全文获取类型
收费全文 | 21535篇 |
免费 | 1637篇 |
国内免费 | 1589篇 |
专业分类
24761篇 |
出版年
2024年 | 58篇 |
2023年 | 252篇 |
2022年 | 659篇 |
2021年 | 1163篇 |
2020年 | 770篇 |
2019年 | 940篇 |
2018年 | 909篇 |
2017年 | 681篇 |
2016年 | 953篇 |
2015年 | 1305篇 |
2014年 | 1579篇 |
2013年 | 1729篇 |
2012年 | 1901篇 |
2011年 | 1772篇 |
2010年 | 1086篇 |
2009年 | 994篇 |
2008年 | 1141篇 |
2007年 | 1004篇 |
2006年 | 859篇 |
2005年 | 742篇 |
2004年 | 572篇 |
2003年 | 552篇 |
2002年 | 451篇 |
2001年 | 324篇 |
2000年 | 328篇 |
1999年 | 330篇 |
1998年 | 192篇 |
1997年 | 173篇 |
1996年 | 181篇 |
1995年 | 180篇 |
1994年 | 158篇 |
1993年 | 118篇 |
1992年 | 158篇 |
1991年 | 115篇 |
1990年 | 112篇 |
1989年 | 78篇 |
1988年 | 54篇 |
1987年 | 47篇 |
1986年 | 38篇 |
1985年 | 37篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1966年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Identification of a stable quantitative trait locus for percentage grains with white chalkiness in rice (Oryza sativa) 总被引:1,自引:0,他引:1
Guo T Liu X Wan X Weng J Liu S Liu X Chen M Li J Su N Wu F Cheng Z Guo X Lei C Wang J Jiang L Wan J 《植物学报(英文版)》2011,53(8):598-607
High chalkiness is a major problem in many rice-producing areas of the world, especially in hybrid rice (Oryza sativa L.) in China. We previously showed a major quantitative trait locus for the percentage of grains with white chalkiness (QTLqPGWC-8) in the interval G1149-R727 on chromosome 8 using a chromosome segment substitution line (CSSL). Here, we selected the line-CSSL50 harboring the QTLqPGWC-8 allele from the CSSLs derived from a cross between Asominori (as a recurrent parent) and IR24 (as a donor parent), which had higher percentage chalkiness, markedly different from that of Asominori. There were also significant differences in starch granules, appearance of amylose content (AAC) and milling qualities between Asominori and CSSL50, but not in grain size or thousand grain weight (TGW). The BC(4) F(2) and BC(4) F(3) populations from a cross between CSSL50 and Asominori were used for fine mapping of qPGWC-8. We narrowed down the location of this QTL to a 142 kb region between Indel markers 8G-7 and 8G-9. QTLqPGWC-8 accounted for 50.9% of the difference in PGWC between the parents. The markers tightly linked to qPGWC-8 should facilitate cloning of the gene underlying this QTL and will be of value for marker-assisted selection in breeding rice varieties with better grain quality. 相似文献
82.
83.
Zhou Z Sun D Yang A Dong Y Chen Z Wang X Guan X Jiang B Wang B 《Fish & shellfish immunology》2011,31(4):540-547
The complement system has been discovered in invertebrates and vertebrates, and plays a crucial role in the innate defense against common pathogens. As a central component in the complement system, complement component 3 (C3) is an intermediary between innate and adaptive immune system. In this study, a new isoform of C3 in the sea cucumber Apostichopus japonicus, termed AjC3-2 was identified. Its open reading frame (ORF) is 5085?bp and encodes for 1695 amino acids with a putative signal peptide of 20 amino acid residues. The mature protein molecular weight of AjC3-2 was 187.72?kDa. It has a conserved thioester site and a linker R(689)RRR(692) where AjC3-2 is splitted into β and α chain during posttranslational modification. The expression patterns of two distinct sea cucumber C3 genes, AjC3-2 and AjC3, were similar. During the different development stages from unfertilized egg to juvenile of the sea cucumber, the highest expression levels of AjC3-2 and AjC3 genes were both found in late auricularia. In the adult, the highest expression of these two genes was observed in the coelomocytes and followed by the body wall. AjC3-2 and AjC3 genes expression increased significantly at 6?h after the LPS challenge. These results indicated that these two C3 genes play a pivotal role in immune responses to the bacterial infection in sea cucumber. 相似文献
84.
W Weng N A Brandenburg S Zhong J Halkias L Wu X C Jiang A Tall J L Breslow 《Journal of lipid research》1999,40(6):1064-1070
High density lipoprotein (HDL) cholesterol levels are inversely related to the risk of developing coronary heart disease. Apolipoprotein (apo) A-II is the second most abundant HDL apolipoprotein and apoA-II knockout mice show a 70% reduction in HDL cholesterol levels. There is also evidence, using human apoA-II transgenic mice, that apoA-II can prevent hepatic lipase-mediated HDL triglyceride hydrolysis and reduction in HDL size. These observations suggest the hypothesis that apoA-II maintains HDL levels, at least in part, by inhibiting hepatic lipase. To evaluate this, apoA-II knockout mice were crossbred with hepatic lipase knockout mice. Compared to apoA-II-deficient mice, in double knockout mice there were increased HDL cholesterol levels (57% in males and 60% in females), increased HDL size, and decreased HDL cholesteryl ester fractional catabolic rate. In vitro incubation studies of plasma from apoA-II knockout mice, which contains largely apoA-I HDL particles, showed active lipolysis of HDL triglyceride, whereas similar studies of plasma from apoA-I knockout mice, which contains largely apoA-II particles, did not. In summary, these results strongly suggest that apoA-II is a physiological inhibitor of hepatic lipase and that this is at least part of the mechanism whereby apoA-II maintains HDL cholesterol levels. 相似文献
85.
