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131.
Illumination causes an uptake of oxygen by isolated chromatophores of purple and green bacteria incubated with electron donors. Photooxidase activity of Rhodospirillum rubrum, Chromatium minutissimum, Rhodopseudomonas sphaeroides and Thiocapsa roseopersicina chromatophores is sensitive, and photooxidase activity of Ectothiorhodospira shaposhnikovii and Chlorobium limicola f. thiosulfatophilum is resistant to o-phenanthroline. O2 uptake by illuminated chromatophores of R. rubrum and C. limicola is stimulated upon the increase of pH of incubation mixture from 5 to 9. Photooxidase activity is also manifested in the intact bacterial cells and not merely in the isolated chromatophores. O2 uptake by the illuminated R. rubrum cells treated with CN- is stimulated by 2-heptyl-4-hydroxyquinoline-N-oxide and a protonophorous uncoupler. The interaction of the photosynthetic and respiratory systems of the electron transfer in the bacterial cells and the probable causes of the strong anaerobic way of life of the green sulfur bacteria are discussed.HQNO
2-heptyl-4-hydroxyquinoline-N-oxide
- TMPD
N,N,-N,N-tetramethyl-p-phenylenediamine 相似文献
132.
Arunkumar AI Klimovich V Jiang X Ott RD Mizoue L Fanning E Chazin WJ 《Nature structural & molecular biology》2005,12(4):332-339
Simian virus 40 (SV40) provides a model system for the study of eukaryotic DNA replication, in which the viral protein, large T antigen (Tag), marshals human proteins to replicate the viral minichromosome. SV40 replication requires interaction of Tag with the host single-stranded DNA-binding protein, replication protein A (hRPA). The C-terminal domain of the hRPA32 subunit (RPA32C) facilitates initiation of replication, but whether it interacts with Tag is not known. Affinity chromatography and NMR revealed physical interaction between hRPA32C and the Tag origin DNA-binding domain, and a structural model of the complex was determined. Point mutations were then designed to reverse charges in the binding sites, resulting in substantially reduced binding affinity. Corresponding mutations introduced into intact hRPA impaired initiation of replication and primosome activity, implying that this interaction has a critical role in assembly and progression of the SV40 replisome. 相似文献
133.
Chromosomal data have been underutilized in phylogenetic investigations despite the obvious potential that cytogenetic studies have to reveal both structural and functional homologies among taxa. In large part this is associated with difficulties in scoring conventional and molecular cytogenetic information for phylogenetic analysis. The manner in which chromosomal data have been used by most authors in the past was often conceptionally flawed in terms of the methods and principles underpinning modern cladistics. We present herein a review of the different methods employed, examine their relative strengths, and then outline a simple approach that considers the chromosomal change as the character, and its presence or absence the character state. We test this using one simulated and several empirical data sets. Features that are unique to cytogenetic investigations, including B-chromosomes, heterochromatic additions/deletions, and the location and number of nucleolar organizer regions (NORs), as well as the weighting of chromosomal characters, are critically discussed with regard to their suitability for phylogenetic reconstruction. We conclude that each of these classes of data have inherent problems that limit their usefulness in phylogenetic analyses and in most of these instances, inclusion should be subject to rigorous appraisal that addresses the criterion of unequivocal homology. 相似文献
134.
135.
Yuan YR Pei Y Ma JB Kuryavyi V Zhadina M Meister G Chen HY Dauter Z Tuschl T Patel DJ 《Molecular cell》2005,19(3):405-419
Argonaute (Ago) proteins constitute a key component of the RNA-induced silencing complex (RISC). We report the crystal structure of Aquifex aeolicus Ago (Aa-Ago) together with binding and cleavage studies, which establish this eubacterial Ago as a bona fide guide DNA strand-mediated site-specific RNA endonuclease. We have generated a stereochemically robust model of the complex, where the guide DNA-mRNA duplex is positioned within a basic channel spanning the bilobal interface, such that the 5' phosphate of the guide strand can be anchored in a basic pocket, and the mRNA can be positioned for site-specific cleavage by RNase H-type divalent cation-coordinated catalytic Asp residues of the PIWI domain. Domain swap experiments involving chimeras of human Ago (hAgo1) and cleavage-competent hAgo2 reinforce the role of the PIWI domain in "slicer" activity. We propose a four-step Ago-mediated catalytic cleavage cycle model, which provides distinct perspectives into the mechanism of guide strand-mediated mRNA cleavage within the RISC. 相似文献
136.
