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991.
Graham WA Ludlage E Mansfield K Magill D Nesathurai S 《Journal of medical primatology》2006,35(1):25-29
BACKGROUND: The aim of this study was to test the feasibility of using the tail of Macaca mulatta for neurophysiological testing of the peripheral nervous system. METHODS: Motor and sensory nerve conduction studies (NCS) of the tail were obtained by surface stimulation and recording. The technique utilized was novel. Unlike other NCS obtained from other peripheral nerves, this technique did not require any special neurophysiological expertise. RESULTS: The latency of the motor and sensory response was 2.5 +/- 0.71 and 1.1 +/- 0.27 ms respectively. The amplitude of the motor and sensory response was 8.1 +/- 5.1 mV and 14.6 +/- 9.4 microV respectively. Similar to human beings, there was a statistically significant relationship between age and motor amplitude, motor latency and sensory latency. CONCLUSIONS: Based on our results, a relatively simple, reproducible neurophysiological monitoring technique of the peripheral nervous system is possible. 相似文献
992.
Crawford GC Ziccardi MH Gonzales BJ Woods LM Fischer JK Manning EJ Mazet JA 《Journal of wildlife diseases》2006,42(4):715-723
Between 2 August and 22 September 2000, 37 hunter-killed tule elk (Cervus elaphus nannodes) were evaluated at the Grizzly Island Wildlife Area, California, USA, for evidence of paratuberculosis. Elk were examined post-mortem, and tissue and fecal samples were submitted for radiometric mycobacterial culture. Acid-fast isolates were identified by a multiplex polymerase chain reaction (PCR) that discriminates among members of the Mycobacterium avium complex (MAC). Histopathologic evaluations were completed, and animals were tested for antibodies using a Johne's enzyme-linked immunosorbent assay (ELISA) and agar gel immunodiffusion. In addition, 104 fecal samples from tule elk remaining in the herd were collected from the ground and submitted for radiometric mycobacterial culture. No gross lesions were detected in any of the hunter-killed animals. Mycobacterium avium subsp. paratuberculosis (MAP) was cultured once from ileocecal tissue of one adult elk and was determined to be a strain (A18) found commonly in infected cattle. One or more isolates of Mycobacterium avium subsp. avium (MAA) were isolated from tissues of five additional adult elk. Gastrointestinal tract and lymph node tissues from 17 of the 37 elk (46%) examined had histopathologic lesions commonly seen with mycobacterial infection; however, acid-fast bacteria were not observed. All MAC infections were detected from adult elk (P = 0.023). In adult elk, a statistically significant association was found between MAA infection and ELISA sample-to-positive ratio (S/P) > or = 0.25 (P=0.021); four of five MAA culture-positive elk tested positive by ELISA. Sensitivity and specificity of ELISA S/P > or = 0.25 for detection of MAA in adult elk were 50% and 93%, respectively. No significant associations were found between MAC infection and sex or histopathologic lesions. Bacteriologic culture confirmed infection with MAP and MAA in this asymptomatic tule elk herd. The Johne's ELISA was useful in signaling mycobacterial infection on a population basis but could not discriminate between MAA and MAP antibodies. The multiplex PCR was useful in discriminating among the closely related species belonging to MAC. 相似文献
993.
994.
Continuous Plankton Recorder flow rates revisited: clogging, ship speed and flow meter design 总被引:1,自引:0,他引:1
The factors affecting the volume of water filtered by a TypeII Mark III Continuous Plankton Recorder (CPR) were investigatedin eastern Antarctica in February/March 2003. Three tows wereconducted, one each using 270-, 224- and 125-µm nylonmesh. Volume filtered was measured at 3-s intervals with a Valeportelectromagnetic flow meter, while ship speed, photosyntheticallyactive radiation (PAR) and fluorescence were measured everyminute. Substantial variation in measured volume filtered (MVF)was recorded on each transect. Ship speed was positively correlatedwith MVF and caused up to 30% reductions in MVF while clogging,predominantly by phytoplankton, resulted in up to 60% reductionsin MVF. A maximum 78% reduction in MVF resulted from the combinedeffects of clogging and ship speed. The substantial impact ofclogging on observed zooplankton densities highlights the needfor flow meter measurements to quantify CPR data. However, observationsfrom this study show that the CPR flow meter currently in usemay itself have caused the positive correlation between MVFand ship speed, indicating the need for improved flow meterdesign. Continuing miniaturization and improved resolution ofdistance loggers for attachment to marine vertebrate predatorsholds promise in this area. 相似文献
995.
