全文获取类型
收费全文 | 43954篇 |
免费 | 2718篇 |
国内免费 | 56篇 |
专业分类
电工技术 | 290篇 |
综合类 | 33篇 |
化学工业 | 9685篇 |
金属工艺 | 800篇 |
机械仪表 | 871篇 |
建筑科学 | 1479篇 |
矿业工程 | 86篇 |
能源动力 | 1369篇 |
轻工业 | 8474篇 |
水利工程 | 449篇 |
石油天然气 | 218篇 |
武器工业 | 3篇 |
无线电 | 1858篇 |
一般工业技术 | 6747篇 |
冶金工业 | 8029篇 |
原子能技术 | 248篇 |
自动化技术 | 6089篇 |
出版年
2023年 | 376篇 |
2022年 | 381篇 |
2021年 | 1277篇 |
2020年 | 997篇 |
2019年 | 1115篇 |
2018年 | 1586篇 |
2017年 | 1576篇 |
2016年 | 1713篇 |
2015年 | 1351篇 |
2014年 | 1699篇 |
2013年 | 3377篇 |
2012年 | 2676篇 |
2011年 | 2946篇 |
2010年 | 2251篇 |
2009年 | 2170篇 |
2008年 | 2013篇 |
2007年 | 1795篇 |
2006年 | 1361篇 |
2005年 | 1180篇 |
2004年 | 1093篇 |
2003年 | 1008篇 |
2002年 | 884篇 |
2001年 | 608篇 |
2000年 | 521篇 |
1999年 | 580篇 |
1998年 | 2734篇 |
1997年 | 1757篇 |
1996年 | 1175篇 |
1995年 | 665篇 |
1994年 | 549篇 |
1993年 | 556篇 |
1992年 | 192篇 |
1991年 | 175篇 |
1990年 | 132篇 |
1989年 | 158篇 |
1988年 | 157篇 |
1987年 | 150篇 |
1986年 | 115篇 |
1985年 | 153篇 |
1984年 | 114篇 |
1983年 | 78篇 |
1982年 | 88篇 |
1981年 | 108篇 |
1980年 | 108篇 |
1979年 | 53篇 |
1978年 | 54篇 |
1977年 | 186篇 |
1976年 | 368篇 |
1975年 | 57篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Ignacio Brevis Ángel Rodríguez-Rozas Jaime H. Ortega David Pardo 《Computers & Mathematics with Applications》2019,77(5):1358-1375
We study the problem of source reconstruction for a linear elasticity problem applied to seismicity induced by mining. We assume the source is written as a variable separable function . We first present a simple proof a local decay result for elasticity in the case of homogeneous media. We then extend the source time reversal method, originally developed for acoustic waves, to an elastic system of waves. Additionally, we present a fast reconstruction implementation for large data sets. This is especially useful in the elastic case, in which the numerical cost is higher than in fluid acoustics. We complement this work with several 2D and 3D numerical experiments and an analysis of the results. 相似文献
82.
83.
Dr. Sónia Teixeira Dr. Miguel M. Santos Prof. Ricardo Ferraz Prof. Cristina Prudêncio Prof. Maria H. Fernandes Prof. João Costa-Rodrigues Dr. Luís C. Branco 《ChemMedChem》2019,14(20):1767-1770
Novel ionic liquids and organic salts based on mono- or dianionic zoledronate and protonated superbases, choline and n-alkylmethylimidazolium cations, were prepared and characterized by spectroscopic and thermal analyses. Most of the prepared salts display amorphous structures and very high solubility in water and saline solutions, especially the dianionic salts. Among the zoledronate-based ionic compounds, those containing choline [Ch] and methoxyethylmethylimidazolium [C3OMIM] cations appear to have significant cytotoxicity against human osteosarcoma cells (MG63) and low toxicity toward healthy skin fibroblast cells. Because osteosarcoma is a bone pathology characterized by an increase in bone turnover rate, the results presented herein may be a promising starting point for the development of new ionic pharmaceutical drugs against osteosarcoma. 相似文献
84.
85.
