全文获取类型
收费全文 | 1210篇 |
免费 | 90篇 |
出版年
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 31篇 |
2020年 | 19篇 |
2019年 | 26篇 |
2018年 | 26篇 |
2017年 | 23篇 |
2016年 | 39篇 |
2015年 | 70篇 |
2014年 | 72篇 |
2013年 | 104篇 |
2012年 | 109篇 |
2011年 | 114篇 |
2010年 | 63篇 |
2009年 | 74篇 |
2008年 | 74篇 |
2007年 | 74篇 |
2006年 | 68篇 |
2005年 | 47篇 |
2004年 | 53篇 |
2003年 | 34篇 |
2002年 | 35篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1986年 | 7篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1964年 | 1篇 |
1934年 | 1篇 |
1933年 | 1篇 |
1926年 | 1篇 |
排序方式: 共有1300条查询结果,搜索用时 15 毫秒
991.
992.
Jia Guogang Triulzi C. Marzano F. Nonnis Belli M. Sansone U. Vaghi M. 《Biological trace element research》1999,(1):349-357
A radioecological survey in Antarctica shows that the239+240Pu,238Pu,241Am,90Sr, and137Cs activities were detectable in nearly all the samples. The activity level of239+240Pu,241Am, and137Cs in antarctic sediments was about 5–20 times lower than in the northern Adriatic Sea sediments, but the238Pu activities were relatively high. It was interesting to note that the90Sr concentrations in all the sediments tended to be low, which could be the result of the easier exchangeable behavior of90Sr in water. High concentrations were detected in mosses and lichens and their activity levels were comparable to those in
central Italy. The radionuclide ratio analyses show that the major part of239+240Pu,241Am,90Sr, and137Cs was a result of nuclear weapon tests. The higher241Am/239+240Pu ratio was observed and it could perhaps be the result of fallout of nuclear weapon tests prior to 1962. The238Pu/239+240Pu ratio in the antarctic matrices was about seven times higher than in the Northern hemisphere and it could be inferred that
the major part of238Pu was originating from the SNAP-9A satellite accident. 相似文献
993.
Rafael Franco Berta Casanovas Jordi Camps Gemma Navarro Eva Martínez-Pinilla 《Current issues in molecular biology》2021,43(2):650
Although antioxidants can act locally to react with an oxidant, oral administration of “antioxidants” is quite useless in treating oxidative stress in tissues. Furthermore, it does not make sense to consider a vitamin as an antioxidant, but vitamin B3 leads to the in vivo formation of compounds that are essential for reducing this stress. A rigorous treatment of the subject indicates that to deal with oxidative stress, the most direct approach is to enhance the innate antioxidant mechanisms. The question is whether this is possible through daily activities. Diets can contain the necessary components for these mechanisms or may induce the expression of the genes involved in them. Another possibility is that pro-oxidant molecules in food increase the sensitivity and power of the detoxification pathways. This option is based on well-known DNA repair mechanisms after exposure to radiation (even from the Sun), or strong evidence of induction of antioxidant capacity after exposure to powerful pro-oxidants such as H2O2. More experimental work is required to test whether some molecules in food can increase the expression of antioxidant enzymes and/or improve antioxidant mechanisms. Identifying effective molecules to achieve such antioxidant power is critical to the food and nutraceutical industries. The potential of diet-based interventions to combat oxidative stress must be viewed from a new perspective. 相似文献
994.
