全文获取类型
收费全文 | 297篇 |
免费 | 17篇 |
国内免费 | 43篇 |
专业分类
357篇 |
出版年
2024年 | 3篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 16篇 |
2013年 | 18篇 |
2012年 | 15篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 15篇 |
2007年 | 14篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1951年 | 2篇 |
1948年 | 1篇 |
1945年 | 1篇 |
1933年 | 1篇 |
1928年 | 1篇 |
1921年 | 1篇 |
1919年 | 2篇 |
1917年 | 1篇 |
排序方式: 共有357条查询结果,搜索用时 15 毫秒
1.
J.N. Beresford J.A. Gallagher M. Gowen M. Couch J. Poser D.D. Wood R.G.G. Russell 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,801(1):58-65
Cultural adherent human mononuclear cells produce factor(s) which stimulate the release of calcium from new-born mouse calvaria in organ culture. This stimulation of bone resorption is accompanied by an inhibition of the incorporation of [3H]proline into collagen which is independent of increased prostaglandin production by the bone. When human osteoblast-like cells are treated with conditioned medium from human mononuclear cells, collagen accounts for a decreased proportion of the protein synthesised. This effect on matrix synthesis is not accompanied by an inhibitory action of the monocyte-conditioned medium preparations on net cell proliferation. In human osteoblast-like cell cultures, partially purified human interleukin 1 also inhibits the production of the bone-specific protein osteocalcin in a dose-dependent fashion. These observations are consistent with the hypothesis that products of human monocytes similar to, or identical with, human interleukin 1 may be important regulators of bone metabolism and may contribute to the bone loss seen in diseases such as chronic rheumatoid arthritis. 相似文献
2.
P L Stern N Beresford C I Friedman V C Stevens J M Risk P M Johnson 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(4):1088-1091
Human placental villous trophoblast is known to be unreactive with W6/32 and other monoclonal antibodies recognizing monomorphic determinants of human class I MHC heavy chains, whereas extravillous cytotrophoblast in the placental bed is W6/32-reactive by immunohistology. We have now demonstrated, in contrast, that syncytiotrophoblast is the only cellular component of baboon early placental villous tissue which is reactive with any of these antibodies. Radioimmunoprecipitation of detergent-solubilized baboon placental membrane preparations, and subsequent SDS-PAGE, has shown the W6/32-reactive component to have an m.w. of 41,000 and to be associated with beta 2-microglobulin, whereas baboon peripheral lymphocytes express 45,000 m.w. W6/32-reactive antigens comparable with the HLA-A,B,C heavy chains of human lymphocytes. 相似文献
3.
Antithrombin Glasgow, 393 Arg to His: a P1 reactive site variant with increased heparin affinity but no thrombin inhibitory activity 总被引:1,自引:0,他引:1
Antithrombin Glasgow is a hereditary abnormal antithrombin that has lost thrombin inhibitory activity. It was isolated from the plasma of a 41-year-old male with a history of thrombotic events. Antithrombin Glasgow was purified from plasma using heparin-Sepharose chromatography at pH 7.4 eluting with increasing concentrations of NaCl. The normal protein eluted with 0.9 mol/l NaCl and Glasgow with 1.05 mol/l NaCl. Electrophoresis in agarose at pH 8.6 showed the variant to migrate more anodally than normal. The C-terminal small fragment resulting from catalytic cleavage with elastase between P3 and P4 of the reactive loop was isolated and sequenced. This showed the replacement of the arginine at residue 3 by a histidine. This is residue 393 in the intact molecule. The findings suggest that heparin, on binding, interacts indirectly with the reactive centre region of antithrombin. 相似文献
4.
R. W. Mayes N. A. Beresford B. J. Howard C. M. Vandecasteele G. Stakelum 《Radiation and environmental biophysics》1996,35(2):101-109
Limitations of existing methods to describe the bioavailability of dietary radionuclides to ruminants (the transfer coefficient
and apparent absorption coefficient) have led to the alternative suggestion of using the true absorption coefficient (A
t). Various approaches to estimatingA
t for radiocaesium, involving the intravenous administration of a second isotope, are presented and discussed with reference
to results from studies in which a range of radiocaesium sources were examined in sheep. Although estimates ofA
t differed between the sources, they were reasonably consistent between measurement techniques. Those methods which involved
the estimation of endogenous faecal excretion of radiocaesium could be used with previously contaminated animals and did not
require continuous administrations of radiocaesium isotopes, but gave unreliable results for sources of low bioavailability.
