全文获取类型
收费全文 | 563篇 |
免费 | 31篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 23篇 |
2014年 | 33篇 |
2013年 | 44篇 |
2012年 | 40篇 |
2011年 | 56篇 |
2010年 | 25篇 |
2009年 | 24篇 |
2008年 | 29篇 |
2007年 | 37篇 |
2006年 | 30篇 |
2005年 | 19篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1970年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有594条查询结果,搜索用时 15 毫秒
1.
Abundant alkali-sensitive sites in DNA of human and mouse sperm 总被引:18,自引:0,他引:18
Narendra P. Singh David B. Danner Raymond R. Tice Michael T. McCoy Gary D. Collins Edward L. Schneider 《Experimental cell research》1989,184(2):461-470
The DNA of human and mouse sperm cells was analyzed by single-cell microgel electrophoresis, by agarose gel electrophoresis, and by alkaline elution--three techniques that can detect single-strand DNA breaks and/or labile sites. Under these conditions a surprisingly large number of single-strand DNA breaks, approximately 10(6) to 10(7) per genome, were detected in human and mouse sperm but not in human lymphocytes or in mouse bone marrow cells. These breaks were also present in chicken erythrocyte DNA, which is also highly condensed. These breaks were not observed under neutral pH conditions nor under denaturing conditions not involving alkali, suggesting that these sites are alkali-sensitive and do not represent preexisting single-strand breaks. The high frequency of such sites in sperm from healthy mouse and human donors suggests that they represent a functional characteristic of condensed chromatin rather than DNA damage. 相似文献
2.
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
3.
The distance geometry approach for computing the tertiary structure of globular proteins emphasized in this series of papers (Goelet al., J. theor. Biol. 99, 705–757, 1982) is developed further. This development includes incorporation of some secondary structure information—the location of alpha helices in the primary sequence—in the algorithm to compute the tertiary structure of alpha helical globular proteins. An algorithm is developed which estimates the interresidue distances between chain-proximate helices. These distances, in conjunction with the global statistical average distances obtainable from a database of real proteins and determined by the primary sequence of the protein under study, are used to determine the tertiary structure. Five proteins, parvalbumin, hemerythrin, human hemoglobin, lamprey hemoglobin, and sperm whale myoglobin, are investigated. The root mean square (RMS) errors between the calculated structures and those determined by X-ray diffraction range from 4.78 to 7.56 Å. These RMSs are 0.21–2.76 Å lower than those estimated without the secondary structure information. Contact maps and three-dimensional backbone representations also show considerable improvements with the introduction of secondary structure information. 相似文献
4.
Narendra S. Goel Carlos F. Doggenweiler Richard L. Thompson 《Bulletin of mathematical biology》1986,48(2):167-187
A model based upon minimization of surface energy is proposed as an explanation for compaction and internalization of cells
during mammalian embryo development. The model is used to simulate and graphically display these phenomena on a computer. 相似文献
5.
The effect of foliar sprays of the growth regulator 2-(3,4 dichlorophenoxy)-triethylamine (DCPTA) on net photosynthesis (Pn) by intact bean plants depended upon concentration and the stage of development of the leaves. A single foliar spray of 2.0 mM DCPTA reduced Pn when applied to young expanding leaves but had little effect on fully expanded leaves. Lower DCPTA concentrations (0.2 to 0.8 mM) had no effect on Pn, unless applied more than once which resulted in reduced Pn. The DCPTA-induced inhibition of Pn was associated with chlorosis and aberrations in chloroplast ultrastructure. DCPTA did not affect stomatal resistance. When applied to detached leaf disks in the dark, DCPTA retarded the normal loss of chlorophyll suggesting that DCPTA may have anti-seneseent properties.Abbreviations DCPTA
2-(3,4 dichlorophenoxy)-triethylamine
- Pn
net photosynthesis
- Is
stomatal diffusive resistance 相似文献
6.
Mycopathologia - A new entomogenous species ofPhoma, P. aspidioticola, has been described on a scale insect (Aspidiotus destructor Sign.) from India on the basis of morphological characters and... 相似文献
7.
Alterations in cell membrane structure and expression of a membrane-associated protein after adaptation to osmotic stress 总被引:3,自引:0,他引:3
8.
Renu Tuteja Narendra Tuteja Franco Lilliu Bruno Bembi Renzo Galanello Antonio Cao Francisco E. Baralle 《Human genetics》1994,94(3):314-315
We report a novel mutation in exon 9 of the glucocerebrosidase gene of a patient with Gaucher disease and of Sardinian origin. 相似文献
9.
Pornanong Aramwit Qiuran Jiang Supritha Muppuri Narendra Reddy 《Biotechnology and bioengineering》2023,120(10):2827-2839
Transgenic modification of Bombyx mori silkworms is a benign approach for the production of silk fibers with extraordinary properties and also to generate therapeutic proteins and other biomolecules for various applications. Silk fibers with fluorescence lasting more than a year, natural protein fibers with strength and toughness exceeding that of spider silk, proteins and therapeutic biomolecules with exceptional properties have been developed using transgenic technology. The transgenic modifications have been done primarily by modifying the silk sericin and fibroin genes and also the silk producing glands. Although the genetic modifications were typically performed using the sericin 1 and other genes, newer techniques such as CRISPR/Cas9 have enabled successful modifications of both the fibroin H-chain and L-chain. Such modifications have led to the production of therapeutic proteins and other biomolecules in reasonable quantities at affordable costs for tissue engineering and other medical applications. Transgenically modified silkworms also have distinct and long-lasting fluorescence useful for bioimaging applications. This review presents an overview of the transgenic techniques for modifications of B. mori silkworms and the properties obtained due to such modifications with particular focus on production of growth factors, fluorescent proteins, and high performance protein fibers. 相似文献
10.
Narendra Tuteja Ning Wu Huang Doris Skopac Renu Tuteja Sara Hrvatic Jianwen Zhang Sandor Pongor Grard Joseph Christian Faucher Franois Amalric Arturo Falaschi 《Gene》1995,160(2):143-148
The cDNA encoding human DNA helicase IV (HDH IV), a 100-kDa protein which unwinds DNA in the 5′ to 3′ direction with respect to the bound strand, was cloned and sequenced. It was found to be identical to the human cDNA encoding nucleolin, a ubiquitous eukaryotic protein essential for pre-ribosome assembly. HDH IV/nucleolin can unwind RNA-RNA duplexes, as well as DNA-DNA and DNA-RNA duplexes. Phosphorylation of HDH IV/nucleolin by cdc2 kinase and casein kinase II enhanced its unwinding activity in an additive way. The Gly-rich C-terminal domain possesses a limited ATP-dependent duplex-unwinding activity which contributes to the helicase activity of HDH IV/nucleolin. 相似文献