全文获取类型
收费全文 | 372篇 |
免费 | 35篇 |
国内免费 | 3篇 |
专业分类
410篇 |
出版年
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 17篇 |
2011年 | 20篇 |
2010年 | 23篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 29篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1968年 | 2篇 |
1908年 | 1篇 |
1904年 | 2篇 |
1903年 | 1篇 |
排序方式: 共有410条查询结果,搜索用时 15 毫秒
1.
2.
Some recent advances in the chemistry and biology of transforming growth factor-beta 总被引:104,自引:17,他引:87 下载免费PDF全文
M B Sporn A B Roberts L M Wakefield B de Crombrugghe 《The Journal of cell biology》1987,105(3):1039-1045
3.
Pneumocystis carinii is the prime opportunistic pathogen of our time, the leading cause of fatal pneumonia in the increasing number of immunosuppressed subjects encountered on oncology and transplant programmes' and in subjects with the acquired immuno-deficiency syndrome (AIDS). 相似文献
4.
5.
Ann E. Wakefield Sarah E. Peters Suneale Banerji Paul D. Bridge Geoffrey S. Hall David L. Hawksworth Lynden A. Guiver rew G. Allen Julian M. Hopkin 《Molecular microbiology》1992,6(14):1903-1911
Pneumocystis carinii causes life-threatening pneumonia in T-lymphocyte-immunodeficient subjects in transplant and oncology units or with acquired immune deficiency syndrome (AIDS). Recent DNA homology studies show P. carinii to be a fungus. To investigate the biology and epidemiology of this parasite further, we elected to determine for it a more precise taxonomic assignment within the fungal kingdom. We screened a wide range of organisms representing the major orders of fungi using DNA amplification and subsequently sequenced a portion of the mitochondrial gene encoding the large subunit ribosomal RNA. Our data show that the opportunistic pulmonary pathogen P. carinii is closely related to the ustomycetous red yeast fungi, a group which includes organisms that are extensively distributed throughout the environment and which release many widely dispersed airborne spores. 相似文献
6.
Transforming growth factor beta is an important immunomodulatory protein for human B lymphocytes 总被引:82,自引:0,他引:82
J H Kehrl A B Roberts L M Wakefield S Jakowlew M B Sporn A S Fauci 《Journal of immunology (Baltimore, Md. : 1950)》1986,137(12):3855-3860
The growth and differentiation of B cells to immunoglobulin (Ig)-secreting cells is regulated by a variety of soluble factors. This study presents data that support a role for transforming growth factor (TGF)-beta in this regulatory process. B lymphocytes were shown to have high-affinity receptors for TGF-beta that were increased fivefold to sixfold after in vitro activation. The addition of picogram quantities of TGF-beta to B cell cultures suppressed factor-dependent, interleukin 2 (IL 2) B cell proliferation and markedly suppressed factor-dependent (IL 2 or B cell differentiation factor) B cell Ig secretion. In contrast, the constitutive IgG production by an Epstein Barr virus-transformed B cell line was not modified by the presence of TGF-beta in culture. This cell line was found to lack high-affinity TGF-beta receptors. The degree of inhibition of B cell proliferation observed in in vitro cultures was found to be dependent not only on the concentration of TGF-beta added but also on the concentration of the growth stimulatory substance (IL 2) present. By increasing the IL 2 concentrations in culture, the inhibition of proliferation induced by TGF-beta could be partially overcome. In contrast, the inhibition of Ig secretion induced by TGF-beta could not be overcome by a higher concentration of stimulatory factor, demonstrating that the suppression of B cell differentiation by TGF-beta is not due solely to its effects on proliferation. Furthermore, it was demonstrated that B lymphocytes secrete TGF-beta. Unactivated tonsillar B cells had detectable amounts of TGF-beta mRNA on Northern blot analysis, and B cell activation with Staphylococcus aureus Cowan (SAC) resulted in a twofold to threefold increase in TGF-beta mRNA. Supernatants conditioned by unactivated B cells had small amounts of TGF-beta, SAC activation of the B cells resulted in a sixfold to sevenfold increase in the amount of TGF-beta present in the supernatants. Thus, B lymphocytes synthesize and secrete TGF-beta and express receptors for TGF-beta. The addition of exogenous TGF-beta to cultures of stimulated B cells inhibits subsequent proliferation and Ig secretion. TGF-beta may function as an autocrine growth inhibitor that limits B lymphocyte proliferation and ultimate differentiation. 相似文献
7.
Computer-Assisted Image Analysis of Plant Growth, Thigmomorphogenesis, and Gravitropism 总被引:2,自引:0,他引:2 下载免费PDF全文
Mordecai J. Jaffe Andrew H. Wakefield Frank Telewski Edward Gulley Ronald Biro 《Plant physiology》1985,77(3):722-730
A nonintrusive auxonometric system, based on the DARWIN image processor (Telewski et al. 1983 Plant Physiol 72: 177-181), is described and demonstrated in the analysis of gravitropism and thigmomorphogenesis in corn seedlings (Zea mays). Using this system, growth and bending of regularly shaped plants or organs can be quickly and accurately measured without, in any way, interfering with the plant. Furthermore, the growth and bending curves are automatically plotted. Thigmomorphogenesis in the aerial part of corn seedlings involves growth promotion at a low force load and growth retardation at higher force loads. The time courses of the two kinds of response are somewhat different, with retardation occurring immeditely after mechanical perturbation and growth promotion taking somewhat longer to begin. Gravitropic experiments show that when dark-grown corn seedlings are placed on their side in the light, the resulting curvature is due to two consecutive morphological mechanisms. In the first instance, lasting for about 15 minutes, the elongation of the bottom edge of the plant accelerates, while the elongation of the top edge remains constant. After that, for the next 1.75 hours, the elongation of the top edge decelerates and stops while that of the bottom edge remains constant at the increased rate for most of the period. The measurements taken from both experiments at relatively high resolution (0.08-0.1 millimeter) show that the growth curves are not smooth but show many small irregularities which may or may not involve micronutations. 相似文献
8.
9.
10.
The cytohistologic and ultrastructural findings in a case of bilateral renal oncocytoma diagnosed by needle aspiration cytology are presented. This case appears to be the first reported example in which the preoperative needle aspiration cytologic diagnosis of bilateral renal oncocytoma was made due to the presence of characteristic tumor cells that were seen singly or in small clusters with rounded polygonal shapes and abundant eosinophilic granular cytoplasm. The preoperative diagnosis of bilateral oncocytoma permitted a timely decision as to the appropriate management in this case. 相似文献