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51.
Rosenfeld SS Xing J Jefferson GM Cheung HC King PH 《The Journal of biological chemistry》2002,277(39):36731-36739
A variety of models have recently emerged to explain how the molecular motor kinesin is able to maintain processive movement for over 100 steps. Although these models differ in significant features, they all predict that kinesin's catalytic domains intermittently separate from each other as the motor takes 8-nm steps along the microtubule. Furthermore, at some point in this process, one molecule of ATP is hydrolyzed per step. However, exactly when hydrolysis and product release occur in relation to this forward step have not been established. Furthermore, the rate at which this separation occurs as well as the speed of motor stepping onto and release from the microtubule have not been measured. In the absence of this information, it is difficult to critically evaluate competing models of kinesin function. We have addressed this issue by developing spectroscopic probes whose fluorescence is sensitive to motor-motor separation or microtubule binding. The kinetics of these fluorescence changes allow us to directly measure how fast kinesin steps onto and releases from the microtubule and provide insight into how processive movement is maintained by this motor. 相似文献
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In vitro generation of long-term repopulating hematopoietic stem cells by fibroblast growth factor-1
de Haan G Weersing E Dontje B van Os R Bystrykh LV Vellenga E Miller G 《Developmental cell》2003,4(2):241-251
The role of fibroblast growth factors and their receptors (FGFRs) in the regulation of normal hematopoietic stem cells is unknown. Here we show that, in mouse bone marrow, long-term repopulating stem cells are found exclusively in the FGFR(+) cell fraction. During differentiation toward committed progenitors, stem cells show loss of FGFR expression. Prolonged culture of bone marrow cells in serum-free medium supplemented with only FGF-1 resulted in robust expansion of multilineage, serially transplantable, long-term repopulating hematopoietic stem cells. Thus, we have identified a simple method of generating large numbers of rapidly engrafting stem cells that have not been genetically manipulated. Our results show that the multipotential properties of stem cells are dependent on signaling through FGF receptors and that FGF-1 plays an important role in hematopoietic stem cell homeostasis. 相似文献
54.
Cuenca AA Schetter A Aceto D Kemphues K Seydoux G 《Development (Cambridge, England)》2003,130(7):1255-1265
Polarization of the C. elegans zygote along the anterior-posterior axis depends on cortically enriched (PAR) and cytoplasmic (MEX-5/6) proteins, which function together to localize determinants (e.g. PIE-1) in response to a polarizing cue associated with the sperm asters. Using time-lapse microscopy and GFP fusions, we have analyzed the localization dynamics of PAR-2, PAR-6, MEX-5, MEX-6 and PIE-1 in wild-type and mutant embryos. These studies reveal that polarization involves two genetically and temporally distinct phases. During the first phase (establishment), the sperm asters at one end of the embryo exclude the PAR-3/PAR-6/PKC3 complex from the nearby cortex, allowing the ring finger protein PAR-2 to accumulate in an expanding 'posterior' domain. Onset of the establishment phase involves the non-muscle myosin NMY-2 and the 14-3-3 protein PAR-5. The kinase PAR-1 and the CCCH finger proteins MEX-5 and MEX-6 also function during the establishment phase in a feedback loop to regulate growth of the posterior domain. The second phase begins after pronuclear meeting, when the sperm asters begin to invade the anterior. During this phase (maintenance), PAR-2 maintains anterior-posterior polarity by excluding the PAR-3/PAR-6/PKC3 complex from the posterior. These findings provide a model for how PAR and MEX proteins convert a transient asymmetry into a stably polarized axis. 相似文献
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56.
Ugo Maninchedda Olivier M. Lepage Monika Gangl Sandrine Hilairet Bernard Remandet Francoise Meot Geraldine Penarier Emilie Segard Pierre Cortez Christian Jorgensen Régis Steinberg 《PloS one》2015,10(2)
The aim of this work was to develop an equine metacarpophalangeal joint model that induces osteoarthritis that is not primarily mediated by instability or inflammation. The study involved six Standardbred horses. Standardized cartilage surface damage or “grooves” were created arthroscopically on the distal dorsal aspect of the lateral and medial metacarpal condyles of a randomly chosen limb. The contralateral limb was sham operated. After 2 weeks of stall rest, horses were trotted 30 minutes every other day for 8 weeks, then evaluated for lameness and radiographed. Synovial fluid was analyzed for cytology and biomarkers. At 10 weeks post-surgery, horses were euthanized for macroscopic and histologic joint evaluation. Arthroscopic grooving allowed precise and identical damage to the cartilage of all animals. Under the controlled exercise regime, this osteoarthritis groove model displayed significant radiographic, macroscopic, and microscopic degenerative and reactive changes. Histology demonstrated consistent surgically induced grooves limited to non-calcified cartilage and accompanied by secondary adjacent cartilage lesions, chondrocyte necrosis, chondrocyte clusters, cartilage matrix softening, fissuring, mild subchondral bone inflammation, edema, and osteoblastic margination. Synovial fluid biochemistry and cytology demonstrated significantly elevated total protein without an increase in prostaglandin E2, neutrophils, or chondrocytes. This equine metacarpophalangeal groove model demonstrated that standardized non-calcified cartilage damage accompanied by exercise triggered altered osteochondral morphology and cartilage degeneration with minimal or inefficient repair and little inflammatory response. This model, if validated, would allow for assessment of disease processes and the effects of therapy. 相似文献
57.
