全文获取类型
收费全文 | 350篇 |
免费 | 41篇 |
出版年
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 6篇 |
2013年 | 32篇 |
2012年 | 18篇 |
2011年 | 24篇 |
2010年 | 13篇 |
2009年 | 5篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 18篇 |
2005年 | 16篇 |
2004年 | 14篇 |
2003年 | 9篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1996年 | 3篇 |
1994年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1963年 | 2篇 |
1961年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有391条查询结果,搜索用时 15 毫秒
1.
Plasmalemma Redox Chain and H Extrusion: II. Respiratory and Metabolic Changes Associated with Fusicoccin-Induced and with Ferricyanide-Induced H Extrusion 总被引:4,自引:1,他引:3
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)
Ferricyanide reduction by Elodea densa leaves is associated with a release of protons in the cytoplasm, a fraction of the increase in protons being then extruded by the ATP-driven proton pump (20). The data presented here show that ferricyanide induces a marked increase in O2 uptake, additive to that induced by fusicoccin plus K+, and here interpreted as depending on the utilization of ATP by the H+ pump. Glucose 6-phosphate and malate levels are markedly increased by fusicoccin plus K+. The simultaneous presence of ferricyanide reduces by about 50% the increase of malate, while it completely suppresses that of glucose 6-phosphate. The ferricyanide-induced decrease of malate is interpreted as due to the acidification of the cytosol associated with ferricyanide reduction, while the more marked decrease of glucose 6-phosphate might depend in part on the pH change and in part on a faster oxidation of this substrate. In fact, ferricyanide reduction is accompanied by a marked decrease of the incorporation into RNA ribose of C-1 as compared with C-2 of [14C]glucose. This suggests a stimulation of the release of C-1 as CO2 at the level of the glucose 6-phosphate oxidation pathway, as expected if NADPH was the electron donor for ferricyanide reduction. These results are interpreted as confirming that the H+ efflux associated with ferricyanide reduction depends on the activation of the ATP-driven plasmalemma H+ pump. They also suggest that NADPH is used as an electron donor to some initial component of the plasmalemma redox system. 相似文献
2.
Bendectin, composed of doxylamine succinate and pyridoxine HCl (1:1), is an antinauseant previously prescribed for nausea and vomiting during pregnancy. The present study examined the maternal and developmental effects of Bendectin (0, 200, 500, or 800 mg/kg/day, po) administered to timed-pregnant CD rats (36-41/group) during organogenesis (gestational days [gd] 6-15). At death (gd 20), all live fetuses were examined for external, visceral, and skeletal abnormalities. At 500 and 800 mg/kg/day, maternal toxicity included reduced food consumption during treatment and for the gestation period, increased water consumption in the posttreatment period, reduced weight gain during treatment, and sedation; water consumption was reduced during treatment and for the gestation period, and maternal mortality (17.1%) was observed only at the high dose. Developmental toxicity included reduced prenatal viability (800 mg/kg/day) and reduced fetal body weight/litter (500 and 800 mg/kg/day). In addition, reduced ossification of metacarpals (800 mg/kg/day), phalanges of the forelimbs (500 and 800 mg/kg/day), and of caudal vertebral centra (all doses) was observed. No increase in percent malformed live fetuses/litter was observed. The proportion of litters with one or more malformed fetuses was higher than vehicle controls only at 800 mg/kg/day, with short 13th rib (to which the test species is predisposed) as the predominant observation. By contrast, a positive control agent (nitrofen, 50 mg/kg/day, po, 14 dams) produced 85% malformed fetuses/litter with the predominant malformation being diaphragmatic hernia. In conclusion, the incidence of litters with one or more malformed fetuses was increased only at a dose of Bendectin which produced maternal mortality (17.1%) and other indices of maternal and developmental toxicity (see Discussion). 相似文献
3.
A species of Prorocentrum (Dinophyta, Prorocentrales), isolated from a phytoplankton net sample from the Atlantic coast of Nova Scotia, has been brought
into unialgal culture. The sample was collected at an aquaculture site immediately following an incident of diarrhetic shellfish
poisoning (DSP) due to the consumption of contaminated mussels. This clonal isolate has been identified as P. lima, based on its morphological characteristics. Analysis of the culture extract, using high performance liquid chromatography
(HPLC) with fluorescence detection, indicated the presence of the DSP toxins, okadaic acid (OA) and dinophysistoxin-1 (DTX-1). 相似文献
4.
5.
Nuclear protein import in permeabilized mammalian cells requires soluble cytoplasmic factors 总被引:94,自引:41,他引:53
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have developed an in vitro system involving digitonin-permeabilized vertebrate cells to study biochemical events in the transport of macromolecules across the nuclear envelope. While treatment of cultured cells with digitonin permeabilizes the plasma membranes to macromolecules, the nuclear envelopes remain structurally intact and nuclei retain the ability to transport and accumulate proteins containing the SV40 large T antigen nuclear location sequence. Transport requires addition of exogenous cytosol to permeabilized cells, indicating the soluble cytoplasmic factor(s) required for nuclear import are released during digitonin treatment. In this reconstituted import system, a protein containing a nuclear location signal is rapidly accumulated in nuclei, where it reaches a 30-fold concentration compared to the surrounding medium within 30 min. Nuclear import is specific for a functional nuclear location sequence, requires ATP and cytosol, and is temperature dependent. Furthermore, accumulation of the transport substrate within nuclei is completely inhibited by wheat germ agglutinin, which binds to nuclear pore complexes and inhibits transport in vivo. Together, these results indicate that the permeabilized cell system reproduces authentic nuclear protein import. In a preliminary biochemical dissection of the system, we observe that the sulfhydryl alkylating reagent N-ethylmaleimide inactivates both cytosolic factor(s) and also component(s) in the insoluble permeabilized cell fraction required for nuclear protein import. Because this permeabilized cell model is simple, efficient, and works effectively with cells and cytosol fractions prepared from a variety of different vertebrate sources, it will prove powerful for investigating the biochemical pathway of nuclear transport. 相似文献
6.
