全文获取类型
收费全文 | 7493篇 |
免费 | 535篇 |
国内免费 | 7篇 |
专业分类
8035篇 |
出版年
2024年 | 9篇 |
2023年 | 34篇 |
2022年 | 103篇 |
2021年 | 157篇 |
2020年 | 120篇 |
2019年 | 140篇 |
2018年 | 232篇 |
2017年 | 170篇 |
2016年 | 316篇 |
2015年 | 428篇 |
2014年 | 489篇 |
2013年 | 533篇 |
2012年 | 667篇 |
2011年 | 696篇 |
2010年 | 446篇 |
2009年 | 358篇 |
2008年 | 509篇 |
2007年 | 457篇 |
2006年 | 391篇 |
2005年 | 333篇 |
2004年 | 328篇 |
2003年 | 266篇 |
2002年 | 234篇 |
2001年 | 97篇 |
2000年 | 85篇 |
1999年 | 72篇 |
1998年 | 63篇 |
1997年 | 53篇 |
1996年 | 30篇 |
1995年 | 34篇 |
1994年 | 22篇 |
1993年 | 16篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1979年 | 6篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1969年 | 2篇 |
排序方式: 共有8035条查询结果,搜索用时 15 毫秒
51.
In Jung Kim Hyeok-Jin Ko Tae-Wan Kim Ki Hyun Nam In-Geol Choi Kyoung Heon Kim 《Applied microbiology and biotechnology》2013,97(12):5381-5388
BsEXLX1 from Bacillus subtilis is the first discovered bacterial expansin as a structural homolog of a plant expansin, and it exhibited synergism with cellulase on the cellulose hydrolysis in a previous study. In this study, binding characteristics of BsEXLX1 were investigated using pretreated and untreated Miscanthus x giganteus in comparison with those of CtCBD3, a cellulose-binding domain from Clostridium thermocellum. The amounts of BsEXLX1 bound to cellulose-rich substrates were significantly lower than those of CtCBD3. However, the amounts of BsEXLX1 bound to lignin-rich substrates were much higher than those of CtCBD3. A binding competition assay between BsEXLX1 and CtCBD3 revealed that binding of BsEXLX1 to alkali lignin was not affected by the presence of CtCBD3. This preferential binding of BsEXLX1 to lignin could be related to root colonization in plants by bacteria, and the bacterial expansin could be used as a lignin blocker in the enzymatic hydrolysis of lignocellulose. 相似文献
52.
Genetic localization and in vivo characterization of a Monascus azaphilone pigment biosynthetic gene cluster 总被引:1,自引:0,他引:1
53.
Keun Sik Baik Yeoung Min Hwang Jong-Soon Choi Joseph Kwon Chi Nam Seong 《Antonie van Leeuwenhoek》2013,104(6):1143-1150
A motile, curved to twisted rod-shaped aerobic bacterium, designated strain 04SU4-PT, was isolated from freshwater collected from the Woopo wetland (Republic of Korea). Cells were observed to be Gram-stain negative, catalase negative and oxidase positive. The major fatty acids (>10 % of the total) were identified as C19:0 ω8c cyclo (24.6 %), C16:0 (24.3 %) and C18:1 ω7c (13.1 %). The DNA G+C content was determined to be 71.5 mol%. The major polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine, one unknown phospholipid and one unknown aminolipid. The major ubiquinone was determined to be Q-10. A phylogenetic tree based on 16S rRNA gene sequences showed that strain 04SU4-PT forms an evolutionary lineage within the genus Dongia and its nearest neighbour is Dongia mobilis LM22T (98.0 % sequence similarity). Genomic DNA–DNA hybridization of stain 04SU4-PT with D. mobilis LM22T showed relatedness of only 34.2 %. The phenotypic characteristics indicate the strain 04SU4-PT can be distinguished from the sole member of the genus Dongia. On the basis of the data presented in this study, strain 04SU4-PT represents a novel species, for which the name Dongia rigui is proposed. The type strain is 04SU4-PT (KCTC 23341T = JCM 17521T). 相似文献
54.
