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61.
Effects of low water potential on cortical cell length in growing regions of maize roots 总被引:8,自引:5,他引:3
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Roots growing under low water potential commonly exhibit a marked decrease in growth rate and in diameter. Using median longitudinal sections of fixed maize (Zea mays L. cv WF9 × Mo 17) seedling roots, we investigated the cellular basis for these effects. Cortical cells in the shortened elongation zone of water stressed roots were longer than cortical cells in the comparable location of well-watered roots. Nearly twofold differences in cell length were seen in the region 2 to 4 millimeters behind the root apex. The shortened growth zone, however, leads to a final mean cortical cell length approximately 30% shorter in the stressed roots. These differences were present regardless of the age of the control roots. These data, and the slower growth rate seen in water-stressed roots, suggest that the water deficit causes a significant reduction in the rate of cell supply to the cortical cell files. 相似文献
62.
P Bachmann R N Bramwell S J Fraser D A Gilmore D H Johnston K F Lawson C D MacInnes F O Matejka H E Miles M A Pedde 《Journal of wildlife diseases》1990,26(4):486-501
A series of experiments are described on the acceptance, by red foxes (Vulpes vulpes) and other species, of two types of vaccine-baits intended to deliver liquid rabies vaccine. The baits consisted of a cube of sponge coated in a mixture of tallow and wax, or a plastic blister-pack embedded in tallow. All baits contained tetracycline as a biological marking agent: examination of thin sections of carnivore canines under an ultraviolet microscope revealed a fluorescent line of tetracycline if an individual had eaten baits. Baits were dropped from fixed-wing aircraft flying about 100 m above ground at approximately 130 km/h. Flight lines followed the edges of woodlots midway between parallel roads. Baits were dropped at one/sec, resulting in one bait/36 m on the ground, or 17 to 25 baits per km2. Crows (Corvus brachyrhynchos) removed many baits, but did not appear to lower the percent of the fox population which took bait. Dropping baits only into corn and woodland to conceal baits, to reduce depredation by crows, reduced acceptance by foxes. Acceptance by foxes ranged between 37 and 68%. Meat added as an attractant did not raise acceptance. Presence, absence, color and perforations of plastic bags did not alter bait acceptance. Dispersal by juvenile foxes probably lowered the estimates of bait acceptance. It took 7 to 17 days for 80% (n = 330) of foxes to eat their first bait. The rapidity with which foxes picked up their first bait appeared more affected by unknown characteristics of years or study areas than by experimental variables. Skunks (Mephitis mephitis) and raccoons (Procyon lotor) also ate these baits, but acceptance was lower. Small mammals contacted baits, but rarely contacted the vaccine, which had the potential for vaccine-induced rabies in some species. Aerial distribution of baits was more cost-effective than ground distribution as practiced in Europe. This system has potential for field control of rabies, although higher acceptance will be desirable. 相似文献
63.
Patricia A. Fraser Barbara Moore Rosanne Stein Sharon Alosco Armead H. Johnson Deborah Marcus-Bagley Zuhier Awdeh Edmond J. Yunis Chester A. Alper 《Immunogenetics》1990,31(2):89-93
We analyzed the frequency distribution of 106 complotypes [four allele sets of the major histocompatibility complex (MHC) genes for the complement proteins factor B, C2, C4A, and C4B] from 32 Black families residing in Boston and Washington, DC. Twenty-five different complotypes were identified, among which there were four complotypes that had not been previously observed in our large database of complotypes compiled from family studies of Boston Caucasians and that are, presumably, unique to individuals of African origin. These four African-derived complotypes areFC(1,90)0, FC63, S1C2,17, andSC(3,2,90)0. The frequencies of two of these four unique Black complotypes,FC(1,90)0 andFC63, were increased significantly when compared to Caucasians (pcorr <0.00042, pcorr=0.00294, respectively). The complotypeFC(1,90)0 was in positive linkage disequilibrium withHLA-DR3 haplotypes containing theB locus antigens Bw42, Bw52, Bw53, and Bw58, whileFC63 was associated withHLA-Bw70,-DR5. These findings demonstrate the extensive polymorphism of complotypes in Blacks, and also suggest that it may be possible to define unique extended haplotypes of African origin. 相似文献
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66.
Replicon rescue: a novel strategy to clone the genomic DNA flanking insertions of integrating shuttle vector DNA.
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T L McMahon Z Wilczynska C Barth D J Fraser L Pontes P R Fisher 《Nucleic acids research》1996,24(20):4096-4097
A novel cloning strategy, replicon rescue, was developed for cloning genes disrupted by plasmid insertions. After ligation to a tetracycline resistance cassette, fragments containing a bacterial origin of replication from the insertion are recovered in Escherichia coli because they replicate autonomously. Restriction enzymes for cloning are so chosen that the only legitimate two fragment ligation yielding TetR clones involves a fragment spanning the boundary of the insertion. Replicon rescue was used successfully firstly in a test system to clone the chromosomal orl from a Klebsiella aerogenes strain, and secondly to recover a disrupted gene from a phototaxis-deficient mutant of Dictyostelium. 相似文献
67.
Linkage of cutaneous malignant melanoma/dysplastic nevi to chromosome 9p, and evidence for genetic heterogeneity. 总被引:7,自引:1,他引:6
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A. M. Goldstein N. C. Dracopoli M. Engelstein M. C. Fraser W. H. Clark Jr M. A. Tucker 《American journal of human genetics》1994,54(3):489-496
We examined the relationship between cutaneous malignant melanoma/dysplastic nevi (CMM/DN) and chromosome 9p in 13 pedigrees with two or more living cases of invasive melanoma. We used two highly informative (CA)n repeats, D9S126 and IFNA, previously implicated in familial malignant melanoma (MLM), to conduct linkage analysis. Three analyses were performed: (1) CMM alone--all individuals without either confirmed melanoma or borderline lesions were considered unaffected (model A); (2) CMM/DN with both variable age at onset and sporadics (model B); and (3) CMM affecteds only--all individuals either without confirmed melanoma or with borderline lesions were designated "unknown" (model C). There was significant evidence for linkage to IFNA in all three models. For CMM alone, the maximum lod score (Zmax) was 4.36 at theta = .10 for model A and 3.39 at theta = .10 for model C. For CMM/DN (model B), Zmax = 3.05 at theta = .20. There was no significant evidence for linkage between CMM alone or CMM/DN and chromosome 9p marker D9S126. In addition, there was significant evidence for heterogeneity when a homogeneity test allowing for linkage to chromosome 9p or chromosome 1p or neither region was used. These results suggest that there is an MLM susceptibility locus on chromosome 9p but that familial melanoma is heterogeneous and not all families with CMM/DN are linked to a locus in this region. 相似文献
68.
Many studies have reported on the dental status of elderly patients. The results demonstrate consistent differences between normative and perceived needs in addition to varying levels of awareness of dental education among carers. This review article attempts to integrate a range of social factors which must be considered if holistic and comprehensive care is to be delivered to elderly patients. 相似文献
69.
Margo T. Murphy Norma Morrison John S. Miles Robin H. Fraser Nigel K. Spurr Elizabeth Boyd 《Human genetics》1993,91(6):585-588
The gene encoding the Kell blood group polypeptide has been localized to chromosome 7q33-35 by in situ hybridization using a biotinylated 1.1-kb DNA fragment containing the 3 half of the human cDNA. This assignment is in accord with genetic localization using antigenic variation as a marker, and strongly suggests that Kell antigenic determinants are part of the polypeptide chain rather than the associated sugar molecules. 相似文献
70.