全文获取类型
收费全文 | 136篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
丛书文集 | 2篇 |
理论与方法论 | 1篇 |
现状及发展 | 43篇 |
研究方法 | 3篇 |
综合类 | 86篇 |
自然研究 | 2篇 |
出版年
2022年 | 1篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2012年 | 1篇 |
2011年 | 6篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1971年 | 7篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 7篇 |
1967年 | 7篇 |
1966年 | 2篇 |
1962年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有137条查询结果,搜索用时 31 毫秒
101.
The tetradecapeptide bombesin was originally isolated from frog skin. Bombesin-like peptides have since been detected in mammalian gastrointestinal tract, brain and lung. These peptides have potent pharmacological effects on the central nervous system; they cause contraction of intestinal, uterine and urinary tract smooth muscle; and stimulate the release of other peptides including gastrin, cholecystokinin, motilin, pancreatic polypeptide, neurotensin, insulin, enteroglucagon, prolactin and growth hormone. Specific plasma membrane receptors for bombesin have been demonstrated on pancreatic acinar cells, brain membranes and pituitary cells. Studies defining the physiological importance of bombesin have been impeded by the lack of a bombesin receptor antagonist. Here we describe experiments which demonstrate that a peptide originally described as a substance P receptor antagonist, [D-Arg, D-Pro, D-Trp, Leu ]substance P, is also a bombesin receptor antagonist. This peptide competitively inhibits the ability of bombesin to stimulate enzyme secretion from dispersed pancreatic acini, and also inhibits the action of other peptides that interact with the bombesin receptor. 相似文献
102.
Everette S. Gardner 《Journal of forecasting》1983,2(1):1-21
This paper evaluates a variety of automatic monitoring schemes to detect biased forecast errors. Backward cumulative sum (cusum) tracking signals have been recommended in previous research to monitor exponential smoothing models. This research shows that identical performance can be had with much simpler tracking signals. The smoothed-error signal is recommended for α = 0.1, although its performance deteriorates badly as α is increased. For higher α values, the simple cusum signal is recommended. A tracking signal based on the autocorrelation in errors is recommended for forecasting models other than exponential smoothing, with one exception. If the time series has a constant variance, the backward cusum should give better results. 相似文献
103.
Isolation of a feline leukaemia provirus containing the oncogene myc from a feline lymphosarcoma 总被引:1,自引:0,他引:1
The molecular mechanism by which feline leukaemia virus (FeLV) induces lymphoid malignancy in domestic cats is largely unknown. Using the insertional activation model of c-myc by avian leukosis virus in the induction of bursal lymphoma in chickens, we have now characterized the c-myc locus in feline tissues and investigated the possibility that FeLV may also insert within feline c-myc. We used the 1.5 kilobase (kb) PstI fragment of MC29 v-myc in Southern blot analysis to characterize the structure of the c-myc locus in the DNA of 31 naturally occurring feline lymphomas. Analysis of a cloned c-myc gene from one lymphoma demonstrated that sequences homologous to v-myc occupy 2.6 kb of feline DNA in which a putative intron of 0.5 kb separates sequences homologous to the 5' and 3' exons represented in avian v-myc. We also observed in the DNA of this lymphoma tumour-specific fragments homologous to v-myc. Characterization of these molecularly cloned myc-hybridizing fragments revealed the presence of at least two identical FeLV proviruses 5.5 kb in length, each containing long terminal repeats enclosing a spliced version of the feline myc gene. 相似文献
104.
105.
106.
107.
108.
Karhadkar SS Bova GS Abdallah N Dhara S Gardner D Maitra A Isaacs JT Berman DM Beachy PA 《Nature》2004,431(7009):707-712
Metastatic cancers adopt certain properties of normal cells in developing or regenerating organs, such as the ability to proliferate and alter tissue organization. We find here that activity of the Hedgehog (Hh) signalling pathway, which has essential roles in developmental patterning, is required for regeneration of prostate epithelium, and that continuous pathway activation transforms prostate progenitor cells and renders them tumorigenic. Elevated pathway activity furthermore distinguishes metastatic from localized prostate cancer, and pathway manipulation can modulate invasiveness and metastasis. Pathway activity is triggered in response to endogenous expression of Hh ligands, and is dependent upon the expression of Smoothened, an essential Hh response component that is not expressed in benign prostate epithelial cells. Monitoring and manipulating Hh pathway activity may thus offer significant improvements in diagnosis and treatment of prostate cancers with metastatic potential. 相似文献
109.
教学型大学的主要任务是提高教学质量,培养应用型高级专门人才.学科建设是人才培养的关键.重点学科建设应结合学科特点和优势,明确学科研究方向,紧密结合教学,突出应用性教育的特点,发挥重点学科的科学研究、人才培养、为社会服务三大职能.就材料物理与化学学科建设提出了自己的初步思考. 相似文献
110.
Résumé La forme d'hypertension qui accompagne la régénération de la glande surrénale énucléée à été étudiée chez les rats. Au cours de l'évolution de l'hypertension, la réaction vasculaire à la noradrénaline, l'adrénaline, la vasopressine et l'ocitocine est modifiée de manière qualitative, mais les effets vasculaires de l'hypertensine et de l'acétylcholine restent inchangés. Ces modifications diffèrent selon la phase de développement de l'hypertension. Hormis la vasopressine, les agents hypertenseurs ne sont pas plus actifs. Ces changements reflètent en toute probabilité le déséquilibre hormonal lié à ce type d'hypertension.
Supported by a grant from the National Institutes of Health, Washington. 相似文献
Supported by a grant from the National Institutes of Health, Washington. 相似文献