全文获取类型
收费全文 | 496篇 |
免费 | 48篇 |
出版年
2021年 | 7篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 17篇 |
2014年 | 19篇 |
2013年 | 19篇 |
2012年 | 28篇 |
2011年 | 25篇 |
2010年 | 24篇 |
2009年 | 19篇 |
2008年 | 28篇 |
2007年 | 10篇 |
2006年 | 21篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 17篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 11篇 |
1972年 | 11篇 |
1971年 | 8篇 |
1970年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有544条查询结果,搜索用时 15 毫秒
11.
N J Nadler 《The Journal of cell biology》1971,49(3):877-882
12.
13.
Molecular evidence for Acanthocephala as a subtaxon of Rotifera 总被引:7,自引:0,他引:7
James R. Garey Thomas J. Near Michael R. Nonnemacher Steven A. Nadler 《Journal of molecular evolution》1996,43(3):287-292
Rotifers are free-living animals usually smaller than 1 mm that possess a characteristic wheel organ. Acanthocephalans (thorny-headed
worms) are larger endoparasitic animals that use vertebrates and arthropods to complete their life cycle. The taxa Acanthocephala
and Rotifera are considered separate phyla, often within the taxon Aschelminthes. We have reexamined the relationship between
Rotifera and Acanthocephala using 18S rRNA gene sequences. Our results conclusively show that Acanthocephala is the sister
group of the rotifer class Bdelloidea. Rotifera was nonmonophyletic in all molecular analyses, which supports the hypothesis
that the Acanthocephala represent a taxon within the phylum Rotifera and not a separate phylum. These results agree with a
previous cladistic study of morphological characters.
Correspondence to: J.R. Garey 相似文献
14.
Steven A. Nadler Mark S. Hafner John C. Hafner David J. Hafner 《Evolution; international journal of organic evolution》1990,44(4):942-951
Genetic variation among populations of chewing lice (Geomydoecus actuosi) was examined in relation to chromosomal and electrophoretic variation among populations of their hosts (Thomomys bottae) at a contact zone. Louse demes were characterized by low levels of genetic heterozygosity (H? = 0.039) that may result from founder effects during primary infestation of hosts, compounded by seasonal reductions in louse population size. Louse populations sampled from different hosts showed high levels of genetic structuring both within and among host localities. Microgeographic differentiation of louse populations is high (mean FST = 0.092) suggesting that properties of this host–parasite system promote differentiation of louse populations living on different individual hosts. Among-population differentiation in lice (FST = 0.240) was similar to that measured among host populations (FST = 0.236), suggesting a close association between gene flow in pocket gophers and gene flow in their lice. 相似文献
15.
R D Nadler C Roth-Meyer J Wallis W Cooper E Bourreau G Affre E E Baulieu 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1984,298(14):409-413
Ten male and eleven female Chimpanzees from three to nine years of age were studied to establish possible correlations between behavioral changes and hormonal changes peculiar to adrenarche and the pre-puberty period. Most of the thirteen behaviors studied varied with age, body weight and hormones. For the males, the correlations were significant statistically for age, weight and plasma concentration of testosterone and of FSH. The correlations for the females were more often not significant statistically. In ten out of the thirteen behaviors for the female, however, the correlations with the sulfate of plasma dehydroepiandrosterone were in the same direction as those observed for the males with testosterone. 相似文献
16.
Galactosylceramide β-galactosidase (EC 3.2.1.46) has been partially purified from liver of a patient who died of Krabbe disease. Approximately 700-fold purification was achieved by solubilization, adsorption with immobilized concanavalin A, gel filtration through Bio-Gel A-1.5m and chromatography on immobilized sphingosine. The relative increase in crossreacting material and residual galactosylceramidase and lactosylceramidase I activities of the mutant enzyme was essentially identical to that obtained for the enzyme partially purified by the same procedure from normal liver control. An apparent molecular weight of about 750,000 and similar electrophoretic mobilities were observed for both enzymes. In contrast, catalytic properties and stability of the enzyme protein were severely affected in the mutant as compared to the normal enzyme. The apparent Km values of the mutant enzyme for β-galactosidase activities toward galactosylceramide and lactosylceramide in the presence of pure sodium taurocholate were 14 and 4 times, respectively, higher than the normal values. Incubation for 4 min at 52 °C or dialysis against 1.3 m urea caused a 50% loss of residual enzymatic activity of the mutant enzyme, whereas a 35-min incubation or dialysis against 5.6 m urea was required for 50% inactivation of the normal enzyme. These findings indicate that the mutation in Krabbe disease leads to synthesis of normal quantities of catalytically and structurally altered protein. 相似文献
17.
