全文获取类型
收费全文 | 774篇 |
免费 | 47篇 |
国内免费 | 2篇 |
出版年
2023年 | 4篇 |
2022年 | 22篇 |
2021年 | 35篇 |
2020年 | 18篇 |
2019年 | 14篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 24篇 |
2015年 | 44篇 |
2014年 | 52篇 |
2013年 | 67篇 |
2012年 | 62篇 |
2011年 | 74篇 |
2010年 | 41篇 |
2009年 | 27篇 |
2008年 | 51篇 |
2007年 | 30篇 |
2006年 | 32篇 |
2005年 | 27篇 |
2004年 | 31篇 |
2003年 | 29篇 |
2002年 | 26篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有823条查询结果,搜索用时 15 毫秒
61.
Carotenoids are converted by carotenoid cleavage dioxygenases that catalyze oxidative cleavage reactions leading to apocarotenoids.
However, apocarotenoids can also be further truncated by some members of this enzyme family. The plant carotenoid cleavage
dioxygenase 1 (CCD1) subfamily is known to degrade both carotenoids and apocarotenoids in vitro, leading to different volatile
compounds. In this study, we investigated the impact of the rice CCD1 (OsCCD1) on the pigmentation of Golden Rice 2 (GR2),
a genetically modified rice variety accumulating carotenoids in the endosperm. For this purpose, the corresponding cDNA was
introduced into the rice genome under the control of an endosperm-specific promoter in sense and anti-sense orientations.
Despite high expression levels of OsCCD1 in sense plants, pigment analysis revealed carotenoid levels and patterns comparable
to those of GR2, pleading against carotenoids as substrates in rice endosperm. In support, similar carotenoid contents were
determined in anti-sense plants. To check whether OsCCD1 overexpressed in GR2 endosperm is active, in vitro assays were performed
with apocarotenoid substrates. HPLC analysis confirmed the cleavage activity of introduced OsCCD1. Our data indicate that
apocarotenoids rather than carotenoids are the substrates of OsCCD1 in planta. 相似文献
62.
Raed Salim Gali Garmi Zohar Nachum Eliezer Shalev 《Reproductive biology and endocrinology : RB&E》2010,8(1):81
Background
Variable decelerations are the most frequent fetal heart rate changes that are related to labor. The objective of the study was to estimate the impact of non-significant variable decelerations (NSV) appearing during the latent phase of labor on delivery mode and neonatal outcome. 相似文献63.
64.
Sigruener A Buechler C Bared SM Grandl M Aslanidis C Ugocsai P Gehrmann M Schmitz G 《Biochemical and biophysical research communications》2007,359(3):723-728
Uptake of modified lipoproteins by macrophages causes foam cell formation and promotes atherosclerosis. Atherogenic lipoproteins are cytotoxic and induce cell death under certain conditions but may also enhance macrophage survival. Macrophages treated with enzymatically modified LDL (E-LDL) were subjected to GeneChip analysis and the antiapoptotic gene TOSO was found induced. TOSO mRNA is upregulated and apoptosis is reduced in E-LDL but not in oxidized LDL (Ox-LDL) loaded macrophages. FLIP(L) abundance was suggested to mediate the antiapoptotic properties of TOSO; however, FLIP(L) was not changed. Ox-LDL is internalized predominantly by scavenger receptors such as CD36 while E-LDL particles are preferentially internalized by Fc- and complement-receptor dependent phagocytosis and internalization of phagobeads by macrophages upregulates TOSO. In COS-7 cells however, phagocytotic activity was not affected by TOSO. These data indicate that E-LDL-generated foam cells are protected from cell death most likely through the expression of TOSO by a FLIP(L) independent mechanism. 相似文献
65.
Kusal K. Das Amrita Das Gupta Salim A. Dhundasi Ashok M. Patil Swastika N. Das Jeevan G. Ambekar 《Biometals》2007,20(2):177-184
In this experimental study, we investigated whether l-ascorbic acid has any influence on the blood antioxidant defense system, lipid peroxidation and hematological parameters
of the albino rats exposed to nickel sulfate(NiSO4).Twenty four adult rats were divided into four groups of six animals in each group. The control rats were untreated and comprised
Group I. Group II rats were administered nickel sulfate (2.0 mg/100 g b.wt.; intraperitonially, i.p.). Group II rats were
treated orally l-ascorbic acid (50 mg/100 g b.wt.) and Group IV rats were given both nickel sulfate and l-ascorbic acid simultaneously on alternate days until the tenth dose. The hematological parameters were assessed: red blood
corpuscle counts, packed cell volume %, hemoglobin concentration, white blood corpuscle counts and platelets count decreased
significantly and clotting time increased significantly in nickel treated rats. We also observed increase malondialdehyde
(MDA) and decrease glutathione level (GSH) in erythrocytes of nickel treated rats. The activities of erythrocyte antioxidant
enzymes like superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were significantly increased in
rats treated with nickel sulfate. Simultaneously treatment of l-ascorbic acid exhibited a possible protective role on the toxic effect of nickel sulfate on the hematological values, erythrocyte
MDA and GSH concentrations as well as antioxidant enzymatic defense system. 相似文献
66.
