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排序方式: 共有161条查询结果,搜索用时 17 毫秒
1.
2.
R A Van Vliet J S Walton A G Wildeman K J Betteridge A M Gibbins 《Journal of reproduction and fertility》1991,91(1):73-79
Total cellular RNA was isolated from conceptus tissue obtained from 22 superovulated cows 18 days after artificial insemination. Total RNA was also isolated from luteal tissue from 3 cyclic cows 7 and 8 days after oestrus. Luteal and conceptus RNA were simultaneously subjected to formaldehyde-agarose gel electrophoresis and transferred to nitrocellulose by bidirectional diffusion blotting. Northern blots were probed using cDNAs specific for bovine oxytocin and bovine beta-actin gene sequences. Hybridization of the oxytocin cDNA to RNA was consistently observed on autoradiographs as a 0.6 kilobase (kb) band in lanes containing corpus luteum RNA, but was not detected in lanes containing conceptus RNA. The presence of conceptus RNA on the blots was confirmed by hybridization of the actin cDNA to conceptus RNA, which resulted in a 2.0 kb band on autoradiographs. These results suggest that oxytocin is not synthesized by the bovine conceptus on Day 18 of gestation. 相似文献
3.
J M Scodras K J Betteridge B A Croy I B Johnstone D Rieger 《Journal of reproduction and fertility》1991,92(2):483-494
The ability of purified preparations of platelet-activating factor (PAF), from three different suppliers, to induce thrombocytopaenia in mice after splenectomy and to activate mouse platelets in vitro was examined. Although the PAF preparations were potent activators of horse and cow platelets in vitro, injections of up to 1 microgram PAF failed to elicit thrombocytopaenia responses in either CD1 or Swiss Webster random-bred mice. However, when thrombin was injected into Swiss Webster mice, a dose-dependent decrease in the concentration of platelets was observed. Furthermore, isolated platelets from these strains and from 3 inbred lines (C3H/He, BALB/c, C57BL/6) of mice, were not aggregated by PAF in vitro but were sensitive to adenosine diphosphate and thrombin. No change in circulating platelet concentrations was observed over the initial 7 days of gestation in intact Swiss Webster and C57BL/6 or splenectomized C57BL/6 mice, suggesting either an absence of PAF production during early pregnancy in these strains or insensitivity of their platelets to PAF. These results suggest that many mouse strains are unsuitable for the bioassay of PAF. 相似文献
4.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
相似文献
5.
The oviducts of 24 mares were examined to determine the site of retention of unfertilized eggs. The ampullary-isthmic junction regions of 42 of the 48 oviducts were serially sectioned and examined histologically. The remaining parts of the oviducts were flushed and the flushings searched microscopically. Of 45 eggs located, 40 were in the sectioned segments of 24 oviducts and only 5 were in the flushings. All but one of the sectioned segments contained prominent masses of material obstructing the lumen, but these were apparently not the direct cause of egg retention since eggs were found on both sides of them. 相似文献
6.
A. J. Nixon M. P. Gurnsey K. Betteridge R. J. Mitchell R. A. S. Welch 《Journal of Zoology》1991,224(4):589-598
Hair follicle activity and fibre growth were studied using histological sections from the skin of five adult feral does sampled every four weeks for 18 months. The main period of guard hair growth in primary follicles was from November to April. Secondary follicles grew fine, long, nonmedullated fibres (cashmere) from December to June. Shedding of these fibres from secondary follicles had commenced by July and cashmere was absent from the fleece by November. From September to December a subsidiary hair cycle occurred in many secondary follicles which produced minute (vellus) fibres, less than 2.4 mm in length. Some secondary follicles probably shed their cashmere fibres and remain quiescent over spring. Annual pelage changes were therefore achieved with one main growth period, although many secondary follicles underwent another brief hair cycle in spring. 相似文献
7.
