全文获取类型
收费全文 | 579篇 |
免费 | 63篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 247篇 |
金属工艺 | 8篇 |
机械仪表 | 13篇 |
建筑科学 | 25篇 |
矿业工程 | 1篇 |
能源动力 | 19篇 |
轻工业 | 105篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 29篇 |
一般工业技术 | 94篇 |
冶金工业 | 28篇 |
原子能技术 | 1篇 |
自动化技术 | 66篇 |
出版年
2023年 | 11篇 |
2022年 | 25篇 |
2021年 | 71篇 |
2020年 | 20篇 |
2019年 | 28篇 |
2018年 | 28篇 |
2017年 | 30篇 |
2016年 | 40篇 |
2015年 | 26篇 |
2014年 | 28篇 |
2013年 | 46篇 |
2012年 | 47篇 |
2011年 | 43篇 |
2010年 | 43篇 |
2009年 | 36篇 |
2008年 | 33篇 |
2007年 | 16篇 |
2006年 | 17篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
排序方式: 共有645条查询结果,搜索用时 31 毫秒
21.
Immigration and Construction: The Makeup of the Workforce in the Washington, D.C., Metropolitan Area
There are an estimated 11 million illegal immigrants currently residing in the United States. Of this population, research shows that approximately 19% work in the construction industry, comprising around 14% of all construction workforces. The Washington, D.C. metropolitan region has a unique makeup of workforces within the construction industry. Between September 2006 and February 2007, 896 construction workers from several projects in the Washington, D.C. metropolitan area participated in a survey. The study targeted the low-skilled, immigrant-saturated trades in construction. The most compelling finding in this study was that illegal immigrants make up a far greater proportion of the construction workers in low-skilled trades than indicated by national averages, 55% as compared to between 20 and 36% nationally. This will increase the impact of immigration and immigration reform substantially for the Washington, D.C. metropolitan. 相似文献
22.
Mechanistic Insights into Cyclic Peptide Generation by DnaE Split-Inteins through Quantitative and Structural Investigation 下载免费PDF全文
Leonhard M. Kick Dr. Sabrina Harteis Dr. Maximilian F. Koch Dr. Sabine Schneider 《Chembiochem : a European journal of chemical biology》2017,18(22):2242-2246
Inteins carry out protein-splicing reactions, which are used in protein chemistry, protein engineering and biotechnological applications. Rearrangement of the order of the domains in split-inteins results in head-to-tail cyclisation of the target sequence, which can be used for genetic encoding and expression of libraries of cyclic peptides (CPs). The efficiency of the splicing reaction depends on the target sequence. Here we used mass spectrometry to assess in vivo cyclic peptide formation from different hexameric target sequences by the DnaE split-inteins from Synechocystis sp. and Nostoc punctiforme, revealing a strong impact of the target sequence and of the intein on the intracellular peptide concentration. Furthermore, we determined the crystal structures of their pre-splicing complexes, which allowed us to identify F-block Asp17 as crucial for the DnaE-mediated splicing reaction. 相似文献
23.
Sabrina Reich Dr. Hans Wolfgang Hoeffken Dr. Bettina Rosche Dr. Bettina M. Nestl Prof. Dr. Bernhard Hauer 《Chembiochem : a European journal of chemical biology》2012,13(16):2400-2407
The crystal structure of the “ene” nicotinamide‐dependent cyclohexenone reductase (NCR) from Zymomonas mobilis (PDB ID: 4A3U) has been determined in complex with acetate ion, FMN, and nicotinamide, to a resolution of 1.95 Å. To study the activity and enantioselectivity of this enzyme in the bioreduction of activated α,β‐unsaturated alkenes, the rational design methods site‐ and loop‐directed mutagenesis were applied. Based on a multiple sequence alignment of various members of the Old Yellow Enzyme family, eight single‐residue variants were generated and investigated in asymmetric bioreduction. Furthermore, a structural alignment of various ene reductases predicted four surface loop regions that are located near the entrance of the active site. Four NCR loop variants, derived from loop‐swapping experiments with OYE1 from Saccharomyces pastorianus, were analysed for bioreduction. The three enzyme variants, P245Q, D337Y and F314Y, displayed increased activity compared to wild‐type NCR towards the set of substrates tested. The active‐site mutation Y177A demonstrated a clear influence on the enantioselectivity. The loop‐swapping variants retained reduction efficiency, but demonstrated decreased enzyme activity compared with the wild‐type NCR ene reductase enzyme. 相似文献
24.