Vitaly?SchetininEmail author Joachim?SchultEmail author 《Theorie in den Biowissenschaften》2005,124(1):151-53
A new technique is presented developed to learn multi-class concepts from clinical electroencephalograms (EEGs). A desired
concept is represented as a neuronal computational model consisting of the input, hidden, and output neurons. In this model
the hidden neurons learn independently to classify the EEG segments presented by spectral and statistical features. This technique
has been applied to the EEG data recorded from 65 sleeping healthy newborns in order to learn a brain maturation concept of
newborns aged between 35 and 51 weeks. The 39,399 and 19,670 segments from these data have been used for learning and testing
the concept, respectively. As a result, the concept has correctly classified 80.1% of the testing segments or 87.7% of the
65 records. 相似文献
137.
138.
Cell-to-cell tobacco mosaic virus movement protein (TMV MP) mediates viral spread between the host cells through plasmodesmata. Although several host factors have been shown to interact with TMV MP, none of them coresides with TMV MP within plasmodesmata. We used affinity purification to isolate a tobacco protein that binds TMV MP and identified it as calreticulin. The interaction between TMV MP and calreticulin was confirmed in vivo and in vitro, and both proteins were shown to share a similar pattern of subcellular localization to plasmodesmata. Elevation of the intracellular levels of calreticulin severely interfered with plasmodesmal targeting of TMV MP, which, instead, was redirected to the microtubular network. Furthermore, in TMV-infected plant tissues overexpressing calreticulin, the inability of TMV MP to reach plasmodesmata substantially impaired cell-to-cell movement of the virus. Collectively, these observations suggest a functional relationship between calreticulin, TMV MP, and viral cell-to-cell movement. 相似文献
139.
The present study set out to elucidate the structure and function of the large subcuticular air sacs encountered in the gaster
of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae). Gastral segments I, II, III, together with the anterior portion of segment IV, comprise the greater
volume of the gaster, and inside them, beneath the cuticle, are contained not only structures that extend throughout their
entire length, like the alimentary canal, and the nerve cord with its paired abdominal ganglia, situated near the cuticle
in the ventral side, but also the heart, which is actually a muscular and dorsally located blood vessel that pumps blood anteriorly,
toward the head of the hornet. The mentioned structures take up only a small volume of the gaster, while the rest is occupied
by air sacs and tracheal ducts that also extend longitudinally. Interposed between the two air sacs, there is a hard partition
and above it, at the center – a paired tracheal duct that extends the entire length of the air sacs. The endothelium of the
air sacs is very anfractuous, thereby enlarging and strengthening the surface area. In each gastral segment there is an aperture
for the entry of air, namely, a spiracle. Additionally, in each segment, in the antero-lateral aspect of its tergum and situated between two successive
segments, there is an intersegmental conjunctive bearing parallel slits of 1–2 microM in width and 10–30 microM in length.
The latter are arranged concentrically around bundles of tracheae that traverse the cuticle from segment to segment. From
the upper rims of the slits are suspended downward fringe-like structures or "shutters" ranging between 3–10 microM in length.
We discuss the possibility that the Oriental hornet resorts to internal circulation of air, along with a thermoelectric heat
pump mechanism, in order to achieve cooling and thermoregulation of its body. 相似文献
140.
Research suggests that fibromyalgia is a central, widespread pain syndrome supported by a generalized disturbance in central nervous system pain processing. Over the past decades, multiple lines of research have identified the locus for many functional, chronic pain disorders to the central nervous system, and the brain. In recent years, brain neuroimaging techniques have heralded a revolution in our understanding of chronic pain, as they have allowed researchers to non-invasively (or minimally invasively) evaluate human patients suffering from various pain disorders. While many neuroimaging techniques have been developed, growing interest in two specific imaging modalities has led to significant contributions to chronic pain research. For instance, resting functional connectivity magnetic resonance imaging (fcMRI) is a recent adaptation of fMRI that examines intrinsic brain connectivity - defined as synchronous oscillations of the fMRI signal that occurs in the resting basal state. Proton magnetic resonance spectroscopy (1H-MRS) is a non-invasive magnetic resonance imaging technique that can quantify the concentration of multiple metabolites within the human brain. This review will outline recent applications of the complementary imaging techniques - fcMRI and 1H-MRS - to improve our understanding of fibromyalgia pathophysiology and how pharmacological and non-pharmacological therapies contribute to analgesia in these patients. A better understanding of the brain in chronic pain, with specific linkage as to which neural processes relate to spontaneous pain perception and hyperalgesia, will greatly improve our ability to develop novel therapeutics. Neuroimaging will play a growing role in the translational research approaches needed to make this a reality. 相似文献