全文获取类型
收费全文 | 2239篇 |
免费 | 138篇 |
出版年
2024年 | 3篇 |
2023年 | 3篇 |
2022年 | 21篇 |
2021年 | 40篇 |
2020年 | 23篇 |
2019年 | 39篇 |
2018年 | 64篇 |
2017年 | 38篇 |
2016年 | 47篇 |
2015年 | 98篇 |
2014年 | 143篇 |
2013年 | 179篇 |
2012年 | 229篇 |
2011年 | 182篇 |
2010年 | 119篇 |
2009年 | 117篇 |
2008年 | 170篇 |
2007年 | 128篇 |
2006年 | 119篇 |
2005年 | 126篇 |
2004年 | 108篇 |
2003年 | 99篇 |
2002年 | 77篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 21篇 |
1998年 | 32篇 |
1997年 | 20篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有2377条查询结果,搜索用时 15 毫秒
21.
Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation
下载免费PDF全文
![点击此处可从《Plant, cell & environment》网站下载免费的PDF全文](/ch/ext_images/free.gif)
NúRIA Garcia‐Forner Henry D. Adams Sanna Sevanto Adam D. Collins Lee T. Dickman Patrick J. Hudson Melanie J.B. Zeppel Michael W. Jenkins Heath Powers Jordi Martínez‐Vilalta Nate G. Mcdowell 《Plant, cell & environment》2016,39(1):38-49
Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co‐occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies. 相似文献
22.
Cigliano L D'Andrea LD Maresca B Serino M Carlucci A Salvatore A Spagnuolo MS Scigliuolo G Pedone C Abrescia P 《Biological chemistry》2008,389(11):1421-1426
The high-density lipoprotein apolipoprotein A-I (ApoA-I) stimulates the enzyme lecithin-cholesterol acyltransferase (LCAT) in the reverse cholesterol transport pathway. Two ApoA-I variants, Zaragoza (L144R) and Zavalla (L159P), are associated with low levels of HDL-cholesterol but normal LCAT activity. Haptoglobin interacts with ApoA-I, impairing LCAT stimulation. Synthetic peptides matching the haptoglobin-binding site of native or variant ApoA-I (native, P2a; variants, Zav-pep and Zar-pep) bound haptoglobin with different activity: Zar-pep>P2a>Zav-pep. They also differently rescued LCAT in vitro activity in the presence of haptoglobin (P2a=Zar-pep>Zav-pep). Therefore, both amino acid conversions affect haptoglobin binding and LCAT regulation. We highlight the role of haptoglobin in LCAT regulation in subjects with ApoA-I variants. 相似文献
23.
Wangxiao He Pietro Mazzuca Weirong Yuan Kristen Varney Antonella Bugatti Alfredo Cagnotto Cinzia Giagulli Marco Rusnati Stefania Marsico Luisa Diomede Mario Salmona Arnaldo Caruso Wuyuan Lu Francesca Caccuri 《Biochimica et Biophysica Acta (BBA)/General Subjects》2019,1863(1):13-24
Background
HIV-1 matrix protein p17 variants (vp17s) detected in HIV-1-infected patients with non-Hodgkin's lymphoma (HIV-NHL) display, differently from the wild-type protein (refp17), B cell growth-promoting activity. Biophysical analysis revealed that vp17s are destabilized as compared to refp17, motivating us to explore structure-function relationships.Methods
We used: biophysical techniques (circular dichroism (CD), nuclear magnetic resonance (NMR) and thermal/GuHCL denaturation) to study protein conformation and stability; Surface plasmon resonance (SPR) to study interactions; Western blot to investigate signaling pathways; and Colony Formation and Soft Agar assays to study B cell proliferation and clonogenicity.Results
By forcing the formation of a disulfide bridge between Cys residues at positions 57 and 87 we obtained a destabilized p17 capable of promoting B cell proliferation. This finding prompted us to dissect refp17 to identify the functional epitope. A synthetic peptide (F1) spanning from amino acid (aa) 2 to 21 was found to activate Akt and promote B cell proliferation and clonogenicity. Three positively charged aa (Arg15, Lys18 and Arg20) proved critical for sustaining the proliferative activity of both F1 and HIV-NHL-derived vp17s. Lack of any interaction of F1 with the known refp17 receptors suggests an alternate one involved in cell proliferation.Conclusions
The molecular reasons for the proliferative activity of vp17s, compared to refp17, relies on the exposure of a functional epitope capable of activating Akt.General significance
Our findings pave the way for identifying the receptor(s) responsible for B cell proliferation and offer new opportunities to identify novel treatment strategies in combating HIV-related NHL. 相似文献24.
