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71.
72.
Read TD Peterson SN Tourasse N Baillie LW Paulsen IT Nelson KE Tettelin H Fouts DE Eisen JA Gill SR Holtzapple EK Okstad OA Helgason E Rilstone J Wu M Kolonay JF Beanan MJ Dodson RJ Brinkac LM Gwinn M DeBoy RT Madpu R Daugherty SC Durkin AS Haft DH Nelson WC Peterson JD Pop M Khouri HM Radune D Benton JL Mahamoud Y Jiang L Hance IR Weidman JF Berry KJ Plaut RD Wolf AM Watkins KL Nierman WC Hazen A Cline R Redmond C Thwaite JE White O Salzberg SL Thomason B Friedlander AM Koehler TM Hanna PC 《Nature》2003,423(6935):81-86
Bacillus anthracis is an endospore-forming bacterium that causes inhalational anthrax. Key virulence genes are found on plasmids (extra-chromosomal, circular, double-stranded DNA molecules) pXO1 (ref. 2) and pXO2 (ref. 3). To identify additional genes that might contribute to virulence, we analysed the complete sequence of the chromosome of B. anthracis Ames (about 5.23 megabases). We found several chromosomally encoded proteins that may contribute to pathogenicity--including haemolysins, phospholipases and iron acquisition functions--and identified numerous surface proteins that might be important targets for vaccines and drugs. Almost all these putative chromosomal virulence and surface proteins have homologues in Bacillus cereus, highlighting the similarity of B. anthracis to near-neighbours that are not associated with anthrax. By performing a comparative genome hybridization of 19 B. cereus and Bacillus thuringiensis strains against a B. anthracis DNA microarray, we confirmed the general similarity of chromosomal genes among this group of close relatives. However, we found that the gene sequences of pXO1 and pXO2 were more variable between strains, suggesting plasmid mobility in the group. The complete sequence of B. anthracis is a step towards a better understanding of anthrax pathogenesis. 相似文献
73.
Genomic islands, such as pathogenicity islands, contribute to the evolution and diversification of microbial life. Here we report on the Widespread Colonization Island, which encompasses the tad (tight adherence) locus for colonization of surfaces and biofilm formation by the human pathogen Actinobacillus actinomycetemcomitans. At least 12 of the 14 genes at the tad locus are required for tenacious biofilm formation and synthesis of bundled Flp pili (fibrils) that mediate adherence. The pilin subunit, Flp1, remains inside the cell in tad-locus mutants, indicating that these genes encode a secretion system for export and assembly of fibrils. We found tad-related regions in a wide variety of Bacterial and Archaeal species, and their sequence characteristics indicate possible horizontal transfer. To test the hypothesis of horizontal transfer, we compared the phylogeny of the tad locus to a robust organismal phylogeny using statistical tests of congruence and tree reconciliation techniques. Our analysis strongly supports a complex history of gene shuffling by recombination and multiple horizontal transfers, duplications and losses. We present evidence for a specific horizontal transfer event leading to the establishment of this region as a determinant of disease. 相似文献
74.
Inada N Oguri M Pindor B Hennawi JF Chiu K Zheng W Ichikawa S Gregg MD Becker RH Suto Y Strauss MA Turner EL Keeton CR Annis J Castander FJ Eisenstein DJ Frieman JA Fukugita M Gunn JE Johnston DE Kent SM Nichol RC Richards GT Rix HW Sheldon ES Bahcall NA Brinkmann J Ivezić Z Lamb DQ McKay TA Schneider DP York DG 《Nature》2003,426(6968):810-812
Gravitational lensing is a powerful tool for the study of the distribution of dark matter in the Universe. The cold-dark-matter model of the formation of large-scale structures (that is, clusters of galaxies and even larger assemblies) predicts the existence of quasars gravitationally lensed by concentrations of dark matter so massive that the quasar images would be split by over 7 arcsec. Numerous searches for large-separation lensed quasars have, however, been unsuccessful. All of the roughly 70 lensed quasars known, including the first lensed quasar discovered, have smaller separations that can be explained in terms of galaxy-scale concentrations of baryonic matter. Although gravitationally lensed galaxies with large separations are known, quasars are more useful cosmological probes because of the simplicity of the resulting lens systems. Here we report the discovery of a lensed quasar, SDSS J1004 + 4112, which has a maximum separation between the components of 14.62 arcsec. Such a large separation means that the lensing object must be dominated by dark matter. Our results are fully consistent with theoretical expectations based on the cold-dark-matter model. 相似文献
75.
