全文获取类型
收费全文 | 155872篇 |
免费 | 6518篇 |
国内免费 | 2372篇 |
专业分类
电工技术 | 3082篇 |
技术理论 | 1篇 |
综合类 | 4510篇 |
化学工业 | 25134篇 |
金属工艺 | 8012篇 |
机械仪表 | 7423篇 |
建筑科学 | 5314篇 |
矿业工程 | 1319篇 |
能源动力 | 3947篇 |
轻工业 | 9804篇 |
水利工程 | 2211篇 |
石油天然气 | 1579篇 |
武器工业 | 271篇 |
无线电 | 20041篇 |
一般工业技术 | 29388篇 |
冶金工业 | 7386篇 |
原子能技术 | 1297篇 |
自动化技术 | 34043篇 |
出版年
2024年 | 192篇 |
2023年 | 963篇 |
2022年 | 1700篇 |
2021年 | 2577篇 |
2020年 | 1967篇 |
2019年 | 1894篇 |
2018年 | 16204篇 |
2017年 | 15220篇 |
2016年 | 12168篇 |
2015年 | 2978篇 |
2014年 | 3668篇 |
2013年 | 4965篇 |
2012年 | 8160篇 |
2011年 | 14736篇 |
2010年 | 12529篇 |
2009年 | 10042篇 |
2008年 | 10995篇 |
2007年 | 11373篇 |
2006年 | 3683篇 |
2005年 | 4125篇 |
2004年 | 3638篇 |
2003年 | 3608篇 |
2002年 | 2904篇 |
2001年 | 2188篇 |
2000年 | 1735篇 |
1999年 | 1375篇 |
1998年 | 1868篇 |
1997年 | 1231篇 |
1996年 | 1038篇 |
1995年 | 722篇 |
1994年 | 587篇 |
1993年 | 491篇 |
1992年 | 386篇 |
1991年 | 357篇 |
1990年 | 298篇 |
1989年 | 296篇 |
1988年 | 233篇 |
1987年 | 198篇 |
1986年 | 132篇 |
1985年 | 127篇 |
1984年 | 105篇 |
1983年 | 74篇 |
1982年 | 44篇 |
1976年 | 66篇 |
1968年 | 47篇 |
1966年 | 45篇 |
1965年 | 46篇 |
1959年 | 43篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Su-Il Ri Song-Il Hong Jong-Chol Kim Ju-Hyok Wi 《International Journal of Hydrogen Energy》2021,46(5):3319-3328
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance. 相似文献
22.
Jeongchan Lee Dr. Joonwon Kim Hyun Kim Eun-Jung Kim Prof. Dr. Hee-Jin Jeong Prof. Dr. Kwon-Young Choi Prof. Dr. Byung-Gee Kim 《Chembiochem : a European journal of chemical biology》2020,21(10):1446-1452
Tryptophan halogenases are found in diverse organisms and catalyze regiospecific halogenation. They play an important role in the biosynthesis of halogenated indole alkaloids, which are biologically active and of therapeutic importance. Here, a tryptophan 6-halogenase (SatH) from Streptomyces albus was characterized by using a whole-cell reaction system in Escherichia coli. SatH showed substrate specificity for chloride and bromide ions, leading to regiospecific halogenation at the C6-position of l -tryptophan. In addition, SatH exhibited higher performance in bromination than that of previously reported tryptophan halogenases in the whole-cell reaction system. Through structure-based protein mutagenesis, it has been revealed that two consecutive residues, A78/V79 in SatH and G77/I78 in PyrH, are key determinants in the regioselectivity difference between tryptophan 6- and 5-halogenases. Substituting the AV with GI residues switched the regioselectivity of SatH by moving the orientation of tryptophan. These data contribute to an understanding of the key residues that determine the regioselectivity of tryptophan halogenases. 相似文献
23.
24.
25.
Choi Paul Santos Christian Ariane Kim Min-Kun Jung Hyunsook Hong Do-Young Koo Junemo 《Journal of Mechanical Science and Technology》2021,35(11):5007-5022
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations... 相似文献
26.
27.
Kazuo Tsubota Stephen C. Pflugfelder Zuguo Liu Christophe Baudouin Hyo Myung Kim Elisabeth M. Messmer Friedrich Kruse Lingyi Liang Jimena Tatiana Carreno-Galeano Maurizio Rolando Norihiko Yokoi Shigeru Kinoshita Reza Dana 《International journal of molecular sciences》2020,21(23)
Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint. 相似文献
28.
Yude Ji Yanping Guo Yuejuan Liu Yun Tian 《International Journal of Adaptive Control and Signal Processing》2020,34(3):283-297
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results. 相似文献
29.
30.