Nguyen The Tung To Dao Cuong Tran Manh Hung Jeong Hyung Lee Mi Hee Woo Jae Sue Choi Jaewang Kim Sung Ho Ryu Byung Sun Min 《Bioorganic & medicinal chemistry letters》2013,23(5):1428-1432
Four new lanostane triterpenes, butyl lucidenate P (1), butyl lucidenate D2 (2), butyl lucidenate E2 (3) and butyl lucidenate Q (4) along with 11 known compounds (5–15) were isolated from the fruiting bodies of Ganoderma lucidum. Their chemical structures were established mainly by 1D and 2D NMR techniques and mass spectrometry. Their anti-inflammatory activity was evaluated against LPS-induced NO production in macrophage RAW 264.7 cells. Compounds 1, 3, 4, 9, 10 and 15 showed inhibitory potency with IC50 values of 7.4, 6.4, 4.3, 9.4, 9.2 and 4.5 μM, respectively. Compounds 1, 3 and 15 dose-dependently reduced the LPS-induced iNOS expressions. Preincubation of cell with 1, 3 and 15 significantly suppressed LPS-induced expression of COX-2 protein. 相似文献
55.
Phuong-Thao Tran Van-Hai Hoang Shivaji A. Thorat Sung Eun Kim Jihyae Ann Yu Jin Chang Dong Woo Nam Hyundong Song Inhee Mook-Jung Jiyoun Lee Jeewoo Lee 《Bioorganic & medicinal chemistry》2013,21(13):3821-3830
In an effort to design inhibitors of human glutaminyl cyclase (QC), we have synthesized a library of N-aryl N-(5-methyl-1H-imidazol-1-yl)propyl thioureas and investigated the contribution of the aryl region of these compounds to their structure–activity relationships as cyclase inhibitors. Our design was guided by the proposed binding mode of the preferred substrate for the cyclase. In this series, compound 52 was identified as the most potent QC inhibitor with an IC50 value of 58 nM, which was two-fold more potent than the previously reported lead 2. Compound 52 is a most promising candidate for future evaluation to monitor its ability to reduce the formation of pGlu-Aβ and Aβ plaques in cells and transgenic animals. 相似文献
56.
Jun Hyung Seo Hyo Geun Bae Da Hee Park Beom Seok Kim Jong Wook Lee Jung In Lee Dong Hyun Kim Seok Won Lee Bong Bo Seo 《Genes & genomics.》2013,35(1):117-124
Numerous studies on Oenothera species have been investigated for the physiological and ecological characteristics. However, no such an information based on molecular cytogenetic has yet been introduced, in turn, is very essential for identifying sequence polymorphisms of rRNA genes with their loci on mitotic phases for further biological researches. In this study, sequence variations of rRNA genes in Oenothera odorata and O. laciniata were examined to identify informative factors as unique or repeat sequences in intra- and inter-specific variations. Intra-specific variation revealed that the sequences of the rRNA genes including the spacer regions were highly conserved revealing only a few variations. From the inter-specific variation, spacer regions of species were completely different as (1) non-homologous sequences in NTS and (2) different type repeat sequences in ITS 1, 2 and 5.8S rRNA, whereas the remaining coding regions were highly conserved. FISH was carried out on mitotic phases using the 5S rDNA of the analyzed sequences. From the interphase and metaphase chromosomes of the examined species, two loci of 5S rDNA in O. odorata and four loci in O. laciniata were confirmed on the telomeric region of the short arm. Due to the small size and unclear centromere of the chromosomes, karyotype could not be completed. However, we confirmed that the chromosomes are organized by meta- and acrocentric chromosomes and the chromosomes with identified loci were assumed to be paired by the location of loci at the telomeric region on the short arm with relative lengths. 相似文献
57.
