全文获取类型
收费全文 | 5812篇 |
免费 | 451篇 |
国内免费 | 4篇 |
出版年
2023年 | 26篇 |
2022年 | 65篇 |
2021年 | 148篇 |
2020年 | 85篇 |
2019年 | 99篇 |
2018年 | 170篇 |
2017年 | 138篇 |
2016年 | 195篇 |
2015年 | 269篇 |
2014年 | 303篇 |
2013年 | 366篇 |
2012年 | 468篇 |
2011年 | 488篇 |
2010年 | 269篇 |
2009年 | 249篇 |
2008年 | 336篇 |
2007年 | 357篇 |
2006年 | 335篇 |
2005年 | 274篇 |
2004年 | 232篇 |
2003年 | 243篇 |
2002年 | 215篇 |
2001年 | 61篇 |
2000年 | 55篇 |
1999年 | 53篇 |
1998年 | 41篇 |
1997年 | 34篇 |
1996年 | 26篇 |
1995年 | 25篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 31篇 |
1991年 | 24篇 |
1990年 | 28篇 |
1989年 | 42篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 30篇 |
1985年 | 34篇 |
1984年 | 33篇 |
1983年 | 27篇 |
1982年 | 22篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 19篇 |
1977年 | 15篇 |
1976年 | 20篇 |
1975年 | 12篇 |
1974年 | 16篇 |
排序方式: 共有6267条查询结果,搜索用时 46 毫秒
1.
V A Frolov G Mall P Rieger Kh Derks Z Antoni 《Biulleten' eksperimental'no? biologii i meditsiny》1987,104(12):739-741
Intensive synthesis of collagen-like substance was revealed in the rabbit myocardium during experimental diphtheria intoxication. It was more marked in the right ventricle 24 hours after the injection of diphtheria toxin. Since similar changes (the substance was mainly formed around blood vessels) have been observed in other cases of toxic myocardial alterations (i.e. ethanol intoxication, injection of pharmacological agents, etc.), it can be assumed that it is a standard protective reaction of the altered heart to the penetration of toxic agents from the blood into the myocardial tissue. 相似文献
2.
3.
Experiments in mice have demonstrated that in the presence of influenza infection the suppressing effect of virulent shigellae on the secondary humoral and cell-mediated immune response is enhanced. Under such conditions avirulent shigellae can also show suppressing effect which is usually absent in these organisms. 相似文献
4.
A F Frolov V E Rychnev V M Frolov M A Bala 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(11):93-96
The dynamics of circulating immune complexes (CIC) in comparison with the level of SH-groups of serum deproteinate and other characteristics of cell-mediated and humoral immunity (the reaction of the inhibition of antibodies, the levels of T-cells and their main subpopulations) was studied in 103 erysipelas patients and in 46 persons having had the disease at the acute period of this infection and at the periods between relapses. The elevated levels of CIC and SH-groups of serum deproteinate were found to be directly correlated with the inhibition index. The study showed that, as a rule, in patients with the elevated level of CIC the frequently relapsing form of erysipelas, accompanied by the formation of relative hypersuppressor-type secondary immunodeficiency and by a decrease in the functional activity of dermal macrophages, was observed. 相似文献
5.
6.
7.
Shreaya Chakroborty Clark Briggs Megan B. Miller Ivan Goussakov Corinne Schneider Joyce Kim Jaime Wicks Jill C. Richardson Vincent Conklin Benjamin G. Cameransi Grace E. Stutzmann 《PloS one》2012,7(12)
Alzheimer’s disease (AD) is a devastating neurodegenerative condition with no known cure. While current therapies target late-stage amyloid formation and cholinergic tone, to date, these strategies have proven ineffective at preventing disease progression. The reasons for this may be varied, and could reflect late intervention, or, that earlier pathogenic mechanisms have been overlooked and permitted to accelerate the disease process. One such example would include synaptic pathology, the disease component strongly associated with cognitive impairment. Dysregulated Ca2+ homeostasis may be one of the critical factors driving synaptic dysfunction. One of the earliest pathophysiological indicators in mutant presenilin (PS) AD mice is increased intracellular Ca2+ signaling, predominantly through the ER-localized inositol triphosphate (IP3) and ryanodine receptors (RyR). In particular, the RyR-mediated Ca2+ upregulation within synaptic compartments is associated with altered synaptic homeostasis and network depression at early (presymptomatic) AD stages. Here, we offer an alternative approach to AD therapeutics by stabilizing early pathogenic mechanisms associated with synaptic abnormalities. We targeted the RyR as a means to prevent disease progression, and sub-chronically treated AD mouse models (4-weeks) with a novel formulation of the RyR inhibitor, dantrolene. Using 2-photon Ca2+ imaging and patch clamp recordings, we demonstrate that dantrolene treatment fully normalizes ER Ca2+ signaling within somatic and dendritic compartments in early and later-stage AD mice in hippocampal slices. Additionally, the elevated RyR2 levels in AD mice are restored to control levels with dantrolene treatment, as are synaptic transmission and synaptic plasticity. Aβ deposition within the cortex and hippocampus is also reduced in dantrolene-treated AD mice. In this study, we highlight the pivotal role of Ca2+ aberrations in AD, and propose a novel strategy to preserve synaptic function, and thereby cognitive function, in early AD patients. 相似文献
8.
We have observed that sperm quality parameters indicative of spermatozoa hyperactivation such are lower “linearity” and “straightness”, and as showed by this research “elongation”, were more pronounced in patients with normal spermiogram compared to the group of men with reduced sperm motility who were undergoing routine in vitro fertilisation. The research encompassed 97 men diagnosed with normozoospermia (n = 20), asthenozoospermia (n = 54) and oligoasthenozoospermia (n = 23). The findings indicate that sperm quality of patients with normal spermiogram diagnosed according to WHO criteria, may be compromised by showing premature spontaneous hyperactivation which can decrease the chances of natural conception. We assessed synergistic effects of multiple chemical elements in ejaculated semen to find if premature spontaneous hyperactivation of spermatozoa can be a sign of imbalanced semen composition especially of elements K, Ca, Cu and Zn. Human semen samples showing low or high baseline status of chemical elements concentrations were found in samples from all three diagnostic groups. However, correlation of K/Ca and Cu/Zn ratios, taking into account samples from all three groups of men, were negative at statistical significance level p = 0.01. We tested if the negative correlation between K/Ca and Cu/Zn ratio works for greater number of semen samples. We found the negative correlation to be valid for 175 semen samples at statistical significance of p = 0.00002. The ratio of K/Ca and Cu/Zn, i.e. increased concentrations of K and Zn in comparison to concentrations of Ca and Cu, were associated with a decrease of “straightness” in the group of men with normal spermiogram and pronounced spontaneous hyperactivation of spermatozoa, implying that these elements act in synergy and that the balance of elements and not their absolute concentrations plays the major role in premature spermatozoa hyperactivation in ejaculated semen. 相似文献
9.
10.