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151.
CDP-diacylglycerol for polyglycerophosphatide biogenesis can be synthesized within rat liver mitochondria. This membrane-associated enzyme was predominantly located in the inner mitochondrial membrane. GTP had a significant effect in activating the microsomal CDP-diacylglycerol synthase, especially if the microsomes were preincubated with GTP in the presence of phosphatidic acid. This stimulatory effect of GTP on the microsomal enzyme was not detected in the mitochondrial fractions. The enzymes could be solubilized from the membrane fractions using CHAPS, and the detergent-soluble activity partially restored by addition of phospholipids. Mitochondrial and microsomal CDP-diacylglycerol synthase activity could be completely separated by anion-exchange column chromatography. The mitochondrial and microsomal CDP-diacylglycerol synthases appear to be two distinct enzymes with different localization and regulatory characteristics. 相似文献
152.
DANIEL T. KSEPKA AMY M. BALANOFF STIG WALSH ARIEL REVAN AMY HO 《Zoological Journal of the Linnean Society》2012,166(1):202-219
Penguins have undergone dramatic changes associated with the evolution of underwater flight and subsequent loss of aerial flight, which are manifest and well documented in the musculoskeletal system and integument. Significant modification of neurosensory systems and endocranial spaces may also be expected along this locomotor transition. However, no investigations of the brain and sensory organs of extinct stem lineage Sphenisciformes have been carried out, and few data exist even for extant species of Spheniscidae. In order to explore neuroanatomical evolution in penguins, we generated virtual endocasts for the early Miocene stem penguin Paraptenodytes antarcticus, three extant penguin species (Pygoscelis antarctica, Aptenodytes patagonicus, Spheniscus magellanicus), and two outgroup species (the common loon Gavia immer and the Laysan albatross Phoebastria immutabilis). These endocasts yield new anatomical data and phylogenetically informative characters from the brain, carotid arteries, pneumatic recesses, and semicircular canal system. Despite having undergone over 60 million years of evolution since the loss of flight, penguins retain many attributes traditionally linked to flight. Features associated with visual acuity and proprioception, such as the sagittal eminence and flocculus, show a similar degree of development to those of volant birds in the three extant penguins and Paraptenodytes antarcticus. These features, although clearly not flight‐related in penguins, are consistent with the neurological demands associated with rapid manoeuvring in complex aquatic environments. Semicircular canal orientation in penguins is similar to volant birds. Interestingly, canal radius is grossly enlarged in the fossil taxon Pa. antarcticus compared to living penguins and outgroups. In contrast to all other living birds, the contralateral anterior tympanic recesses of extant penguins do not communicate. An interaural pathway connecting these recesses is retained in Pa. antarcticus, suggesting that stem penguins may still have employed this connection, potentially to enhance directional localization of sound. Paedomorphosis, already identified as a potential factor in crown clade penguin skeletal morphology, may also be implicated in the failure of an interaural pathway to form during ontogeny in extant penguins. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 202–219. 相似文献
153.
Zeatin is a highly active and ubiquitous cytokinin. O-Glycosylation of zeatin occurs widely in plant tissues and is likely to be important in regulating the level of active cytokinins. Enzymes mediating the conversion of zeatin to O-glucosylzeatin and O-xylosylzeatin have been isolated from Phaseolus seeds. The corresponding genes have been cloned recently. The current status of molecular and biochemical studies of these genes and enzymes is summarised in this paper. 相似文献
154.
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156.
