全文获取类型
收费全文 | 211篇 |
免费 | 17篇 |
专业分类
228篇 |
出版年
2021年 | 3篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 5篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有228条查询结果,搜索用时 0 毫秒
1.
Nonlactating Dutch-Friesian cows were selected from a local slaughterhouse and synchronized with Syncro-Mate B. Cows with a normal progesterone pattern were treated with PMSG (3,000 I.U. i.m.) on Day 10 followed by PG (Prosolvin 22.5 mg) 48 h later. Blood samples were collected daily and at hourly intervals from 30 h after PG. Monoclonal anti-PMSG (Neutra-PMSG) was administered i.v. at 5.8 h after the LH peak in 16 cows; controls (n = 16) did not receive Neutra-PMSG. For comparison, 16 additional cows were superovulated with FSH-P in decreasing doses, twice a day (total 32 mg), starting at Day 10. All cows were inseminated at 10 h after the LH peak. Embryos were evaluated on Days 6 and 7 after flushing upon slaughter (recovery 87%). The number of corpora lutea and follicles on the donor ovaries were counted. No significant differences in the concentrations of progesterone and LH were observed between the three superovulation groups. Upon Neutra-PMSG, PMSG in blood was completely neutralized, it was decreased to < 0.5 ug/l at AI from 7.0 ug/l at the LH peak. The number of transferable embryos was significantly higher after Neutra-PMSG (9.1 per cow) than without Neutra-PMSG (5.3). or upon FSH-superovulation (4.6). The number of cysts on the ovaries of Neutra-PMSG-treated cows was reduced similarly to that after FSH-superovulation. Treatment with Neutra-PMSG shortly after the LH peak positively affects final follicular maturation in PMSG-superovulated cows and results in a nearly two-fold increase of transferable embryos. 相似文献
2.
3.
Summary In Gasteria and Chamaenerion, microtubular configurations were visualized immunocytochemically during meiosis and megasporogenesis in order to study their relationship to cell development, meiotic divisions and selection of the functional megaspore. In Chamaenerion, the intensity of the fluorescence found in megaspores was weaker than that found in Gasteria. Both plants exhibited concentrations of microtubules around the meiocyte nuclei during pachytene-diplotene. Preprophase bands were not observed. In Chamaenerion, cytoplasmic microtubules radiating from meiocyte nuclei were found at late prophase, the dyad stage and in the functional megaspore; in Gasteria, they were observed only at the dyad stage and in the functional megaspore. During the second meiotic division of Gasteria, dividing cells and their nuclei exhibited differences in volumes. Also, the two microtubular spindles of the dyad cells had different widths. Fluorescence indicating the presence of the cytoskeleton diminished during maturation of the large functional megaspores in both plants, whereas in the three degenerating smaller megaspores, fluorescence intensity persisted. Our conclusion is that only an indirect relationship exists between the organization of the microtubular cytoskeleton and selection of the functional megaspore. 相似文献
4.
Repeated transvaginal ultrasound guided puncturing of visible follicles was performed for ovum pick-up (OPU) during Periods A and B, each of which lasted 3 mo. During Period A, 10 cows (A) were used in the study. Period B commenced 1 mo after Period A and two groups of animals were used. The first group (B1) consisted of 9 of 10 cows from Group A. The second experimental group of animals in Period B consisted of 11 cows (B2) which had not been submitted to previous puncture. During the study, all visible follicles larger than 3 mm were punctured and aspirated three times, on Day 3 or 4, Day 9 or 10 and Day 15 or 16 of the estrous cycle. The mean estrous cycle length (+/- SEM) after repeated follicle puncture did not differ among the three groups and was 22.3 +/- 0.4, 22.5 +/- 0.4 and 22.1 +/- 0.3 d for groups A, B1 and B2, respectively. The mean total number (+/- SEM) of punctured follicles per estrous cycle in Group A (13.1 +/- 0.5) was significantly larger than in Groups B1 (11.2 +/- 0.4) and B2 (11.6 +/- 0.4). The largest number of follicles punctured for ovum pick-up in all three groups was always on Day 3 or 4 of the estrous cycle: 4.9 +/- 0.3 follicles; the mean (+/- SEM) number of punctured follicles on Day 9 or 10 and Day 15 or 16 was significantly (P<0.05) lower: 3.4 +/- 0.2 and 3.9 +/- 0.2, respectively. In Period A, primarily 3- to 5-mm follicles were punctured per estrous cycle, while 6- to 10-mm follicles were predominantly punctured in Period B (P<0.05). Recovery rate of oocytes on Day 3 or 4, Day 9 or 10 and Day 15 or 16 were 53, 50 and 52%, respectively. Most oocytes (P<0.05) were aspirated from follicles smaller than 10 mm. 相似文献
5.
6.
