全文获取类型
收费全文 | 93380篇 |
免费 | 10313篇 |
国内免费 | 5770篇 |
专业分类
电工技术 | 7240篇 |
技术理论 | 9篇 |
综合类 | 7795篇 |
化学工业 | 13073篇 |
金属工艺 | 7447篇 |
机械仪表 | 4163篇 |
建筑科学 | 12547篇 |
矿业工程 | 4929篇 |
能源动力 | 2297篇 |
轻工业 | 8908篇 |
水利工程 | 3530篇 |
石油天然气 | 6043篇 |
武器工业 | 1009篇 |
无线电 | 7861篇 |
一般工业技术 | 7912篇 |
冶金工业 | 6495篇 |
原子能技术 | 1163篇 |
自动化技术 | 7042篇 |
出版年
2024年 | 455篇 |
2023年 | 1380篇 |
2022年 | 2682篇 |
2021年 | 3229篇 |
2020年 | 3426篇 |
2019年 | 2830篇 |
2018年 | 2694篇 |
2017年 | 3241篇 |
2016年 | 3595篇 |
2015年 | 3712篇 |
2014年 | 5931篇 |
2013年 | 5219篇 |
2012年 | 6806篇 |
2011年 | 6980篇 |
2010年 | 5103篇 |
2009年 | 5440篇 |
2008年 | 4852篇 |
2007年 | 6373篇 |
2006年 | 5765篇 |
2005年 | 4867篇 |
2004年 | 4180篇 |
2003年 | 3787篇 |
2002年 | 3285篇 |
2001年 | 2833篇 |
2000年 | 2334篇 |
1999年 | 1895篇 |
1998年 | 1355篇 |
1997年 | 1008篇 |
1996年 | 919篇 |
1995年 | 691篇 |
1994年 | 565篇 |
1993年 | 409篇 |
1992年 | 348篇 |
1991年 | 259篇 |
1990年 | 224篇 |
1989年 | 157篇 |
1988年 | 128篇 |
1987年 | 90篇 |
1986年 | 58篇 |
1985年 | 68篇 |
1984年 | 39篇 |
1983年 | 25篇 |
1982年 | 27篇 |
1981年 | 29篇 |
1980年 | 33篇 |
1979年 | 11篇 |
1975年 | 9篇 |
1964年 | 11篇 |
1959年 | 19篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
文章通过对黑龙江省高效节水现状,存在问题的分析,结合黑龙江省高效节水发展的支撑能力,阐述黑龙江省节水增粮目标、任务及总体布局,为黑龙江省2012—2015年节水增粮实施提供依据。 相似文献
3.
4.
5.
游世文 《食品安全质量检测学报》2019,10(3):761-764
目的探讨水﹑气﹑土壤中多环芳烃检测标准(HJ 478-2009﹑HJ 647-2013、HJ 784-2016)的正确出峰时间和顺序。方法用高效液相色谱来对苊烯、芴、苊、?、苯并(a)蒽进行定性分析,并与3个标准中的出峰顺序进行比较。结果苊烯、苊、芴、苯并(a)蒽、?的出峰时间分别为6.450、7.923、8.233、17.760、18.740min,与标准HJ478-2009﹑HJ647-2013的出峰顺序存在差异。结论在使用标准HJ478-2009﹑HJ647-2013、HJ 784-2016同时测定16种多环芳烃时,多环芳烃的出峰顺序及时间应以HJ 784-2016为准。 相似文献
6.
7.
Wang Hay Kan Chenxi Wei Dongchang Chen Tao Bo Bao‐Tian Wang Yan Zhang Yangchao Tian Jun‐Sik Lee Yijin Liu Guoying Chen 《Advanced functional materials》2019,29(17)
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes. 相似文献
8.
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
9.
10.
Evidence suggests that transient visual information, such as animations, may be more challenging to learn than static visualizations. However, when a procedural-manipulative task is involved, our evolved embodied cognition seems to reverse this transitory challenge. Hence, for object manipulative tasks, instructional animations may be more suitable than statics. We investigated this argument further by comparing animations with statics using a Lego task shown to university students, by examining three potential moderators of effectiveness: (a) the environment of manipulation (virtual or physical), (b) the quality of visual information (focused or unfocused), and (c) the presence of hands (no hands or with hands). In Experiment 1 we found an advantage of animation over statics, and no differences among the environments. In Experiment 2, we again observed an animation advantage, a small advantage of focused static information compared to unfocused static information, and a positive effect of not showing the hands. 相似文献