Identification of tissue transglutaminase-reactive lysine residues in glyceraldehyde-3-phosphate dehydrogenase
下载免费PDF全文
![点击此处可从《Protein science : a publication of the Protein Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stefania Orru Margherita Ruoppolo Simona Francese Luigi Vitagliano Gennaro Marino Carla Esposito 《Protein science : a publication of the Protein Society》2002,11(1):137-146
Polyglutamine domains are excellent substrates for tissue transglutaminase resulting in the formation of cross-links with polypeptides containing lysyl residues. This finding suggests that tissue transglutaminase may play a role in the pathology of neurodegenerative diseases associated with polyglutamine expansion. The glycolytic enzyme GAPDH previously was shown to tightly bind several proteins involved in such diseases. The present study confirms that GAPDH is an in vitro lysyl donor substrate of tissue transglutaminase. A dansylated glutamine-containing peptide was used as probe for labeling the amino-donor sites. SDS gel electrophoresis of a time-course reaction mixture revealed the presence of both fluorescent GAPDH monomers and high molecular weight polymers. Western blot analysis performed using antitransglutaminase antibodies reveals that tissue transglutaminase takes part in the formation of heteropolymers. The reactive amino-donor sites were identified using mass spectrometry. Here, we report that of the 26 lysines present in GAPDH, K191, K268, and K331 were the only amino-donor residues modified by tissue transglutaminase. 相似文献
25.
In a batch cultivation of Pichia pastoris expressing Candida rugosa lipase 1 (CRL1), secretion of 200 microg lipase ml(-1) of culture was achieved in sorbitol-based medium. However, a large amount of recombinant protein was retained intracellularly throughout the fermentation, pointing to the transport step as a major bottleneck. Therefore a translational fusion with the green fluorescent protein (GFP) was constructed that was expressed and transported similarly to the native lipase and retained catalytic activity. This analytical tool enables a rapid monitoring of product localization and amount, based on GFP-associated fluorescence. 相似文献
26.
Yan G. Ni Jon H. Condra Laura Orsatti Xun Shen Stefania Di Marco Shilpa Pandit Matthew J. Bottomley Lionello Ruggeri Richard T. Cummings Rose M. Cubbon Joseph C. Santoro Anka Ehrhardt Dale Lewis Timothy S. Fisher Sookhee Ha Leila Njimoluh Dana D. Wood Holly A. Hammond Douglas Wisniewski Cinzia Volpari Alessia Noto Paola Lo Surdo Brian Hubbard Andrea Carf�� Ayesha Sitlani 《The Journal of biological chemistry》2010,285(17):12882-12891
27.
Robert M. Stefani Sofia Barbosa Andrea R. Tan Stefania Setti Aaron M. Stoker Gerard A. Ateshian Ruggero Cadossi Gordana Vunjak-Novakovic Roy K. Aaron James L. Cook J. Chloë Bulinski Clark T. Hung 《Biotechnology and bioengineering》2020,117(5):1584-1596
Articular cartilage injuries are a common source of joint pain and dysfunction. We hypothesized that pulsed electromagnetic fields (PEMFs) would improve growth and healing of tissue-engineered cartilage grafts in a direction-dependent manner. PEMF stimulation of engineered cartilage constructs was first evaluated in vitro using passaged adult canine chondrocytes embedded in an agarose hydrogel scaffold. PEMF coils oriented parallel to the articular surface induced superior repair stiffness compared to both perpendicular PEMF (p = .026) and control (p = .012). This was correlated with increased glycosaminoglycan deposition in both parallel and perpendicular PEMF orientations compared to control (p = .010 and .028, respectively). Following in vitro optimization, the potential clinical translation of PEMF was evaluated in a preliminary in vivo preclinical adult canine model. Engineered osteochondral constructs (∅ 6 mm × 6 mm thick, devitalized bone base) were cultured to maturity and implanted into focal defects created in the stifle (knee) joint. To assess expedited early repair, animals were assessed after a 3-month recovery period, with microfracture repairs serving as an additional clinical control. In vivo, PEMF led to a greater likelihood of normal chondrocyte (odds ratio [OR]: 2.5, p = .051) and proteoglycan (OR: 5.0, p = .013) histological scores in engineered constructs. Interestingly, engineered constructs outperformed microfracture in clinical scoring, regardless of PEMF treatment (p < .05). Overall, the studies provided evidence that PEMF stimulation enhanced engineered cartilage growth and repair, demonstrating a potential low-cost, low-risk, noninvasive treatment modality for expediting early cartilage repair. 相似文献
28.
