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排序方式: 共有1297条查询结果,搜索用时 93 毫秒
991.
Submucosal Gland Myoepithelial Cells Are Reserve Stem Cells That Can Regenerate Mouse Tracheal Epithelium 总被引:1,自引:0,他引:1
Thomas J. Lynch Preston J. Anderson Pavana G. Rotti Scott R. Tyler Adrianne K. Crooke Soon H. Choi Daniel T. Montoro Carolyn L. Silverman Weam Shahin Rui Zhao Chandler W. Jensen-Cody Andrea Adamcakova-Dodd T. Idil Apak Evans Weiliang Xie Yulong Zhang Hongmei Mou B. Paul Herring Peter S. Thorne John F. Engelhardt 《Cell Stem Cell》2018,22(5):653-667.e5
992.
Site-directed mutagenesis of the mecA gene from a methicillin-resistant strain of Staphylococcus aureus. 总被引:2,自引:1,他引:1 下载免费PDF全文
C Y Wu W E Alborn Jr J E Flokowitsch J Hoskins S Unal L C Blaszczak D A Preston P L Skatrud 《Journal of bacteriology》1994,176(2):443-449
The mecA-27r gene from Staphylococcus aureus 27r encodes penicillin-binding protein 2a (PBP2a-27r), which causes this strain to be methicillin resistant. Removal or replacement of the N-terminal transmembrane domain had no effect on binding of penicillin, but removal of portions of the putative transglycosylase domain (144, 245, or 341 amino acids after the transmembrane region) destroyed penicillin-binding activity. The SXXK, SXN, and KSG motifs, present in all penicillin-interacting enzymes, were found in the expected linear spatial arrangement within the putative transpeptidase region of PBP2a-27r. Alterations of amino acids in all three of these motifs resulted in elimination of penicillin-binding activity, confirming their roles in the interaction with penicillin. 相似文献
993.
Maneechote Chanya; Holtum Joseph A.M.; Preston Christopher; Powles Stephen B. 《Plant & cell physiology》1994,35(4):627-635
A biotype of Avena sterilis ssp. ludoviciana is highly resistantto a range of herbicides which inhibit a key enzyme in fattyacid synthesis, acetyl-CoA carboxylase (ACCase). Possible mechanismsof herbicide resistance were investigated in this biotype. Acetyl-CoAcarboxylase from the resistant biotype is less sensitive toinhibition by herbicides to which resistance is expressed. I50values for herbicide inhibition of ACCase were 52 to 6 timesgreater in the resistant biotype than in the susceptible biotype.This was the only major difference found between the resistantand susceptible biotypes. The amount of ACCase in the meristemsof the resistant and susceptible is similar during ontogenyand no difference was found in distribution of ACCase betweenthe two biotypes. Uptake, translocation and metabolism of [14C]diclofop-methylwere not different between the two biotypes. In vivo, ACCaseactivity in the meristems of the susceptible biotype was greatlyinhibited by herbicide application whereas only 25% inhibitionoccurred in the resistant biotype. Depolarisation of plasmamembrane potential by 50 µM diclofop acid was observedin both biotypes and neither biotype showed recovery of themembrane potential following removal of the herbicide. Hence,a modified form of ACCase appears to be the major determinantof resistance in this resistant wild oat biotype. (Received February 10, 1994; Accepted March 11, 1994) 相似文献
994.
Flanking Duplications and Deletions Associated with P-Induced Male Recombination in Drosophila 总被引:13,自引:6,他引:7 下载免费PDF全文
We studied P element-induced recombination in germline mitotic cells by examining the structure of the recombinant chromosomes. We found that most recombinants retain a mobile P element at the site of the recombination, usually with either a deletion or a duplication immediately adjacent to the P end at which the crossover occurred. The sizes of these deletions and duplications ranged from a few base pairs to well over 100 kb. These structures fit the ``hybrid element insertion' (HEI) model of male recombination in which the two P-element copies on sister chromatids combine to form a ``hybrid element' whose termini insert into a nearby position on the homologue. The data suggest that P-induced recombination can be used as an efficient means of generating flanking deletions in the vicinity of existing P elements. These deletions are easily screened using distant flanking markers, and they can be chosen to extend in a given direction depending on which reciprocal recombinant type is selected. Furthermore, the retention of a mobile P element allows one to extend the deletion or generate additional variability at the site by subsequent rounds of recombination. 相似文献
995.