Ren H Dover LG Islam ST Alexander DC Chen JM Besra GS Liu J 《Molecular microbiology》2007,65(5):1345-1359
Lipooligosaccharides (LOSs) are antigenic glycolipids that are present in some species of Mycobacterium including the Canetti strain of M. tuberculosis. The core LOS structures from several mycobacterial organisms have been established, but the biosynthetic pathways of LOSs remain unknown. In this study, we describe two transposon insertion mutants of M. marinum that exhibit altered colony morphology. Cell wall analysis reveals that the MRS1271 mutant is defective in the synthesis of LOS-II, whereas the MRS1178 mutant accumulates an intermediate between LOS-I and -II. The genetic lesions were localized to two genes, MM2309 and MM2332. MM2309 encodes a UDP-glucose dehydrogenase that is involved in the synthesis of d-xylose. MM2332 is predicted to encode a decarboxylase. These two genes and a previously identified losA gene are localized in a gene cluster likely to be involved in the biosynthesis of LOSs. Our results also show that LOSs play an important role in sliding motility, biofilm formation, and infection of host macrophages. Taken together, our studies have identified, for the first time, a LOS biosynthetic locus. This is an important step in assessing the differential distribution of LOSs among Mycobacterium species and understanding the role of LOSs in mycobacterial virulence. 相似文献
67.
Bashir Nabiha Ishfaq Mehreen Mazhar Kehkashan Khan Jahangir Sarwar Shahid Ramla 《Molecular biology reports》2022,49(1):487-495
Molecular Biology Reports - Biological treatment of many cancers currently targets membrane bound receptors located on a cell surface. We are in a great to need identify novel membrane proteins... 相似文献
68.
69.
The influenced of PAC, zeolite, and Moringa oleifera as biofouling reducer (BFR) on hybrid membrane bioreactor of palm oil mill effluent (POME) 总被引:2,自引:0,他引:2
The main objective of this work was to determine the effectiveness of various biofouling reducers (BFRs) to operational condition in hybrid membrane bioreactor (MBR) of palm oil mill effluent (POME). A series of tests involving three bench scale (100 L) hybrid MBR were operated at sludge retention times (SRTs) of 30 days with biofouling reducer (BFR). Three different biofouling reducers (BFRs) were powdered actived carbon (PAC), zeolite (Ze), and Moringa oleifera (Mo) with doses of 4, 8 and 12 g L−1 respectively were used. Short-term filtration trials and critical flux tests were conducted. Results showed that, all BFRs successfully removed soluble microbial products (SMP), for PAC, Ze, and Mo at 58%, 42%, and 48%, respectively. At their optimum dosages, PAC provided above 70% reductions and 85% in fouling rates during the short-term filtration and critical flux tests. 相似文献
70.
Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and characterisation of its blend with oil palm empty fruit bunch fibers 总被引:1,自引:0,他引:1
Poly(3-hydroxybutyrate-co-38 mol%-3-hydroxyvalerate) [P(3HB-co-38mol%-3HV)] was produced by Cupriavidus sp. USMAA2-4 in the presence of oleic acid and 1-pentanol. Due to enormous production of empty fruit bunch (EFB) in the oil palm plantation and high production cost of P(3HB-co-3HV), oil palm EFB fibers were used for biocomposites preparation. In this study, maleic anhydride (MA) and benzoyl peroxide (DBPO) were used to improve the miscibility between P(3HB-co-3HV) and EFB fibers. Introduction of MA into P(3HB-co-3HV) backbone reduced the molecular weight and improved the thermal stability of P(3HB-co-3HV). Thermal stability of P(3HB-co-3HV)/EFB composites was shown to be comparable to that of commercial packaging product. Composites with 35% EFB fibers content have the highest tensile strength compared to 30% and 40%. P(3HB-co-3HV)/EFB blends showed less chemicals leached compared to commercial packaging. 相似文献