Malia M. Edwards Elmina Mammadova-Bach Fabien Alpy Annick Klein Wanda L. Hicks Michel Roux Patricia Simon-Assmann Richard S. Smith Gertraud Orend Jiang Wu Neal S. Peachey J��rgen K. Naggert Olivier Lefebvre Patsy M. Nishina 《The Journal of biological chemistry》2010,285(10):7697-7711
The Neuromutagenesis Facility at the Jackson Laboratory generated a mouse model of retinal vasculopathy, nmf223, which is characterized clinically by vitreal fibroplasia and vessel tortuosity. nmf223 homozygotes also have reduced electroretinogram responses, which are coupled histologically with a thinning of the inner nuclear layer. The nmf223 locus was mapped to chromosome 17, and a missense mutation was identified in Lama1 that leads to the substitution of cysteine for a tyrosine at amino acid 265 of laminin α1, a basement membrane protein. Despite normal localization of laminin α1 and other components of the inner limiting membrane, a reduced integrity of this structure was suggested by ectopic cells and blood vessels within the vitreous. Immunohistochemical characterization of nmf223 homozygous retinas demonstrated the abnormal migration of retinal astrocytes into the vitreous along with the persistence of hyaloid vasculature. The Y265C mutation significantly reduced laminin N-terminal domain (LN) interactions in a bacterial two-hybrid system. Therefore, this mutation could affect interactions between laminin α1 and other laminin chains. To expand upon these findings, a Lama1 null mutant, Lama1tm1.1Olf, was generated that exhibits a similar but more severe retinal phenotype than that seen in nmf223 homozygotes. The increased severity of the Lama1 null mutant phenotype is probably due to the complete loss of the inner limiting membrane in these mice. This first report of viable Lama1 mouse mutants emphasizes the importance of this gene in retinal development. The data presented herein suggest that hypomorphic mutations in human LAMA1 could lead to retinal disease. 相似文献
86.
Anla Hu Li Li Chuanlai Hu Daoming Zhang Chen Wang Yan Jiang Meng Zhang Chunmei Liang Wenjun Chen Qingli Bo Qihong Zhao 《Biological trace element research》2018,182(1):21-28
Data on the effects of magnesium-zinc-calcium-vitamin D co-supplementation on hormonal profiles, biomarkers of inflammation, and oxidative stress among women with polycystic ovary syndrome (PCOS) are scarce. The objective of this study was to assess the effects of magnesium-zinc-calcium-vitamin D co-supplementation on hormonal profiles, biomarkers of inflammation, and oxidative stress in women with PCOS. Sixty PCOS women were randomized into two groups and treated with 100 mg magnesium, 4 mg zinc, 400 mg calcium plus 200 IU vitamin D supplements (n = 30), or placebo (n = 30) twice a day for 12 weeks. Hormonal profiles, biomarkers of inflammation, and oxidative stress were assessed at baseline and at end-of-treatment. After the 12-week intervention, compared with the placebo, magnesium-zinc-calcium-vitamin D co-supplementation resulted in significant reductions in hirsutism (?2.4 ± 1.2 vs. ?0.1 ± 0.4, P < 0.001), serum high sensitivity C-reactive protein (?0.7 ± 0.8 vs. +0.2 ± 1.8 mg/L, P < 0.001), and plasma malondialdehyde (?0.4 ± 0.3 vs. +0.2 ± 1.0 μmol/L, P = 0.01), and a significant increase in plasma total antioxidant capacity concentrations (+46.6 ± 66.5 vs. ?7.7 ± 130.1 mmol/L, P = 0.04). We failed to find any significant effect of magnesium-zinc-calcium-vitamin D co-supplementation on free androgen index, and other biomarkers of inflammation and oxidative stress. Overall, magnesium-zinc-calcium-vitamin D co-supplementation for 12 weeks among PCOS women had beneficial effects on hormonal profiles, biomarkers of inflammation, and oxidative stress. 相似文献
87.
88.
K Y Jiang O Pitiot M Anissimova H Adenier M A Vijayalakshmi 《Biochimica et biophysica acta》1999,1433(1-2):198-209
Chemical glycosylation of bovine alpha-chymotrypsin, by a glucosamine adduct on the carboxyl group, results in the modification of its catalytic activity. The structural alterations of alpha-chymotrypsin resulting from its glycosylation are studied by immobilized metal-ion affinity chromatography (IMAC) and immobilized metal-ion affinity capillary electrophoresis (IMACE). The chemical glycosylation of alpha-chymotrypsin generates two distinct subpopulations of the protein: one which totally loses the initial affinity for IDA-Cu(II) and another which exhibits an increased affinity for the metal chelate ligand. 相似文献
89.
Zhenwei Qiu Yongbing Zhang Dorothea Bedigian Xiao Li Changsui Wang Hongen Jiang 《Economic botany》2012,66(3):255-263
Sesame Utilization in China: New Archaeobotanical Evidence from Xinjiang. A cache of sesame (Sesamum indicum L.) seeds, discovered in the Thousand Buddha Grottoes at Boziklik, Turpan, China, dating to ca. 700 years before present (BP), is hard evidence of their use in China since that time. Morphological and anatomical features suggest a white sesame cultivar. The sizeable quantity unearthed implies that sesame was a valued commodity that could provision the monks and enrich the diet of ancient inhabitants as an oil source. 相似文献
90.