全文获取类型
收费全文 | 5982篇 |
免费 | 235篇 |
国内免费 | 44篇 |
专业分类
电工技术 | 106篇 |
综合类 | 79篇 |
化学工业 | 1085篇 |
金属工艺 | 82篇 |
机械仪表 | 145篇 |
建筑科学 | 224篇 |
矿业工程 | 13篇 |
能源动力 | 113篇 |
轻工业 | 2082篇 |
水利工程 | 50篇 |
石油天然气 | 54篇 |
武器工业 | 5篇 |
无线电 | 580篇 |
一般工业技术 | 842篇 |
冶金工业 | 260篇 |
原子能技术 | 25篇 |
自动化技术 | 516篇 |
出版年
2023年 | 91篇 |
2022年 | 158篇 |
2021年 | 263篇 |
2020年 | 167篇 |
2019年 | 133篇 |
2018年 | 184篇 |
2017年 | 134篇 |
2016年 | 214篇 |
2015年 | 112篇 |
2014年 | 173篇 |
2013年 | 237篇 |
2012年 | 218篇 |
2011年 | 232篇 |
2010年 | 200篇 |
2009年 | 167篇 |
2008年 | 165篇 |
2007年 | 153篇 |
2006年 | 143篇 |
2005年 | 94篇 |
2004年 | 109篇 |
2003年 | 109篇 |
2002年 | 111篇 |
2001年 | 71篇 |
2000年 | 66篇 |
1999年 | 72篇 |
1998年 | 116篇 |
1997年 | 75篇 |
1996年 | 66篇 |
1995年 | 66篇 |
1994年 | 74篇 |
1993年 | 55篇 |
1992年 | 38篇 |
1919年 | 35篇 |
1917年 | 48篇 |
1916年 | 78篇 |
1915年 | 88篇 |
1914年 | 54篇 |
1913年 | 61篇 |
1912年 | 82篇 |
1911年 | 84篇 |
1910年 | 94篇 |
1909年 | 97篇 |
1908年 | 102篇 |
1907年 | 101篇 |
1906年 | 94篇 |
1905年 | 118篇 |
1904年 | 150篇 |
1903年 | 94篇 |
1902年 | 65篇 |
1901年 | 74篇 |
排序方式: 共有6261条查询结果,搜索用时 15 毫秒
991.
Mai Thi Nguyen 《Journal of the American Planning Association. American Planning Association》2014,80(4):385-396
Problem, research strategy, and findings: Immigrants suffer disproportionately from disasters because they have limited capacity to prepare for, respond to, or recover from a disaster. Unfortunately, planners and emergency managers are often inadequately trained or educated about the unique sociocultural needs and assets among immigrant groups. Hurricane Katrina exposed challenges to long-term recovery among Southeast Asian immigrants in Bayou La Batre (AL). We employ qualitative research methods, including in-depth interviews, focus groups with immigrants, and site visits, to better understand the barriers to disaster recovery and to inform local, state, federal, and nongovernmental agencies on how to better prepare disaster plans that would improve disaster recovery for multiethnic, multicultural, immigrant populations. We find four significant categories of sociocultural barriers to disaster recovery for Southeast Asian immigrants in Bayou La Batre: 1) language, literacy, and communication; 2) cultural differences in help-seeking; 3) inability to navigate the disaster recovery bureaucracy; and 4) and lack of leadership. Despite these barriers to recovery, immigrant groups can also teach us about resiliency in the face of disaster. The levels of trust, cooperation, and collaboration within the ethnic immigrant community help to buffer the damaging effects during the response and recovery period.Takeaway for practice: Our study reveals that cultural competency among staff members engaged in preparedness, response, and recovery is essential for an effective disaster recovery process. Furthermore, engaging immigrant groups in long-term recovery requires trust and relationship building prior to a disaster. In doing so, more culturally appropriate and effective disaster recovery plans can be developed. 相似文献
992.
993.
