全文获取类型
收费全文 | 4915篇 |
免费 | 309篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 61篇 |
综合类 | 1篇 |
化学工业 | 1408篇 |
金属工艺 | 141篇 |
机械仪表 | 78篇 |
建筑科学 | 152篇 |
矿业工程 | 17篇 |
能源动力 | 142篇 |
轻工业 | 647篇 |
水利工程 | 13篇 |
石油天然气 | 10篇 |
无线电 | 124篇 |
一般工业技术 | 792篇 |
冶金工业 | 1162篇 |
原子能技术 | 23篇 |
自动化技术 | 457篇 |
出版年
2023年 | 41篇 |
2022年 | 164篇 |
2021年 | 282篇 |
2020年 | 126篇 |
2019年 | 96篇 |
2018年 | 187篇 |
2017年 | 191篇 |
2016年 | 205篇 |
2015年 | 148篇 |
2014年 | 207篇 |
2013年 | 325篇 |
2012年 | 234篇 |
2011年 | 294篇 |
2010年 | 174篇 |
2009年 | 173篇 |
2008年 | 167篇 |
2007年 | 161篇 |
2006年 | 111篇 |
2005年 | 86篇 |
2004年 | 77篇 |
2003年 | 70篇 |
2002年 | 58篇 |
2001年 | 35篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 179篇 |
1997年 | 204篇 |
1996年 | 141篇 |
1995年 | 95篇 |
1994年 | 52篇 |
1993年 | 72篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 16篇 |
1984年 | 33篇 |
1983年 | 23篇 |
1982年 | 41篇 |
1981年 | 50篇 |
1980年 | 57篇 |
1979年 | 28篇 |
1978年 | 42篇 |
1977年 | 110篇 |
1976年 | 237篇 |
1975年 | 15篇 |
1973年 | 12篇 |
排序方式: 共有5228条查询结果,搜索用时 31 毫秒
51.
Measurements of the wetting contact angle for a marble surface were carried out for two systems: dry marble plate-water drop-saturated water vapour and marble wetted by water-water drop-dry air (in the presence of molecular sieves). The marble plate was placed in a measuring chamber and contact angles were measured after different lengths of time; it was found that their values grew to a maximum which was reached after about 30 min. It was found that when the dry marble plate was placed in saturated water vapour for 24 h the contact angle decreased in comparison with its maximal value. To explain the results obtained, theoretical calculations were made. The theoretical calculations and measurements showed that it was possible to obtain a contact angle greater than zero on a marble surface, depending on the structure and thickness of the water film. 相似文献
52.
Karolina Bukowska-Strakova Joanna Wodek Ewelina Pitera Magdalena Kozakowska Anna Konturek-Ciela Maciej Ciela Monika Goka Witold Nowak Aleksandra Wieczorek Katarzyna Pawiska-Wsikowska Alicja Jzkowicz Maciej Siedlar 《International journal of molecular sciences》2021,22(3)
Whilst the survival rates of childhood acute lymphoblastic leukemia (ALL) have increased remarkably over the last decades, the therapy resistance and toxicity are still the major causes of treatment failure. It was shown that overexpression of heme oxygenase-1 (HO-1) promotes proliferation and chemoresistance of cancer cells. In humans, the HO-1 gene (HMOX1) expression is modulated by two polymorphisms in the promoter region: (GT)n-length polymorphism and single-nucleotide polymorphism (SNP) A(−413)T, with short GT repeat sequences and 413-A variants linked to an increased HO-1 inducibility. We found that the short alleles are significantly more frequent in ALL patients in comparison to the control group, and that their presence may be associated with a higher risk of treatment failure, reflecting the role of HO-1 in chemoresistance. We also observed that the presence of short alleles may predispose to develop chemotherapy-induced neutropenia. In case of SNP, the 413-T variant co-segregated with short or long alleles, while 413-A almost selectively co-segregated with long alleles, hence it is not possible to determine if SNPs are actually of phenotypic significance. Our results suggest that HO-1 can be a potential target to overcome the treatment failure in ALL patients. 相似文献
53.
Joanna Gruszczynska-Biegala Andrzej Stefan Andrzej A. Kasprzak Piotr Dobryszycki Sofia Khaitlina Hanna Strzelecka-Goaszewska 《International journal of molecular sciences》2021,22(5)
Formation of stable actin filaments, critically important for actin functions, is determined by the ionic strength of the solution. However, not much is known about the elements of the actin fold involved in ionic-strength-dependent filament stabilization. In this work, F-actin was destabilized by Cu2+ binding to Cys374, and the effects of solvent conditions on the dynamic properties of F-actin were correlated with the involvement of Segment 227-235 in filament stabilization. The results of our work show that the presence of Mg2+ at the high-affinity cation binding site of Cu-modified actin polymerized with MgCl2 strongly enhances the rate of filament subunit exchange and promotes the filament instability. In the presence of 0.1 M KCl, the filament subunit exchange was 2–3-fold lower than that in the MgCl2-polymerized F-actin. This effect correlates with the reduced accessibility of the D-loop and Segment 227-235 on opposite filament strands, consistent with an ionic-strength-dependent conformational change that modulates involvement of Segment 227-235 in stabilization of the intermonomer interface. KCl may restrict the mobility of the α-helix encompassing part of Segment 227-235 and/or be bound to Asp236 at the boundary of Segment 227-235. These results provide experimental evidence for the involvement of Segment 227-235 in salt-induced stabilization of contacts within the actin filament and suggest that they can be weakened by mutations characteristic of actin-associated myopathies. 相似文献
54.
