全文获取类型
收费全文 | 1147篇 |
免费 | 85篇 |
专业分类
1232篇 |
出版年
2023年 | 14篇 |
2022年 | 26篇 |
2021年 | 27篇 |
2020年 | 25篇 |
2019年 | 18篇 |
2018年 | 36篇 |
2017年 | 26篇 |
2016年 | 31篇 |
2015年 | 31篇 |
2014年 | 54篇 |
2013年 | 74篇 |
2012年 | 101篇 |
2011年 | 68篇 |
2010年 | 37篇 |
2009年 | 34篇 |
2008年 | 37篇 |
2007年 | 59篇 |
2006年 | 36篇 |
2005年 | 34篇 |
2004年 | 44篇 |
2003年 | 35篇 |
2002年 | 47篇 |
2001年 | 34篇 |
2000年 | 38篇 |
1999年 | 33篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 22篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有1232条查询结果,搜索用时 15 毫秒
61.
The current study was intended to evaluate the hepatoprotective effect of Epicatechin (EC) against radiation-induced oxidative stress, in terms of inflammation and lipid peroxidation. Swiss albino mice were administered with EC (15 mg/kg body weight) for three consecutive days before exposing them to a single dose of 5-Gy (60)Co gamma (γ) irradiation. Mice were necropsied and livers were taken for immunohistochemistry, western blot analysis and biochemical tests for the detection of markers of hepatic oxidative stress. Nuclear translocation of nuclear factor kappa B (NF-κB) and lipid peroxidation were increased whereas the activities of superoxide dismutase (SOD) and catalase (CAT), reduced glutathione (GSH) content and ferric reducing antioxidant power (FRAP) were diminished upon radiation exposure compared to control. Translocation of NF-κB from cytoplasm to nucleus and lipid peroxidation were found to be inhibited whereas an increase in SOD, CAT, GSH and FRAP was observed in the mice treated with EC prior to irradiation. Thus, pre-treatment with EC offers protection against γ-radiation induced hepatic alterations. 相似文献
62.
The induction of L-phenylalanine ammonialyase (PAL, EC 4.3.1.5) and flavanone synthase in French bean cell suspension cultures in response to heat-released elicitor from cell walls of the phytopathogenic fungus Colletotrichum lindemuthianum is highly dependent upon elicitor concentration. The elicitor dose-response curve for PAL induction shows two maxima at around 17.5 and 50 g elicitor carbohydrate per ml culture, whereas the flavanone synthase response shows one maximum at around 100 g ml-1. The PAL response is independent of the elicitor concentration present during the lag phase of enzyme induction; if the initial elicitor concentration is increased after 2 h by addition of extra elicitor, or decreased by dilution of the cultures, the dose response curves obtained reflect the concentration of elicitor present at the time of harvest. PAL induction is not prevented by addition of methyl sugar derivatives to the cultures; -methyl-D-glucoside, itself a weak elicitor of PAL activity, elicits a multiphasic PAL response when increasing concentrations are added in the presence of Colletotrichum elicitor. Eight fractions with different monosaccharide compositions, obtained from the crude elicitor by gel-filtration, each elicit different dose-responses for PAL induction; the response to unfractionated elicitor is not the sum of the response to the isolated fractions. There is no correlation between the ability of the fractions to induce PAL in the cultures and their ability to act as elicitors of isoflavonoid phytoalexin accumulation in bean hypocotyls.Abbreviations PAL
phenylalanine ammonia-lyase
- PMS
Phytophthora megasperma var sojae 相似文献
63.
Summary The effect of histamine on cAMP and cGMP levels in day 6 (144 h post coitum) rabbit blastocysts was determined. Histamine at 200 M and 1000 M concentrations stimulated the increased formation of cAMP in vitro, whereas stimulation of cGMP occurred only in the presence of 1000 M histamine. Furthermore, intrauterine injection of RMI-12330A (50 g or 500 g/uterine horn), an inhibitor of adenylyl cyclase, on day 5 of pregnancy interrupted embryro development and implantation of the embryo. The drug was also effective in reducing the cAMP level in the endometrial cells in vitro. A relationship between histamine and cyclic nucleotide changes in embryo development and implantation is suggested. 相似文献
64.
