全文获取类型
收费全文 | 652篇 |
免费 | 48篇 |
国内免费 | 1篇 |
出版年
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 20篇 |
2014年 | 21篇 |
2013年 | 47篇 |
2012年 | 37篇 |
2011年 | 49篇 |
2010年 | 30篇 |
2009年 | 28篇 |
2008年 | 38篇 |
2007年 | 44篇 |
2006年 | 41篇 |
2005年 | 29篇 |
2004年 | 28篇 |
2003年 | 29篇 |
2002年 | 23篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有701条查询结果,搜索用时 15 毫秒
1.
Sympathoadrenergic pathways are crucial to the communication between the nervous system and the immune system. The present review addresses emerging issues in the adrenergic modulation of immune cells, including: the specific pattern of adrenoceptor expression on immune cells and their role and changes upon cell differentiation and activation; the production and utilization of noradrenaline and adrenaline by immune cells themselves; the dysregulation of adrenergic immune mechanisms in disease and their potential as novel therapeutic targets. A wide array of sympathoadrenergic therapeutics is currently used for non-immune indications, and could represent an attractive source of non-conventional immunomodulating agents. 相似文献
2.
Piero A. Battaglia Franca Gigliani Liana Marcucci Raffaella Elli 《Molecular & general genetics : MGG》1987,209(1):41-48
Summary By using an artificial hybrid between phage and the pR plasmid, we have shown that the rep region of the pR plasmid encodes a function which regulates the expression of the muc genes (plasmid genes that are under the negative control of lexA and responsible for an increased rate of spontaneous mutagenesis and resistance to UV and chemicals). Expression of the muc genes was monitored by a fusion between the muc promoter and the lacZ structural gene. When E. coli cells containing such a fusion are infected by the hybrid pR phasmid, -galactosidase activity is enhanced, indicating that pR encodes an antagonist of lexA. By deletion mapping we have located the gene encoding the antagonist of lexA (bat) in the rep region of the plasmid. The bat gene product can also antagonize the cI repressor as shown by the observation that pR phasmids are virulent on a homoimmune lysogen. We have exploited this latter property to carry out genetic and functional analysis of the bat region. This region is organized as a classical operon where the expression of the bat structural gene is negatively regulated by a repressor gene that encodes a proteic product. 相似文献
3.
The characteristics of fusicoccin binding were investigated in microsomes from 24-h-old radish (Raphanus sativus L.) seedlings. The time course of fusicoccin binding depended on fusicoccin concentration: equilibrium was reached much faster at 10 nanomolar fusicoccin than at 0.3 nanomolar fusicoccin. Scatchard analysis of equilibrium binding as a function of fusicoccin concentration indicated a single class of receptor sites with a Kd of 1.8 nanomolar and a site density of 6.3 picomoles per milligram protein. Similar values (Kd 1.7 nanomolar and site density 7 picomoles per milligram protein) were obtained from the analysis of the dependence of equilibrium binding on membrane concentration at fixed fusicoccin concentrations. Fusicoccin binding comigrated with the plasma membrane H+-ATPase in an equilibrium sucrose density gradient: both activities formed a sharp peak (1.18 grams per milliliter) clearly distinct from that of markers of other membranes which all peaked at lower densities. The saturation profiles of fusicoccin binding and of fusicoccin-induced activation of the plasma membrane H+-ATPase, measured under identical conditions, were similar, supporting the view that fusicoccin-induced activation of the plasma membrane H+-ATPase is mediated by fusicoccin binding to its plasma membrane receptor. 相似文献
4.
Bruno Biavati Franca Crociani Paola Mattarelli Dr. Vittorio Scardovi 《Current microbiology》1992,25(1):51-55
Strains isolated from rabbit, chicken, and rat feces and from sewage and fermented milk products, all identified asBifidobacterium animalis, were found to show phase variations in colony appearance and in cellular morphology. The rate of transition in a switching system from opaque to transparent colonies and vice versa was determined. Differences in protein components and in penicillin-binding proteins (PBPs) of the cells from different colony types are shown. 相似文献
5.
Rita Businaro Evandro Fioretti Lorenzo Fumagalli Gennaro Citro Gabriella De Renzis Franca Ascoli 《The Histochemical journal》1988,20(4):187-193
Summary In addition to bovine pancreatic trypsin inhibitor (BPTI), three BPTI-related molecular forms (isoinhibitors I, II and III) were isolated from bovine lung by affinity chromatography on immobilized trypsin and subsequently purified by Fast Protein Liquid Chromatography. These inhibitors are identical to the isoinhibitors previously isolated from bovine spleen. Their localization in bovine lung was studied by immunohistochemical techniques, using two different immunoglobulin preparations, selectively recognizing BPTI or the other molecular forms.BPTI-related immunoreactivity was found to be restricted to isolated cells, often identified as mast cells by Toluidine Blue staining. In contrast, isoinhibitor-related immunoreactivity, which also occurs in the mast cells, is present in a number of other cell types. These types include: (i) the smooth muscle cells of different calibre vessels, (ii) the ciliated cells of the bronchial epithelium and the related mucus, and (iii) many cells at alveolar level.Comparison of these data with previous results obtained for bovine spleen suggest multiple physiological roles for these inhibitors. 相似文献
6.