Andrés Mario Zervigón 《History of Photography》2019,43(2):130-143
For decades now, Douglas Crimp’s landmark 1980 essay ‘The Photographic Activity of Postmodernism’ has shaped our understanding of modernism’s aftermath, at least as it unfolded in North America and Western Europe. Less remembered, however, is the degree to which the procedures of disjunction, copying, appropriation, and outright theft that he highlighted were epitomised not just by contemporary photography, but by photomontage in particular. This article recovers the debates that led critics such as Crimp, Abigail Solomon-Godeau, Christopher Phillips, Benjamin Buchloh and others to turn to photomontage as one of their principal objects of concern in what became known as the postmodern critique of photography. Why was montage tasked to perform this critical function, particularly by people around the journal October who had not otherwise devoted the balance of their writing to photography’s history? The article suggests that these men and women, along with the contemporary artists they foregrounded, manifested what Mary Anne Doane has called a ‘desire for signification’, a reaction in the late 1970s against the mute theatricality of minimalist and conceptual art. Photomontage reintroduced representation to contemporary art and to the canon of art history. But unlike the reemerging illusionism in painting that also manifested this desire, montage guarded against an uncomplicated realism by highlighting and critiquing operations of representation in a manner that painting no longer could. 相似文献
86.
Scientometrics - A network analysis (NA) of keyword co-occurrences for a broad collection of Data envelopment analysis (DEA) papers in the period 2008–2017 is carried out. The raw keywords... 相似文献
87.
Miguel Muiz‐Calvente Adrin lvarez‐Vzquez Sergio Cicero Jos A.F.O. Correia Abilio M.P. de Jesus Sergio Blasn Alfonso Fernndez‐Canteli Filippo Berto 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(12):2663-2673
The fracture assessment of notched components based on cracked components approaches leads to over‐conservative failure predictions. In the research literature, several approaches are proposed to overcome this problem using an apparent fracture toughness, . Nevertheless, most of these approaches are based on deterministic assumptions despite the large and variable scatter exhibited by for different notch radii (ρ) or temperatures (T). This paper proposes a methodology for deriving a probabilistic field including the effect of temperature on the failure of notched components. First, the theory of critical distances is applied to transform each apparent fracture toughness into the equivalent fracture toughness for ρ = 0. Then, the temperature is supposed to act as a scale effect in the Weibull cumulative distribution function of the equivalent fracture toughness, and the corresponding scale effect function is derived. Finally, the applicability of the proposed methodology is illustrated by an example using two ferritic‐pearlitic steels: S275JR and S355J2. 相似文献
88.
Jardón-Pérez Luis E. Amaro-Villeda Adrian González-Rivera Carlos Trápaga Gerardo Conejo A. N. Ramírez-Argáez Marco A. 《Metallurgical and Materials Transactions B》2019,50(5):2121-2133
Metallurgical and Materials Transactions B - The planar laser-induced fluorescence (PLIF) technique was implemented to measure mixing time in a 1/17 water model of a 200-ton ladle furnace. The... 相似文献
89.
García-Peñalvo Francisco J. Moreno Lourdes 《Universal Access in the Information Society》2019,18(1):1-2
Universal Access in the Information Society - 相似文献
90.
Dr. Eduarda Mendes Enrico Cadoni Filipa Carneiro Dr. Marta B. Afonso Hugo Brito Dr. João Lavrado Dr. Daniel J. V. A. dos Santos Dr. Jorge B. Vítor Prof. Stephen Neidle Prof. Cecília M. P. Rodrigues Prof. Alexandra Paulo 《ChemMedChem》2019,14(14):1325-1328
Quadruplex nucleic acids are promising targets for cancer therapy. In this study we used a fragment-based approach to create new flexible G-quadruplex (G4) DNA-interactive small molecules with good calculated oral drug-like properties, based on quinoline and triazole heterocycles. G4 melting temperature and polymerase chain reaction (PCR)-stop assays showed that two of these compounds are selective G4 ligands, as they were able to induce and stabilize G4s in a dose- and DNA sequence-dependent manner. Molecular docking studies have suggested plausible quadruplex binding to both the G-quartet and groove, with the quinoline module playing the major role. Compounds were screened for cytotoxicity against four cancer cell lines, where 4,4′-(4,4′-(1,3-phenylene)bis(1H-1,2,3-triazole-4,1-diyl))bis(1-methylquinolin-1-ium) ( 1 d ) showed the greater activity. Importantly, dose–response curves show that 1 d is cytotoxic in the human colon cancer HT-29 cell line enriched in cancer stem-like cells, a subpopulation of cells implicated in chemoresistance. Overall, this study identified a new small molecule as a promising lead for the development of drugs targeting G4 in cancer stem cells. 相似文献