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81.
Geoffrey W. Garnham Geoffrey A. Codd Geoffrey M. Gadd 《Journal of applied phycology》1993,5(3):307-315
Accumulation of pertechnetate ions (99TcO4
–) by the cyanobacterial speciesSynechocystis PCC 6803,Synechococcus PCC 6301,Plectonema boryanum,Anabaena variabilis and a redOscillatoria sp. consisted solely of a single rapid energy-independent phase (biosorption); no energy-dependent uptake was detected. Biosorption of TcO4
– was concentration-dependent and could be described by a Freundlich adsorption isotherm for each cyanobacterial species examined. Decreasing pH increased the accumulation of TcO4
– by all the species as did an increase in external NaCl concentration. Accumulation of TcO4
– was also increased inA. variabilis, P. boryanum and the redOscillatoria by an increased external osmotic potential. Concentrations of cations affected TcO4
– accumulation; K+ increased accumulation in all the species, Mg2+, Ca2+, Sr2+ and Cs+ increased accumulation inSynechococcus PCC 6301 and Ca2+ increased accumulation by the redOscillatoria. Some anions decreased TcO4
– accumulation; CO3
2– inA. variabilis and the redOscillatoria, SO4
2– inSynechocystis PCC 6803, and HCO3
– inP. boryanum. The majority of TcO4
– accumulated by all the cyanobacteria was easily desorbed, with no difference in the amounts desorbed between desorption agents of different pH or cation concentration.(*author for correspondence) 相似文献
82.
In situ hybridization of atrial natriuretic peptide mRNA in the endothelial cells of human umbilical vessels 总被引:1,自引:0,他引:1
Wen Qin Cai Giorgio Terenghi Philippe Bodin Geoffrey Burnstock Julia M. Polak 《Histochemistry and cell biology》1993,100(4):277-283
The localization of mRNA encoding preproatrial natriuretic peptide (ANP) was investigated in cultured human umbilical vein endothelial cells (HUVEC) and tissue preparations of umbilical vein and artery. The techniques used were in situ hybridization and in situ hybridization combined with immunocytochemistry, using 32P-radiolabelled and non-radioactive digoxigenin labelled complementary RNA probes. Human ANP mRNAs are mainly localized in the endothelial cells of the umbilical vein and, to a lesser extent, in the endothelial cells of the umbilical artery. The autoradiographic labelling and the intensity of digoxigenin staining were significantly reduced by treatment with RNase before in situ hybridization. This study provides unequivocal evidence for the expression of the ANP gene in the endothelial cells of human umbilical vessels, confirming that these endothelial cells have the ability to synthesize this peptide. The functional significance of the presence of the ANP mRNA in the endothelial cells of human umbilical vessels is discussed. 相似文献
83.
Robert R. Sokal Geoffrey M. Jacquez 《Evolution; international journal of organic evolution》1991,45(1):152-168
We generated numerous simulated gene-frequency surfaces subjected to 200 generations of isolation by distance with, in some cases, added migration or selection. From these surfaces we assembled six data sets comprising from 12 to 15 independent allele-frequency surfaces, to simulate biologically plausible population samples. The purpose of the study was to investigate whether spatial autocorrelation analysis will correctly infer the microevolutionary processes involved in each data set. The correspondence between the simulated processes and the inferences made concerning them is close for five of the six data sets. Errors in inference occurred when the effect of migration was weak, due to low gene frequency differential or low migration strength; when selection was weak and against a background with a complex pattern; and when a random process—isolation by distance—was the only one acting. Spatial correlograms proved more sensitive to detecting trends than inspection of gene-frequency surfaces by the human eye. Joint interpretation of the correlograms and their clusters proved most reliable in leading to the correct inference. The inspection and clustering of surfaces were useful for determining directional components. Because this method relies on common patterns across loci, as many gene frequencies as feasible should be used. We recommend spatial autocorrelation analysis for the detection of microevolutionary processes in natural populations. 相似文献
84.
Geoffrey M. White 《American anthropologist》2003,105(1):164-167
Represented Communities: Fiji and World Decolonization. John D. Kelly and Martha Kaplan. Chicago: University of Chicago Press, 2001. 243 pp.
Cultural Memory: Reconfiguring History and Identity in the Postcolonial Pacific. Jeannerte Marie Mageo. Honolulu: University of Hawai'i Press, 2001. 222 pp.
In Colonial New Guinea: Anthropological Perspectives. Naomi M. McPherson. ed. Pittsburgh: University of Pittsburgh Press, 2001. 264 pp. 相似文献
Cultural Memory: Reconfiguring History and Identity in the Postcolonial Pacific. Jeannerte Marie Mageo. Honolulu: University of Hawai'i Press, 2001. 222 pp.
In Colonial New Guinea: Anthropological Perspectives. Naomi M. McPherson. ed. Pittsburgh: University of Pittsburgh Press, 2001. 264 pp. 相似文献
85.
