全文获取类型
收费全文 | 2079篇 |
免费 | 105篇 |
国内免费 | 3篇 |
出版年
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 18篇 |
2018年 | 30篇 |
2017年 | 16篇 |
2016年 | 38篇 |
2015年 | 77篇 |
2014年 | 71篇 |
2013年 | 145篇 |
2012年 | 144篇 |
2011年 | 119篇 |
2010年 | 74篇 |
2009年 | 103篇 |
2008年 | 131篇 |
2007年 | 146篇 |
2006年 | 130篇 |
2005年 | 137篇 |
2004年 | 135篇 |
2003年 | 130篇 |
2002年 | 131篇 |
2001年 | 15篇 |
2000年 | 10篇 |
1999年 | 21篇 |
1998年 | 32篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 25篇 |
1994年 | 11篇 |
1993年 | 22篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1965年 | 3篇 |
1963年 | 2篇 |
排序方式: 共有2187条查询结果,搜索用时 15 毫秒
1.
Comparisons among 16S rRNA sequences from various eubacteria reveal a natural relationship between the bacteroides (represented by the Bacteroides fragilis sequence) and a phylogenetic unit that comprises the flavobacteria, cytophagae, flexibacteria, and others (represented by the Flavobacterium heparinum sequence). Although the relationship is not a close one, it is, nevertheless, specific. rRNAs from these two organisms are not only closer to one another in overall sequence than they are to outgroup species (such as Bacillus subtilis, Escherichia coli, Desulfovibrio desulfuricans, and Agrobacterium tumefaciens), but they show common idiosyncrasies (i.e., derived characteristics) in both rRNA sequences and higher-order structures. 相似文献
2.
3.
Circulating tumor cells (CTCs), shed from primary tumors and disseminated into peripheral blood, are playing a major role in metastasis. Even after isolation of CTCs from blood, the target cells are mixed with a population of other cell types. Here, we propose a new method for analyses of cell mixture at the single-cell level using a microfluidic device that contains arrayed electroactive microwells. Dielectrophoretic (DEP) force, induced by the electrodes patterned on the bottom surface of the microwells, allows efficient trapping and stable positioning of single cells for high-throughput biochemical analyses. We demonstrated that various on-chip analyses including immunostaining, viability/apoptosis assay and fluorescent in situ hybridization (FISH) at the single-cell level could be conducted just by applying specific reagents for each assay. Our simple method should greatly help discrimination and analysis of rare cancer cells among a population of blood cells. 相似文献
4.
5.
Summary An activated carbon column was utilized for the synthesis of disaccharides by use of a reversed hydrolysis activity of an immobilized -galactosidase column in order to shift the equilibrium to the direction of condensation. The yields of lactulose and allo-lactulose from galactose and fructose, and N-acetyl lactosamine and N-acetyl allolactosamine from galactose and N-acetyl glucosamine, were 11.3% and 10.0%, respectively. 相似文献
6.
Abstract Biovar A strains of Fusobacterium necrophorum exhibited high hydrophobicity when examined by the method of Rosenberg et al. Biovar B strains showed a lower cell surface hydrophobicity than biovar A strains. Biovar B strains were divided into 2 groups according to their hydrophobic activity. The strains of biovar A and the first group of biovar B were increasingly removed from aqueous phase to octane phase by increasing the volume of octane, but the turbidity of the second group of biovar B was not significantly affected. The hydrophobicity of biovar A strains decreased on heating at 60 and 100°C for 30 min. 相似文献
7.
E Yabuuchi I Yano H Oyaizu Y Hashimoto T Ezaki H Yamamoto 《Microbiology and immunology》1990,34(2):99-119
8.
Oka Kotaro; Ikeshima Hiroko; Ishikawa Hideo; Ohta Eiji; Sakata Makoto 《Plant & cell physiology》1988,29(5):771-775
We showed that the surface charge density of protoplasts canbe estimated by the 9-aminoacridine method. The estimated surfacecharge density of the protoplasts isolated from elongating regionsof Vigna mungo root was 39 ? 8 mC/m2. The negative surfacecharge density increased when protoplasts were treated withglutaraldehyde or when EDTA was added to the protoplast suspensionmedium. These results support the validity of our estimationof the surface charge density of protoplasts by the 9-aminoacridinemethod. The concentration of amino groups at the surface ofthe protoplasts was estimated to be 34 mC/m2. (Received June 19, 1987; Accepted April 11, 1988) 相似文献
9.
E Yabuuchi Y Kosako H Oyaizu I Yano H Hotta Y Hashimoto T Ezaki M Arakawa 《Microbiology and immunology》1992,36(12):1251-1275
Based on the 16S rRNA sequences, DNA-DNA homology values, cellular lipid and fatty acid composition, and phenotypic characteristics, a new genus Burkholderia is proposed for the RNA homology group II of genus Pseudomonas. Seven species in this group were transferred to the new genus. Thus seven new combinations, Burkholderia cepacia (Palleroni and Holmes 1981), Burkholderia mallei (Zopf 1885), Burkholderia pseudomallei (Whitmore 1913), Burkholderia caryophylli (Burkholder 1942), Burkholderia gladioli (Severini 1913), Burkholderia pickettii (Ralston et al 1973) and Burkholderia solanacearum (Smith 1896) were proposed. 相似文献
10.
Human immunodeficiency virus type 1 envelope glycoproteins gp120 and gp160 induce interleukin-6 production in CD4+ T-cell clones. 下载免费PDF全文
Polyclonal B-cell activation is a characteristic feature of AIDS and of the AIDS-related complex. Since the immunoregulatory cytokine interleukin-6 (IL-6) plays a major role in inducing B-cell differentiation, we examined the effects of native human immunodeficiency virus type 1 envelope glycoproteins gp120 and gp160 on IL-6 induction. In this study, we have demonstrated that both gp120 and gp160 have the ability to induce IL-6 mRNA and biologically active IL-6 protein secretion in peripheral blood mononuclear cells in vitro. The envelope protein preparations had no detectable endotoxin as tested by the Limulus amebocyte lysate assay, and hence we can rule out the effect of contaminating endotoxin, which is a potent inducer of IL-6 in monocyte/macrophage cell cultures. In addition, we have shown that the envelope glycoproteins act directly on CD4(+)-cloned T cells to induce IL-6 production in the absence of monocytes. These findings indicate that monocytes and T cells both contribute to the secretion of IL-6, which plays an important role in the pathogenesis of B-cell activation in human immunodeficiency virus infection. 相似文献