全文获取类型
收费全文 | 86516篇 |
免费 | 1201篇 |
国内免费 | 410篇 |
专业分类
电工技术 | 810篇 |
综合类 | 2340篇 |
化学工业 | 12189篇 |
金属工艺 | 4826篇 |
机械仪表 | 3082篇 |
建筑科学 | 2378篇 |
矿业工程 | 569篇 |
能源动力 | 1175篇 |
轻工业 | 3761篇 |
水利工程 | 1281篇 |
石油天然气 | 342篇 |
无线电 | 9460篇 |
一般工业技术 | 16910篇 |
冶金工业 | 2765篇 |
原子能技术 | 283篇 |
自动化技术 | 25956篇 |
出版年
2023年 | 54篇 |
2022年 | 24篇 |
2021年 | 131篇 |
2020年 | 111篇 |
2019年 | 121篇 |
2018年 | 14527篇 |
2017年 | 13454篇 |
2016年 | 10062篇 |
2015年 | 715篇 |
2014年 | 409篇 |
2013年 | 407篇 |
2012年 | 3342篇 |
2011年 | 9667篇 |
2010年 | 8451篇 |
2009年 | 5699篇 |
2008年 | 6942篇 |
2007年 | 7915篇 |
2006年 | 250篇 |
2005年 | 1316篇 |
2004年 | 1194篇 |
2003年 | 1229篇 |
2002年 | 594篇 |
2001年 | 126篇 |
2000年 | 199篇 |
1999年 | 94篇 |
1998年 | 92篇 |
1997年 | 51篇 |
1996年 | 64篇 |
1995年 | 36篇 |
1994年 | 27篇 |
1993年 | 30篇 |
1992年 | 26篇 |
1991年 | 38篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 45篇 |
1965年 | 45篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34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 46 毫秒
1.
Jennie O'Loughlin Silvia Napolitano Fahad Alkhathami Cillian O'Beirne Daniel Marhöfer Megan O'Shaughnessy Prof. Orla Howe Prof. Matthias Tacke Dr. Marina Rubini 《Chembiochem : a European journal of chemical biology》2021,22(6):1093-1098
Antibiotic resistance is a growing problem for public health and associated with increasing economic costs and mortality rates. Silver and silver-related compounds have been used for centuries due to their antimicrobial properties. In this work, we show that 1,3-dibenzyl-4,5-diphenyl-imidazol-2-ylidene silver(I) acetate/NHC*-Ag-OAc (SBC3) is a reversible, high affinity inhibitor of E. coli thioredoxin reductase (TrxR; Ki=10.8±1.2 nM). Minimal inhibition concentration (MIC) tests with different E. coli and P. aeruginosa strains demonstrated that SBC3 can efficiently inhibit bacterial cell growth, especially in combination with established antibiotics like gentamicin. Our results show that SBC3 is a promising antibiotic drug candidate targeting bacterial TrxR. 相似文献
2.
The design of a liquid/liquid contact apparatus necessitates the knowledge of fluid dynamics and mass transfer in the dispersion. Prediction of process parameters is challenging due to swarm and interfacial effects. Single drop investigations are suitable to enable a sophisticated dimensioning based on few simple experiments combined with published theories and correlations. In the first part of this article, the fundamentals of fluid dynamics and mass transfer in absence of interfacial effects were explained. Here, an overview of relevant interfacial phenomena and the influence of different substances typically occurring in technical applications as impurities or accompanying components is given. 相似文献
3.
Forschung im Ingenieurwesen - Zur Übertragung von Drehmoment und Drehzahl in beliebiger Achsanordnung eignen sich bei kleinem Achswinkel bis 30° Beveloidverzahnungen. Besonders... 相似文献
4.
Tilman Sauter Karl Kratz Samy Madbouly Frank Klein Matthias Heuchel Andreas Lendlein 《大分子材料与工程》2021,306(4):2000730
Isotropic and anisotropic shape-memory polymer foams are prepared by supercritical carbon dioxide foaming from a multiblock copolymer (PDLCL) consisting of poly(ω-pentadecalactone) and poly(ε-caprolactone) segments. Analysis by micro-computed tomography reveals for the anisotropic PDLCL foam cells a high shape anisotropy ratio of R = 1.72 ± 0.62 with a corresponding Young's compression moduli ratio between longitudinal and transversal direction of 4.3. The experimental compression data in the linear elastic range can be well described by the anisotropic open foam model of Gibson and Ashby. A micro-morphological analysis for single pores using scanning electron microscopy images permits the correlation between the macroscopic stress-compression behavior and microscale structural changes. 相似文献
5.
Dr. Barbara Wienen-Schmidt Matthias Oebbeke Dr. Khang Ngo Prof. Dr. Andreas Heine Prof. Dr. Gerhard Klebe 《ChemMedChem》2021,16(1):292-300
In lead optimization, protein crystallography is an indispensable tool to analyze drug binding. Binding modes and non-covalent interaction inventories are essential to design follow-up synthesis candidates. Two protocols are commonly applied to produce protein–ligand complexes: cocrystallization and soaking. Because of its time and cost effectiveness, soaking is the more popular method. Taking eight ligand hinge binders of protein kinase A, we demonstrate that cocrystallization is superior. Particularly for flexible proteins, such as kinases, and larger ligands cocrystallization captures more reliable the correct binding pose and induced protein adaptations. The geometrical discrepancies between soaking and cocrystallization appear smaller for fragment-sized ligands. For larger flexible ligands that trigger conformational changes of the protein, soaking can be misleading and underestimates the number of possible polar interactions due to inadequate, highly impaired positions of protein amino-acid side and main chain atoms. Thus, if applicable cocrystallization should be the gold standard to study protein–ligand complexes. 相似文献
6.