Electron microscopy, in conjunction with X-ray microanalysis, was used to investigate the effects of exposure to cadmium on the elemental composition of the macroalgaUlva lactuca. The cell wall was the only region of the cell to show any marked change in chemical composition as a result of exposure to cadmium, with less calcium evident in cadmium-treated thallus compared with untreated thalli. The cell wall ofU. lactuca is a complex structure made up of polysaccharides consisting of many-branched chains composed mostly of rhamnose and galactose subunits. Some of the hydroxyl groups on the subunits are substituted by sulphate groups. Borate is associated with the rhamnose subunits, which contain no sulphate groups, and calcium binds to borate, cross-linking the rhamnose groups. The borate-calcium complex adds rigidity to the cell wall; the replacement of calcium by cadmium will, therefore, influence the rigidity of the thallus. The ecological significance of this work is discussed with respect to the ability of the alga to withstand grazing or emersion. 相似文献
86.
87.
Mark A. Brown Alan Carne Geoffrey K. Chambers 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》1996,113(4):731-736
α2-Macroglobulin (α2-M), a large molecular mass proteinase-binding protein, was identified in plasma from tuatara (Sphenodon), a rare reptile endemic to New Zealand. In this genus, α2-M constitutes 11–13% of total plasma protein (∼2.2–3.9 mg/ml). Analysis of blood samples collected at approximately monthly intervals from individual tuatara indicated that the plasma level of α2-M remains fairly constant. The subunits of tuatara α2-M have an apparent molecular mass of ∼160 kDa as determined by SDS-polyacrylamide gel electrophoresis and the intact protein is an oligomer that contains inter-chain disulfide bonds. N-terminal sequence analyses of tuatara α2-M revealed a distinct similarity to α-macroglobulins of other vertebrates and that at least two types of α2-M subunits are present in plasma of tuatara. 相似文献
88.
Collings David A.; Wasteneys Geoffrey O.; Williamson Richard E. 《Plant & cell physiology》1995,36(5):765-772
The cortical cytoplasm of the alga Nitella contains reticulateactin that does not survive perfusion fixation with glutaraldehydeunless prestabilized with the cross-linker 3-maleimidobenzoyl-N-hydroxysuccinimidester (MBS). Cytochalasin D remodels thiscortical actin into short rods which are more stable, survivingaldehyde fixation without MBS pre-treatment. The overall alignmentof these actin rods correlates with that of cortical microtubules(transverse in young cells, random in old cells) but probablydoes not involve one-to-one correspondence. The time course,dose dependence and reversibility of these structural changesbroadly resemble those for streaming inhibition by cytochalasinbut the cortical actin responds to concentrations that do notslow streaming. Because the structural changes concern the corticaland not the subcortical actin, they seem unlikely to directlyinhibit streaming. Formation of cortical rods is not a responseto streaming inhibition per se since it does not occur whentwo other inhibitors of streaming (2,4-dinitrophenol (DNP) andNethyl maleimide (NEM)) are used. NEM, however, resembles MBSin stabilizing the reticulate form of cortical actin even thoughit cannot cross link.
1Address from July 1995; Department of Biology, Faculty of Science,Osaka University, Machikaneyama 1-1, Tayonaka, Osaka, 560 Japan. 相似文献
89.
Geoffrey Fryer 《Hydrobiologia》1995,307(1-3):57-68
The distinctness of the Anomopoda and the polyphyletic nature of the so-called Cladocera are emphasized.An attempt is made to reconstruct the ancestral anomopod, which probably lived in Palaeozoic times. This task is facilitated by the availability of detailed information on extant forms, which includes functional as well as purely morphological considerations and enables us to understand the means whereby complex mechanisms were transformed during evolution. Comparative studies on the ecology and habits of extant forms also throw light on the probable way of life of the ancestral anomopod.Adaptive radiation within the Anomopoda is briefly surveyed and an outline of the suggested phylogeny of the order is indicated.Institute of Environmental and Biological Sciences, University of Lancaster 相似文献
90.
Effect of inhA and katG on isoniazid resistance and virulence of Mycobacterium bovis 总被引:10,自引:1,他引:9
Theresa M. Wilson Geoffrey W. de Lisle Desmond M. Collins 《Molecular microbiology》1995,15(6):1009-1015
Isoniazid (INH) resistance of the Mycobacterium tuberculosis Complex (MtbC) is associated with both loss of catalase activity and mutation of the inhA gene. However, the relative contributions of these changes to resistance and to the loss of virulence for guinea-pigs is unknown. In this study, a virulent strain of Mycobacterium bovis, a member of the MtbC., was exposed to increasing concentrations of INH. Two INH-resistant strains were produced which had lost catalase activity. Strain WAg405, which had a higher resistance to INH, also had a mutation in the inhA gene. This demonstrated that loss of catalase activity and mutation of inhA had a cumulative effect on INH resistance. When a functional katG gene was integrated into the genome of WAg405 the INH resistance was greatly reduced. This indicated that most of the resistance had been caused by loss of catalase activity. While the parent INH-sensitive strain was virulent for guinea-pigs, the INH-resistant strains were significantly less virulent. Integration of a functional katG gene into the most resistant strain restored full virulence. This clearly established that katG is a virulence factor for M. bovis and that mutation of the inhA gene has no effect on virulence. 相似文献