Rouzer CA Kingsley PJ Wang H Zhang H Morrow JD Dey SK Marnett LJ 《The Journal of biological chemistry》2004,279(33):34256-34268
Comprehensive studies of prostaglandin (PG) synthesis in murine resident peritoneal macrophages (RPM) responding to bacterial lipopolysaccharide (LPS) revealed that the primary PGs produced by RPM were prostacyclin and PGE(2). Detectable increases in net PG formation occurred within the first hour, and maximal PG formation had occurred by 6-10 h after LPS addition. Free arachidonic acid levels rose and peaked at 1-2 h after LPS addition and then returned to baseline. Cyclooxygenase-2 (COX-2) and microsomal PGE synthase levels markedly increased upon exposure of RPM to LPS, with the most rapid increases in protein expression occurring 2-6 h after addition of the stimulus. RPM constitutively expressed high levels of COX-1. Studies using isoform-selective inhibitors and RPM from mice bearing targeted deletions of ptgs-1 and ptgs-2 demonstrated that COX-1 contributes significantly to PG synthesis in RPM, especially during the initial 1-2 h after LPS addition. Selective inhibition of either COX isoform resulted in increased secretion of tumor necrosis factor-alpha (TNF-alpha); however, this effect was much greater with the COX-1 than with the COX-2 inhibitor. These results demonstrate autocrine regulation of TNF-alpha secretion by endogenous PGs synthesized primarily by COX-1 in RPM and suggest that COX-1 may play a significant role in the regulation of the early response to endotoxemia. 相似文献
65.
Banerjee R Sreetama S Saravanan KS Dey SN Mohanakumar KP 《Neurochemical research》2007,32(7):1238-1247
The potent parkinsonian neurotoxin 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) is known to cause dopaminergic neurodegeneration
in nigrostriatal system. In the present study we investigated the nuclear morphology of cells in the substantia nigra pars
compacta (SNpc) region of rats following unilateral intranigral infusion of the active metabolite, 1-methyl-4-phenyl pyridinium
ion (MPP+), which resulted in a dose-dependent and prolonged dopamine depletion in the ipsilateral striatum. There appeared a substantial
loss of tyrosine hydroxylase immunoreactive neurons in the SNpc that received the neurotoxin. Specific nuclear staining with
Hoechst 33342 or acridine orange revealed bright pyknotic, shrunken, distorted nuclei and condensed chromatin with perinuclear
nucleolus respectively following visualization with the former and latter dyes in the ipsilateral SNpc, as compared to the
round, intact nuclei and centrally positioned nucleolus in the contralateral side. Ultrastructural details of the nucleus
under transmission electron microscope confirmed distorted nuclear organization with shrunken or condensed nuclei and disrupted
nuclear membrane. These features are typical of nucleus undergoing apoptosis, and suggest that MPP+ causes dopaminergic neuronal death through an apoptotic mode. Typical laddering pattern of genomic DNA isolated from the
ipsilateral SN in agarose gel electrophoresis conclusively established apoptosis following intranigral administration of MPP+ in rats.
Rebecca Banerjee and Sen Sreetama contributed equally to this paper. 相似文献
66.
67.
68.
Maher Alayyoubi Huatao Guo Sanghamitra Dey Talin Golnazarian Garrett A. Brooks Andrew Rong Jeffery F. Miller Partho Ghosh 《Structure (London, England : 1993)》2013,21(2):266-276
Highlights? bAvd forms a highly positively charged pentameric barrel ? bAvd binds both DNA and RNA, but without sequence preference ? The coding sequence for bAvd serves dual purposes ? The interaction of bAvd with bRT is likely to be important for retrohoming 相似文献
69.
Kow Jen Duan Dey Chyi Sheu Ming Tse Lin Hsiao Chiang Hsueh 《Biotechnology letters》1994,16(11):1151-1156
Summary An -glucosidase fromAspergillus carbonarious CCRC 30414 was employed for investigating the enzymatic synthesis of isomaltooligosaccharides from maltose. The enzyme transferred a glucose unit from the nonreducing end of maltose and other -linked glucosyl oligosaccharides to glucose and other glucosyl oligosaccharides which function as accepting co-substrates. The transfer of a glucose unit occurs most frequently to the 6-OH position of the nonreducing end of acceptor, but transfer to 4-OH position also occurs. Treatment of 30 % (w/v) maltose with the enzyme under optimum conditions afforded more than 50% isomaltooligosaccharides. 相似文献
70.