全文获取类型
收费全文 | 203篇 |
免费 | 41篇 |
专业分类
244篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2019年 | 1篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 18篇 |
2011年 | 13篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 12篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 5篇 |
2002年 | 20篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有244条查询结果,搜索用时 9 毫秒
61.
The X box in the DRA promoter of the human histocompatibility complex is required for expression of the DRA gene in B cells. We show that a B-cell factor binds to a sequence that is clearly distinguishable from binding sites for the previously described X box binding nuclear proteins RF-X, NF-X, NF-Xc, NF-S, hXBP, and AP-1. Mutations in the DRA X box that disrupt the binding of this factor result in a lower level of gene expression, as does the presence of Id (a trans-dominant regulatory protein that negatively regulates helix-loop-helix proteins). Furthermore, this factor is recognized by antibodies directed against the helix-loop-helix protein A1, a mouse homolog of the immunoglobulin enhancer binding proteins E12/E47, and it binds to sequences in other genes that were previously shown to bind these proteins. By these criteria, this factor is BCF-1. 相似文献
62.
63.
E Ricciardi G Di Martino P Maniglio M Schimberni A Frega M Jakimovska B Kobal M Moscarini 《World journal of surgical oncology》2012,10(1):149
ABSTRACT: Late rupture of external iliac artery pseudo-aneurysm is an uncommon complication in patients who undergo extensive gynecologic radical surgeries. A 28-year-old woman with stage IB cervical cancer underwent pelvic lymphadenectomy and extrafascial trachelectomy. Two months after surgery, massive bleeding from ruptured pseudo-aneurysm of the external iliac artery occurred. Endovascular management with covered stent placement was feasible and safe to stop bleeding. 相似文献
64.
65.
Oliver T. Fackler Paola d''Aloja Andreas S. Baur Maurizio Federico B. Matija Peterlin 《Journal of virology》2001,75(14):6601-6608
Human immunodeficiency virus type 1(F12) (HIV-1(F12)) interferes with the replication of other strains of HIV. Its accessory protein, Nef, is sufficient for this phenotype, where the production and infectivity of HIV are impaired significantly. The analysis of three rare mutations in this Nef protein revealed that these effects could be separated genetically. Moreover, the defect in virus production correlated with the lack of processing of the p55(Gag) precursor in the presence of Nef from HIV-1(F12). Importantly, the introduction of one of these mutations (E177G) into Nef from HIV-1(NL4-3) also created a dominant-negative Nef protein. Effects of Nef from HIV-1(F12) on virus production and Gag processing correlated with its altered subcellular distribution. Moreover, the association with two new cellular proteins with molecular masses of 74 and 75 kDa, which do not interact with other Nef proteins, correlated with the decreased virion infectivity. The identification of a dominant-negative protein for the production and infectivity of HIV suggests that Nef plays an active role at this stage of the viral replicative cycle. 相似文献
66.
Tatjana Ćosić Branka Vinterhalter Dragan Vinterhalter Nevena Mitić Aleksandar Cingel Jelena Savić Borut Bohanec Slavica Ninković 《In vitro cellular & developmental biology. Plant》2013,49(3):294-303
A simple and efficient protocol for direct somatic embryogenesis and plant regeneration of kohlrabi (Brassica oleracea var. gongylodes) was developed. Somatic embryos were induced from immature zygotic embryos at different developmental stages cultured on Murashige and Skoog medium supplemented with 0, 0.5, 1.0, or 1.5 mg/l 2,4-dichlorophenoxyacetic acid. Zygotic embryos at the early cotyledonary stage, which were cultured for 4 wk on plant growth regulator-free (PGR-free) medium, displayed the highest percentage of somatic embryogenesis (80.7%). Embryogenic tissue could be subcultured on the same medium for over 1 yr. Embryogenic lines derived from early cotyledonary stage zygotic embryos displayed the highest intensity of secondary embryogenesis (highest mean number of new somatic embryos per responsive somatic embryo explant). Histological analyses confirmed the direct origin of the secondary somatic embryos. Prolonged culturing of embryogenic tissue on PGR-free medium led to somatic embryo development into plantlets that were successfully acclimated in the greenhouse with a survival rate of 72.5%. Flow cytometry analysis showed no ploidy variation in 96.7% of the acclimated plants. 相似文献
67.
Krystyna?MusialEmail author Borut?Bohanec Marijana?Jak?e Leslaw?Przywara 《In vitro cellular & developmental biology. Plant》2005,41(4):446-452
Summary The development of embryo sacs (ES) in vitro and induction of gynogenesis were studied in onion flower bud culture. Explants were divided into three groups according
to their size at inoculation: (a) small flower buds (2.3–3.0 mm in diameter); (b) medium flower buds (3.1–3.7 mm); and (c)
large flower buds (3.8–4.4 mm). For histological study, excised ovaries were fixed at inoculation and then at 3-d intervals
until day 12, and after 2 and 3 wk of culture. Some explants were cultured until embryo emergence, i.e., 3–5 mo. In total,
2592 ovules were examined histologically. At inoculation, 83% of ovules in small flower buds contained a megaspore mother
cell; in 17% of ovules, two-nucleate ES occurred. In medium flower buds two-nucleate, four-nucleate, and mature ES were present
at frequencies of 15%, 46%, and 40%, respectively. In large flower buds, only mature ES occurred. In vitro conditions did not disturb meiosis and megagametophyte development in non-degenerated ovules. Regardless of the developmental
stage at inoculation, only mature ES occurred on day 12. Gynogenic embryos were found after 2 wk of culture, indicating that
embryos developed in mature ES exclusively. Embryos were detected in 5.4% of histological studied ovules; however, the number
of embryos after 3–5 mo. was higher (12.4%). The parthenogenetic origin of the embryos is discussed. In addition, ES containing
endosperm only (6.5%) and both endosperm and embryo (0.4%) were observed. 相似文献
68.
Deletions of two of four DAZ (Deleted in AZoospermia) gene copies located on the Y chromosome were associated with spermatogenic failure, but the information on DAZ copy number is still very scarce. The aim of this study was to determine the frequency of partial DAZ gene deletions and to analyze the existence of duplications in general Slovenian and Bosnian population. To answer these questions, we used real time PCR. We analyzed 100 male samples from Slovenian and Bosnian general population. The incidence of two DAZ gene copies was 6% (3/50) in Slovenian population. The incidence of more than four DAZ genes was 2% (1/50) in Slovenian population and 8% (4/50) in Bosnian population. Observed differences have not reached statistical significance. In conclusion we demonstrate that DAZ genes are not only prone to deletions but also to duplication events. Further studies are needed to estimate the prevalence of these mutations and its' relevance to male infertility. 相似文献
69.
Barboric M Zhang F Besenicar M Plemenitas A Peterlin BM 《Journal of virology》2005,79(17):11135-11141
70.