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991.
992.
J. H. D. Millar K. B. Fraser Margaret Haire J. H. Connolly P. V. Shirodaria Diana S. M. Hadden 《BMJ (Clinical research ed.)》1971,2(5758):378-380
Sera from 43 patients with multiple sclerosis were tested by immunofluorescence. Sera from patients with active multiple sclerosis included four with measles virus-specific immunoglobulin M (measles IgM) and two with mumps virus-specific IgM (mumps IgM). In one case each mumps IgM and measles IgM seem to have persisted for two and a half years and three years respectively. In a comparable group of 43 patients with other nervous diseases measles IgM was found in only one serum, and among 43 normal patients no measles or mumps IgM was found.Herpes simplex virus-specific IgM (herpes simplex IgM) was distributed among all three groups. Anticellular IgM was also found, predominantly in active multiple sclerosis, and persisted in two sera for two and a half years. 相似文献
993.
Northern elephant seals were hunted to near extinction in the 19th century, yet have recovered remarkably and now number around 175,000. We surveyed 110 seals for single-strand conformation polymorphism (SSCP) and sequence variation at three major histocompatibility (MHC) class II loci (DQA, DQB and DRB) to evaluate the genetic consequences of the population bottleneck at these loci vs. other well-studied genes. We found very few alleles at each MHC locus, significant variation among breeding sites for the DQA locus, and linkage disequilibrium between the DQB and DRB loci. Northern elephant seals are evidently inbred, although there is as yet no evidence of correlative reductions in fitness. 相似文献
994.
Sarah L. Bush Diana J. Bell 《Ethology : formerly Zeitschrift fur Tierpsychologie》1997,103(4):292-303
The courtship and mating behaviour of A. muletensis are described based on observations of captive toads. Courtship is prolonged and complex, with both sexes participating actively. Either sex can escape from amplexus and may do so if the partner fails to respond appropriately to courtship manocuvres. Females control the pace and duration of courtship. Females unable to obtain a mate drop their eggs unfertilized. Both sexes produce courtship vocalizations and either sex may initiate courtship, although females were observed to do so only when they were in danger of dropping their eggs. Physical competition in the form of interference and grappling may occur between either males or females, but was observed more frequently between females. The active role played by females during courtship in this species is discussed with regard to sex-role reversal theory and opportunities for mate choice. 相似文献
995.
Chee MJ Mörl K Lindner D Merten N Zamponi GW Light PE Beck-Sickinger AG Colmers WF 《The Journal of biological chemistry》2008,283(48):33337-33346
Constitutively active G-protein-coupled receptors (GPCRs) can signal even in the absence of ligand binding. Most Class I GPCRs are stabilized in the resting conformation by intramolecular interactions involving transmembrane domain (TM) 3 and TM6, particularly at loci 6.30 and 6.34 of TM6. Signaling by Gi/Go-coupled receptors such as the Neuropeptide Y1 receptor decreases already low basal metabolite levels. Thus, we examined constitutive activity using a biochemical assay mediated by a Gi/Gq chimeric protein and a more direct electrophysiological assay. Wild-type (WT-Y1) receptors express no measurable, agonist-independent activation, while mu-opioid receptors (MOR) and P2Y12 purinoceptors showed clear evidence of constitutive activation, especially in the electrophysiological assay. Neither point mutations at TM6 (T6.30A or N6.34A) nor substitution of the entire TM3 and TM6 regions from the MOR into the Y1 receptor increased basal WT-Y1 activation. By contrast, chimeric substitution of the third intracellular loop (ICL3) generated a constitutively active, Y1-ICL3-MOR chimera. Furthermore, the loss of stabilizing interactions from the native ICL3 enhanced the role of surrounding residues to permit basal receptor activation; because constitutive activity of the Y1-ICL3-MOR chimera was further increased by point mutation at locus 6.34, which did not alter WT-Y1 receptor activity. Our results indicate that the ICL3 stabilizes the Y1 receptor in the inactive state and confers structural properties critical for regulating Y receptor activation and signal transduction. These studies reveal the active participation of the ICL3 in the stabilization and activation of Class I GPCRs. 相似文献
996.
