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排序方式: 共有626条查询结果,搜索用时 19 毫秒
31.
Moffat BA Reddy GR McConville P Hall DE Chenevert TL Kopelman RR Philbert M Weissleder R Rehemtulla A Ross BD 《Molecular imaging》2003,2(4):324-332
A novel polyacrylamide superparamagnetic iron oxide nanoparticle platform is described which has been synthetically prepared such that multiple crystals of iron oxide are encapsulated within a single polyacrylamide matrix (PolyAcrylamide Magnetic [PAM] nanoparticles). This formulation provides for an extremely large T2 and T2* relaxivity of between 620 and 1140 sec(-1) mM(-1). Administration of PAM nanoparticles into rats bearing orthotopic 9L gliomas allowed quantitative pharmacokinetic analysis of the uptake of nanoparticles in the vasculature, brain, and glioma. Addition of polyethylene glycol of varying sizes (0.6, 2, and 10 kDa) to the surface of the PAM nanoparticles resulted in an increase in plasma half-life and affected tumor uptake and retention of the nanoparticles as quantified by changes in tissue contrast using MRI. The flexible formulation of these nanoparticles suggests that future modifications could be accomplished allowing for their use as a targeted molecular imaging contrast agent and/or therapeutic platform for multiple indications. 相似文献
32.
Metastatic mammary tumors in rats were treated by laser immunotherapy. Tumors injected by a laserabsorbing dye and an immunoadjuvant were irradiated non-invasively by a near-infrared laser. The successfully cured rats developed a long-term resistance to repeated tumor challenges. Using the sera from cured rats as the source of primary antibodies, immune responses induced by laser immunotherapy were observed in both cellular and molecular levels using histochemical assays and Western blot analysis. 相似文献
33.
Gerhard J. Magis Willem G. Onderwaater C. Neil Hunter Raoul N. Frese 《生物化学与生物物理学报:生物膜》2010,1798(3):637-39171
Photosynthetic membranes comprise a network of light harvesting and reaction center pigment-protein complexes responsible for the primary photoconversion reactions: light absorption, energy transfer and electron cycling. The structural organization of membranes of the purple bacterial species Rb. sphaeroides has been elucidated in most detail by means of polarized light spectroscopy and atomic force microscopy. Here we report a functional characterization of native and untreated membranes of the same species adsorbed onto a gold surface. Employing fluorescence confocal spectroscopy and light-induced electrochemistry we show that adsorbed membranes maintain their energy and electron transferring functionality. Gold-adsorbed membranes are shown to generate a steady high photocurrent of 10 μA/cm2 for several minutes and to maintain activity for up to three days while continuously illuminated. The surface-adsorbed membranes exhibit a remarkable functionality under aerobic conditions, even when exposed to light intensities well above that of direct solar irradiation. The component at the interface of light harvesting and electron cycling, the LH1 complex, displays exceptional stability, likely contributing to the robustness of the membranes. Peripheral light harvesting LH2 complexes show a light intensity dependent decoupling from photoconversion. LH2 can act as a reversible switch at low-light, an increased emitter at medium light and photobleaches at high light. 相似文献
34.
Two male plumage morphs, 'white' and 'rufous', coexist in the Madagascar paradise flycatcher Terpsiphone mutata . There has been enduring debate about whether this dimorphism in male plumage represents seasonal dichromatism, delayed plumage maturation, or genetic differences. We present data from a nine-year study monitoring plumage changes in 119 individually colour-banded males (430 male-years). Our data show that paradise flycatchers are not seasonally dichromatic, and that although males show delayed plumage maturation, the rufous morph is not simply a precursor to white plumage, as previously thought. Individual males followed irreversible developmental pathways to 'rufous' or 'white', and could be reliably assigned to these distinct phenotypes by their second year. 'White' males adopted definitive plumage by the age of three years, whereas 'rufous' males did so between the ages of three and six years. The fixed nature of these morphs suggests that a genetic basis for the dichromatism is likely. However, variation in the timing of definitive plumage acquisition in rufous males could involve condition dependence and be environmentally influenced. 相似文献
35.