Marta Krychowiak-Manicka Mirosawa Krauze-Baranowska Sylwia Godlewska Zbigniew Kaczyski Aleksandra Bielicka-Giedo Natalia Grzegorczyk Magdalena Narajczyk Joanna E. Frackowiak Aleksandra Krolicka 《International journal of molecular sciences》2021,22(9)
Carnivorous plants are exemplary natural sources of secondary metabolites with biological activity. However, the therapeutic antimicrobial potential of these compounds is limited due to intrinsic resistance of selected bacterial pathogens, among which Pseudomonas aeruginosa represents an extreme example. The objective of the study was to overcome the intrinsic resistance of P. aeruginosa by combining silver nanoparticles (AgNPs) with secondary metabolites from selected carnivorous plant species. We employed the broth microdilution method, the checkerboard titration technique and comprehensive phytochemical analyses to define interactions between nanoparticles and active compounds from carnivorous plants. It has been confirmed that P. aeruginosa is resistant to a broad range of secondary metabolites from carnivorous plants, i.e., naphthoquinones, flavonoids, phenolic acids (MBC = 512 µg mL−1) and only weakly sensitive to their mixtures, i.e., extracts and extracts’ fractions. However, it was shown that the antimicrobial activity of extracts and fractions with a significant level of naphthoquinone (plumbagin) was significantly enhanced by AgNPs. Our studies clearly demonstrated a crucial role of naphthoquinones in AgNPs and extract interaction, as well as depicted the potential of AgNPs to restore the bactericidal activity of naphthoquinones towards P. aeruginosa. Our findings indicate the significant potential of nanoparticles to modulate the activity of selected secondary metabolites and revisit their antimicrobial potential towards human pathogenic bacteria. 相似文献
55.
Ewa ya Katarzyna Dziendzikowska Dariusz Kamola Jacek Wilczak Rafa Sapierzyski Joanna Harasym Joanna Gromadzka-Ostrowska 《International journal of molecular sciences》2021,22(9)
Background: The incidence of Crohn’s disease (CD) is increasing worldwide, and it has currently become a serious public health issue in society. The treatment of CD continues throughout a patient’s lifetime, and therefore, it is necessary to develop new, effective treatment methods, including dietotherapy. The present study aimed to determine the effects of consumption of oat beta-glucans with different molar mass on colon inflammation (colitis) in the early stages of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced CD in an animal model. Methods: Sprague–Dawley rats (control and TNBS-induced CD) were divided into three dietary groups and fed for 3 days (reflecting acute inflammation) or 7 days (reflecting remission) with a feed containing 1% low (βGl) or high (βGh) molar mass oat beta-glucan or a feed without this polysaccharide. The level of colon inflammatory markers and the expression of cytokines and their receptor genes were measured by ELISA and RT-PCR methods, respectively. Results: Acute inflammation or remission (3 or 7 days after TNBS administration, respectively) stages of experimentally induced CD were characterized by an increase in the level of inflammatory markers (IL-1, IL-6, IL-10, IL-12, TNF-α, CRP, MPO, COX, and PGE2) and the disruption of some cytokine signaling pathways as well as macro- and microscopic changes of colon tissue. The consumption of oat beta-glucans reduced the level of inflammatory markers and recovered the signaling pathways and histological changes, with stronger effects of βGl after 7 days of colitis. Conclusions: Dietary oat beta-glucans can reduce colitis at the molecular and organ level and accelerate CD remission. 相似文献
56.
Joanna Czajkowska Adam Junka Jakub Hoppe Monika Toporkiewicz Andrzej Pawlak Pawe Migda Monika Oleksy-Wawrzyniak Karol Fijakowski Marcin
miglak Agata Markowska-Szczupak 《International journal of molecular sciences》2021,22(11)
Staphylococcus aureus is one of the most prevalent pathogens associated with several types of biofilm-based infections, including infections of chronic wounds. Mature staphylococcal biofilm is extremely hard to eradicate from a wound and displays a high tendency to induce recurring infections. Therefore, in the present study, we aimed to investigate in vitro the interaction between S. aureus biofilm and fibroblast cells searching for metabolites that could be considered as potential biomarkers of critical colonization and infection. Utilizing advanced microscopy and microbiological methods to examine biofilm formation and the staphylococcal infection process, we were able to distinguish 4 phases of biofilm development. The analysis of staphylococcal biofilm influence on the viability of fibroblasts allowed us to pinpoint the moment of critical colonization—12 h post contamination. Based on the obtained model we performed a metabolomics analysis by 1H NMR spectroscopy to provide new insights into the pathophysiology of infection. We identified a set of metabolites related to the switch to anaerobic metabolism that was characteristic for staphylococcal biofilm co-cultured with fibroblast cells. The data presented in this study may be thus considered a noteworthy but preliminary step in the direction of developing a new, NMR-based tool for rapid diagnosing of infection in a chronic wound. 相似文献
57.
