全文获取类型
收费全文 | 12160篇 |
免费 | 780篇 |
国内免费 | 7篇 |
出版年
2024年 | 15篇 |
2023年 | 39篇 |
2022年 | 138篇 |
2021年 | 233篇 |
2020年 | 131篇 |
2019年 | 205篇 |
2018年 | 295篇 |
2017年 | 244篇 |
2016年 | 427篇 |
2015年 | 618篇 |
2014年 | 754篇 |
2013年 | 801篇 |
2012年 | 1077篇 |
2011年 | 1047篇 |
2010年 | 652篇 |
2009年 | 501篇 |
2008年 | 791篇 |
2007年 | 677篇 |
2006年 | 615篇 |
2005年 | 563篇 |
2004年 | 574篇 |
2003年 | 460篇 |
2002年 | 364篇 |
2001年 | 355篇 |
2000年 | 327篇 |
1999年 | 227篇 |
1998年 | 90篇 |
1997年 | 77篇 |
1996年 | 50篇 |
1995年 | 48篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 83篇 |
1991年 | 54篇 |
1990年 | 44篇 |
1989年 | 48篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 21篇 |
1985年 | 23篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
Industrial production can produce large amounts of harmful by-products, causing serious pollution and ecological risk. In addition, if government regulations are subjected into the industries, huge cost risk will be faced. This article adopts a two-stage slack-based undesirable-output data envelope analysis (DEA) model to measure the eco-efficiency of China. In the first stage, we analyze the eco-efficiency of each province of China, and in the second stage, we employed a truncated bootstrap method to understand the determinants of eco-efficiency. The results indicate that whereas the eco-efficiency of the eastern region was the highest, that of the western region was the lowest. The western region's economy lagged behind that of other regions, and its environment suffered from heavy pollution. It was found that the level of industrialization did not contribute to eco-efficiency. However, promotion of the service industry, investment for the environment, and regional innovation have positive effects on eco-efficiency. 相似文献
153.
Toxic metal contamination in the vicinity of Korean abandoned metal mines has been reported. A risk assessment for these metals was performed for the inhabitants in the area of the abandoned Jukjeon metal mine. Soil, groundwater, and crop samples were collected around the mine. After pretreatment of these samples, metal concentrations were measured and then a risk assessment was performed using the Korean soil-contamination risk assessment guidelines. Phytoaccumulation of metals in crops was observed in soybeans (As and Zn), red peppers (Zn), sweet potatoes (As and Zn), and cabbage (Cu), which had higher metal concentrations than soils in the area. The metal intake rate was highest for inhalation of soil. Cancer risk was highest from ingestion of As-contaminated crops. The sum of carcinogenic risks was 6.29 × 10–3. The non-carcinogenic risk was highest for ingestion of As-contaminated crops (8.17). Most of the risks were attributable to As, Pb, and Hg contamination, therefore these three metals must be considered as the principal metals toxic to human health in the sampled area. In particular, the inhalation of metal-contaminated soil should be considered for risk assessment along with ingestion of water and crops in abandoned mine areas. 相似文献
154.
Hye Jung Choi Jeoung-Yoon Seo Su Mi Hwang Yong-Ill Lee Yong Kee Jeong Ja-Young Moon Woo Hong Joo 《Biotechnology and Bioprocess Engineering》2013,18(5):1000-1007
Bacterial strains growing in river sediments were screened to identify an organic solvent-tolerant strain of Pseudomonas. Using this screen, Pseudomonas sp. BCNU 106 was isolated on the basis of its ability to grow on benzene, toluene, ethylbenzene, and three xylene isomers, o-, m- and p-xylene, as its sole carbon source. BCNU 106 was identified as a gram-negative, rod-shaped aerobic and mesophilic bacterium, which grew in liquid media containing high concentrations of organic solvents. 16S rDNA analysis classified BCNU 106 as a new member of the genus Pseudomonas. BCNU 106 was distinguishable from other Pseudomonas strains that are tolerant to organic solvents in that the isolate had the ability to utilize all three xylene isomers as well as benzene, toluene and ethylbenzene. The unique properties of the isolate such as solvent-tolerance and the ability to degrade xylene isomers may have important implications for the efficient treatment of solvent wastes. 相似文献
155.
