全文获取类型
收费全文 | 113659篇 |
免费 | 1679篇 |
国内免费 | 887篇 |
专业分类
116225篇 |
出版年
2023年 | 187篇 |
2022年 | 309篇 |
2021年 | 599篇 |
2020年 | 438篇 |
2019年 | 513篇 |
2018年 | 12303篇 |
2017年 | 11101篇 |
2016年 | 8185篇 |
2015年 | 1768篇 |
2014年 | 1556篇 |
2013年 | 1822篇 |
2012年 | 5846篇 |
2011年 | 14302篇 |
2010年 | 12873篇 |
2009年 | 9021篇 |
2008年 | 10830篇 |
2007年 | 12326篇 |
2006年 | 1309篇 |
2005年 | 1545篇 |
2004年 | 1918篇 |
2003年 | 1821篇 |
2002年 | 1394篇 |
2001年 | 599篇 |
2000年 | 476篇 |
1999年 | 277篇 |
1998年 | 159篇 |
1997年 | 129篇 |
1996年 | 116篇 |
1995年 | 99篇 |
1994年 | 95篇 |
1993年 | 117篇 |
1992年 | 160篇 |
1991年 | 160篇 |
1990年 | 125篇 |
1989年 | 96篇 |
1988年 | 103篇 |
1987年 | 92篇 |
1986年 | 72篇 |
1985年 | 71篇 |
1984年 | 67篇 |
1983年 | 72篇 |
1982年 | 52篇 |
1981年 | 46篇 |
1980年 | 37篇 |
1979年 | 51篇 |
1978年 | 49篇 |
1975年 | 56篇 |
1974年 | 32篇 |
1972年 | 265篇 |
1971年 | 296篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
941.
Philippos Peidis Thomas Giannakouros Matthew E Burow Robert W Williams Robert E Scott 《BMC systems biology》2010,4(1):14
Background
The 250 kDa P2P-R protein (also known as PACT and Rbbp6) was cloned over a decade ago and was found to bind both the p53 and Rb1 tumor suppressor proteins. In addition, P2P-R has been associated with multiple biological functions, such as mitosis, mRNA processing, translation and ubiquitination. In the current studies, the online GeneNetwork system was employed to further probe P2P-R biological functions. Molecular studies were then performed to confirm the GeneNetwork evaluations. 相似文献942.
Jinze Noordijk C. J. M. Musters Jerry van Dijk Geert R. de Snoo 《Biodiversity and Conservation》2010,19(11):3255-3268
Sown, temporary field margins are a common agri-environment scheme (AES) in the Netherlands. Despite their wide application, though, there has been scarcely any long-term monitoring of the succession of invertebrates. In the field margins of 40 farms, invertebrate diversity and the abundance of three functional groups were assessed in relation to age. The diversity in terms of number of species groups was found to increase with the age of the margins. The abundance of herbivores and detritivores also showed a positive correlation with the age of the margins. However, the abundance of predators decreased with increasing age. Older margins showed a higher total vegetation cover and fewer plant species, also resulting in lower plant species evenness. We suggest several changes to the current AES regulations. For the conservation of invertebrate diversity, longer-lasting field margins are desirable. In addition, old margins are favoured by detritivores, a group that has particular difficulty finding suitable habitats in agricultural landscapes. However, such margins are less favourable from an agricultural perspective, as they appear unsuitable for high abundances of potentially useful predators and the high vegetation cover attracts many potentially harmful herbivores. To circumvent this, the AES might be extended by incorporating hay-making, which would reduce standing biomass and might lead to more predators and fewer herbivores. 相似文献
943.
Senka S. Vidović Ibrahim O. Mujić Zoran P. Zeković Žika D. Lepojević Vesna T. Tumbas Aida I. Mujić 《Food biophysics》2010,5(1):49-58
Considering the growing interest for mushrooms and the demand search of natural antioxidants sources, the aim of this study
was to investigate the antioxidant properties of two edible widely used Boletus species, Boletus edulis, and Boletus auranticus, collected from Istra region in Croatia in late summer 2007. To evaluate the antioxidant properties and content of antioxidant
compounds, scavenging capacity on DPPH˙, OH˙, and O2˙− radicals, reducing power and capacity to inhibit lipid peroxidation has been investigated. It is determined that content
of total phenols (41.82 ± 0.08 mg gallic acid equivalent per gram of dry extract) was higher for B. edulis. Using high performance liquid chromatography/diode array detector analysis, the main antioxidant compound, variegatic acid,
has been detected and quantified. 1,1-Diphenyl-2-picryl-hydrazyl-hydrate assay was used as a preliminary free radical–scavenging
evaluation. By this assay, it has been found that B. edulis dry mushroom extract exhibits 50% of inhibition value at the extract concentration of 0.016 ± 0.0003 mg/ml. The extracts
were capable of reducing iron(III) and, thus, are capable of donating electrons. Using electron paramagnetic resonance spin-trapping
and spin-probing techniques, activity against relevant reactive species, ˙OH and O2˙− radical, was analyzed for both mushroom extracts. Both investigated extracts are determined as good inhibitors for ˙OH radical
reduction, and both exhibited significant capacity for scavenging O2˙− radical and for that could help to prevent or meliorate oxidative damage. Only B. edulis extract prevents lipid peroxidation. Investigated mushroom extracts could represent easily accessible natural antioxidant
resource. 相似文献
944.