Izabela Perkowska Marta Potrykus Joanna Siwinska Dominika Siudem Ewa Lojkowska Anna Ihnatowicz 《International journal of molecular sciences》2021,22(12)
Coumarins belong to a group of secondary metabolites well known for their high biological activities including antibacterial and antifungal properties. Recently, an important role of coumarins in plant resistance to pathogens and their release into the rhizosphere upon pathogen infection was discovered. It is also well documented that coumarins play a crucial role in the Arabidopsis thaliana growth under Fe-limited conditions. However, the mechanisms underlying interplay between plant resistance, accumulation of coumarins and Fe status, remain largely unknown. In this work, we investigated the effect of both mentioned factors on the disease severity using the model system of Arabidopsis/Dickeya spp. molecular interactions. We evaluated the disease symptoms in Arabidopsis plants, wild-type Col-0 and its mutants defective in coumarin accumulation, grown in hydroponic cultures with contrasting Fe regimes and in soil mixes. Under all tested conditions, Arabidopsis plants inoculated with Dickeya solani IFB0099 strain developed more severe disease symptoms compared to lines inoculated with Dickeya dadantii 3937. We also showed that the expression of genes encoding plant stress markers were strongly affected by D. solani IFB0099 infection. Interestingly, the response of plants to D. dadantii 3937 infection was genotype-dependent in Fe-deficient hydroponic solution. 相似文献
58.
Microstructure and Mechanical Properties of the Ductile Al–Ti–Mo–Nb–V Refractory High Entropy Alloys
Cieślak Grzegorz Dąbrowa Juliusz Jawańska Monika Parzuchowska Agnieszka Oleszak Dariusz 《Metallurgical and Materials Transactions A》2022,53(2):653-662
Metallurgical and Materials Transactions A - A number of non-equimolar refractory high entropy alloys (RF HEAs) from the Al–Ti–Mo–Nb–V system are synthesized, with the... 相似文献
59.
Rémy Belmonte Petr A. Golovach Pinar Heggernes Pim van ’t Hof Marcin Kamiński Daniël Paulusma 《Algorithmica》2014,69(3):501-521
The Contractibility problem takes as input two graphs G and H, and the task is to decide whether H can be obtained from G by a sequence of edge contractions. The Induced Minor and Induced Topological Minor problems are similar, but the first allows both edge contractions and vertex deletions, whereas the latter allows only vertex deletions and vertex dissolutions. All three problems are NP-complete, even for certain fixed graphs H. We show that these problems can be solved in polynomial time for every fixed H when the input graph G is chordal. Our results can be considered tight, since these problems are known to be W[1]-hard on chordal graphs when parameterized by the size of H. To solve Contractibility and Induced Minor, we define and use a generalization of the classic Disjoint Paths problem, where we require the vertices of each of the k paths to be chosen from a specified set. We prove that this variant is NP-complete even when k=2, but that it is polynomial-time solvable on chordal graphs for every fixed k. Our algorithm for Induced Topological Minor is based on another generalization of Disjoint Paths called Induced Disjoint Paths, where the vertices from different paths may no longer be adjacent. We show that this problem, which is known to be NP-complete when k=2, can be solved in polynomial time on chordal graphs even when k is part of the input. Our results fit into the general framework of graph containment problems, where the aim is to decide whether a graph can be modified into another graph by a sequence of specified graph operations. Allowing combinations of the four well-known operations edge deletion, edge contraction, vertex deletion, and vertex dissolution results in the following ten containment relations: (induced) minor, (induced) topological minor, (induced) subgraph, (induced) spanning subgraph, dissolution, and contraction. Our results, combined with existing results, settle the complexity of each of the ten corresponding containment problems on chordal graphs. 相似文献
60.
Piotr Hońko 《国际智能系统杂志》2014,29(5):407-438
One of the popular methods to develop an algorithm for mining data stored in a relational structure is to upgrade an existing attribute‐value algorithm to a relational case. Current approaches to this problem have some shortcomings such as (1) a dependence on the upgrading process of the algorithm to be extended, (2) complicated redefinitions of crucial notions (e.g., pattern generality, pattern refinement), and (3) a tolerant limitation of the search space for pattern discovery. In this paper, we propose and evaluate a general methodology for upgrading a data mining framework to a relational case. This methodology is defined in a granular computing environment. Thanks to our relational extension of a granular computing based data mining framework, the three above problems can be overcome. 相似文献