Anna Maria Sacco Immacolata Belviso Veronica Romano Antonia Carfora Fabrizio Schonauer Daria Nurzynska Stefania Montagnani Franca Di Meglio Clotilde Castaldo 《Journal of cellular and molecular medicine》2019,23(6):4256-4268
Induced pluripotent stem cells (iPSCs) are adult somatic cells genetically reprogrammed to an embryonic stem cell‐like state. Notwithstanding their autologous origin and their potential to differentiate towards cells of all three germ layers, iPSC reprogramming is still affected by low efficiency. As dermal fibroblast is the most used human cell for reprogramming, we hypothesize that the variability in reprogramming is, at least partially, because of the skin fibroblasts used. Human dermal fibroblasts harvested from five different anatomical sites (neck, breast, arm, abdomen and thigh) were cultured and their morphology, proliferation, apoptotic rate, ability to migrate, expression of mesenchymal or epithelial markers, differentiation potential and production of growth factors were evaluated in vitro. Additionally, gene expression analysis was performed by real‐time PCR including genes typically expressed by mesenchymal cells. Finally, fibroblasts isolated from different anatomic sites were reprogrammed to iPSCs by integration‐free method. Intriguingly, while the morphology of fibroblasts derived from different anatomic sites differed only slightly, other features, known to affect cell reprogramming, varied greatly and in accordance with anatomic site of origin. Accordingly, difference also emerged in fibroblasts readiness to respond to reprogramming and ability to form colonies. Therefore, as fibroblasts derived from different anatomic sites preserve positional memory, it is of great importance to accurately evaluate and select dermal fibroblast population prior to induce reprogramming. 相似文献
29.
Alessia Carocci Alessia Catalano Maria Stefania Sinicropi Giuseppe Genchi 《Biometals》2018,31(5):715-735
Many evidences indicate that oxidative stress plays a significant role in a variety of human disease states, including neurodegenerative diseases. Iron is an essential metal for almost all living organisms due to its involvement in a large number of iron-containing proteins and enzymes, though it could be also toxic. Actually, free iron excess generates oxidative stress, particularly in brain, where anti-oxidative defences are relatively low. Its accumulation in specific regions is associated with pathogenesis in a variety of neurodegenerative diseases (i.e., Parkinson’s disease, Alzheimer’s disease, Huntington’s chorea, Amyotrophic Lateral Sclerosis and Neurodegeneration with Brain Iron Accumulation). Anyway, the extent of toxicity is dictated, in part, by the localization of the iron complex within the cell (cytosolic, lysosomal and mitochondrial), its biochemical form, i.e., ferritin or hemosiderin, as well as the ability of the cell to prevent the generation and propagation of free radical by the wide range of antioxidants and cytoprotective enzymes in the cell. Particularly, ferrous iron can act as a catalyst in the Fenton reaction that potentiates oxygen toxicity by generating a wide range of free radical species, including hydroxyl radicals (·OH). The observation that patients with neurodegenerative diseases show a dramatic increase in their brain iron content, correlated with the production of reactive oxigen species in these areas of the brain, conceivably suggests that disturbances in brain iron homeostasis may contribute to the pathogenesis of these disorders. The aim of this review is to describe the chemical features of iron in human beings and iron induced toxicity in neurodegenerative diseases. Furthermore, the attention is focused on metal chelating drugs therapeutic strategies. 相似文献
30.