Butler Stephen F.; Newman Frederick L.; Cacciola John S.; Frank Arlene; Budman Simon H.; McLellan A. Thomas; Ford Sabrina; Blaine Jack; Gastfriend David; Moras Karla; Salloum Ihsan M.; Barber Jacques P. 《Canadian Metallurgical Quarterly》1998,10(4):399
The Addiction Severity Index (ASI) is a reliable and valid measure of problem severity among addicted patients. Concerns have been raised about the reliability of the Interviewer Severity Rating (ISR), a summary score for each of 7 domains. As part of an effort to build a computer-administered ASI, regression equations were developed to predict the ISR. Repeated resampling of a large dataset, consisting of 1,124 ASIs conducted by trained interviewers, permitted derivation of stable regression equations predicting the ISR for each ASI domain from patients' answers to preselected interview items. The resulting 7 Predicted Severity Ratings (PSRs) were tested on 8, standardized vignettes, with "gold standard," expert-generated ISRs. Reliabilities compared well with those of intensively trained interviewers. The PSRs could provide an alternative to potentially unreliable interviewer ratings, enhancing the ASI's role in treatment planning and treatment matching and make possible a computer-administered version of the ASI. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
Frecer V Kabelác M De Nardi P Pricl S Miertus S 《Journal of molecular graphics & modelling》2004,22(3):209-220
We have designed small focused combinatorial library of hexapeptide inhibitors of NS3 serine protease of the hepatitis C virus (HCV) by structure-based molecular design complemented by combinatorial optimisation of the individual residues. Rational residue substitutions were guided by the structure and properties of the binding pockets of the enzyme's active site. The inhibitors were derived from peptides known to inhibit the NS3 serine protease by using unusual amino acids and alpha-ketocysteine or difluoroaminobutyric acid, which are known to bind to the S1 pocket of the catalytic site. Inhibition constants (Ki) of the designed library of inhibitors were predicted from a QSAR model that correlated experimental Ki of known peptidic inhibitors of NS3 with the enthalpies of enzyme-inhibitor interaction computed via molecular mechanics and the solvent effect contribution to the binding affinity derived from the continuum model of solvation. The library of the optimised inhibitors contains promising drug candidates-water-soluble anionic hexapeptides with predicted Ki* in the picomolar range. 相似文献
26.
Falcieri E Burattini S Bortul R Luchetti F Tabellini G Tazzari PL Cappellini A Cocco L Martelli AM 《Microscopy research and technique》2003,62(3):192-200
Two distinct types of cell death have been described: apoptosis and necrosis. However, it is becoming increasingly clear that the differences between these two types are far less numerous than initially thought. Morphological analyses might provide important information to distinguish apoptotic from necrotic samples. We recently reported that in necrotic, but not apoptotic, HL-60 human myeloid leukaemia cells, the nuclear protein topoisomerase IIalpha concentrated in nucleoli. In order to ascertain whether or not this phenomenon was restricted to a peculiar cell type or could be detected also in cells of lymphoid lineage, we performed an investigation aimed at defining the localization of topoisomerase IIalpha in apoptotic and necrotic Jurkat human T lymphoblastoid cells. Immunofluorescence staining demonstrated that topoisomerase IIalpha was excluded from the condensed chromatin of apoptotic cells, whereas in necrotic cells it was localized in discrete nuclear dots. Immuno-electron microscopy analysis showed that topoisomerase IIalpha was undetectable in nucleoli of normal and apoptotic cells, whereas it was present in the nucleolus of necrotic cells irrespectively of the type of inducer used (ethanol, H(2)O(2), HgCl(2)). Taken together, our findings identify topoisomerase IIalpha as a potential morphological marker useful to discriminate between apoptotic and necrotic cells. 相似文献
27.
28.
29.
It is widely accepted that corporate reputation plays an important role in determining the impact of crises on firms. Crises may erode corporate reputation. However, reputation may also attenuate the negative effects of crises. This study investigates how corporate reputation moderates the relationship between crisis occurrence and customer loyalty which is expected to decrease given a crisis. Drawing on opposing theories, namely dissonance theory and expectancy‐violation, we conduct a scenario experiment set in the airline industry. Results demonstrate that the moderating effect is weaker in the case of a favourable corporate reputation. This may indicate that a pre‐existing favourable reputation does not shield the firm from the negative effects of the crisis, but may rather present a liability because customers have higher expectations with regard to well‐reputed firms. Contrary to that, ill‐reputed firms have less to lose in the case of a crisis and suffer comparatively smaller decreases in customer loyalty. Marketing management might take into account the role of crisis and reputation management for customer bonding strategies while crisis management should recognize the importance of reputation effects in crises given their impact on customer loyalty and firm profitability. 相似文献
30.