Two lactic acid bacteria (LAB) having ornithine-producing capacity were isolated from Korean natural sea salt. They were Gram-positive,
short rod-type bacteria, and able to grow anaerobically with CO2 production. The isolates grew well on MRS broth at 30–37°C and a pH of 6.5–8.0. The optimum temperature and pH for growth
are 37°C and pH 7.0. The isolates fermented D-ribose, D-galactose, D-lactose, D-maltose, Dcellobiose, D-tagatose, D-trehalose,
sucrose, D-melezitose, gentiobiose, D-glucose but not D-melibiose, inositol, and L-sorbose. The 16S rDNA sequences of the
two isolates showed 99.5% and 99.6% homology with the Weissella koreensis S5623 16S rDNA (Access no. AY035891). They were accordingly identified and named as Weissella koreensis MS1-3 and Weissella koreensis MS1-14, and produced intracellular ornithine at levels of 72 mg/100 g cell F.W. and 105 mg/100 g cell F.W. and extracellular
ornithine at levels of 4.5 mg/100 ml and 4.6 mg/100 ml medium, respectively, by culturing in MRS broth supplemented with 1%
arginine. High cell growth was maintained in MRS broth with a NaCl concentration of 0–6%. These results show for the first
time that Korean natural sea salts contain lactic acid bacteria Weissella koreensis strains having ornithine producing capacity. 相似文献
945.
Identification and characterization of adipose triglyceride lipase (ATGL) gene in birds 总被引:1,自引:0,他引:1
Qinghua Nie Yongsheng Hu Liang Xie Chengguang Zhang Xu Shen Xiquan Zhang 《Molecular biology reports》2010,37(7):3487-3493
Adipose triglyceride lipase (ATGL) is a triglyceride hydrolysis lipase and is generally related to lipid metabolism in animals.
The ATGL gene was well studied in mammals, however very less was known in birds that differed significantly with mammals for
lipid metabolism. In this study, cloning, mRNA real time and association analysis was performed to characterize the ATGL gene in birds. Results showed that the obtained ATGL gene cDNA of parrot, quail, duck were 1,651 bp (NCBI accession number: GQ221784), 1,557 bp (NCBI accession number: GQ221783)
and 1,440 bp each, encoded 481-, 482- and 279-amino acid (AA) peptide, respectively. The parrot ATGL (pATGL) gene was found to predominantly express in breast muscle and leg muscle, and very higher ATGL mRNA level was also found in heart, abdominal fat and subcutaneous fat. The quail ATGL (qATGL) gene was also predominantly expressed in breast muscle and leg muscle, and then to a much lesser degree in heart. The duck
ATGL (dATGL) gene was found to predominantly express in subcutaneous fat and abdominal fat, quite higher ATGL mRNA was also found in heart, spleen, breast muscle and leg muscle. Blast analyses indicated the high homology of ATGL and
its patatin region, and moreover, and the active serine hydrolase motif (“GASAG” for “GXSXG”) and the glycine rich motif (“GCGFLG”
for “GXGXXG”) were completely conservative among 14 species. Association analyses showed that c.950+24C>A, c.950+45C>G, c.950+73G>A,
c.950+83C>T and c.950+128delA of chicken ATGL gene (cATGL) were all significantly or highly significantly with cingulated fat width (CFW) (P < 0.05 or P < 0.01), and c.777−26C>A, c.950+45C>G, c.950+73G>A and c.950+118C>T were all significantly or highly significantly with pH
value of breast muscle (BMPH) (P < 0.05). 相似文献
946.