P. M. Hollingsworth C. D. Preston R. J. Gornall 《Plant Systematics and Evolution》1996,202(3-4):219-232
Evidence from isozyme analyses indicates thatPotamogeton ×suecicus is the hybrid betweenP. pectinatus andP. filiformis. The hybrid appears to have arisen on several occasions. The isozyme profiles of this hybrid from the Rivers Wharfe and Ure in Yorkshire, south of the present limit of distribution ofP. filiformis, suggest that each population is a single clone; these clones may be relics from the Weichselian glacial period. Populations of the putative hybrid from the Rivers Tweed and Till are notP. ×suecicus but probably haveP. vaginatus andP. pectinatus as parents. If so, this is a remarkable example of a pondweed hybrid persisting vegetatively in an area outside the distributional range of one of its parents. 相似文献
996.
Sequence variation among 10 alleles of the alcohol dehydrogenase (Adh) gene
of the Hawaiian drosophilid D. mimica was analyzed with reference to the
evolutionary history of the Hawaiian subgroup as well as to levels and
patterns of polymorphism of the Adh gene in continental drosophilid
species. The Adh gene of D. mimica is less polymorphic than that of other
drosophilid species, and no replacement substitutions were found.
Statistical analyses of the Adh alleles suggested the action of balancing
selection and revealed significant linkage disequilibrium among three of
the variable sites. The effective population size was estimated to be only
slightly smaller than that of continental species and, surprisingly, on the
same order of magnitude as the actual size.
相似文献
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Adam L. Bailey Michael Lauck Samuel D. Sibley Thomas C. Friedrich Jens H. Kuhn Nelson B. Freimer Anna J. Jasinska Jane E. Phillips-Conroy Clifford J. Jolly Preston A. Marx Cristian Apetrei Jeffrey Rogers Tony L. Goldberg David H. O'Connor 《Journal of virology》2016,90(2):630-635
Wild nonhuman primates are immediate sources and long-term reservoirs of human pathogens. However, ethical and technical challenges have hampered the identification of novel blood-borne pathogens in these animals. We recently examined RNA viruses in plasma from wild African monkeys and discovered several novel, highly divergent viruses belonging to the family Arteriviridae. Close relatives of these viruses, including simian hemorrhagic fever virus, have caused sporadic outbreaks of viral hemorrhagic fever in captive macaque monkeys since the 1960s. However, arterivirus infection in wild nonhuman primates had not been described prior to 2011. The arteriviruses recently identified in wild monkeys have high sequence and host species diversity, maintain high viremia, and are prevalent in affected populations. Taken together, these features suggest that the simian arteriviruses may be “preemergent” zoonotic pathogens. If not, this would imply that biological characteristics of RNA viruses thought to facilitate zoonotic transmission may not, by themselves, be sufficient for such transmission to occur. 相似文献
1000.
Nikos E. Papanikolaou Nikos Demiris Panagiotis G. Milonas Simon Preston Theodore Kypraios 《PloS one》2016,11(1)
Mutual interference involves direct interactions between individuals of the same species that may alter their foraging success. Larvae of aphidophagous coccinellids typically stay within a patch during their lifetime, displaying remarkable aggregation to their prey. Thus, as larvae are exposed to each other, frequent encounters may affect their foraging success. A study was initiated in order to determine the effect of mutual interference in the coccinellids’ feeding rate. One to four 4th larval instars of the fourteen-spotted ladybird beetle Propylea quatuordecimpunctata were exposed for 6 hours into plastic containers with different densities of the black bean aphid, Aphis fabae, on potted Vicia faba plants. The data were used to fit a purely prey-dependent Holling type II model and its alternatives which account for interference competition and have thus far been underutilized, i.e. the Beddington-DeAngelis, the Crowley-Martin and a modified Hassell-Varley model. The Crowley-Martin mechanistic model appeared to be slightly better among the competing models. The results showed that although the feeding rate became approximately independent of predator density at high prey density, some predator dependence in the coccinellid’s functional response was observed at the low prey—high predator density combination. It appears that at low prey densities, digestion breaks are negligible so that the predators do waste time interfering with each other, whereas at high prey densities time loss during digestion breaks may fully accommodate the cost of interference, so that the time cost may be negligible. 相似文献