Diana?Negr?o?Cavalcanti Meire-Anne?Rezende?de?Oliveira Joel?Campos?De-Paula Leandro?Silva?Barbosa Tamara?Fogel Marcelo?Alves?Pinto Izabel?Christina?Nunes?de?Palmer Paix?o Valéria?Laneuville?TeixeiraEmail author 《Journal of applied phycology》2011,23(5):873-876
This study evaluated the variability in the production of an HIV-1 antiviral diterpene in individuals of Dictyota menstrualis throughout reproductive stages. The brown alga Dictyota has an isomorphic biphasic life cycle. The quantification of the active principle by GC–FID indicated a greater production
of the diterpene in the female gametophytic phase (42.11 ppm). However, these individuals had the highest variation between
individuals (standard deviation of 68.20 ppm in the range from 0.39 to 227 ppm). Sporophytic individuals showed less variability.
This variability in the production of the antiviral diterpene is important to the development of future antiviral drugs. 相似文献
997.
Tianjun Zhou Oleg Kurnasov Diana R Tomchick Derk D Binns Nick V Grishin Victor E Marquez Andrei L Osterman Hong Zhang 《The Journal of biological chemistry》2002,277(15):13148-13154
Nicotinamide/nicotinate mononucleotide (NMN/ NaMN)adenylyltransferase (NMNAT) is an indispensable enzyme in the biosynthesis of NAD(+) and NADP(+). Human NMNAT displays unique dual substrate specificity toward both NMN and NaMN, thus flexible in participating in both de novo and salvage pathways of NAD synthesis. Human NMNAT also catalyzes the rate-limiting step of the metabolic conversion of the anticancer agent tiazofurin to its active form tiazofurin adenine dinucleotide (TAD). The tiazofurin resistance is mainly associated with the low NMNAT activity in the cell. We have solved the crystal structures of human NMNAT in complex with NAD, deamido-NAD, and a non-hydrolyzable TAD analogue beta-CH(2)-TAD. These complex structures delineate the broad substrate specificity of the enzyme toward both NMN and NaMN and reveal the structural mechanism for adenylation of tiazofurin nucleotide. The crystal structure of human NMNAT also shows that it forms a barrel-like hexamer with the predicted nuclear localization signal sequence located on the outside surface of the barrel, supporting its functional role of interacting with the nuclear transporting proteins. The results from the analytical ultracentrifugation studies are consistent with the formation of a hexamer in solution under certain conditions. 相似文献
998.
The Drosophila kinesin-like protein KLP67A is essential for mitotic and male meiotic spindle assembly 下载免费PDF全文
Gandhi R Bonaccorsi S Wentworth D Doxsey S Gatti M Pereira A 《Molecular biology of the cell》2004,15(1):121-131
We have performed a mutational analysis together with RNA interference to determine the role of the kinesin-like protein KLP67A in Drosophila cell division. During both mitosis and male meiosis, Klp67A mutations cause an increase in MT length and disrupt discrete aspects of spindle assembly, as well as cytokinesis. Mutant cells exhibit greatly enlarged metaphase spindle as a result of excessive MT polymerization. The analysis of both living and fixed cells also shows perturbations in centrosome separation, chromosome segregation, and central spindle assembly. These data demonstrate that the MT plus end-directed motor KLP67A is essential for spindle assembly during mitosis and male meiosis and suggest that the regulation of MT plus-end polymerization is a key determinant of spindle architecture throughout cell division. 相似文献
999.
Peter Schmidt Diana Lindner Cindy Montag Sandra Berndt Annette G. Beck‐Sickinger Rainer Rudolph Daniel Huster 《Biotechnology progress》2009,25(6):1732-1739
G protein‐coupled receptors (GPCRs) are a class of membrane proteins that represent a major target for pharmacological developments. However, there is still little knowledge about GPCR structure and dynamics since high‐level expression and characterization of active GPCRs in vitro is extremely complicated. Here, we describe the recombinant expression and functional folding of the human Y2 receptor from inclusion bodies of E. coli cultures. Milligram protein quantities were produced using high density fermentation and isolated in a single step purification with a yield of over 20 mg/L culture. Extensive studies were carried out on in vitro refolding and stabilization of the isolated receptor in detergent solution. The specific binding of the ligand, the 36 residue neuropeptide Y (NPY), to the recombinant Y2 receptors in micellar form was shown by several radioligand affinity assays. In competition experiments, an IC50 value in low nanomolar range could be determined. Further, a KD value of 1.9 nM was determined from a saturation assay, where NPY was titrated to the recombinant Y2 receptors. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 相似文献
1000.