Methods based on estimating the turnover rate of dietary radiocaesium through blood plasma were sufficiently sensitive to
measureA
t for the range of sources studied. However, they require previously uncontaminated animals and continuous administration of
both isotopes for approximately 7 days. Bioavailability is more effectively measured asA
t than as the transfer or apparent absorption coefficients sinceA
t does not incorporate factors relating to the metabolism of radiocaesium in the tissues of the animal. The results of these
studies show that differences in transfer coefficients between sheep and cattle and between sheep of differing ages are not
due to variation in absorption across the gut. The potential for applying these approaches to other radioactive elements is
discussed. 相似文献
5.
6.
siRNA-directed inhibition of HIV-1 infection 总被引:133,自引:0,他引:133
Novina CD Murray MF Dykxhoorn DM Beresford PJ Riess J Lee SK Collman RG Lieberman J Shankar P Sharp PA 《Nature medicine》2002,8(7):681-686
RNA interference silences gene expression through short interfering 21 23-mer double-strand RNA segments that guide mRNA degradation in a sequence-specific fashion. Here we report that siRNAs inhibit virus production by targeting the mRNAs for either the HIV-1 cellular receptor CD4, the viral structural Gag protein or green fluorescence protein substituted for the Nef regulatory protein. siRNAs effectively inhibit pre- and/or post-integration infection events in the HIV-1 life cycle. Thus, siRNAs may have potential for therapeutic intervention in HIV-1 and other viral infections. 相似文献
7.
8.
大中型食肉动物肇事事件导致人类与野生动物关系恶化,给生物多样性保护工作带来巨大的挑战。若尔盖湿地是我国三大湿地之一,湿地、草原分布广泛,生物多样性丰富,畜牧业发达,但近年来狼(Canis lupus)捕杀牲畜的肇事事件时有发生。为了解若尔盖野生狼肇事件的空间分布以及牧民对人-狼冲突管理的看法,本研究于2022年对若尔盖县13个乡镇83个行政村进行走访调查。结果表明:(1)多数受访者(66.0%)认为在过去5年内,若尔盖县野生狼数量有所增加;(2)狼肇事事件具有明显的空间分异性,最严重的是包座乡。包座乡临近山区,该区域牧场面积广阔、牧民饲养牲畜数量多等原因导致该镇发生狼肇事事件较多;(3)对于狼肇事,绝大多数牧民(85.0%)更希望采取经济补偿或者驱赶措施,只有少数牧民(9.4%)希望采取捕杀的措施;(4)影响牧民对狼肇事管理措施的偏好因子中,受教育程度、年龄、民族以及被杀牲畜数量有显著影响。建议加强狼种群监测管理,采取措施减少狼捕杀牲畜,优化补偿机制,缓解当地牧民与狼之间的矛盾。本研究为当前若尔盖县野生动物保护和管理决策提供了依据,对其他地区大型食肉动物与当地居民冲突管理具有借鉴意义。 相似文献
9.
10.
David M. Wilson James Apps Nicholas Bailey Mark J. Bamford Isabel J. Beresford Michael A. Briggs Andrew R. Calver Barry Crook Robert P. Davis Susannah Davis David K. Dean Leanne Harris Tom D. Heightman Terry Panchal Christopher A. Parr Nigel Quashie Jon G.A. Steadman Joanne Schogger Andrew D. Medhurst 《Bioorganic & medicinal chemistry letters》2013,23(24):6897-6901
This Letter describes the discovery of a novel series of H3 receptor antagonists. The initial medicinal chemistry strategy focused on deconstructing and simplifying an early screening hit which rapidly led to the discovery of a novel series of H3 receptor antagonists based on the benzazepine core. Employing an H3 driven pharmacodynamic model, the series was then further optimised through to a lead compound that showed robust in vivo functional activity and possessed overall excellent developability properties. 相似文献