Modelling the role of intracolonial genetic diversity on regulation of brood temperature in honey bee (Apis mellifera L.) colonies 总被引:2,自引:0,他引:2
In polyandrous social insects such as honey bees, a worker’s affinity for a particular task may be genetically infl uenced
and so some patrilines may have lower stimulus thresholds for commencing a task than others. We used simulation models to
investigate the effects of intracolonial diversity in the task thresholds that stimulate workers to engage in heating and
cooling during nest thermoregulation. First, we simulated colonies comprised of one or 15 patrilines that were engaged in
heating the brood nest, and observed that single patriline colonies maintained, on average, less stable brood nest temperatures
than multiple patriline colonies. Second we simulated colonies with five patrilines that were engaged in cooling their nest,
recording the proportions of bees of different patrilines that engaged in nest cooling in response to changing temperatures.
Both of our simulations show remarkably similar qualitative patterns to those that we have previously observed empirically.
This provides further support for the hypothesis that geneticallybased variability in task thresholds among patrilines within
honey bee colonies is an important contributor to the ability of colonies to precisely thermoregulate their nests, and we
suggest that diversity is important for optimal expression of a range of other colony-level phenotypes.
Received 17 June 2005; revised 27 October 2005; accepted 23 December 2005. 相似文献
996.
De Smet L Savvides SN Van Horen E Pettigrew G Van Beeumen JJ 《The Journal of biological chemistry》2006,281(7):4371-4379
Cytochrome c peroxidases (CCP) play a key role in cellular detoxification by catalyzing the reduction of hydrogen peroxide to water. The di-heme CCP from Rhodobacter capsulatus is the fastest enzyme (1060 s(-1)), when tested with its physiological cytochrome c substrate, among all di-heme CCPs characterized to date and has, therefore, been an attractive target to investigate structure-function relationships for this family of enzymes. Here, we combine for the first time structural studies with site-directed mutagenesis and spectroscopic studies of the mutant enzymes to investigate the roles of amino acid residues that have previously been suggested to be important for activity. The crystal structure of R. capsulatus at 2.7 Angstroms in the fully oxidized state confirms the overall molecular scaffold seen in other di-heme CCPs but further reveals that a segment of about 10 amino acids near the peroxide binding site is disordered in all four molecules in the asymmetric unit of the crystal. Structural and sequence comparisons with other structurally characterized CCPs suggest that flexibility in this part of the molecular scaffold is an inherent molecular property of the R. capsulatus CCP and of CCPs in general and that it correlates with the levels of activity seen in CCPs characterized, thus, far. Mutagenesis studies support the spin switch model and the roles that Met-118, Glu-117, and Trp-97 play in this model. Our results help to clarify a number of aspects of the debate on structure-function relationships in this family of bacterial CCPs and set the stage for future studies. 相似文献
997.
Targett-Adams P Schaller T Hope G Lanford RE Lemon SM Martin A McLauchlan J 《The Journal of biological chemistry》2006,281(39):29221-29227
Chronic infection by hepatitis C virus (HCV) is a leading cause of liver disease for which better therapies are urgently needed. Because a clearer understanding of the viral life cycle may suggest novel anti-viral approaches, we studied the role of host signal peptide peptidase (SPP) in viral infection. This intramembrane protease cleaves within a C-terminal signal sequence in the viral core protein, but the molecular determinants of cleavage and whether it is required for infection in vivo are unknown. To answer these questions, we studied SPP processing in GB virus B (GBV-B) infection. GBV-B is the closest phylogenetic relative of HCV and offers an accurate surrogate model for HCV infection. We demonstrate that SPP also processes GBV-B core protein and that a serine residue in the hydrophobic region of the signal sequence (present also in HCV) is critical for efficient SPP cleavage. The small size of the serine side chain combined with its ability to form intra- and interhelical hydrogen bonds likely contributes to recognition of the signal sequence as a substrate for SPP. By introducing mutations with differing effects on SPP processing into an infectious GBV-B molecular clone, we demonstrate that SPP processing of the core protein is required for productive infection in primates. These results broaden our understanding of the mechanism and requirements for SPP cleavage and reveal a functional role in vivo for intramembrane proteolysis in host-pathogen interactions. Moreover, they identify SPP as a potential therapeutic target for reducing the impact of HCV infection. 相似文献
998.