A polyelectrolyte complex micelle (PECM)-based delivery system for targeting folate (FOL) receptor overexpressing tumor cells is demonstrated using poly(ethylene glycol) (PEG)-conjugated oligonucleotide (ODN). The tumor targeting property was conferred to the PECM by tethering a folate moiety to the distal end of the PEG segment in an anti-sense green fluorescent protein (GFP) ODN-PEG conjugate. Nanoscale PECMs were spontaneously produced from ionic interactions between the ODN-PEG-FOL conjugate and a cationic lipid, lipofectamine (Lf). When treated with FOL receptor overexpressing cells (KB), the PCEMs caused a significant reduction in GFP expression in a dose-dependent manner. This effect was not observed in FOL receptor deficient cells (A549). The enhanced transfection of ODN-PEG-FOL/Lf PECMs to KB cells was caused by FOL receptor mediated endocytosis. The efficiency of target-specific gene suppression by ODN-PEG-FOL/Lf PECMs was maintained even in the presence of 10% fetal bovine serum in the transfection medium. 相似文献
157.
BACKGROUND: The unique potential of mesenchymal stromal cells (MSC) has generated much research interest recently, particularly in exploring the regenerative nature of these cells. Previously, MSC were thought to be found only in the BM. However, further studies have shown that MSC can also be isolated from umbilical cord blood, adipose tissue and amniotic fluid. In this study, we explored the possibility of MSC residing in the cornea. METHODS: Human cornea tissues were chopped to fine pieces and cultured in DMEM supplemented with 10% FBS. After a few days, the crude pieces of cornea were removed. Isolated keratocytes that were adherent to tissue culture flasks were grown until confluency before being passaged further. The immunophenotype was evaluated by flow cytometry. Assays were performed to differentiate cultured cells into adipocytes and osteocytes. RESULTS: Isolated corneal keratocytes exhibited a fibroblastoid morphology and expressed CD13, CD29, CD44, CD56, CD73, CD90, CD105 and CD133, but were negative for HLA-DR, CD34, CD117 and CD45. These properties are similar to those of BM-MSC (BM-MSC). In addition, corneal keratocytes were able to differentiate into adipocytes and osteocytes. DISCUSSION: Our results indicate that corneal keratocytes have MSC-like properties similar to those of BM-MSC. This study opens up the possibility of using BM-MSC in corneal tissue engineering and regeneration. Furthermore, discarded corneal tissue can also be used to generate MSC for tissue engineering purposes. 相似文献
158.
BACKGROUND: The multipotency of stromal cells has been studied extensively. It has been reported that mesenchymal stromal cells (MSC) are capable of differentiating into cells of multilineage. Different methods and reagents have been used to induce the differentiation of MSC. We investigated the efficacy of different growth factors in inducing MSC differentiation into neurons. METHODS: MSC from human BM were isolated and cultured in media supplemented with 10% FBS. These cells were identified and later induced to differentiate into neuron-like cells using different neurotrophic factors. Three different growth factors were used, either alone or in combination: brain-derived neurotrophic factor, epidermal growth factor and neural growth factor. RESULTS: After 10 days of culture, MSC showed neuron-like morphologic changes. Immunostaining showed that these cells expressed markers for neurons (growth-associated protein-43, neuron-specific nuclear protein and neurofilament 200 kDa) and expression of these markers suggested the transition of immature stages to more mature stages of neuron-like cells. DISCUSSION: Our results show that BM-derived MSC can differentiate not only into target cells of mesodermal origin but also neuron-like cells of ectodermal origin. The findings show that a combination of growth factors is more effective in inducing MSC into neuron-like cells. 相似文献
159.
S Min J Meehan LM Sullivan NP Harte Y Xie GP Davey C Svanborg A Brodkorb KH Mok 《Biochemical Society transactions》2012,40(4):746-751
HAMLET (human α-lactalbumin made lethal to tumour cells) and its related partially unfolded protein-fatty acid complexes are novel biomolecular nanoparticles that possess relatively selective cytotoxic activities towards tumour cells. One of the key characteristics is the requirement for the protein to be partially unfolded, hence endowing native proteins with additional functions in the alternatively folded states. Beginning with the history of its discovery and development, the cellular targets that appear to be strongly correlated with tumour cell death are introduced in the present article. 相似文献
160.
Alexander Sasha Dubrovsky Bethany J. Foster Roman Jednak Elise Mok David McGillivray 《CMAJ》2012,184(15):E796-E803