全文获取类型
收费全文 | 897篇 |
免费 | 66篇 |
国内免费 | 3篇 |
出版年
2024年 | 4篇 |
2023年 | 31篇 |
2022年 | 37篇 |
2021年 | 76篇 |
2020年 | 82篇 |
2019年 | 113篇 |
2018年 | 66篇 |
2017年 | 45篇 |
2016年 | 54篇 |
2015年 | 38篇 |
2014年 | 65篇 |
2013年 | 78篇 |
2012年 | 64篇 |
2011年 | 58篇 |
2010年 | 34篇 |
2009年 | 28篇 |
2008年 | 23篇 |
2007年 | 17篇 |
2006年 | 12篇 |
2005年 | 15篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有966条查询结果,搜索用时 31 毫秒
841.
842.
843.
Elmira Khansari Shahin Zarre Kamaleddin Alizadeh Farideh Attar Fatemeh Aghabeigi Yasaman Salmaki 《Flora》2012
Pollen grains of 47 taxa of Campanulaceae including 35 taxa of Campanula that represent its five subgenera and nine sections are investigated. Moreover, five species and three subspecies representing three sections in Asyneuma and one species of each genera Legousia, Michauxia, Zeugandra and Theodorovia were studied by light and scanning electron microscopy. The basic shape of the pollen grains was spheroidal. The apertures vary from tri- to hexa-porate. The sculpturing pattern of exine was rugulate-echinate, rugulate-microechinate or in few species rugulate-microreticulate and microechinate. The most valuable characters for subgeneric classification were the length and density of echini. The length of echini were significantly long (> 2 μm) in C. sclerotricha, Legousia falcata and Michauxia laevigata. Pollen grains show low variation in different species of subgen. Rapunculus, but were variable among different species of some groups, such as sect. Rupestres, probably indicating their non-monophyly despite homogeneity with respect to other morphological characters. Pollen morphology does not support recognition of Asyneuma, Legousia, Michauxia, Symphyandra, Theodorovia, and Zeugandra as separated from Campanula, since none of them exhibit any unique feature. 相似文献
844.
Mostafa-Gharehbaghi M Mostafa-Gharabaghi P Ghanbari F Abdolmohammad-Zadeh H Sadeghi GH Jouyban A 《Biological trace element research》2012,147(1-3):1-7
Bronchopulmonary dysplasia (BPD), also known as chronic lung disease, is one of the most challenging complications in premature newborn infants. Selenium plays a role in antioxidant system by protecting cell membranes and neutralizing the deleterious effects of free radicals. The aim of this study was to determine the relationship between selenium concentration and incidence of bronchopulmonary dysplasia using a validated analytical method. Umbilical cord blood and blood samples 30 days after the birth were collected from 38 preterm newborn infants with gestation age of 32 weeks or less, and the separated serums were kept at -70°C until analysis time. Selenium concentration of serum was determined using an atomic absorption spectrophotometer. The method was validated on the basis of standard validation techniques. The analytical method was linear in the range of 1 to 500 μg/L with the limit of detection of 0.4 μg/L. Samples were collected from 38 infants whose gestation age was 32 weeks or less. The blood samples were collected from the umbilical cord blood at birth in 19 cases. In 25 cases, blood samples were collected 1 month after birth. Of the 15 patients diagnosed with BPD, 10 were boys (p = 0.02). The mean serum selenium concentration was not different at birth between patients with and without BPD, but it was significantly lower at 30 days after birth in patients with BPD (38.5 ± 14.1vs. 45.4 ± 18.7 μg/L, p = 0.02). Preterm newborn infants with BPD had lower serum selenium concentrations 1 month after birth. 相似文献
845.
Nasibeh Khayer Sayed-Amir Marashi Mostafa Rezaei-Tavirani Fatemeh Goshadrou 《Expert review of proteomics》2019,16(2):161-169
Introduction: Identification of functionally-related genes is an important step in understanding biological systems. The most popular strategy to infer functional dependence is to study pairwise correlations between gene expression levels. However, certain functionally-related genes may have a low expression correlation due to their nonlinear interactions. The use of a three-way interaction (3WI) model with switching mechanism (SM) is a relatively new strategy to trace functionally-related genes. The 3WI model traces the dynamic and nonlinear nature of the co-expression relationship of two genes by introducing their link to the expression level of a third gene.
Areas covered: In this paper, we reviewed a variety of existing methods for tracing the 3WIs. Furthermore, we provide a comprehensive review of the previous biological studies based on 3WI models.
Expert commentary: Comparison of features of these methods indicates that the modified liquid association algorithm has the best efficiency for tracing 3WI between others. The limited number of biological studies based on the 3WI suggests that high computational demand of the available algorithms is a major challenge to apply this approach for analyzing high-throughput omics data. 相似文献
846.