Subdominant CD8+ T-cell responses are involved in durable control of AIDS virus replication
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Friedrich TC Valentine LE Yant LJ Rakasz EG Piaskowski SM Furlott JR Weisgrau KL Burwitz B May GE León EJ Soma T Napoe G Capuano SV Wilson NA Watkins DI 《Journal of virology》2007,81(7):3465-3476
"Elite controllers" are individuals that durably control human immunodeficiency virus or simian immunodeficiency virus replication without therapeutic intervention. The study of these rare individuals may facilitate the definition of a successful immune response to immunodeficiency viruses. Here we describe six Indian-origin rhesus macaques that have controlled replication of the pathogenic virus SIVmac239 for 1 to 5 years. To determine which lymphocyte populations were responsible for this control, we transiently depleted the animals' CD8+ cells in vivo. This treatment resulted in 100- to 10,000-fold increases in viremia. When the CD8+ cells returned, control was reestablished and the levels of small subsets of previously subdominant CD8+ T cells expanded up to 2,500-fold above pre-depletion levels. This wave of CD8+ T cells was accompanied by robust Gag-specific CD4 responses. In contrast, CD8+ NK cell frequencies changed no more than threefold. Together, our data suggest that CD8+ T cells targeting a small number of epitopes, along with broad CD4+ T-cell responses, can successfully control the replication of the AIDS virus. It is likely that subdominant CD8+ T-cell populations play a key role in maintaining this control. 相似文献
995.
Oxidative stress in retinal pigment epithelium cells increases exosome secretion and promotes angiogenesis in endothelial cells
下载免费PDF全文
![点击此处可从《Journal of cellular and molecular medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sandra Atienzar‐Aroca Miguel Flores‐Bellver Gemma Serrano‐Heras Natalia Martinez‐Gil Jorge M. Barcia Silvia Aparicio Daniel Perez‐Cremades Jose M. Garcia‐Verdugo Manuel Diaz‐Llopis Francisco J. Romero Javier Sancho‐Pelluz 《Journal of cellular and molecular medicine》2016,20(8):1457-1466
The retinal pigment epithelium (RPE), a monolayer located between the photoreceptors and the choroid, is constantly damaged by oxidative stress, particularly because of reactive oxygen species (ROS). As the RPE, because of its physiological functions, is essential for the survival of the retina, any sustained damage may consequently lead to loss of vision. Exosomes are small membranous vesicles released into the extracellular medium by numerous cell types, including RPE cells. Their cargo includes genetic material and proteins, making these vesicles essential for cell‐to‐cell communication. Exosomes may fuse with neighbouring cells influencing their fate. It has been observed that RPE cells release higher amounts of exosomes when they are under oxidative stress. Exosomes derived from cultured RPE cells were isolated by ultracentrifugation and quantified by flow cytometry. VEGF receptors (VEGFR) were analysed by both flow cytometry and Western blot. RT‐PCR and qPCR were conducted to assess mRNA content of VEGFRs in exosomes. Neovascularization assays were performed after applying RPE exosomes into endothelial cell cultures. Our results showed that stressed RPE cells released a higher amount of exosomes than controls, with a higher expression of VEGFR in the membrane, and enclosed an extra cargo of VEGFR mRNA. Angiogenesis assays confirmed that endothelial cells increased their tube formation capacity when exposed to stressed RPE exosomes. 相似文献
996.
997.
Plasma proteomics of lung cancer by a linkage of multi-dimensional liquid chromatography and two-dimensional difference gel electrophoresis 总被引:3,自引:0,他引:3
Okano T Kondo T Kakisaka T Fujii K Yamada M Kato H Nishimura T Gemma A Kudoh S Hirohashi S 《Proteomics》2006,6(13):3938-3948
To investigate aberrant plasma proteins in lung cancer, we compared the proteomic profiles of serum from five lung cancer patients and from four healthy volunteers. Immuno-affinity chromatography was used to deplete highly abundant plasma proteins, and the resulting plasma samples were separated into eight fractions by anion-exchange chromatography. Quantitative protein profiles of the fractionated samples were generated by two-dimensional difference gel electrophoresis, in which the experimental samples and the internal control samples were labeled with different dyes and co-separated by two-dimensional polyacrylamide gel electrophoresis. This approach succeeded in resolving 3890 protein spots. For 364 of the protein spots, the expression level in lung cancer was more than twofold different from that in the healthy volunteers. These differences were statistically significant (Student's t-test, p-value less than 0.05). Mass spectrometric protein identification revealed that the 364 protein spots corresponded to 58 gene products, including the classical plasma proteins and the tissue-leakage proteins catalase, clusterin, ficolin, gelsolin, lumican, tetranectin, triosephosphate isomerase and vitronectin. The combination of multi-dimensional liquid chromatography and two-dimensional difference gel electrophoresis provides a valuable tool for serum proteomics in lung cancer. 相似文献
998.
