全文获取类型
收费全文 | 1707篇 |
免费 | 125篇 |
国内免费 | 40篇 |
出版年
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 37篇 |
2020年 | 12篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 29篇 |
2016年 | 46篇 |
2015年 | 104篇 |
2014年 | 102篇 |
2013年 | 128篇 |
2012年 | 174篇 |
2011年 | 131篇 |
2010年 | 85篇 |
2009年 | 80篇 |
2008年 | 115篇 |
2007年 | 110篇 |
2006年 | 90篇 |
2005年 | 88篇 |
2004年 | 78篇 |
2003年 | 70篇 |
2002年 | 76篇 |
2001年 | 32篇 |
2000年 | 19篇 |
1999年 | 25篇 |
1998年 | 19篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 15篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1962年 | 2篇 |
排序方式: 共有1872条查询结果,搜索用时 312 毫秒
111.
Eliane Berrou Alexandre Kauskot Frédéric Adam Amélie Harel Paulette Legendre Cécile Lavenu Bombled Chantal Rothschild Nicolas Prevost Olivier D. Christophe Peter J. Lenting Cécile V. Denis Jean-Philippe Rosa Marijke Bryckaert 《PloS one》2015,10(12)
Thrombocytopenia and increased platelet clearance observed in von Willebrand disease-type 2B (VWD-2B) may be explained by platelet apoptosis triggered by the constitutive binding of VWF to its receptor, glycoprotein Ib (GPIb). Apoptosis was assessed in platelets from two patients with a severe VWD-2B mutation VWF/p.V1316M and from mice transiently expressing VWF/p.V1316M. We now report that the VWD-2B mutation VWF/p.V1316M which binds spontaneously to its receptor GPIbα does not induce apoptosis. In 2 unrelated patients (P1 and P2) exhibiting different VWF plasma levels (70% and 36%, respectively, compared with normal pooled human plasma given as 100%), inner transmembrane depolarization of mitochondria, characteristic of apoptotic events was undetectable in platelets, whether washed or in whole blood. No or a moderate phosphatidyl serine (PS) exposure as measured by annexin-V staining was observed for P1 and P2, respectively. Expression of pro-apoptotic proteins Bak and Bax, and caspase-3 activity were similar to control platelets. In the VWD-2B mouse model expressing high levels of mVWF/p.V1316M (423%), similar to what is found in inflammatory pathologies, no significant difference was observed between mice expressing mVWF/WT and mVWF/p.V1316M. These results strongly argue against apoptosis as a mechanism for the thrombocytopenia of severe VWD-2B exhibiting the VWF/p.V1316M mutation. 相似文献
112.
113.
选择阴石粉背蕨(Aleuritopteris humatifolia)和金粉背蕨(A.chrysophylla)及其相关类群共27种植物,提取基因组DNA,通过聚合酶链式反应(PCR)扩增其叶绿体rbc L,trn L-F和mat K序列,所得序列利用Clustal X软件进行对位排列,用MEGA6.0软件计算种内及种间遗传距离,并采用最大简约法(MP)构建系统发育树。结果显示:阴石粉背蕨1个样品和金粉背蕨2个样品的rbc L,trn L-F和mat K序列间差异很小,最大遗传距离均小于其与其它近缘种的种间最小遗传距离,结合两个种叶片形态、孢子、囊群盖和根状茎鳞片等形态学特征的对比研究,作者认为阴石粉背蕨应该作为金粉背蕨的异名处理。 相似文献
114.
115.
Christine Demanche Manjula Deville Johan Michaux Véronique Barriel Claire Pin?on Cécile Marie Aliouat-Denis Muriel Pottier Christophe No?l Eric Viscogliosi El Moukhtar Aliouat Eduardo Dei-Cas Serge Morand Jacques Guillot 《PloS one》2015,10(4)
Pneumocystis fungi represent a highly diversified biological group with numerous species, which display a strong host-specificity suggesting a long co-speciation process. In the present study, the presence and genetic diversity of Pneumocystis organisms was investigated in 203 lung samples from woodmice (Apodemus sylvaticus) collected on western continental Europe and Mediterranean islands. The presence of Pneumocystis DNA was assessed by nested PCR at both large and small mitochondrial subunit (mtLSU and mtSSU) rRNA loci. Direct sequencing of nested PCR products demonstrated a very high variability among woodmouse-derived Pneumocystis organisms with a total number of 30 distinct combined mtLSU and mtSSU sequence types. However, the genetic divergence among these sequence types was very low (up to 3.87%) and the presence of several Pneumocystis species within Apodemus sylvaticus was considered unlikely. The analysis of the genetic structure of woodmouse-derived Pneumocystis revealed two distinct groups. The first one comprised Pneumocystis from woodmice collected in continental Spain, France and Balearic islands. The second one included Pneumocystis from woodmice collected in continental Italy, Corsica and Sicily. These two genetic groups were in accordance with the two lineages currently described within the host species Apodemus sylvaticus. Pneumocystis organisms are emerging as powerful tools for phylogeographic studies in mammals. 相似文献
116.