Purine metabolism in Toxoplasma gondii 总被引:11,自引:0,他引:11
We have studied the incorporation and interconversion of purines into nucleotides by freshly isolated Toxoplasma gondii. They did not synthesize nucleotides from formate, glycine, or serine. The purine bases hypoxanthine, xanthine, guanine, and adenine were incorporated at 9.2, 6.2, 5.1, and 4.3 pmol/10(7) cells/h, respectively. The purine nucleosides adenosine, inosine, guanosine, and xanthosine were incorporated at 110, 9.0, 2.7, and 0.3 pmol/10(7) cells/h, respectively. Guanine, xanthine, and their respective nucleosides labeled only guanine nucleotides. Inosine, hypoxanthine, and adenine labeled both adenine and guanine nucleotide pools at nearly equal ratios. Adenosine kinase was greater than 10-fold more active than the next most active enzyme in vitro. This is consistent with the metabolic data in vivo. No other nucleoside kinase or phosphotransferase activities were found. Phosphorylase activities were detected for guanosine and inosine; no other cleavage activities were detected. Deaminases were found for adenine and guanine. Phosphoribosyltransferase activities were detected for all four purine nucleobases. Interconversion occurs only in the direction of adenine to guanine nucleotides. 相似文献
7.
Investigation of the role of the disulphide bond in the activity and structure of staphylococcal enterotoxin C1 总被引:13,自引:0,他引:13
Carolyn J. Hovde James C. Marr Marcy L. Hoffmann Sean P. Hackett Young-in Chi Kimberlee K. Crum Dennis L. Stevens Cynthia V. Stauffacher Gregory A. Bohach 《Molecular microbiology》1994,13(5):897-909
The goal of this study was to Investigate the role of the disulphide bond of staphylococcal enterotoxin C1 (SEC1) in the structure and activity of the toxin. Mutants unable to form a disulphide bond were generated by substituting alanine or serine for cysteine at positions 93 and/or 110. Although we did not directly investigate the residues between the disulphide linkage, tryptic lability showed that significant native structure in the cystine loop is preserved in the absence of covalent bonding between residues 93 and 110. Since no correlation was observed between the behaviour of these mutants with regard to toxin stability, emesis and T cell proliferation, we conclude that SEC1 -induced emesis and T cell proliferation are dependent on separate regions of the molecule. The disulphide bond itself is not an absolute requirement for either activity. However, conformation within or adjacent to the loop is important for emesis. Although mutants with alanine substitutions were not emetic, those with serine substitutions retained this activity, suggesting that the disulphide linkage stabilizes a crucial conformation but can be replaced by residues which hydrogen bond. 相似文献
8.
Identification of a ClpC ATPase required for stress tolerance and in vivo survival of Listeria monocytogenes 总被引:1,自引:0,他引:1
9.
Evidence for Linkage of Bipolar Disorder to Chromosome 18 with a Parent-of-Origin Effect 总被引:16,自引:8,他引:8
下载免费PDF全文
![点击此处可从《American journal of human genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
O. Colin Stine Jianfeng Xu Rebecca Koskela Francis J. McMahon Michele Gschwend Carl Friddle Chris D. Clark Melvin G. McInnis Sylvia G. Simpson Theresa S. Breschel Eva Vishio Kelly Riskin Harriet Feilotter Eugene Chen Susan Shen Susan Folstein Deborah A. Meyers David Botstein Thomas G. Marr J. Raymond DePaulo 《American journal of human genetics》1995,57(6):1384-1394
A susceptibility gene on chromosome 18 and a parent-of-origin effect have been suggested for bipolar affective disorder (BPAD). We have studied 28 nuclear families selected for apparent unilineal transmission of the BPAD phenotype, by using 31 polymorphic markers spanning chromosome 18. Evidence for linkage was tested with affected-sib-pair and LOD score methods under two definitions of the affected phenotype. The affected-sib-pair analyses indicated excess allele sharing for markers on 18p within the region reported previously. The greatest sharing was at D18S37: 64% in bipolar and recurrent unipolar (RUP) sib pairs (P = .0006). In addition, excess sharing of the paternally, but not maternally, transmitted alleles was observed at three markers on 18q: at D18S41, 51 bipolar and RUP sib pairs were concordant for paternally transmitted alleles, and 21 pairs were discordant (P = .0004). The evidence for linkage to loci on both 18p and 18q was strongest in the 11 paternal pedigrees, i.e., those in which the father or one of the father's sibs is affected. In these pedigrees, the greatest allele sharing (81%; P = .00002) and the highest LOD score (3.51; θ = 0.0) were observed at D18S41. Our results provide further support for linkage of BPAD to chromosome 18 and the first molecular evidence for a parent-of-origin effect operating in this disorder. The number of loci involved, and their precise location, require further study. 相似文献
10.
It was shown in an investigation of the phosphofructokinases of Leishmania donovani and Leishmania braziliensis that both enzymes are similar to that of Crithidia fasciculata. Although the enzymes are allosteric with respect to their substrates and require AMP for activation, there is no influence by other heterotropic modifiers. The Mg2+-ATP chelate activates these enzymes in a first order process and they can be inhibited by free ATP. The inhibition is reversed by the activator, AMP, in a competitive manner. The requirement for the nucleotide in L. donovani can be eliminated by decreasing the pH. The data indicate that phosphofructokinase, a pivotal enzyme in glycolysis for most organisms, probably does not play an important role in glycolysis in Leishmania. 相似文献