Christian Gentzsch Dr. Matthias Hoffmann Dr. Yasuhiro Ohshima Naoko Nose Dr. Xinyu Chen Prof. Dr. Takahiro Higuchi Prof. Dr. Michael Decker 《ChemMedChem》2021,16(9):1427-1437
The enzyme butyrylcholinesterase (BChE) represents a promising target for imaging probes to potentially enable early diagnosis of neurodegenerative diseases like Alzheimer's disease (AD) and to monitor disease progression in some forms of cancer. In this study, we present the design, facile synthesis, in vitro and preliminary ex vivo and in vivo evaluation of a morpholine-based, selective inhibitor of human BChE as a positron emission tomography (PET) tracer with a pseudo-irreversible binding mode. We demonstrate a novel protecting group strategy for 18F radiolabeling of carbamate precursors and show that the inhibitory potency as well as kinetic properties of our unlabeled reference compound were retained in comparison to the parent compound. In particular, the prolonged duration of enzyme inhibition of such a morpholinocarbamate motivated us to design a PET tracer, possibly enabling a precise mapping of BChE distribution. 相似文献
7.
Dr. Simon Schramm Luca Agnetta Dr. Marcel Bermudez Hubert Gerwe Matthias Irmen Dr. Janine Holze Dr. Timo Littmann Prof. Gerhard Wolber Dr. Christian Tränkle Prof. Michael Decker 《ChemMedChem》2019,14(14):1349-1358
Recently, investigations of the complex mechanisms of allostery have led to a deeper understanding of G protein-coupled receptor (GPCR) activation and signaling processes. In this context, muscarinic acetylcholine receptors (mAChRs) are highly relevant due to their exemplary role in the study of allosteric modulation. In this work, we compare and discuss two sets of putatively dualsteric ligands, which were designed to connect carbachol to different types of allosteric ligands. We chose derivatives of TBPB [1-(1′-(2-tolyl)-1,4′-bipiperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one] as M1-selective putative bitopic ligands, and derivatives of benzyl quinolone carboxylic acid (BQCA) as an M1 positive allosteric modulator, varying the distance between the allosteric and orthosteric building blocks. Luciferase protein complementation assays demonstrated that linker length must be carefully chosen to yield either agonist or antagonist behavior. These findings may help to design biased signaling and/or different extents of efficacy. 相似文献
8.
Yavuz Emre Arslan Yusuf Furkan Galata Tugba Sezgin Arslan Burak Derkus 《Journal of materials science. Materials in medicine》2018,29(8):127
In this study, we aimed at fabricating decellularized bovine myocardial extracellular matrix-based films (dMEbF) for cardiac tissue engineering (CTE). The decellularization process was carried out utilizing four consecutive stages including hypotonic treatment, detergent treatment, enzymatic digestion and decontamination, respectively. In order to fabricate the dMEbF, dBM were digested with pepsin and gelation process was conducted. dMEbF were then crosslinked with N-hydroxysuccinimide/1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (NHS/EDC) to increase their durability. Nuclear contents of native BM and decellularized BM (dBM) tissues were determined with DNA content analysis and agarose-gel electrophoresis. Cell viability on dMEbF for 3rd, 7th, and 14th days was assessed by MTT assay. Cell attachment on dMEbF was also studied by scanning electron microscopy. Trans-differentiation capacity of human adipose-derived mesenchymal stem cells (hAMSCs) into cardiomyocyte-like cells on dMEbF were also evaluated by histochemical and immunohistochemical analyses. DNA contents for native and dBM were, respectively, found as 886.11?±?164.85 and 47.66?±?0.09?ng/mg dry weight, indicating a successful decellularization process. The results of glycosaminoglycan and hydroxyproline assay, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), performed in order to characterize the extracellular matrix (ECM) composition of native and dBM tissue, showed that the BM matrix was not damaged during the proposed method. Lastly, regarding the histological study, dMEbF not only mimics native ECM, but also induces the stem cells into cardiomyocyte-like cells phenotype which brings it the potential of use in CTE. 相似文献
9.
10.
Jamasb Pirkandi Mehdi Jahromi Seyedeh Zeynab Sajadi Mohammad Ommian 《Clean Technologies and Environmental Policy》2018,20(5):1047-1060
In this study, three different configurations of a solid oxide fuel cell and gas microturbine hybrid system are evaluated for application in auxiliary power units. The first configuration is a common hybrid system in auxiliary power units, utilizing a fuel cell stack in the structure of the gas turbine cycle. The other configurations use two series and parallel fuel cell stacks in the structure of the gas turbine cycle. The main purpose of this research is thermodynamic analysis, evaluation of the performance of the proposed hybrid systems in similar conditions, and selection of an appropriate system in terms of efficiency, power generation, and entropy generation rate. In this study, the utilized fuel cells were subjected to electrochemical, thermodynamic, and thermal analyses and their working temperatures were calculated under various working conditions. Results indicate that the hybrid system with two series stacks had maximum power generation and efficiency compared with the other two cases. Moreover, the simple hybrid system and the system with two parallel stacks had relatively equal pure power generation and efficiency. According to the investigations, hybrid system with two series fuel cell stacks, which had 3424 and 1712 cells, respectively, can achieve the electrical efficiency of over 48%. A hybrid system with two parallel fuel cell stacks, in which each stack had 2568 cells, had the electrical efficiency of 46.3%. Findings suggested that maximum electrical efficiency occurred between the pressure ratios of 5–6 in the proposed hybrid systems. 相似文献