全文获取类型
收费全文 | 7434篇 |
免费 | 750篇 |
国内免费 | 1篇 |
出版年
2022年 | 50篇 |
2021年 | 91篇 |
2020年 | 87篇 |
2019年 | 80篇 |
2018年 | 117篇 |
2017年 | 89篇 |
2016年 | 128篇 |
2015年 | 229篇 |
2014年 | 244篇 |
2013年 | 393篇 |
2012年 | 408篇 |
2011年 | 417篇 |
2010年 | 270篇 |
2009年 | 238篇 |
2008年 | 310篇 |
2007年 | 338篇 |
2006年 | 346篇 |
2005年 | 302篇 |
2004年 | 296篇 |
2003年 | 299篇 |
2002年 | 301篇 |
2001年 | 112篇 |
2000年 | 115篇 |
1999年 | 135篇 |
1998年 | 107篇 |
1997年 | 73篇 |
1996年 | 81篇 |
1995年 | 86篇 |
1994年 | 76篇 |
1993年 | 76篇 |
1992年 | 98篇 |
1991年 | 81篇 |
1990年 | 99篇 |
1989年 | 85篇 |
1988年 | 82篇 |
1987年 | 82篇 |
1986年 | 84篇 |
1985年 | 103篇 |
1984年 | 100篇 |
1983年 | 70篇 |
1982年 | 92篇 |
1981年 | 74篇 |
1980年 | 83篇 |
1979年 | 73篇 |
1978年 | 80篇 |
1977年 | 65篇 |
1976年 | 59篇 |
1975年 | 58篇 |
1974年 | 54篇 |
1973年 | 59篇 |
排序方式: 共有8185条查询结果,搜索用时 15 毫秒
1.
The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments. 相似文献
2.
A physical domain of herpes simplex virus ICP8 is expressed and active in Escherichia coli.
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this report, we describe a series of procedures to assay the function of fusion genes in Escherichia coli and the specific application to the carboxy-terminal third of the herpes simplex virus type 1 (HSV-1) DNA-binding protein ICP8. E. coli cells containing the cloned HSV-1 BamHI G fragment with the HSV-1 BamHI-G-V site, map unit 0.388, nearest the tet promoter in pBR322 synthesized an active product containing a portion of ICP8. The new product induced phenotypic alterations in recipient hosts that were measurable and stable yet limited to the stability of the plasmid. The corresponding cloned DNA from the characterized HSV-1 DNA-binding protein mutant tsHA1 exhibited a predictable temperature-sensitive phenotype. Screening procedures based on the loss of induction of the parental plasmid-induced phenotype in E. coli cells allowed us to select additional mutations. One of these, which conferred a phenotype different from that of tsHA1, was transferred to the viral genome by marker transfer techniques. We suggest that any mutant could be isolated in any sequence, provided that the wild-type coding sequences induce alterations in E. coli cells. The observed alterations should have relevance in determining the mode of action of the protein in its normal environment. 相似文献
3.
Immune deficiency in the X-linked lymphoproliferative syndrome. I. Epstein-Barr virus-specific defects 总被引:8,自引:0,他引:8
S Harada K Sakamoto J K Seeley T Lindsten T Bechtold J Yetz G Rogers G Pearson D T Purtilo 《Journal of immunology (Baltimore, Md. : 1950)》1982,129(6):2532-2535
Eleven males with XLP were evaluated for EBV-specific antibodies during periods of 2 to 7 yr. Variable responses to EBV-specific antigens were found. All 11 patients had subnormal anti-EBNA titers, which probably reflected a T cell deficiency. The patients showed four different patterns in their anti-VCA response: 1) two boys who had experienced malignant lymphoma mounted no antibodies at all; 2) two patients showed intermittent anti-VCA titers; 3) four males had persistently elevated anti-VCA titers; and 4) three patients showed normal anti-VCA titers. ADCC against EBV-infected cells was abnormally low in six patients and was elevated in two patients given gamma-globulin. ADCC titers did not correlate with anti-VCA titers. However, most patients with XLP failed to effect regression of autologous EBV-infected lymphoblastoid cell lines, indicating a deficiency in long-lived T cell-mediated immunity to EBV. 相似文献
4.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
5.
Transformation in vitro of bone marrow cells by avian erythroblastosis virus (AEV) gives rise to rapidly growing cells of erythroid nature. Target cells of neoplastic transformation by AEV are recruited among the early progenitors of the erythroid lineage, the burst-forming units-erythroid (BFU-E). They express a brain-related antigen at a high level and an immature antigen at a low level. We show that AEV-transformed cells express low levels of the brain antigen and high levels of the immature antigen. Their response to specific factors regulating the erythroid differentiation indicates that they are very sensitive to erythropoietin. Furthermore, cells transformed by a temperature-sensitive mutant of AEV differentiate into hemoglobin-synthesizing cells 4 days after being shifted to the nonpermissive temperature. All these properties are similar to those of late progenitors of the erythroid lineage, the colony-forming units-erythroid (CFU-E). These results indicate that the AEV-transformed cells are blocked in their differentiation at the CFU-E stage. 相似文献
6.
7.
Feral and laboratory flocks of rock doves () show a pattern of grouped sequential exploitation when simultaneously presented with two dispersed, depleting patches of seed. This behavior contrasts with the ideal free distribution pattern shown when patches are small and concentrated. Grouped sequential exploitation consists of two phases: all pigeons first land together and feed at one patch, then leave one by one for the other patch. Departure times of individuals for the second patch are correlated with feeding rate at patch 1, which is in turn correlated with position in the dominance hierarchy. The decision to switch from patch 1 to patch 2 improves individual feeding rates in all cases, but is done slightly later than it should according to optimal foraging theory. 相似文献
8.
9.
10.
Nathalie Jeanray Rapha?l Marée Benoist Pruvot Olivier Stern Pierre Geurts Louis Wehenkel Marc Muller 《PloS one》2015,10(1)
Zebrafish is increasingly used to assess biological properties of chemical substances and thus is becoming a specific tool for toxicological and pharmacological studies. The effects of chemical substances on embryo survival and development are generally evaluated manually through microscopic observation by an expert and documented by several typical photographs. Here, we present a methodology to automatically classify brightfield images of wildtype zebrafish embryos according to their defects by using an image analysis approach based on supervised machine learning. We show that, compared to manual classification, automatic classification results in 90 to 100% agreement with consensus voting of biological experts in nine out of eleven considered defects in 3 days old zebrafish larvae. Automation of the analysis and classification of zebrafish embryo pictures reduces the workload and time required for the biological expert and increases the reproducibility and objectivity of this classification. 相似文献