Comparisons of oocyte maturation times and of three methods of sperm preparation for their effects on the production of goat embryos in vitro 总被引:3,自引:0,他引:3
Various times of in vitro maturation of oocytes, and three methods of separating spermatozoa from frozen-thawed semen (Percoll density-gradient centrifugation, swim-up, and glass-wool filtration), were compared for their effects on goat embryo production in vitro. Cumulus-oocyte-complexes (COCs) from abattoir ovaries were matured in M199 supplemented with 10% fetal calf serum and hormones. In Experiment 1, COCs were fixed at 4 h intervals from 0 to 27 h of culture to assess oocyte nuclear maturation. A higher proportion cultured for 27 h than for 24 h were in Metaphase II (27/37, 73% vs. 18/33, 55%, P < 0.05). In Experiment 2, the effects of separation methods on total numbers and numbers of membrane-intact spermatozoa, and the acrosome reaction were compared. Total numbers after Percoll density-gradient centrifugation were approximately 4 times higher than after swim-up and approximately 2 times higher than after glass-wool filtration (P < 0.001). Progression of the acrosome reaction was not affected differentially. In Experiments 3 and 4, after 27 h of culture the COCs were inseminated with sperm isolated by the three methods. In Experiment 3, presumptive zygotes were examined for pronucleus (PN) formation at 6, 12, 18 and 24 h post-insemination. At 12 h, male PN formation rate from Percoll-treated spermatozoa was higher than from sperm subjected to swim-up and glass-wool treatments (20/37, 54% vs. 6/37, 16% and 6/38, 16%, respectively; P < 0.001). In Experiment 4, embryos were compared for cleavage at 48 h and development into blastocysts, hatching rates and cell number at 192 h. The rates of cleavage and blastocyst formation in the Percoll-treated group were higher (P < 0.05) than in the swim-up and glass-wool groups (62% and 18% vs. 50% and 11%, and 45% and 8%, respectively). Similarly, the mean cell number in the Percoll group was higher (P < 0.05) than in the swim-up and glass-wool groups (167 +/- 5 vs. 149 +/- 4 and 126 +/- 4, respectively). We conclude that Percoll density-gradient centrifugation is superior to the other two methods for separating goat spermatozoa from frozen-thawed semen in preparation for IVF. 相似文献
8.
The prevention and treatment of coronary heart disease is a major challenge in the overall management of the patient with type 2 diabetes. Diabetic dyslipidaemia is an important risk factor and is open to therapeutic intervention. However, as yet there are no primary or secondary coronary heart disease prevention trials of lipid-lowering therapy reported in diabetic populations. In this review, on-going clinical trials of lipid-lowering therapy in specific diabetic populations will be described. 相似文献
9.
Cellular composition and viability of demi- and quarter-embryos made from bisected bovine morulae and blastocysts produced in vitro 总被引:5,自引:0,他引:5
The cellular composition and viability of intact, IVP embryos were compared with those of demi- and quarter-embryos produced by bisection of IVP morulae and blastocysts. Embryos were produced by established techniques from oocytes harvested from slaughterhouse ovaries. In Experiment 1, morulae at Day 6 or blastocysts at Day 7 were bisected on an inverted microscope using a microsurgical steel blade. Demi-embryos were then cultured without a zona pellucida until Day 8, when they were morphologically assessed for quality (viability). A higher proportion of demi-embryos made from blastocysts than from morulae were classified as viable (381/420, 91% vs 164/267, 61%; P < 0.001). In Experiment 2, only Day 7 blastocysts were bisected, and some of the resulting demi-embryos were bisected a second time 24 h later to produce quarter-embryos. The remaining demi-embryos, the quarter-embryos, and control intact embryos were cultured until Day 9, at which time they were assessed for quality and subjected to immunosurgery and differential staining to count inner cell mass (ICM) and trophectoderm cells. A higher proportion of demi-embryos than quarter-embryos was classified as viable (408/459, 89% vs 223/319, 70%, respectively; P < 0.001). Total cell numbers decreased with successive bisections, but the proportion of surviving cells found in the ICM was significantly (P < 0.05) higher in the best quality demi- and quarter-embryos (35 and 32%, respectively) than in the controls (22%). Transfer of all 12 quarter-embryos derived from 3 blastocysts, in pairs, into 6 recipient heifers resulted in 2 pregnancies, each with a single viable fetus at 90 d of gestation. The fetuses originated from 2 different blastocysts. The results suggest that bisection of intact IVP embryos into demi-embryos and bisection of those into quarter-embryos can increase the number of transferable embryos by as much as 178 and 235%, respectively. 相似文献
10.
Alan C. H. Lee Joanne K. Y. Lam Sammy W. M. Shiu Ying Wong D. John Betteridge Kathryn C. B. Tan 《PloS one》2015,10(9)