Mohammad Fathalipour Masoomeh Eghtedari Fernanda Borges Tiago Silva Fatemeh Moosavi Omidreza Firuzi Hossein Mirkhani 《化学与生物多样性》2019,16(12)
The purpose of this study was to examine the neuroprotective effects of caffeic acid hexyl ( CAF6 ) and dodecyl ( CAF12 ) amide derivatives on the early stage of retinopathy in streptozotocin‐induced diabetic rats. Animals were divided in five groups (n=8/group); one group consisted of non‐diabetic rats as control, while the other four were diabetic animals either non‐treated or treated with CAF6 , CAF12 or resveratrol intravitreally for four weeks. Retinal superoxide dismutase (SOD) activity and 8‐iso‐prostaglandin F2α (iPF2α) levels were evaluated by an ELISA assay. Phosphorylation of ERK1/2 and AKT was determined by immunoblotting in retinal homogenates. Retinal morphology was also examined using light microscopy. Treatment with CAF6 and CAF12 increased retinal SOD activity, while it decreased iPF2α levels in diabetic rats. Phosphorylation of ERK1/2 was increased, while AKT phosphorylation was decreased in diabetic rats compared to normal control and these alterations were significantly reversed in diabetic rats treated with CAF6 and CAF12 . Furthermore, thickness of the whole retinal layer, outer nuclear layer, and ganglion cell count were decreased in diabetic rats compared to control and CAF6 and CAF12 treatments prevented these changes. CAF6 and CAF12 seem to be effective agents for treatment of diabetic retinopathy via attenuation of retinal oxidative stress and improvement of neuronal survival signaling. 相似文献
847.
DNA gyrase, an essential enzyme that regulates DNA topology in bacteria, is the target of fluoroquinolones. Three fluoroquinolone-resistant
mutants derived from one strain of Clostridium perfringens had amino acid substitutions of glycine 81 to cysteine, aspartic acid 87 to tyrosine, or both, in α-helix-4 of gyrase A.
The gyrase mutations affected the growth kinetics of mutants differently when the mutants were exposed to increasing concentrations
of gatifloxacin and ciprofloxacin. Fluoroquinolone concentration-dependent effects observed during growth in the exponential
and stationary phases depended on the presence of particular gyrA mutations. Introduction of a wild-type gyrA gene into the mutants enhanced their susceptibility to fluoroquinolones and decreased their growth rates proportional to
increases in fluoroquinolone concentrations. Amino acid substitutions in α-helix-4 of gyrase A protected C. perfringens from fluoroquinolones, and a strain with two substitutions was the most resistant. 相似文献
848.
Ahmed I. Younes Hampartsoum B. Barsoumian Duygu Sezen Vivek Verma Roshal Patel Mark Wasley Yun Hu Joe D. Dunn Kewen He Dawei Chen Hari Menon Fatemeh Masrorpour Meidi Gu Liangpeng Yang Nahum Puebla-Osorio Maria Angelica Cortez James W. Welsh 《Translational oncology》2021,14(2)
Radiotherapy (RT) has been used to control tumors by physically damaging DNA and inducing apoptosis; it also promotes antitumor immune responses via neoantigens release and augmenting immune-oncology agents to elicit systemic response. Tumor regression after RT can recruit inflammatory cells, such as tumor-associated macrophages and CD11b+ myeloid cell populations, a major subset of which may actually be immunosuppressive. However, these inflammatory cells also express Toll-like receptors (TLRs) that can be stimulated to reverse suppressive characteristics and promote systemic antitumor outcomes. Here, we investigated the effects of adding CMP-001, a CpG-A oligodeoxynucleotide TLR9 agonist delivered in a virus-like particle (VLP), to RT in two murine models (344SQ metastatic lung adenocarcinoma and CT26 colon carcinoma). High-dose RT (12Gy x 3 fractions) significantly increased the percentages of plasmacytoid dendritic cells within the tumor islets 3- and 5-days post-RT; adding CMP-001 after RT also enhanced adaptive immunity by increasing the proportion of CD4+ and CD8+ T cells. RT plus CMP-001-mediated activation of the immune system led to significant inhibition of tumor growth at both primary and abscopal tumor sites, thereby suggesting a new combinatorial treatment strategy for systemic disease. 相似文献
849.
Ravanrouy Fatemeh Niazi Ali Moghadam Ali Taghavi Seyed Mohsen 《Molecular biology reports》2021,48(10):6719-6728
Molecular Biology Reports - DNA methylation is one of the most important epigenetic event that regulates gene expression. In addition to DNA methylation, transgene copy number may induce gene... 相似文献
850.
Darzi Sina Mirzaei Seyed Abbas Elahian Fatemeh Peymani Amir Rahmani Babak Pishkhan Dibazar Shaghayegh Shirian Sadegh Shakeri Chaleshtori Leila Aali Ehsan 《Molecular biology reports》2021,48(11):7105-7111
Molecular Biology Reports - Flavonoids have been demonstrated to have the ability of sensitizing cancer cells to chemotherapy and inverse multidrug resistance via various mechanisms, such as... 相似文献