Pin Guo Jin Lan Jianwei Ge Quanmin Nie Liemei Guo Yongming Qiu Qing Mao 《Experimental cell research》2014
Glioblastoma multiforme (GBM) is notoriously resistant to radiation, and consequently, new radiosensitizers are urgently needed. MicroRNAs are a class of endogenous gene modulators with emerging roles in DNA repair. We found that overexpression of miR-26a can enhance radiosensitivity and reduce the DNA repair ability of U87 cells. However, knockdown miR-26a in U87 cells could act the converse manner. Mechanistically, this effect is mediated by direct targeting of miR-26a to the 3′UTR of ATM, which leads to reduced ATM levels and consequent inhibition of the homologous recombination repair pathway. These results suggest that miR-26a may act as a new radiosensitizer of GBM. 相似文献
117.
Mathieu Muller Dominique Patureau Jean-Jacques Godon Jean-Philippe Delgenès Guillermina Hernandez-Raquet 《Applied microbiology and biotechnology》2010,85(3):691-701
The biodegradation of estradiol (E2), estrone (E1), and ethinylestradiol (EE2) was investigated using mixed bacterial cultures
enriched from activated sludge. Enrichments were carried out on E2 or EE2 in batch conditions with acetonitrile as additional
carbon source. Degradation experiments were performed both using hormones as sole carbon source or with an additional source.
The hormones were completely degraded by these cultures. Estradiol was rapidly converted to E1 within 24 h. Thereafter, E1
degradation began, displaying a lag phase ranging from 3 to 4 days. Estrone depletion took from 48 h to more than 6 days,
depending on the culture conditions. For EE2 degradation, when it was the sole carbon source, the lag phase and the time required
for its complete removal (7 and 15 days, respectively) were shorter that in cultures with a supplementary carbon source. The
specific degradation rates observed for E2 both with and without an additional carbon source were similar. By contrast, the
specific degradation rates for E1 and EE2 were, respectively, seven and 20 times faster when these hormones were supplied
as the sole carbon source. The bacterial community structure of each culture was characterized by molecular and cultural methods.
The mixed cultures were made up of species belonging to Alcaligenes faecalis, Pusillimonas sp., Denitrobacter sp., and Brevundimonas diminuta or related to uncultured Bacteroidetes. The isolated strain B. diminuta achieved the conversion of E2 to E1. 相似文献
118.
Denis Monneret Jean-Louis Pepin Diane Godin-Ribuot Veronique Ducros Jean-Philippe Baguet Patrick Levy Patrice Faure 《Free radical biology & medicine》2010,48(4):619-625
Obstructive sleep apnea (OSA) is characterized by recurrent apnea during sleep that may unbalance oxidative stress, increasing atherosclerosis. Among oxidative stress markers, 15-F2t-isoprostane is considered one of the most sensitive and specific metabolites of lipid peroxidation. To explore the relationship between urinary 15-F2t-isoprostane with sleep apnea severity and carotid modifications in nonobese OSA patients, 31 nonobese sleep apnea patients were studied, along with 10 lean subjects without OSA. Patients were assessed by polysomnography, blood pressure measurement, and ultrasonography to determine the carotid intima–media thickness (IMT). Urinary 15-F2t-isoprostanes were measured by liquid chromatography–tandem mass spectrometry. Urinary 15-F2t-isoprostane concentrations were increased in severe OSA patients compared to control subjects (20.2 ± 7.3 vs 12.3 ± 2.8 ng/mmol creatinine; P = 0.020). Mean carotid IMT was correlated with 15-F2t-isoprostane (r = 0.532; P < 0.001) and with the apnea–hypopnea index (r = 0.345; P = 0.029). 15-F2t-Isoprostane level was related to the night time spent at SaO2 < 90% (r = 0.478; P = 0.002), the apnea–hypopnea index (r = 0.465; P = 0.003), and the mean nocturnal SaO2 (r = ? 0.424; P = 0.007). These results showed a relationship between lipid peroxidation, carotid intima–media thickness, and intermittent hypoxia in nonobese OSA patients, thus reinforcing the hypothesis that oxidative stress could be involved in the early atherosclerotic process. 相似文献
119.
Navjot S. Sodhi Mary Rose C. Posa Tien Ming Lee David Bickford Lian Pin Koh Barry W. Brook 《Biodiversity and Conservation》2010,19(2):317-328
Southeast Asia is a region of conservation concern due to heavy losses of its native habitats. In this overview, we highlight
the conservation importance of Southeast Asia by comparing its degree of species endemism and endangerment, and its rate of
deforestation with other tropical regions (i.e., Meso-America, South America, and Sub-Saharan Africa). Southeast Asia contains
the highest mean proportion of country-endemic bird (9%) and mammal species (11%). This region also has the highest proportion
of threatened vascular plant, reptile, bird, and mammal species. Furthermore, not only is Southeast Asia’s annual deforestation
rate the highest in the tropics, but it has also increased between the periods 1990–2000 and 2000–2005. This could result
in projected losses of 13–85% of biodiversity in the region by 2100. Secondary habitat restoration, at least in certain countries,
would allow for some amelioration of biodiversity loss and thus potentially lower the currently predicted extinction rates.
Nonetheless, urgent conservation actions are needed. Conservation initiatives should include public education, sustaining
livelihoods, and ways to enhance the sustainability of agriculture and increase the capacity of conservation institutions.
Furthermore, these actions should be country-specific and not ignore areas heavily populated by humans, as they can also harbour
high numbers of threatened species. We urge that cooperative conservation initiatives be undertaken and support (e.g., capacity-building)
be given by more developed countries in the region and beyond. 相似文献
120.