Antibiotic contamination and occurrence of antibiotic-resistant bacteria in aquatic environments of northern Vietnam 总被引:5,自引:0,他引:5
Hoa PT Managaki S Nakada N Takada H Shimizu A Anh DH Viet PH Suzuki S 《The Science of the total environment》2011,409(15):2894-2901
The ubiquitous application and release of antibiotics to the environment can result in bacterial antibiotic resistance, which in turn can be a serious risk to humans and other animals. Southeast Asian countries commonly apply an integrated recycling farm system called VAC (Vegetable, Aquaculture and Caged animal). In the VAC environment, antibiotics are released from animal and human origins, which would cause antibiotic-resistant bacteria (ARB). This study evaluated occurrence of ARB in the VAC environment in northern Vietnam, with quantitative analysis of antibiotic pollution. We found that sulfonamides were commonly detected at all sites. In dry season, while sulfamethazine was a major contaminant in pig farm pond (475-6662 ng/l) and less common in city canal and aquaculture sites, sulfamethoxazole was a major one in city canal (612-4330 ng/l). Erythromycin (154-2246 ng/l) and clarithromycin (2.8-778 ng/ml) were the common macrolides in city canal, but very low concentrations in pig farm pond and aquaculture sites. High frequencies of sulfamethoxazole-resistant bacteria (2.14-94.44%) were found whereas the occurrence rates of erythromycin-resistant bacteria were lower (< 0.01-38.8%). A positive correlation was found between sulfamethoxazole concentration and occurrence of sulfamethoxazole-resistant bacteria in dry season. The sulfamethoxazole-resistant isolates were found to belong to 25 genera. Acinetobacter and Aeromonas were the major genera. Twenty three of 25 genera contained sul genes. This study showed specific contamination patterns in city and VAC environments and concluded that ARB occurred not only within contaminated sites but also those less contaminated. Various species can obtain resistance in VAC environment, which would be reservoir of drug resistance genes. Occurrence of ARB is suggested to relate with rainfall condition and horizontal gene transfer in diverse microbial community. 相似文献
994.
大型污水泵站虹吸出水断流的试验研究 总被引:1,自引:0,他引:1
虹吸是在重力和大气压力下的一种水力现象 ,虹吸出水断流形式的优点是可以用体积及功率都很小的真空破坏阀来实现断流。通过对各种虹吸启动方式的试验 ,揭示了流态演变的机理 ,对虹吸出水系统的设计、建造和运行均有较高的实用价值。 相似文献
995.
Hien TT Nam PP Yasuhiro S Takayuki K Norimichi T Hiroshi B 《The Science of the total environment》2007,382(1):70-81
A comparative study of polycyclic aromatic hydrocarbons (PAHs) associated with particulate matter (TSP) in the ambient air in an urban area in Ho Chi Minh City, Vietnam and in Osaka, Japan was carried out from 2005 to 2006. The objective of this study was to investigate the environmental levels, emission sources, seasonal variations and health risk of eleven PAHs in the two cities, especially Ho Chi Minh City where air pollution is becoming a serious concern. The results showed that the concentrations of TSP and total PAHs were significantly higher in Ho Chi Minh City than levels in Osaka. The concentrations of 5- and 6-ring PAHs (BeP, BbF, BkF, BaP, BghiP and InP) were much higher in TSP samples in Ho Chi Minh City than in Osaka, accounting for 82% and 51% of total PAHs, respectively. These PAHs are known to be highly carcinogenic and mutagenic in humans. Vehicular emission is suggested as one of the main pollution sources of PAHs in both cities. Motorcycles and gasoline automobiles are suggested as the main emission sources of PAHs in Ho Chi Minh City, whereas diesel automobiles are the primary source in Osaka. Seasonal variations of PAHs were observed in this study; higher concentrations of PAHs were found in the rainy season (May-December) and lower concentrations corresponded to the dry season (February-April) in Ho Chi Minh City, while higher concentrations of PAHs were observed in the winter (November-January) in Osaka. The number of sunshine hours was an important meteorological factor affecting seasonal variations of PAHs in Ho Chi Minh City, while the temperature was a main factor causing the variations of PAHs in Osaka. The high BaP equivalent concentration of 5- and 6-ring PAHs even in the ambient air is an alarming signal for harmfulness to human health and environmental quality in Ho Chi Minh City. 相似文献
996.