Claramma M. Chacko Rebecca S. Wappner Ira K. Brandt Henry L. Nadler 《Human genetics》1977,37(3):261-270
Summary A new variant of clinical galactosemia with two hitherto unidentified alleles on the transferase locus in one family is described. This new clinical variant of transferase has 25% of normal control activity in blood and in skin fibroblasts, and the patient accumulates galactose-1-phosphate in blood on an unrestricted galactose diet. Using starch gel electrophoresis on the hemolysate of the family members, a fast-moving transferase with mobility in between those of the normal control and of the Duarte variant is identified. This new allele is designated as
(fast-moving Chicago variant). In addition, a second new allele was documented in this family by studying the instability of the transferase enzyme in hemolysates of family members at 50°C for various time intervals. This new allele is designated as
(heat-labile Chicago variant). On the basis of the studies, the transferase genotype of this patients is thought to be a double heterozygote compound,
/GALTG. 相似文献
18.
Selective induction of B7/BB-1 on interferon-gamma stimulated monocytes: a potential mechanism for amplification of T cell activation through the CD28 pathway. 总被引:19,自引:0,他引:19
The B cell activation antigen B7/BB-1 is the natural ligand for the T cell antigen CD28 and these two molecules are capable of mediating T-B cell adhesion. Engagement of the CD28 pathway provides a costimulatory signal to T cells leading to enhanced lymphokine production. We report that interferon-gamma (INF-gamma) induces the expression of B7/BB-1 on monocytes. This induction was very specific since other cytokines and stimuli which activate monocytes including M-CSF, GM-CSF, IL3, TNF-alpha, and LPS were unable to induce B7/BB-1. Following culture of monocytes with INF-gamma, maximal mRNA and cell surface B7/BB-1 expression was detected at 12 and 24 hr, respectively. In addition to antigen presentation, optimal T cell activation and lymphokine synthesis require an additional cell to cell contact signal provided by the antigen presenting cell. The induction of B7/BB-1 on monocytes and subsequent heterophilic interaction of B7/BB-1 with CD28 may provide a mechanism for the amplification of T cell proliferation and lymphokine production by INF-gamma activated monocytes. 相似文献
19.
The binding of 22 human liver hydrolase activities by immobilized lectins of six different carbohydrate specificities, namely alpha-D-mannose (glucose), D-N-acetylglucosamine, D-N-acetylgalactosamine, L-fucose, alpha-D-galactose and beta-D-galactose, were examined. Differences in binding among these enzymes and within specific enzymes were observed. For example, the neutral forms of alpha-mannosidase and beta-xylosidase were bound by the Ulex europaeus lectin I (specific for L-fucose), whereas the acidic forms were not. Bandierea simplicifolia lectin (specific for alpha-galactose) bound 65% of beta-glucuronidase activity; recycling experiments demonstrated complete binding of the enzyme that had been eluted with the competitor D-galactose and no binding of the fraction that was not initially bound. These results suggested the presence of two forms of this enzyme. Similar data were obtained for acidic beta-galactosidase activity. These experiments may provide the basis for the expanded use of immobilized lectins for purification and characterization of hydrolases and other glycoproteins. 相似文献
20.
Mannosidosis: separation and characterization of two acid alpha-mannosidase forms in mutant fibroblasts 总被引:2,自引:0,他引:2
Two acidic forms of alpha-mannosidase activity, A and B, are separated and characterized in fibroblasts from controls and patients with mannosidosis. In normal cells, A and B differ in adsorption on DEAE-cellulose, electrophoretic mobility, stability at 70 degrees C and resistance to freezing at --20 degrees C. In 5 of 6 mutant cell lines, A and B both exhibit altered Km's for artificial substrates and decreased thermal stability. Zn2+ has no effect on A or B in mutant or normal cells. In contrast, Co2+ slightly inhibits B in normal cells but markedly enhances the activity of B in mutant cells. The mutation in mannosidosis clearly results in an alteration in the biochemical characteristics of both major acidic forms of alpha-mannosidase. 相似文献