Paired male and female eastern whipbirds, Psophodes olivaceus,sing precisely coordinated, male-led duets. Four broad explanationshave been proposed for the function of duets: 1) cooperativeresource defense, 2) prevention of partner usurpation, 3) defenseof an individual's own position within the partnership, or 4)mate identification and localization. These 4 hypotheses makedifferent predictions about how male and female residents shouldrespond to simulated intrusion by other pairs or individuals.We compared the behavioral and vocal responses of 20 pairs ofeastern whipbirds to simulated territorial intrusions by: 1)a solitary singing male, 2) a solitary singing female, and 3)a duetting pair. Males and females did not coordinate theirapproach to the playback speaker and showed sex-specific responsesto playback. Males did not respond differently to duetting versussolo singing intruders. By contrast, females approached moreclosely during solo female song than during solo male song orduet playback. Females also produced specific vocalizationsonly in response to duet and solo female playback. Both sexesapproached the speaker more closely and quickly during playbackof same-sex solo songs than opposite-sex solo songs. Finally,females answered more of their mate's songs during simulatedintrusion by a lone female than during simulated intrusion bya lone male. Our results suggest that duets in this speciesprimarily function to allow females to defend their exclusiveposition in a partnership. Mate defense by females is unusualin birds but may be promoted in eastern whipbirds by a female-biasedsex ratio and the need for exclusive access to male care. Thus,duets result from independent and conflicting strategies ofmate and territory defense in males and females. 相似文献
36.
Kasperavičiūtė D Catarino CB Chinthapalli K Clayton LM Thom M Martinian L Cohen H Adalat S Bockenhauer D Pope SA Lench N Koltzenburg M Duncan JS Hammond P Hennekam RC Land JM Sisodiya SM 《PloS one》2011,6(8):e23182
Background
Patients with epilepsy often suffer from other important conditions. The existence of such co-morbidities is frequently not recognized and their relationship with epilepsy usually remains unexplained.Methodology/Principal Findings
We describe three patients with common, sporadic, non-syndromic epilepsies in whom large genomic microdeletions were found during a study of genetic susceptibility to epilepsy. We performed detailed gene-driven clinical investigations in each patient. Disruption of the function of genes in the deleted regions can explain co-morbidities in these patients.Conclusions/Significance
Co-morbidities in patients with epilepsy can be part of a genomic abnormality even in the absence of (known) congenital malformations or intellectual disabilities. Gene-driven phenotype examination can also reveal clinically significant unsuspected condition. 相似文献37.
Counter-adaptations of predators towards their prey are a far less investigated phenomenon in predator-prey interactions.
Caudal autotomy is generally considered an effective last-resort mechanism for evading predators. However, in victim-exploiter
relationships, the efficacy of a strategy will obviously depend on the antagonist’s ability to counter it. In the logic of
the predator-prey arms race, one would expect predators to develop attack strategies that minimize the chance of autotomy
of the prey and damage on the predator. We tested whether avian predators preferred grasping lizards by their head. We constructed
plasticine models of the Italian wall lizard (Podarcis sicula) and placed them in natural habitat of the species. Judging from counts of beak marks on the models, birds preferentially
attack the head and might also avoid the tail and limb regions. While a preference for the head might not necessarily demonstrate
tail and limb avoidance, this topic needs further exploration because it suggests that even unspecialised avian predators
may see through the lizard’s trick-of-the-tail. This result may have implications for our understanding of the evolution of
this peculiar defensive system and the loss or decreased tendency to shed the tail on island systems with the absence of terrestrial
predators. 相似文献
38.
Doreen Zegers Sigri Beckers Fenna de Freitas Armand V. Peeters Ilse L. Mertens Stijn L. Verhulst Raoul P. Rooman Jean‐Pierre Timmermans Kristine N. Desager Guy Massa Luc F. van Gaal Wim van Hul 《Obesity (Silver Spring, Md.)》2011,19(1):152-159
The melanocortin‐3 receptor (MC3R), a G‐protein‐coupled receptor expressed in the hypothalamus, is a key component of the leptin‐melanocortin pathway that regulates energy homeostasis. It is suggested that an MC3R defect leads to an increased feed efficiency, by which nutrients are partitioned preferentially into fat. In this study, we hypothesized that early‐onset obesity could be induced by mutations in MC3R. To investigate this hypothesis, we screened the entire coding region of the MC3R gene for mutations in obese subjects. A total of 404 overweight and obese children and adolescents, 86 severely obese adults (BMI ≥40 kg/m2), and 150 normal‐weight control adults were included. Besides three synonymous coding variations in the MC3R gene (S69S, L95L, I226I), we were able to identify three novel heterozygous, nonsynonymous, coding mutations (N128S, V211I, L299V) in three unrelated obese children. None of these mutations were found in any of the control subjects. Functional studies assessing localization and signaling properties of the mutant receptors provided proof for impaired function of the L299V mutated receptor, whereas no conclusive evidence for functional impairment of the N128S and V211I mutated receptors could be established. First, these results provide supporting evidence for a role of the MC3R gene in the pathogenesis of obesity in a small subset of patients. Second, they show that caution is called for the interpretation of newly discovered mutations in MC3R. 相似文献
39.