Byoung-Shik Shim Jung-ah Choi Ho-Hyun Song Sung-Moo Park In Su Cheon Ji-Eun Jang Sun Je Woo Chung Hwan Cho Min-Suk Song Hyemi Kim Kyung Joo Song Jae Myun Lee Suhng Wook Kim Dae Sub Song Young Ki Choi Jae-Ouk Kim Huan Huu Nguyen Dong Wook Kim Young Yil Bahk Cheol-Heui Yun Man Ki Song 《Journal of microbiology (Seoul, Korea)》2013,51(1):130-135
Influenza viruses are respiratory pathogens that continue to pose a significantly high risk of morbidity and mortality of humans worldwide. Vaccination is one of the most effective strategies for minimizing damages by influenza outbreaks. In addition, rapid development and production of efficient vaccine with convenient administration is required in case of influenza pandemic. In this study, we generated recombinant influenza virus hemagglutinin protein 1 (sHA1) of 2009 pandemic influenza virus as a vaccine candidate using a well-established bacterial expression system and administered it into mice via sublingual (s.l.) route. We found that s.l. immunization with the recombinant sHA1 plus cholera toxin (CT) induced mucosal antibodies as well as systemic antibodies including neutralizing Abs and provided complete protection against infection with pandemic influenza virus A/CA/04/09 (H1N1) in mice. Indeed, the protection efficacy was comparable with that induced by intramuscular (i.m.) immunization route utilized as general administration route of influenza vaccine. These results suggest that s.l. vaccination with the recombinant non-glycosylated HA1 protein offers an alternative strategy to control influenza outbreaks including pandemics. 相似文献
156.
Irmina Diala Nicole Wagner Frédérique Magdinier Marina Shkreli Serge Bauwens Caroline Schluth‐Bolard Thomas Simonet Valérie M Renault Jing Ye Abdelnnadir Djerbi Pascal Pineau Jinkuk Choi Steven Artandi Anne Dejean Eric Gilson 《EMBO reports》2013,14(4):356-363
The DNA‐binding protein TRF2 is essential for telomere protection and chromosome stability in mammals. We show here that TRF2 expression is activated by the Wnt/β‐catenin signalling pathway in human cancer and normal cells as well as in mouse intestinal tissues. Furthermore, β‐catenin binds to TRF2 gene regulatory regions that are functional in a luciferase transactivating assay. Reduced β‐catenin expression in cancer cells triggers a marked increase in telomere dysfunction, which can be reversed by TRF2 overexpression. We conclude that the Wnt/β‐catenin signalling pathway maintains a level of TRF2 critical for telomere protection. This is expected to have an important role during development, adult stem cell function and oncogenesis. 相似文献
157.
Changon Seo Yun-Hyeok Choi Jong Seog Ahn Joung Han Yim Hong Kum Lee 《Journal of enzyme inhibition and medicinal chemistry》2013,28(5):1133-1137
The selective inhibition of PTP1B has been widely recognized as a potential drug target for the treatment of type 2 diabetes and obesity. In the course of screening for PTP1B inhibitory natural products, the MeOH extract of the dried sample of the Antarctic lichen Umbilicaria antarctica was found to exhibit significant inhibitory effect, and the bioassay-guided fractionation and purification afforded three related lichen metabolites 1-3. Compounds 1-3 were identified as gyrophoric acid (1), lecanoric acid (2), and methyl orsellinate (3) mainly by analysis of NMR and MS data. These compounds inhibited PTP1B activity with 50% inhibitory concentration values of 3.6 ± 0.04 μM, 31 ± 2.7 μM, and 277 ± 8.6 μM, respectively. Furthermore, the kinetic analysis of PTP1B inhibition by compound 1 suggested that the compound inhibited PTP1B activity in a non-competitive manner. 相似文献
158.