Miao Yin Liang Zhang Xiao-ming Sun Liu-feng Mao Jie Pan 《Molecular biology reports》2010,37(4):2049-2054
To investigate the effect of apolipoprotein E (apoE) on cytokine expression profile of the liver of young mice, quantitative
RT-PCR (qRT-PCR) assay and cytokine antibody array for multiplex analysis of 62 cytokines have been used to analyze characteristics
of expression of cytokines in the liver of 6-week-old apoE-null (apoE−/−) mice. The levels of plasma cytokines were also analyzed. The mRNA level of IL-1β, IL-2, IL-6, ICAM-1, VCAM-1, MCP-1, NF-κB
(p65), IFN-γ and IκB-α were increased significantly in apoE−/− mice comparative to wild-type (WT) mice. IL-4, IL-10 and GM-CSF, however, were slightly decreased. Compared with WT, levels
of 21 cytokines altered twofold or more in apoE−/− mice, including 10 cytokines increased and 11 decreased. Expression patterns of IL-1β, IL-2, IL-4, IL-6, IL-10, GM-CSF, IFN-γ
and VCAM-1 showed identical trend between cytokine antibody array and qRT-PCR analysis. Moreover, levels of IL-1β, IFN-γ and
IL-6 in the plasma were elevated, while IL-4 was lightly decreased in apoE−/− mice compared to those in WT mice. These results implied that promotion of type I immune response in the liver of young apoE−/− mice due to alteration of these cytokines, and the phenotypes may be caused by the regulation of NF-κB. The inflammation
and lipid metabolism dysfunction in the liver cooperated in dysfunction of the liver in young apoE−/− mice. 相似文献
947.
948.
Laurence Dutot Pascaline Lécorché Fabienne Burlina Rodrigue Marquant Vanessa Point Sandrine Sagan Gérard Chassaing Jean-Maurice Mallet Solange Lavielle 《Journal of chemical biology》2010,3(2):51-65
Cell-penetrating peptides (CPPs), which are usually short basic peptides, are able to cross cell membranes and convey bioactive
cargoes inside cells. CPPs have been widely used to deliver inside cells peptides, proteins, and oligonucleotides; however,
their entry mechanisms still remain controversial. A major problem concerning CPPs remains their lack of selectivity to target
a specific type of cell and/or an intracellular component. We have previously shown that myristoylation of one of these CPPs
affected the intracellular distribution of the cargo. We report here on the synthesis of glycosylated analogs of the cell-penetrating
peptide (R6/W3): Ac-RRWWRRWRR-NH2. One, two, or three galactose(s), with or without a spacer, were introduced into the sequence of this nonapeptide via a triazole link, the Huisgen reaction being achieved on a solid support. Four of these glycosylated CPPs were coupled via a disulfide bridge to the proapoptotic KLAK peptide, (KLAKLAKKLAKLAK), which alone does not enter into cells. The effect
on cell viability and the uptake efficiency of different glycosylated conjugates were studied on CHO cells and were compared
to those of the nonglycosylated conjugates: (R6/W3)S-S-KLAK and penetratinS-S-KLAK. We show that glycosylation significantly
increases the cell viability of CHO cells compared to the nonglycosylated conjugates and concomitantly decreases the internalization
of the KLAK cargo. These results suggest that glycosylation of CPP may be a key point in targeting specific cells. 相似文献
949.
Niels Tørring Susan Ball Dave Wright Gaïané Sarkissian Marie Guitton Bruno Darbouret 《Reproductive biology and endocrinology : RB&E》2010,8(1):129
Background
A disintegrin and metalloprotease 12 (ADAM12-S) has previously been reported to be significantly reduced in maternal serum from women with fetal aneuploidy early in the first trimester and to significantly improve the quality of risk assessment for fetal trisomy 21 in prenatal screening. The aim of this study was to determine whether ADAM12-S is a useful serum marker for fetal trisomy 21 using the mixture model. 相似文献950.
Study of the factors affecting the extraction of soybean protein by reverse micelles 总被引:3,自引:0,他引:3
Xihong Zhao Yanmei Li Xiaowei He Nanjing Zhong Zhenbo Xu Liansheng Yang 《Molecular biology reports》2010,37(2):669-675
In this work, the forward and back extraction of soybean protein by reverse micelles was studied. The reverse micellar systems
were formed by anionic surfactant sodium bis(2-ethyl hexyl) sulfosuccinate (AOT), isooctane and KCl solution. The effects
of AOT concentration, aqueous pH, KCl concentration and phase volume ratio on the extraction efficiency of soybean protein
were tested. Suitability of reverse micelles of AOT and Triton-X-100/AOT mixture in organic solvent toluene for soybean protein
extraction was also investigated. The experimental results lead to complete forward extraction at the AOT concentration 120 mmol l−1, aqueous pH 5.5 and KCl concentration 0.8 mol l−1. The backward extraction with aqueous phase (pH 5.5) resulted in 100% extraction of soybean protein from the organic phase. 相似文献