首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   395篇
  免费   6篇
  国内免费   2篇
林业   22篇
农学   19篇
基础科学   1篇
  74篇
综合类   27篇
农作物   18篇
水产渔业   30篇
畜牧兽医   175篇
园艺   3篇
植物保护   34篇
  2023年   1篇
  2022年   4篇
  2021年   15篇
  2020年   4篇
  2019年   4篇
  2018年   9篇
  2017年   8篇
  2016年   10篇
  2015年   10篇
  2014年   17篇
  2013年   30篇
  2012年   21篇
  2011年   26篇
  2010年   11篇
  2009年   13篇
  2008年   32篇
  2007年   29篇
  2006年   30篇
  2005年   15篇
  2004年   20篇
  2003年   29篇
  2002年   23篇
  2001年   13篇
  2000年   6篇
  1999年   3篇
  1998年   4篇
  1997年   2篇
  1994年   2篇
  1993年   2篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1975年   1篇
  1974年   1篇
  1971年   1篇
排序方式: 共有403条查询结果,搜索用时 62 毫秒
1.
Canine cationic trypsin was purified by salting-out, gel filtration and affinity chromatography. Purity was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight was ca. 28 kDa by SDS-PAGE.

Thirty hybridomas were obtained which produced mAb to canine cationic trypsin by the cell fusion technique. Twenty-two of these recognized cationic trypsin only, while eight hybridomas recognized both cationic and anionic trypsin. Several of the anti-canine cationic trypsin mAb were purified by salting-out and DEAE ion-change chromatography using ascites fluid of immunized BALB/c mice. The mAb proved to have very high specificity to canine cationic trypsin as shown by immunoblotting and it may be possible to use them to develop clinical assays.  相似文献   

2.
Carotenoids are not only important to the plants themselves but also are beneficial to human health. Since citrus fruit is a good source of carotenoids for the human diet, it is important to study carotenoid profiles and the accumulation mechanism in citrus fruit. Thus, in the present paper, we describe the diversity in the carotenoid profiles of fruit among citrus genotypes. In regard to carotenoids, such as β-cryptoxanthin, violaxanthin, lycopene, and β-citraurin, the relationship between the carotenoid profile and the expression of carotenoid-biosynthetic genes is discussed. Finally, recent results of quantitative trait locus (QTL) analyses of carotenoid contents and expression levels of carotenoid-biosynthetic genes in citrus fruit are shown.  相似文献   
3.
4.
Differences in sugar distribution between the villous epithelium and follicle-associated epithelium (FAE) were compared using lectins in the rabbit small intestine. In every portion, villous columnar epithelial cells primarily exhibited a positive reaction to the GalNAc, GlcNAc, galactose, and oligosaccharide. In the ileal Peyer's patch (PP), whereas microvillous epithelial cells exhibited positive reactions, M cells tended to be negative. The villous epithelial reaction to the fucose group was negative, but M cells and microvillous epithelial cells showed a positive to the fucose. No epithelium had a positive reaction to the mannose and glucose. The variety of lectin-binding properties of villous epithelial cells and M cells may reflect specificity for the recognizing luminal substances such as antigenic molecules and bacterial elements.  相似文献   
5.
This study was designed to develop a novel culture method for the efficient proliferation of canine peripheral blood lymphocytes (cPBL) for adoptive immunotherapy. When cPBL were cultured in the presence of concanavalin A (Con A), proliferation of cPBL was induced and expression of interleukin-2 receptor (IL-2R) which enables to respond to exogenously added IL-2 was upregulated. And then, when cPBL were cultured with recombinant human interleukin-2 (rhIL-2) in addition to Con A, proliferation was accelerated and increased to about 10-fold after 1 week. The phenotypic analysis showed that the main population of the cultured cPBL was consisted of CD8+ positive lymphocytes. Among them, CD4+CD8+ double positive (DP) lymphocytes had significantly increased, and the ratio of CD4+ single positive (SP) lymphocytes to CD8+ SP lymphocytes (CD4+SP/CD8+SP) was decreased as compared to before culturing. To evaluate the cytotoxic activity of cPBL cultured with Con A and rhIL-2, furthermore, cytotoxic assay was carried out against xenogeneic melanoma cell line (MeWo), which resulted in MHC-unrestricted cytokilling. These results suggest that the culture method of cPBL by the use of Con A and rhIL-2 may be useful for generating lymphokine activated killer cells, and also this may be beneficial for adoptive immunotherapy of tumor-bearing dogs.  相似文献   
6.
The onset of severe injury to the superficial digital flexor tendon (SDFT) is extremely difficult to predict from slight changes in ultrasonographic findings in cases with no apparent clinical signs. This study investigated the relationship between an increased cross-sectional area (CSA) or edema in the subcutaneous tissue around the tendon and the subsequent onset of severe SDFT injury in Thoroughbred racehorses. Horses were classified into three groups based on ultrasound diagnosis (USD) findings: Group A included cases with enlarged tendons; Group B included cases with tendons of normal size but with prominent edema in the peritendinous tissue; and Group C (control group) included cases with no abnormal USD findings. The incidence of subsequent severe tendon injury was significantly higher in the horses in Groups A (25.7%, 28/101) and B (28.3%, 65/212) than in those in Group C (4.9%, 2/41). There were no significant differences in the median period and the median number of races from the first examination to the subsequent tendon injury between Groups A (140 days, 1 race) and B (120 days, 1 race). The results of this study revealed that horses with increased CSA and peritendinous edema are likely to suffer a subsequent severe tendon injury. Also, these two USD findings, i.e., increased CSA and peritendinous edema, indicate the risk of onset of severe SDFT injury.  相似文献   
7.
Abstract

