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11.
12.
Tibor Braun 《中国科学基金(英文版)》2005,13(1):64-72
IntroductionThere arc many proofs indicating that economicgrowth in the modern era has been grounded on theexploitation of scientific knowledge. The sphere ofhuman activities, which can be identified as "The Re-public of Science" has grown too important for therest of society to leave alone. Most of the industrialnations and many among the LDC's acknowledge thistoday, and virtually all societies in which modern sci-ence is practiced pay at least lip service to the beliefthat it is important … 相似文献
13.
Endotoxin-enhanced host resistance: reversal by kinetin riboside 总被引:2,自引:0,他引:2
14.
J P Braun A Rico P Bernard 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(20):1483-1485
In the Mouse, gamma-glutamyl transferase distribution changes with development in the kidney and the liver; on the contrary, its activity remains almost equal and low in other organs. In the liver, a low activity is observed in the fetus and the new-born up to the 3rd day of life; then it is no more measurable. In the kidney, the low enzyme activity of the fetus is multiplied by 10 in the 10 first days of life and by 50 in the 6 first weeks. 相似文献
15.
16.
Packaging paternal chromosomes with protamine 总被引:1,自引:0,他引:1
Braun RE 《Nature genetics》2001,28(1):10-12
17.
Ascaris haemoglobin is a nitric oxide-activated 'deoxygenase'. 总被引:5,自引:0,他引:5
D M Minning A J Gow J Bonaventura R Braun M Dewhirst D E Goldberg J S Stamler 《Nature》1999,401(6752):497-502
The parasitic nematode Ascaris lumbricoides infects one billion people worldwide. Its perienteric fluid contains an octameric haemoglobin that binds oxygen nearly 25,000 times more tightly than does human haemoglobin. Despite numerous investigations, the biological function of this molecule has remained elusive. The distal haem pocket contains a metal, oxygen and thiol, all of which are known to be reactive with nitric oxide. Here we show that Ascaris haemoglobin enzymatically consumes oxygen in a reaction driven by nitric oxide, thus keeping the perienteric fluid hypoxic. The mechanism of this reaction involves unprecedented chemistry of a haem group, a thiol and nitric oxide. We propose that Ascaris haemoglobin functions as a 'deoxygenase', using nitric oxide to detoxify oxygen. The structural and functional adaptations of Ascaris haemoglobin suggest that the molecular evolution of haemoglobin can be rationalized by its nitric oxide related functions. 相似文献
18.
Aharonian F Akhperjanian AG Bazer-Bachi AR Beilicke M Benbow W Berge D Bernlöhr K Boisson C Bolz O Borrel V Braun I Breitling F Brown AM Chadwick PM Chounet LM Cornils R Costamante L Degrange B Dickinson HJ Djannati-Ataï A Drury LO Dubus G Emmanoulopoulos D Espigat P Feinstein F Fontaine G Fuchs Y Funk S Gallant YA Giebels B Gillessen S Glicenstein JF Goret P Hadjichristidis C Hauser D Hauser M Heinzelmann G Henri G Hermann G Hinton JA Hofmann W Holleran M Horns D Jacholkowska A de Jager OC 《Nature》2006,439(7077):695-698
The source of Galactic cosmic rays (with energies up to 10(15) eV) remains unclear, although it is widely believed that they originate in the shock waves of expanding supernova remnants. At present the best way to investigate their acceleration and propagation is by observing the gamma-rays produced when cosmic rays interact with interstellar gas. Here we report observations of an extended region of very-high-energy (> 10(11) eV) gamma-ray emission correlated spatially with a complex of giant molecular clouds in the central 200 parsecs of the Milky Way. The hardness of the gamma-ray spectrum and the conditions in those molecular clouds indicate that the cosmic rays giving rise to the gamma-rays are likely to be protons and nuclei rather than electrons. The energy associated with the cosmic rays could have come from a single supernova explosion around 10(4) years ago. 相似文献
19.
Mayer K Schüller C Wambutt R Murphy G Volckaert G Pohl T Düsterhöft A Stiekema W Entian KD Terryn N Harris B Ansorge W Brandt P Grivell L Rieger M Weichselgartner M de Simone V Obermaier B Mache R Müller M Kreis M Delseny M Puigdomenech P Watson M Schmidtheini T Reichert B Portatelle D Perez-Alonso M Boutry M Bancroft I Vos P Hoheisel J Zimmermann W Wedler H Ridley P Langham SA McCullagh B Bilham L Robben J Van der Schueren J Grymonprez B Chuang YJ Vandenbussche F Braeken M Weltjens I Voet M 《Nature》1999,402(6763):769-777
The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency of a variety of repeats, new repeats, reduced recombination, lowered gene density and lowered gene expression. Roughly 60% of the predicted protein-coding genes have been functionally characterized on the basis of their homology to known genes. Many genes encode predicted proteins that are homologous to human and Caenorhabditis elegans proteins. 相似文献
20.
During vertebrate embryogenesis, myogenic precursor cells of limb muscles delaminate from the ventro-lateral edge of the somitic dermomyotome and migrate to the limb buds, where they congregate into dorsal and ventral muscle masses. It has been proposed that the surrounding connective tissue controls muscle pattern formation in limbs. Regulatory molecules such as receptor tyrosine kinases like c-Met ( ref. 6) and those encoded by homeobox-containing genes, including c-Met (ref. 6), Tbx1 (ref. 7), Mox2 (ref. 8), Six1 and Six2 (ref. 9), Pitx2, Pax3 (refs 10,11) and Lbx1h (refs 12,13), are expressed in migrating limb precursor cells. The role of these genes in the patterning of limb muscles is unknown, although mutation of Pax3 or Met causes disruption of limb muscle development at an initial step, disturbing the epithelial-to-mesenchymal transition of the somitic epithelium. No limb muscle cells form in these mutants, and the early loss of myogenic precursor cells prevented an analysis of later functions of these genes during limb muscle development. Based on quail-chick chimaera studies, it was assumed that a cell-autonomous contribution of myogenic cells to the formation of individual limb muscles is negligible, and that an instructive role of limb mesenchyme is critical in this process. Here we show that Lbx1h determines migratory routes of muscle precursor cells in a cell-autonomous manner, thereby leading to the formation of distinct limb muscle patterns. Inactivation of Lbx1h, which is specifically expressed in migrating muscle precursor cells, led to a lack of extensor muscles in forelimbs and an absence of muscles in hindlimbs. The defect was caused by the failure of all muscle precursor cells of hindlimbs and of precursor cells of extensor muscles of forelimbs to migrate to their corresponding muscle anlagen. Our results demonstrate that Lbx1h is a key regulator of muscle precursor cell migration and is required for the acquisition of dorsal identities of forelimb muscles. 相似文献