M.M. Bevers A.H. Willemse Th.A.M. Kruip D.F.M. Van de Wiel 《Animal reproduction science》1981,4(2):155-163
To determine the role of prolactin in the suppression of ovarian activity during lactation in the sow experiments were performed to investigate a possible inhibitory action of prolactin at the pituitary level. Therefore the LH-response to an intravenous injection of 25 μg synthetic LH-RH was measured in the 1st, 2nd and 3rd week of lactation. The compound was injected under high and low concentrations of prolactin in the peripheral blood, the latter achieved by removal of the piglets 6 h before administration of LH-RH. The results showed no difference in the effect of LH-RH injected at high or low prolactin levels. However, although the mean prolactin concentrations in the 1st, 2nd and 3rd week of lactation were similar, the results clearly demonstrated an increase in LH-response as lactation proceeds.The low responsiveness of the pituitary shortly post partum was also observed when the preparturient rise of prolactin was suppressed by treatment with bromoergocryptine. Injections of LH-RH in the last week of gestation given before and after the physiological increase of PRL, which occurred about 48 h before delivery, all showed low LH-response.It is obvious from the presented data that the LH-response to an intravenous injection of 25 μg LH-RH is in no way correlated with the prolactin levels at the time of treatment. 相似文献
7.
Analyses of successively collected fractions of phloem exudate of Yucca flaccida, and of Yucca fruits picked at various stages of growth, together with experiments on transpiration from fruits, have led to the following conclusions:
- 1 During fruit growth potassium, sodium, magnesium, phosphorus compounds, and nitrogenous substances are delivered to the fruit by both the xylem and the phloem. These solutes move also easily in radial direction between the xylem and phloem part of the vascular bundles. Actually they can be regarded as constituents of one stream of nutrients.
- 2 The overall efficiency of conversion of vascular-fluid dry matter into mature-fruit dry matter is approximately 61 %.
- 3 During its whole period of growth the fruit transpires an amount of water vapour of at least 6 times its own mature fresh weight.
- 4 Estimates could be made for the relative contributions of xylem and phloem in the delivery of fruit constituents. 18% of the water imported by the fruit during its growth had a phloem, 82 % a xylem origin; 89% is transpired, 11 % retained as a fruit constituent. At least 94 % of the dry matter, 69% of the potassium, 56% of the magnesium, 26% of the phosphorus, and 7% of the calcium of the average fruit have been delivered by the phloem. The translocation of nitrogenous substances occurs probably partly in a more indirect way with temporary storage in inflorescence parenchyma.
8.
Summary
Brachiaria decumbens has sexual and apomictic reproduction. Apomixis is facultative and of the aposporic type. In early stages of ovule development, differences in the pattern of callose deposition between sexual and apomictic plants were observed which points to possible differences in carbohydrate metabolism. Therefore, a comparative study on carbohydrate metabolism between a sexual diploid ecotype and an apomictic tetraploidB. decumbens was made. A histochemical determination of two enzymes responsible for sucrose degradation, sucrose synthase and invertase, was performed for all stages of ovule development. In addition, the concentrations of sucrose, glucose, and fructose were measured for each stage of ovule development, both for sexual and apomictic plants. The enzymes were localised by immunohistochemistry with heterologous antibodies. A distinct difference between sexual and apomictic plants was observed in the localisation of sucrose synthase activity as well as in the amount of activity, especially in the early stages of ovular development. Invertase activity localisation was comparable between ovules of the sexual and apomictic plants, but its activity is clearly higher in ovules of sexual plants. The localisation of the enzymes coincided with the place of activity. For both sexual and apomictic plants the amount of sucrose in the ovaries increased with the stage of ovule development. Differences in the amount of sucrose between sexual and apomictic plants in ovaries with ovules in comparable stages of development were detected. A delay in the onset of carbohydrate metabolism during early stages of ovule development characterises the apomictic plant.Abbreviations MMC
megaspore mother cell
- MC
meiocyte
- MS
megaspore
- AI
apospore initial
- CO
coenocyte
- MES
mature embryo sac
- SuSy
sucrose synthase
- INV
invertase
- BMM
buthylmethyl methacrylate
- DTT
dithiothreitol
- DAPI
4,6-diamidino-2-phenylindole
- PBS
phosphate-buffered saline 相似文献
9.
10.
Katrijn Opstoel Johan Pion Marije Elferink-Gemser Esther Hartman Bas Willemse Renaat Philippaerts Chris Visscher Matthieu Lenoir 《PloS one》2015,10(5)
ObjectivesThe aim of this study was to investigate to what extent 9 to 11 year old children participating in a specific sport already exhibit a specific anthropometric, physical fitness and motor coordination profile, in line with the requirements of that particular sport. In addition, the profiles in children with a different training volume were compared and possible differences in training hours per week between children from a low, moderate, and high level of physical fitness and motor coordination were investigated.DiscussionThe study showed that in general, children at a young age do not exhibit sport-specific characteristics, except in children with a high training volume. It is possible that on the one hand, children have not spent enough time yet in their sport to develop sport-specific qualities. On the other hand, it could be possible that they do not take individual qualities into account when choosing a sport. 相似文献