Peng X Wang Z Mai B Chen F Chen S Tan J Yu Y Tang C Li K Zhang G Yang C 《The Science of the total environment》2007,384(1-3):393-400
Three dated sedimentary cores were collected for the investigation of temporal trends and the environmental loadings of nonylphenol (NP) and bisphenol A (BPA) in recent decades in the Pearl River Estuary (PRE), South China and the adjacent South China Sea (SCS). The peak fluxes of NP and BPA occurred in the mid-1980s in the PRE, coincident with the rapid economic growth in China. The decline of NP and BPA fluxes is attributable to the implementation of sewage treatment in the late 1980s in the Pearl River Delta (PRD). Multi-model distributions were observed for the fluxes of NP and BPA in the SCS with the peak fluxes occurring in the late 1950s and the mid-1970s respectively. The fluxes of NP and BPA have increased since the 1990s due to the lack of adequate wastewater treatment facilities and the constant economic growth. Nonylphenol was quantifiably detected in sediments predating its widespread application (1940s), suggesting the downward penetration of NP in the sediment columns. The characterization results revealed that NP and BPA were preserved well and the isomer-selective degradation of NP did not occur significantly in the sediment cores. The environmental loadings of NP and BPA in the PRE sediments were roughly estimated to be 124 t and 1.7 t respectively over the past 30 years. 相似文献
997.
998.
999.
L Kohl T Drmota CD Thi M Callens J Van Beeumen FR Opperdoes PA Michels 《Canadian Metallurgical Quarterly》1996,76(1-2):159-173
A polyclonal antiserum raised against the purified glycosomal glycerol-3-phosphate dehydrogenase of Trypanosoma brucei brucei has been used to identify the corresponding cDNA clone in a T.b. brucei expression library. This cDNA was subsequently used to obtain genomic clones containing glycerol-3-phosphate dehydrogenase genes. Two tandemly arranged genes were detected in these clones. Characterization of one of the genes showed that it codes for a polypeptide of 353 amino acids, with a molecular mass of 37,651 Da and a calculated net charge of +8. Using the T.b. brucei gene as a probe, a corresponding glycerol-3-phosphate dehydrogenase gene was also identified in a genomic library of Leishmania mexicana mexicana. The L.m. mexicana gene codes for a polypeptide of 365 amino acids, with a molecular mass of 39,140 Da and a calculated net charge of +8. The amino-acid sequences of both polypeptides are 63% identical and carry a type-1 peroxisomal targeting signal (PTS1) SKM and -SKL at their respective C-termini. Moreover, the L.m. mexicana polypeptide also carries a short N-terminal extension reminiscent of a mitochondrial transit sequence. Subcellular localisation analysis showed that in L.m. mexicana the glycerol-3-phosphate dehydrogenase activity co-fractionated both with mitochondria and with glycosomes. This is not the case in T. brucei, where the enzyme is predominantly glycosomal. The two trypanosomatid sequences resemble their prokaryotic homologues (32-36%) more than their eukaryotic counterparts (25-31%) and carry typical prokaryotic signatures. The possible reason for this prokaryotic nature of a trypanosomatid glycerol-3-phosphate dehydrogenase is discussed. 相似文献
1000.
C Viguié J Thibault JC Thiéry Y Tillet B Malpaux 《Canadian Metallurgical Quarterly》1996,8(6):465-474
The aim of this study was to analyse medico-legal autopsy rates among Norwegian citizens who died in the two northernmost counties of Norway during the 20-year period 1973-1992. Medico-legal autopsy rate was defined as the number of medico-legal autopsies divided by the total number of deaths. The rates were calculated according to year of death, manner of death, sex, age, police district and county. The material included 1539 medico-legal autopsies. In the total 20-year period 37.9% (n = 1113) of the violent deaths and 1.2% (n = 426) of the natural deaths were subjected to medico-legal autopsy. The annual rates increased gradually up to 1987. In the last 5-year period 51.7% of the violent deaths and 2.1% of the natural deaths were subjected to medico-legal autopsy. Among violent deaths in this period the medico-legal autopsy rates were: suicides 65.7%, motor vehicle traffic accidents 58.3%, falls 8.6%, and other violent deaths 77.1%. Females dying after a fall and due to natural causes were significantly less frequently than males subjected to medico-legal autopsy. These two categories of death also revealed a significant decrease in autopsy rate with increasing age (age group 0-29, 30-59 and > or = 60 years) in each 5-year period. In cases of violent death the medico-legal autopsy rate according to police district varied from 24.1% to 88.9% in the last 5-year period. In conclusion, medico-legal autopsy rates depended on manner of death, sex, age and police district, besides changes in legislation. 相似文献