全文获取类型
收费全文 | 320379篇 |
免费 | 5038篇 |
国内免费 | 725篇 |
专业分类
电工技术 | 6324篇 |
综合类 | 568篇 |
化学工业 | 49514篇 |
金属工艺 | 10496篇 |
机械仪表 | 9127篇 |
建筑科学 | 8363篇 |
矿业工程 | 892篇 |
能源动力 | 8966篇 |
轻工业 | 33482篇 |
水利工程 | 2659篇 |
石油天然气 | 3733篇 |
武器工业 | 10篇 |
无线电 | 40291篇 |
一般工业技术 | 60290篇 |
冶金工业 | 57287篇 |
原子能技术 | 5516篇 |
自动化技术 | 28624篇 |
出版年
2021年 | 2739篇 |
2020年 | 1987篇 |
2019年 | 2508篇 |
2018年 | 4105篇 |
2017年 | 3989篇 |
2016年 | 4072篇 |
2015年 | 2920篇 |
2014年 | 4938篇 |
2013年 | 15278篇 |
2012年 | 8106篇 |
2011年 | 10911篇 |
2010年 | 8492篇 |
2009年 | 9733篇 |
2008年 | 10181篇 |
2007年 | 10089篇 |
2006年 | 8934篇 |
2005年 | 8151篇 |
2004年 | 8006篇 |
2003年 | 7744篇 |
2002年 | 7556篇 |
2001年 | 7704篇 |
2000年 | 7347篇 |
1999年 | 7674篇 |
1998年 | 17898篇 |
1997年 | 13009篇 |
1996年 | 10227篇 |
1995年 | 7973篇 |
1994年 | 7277篇 |
1993年 | 6962篇 |
1992年 | 5319篇 |
1991年 | 5094篇 |
1990年 | 4963篇 |
1989年 | 4807篇 |
1988年 | 4697篇 |
1987年 | 3898篇 |
1986年 | 4027篇 |
1985年 | 4741篇 |
1984年 | 4307篇 |
1983年 | 4052篇 |
1982年 | 3618篇 |
1981年 | 3778篇 |
1980年 | 3476篇 |
1979年 | 3431篇 |
1978年 | 3233篇 |
1977年 | 3826篇 |
1976年 | 4871篇 |
1975年 | 2787篇 |
1974年 | 2665篇 |
1973年 | 2680篇 |
1972年 | 2215篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
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
32.
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
33.
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
34.
Gomes A. C. S. A. Costa L. C. Brito D. C. Frana R. J. Marques Mnica R. C. 《Polymer Bulletin》2020,77(4):1969-1981
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with... 相似文献
35.
36.
37.
38.
39.
Babilas R. Łoński W. Młynarek K. Bajorek A. Radoń A. 《Metallurgical and Materials Transactions A》2020,51(8):4215-4227
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y... 相似文献
40.
ABSTRACTThis paper deals with asymptotic stabilisation of a class of nonlinear input-delayed systems via dynamic output feedback in the presence of disturbances. The proposed strategy has the structure of an observer-based control law, in which the observer estimates and predicts both the plant state and the external disturbance. A nominal delay value is assumed to be known and stability conditions in terms of linear matrix inequalities are derived for fast-varying delay uncertainties. Asymptotic stability is achieved if the disturbance or the time delay is constant. The controller design problem is also addressed and a numerical example with an unstable system is provided to illustrate the usefulness of the proposed strategy. 相似文献