Ana Freitas Ribeiro Alessandra Cristina Guedes Pellini Beatriz Yuko Kitagawa Daniel Marques Geraldine Madalosso Gerrita de Cassia Nogueira Figueira Jo?o Fred Ricardo Kerti Mangabeira Albernaz Telma Regina Marques Pinto Carvalhanas Dirce Maria Trevisan Zanetta 《PloS one》2015,10(3)
This case-control study aimed to assess the risk factors for death from influenza A(H1N1)pdm09 in patients with laboratory confirmation, who had severe acute respiratory illness-SARI and were hospitalized between June 28th and August 29th 2009, in the metropolitan regions of São Paulo and Campinas, Brazil. Medical charts of all the 193 patients who died (cases) and the 386 randomly selected patients who recovered (controls) were investigated in 177 hospitals. Household interviews were conducted with those who had survived and the closest relative of those who had died. 73.6% of cases and 38.1% of controls were at risk of developing influenza-related complications. The 18-to-59-year age group (OR = 2.31, 95%CI: 1.31–4.10 (reference up to 18 years of age)), presence of risk conditions for severity of influenza (OR = 1.99, 95%CI: 1.11–3.57, if one or OR = 6.05, 95%CI: 2.76–13.28, if more than one), obesity (OR = 2.73, 95%CI: 1.28–5.83), immunosuppression (OR = 3.43, 95%CI: 1.28–9.19), and search for previous care associated with the hospitalization (OR = 3.35, 95%CI: 1.75–6.40) were risk factors for death. Antiviral treatment performed within 72 hours of the onset of symptoms (OR = 0.17, 95%CI: 0.08–0.37, if within 48hours, and OR = 0.30, 95%CI: 0.11–0.81, if between 48 and 72 hours) was protective against death. The identification of high-risk patients and early treatment are important factors for reducing morbi-mortality from influenza. 相似文献
58.
59.
Guangxi Wu He Zhao Chenhao Li Menaka Priyadarsani Rajapakse Wing Cheong Wong Jun Xu Charles W. Saunders Nancy L. Reeder Raymond A. Reilman Annika Scheynius Sheng Sun Blake Robert Billmyre Wenjun Li Anna Floyd Averette Piotr Mieczkowski Joseph Heitman Bart Theelen Markus S. Schr?der Paola Florez De Sessions Geraldine Butler Sebastian Maurer-Stroh Teun Boekhout Niranjan Nagarajan Thomas L. Dawson Jr. 《PLoS genetics》2015,11(11)
Malassezia is a unique lipophilic genus in class Malasseziomycetes in Ustilaginomycotina, (Basidiomycota, fungi) that otherwise consists almost exclusively of plant pathogens. Malassezia are typically isolated from warm-blooded animals, are dominant members of the human skin mycobiome and are associated with common skin disorders. To characterize the genetic basis of the unique phenotypes of Malassezia spp., we sequenced the genomes of all 14 accepted species and used comparative genomics against a broad panel of fungal genomes to comprehensively identify distinct features that define the Malassezia gene repertoire: gene gain and loss; selection signatures; and lineage-specific gene family expansions. Our analysis revealed key gene gain events (64) with a single gene conserved across all Malassezia but absent in all other sequenced Basidiomycota. These likely horizontally transferred genes provide intriguing gain-of-function events and prime candidates to explain the emergence of Malassezia. A larger set of genes (741) were lost, with enrichment for glycosyl hydrolases and carbohydrate metabolism, concordant with adaptation to skin’s carbohydrate-deficient environment. Gene family analysis revealed extensive turnover and underlined the importance of secretory lipases, phospholipases, aspartyl proteases, and other peptidases. Combining genomic analysis with a re-evaluation of culture characteristics, we establish the likely lipid-dependence of all Malassezia. Our phylogenetic analysis sheds new light on the relationship between Malassezia and other members of Ustilaginomycotina, as well as phylogenetic lineages within the genus. Overall, our study provides a unique genomic resource for understanding Malassezia niche-specificity and potential virulence, as well as their abundance and distribution in the environment and on human skin. 相似文献
60.
Targeting Ergosterol Biosynthesis in Leishmania donovani: Essentiality of Sterol 14alpha-demethylase
Laura-Isobel McCall Amale El Aroussi Jun Yong Choi Debora F. Vieira Geraldine De Muylder Jonathan B. Johnston Steven Chen Danielle Kellar Jair L. Siqueira-Neto William R. Roush Larissa M. Podust James H. McKerrow 《PLoS neglected tropical diseases》2015,9(3)
Leishmania protozoan parasites (Trypanosomatidae family) are the causative agents of cutaneous, mucocutaneous and visceral leishmaniasis worldwide. While these diseases are associated with significant morbidity and mortality, there are few adequate treatments available. Sterol 14alpha-demethylase (CYP51) in the parasite sterol biosynthesis pathway has been the focus of considerable interest as a novel drug target in Leishmania. However, its essentiality in Leishmania donovani has yet to be determined. Here, we use a dual biological and pharmacological approach to demonstrate that CYP51 is indispensable in L. donovani. We show via a facilitated knockout approach that chromosomal CYP51 genes can only be knocked out in the presence of episomal complementation and that this episome cannot be lost from the parasite even under negative selection. In addition, we treated wild-type L. donovani and CYP51-deficient strains with 4-aminopyridyl-based inhibitors designed specifically for Trypanosoma cruzi CYP51. While potency was lower than in T. cruzi, these inhibitors had increased efficacy in parasites lacking a CYP51 allele compared to complemented parasites, indicating inhibition of parasite growth via a CYP51-specific mechanism and confirming essentiality of CYP51 in L. donovani. Overall, these results provide support for further development of CYP51 inhibitors for the treatment of visceral leishmaniasis. 相似文献