We examined the structure of the arthropod community among deciduous and coniferous dead woods along the process of wood decay. We collected dead wood‐dwelling arthropods from April 2010 to October 2011 by using a vacuum aspirator and an electric chain saw in three areas (Mt. Woonak, Mt. Wolchul, Mt. Jingang) in Korea. We identified them to species levels and classified them into functional groups. We collected 8792 arthropods (5 classes, 20 orders, 58 families, and 93 species). The species richness and abundance of arthropods increased with the progress of decay in dead woods. The evenness index seemed to be shown at a lower value at late decay stage than at early‐ and mid‐decay stages. The diversity index (H′) in conifers was lower than that in deciduous dead woods at the early decay stage but this situation was reversed at the late decay stage. Arthropod communities of functional groups, except the xylophagous insects, did not differ in the variables, but the proportion of xylophagous insects increased as the decay stages progressed. The abundance of arthropods and xylophagous was statistically significantly different. The patterns generated by non‐metric multidimensional scaling in the overall arthropod community composition revealed that the species composition between study areas were significantly different. We confirmed that dead woods play very important roles as arthropods' habitats. Thus, we suggest that the role of dead woods should be emphasized in the management of forest ecosystems. 相似文献
58.
Xiao Wei Xin Chen Xia Wang Weiwei Zheng Dong Zhang Dajun Tian Songhui Jiang Choon Nam Ong Gengsheng He Weidong Qu 《PloS one》2013,8(3)
Drinking water chlorination plays a pivotal role in preventing pathogen contamination against water-borne disease. However, chemical disinfection leads to the formation of halogenated disinfection by products (DBPs). Many DBPs are highly toxic and are of health concern. In this study, we conducted a comprehensive measurements of DBPs, including iodoacetic acid (IAA), iodoform (IF), nine haloacetic acids and four trihalomethanes in drinking waters from 13 water plants in Shanghai, China. The results suggested that IAA and IF were found in all the water treatment plants, with maximum levels of 1.66 µg/L and 1.25 µg/L for IAA and IF, respectively. Owing to deterioration of water quality, the Huangpu River has higher IAA and IF than the Yangtze River. Our results also demonstrated that low pH, high natural organic matter, ammonia nitrogen, and iodide in source waters increased IAA and IF formation. Compared to chlorine, chloramines resulted in higher concentration of iodinated DBP, but reduced the levels of trihalomethanes. This is the first study to reveal the widespread occurrence of IAA and IF in drinking water in China. The data provide a better understanding on the formation of iodinated disinfection byproducts and the findings should be useful for treatment process improvement and disinfection byproducts controls. 相似文献
59.
Mohammad R. Akbari Laura N. Anderson Daniel D. Buchanan Mark Clendenning Mark A. Jenkins Aung Ko Win John L. Hopper Graham G. Giles Robert Nam Steven Narod Steven Gallinger Sean P. Cleary 《Cancer epidemiology》2013,37(4):424-427
Introduction: The HOXB13 pGly84Glu mutation has recently been associated with an increased risk of prostate cancer but the association of other cancer sites with this allele has not been assessed. Data has suggested that HOXB13 expression levels are decreased in colorectal cancer (CRC) cell lines indicating this gene may be involved in colorectal tumourigenesis. Methods: To evaluate a potential association of this mutation with CRC, we genotyped the mutation in 2695 CRC cases and 4593 controls from population-based registries in Canada and Australia. Results: The HOXB13 pGly84Glu mutation was more common in CRC cases than controls (0.48% vs. 0.17%, P = 0.02) indicating a significant association between the HOXB13 variant and CRC risk (OR = 2.8; 95%CI: 1.2–6.8). This association was attenuated but remained significant with the inclusion of previously published and publicly available genotype data. Pedigree analysis of cases and controls revealed that 7/21 HOXB13 mutation carriers had a family history of prostate cancer. Discussion: This report is the first to suggest a risk of CRC associated with mutations in the HOXB13 gene. These findings require further validation but may be of importance in the screening and genetic counseling of families known to carry the HOXB13 pGly84Glu mutation. 相似文献
60.
Kyu-Tae Han Suk Yong Jang Sohee Park Kyung Hee Cho Ki-Bong Yoo Young Choi Eun-Cheol Park 《PloS one》2016,11(1)