全文获取类型
收费全文 | 1376篇 |
免费 | 114篇 |
国内免费 | 1篇 |
专业分类
1491篇 |
出版年
2023年 | 15篇 |
2022年 | 28篇 |
2021年 | 29篇 |
2020年 | 17篇 |
2019年 | 22篇 |
2018年 | 38篇 |
2017年 | 40篇 |
2016年 | 50篇 |
2015年 | 68篇 |
2014年 | 66篇 |
2013年 | 77篇 |
2012年 | 112篇 |
2011年 | 88篇 |
2010年 | 73篇 |
2009年 | 53篇 |
2008年 | 83篇 |
2007年 | 69篇 |
2006年 | 66篇 |
2005年 | 35篇 |
2004年 | 43篇 |
2003年 | 34篇 |
2002年 | 36篇 |
2001年 | 16篇 |
2000年 | 36篇 |
1999年 | 24篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 8篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1971年 | 8篇 |
1969年 | 5篇 |
排序方式: 共有1491条查询结果,搜索用时 8 毫秒
11.
Etsuro Ito Kotaro Oka Carlos Collin Bernard G. Schreurs Manabu Sakakibara Daniel L. Alkon 《Journal of neurochemistry》1994,62(4):1337-1344
Abstract: Tumor necrosis factor-a (TNF-α), interferon-γ (IFN-7), and interleukin-6 (IL-6), but not TNF-β, can induce the in vitro differentiation of the neuroblastoma cell line N103 in a dose-dependent manner. Differentiation of N103 was accompanied by the arrest of cell growth and neurite formation. The induction of neuroblastoma cell differentiation by TNF-α and IFN-γ can be specifically inhibited by a nitric oxide (NO) synthase inhibitor, l -NG -monomethylarginine. In contrast, the differentiation of N103 cells by IL-6 was not affected by l -NG -monomethylarginine. These results indicate that TNF-α and IFN-γ, but not IL-6, induce the differentiation of neuroblastoma cells via NO. This is confirmed by the finding that the culture super- natants of N103 cells induced by TNF-α and IFN-γ, but not that by IL-6, contained high levels of NO2 − , the production of which was inhibited by l - N G -monomethylarginine. Furthermore, the differentiation of N103 cells can be induced directly in a dose-dependent manner by the addition of nitroprusside, a generator of NO, into the culture medium. These data therefore indicate that NO may be an important mediator in the induction of neuronal cell differentiation by certain cytokines such as TNF-α and IFN-γ and that neuronal cells, in addition to the macrophagelike brain cells, can be induced by immunological stimuli to produce large quantities of NO. 相似文献
12.
Two-microelectrode voltage-clamp measurements were made to determine the kinetics and voltage dependence of ionic currents across the soma membrane of the Hermissenda type B photoreceptor. The voltage-dependent outward potassium currents, IA and ICa(2+)-K+, the inward voltage-dependent calcium current, ICa2+ and the light-induced current, IIgt, were then described with Hodgkin-Huxley-type equations. The fast-activating and inactivating potassium current, IA, was described by the equation; IA(t) = gA(max)(ma infinity[1-exp(-t/tau ma)])3 x (ha infinity [1-exp(-t/tau ha)] + exp(-t/tau ha)) (Vm-EK), where the parameters ma infinity, ha infinity, tau ma, and tau ha are functions of membrane potential, Vm, and ma infinity and ha infinity are steady-state activation and inactivation parameters. Similarly, the calcium-dependent outward potassium current, ICa(2+)-K+, was described by the equation, ICa(2+)-K+ (t) = gc(max)(mc infinity(VC)(1-exp[-t/tau mc (VC)]))pc (hc infinity(VC) [1-exp(-t/tau hc)] + exp(-t/tau hc(VC)])pc(VC-EK). In high external potassium, ICa(2+)-K+ could be measured in approximate isolation from other currents as a voltage-dependent inward tail current following a depolarizing command pulse from a holding potential of -60 mV. A voltage-dependent inward calcium current across the type B soma membrane, ICa2+, activated rapidly, showed little inactivation, and was described by the equation: ICa2+ = gCa(max) [1 + exp](-Vm-5)/7]-1 (Vm-ECa), where gCa(max) was 0.5 microS. The light-induced current with both fast and slow phases was described by: IIgt(t) = IIgt1 + IIgt2 + IIgt3, IIgti = gIgti [1-exp(- ton/tau mi)] exp(-ton/tau hi)(Vm-EIgti) (i = 1, 2).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
13.
14.
15.
16.
Susceptibility of human immunodeficiency virus type 1 group O isolates to antiretroviral agents: in vitro phenotypic and genotypic analyses. 总被引:10,自引:4,他引:6 下载免费PDF全文
D Descamps G Collin F Letourneur C Apetrei F Damond I Loussert-Ajaka F Simon S Saragosti F Brun-Vzinet 《Journal of virology》1997,71(11):8893-8898
17.
Summary The presence of 1% agar in the fixation and substrate solutions for the histochemical demonstration of thiamine pyrophosphatase (4.4 mM TPP; 3.6 mM Pb2+; 0.025 Tris-maleate buffer, pH 7.2) clearly facilitates the localization of the enzyme in Golgi apparatus in cold microtome sections prepared from unfixed specimens. 相似文献
18.
Shaun P. Collin 《Zoomorphology》1981,98(3):227-231
Summary A previously undescribed receptor in the coxo-trochantinal region of the metathoracic leg of the cockroach Periplaneta americana was found to have central cell bodies. This cockroach stretch receptor is the second sensory receptor in insects reported to possess somata in the CNS and its remarkable similarity to a locust proprioceptor suggests it to be homologous. 相似文献
19.
The study of current flow fields in biologicaltissue requires finding the potential field from dipole sources such that the
normal gradient vanishes at the exterior surface. A convenient way to determine the dipole field is by taking the gradient
of the potential field set up by a point source. However, the point source problem is ill-posed when the normal gradient is
required to vanish at the outer surface. In the paper the nature of this problem is discussed and several methods for overcoming
the difficulty are presented. 相似文献