Vasily I. Radashevsky Tatyana V. Neretina Victoria V. Pankova Alexander B. Tzetlin Jin-Woo Choi 《分类学与生物多样性》2013,11(4):424-433
Rhynchospio glutaea (Ehlers, 1897), Rhynchospio arenincola Hartman, 1936 and Rhynchospio arenincola asiatica Chlebovitsch, 1959, originally described from Strait of Magellan, California, and South Kurile Islands respectively, appear similar to each other in adult morphology. These species and subspecies have been considered by some authors as subjective synonyms and are here referred to as members of the R. glutaea complex. Sequence data of four gene fragments (2465 bp in total) of the mitochondrial 16S rDNA, nuclear 18S and 28S rDNA, and Histone 3 have shown that R. glutaea complex individuals from the South West Atlantic (Argentina), North East Pacific (British Columbia and Oregon) and North West Pacific (South Korea) were genetically distant and not conspecific. These data also indicate that R. arenincola from North America and R. aff. asiatica from South Korea are more closely related to each other, and both are closer to R. glutaea from South America than to R. nhatrangi from Vietnam: nhatrangi (glutaea (arenincola-aff. asiatica)). Adults of the R. glutaea complex are hermaphrodites and the arrangement of gametes is suggested to be a crucial reproductive character for distinguishing these species. Based on this character, two species of the complex are apparent in the North West Pacific: R. asiatica Chlebovitsch, 1959 stat. nov. from the Kurile Islands (not analysed here) and an unnamed species from the mainland coast of Asia (here referred to as R. aff. asiatica). Adult morphology of R. asiatica stat. nov. is briefly described and illustrated. The lectotype and the type locality of the species on Iturup Is. are established for the first time. An identification key is provided to the 10 currently recognized Rhynchospio species. 相似文献
159.
Moon Woo Chun Sung Pil Choi Myong Jung Kim Chol Joon Bae Hyung Ryong Moon Hee-Doo Kim 《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):615-616
Abstract Novel 1,3-oxathiolanyl pyrimidine nucleosides with 5-hydroxymethyl substituent were synthesized starting from d-mannose and evaluated for antiviral activities against HIV-1, HSV type 1,2 and HCMV. 相似文献
160.
J. H. Choi S. Maruthamuthu Y. J. Lee A. N. Alshawabkeh 《Soil & Sediment Contamination》2013,22(7):767-782
High nitrate concentration in surface soils is a serious concern for the agricultural industry throughout the world. Nitrate reduction can be achieved by chemical or biological processes; however, these processes are difficult to achieve in-situ because of the low permeability of clays. This study evaluates bio-electrokinetic processes for nitrate treatment in low-permeability soils. The concept is based on using iron electrodes to generate an electric field and a reducing environment in the soil to facilitate nitrate reduction by existing bacteria. Experiments were conducted using starch as an additive for microbial activity in the anolyte. Three sets of experiments were conducted under 0.5, 1.0, and 2.0 V cm?1 voltage gradient, and using starch as an anolyte for enhancing existing microbial activity in the soil. Initial nitrate concentration in the soil (agricultural soil collected from Jinju, Korea) was between 782 and 800 mg kg?1. Removal of 100% nitrate was achieved in the soil under 0.5 and 1.0 V cm?1 due to the combined effect of biological and iron reduction. A control experiment with iron electrodes, but without starch, was not as effective. Ammonium was also effectively removed by the combined action of starch and iron under 0.5 and 1.0 V cm?1. The role of starch with iron on the nitrate and ammonium removal process is evaluated along with the role of transport by electro-osmosis and electro-migration. The bacterial action on denitrification and nitrification is assessed and the relationship between pH and the efficiency of nitrate reduction in the bio-EK systems is evaluated. 相似文献