Expression of hemagglutinin esterase protein from recombinant mouse hepatitis virus enhances neurovirulence 总被引:2,自引:0,他引:2 下载免费PDF全文
Murine hepatitis virus (MHV) infection provides a model system for the study of hepatitis, acute encephalitis, and chronic demyelinating disease. The spike glycoprotein, S, which mediates receptor binding and membrane fusion, plays a critical role in MHV pathogenesis. However, viral proteins other than S also contribute to pathogenicity. The JHM strain of MHV is highly neurovirulent and expresses a second spike glycoprotein, the hemagglutinin esterase (HE), which is not produced by MHV-A59, a hepatotropic but only mildly neurovirulent strain. To investigate a possible role for HE in MHV-induced neurovirulence, isogenic recombinant MHV-A59 viruses were generated that produced either (i) the wild-type protein, (ii) an enzymatically inactive HE protein, or (iii) no HE at all (A. Lissenberg, M. M. Vrolijk, A. L. W. van Vliet, M. A. Langereis, J. D. F. de Groot-Mijnes, P. J. M. Rottier, and R. J. de Groot, J. Virol. 79:15054-15063, 2005 [accompanying paper]). A second, mirror set of recombinant viruses was constructed in which, in addition, the MHV-A59 S gene had been replaced with that from MHV-JHM. The expression of HE in combination with A59 S did not affect the tropism, pathogenicity, or spread of the virus in vivo. However, in combination with JHM S, the expression of HE, regardless of whether it retained esterase activity or not, resulted in increased viral spread within the central nervous system and in increased neurovirulence. Our findings suggest that the properties of S receptor utilization and/or fusogenicity mainly determine organ and host cell tropism but that HE enhances the efficiency of infection and promotes viral dissemination, at least in some tissues, presumably by serving as a second receptor-binding protein. 相似文献
40.
Gene expression programs during Brassica oleracea seed maturation, osmopriming, and germination are indicators of progression of the germination process and the stress tolerance level 总被引:1,自引:0,他引:1 下载免费PDF全文
Soeda Y Konings MC Vorst O van Houwelingen AM Stoopen GM Maliepaard CA Kodde J Bino RJ Groot SP van der Geest AH 《Plant physiology》2005,137(1):354-368
During seed maturation and germination, major changes in physiological status, gene expression, and metabolic events take place. Using chlorophyll sorting, osmopriming, and different drying regimes, Brassica oleracea seed lots of different maturity, stress tolerance, and germination behavior were created. Through careful physiological analysis of these seed lots combined with gene expression analysis using a dedicated cDNA microarray, gene expression could be correlated to physiological processes that occurred within the seeds. In addition, gene expression was studied during early stages of seed germination, prior to radicle emergence, since very little detailed information of gene expression during this process is available. During seed maturation expression of many known seed maturation genes, such as late-embryogenesis abundant or storage-compound genes, was high. Notably, a small but distinct subgroup of the maturation genes was found to correlate to seed stress tolerance in osmoprimed and dried seeds. Expression of these genes rapidly declined during priming and/or germination in water. The majority of the genes on the microarray were up-regulated during osmopriming and during germination on water, confirming the hypothesis that during osmopriming, germination-related processes are initiated. Finally, a large group of genes was up-regulated during germination on water, but not during osmopriming. These represent genes that are specific to germination in water. Germination-related gene expression was found to be partially reversible by physiological treatments such as slow drying of osmoprimed seeds. This correlated to the ability of seeds to withstand stress. 相似文献