Daniel S. Yeung Wing W. Y. Ng Aki P. F. Chan Patrick P. K. Chan Michael Firth Eric C. C. Tsang 《系统科学与系统工程学报(英文版)》2007,16(2):166-180
Company bankruptcies cost billions of dollars in losses to banks each year. Thus credit risk prediction is a critical part of a bank's loan approval decision process. Traditional financial models for credit risk prediction are no longer adequate for describing today's complex relationship between the financial health and potential bankruptcy of a company. In this work, a multiple classifier system (embedded in a multiple intelligent agent system) is proposed to predict the financial health of a company. In our model, each individual agent (classifier) makes a prediction on the likelihood of credit risk based on only partial information of the company. Each of the agents is an expert, but has limited knowledge (represented by features) about the company. The decisions of all agents are combined together to form a final credit risk prediction. Experiments show that our model out-performs other existing methods using the benchmarking Compustat American Corporations dataset. 相似文献
76.
Iverson RM Dzurisin D Gardner CA Gerlach TM LaHusen RG Lisowski M Major JJ Malone SD Messerich JA Moran SC Pallister JS Qamar AI Schilling SP Vallance JW 《Nature》2006,444(7118):439-443
The 2004-05 eruption of Mount St Helens exhibited sustained, near-equilibrium behaviour characterized by relatively steady extrusion of a solid dacite plug and nearly periodic shallow earthquakes. Here we present a diverse data set to support our hypothesis that these earthquakes resulted from stick-slip motion along the margins of the plug as it was forced incrementally upwards by ascending, solidifying, gas-poor magma. We formalize this hypothesis with a dynamical model that reveals a strong analogy between behaviour of the magma-plug system and that of a variably damped oscillator. Modelled stick-slip oscillations have properties that help constrain the balance of forces governing the earthquakes and eruption, and they imply that magma pressure never deviated much from the steady equilibrium pressure. We infer that the volcano was probably poised in a near-eruptive equilibrium state long before the onset of the 2004-05 eruption. 相似文献
77.
78.
Rasmussen SG Choi HJ Fung JJ Pardon E Casarosa P Chae PS Devree BT Rosenbaum DM Thian FS Kobilka TS Schnapp A Konetzki I Sunahara RK Gellman SH Pautsch A Steyaert J Weis WI Kobilka BK 《Nature》2011,469(7329):175-180
G protein coupled receptors (GPCRs) exhibit a spectrum of functional behaviours in response to natural and synthetic ligands. Recent crystal structures provide insights into inactive states of several GPCRs. Efforts to obtain an agonist-bound active-state GPCR structure have proven difficult due to the inherent instability of this state in the absence of a G protein. We generated a camelid antibody fragment (nanobody) to the human β(2) adrenergic receptor (β(2)AR) that exhibits G protein-like behaviour, and obtained an agonist-bound, active-state crystal structure of the receptor-nanobody complex. Comparison with the inactive β(2)AR structure reveals subtle changes in the binding pocket; however, these small changes are associated with an 11?? outward movement of the cytoplasmic end of transmembrane segment 6, and rearrangements of transmembrane segments 5 and 7 that are remarkably similar to those observed in opsin, an active form of rhodopsin. This structure provides insights into the process of agonist binding and activation. 相似文献
79.
Genome sequence and analysis of the tuber crop potato 总被引:11,自引:0,他引:11
Potato Genome Sequencing Consortium Xu X Pan S Cheng S Zhang B Mu D Ni P Zhang G Yang S Li R Wang J Orjeda G Guzman F Torres M Lozano R Ponce O Martinez D De la Cruz G Chakrabarti SK Patil VU Skryabin KG Kuznetsov BB Ravin NV Kolganova TV Beletsky AV Mardanov AV Di Genova A Bolser DM Martin DM Li G Yang Y Kuang H Hu Q Xiong X Bishop GJ Sagredo B Mejía N Zagorski W Gromadka R Gawor J Szczesny P Huang S Zhang Z Liang C He J Li Y He Y Xu J Zhang Y Xie B Du Y Qu D Bonierbale M Ghislain M 《Nature》2011,475(7355):189-195
Potato (Solanum tuberosum L.) is the world's most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop. 相似文献
80.