全文获取类型
收费全文 | 343782篇 |
免费 | 18384篇 |
国内免费 | 932篇 |
专业分类
电工技术 | 6127篇 |
综合类 | 391篇 |
化学工业 | 65172篇 |
金属工艺 | 12786篇 |
机械仪表 | 9739篇 |
建筑科学 | 9108篇 |
矿业工程 | 1958篇 |
能源动力 | 7862篇 |
轻工业 | 35291篇 |
水利工程 | 3592篇 |
石油天然气 | 7240篇 |
武器工业 | 26篇 |
无线电 | 38990篇 |
一般工业技术 | 71361篇 |
冶金工业 | 57272篇 |
原子能技术 | 7677篇 |
自动化技术 | 28506篇 |
出版年
2021年 | 2778篇 |
2020年 | 3367篇 |
2019年 | 5346篇 |
2018年 | 7232篇 |
2017年 | 7338篇 |
2016年 | 8177篇 |
2015年 | 6793篇 |
2014年 | 8512篇 |
2013年 | 17934篇 |
2012年 | 10325篇 |
2011年 | 12373篇 |
2010年 | 10846篇 |
2009年 | 11769篇 |
2008年 | 11734篇 |
2007年 | 11395篇 |
2006年 | 10026篇 |
2005年 | 9092篇 |
2004年 | 8447篇 |
2003年 | 8076篇 |
2002年 | 8098篇 |
2001年 | 7768篇 |
2000年 | 7423篇 |
1999年 | 7021篇 |
1998年 | 16433篇 |
1997年 | 12099篇 |
1996年 | 9275篇 |
1995年 | 6993篇 |
1994年 | 6313篇 |
1993年 | 6150篇 |
1992年 | 4654篇 |
1991年 | 4598篇 |
1990年 | 4414篇 |
1989年 | 4456篇 |
1988年 | 4375篇 |
1987年 | 3730篇 |
1986年 | 3731篇 |
1985年 | 4347篇 |
1984年 | 4140篇 |
1983年 | 3783篇 |
1982年 | 3554篇 |
1981年 | 3724篇 |
1980年 | 3585篇 |
1979年 | 3491篇 |
1978年 | 3563篇 |
1977年 | 4119篇 |
1976年 | 5421篇 |
1975年 | 3261篇 |
1974年 | 3098篇 |
1973年 | 3137篇 |
1972年 | 2702篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
131.
132.
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
133.
G. Inglese 《Inverse Problems in Science & Engineering》2019,27(4):439-459
We deal with the mathematical model of the incremental degradation of the internal coating (e.g. a polymeric material) of a metallic pipe in which a fluid flows relatively fast. The fluid drags solid impurities so that longitudinal scratches, inaccessible to any direct inspection procedure, are produced on the coating. Time evolution of this kind of defects can be reconstructed from the knowledge of a sequence of temperature maps of the external surface. The time-varying orthogonal section of this damaged interface is determined as a function of time and polar angle through the identification of a suitable effective heat transfer coefficient by means of Thin Plate Approximation. 相似文献
134.
Byakova O. V. Stepanov G. V. Vlasov A. O. Danylyuk V. E. Semenov N. V. Berezovs’kyi O. M. Gnyloskurenko S. V. 《Strength of Materials》2019,51(5):726-734
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to... 相似文献
135.
136.
Bram H. Frohock Jessica M. Gilbertie Dr. Jennifer C. Daiker Dr. Lauren V. Schnabel Dr. Joshua G. Pierce 《Chembiochem : a European journal of chemical biology》2020,21(7):933-937
The failure of frontline antibiotics in the clinic is one of the most serious threats to human health and requires a multitude of novel therapeutics and innovative approaches to treatment so as to curtail the growing crisis. In addition to traditional resistance mechanisms resulting in the lack of efficacy of many antibiotics, most chronic and recurring infections are further made tolerant to antibiotic action by the presence of biofilms. Herein, we report an expanded set of 5-benzylidene-4-oxazolidinones that are able to inhibit the formation of Staphylococcus aureus biofilms, disperse preformed biofilms, and, in combination with common antibiotics, are able to significantly reduce the bacterial load in a robust collagen-matrix model of biofilm infection. 相似文献
137.
Changmo Kim Izhar Livne‐Bar Karsten Gronert Jeremy M. Sivak 《Molecular nutrition & food research》2020,64(4)
Lipoxins (LXs) are autacoids, specialized proresolving lipid mediators (SPMs) acting locally in a paracrine or autocrine fashion. They belong to a complex superfamily of dietary small polyunsaturated fatty acid (PUFA)–metabolites, which direct potent cellular responses to resolve inflammation and restore tissue homeostasis. Together, these SPM activities have been intensely studied in systemic inflammation and acute injury or infection, but less is known about LX signaling and activities in the central nervous system. LXs are derived from arachidonic acid, an omega‐6 PUFA. In addition to well‐established roles in systemic inflammation resolution, they have increasingly become implicated in regulating neuroinflammatory and neurodegenerative processes. In particular, chronic inflammation plays a central role in Alzheimer's disease (AD) etiology, and dysregulated LX production and activities have been reported in a variety of AD rodent models and clinical tissue samples, yet with complex and sometimes conflicting results. In addition, reduced LX production following retinal injury has been reported recently by the authors, and an intriguing direct neuronal activity promoting survival and homeostasis in retinal and cortical neurons is demonstrated. Here, the authors review and clarify this growing literature and suggest new research directions to further elaborate the role of lipoxins in neurodegeneration. 相似文献
138.
139.
140.
E. G. Kulapina N. M. Makarova O. I. Kulapina I. A. Utc V. V. Baraguzina 《Petroleum Chemistry》2015,55(10):892-900
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection. 相似文献