Pietro Lombardi Raffaella Tudisco Micaela Grossi Vincenzo Monda Monica I. Cutrignelli Antonietta Messina Serena Calabrò Heleena B. Moni Luigi Stradella Giovanni Messina Marcellino Monda Maria Pina Mollica 《Journal of dairy science》2018,101(3):1843-1851
Excessive energy intake may evoke complex biochemical processes characterized by inflammation, oxidative stress, and impairment of mitochondrial function that represent the main factors underlying noncommunicable diseases. Because cow milk is widely used for human nutrition and in food industry processing, the nutritional quality of milk is of special interest with respect to human health. In our study, we analyzed milk produced by dairy cows fed a diet characterized by a high forage:concentrate ratio (high forage milk, HFM). In view of the low n-6:n-3 ratio and high content of conjugated linoleic acid of HFM, we studied the effects of this milk on lipid metabolism, inflammation, mitochondrial function, and oxidative stress in a rat model. To this end, we supplemented for 4 wk the diet of male Wistar rats with HFM and with an isocaloric amount (82 kJ, 22 mL/d) of milk obtained from cows fed a diet with low forage:concentrate ratio, and analyzed the metabolic parameters of the animals. Our results indicate that HFM may positively affect lipid metabolism, leptin:adiponectin ratio, inflammation, mitochondrial function, and oxidative stress, providing the first evidence of the beneficial effects of HFM on rat metabolism. 相似文献
63.
Buryakov A. M. Khusyainov D. I. Mishina E. D. Khabibullin R. A. Yachmenev A. E. Ponomarev D. S. 《Technical Physics Letters》2018,44(12):1115-1119
Technical Physics Letters - The influence of excitation photons energy on the relaxation times of photoexcited carriers is studied. The involved relaxation mechanisms are evaluated and the... 相似文献
64.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards. 相似文献
65.
66.
67.
68.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献
69.
Baizhan Li Chenqiu Du Hong Liu Wei Yu Jie Zheng Meilan Tan Zhenxing Jin Wenjie Li Jing Wu Lu Chen Runming Yao 《Indoor air》2019,29(2):308-319
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being. 相似文献
70.