Electrogenic transport of protons driven by the plasma membrane ATPase in membrane vesicles from radish : biochemical characterization 总被引:10,自引:9,他引:1
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mg:ATP-dependent H+ pumping has been studied in microsomal vesicles from 24-hour-old radish (Raphanus sativus L.) seedlings by monitoring both intravesicular acidification and the building up of an inside positive membrane potential difference (Δ ψ). ΔpH was measured as the decrease of absorbance of Acridine orange and Δ ψ as the shift of absorbance of bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol. Both Mg:ATP-dependent Δ pH and Δ ψ generation are completely inhibited by vanadate and insensitive to oligomycin; moreover, Δ pH generation is not inhibited by NO3−. These findings indicate that this membrane preparation is virtually devoid of mitochondrial and tonoplast H+-ATPases. Both intravesicular acidification and Δ ψ generation are influenced by anions: Δ pH increases and Δ ψ decreases following the sequence SO42−, Cl−, Br−, NO3−. ATP-dependent H+ pumping strictly requires Mg2+. It is very specific for ATP (apparent Km 0.76 millimolar) compared to GTP, UTP, CTP, ITP. Δ pH generation is inhibited by CuSO4 and diethylstilbestrol as well as vanadate. Δ pH generation is specificially stimulated by K+ (+ 80%) and to a lesser extent by Na+ and choline (+28% and +14%, respectively). The characteristics of H+ pumping in these microsomal vesicles closely resemble those described for the plasma membrane ATPase partially purified from several plant materials. 相似文献
7.
Annarosa Selli Franca Crociani Diego Matteuzzi Giorgio Crisetig 《Current microbiology》1986,13(1):33-38
Feedback inhibition of crude and purified extracts of homoserine dehydrogenase and threonine deaminase activities in the genusBifidobacterium was studied. Homoserine dehydrogenase was partially or completely inhibited byl-threonine, and a marked inhibitory effect byl-isoleucine on threonine deaminase was observed. In the speciesBifidobacterium cuniculi high levels ofl-valine reversed the inhibitory effect ofl-isoleucine. The -aminobutyric acid-resistant mutant Ru 326/106 of the speciesB. ruminale, overproducer ofl-isoleucine, had a derepressed homoserine dehydrogenase and a lesser feedback inhibition byl-threonine. Homoserine dehydrogenase appeared to be in bifids specifically NAD dependent. The regulatory mechanisms of aspartate family amino acid biosynthesis in bifidobacteria was discussed. 相似文献
8.
Gianni Bonadonna Silvio Monfardini Mario de Lena Franca Fossati-Bellani 《BMJ (Clinical research ed.)》1969,3(5669):503-506
Adriamycin, a new antitumour antibiotic of the anthracycline group with a structural formula very similar to daunorubicin, has proved to have potent tumour-growth-inhibiting properties, and to be particularly effective in childhood malignancies. Though adriamycin produces a higher percentage of side-effects than daunorubicin—namely, stomatitis and alopecia—a lower dosage may be used for therapy. 相似文献
9.
Duplication of an Xp segment that includes the ZFX locus causes sex inversion in man 总被引:6,自引:6,他引:0
Gerd Scherer Werner Schempp Carlo Baccichetti Elisabetta Lenzini Franca Dagna Bricarelli Laura Doria Lamba Carbone Ulrich Wolf 《Human genetics》1989,81(3):291-294
Summary Two 46,XY females with tandem duplications of an X short arm segment were studied by cytogenetic and Southern blot analysis. The results show that the duplicated segment in each case included the Xp21.2–Xp22.2 interval, resulting in a double dose of ZFX on the single active X chromosome. The results from our two cases, in conjunction with those reported by other workers, lead us to conclude that the duplication is the reason for the sex inversion. If ZFY and ZFX are indeed sex-determining gene loci, these findings favour a model of sex determination characterized by antagonistic interaction between these genes. 相似文献
10.
Guerrini Franca; Lombini Alessandra; Bizarri Mariachiara; Pupillo Paolo 《Journal of experimental botany》1994,45(9):1227-1233
Cell suspension cultures of Beta vulgaris L., treated with calciumchelators or untreated, were used to characterize pyndine nucleotide-dependentdiaphorases of microsomes. The microsomal activity of NADH-dependentduroquinone reductase from cultures treated with 10 mM Na2EGTAfor 24 h increased by a factor of 1.8 with respect to controlmicrosomes, and was mainly associated with particles of d=1.17gml1. NADPH-duroquinone reductase and NADH-ferricyanidereductase activities showed smaller increases. Bacterial protein-lipopolysaccharidecomplexes (prLPS) also promoted the increase of microsomal diaphorases;CaEGTA was Ineffective. EGTA effects on enzymes of supernatantand mitochondria were negligible, although Na2EGTA treatmentinduced cell aggregation and strong acidification of the medium. When microsomes from control cultures were solubilized with1% LPC and fractionated in high-efficiency gel permeation columns(FPLC) the diaphorase activities were found associated to threemajor proteins: (i) NADH-specific quinone reductase (NADH-QR)of 340 kDa; (ii) pyndine nucleotide-nonspecific quinone reductase(NAD(P)H-QR) of 85 kDa also having ferricyanide reductase activity;(iii) NADH-specific ferricyanide reductase (NADH-FCR) of 38kDa. The microsomes from EGTA-treated cells also showed a highlyactive NADH-QR having a larger molecular mass (440 kDa) thanin control cells. NAD(P)H-QR also showed increased activity.We conclude that external Ca2+ chelation induces changes indehydrogenase components in microsomes. Furthermore, prLPS probablyexert part of their effect on plants through Ca2+ chelation. Key words: Beta vulgaris, cell cultures, calcium chelators, diaphorase, NAD(P)H-dehydrogenase, lipopolysaccharide, EGTA, quinone reductase 相似文献