Scabini M Stellari F Cappella P Rizzitano S Texido G Pesenti E 《Apoptosis : an international journal on programmed cell death》2011,16(2):198-207
In vivo imaging of apoptosis in a preclinical setting in anticancer drug development could provide remarkable advantages in
terms of translational medicine. So far, several imaging technologies with different probes have been used to achieve this
goal. Here we describe a bioluminescence imaging approach that uses a new formulation of Z-DEVD-aminoluciferin, a caspase
3/7 substrate, to monitor in vivo apoptosis in tumor cells engineered to express luciferase. Upon apoptosis induction, Z-DEVD-aminoluciferin
is cleaved by caspase 3/7 releasing aminoluciferin that is now free to react with luciferase generating measurable light.
Thus, the activation of caspase 3/7 can be measured by quantifying the bioluminescent signal. Using this approach, we have
been able to monitor caspase-3 activation and subsequent apoptosis induction after camptothecin and temozolomide treatment
on xenograft mouse models of colon cancer and glioblastoma, respectively. Treated mice showed more than 2-fold induction of
Z-DEVD-aminoluciferin luminescent signal when compared to the untreated group. Combining D-luciferin that measures the total tumor burden, with Z-DEVD-aminoluciferin that assesses apoptosis induction via caspase
activation, we confirmed that it is possible to follow non-invasively tumor growth inhibition and induction of apoptosis after
treatment in the same animal over time. Moreover, here we have proved that following early apoptosis induction by caspase
3 activation is a good biomarker that accurately predicts tumor growth inhibition by anti-cancer drugs in engineered colon
cancer and glioblastoma cell lines and in their respective mouse xenograft models. 相似文献
999.
Judit Berman Changfu Zhu Eduard Pérez-Massot Gemma Arjó Uxue Zorrilla-López Gemma Masip Raviraj Banakar Georgina Sanahuja Gemma Farré Bruna Miralpeix Chao Bai Evangelia Vamvaka Maite Sabalza Richard M. Twyman Ludovic Bassié Teresa Capell Paul Christou 《Plant molecular biology》2013,83(1-2):5-19
Genetically engineered (GE) crops can be used as part of a combined strategy to address food insecurity, which is defined as a lack of sustainable access to safe and nutritious food. In this article, we discuss the causes and consequences of food insecurity in the developing world, and the indirect economic impact on industrialized countries. We dissect the healthcare costs and lost productivity caused by food insecurity, and evaluate the relative merits of different intervention programs including supplementation, fortification and the deployment of GE crops with higher yields and enhanced nutritional properties. We provide clear evidence for the numerous potential benefits of GE crops, particularly for small-scale and subsistence farmers. GE crops with enhanced yields and nutritional properties constitute a vital component of any comprehensive strategy to tackle poverty, hunger and malnutrition in developing countries and thus reduce the global negative economic effects of food insecurity. 相似文献
1000.
Daniel Canals David Mormeneo Gemma Fabriàs Amadeu Llebaria Josefina Casas Antonio Delgado 《Bioorganic & medicinal chemistry》2009,17(1):235-241
The synthesis of isomeric jaspines (anhydro phytosphingosines), arising from intramolecular cyclization of the corresponding phytosphingosines with different configurations at C3 and C4 positions of the sphingoid backbone, is reported. Natural jaspine B is the most cytotoxic isomer on A549 cells and it induces cell death in a dose-dependent manner. The cytotoxicity of jaspine B has been correlated with a significant increase of intracellular dihydroceramides, which seem to play an active role in autophagy. 相似文献