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331.
Rinta-Kanto JM Ouellette AJ Boyer GL Twiss MR Bridgeman TB Wilhelm SW 《Environmental science & technology》2005,39(11):4198-4205
In August of 2003 and August of 2004, blooms of potentially toxic cyanobacteria Microcystis spp. persisted in western Lake Erie. Samples collected from the bloom were analyzed for the cyanobacterial toxin microcystin and the presence of Microcystis spp. cells. Estimates of microcystin toxicity exceeding 1 microg L(-1) (microcystin-LR activity equivalents), the safety limit set by the World Health Organization, were found from the samples in both 2003 and 2004. The presence of Microcystis spp. in water samples was confirmed through standard polymerase chain reaction (PCR) using a combination of four primer sets. Quantification of Microcystis was accomplished by a real-time PCR assay utilizing specific primer-Taq-man probe sets targeted on a conserved, Microcystis-specific 16S rDNA fragment and a microcystin toxin synthetase gene mcyD. This approach allowed us to specifically study the distribution and abundance of toxic Microcystis in the lake in contrast to previous studies that have assessed Microcystis populations with less refined methods. On the basis of quantification by quantitative real-time PCR analysis, the total abundance of Microcystis cells in the bloom area varied from 4 x 10(8) to 2 x 10(3) cells L(-1). The results of this study provide novel insight regarding the distribution and abundance of Microcystis spp. in the western basin of Lake Erie, a region plagued in recent years by large-scale (>20 km2) blooms. Our results suggest that the Maumee River and Bay may serve as a source for Microcystis to western and central Lake Erie. 相似文献
332.
The Mycobacterium tuberculosis complex is associated with a remarkably low level of structural gene polymorphism. As part of a search for alternative forms of genetic variation that may act as a source of biological diversity in M. tuberculosis, we have identified a region of the genome that is highly variable amongst a panel of unrelated clinical isolates. Fifteen of 24 isolates examined contained one or more copies of the M. tuberculosis-specific IS6110 insertion element within this 20 kb variable region. In nine of the isolates, including the laboratory-passaged strain H37Rv, genomic deletions were identified, resulting in loss of between two and 13 genes. In each case, deletions were associated with the presence of a copy of the IS6110 element. Absence of flanking tri- or tetra-nucleotide repeats identified homologous recombination between adjacent IS6110 elements as the most likely mechanism of the deletion events. IS6110 insertion into hot-spots within the genome of M. tuberculosis provides a mechanism for generation of genetic diversity involving a high frequency of insertions and deletions. 相似文献
333.
R Bahreini AM Middlebrook CA Brock JA de Gouw SA McKeen LR Williams KE Daumit AT Lambe P Massoli MR Canagaratna R Ahmadov AJ Carrasquillo ES Cross B Ervens JS Holloway JF Hunter TB Onasch IB Pollack JM Roberts TB Ryerson C Warneke P Davidovits DR Worsnop JH Kroll 《Environmental science & technology》2012,46(15):8025-8034
In June 2010, the NOAA WP-3D aircraft conducted two survey flights around the Deepwater Horizon (DWH) oil spill. The Gulf oil spill resulted in an isolated source of secondary organic aerosol (SOA) precursors in a relatively clean environment. Measurements of aerosol composition and volatile organic species (VOCs) indicated formation of SOA from intermediate-volatility organic compounds (IVOCs) downwind of the oil spill (Science2011, 331, doi 10.1126/science.1200320). In an effort to better understand formation of SOA in this environment, we present mass spectral characteristics of SOA in the Gulf and of SOA formed in the laboratory from evaporated light crude oil. Compared to urban primary organic aerosol, high-mass-resolution analysis of the background-subtracted SOA spectra in the Gulf (for short, "Gulf SOA") showed higher contribution of C(x)H(y)O(+) relative to C(x)H(y)(+) fragments at the same nominal mass. In each transect downwind of the DWH spill site, a gradient in the degree of oxidation of the Gulf SOA was observed: more oxidized SOA (oxygen/carbon = O/C ~0.4) was observed in the area impacted by fresher oil; less oxidized SOA (O/C ~0.3), with contribution from fragments with a hydrocarbon backbone, was found in a broader region of more-aged surface oil. Furthermore, in the plumes originating from the more-aged oil, contribution of oxygenated fragments to SOA decreased with downwind distance. Despite differences between experimental conditions in the laboratory and the ambient environment, mass spectra of SOA formed from gas-phase oxidation of crude oil by OH radicals in a smog chamber and a flow tube reactor strongly resembled the mass spectra of Gulf SOA (r(2) > 0.94). Processes that led to the observed Gulf SOA characteristics are also likely to occur in polluted regions where VOCs and IVOCs are coemitted. 相似文献
334.
Huang YH Leamon TB Courtney TK Chen PY DeArmond S 《Accident; analysis and prevention》2011,43(1):1-10
This study, through a random national survey in the U.S., explored how corporate financial decision-makers perceive important workplace safety issues as a function of the size of the company for which they worked (medium- vs. large-size companies). Telephone surveys were conducted with 404 U.S. corporate financial decision-makers: 203 from medium-size companies and 201 from large companies. Results showed that the patterns of responding for participants from medium- and large-size companies were somewhat similar. The top-rated safety priorities in resource allocation reported by participants from both groups were overexertion, repetitive motion, and bodily reaction. They believed that there were direct and indirect costs associated with workplace injuries and for every dollar spent improving workplace safety, more than four dollars would be returned. They perceived the top benefits of an effective safety program to be predominately financial in nature – increased productivity and reduced costs – and the safety modification participants mentioned most often was to have more/better safety-focused training. However, more participants from large- than medium-size companies reported that “falling on the same level” was the major cause of workers’ compensation loss, which is in line with industry loss data. Participants from large companies were more likely to see their safety programs as better than those of other companies in their industries, and those of medium-size companies were more likely to mention that there were no improvements needed for their companies. 相似文献
335.
336.
△经过河南省制造业信息化工程专家组的评审和对企业的考察 ,鹤壁环燕轮胎有限责任公司被确定为河南省制造业信息化工程示范企业。环燕公司组织实施的CAD&ERP制造业信息化建设项目被列为 2 0 0 4年度河南省制造业信息化工程示范企业建设项目。根据《河南省“十五”制造业信息化工程的实施方案》 ,该项目将得到政府的扶植和资金支持。(鹤壁环燕轮胎有限责任公司 张领军供稿 ) △从 2 0 0 4年开始 ,汽车分类将采用新的国家标准 ,根据新的分类方法 ,汽车将分为商用车和乘用车两大类 ,不再有轿车的叫法以适应入世后新形势的需要。国标GB… 相似文献