Structural determinants that target the hepatitis C virus core protein to lipid droplets 总被引:7,自引:0,他引:7
Boulant S Montserret R Hope RG Ratinier M Targett-Adams P Lavergne JP Penin F McLauchlan J 《The Journal of biological chemistry》2006,281(31):22236-22247
Hepatitis C virus core protein is targeted to lipid droplets, which serve as intracellular storage organelles, by its C-terminal domain, termed D2. From circular dichroism and nuclear magnetic resonance analyses, we demonstrate that the major structural elements within D2 consist of two amphipathic alpha-helices (Helix I and Helix II) separated by a hydrophobic loop. Both helices require a hydrophobic environment for folding, indicating that lipid interactions contribute to their structural integrity. Mutational studies revealed that a combination of Helix I, the hydrophobic loop, and Helix II is essential for efficient lipid droplet association and pointed to an in-plane membrane interaction of the two helices at the phospholipid layer interface. Aside from lipid droplet association, membrane interaction of D2 is necessary for folding and stability of core following maturation at the endoplasmic reticulum membrane by signal peptide peptidase. These studies identify critical determinants within a targeting domain that enable trafficking and attachment of a viral protein to lipid droplets. They also serve as a unique model for elucidating the specificity of protein-lipid interactions between two membrane-bound organelles. 相似文献
999.
The Saccharomyces cerevisiae vacuolar proton-translocating ATPase (V-ATPase) is composed of 14 subunits distributed between a peripheral V1 subcomplex and an integral membrane V0 subcomplex. Genome-wide screens have led to the identification of the newest yeast V-ATPase subunit, Vma9p. Vma9p (subunit e) is a small hydrophobic protein that is conserved from fungi to animals. We demonstrate that disruption of yeast VMA9 results in the failure of V1 and V0 V-ATPase subunits to assemble onto the vacuole and in decreased levels of the subunit a isoforms Vph1p and Stv1p. We also show that Vma9p is an integral membrane protein, synthesized and inserted into the endoplasmic reticulum (ER), which then localizes to the limiting membrane of the vacuole. All V0 subunits and V-ATPase assembly factors are required for Vma9p to efficiently exit the ER. In the ER, Vma9p and the V0 subunits interact with the V-ATPase assembly factor Vma21p. Interestingly, the association of Vma9p with the V0-Vma21p assembly complex is disrupted with the loss of any single V0 subunit. Similarly, Vma9p is required for V0 subunits Vph1p and Vma6p to associate with the V0-Vma21p complex. In contrast, the proteolipids associate with Vma21p even in the absence of Vma9p. These results demonstrate that Vma9p is an integral membrane subunit of the yeast V-ATPase V0 subcomplex and suggest a model for the arrangement of polypeptides within the V0 subcomplex. 相似文献
1000.
Purified bovine heart cytochrome c oxidase (CcO) has been extracted from aqueous solution into hexane in the presence of phospholipids and calcium ions. In extracts, CcO is in the so-called "slow" form and probably situated in reverse micelles. At low water:phospholipid molar ratios, electron transfer from reduced heme a and Cu(A) to the catalytic center is inhibited and both heme a3 and Cu(B) remain in the oxidized state. The rate of binding of cyanide to heme a3 in this oxidized catalytic center is, however, dependent on the redox state of heme a and Cu(A). When heme a and Cu(A) are reduced, the rate is increased 20-fold compared to the rate when these two centers are oxidized. The enhanced rate of binding of cyanide to heme a3 is explained by the destabilization of an intrinsic ligand, located at the catalytic site, that is triggered by the reduction of heme a and Cu(A). 相似文献