全文获取类型
收费全文 | 421648篇 |
免费 | 6209篇 |
国内免费 | 1408篇 |
专业分类
电工技术 | 8246篇 |
综合类 | 342篇 |
化学工业 | 61671篇 |
金属工艺 | 16046篇 |
机械仪表 | 12245篇 |
建筑科学 | 10175篇 |
矿业工程 | 1613篇 |
能源动力 | 11159篇 |
轻工业 | 34516篇 |
水利工程 | 3752篇 |
石油天然气 | 5718篇 |
武器工业 | 22篇 |
无线电 | 55354篇 |
一般工业技术 | 83415篇 |
冶金工业 | 82212篇 |
原子能技术 | 7921篇 |
自动化技术 | 34858篇 |
出版年
2021年 | 3484篇 |
2020年 | 2646篇 |
2019年 | 3233篇 |
2018年 | 5540篇 |
2017年 | 5547篇 |
2016年 | 5807篇 |
2015年 | 3973篇 |
2014年 | 6696篇 |
2013年 | 19271篇 |
2012年 | 10516篇 |
2011年 | 14373篇 |
2010年 | 11635篇 |
2009年 | 13196篇 |
2008年 | 14022篇 |
2007年 | 13941篇 |
2006年 | 12250篇 |
2005年 | 11104篇 |
2004年 | 10757篇 |
2003年 | 10879篇 |
2002年 | 10231篇 |
2001年 | 10769篇 |
2000年 | 9985篇 |
1999年 | 10611篇 |
1998年 | 27405篇 |
1997年 | 18966篇 |
1996年 | 14741篇 |
1995年 | 11064篇 |
1994年 | 9743篇 |
1993年 | 9665篇 |
1992年 | 6849篇 |
1991年 | 6655篇 |
1990年 | 6490篇 |
1989年 | 6139篇 |
1988年 | 5901篇 |
1987年 | 4888篇 |
1986年 | 4840篇 |
1985年 | 5474篇 |
1984年 | 5019篇 |
1983年 | 4671篇 |
1982年 | 4300篇 |
1981年 | 4351篇 |
1980年 | 4040篇 |
1979年 | 3780篇 |
1978年 | 3563篇 |
1977年 | 4319篇 |
1976年 | 5842篇 |
1975年 | 3049篇 |
1974年 | 2948篇 |
1973年 | 2878篇 |
1972年 | 2465篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Multicomponent Diamond-Like Semiconductors Based on the InBV–CdS System: Bulk and Surface Properties
Semiconductors - According to developed methods, in the fields of the mutual solubility of initial binary compounds (InP, InSb, and CdS), solid solutions of the InP–CdS and InSb–CdS... 相似文献
42.
43.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
44.
Catalysis Letters - A new zirconium based carbonaceous solid acid catalyst Zr@CC-PA with both Lewis and Bronsted acidic sites was prepared by simultaneous carbonization and phosphonation of glucose... 相似文献
45.
Fischer-Tropsch synthesis of the CO2 in biogas aims at producing light hydrocarbons and increasing its calorific value for feeding into the grid. Fe catalysts with Mn and K as promoters are supposed to yield high amounts of light hydrocarbons. Using a Fe-Mn-K/MgO catalyst, a parameter screening and long-term experiments were carried out. The catalyst shows, within the examined range, the highest selectivity to C2–C4 hydrocarbons at 450 °C, 8 bar(a), and a gas hourly space velocity of 350 h−1. Calcination of the catalyst resulted in a significant drop of activity and an almost complete loss of selectivity to hydrocarbons. Admixture of steam to the reactant gas lowers the tendency to carbon deposition but also promotes the water-gas shift reaction and results in lower yields of hydrocarbons. 相似文献
46.
47.
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
48.
Salim Hengky K. Padfield Rory Lee Chew Tin Syayuti Khadijah Papargyropoulou Effie Tham Mun Hou 《Clean Technologies and Environmental Policy》2018,20(3):529-538
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food... 相似文献
49.
50.