A water culture pot experiment was conducted to analyze the effects of N application during the ripening period (RP) on photosynthesis, dry matter production, and its impact on grain ripening and yield in two semidwarf indica type varieties viz. Gui Zhao 2 (GZ) and BR3 (BR) compared with a japonica type variety Koganemasari (KO) under four N rates viz. 0 (N0), 10 (N10), 20 (N20), and 40 (N40) mg L?1. Results showed that N application enabled to maintain a higher leaf area and delay leaf senescence in both indica and japonica type varieties but the decrease in the rate, of leaf area was higher in the former than in the latter and the rate was reduced with increasing N rates. Flag leaf photosynthesis and SPAD values of N treated plants were higher throughout the RP, showing the presence of a significant correlation either for each variety or all the varieties together. Higher photosynthetic rate was supported by higher leaf chlorophyll (SPAD value basis) content, stomatai conductance, and N concentration in leaf blades. Top dry matter content increased with increasing N rates mainly due to mean leaf area rather than NAR except for BR during RP but it was higher in KO than in GZ and BR. Reduction of shoot weight due to translocation of dry matter to panicles during RP was suppressed by N rates both in GZ and BR while shoot weight increased in the N-treated plants in KO. The dependency of KO on current photosynthates for panicle weight was found to be almost hundred percent while the contribution of stored carbohydrates in shoot before heading to panicle weight in GZ and BR was in the range of 4-27 and 33-54%, respectively and the rest was contributed by current photosynthates. The percentage increased with increasing N rates. Percentage of ripened grains (PRG) increased with increasing N rates in GZ and BR due to the increase in dry matter production and in the photosynthetic rates of apex leaves, despite the larger spikelet number and larger hull size. However, KO showed almost no variation although it had the highest PRG among the varieties. Brown rice yield followed the same pattern as that of PRG in GZ and BR and the highest yield was produced by BR followed by GZ and KO. These results suggest that N application during RP was more effective in increasing yield in the semidwarf indica type varieties than in the japonica type variety.  相似文献   
8.
9.
In the pearl cultivation farms of the Ehime Prefecture, Japan, mass mortalities of the pearl oyster Pinctada fucata have occurred since 1994. The occurrences of mass mortality roughly coincided with a shift of the dominant phytoplankton from Skeletonema and Chaetoceros to Chaetoceros and Nitzschia all of which belong to Bacillariophyceae. Hence, we evaluated Nitzschia, together with Chaetoceros and Isocrysis, as food for the oyster. Wet weights, lengths, widths, glycogen contents, and growth rates in terms of wet weight of the oysters in all the feeding treatments were significantly higher than those in the non-feeding treatment. The highest glycogen content (2.34%) and growth rate (2.21 g month−1) were found in the Chaetoceros treatment. Growth rate in the Isocrysis treatment (1.63 g month−1) was also high, although glycogen content in this treatment (0.41%) was low. In the Nitzschia treatment, growth rate of the oyster (0.94 g month−1) was the lowest and glycogen content (0.83%) was also low relative to that in the Chaetoceros treatment. Chlorophyll a concentration in fecal pellets was lowest in the Nitzschia treatment (<2.7 μg mg−1), suggesting more complete digestion of Nitzschia by the oyster. Thus, Nitzschia was edible and digestible but not assimilated by P. fucata. We propose the following scenario for the relationship between Nitzschia dominance and mass mortality. When Nitzschia dominates in a culture area, the physiological condition of P. fucata deteriorates due to low assimilation of Nitzschia by the oyster, followed by susceptibility of the oyster to infection by agents lethal to the oyster.  相似文献   
10.

Background

Invasive ecosystem engineers can facilitate their invasions by modifying the physical environment to improve their own performance, but this positive feedback process has rarely been tested empirically except in sessile organisms. The invasive crayfish Procambarus clarkii is an ecosystem engineer that destroys aquatic macrophytes, which provide a physical refuge for animal prey, and this destruction is likely to enhance vulnerability to predators. Using two series of mesocosm experiments, we tested the hypothesis that the invasive crayfish increases its feeding efficiency on animal prey by reducing submerged macrophytes, thus increasing its individual growth rate in a positive density-dependent manner.

Results

In the first experiment, increasing crayfish density reduced both macrophytes and animal prey (dragonfly and chironomid larvae) and, importantly, increased the growth rate of individual crayfish, in accordance with our expectation. In the second experiment, we used artificial macrophytes to clarify whether the physical architecture of macrophytes itself protects animal prey and limits crayfish growth rate. Increasing the artificial macrophyte quantity not only increased the survival of animal prey, but also retarded the crayfish growth rate.

Conclusions

We conclude that macrophytes strengthen bottom-up control of crayfish, but this effect can be relaxed by increasing the density of crayfish via reduction in macrophytes. This positive feedback process may explain the crayfish outbreaks and regime shifts occasionally observed in invaded freshwater ecosystems.
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号