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   107篇
  免费   14篇
林业   6篇
基础科学   3篇
  11篇
综合类   23篇
水产渔业   2篇
畜牧兽医   64篇
园艺   4篇
植物保护   8篇
  2023年   1篇
  2022年   1篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   4篇
  2016年   5篇
  2015年   6篇
  2014年   3篇
  2013年   9篇
  2012年   3篇
  2011年   4篇
  2010年   5篇
  2009年   1篇
  2008年   5篇
  2007年   1篇
  2006年   2篇
  2005年   4篇
  2004年   1篇
  2003年   4篇
  2002年   2篇
  2001年   2篇
  1999年   5篇
  1998年   3篇
  1997年   3篇
  1996年   10篇
  1995年   3篇
  1994年   1篇
  1993年   4篇
  1992年   1篇
  1991年   1篇
  1990年   5篇
  1989年   5篇
  1988年   2篇
  1987年   1篇
  1985年   2篇
  1980年   2篇
  1978年   2篇
  1967年   1篇
  1966年   1篇
  1947年   1篇
排序方式: 共有121条查询结果,搜索用时 35 毫秒
41.
Over the past century, Israel was a focal point for the improvement of local cucurbit landraces and introduction of cucurbit germplasm. Some improved open-pollinated cucurbit cultivars developed in Israel became established as market types of considerable economic importance far beyond its borders. The origin and history of these cultivars is not widely known and therefore the purpose of the present work was to collect and compare the records relevant to the development of these cultivars, and to describe them more fully. The four economically most important cultivars originated through mass-selection by amateur breeders and were named after their respective farming communities. The ‘Bet Alfa’ cucumber (Cucumis sativus) was selected from a local landrace and introduced in 1936. The ‘Malali’ watermelon (Citrullus lanatus) originated as a rogue in a local landrace and was commercialized around 1940. The ‘Ananas Yoqne‘am’ melon (Cucumis melo) was selected from a local landrace and commercialized around 1950. The ‘Ha‘Ogen’ melon was selected from a cultivar introduced from Hungary and commercialized in the 1950s. The outstanding fruit quality of these four cultivars resulted in their widespread planting in Israel and neighboring countries. Moreover, the quality of the cucumber and melon cultivars inspired successive improvements, notably introgression of disease resistance and development of hybrids, by Israeli breeder-geneticists. The ever-increasing demand for their high-quality fruits established as international market types the Bet Alfa cucumber, the Ananas Yoqne‘am melon, and the Ha‘Ogen melon and its derivative, the Galia melon, and each is intensively bred today by local and multinational seed companies.  相似文献   
42.
43.
Lymphoma in the left femoral nerve of a 10-year-old English Cocker Spaniel caused complete paralysis of the affected limb. Neoplastic cells were immunopositive for CD79a and Pax5 and negative for CD3. Neoplastic cells were in multiple lymph nodes and one kidney but spared bone marrow. The clinical and histologic features in this case resemble those of the rare human condition of neurolymphomatosis.  相似文献   
44.
Many of the best management practices (BMPs) that are recommended for agricultural producers have not been scientifically evaluated for their conservation benefits considering the soil, climate, and hydrology of the proposed application location. The goal of this study was to compare royal palm (Roystonea elata) production in south Florida, USA, using tensiometer automated irrigation and reduced soil applications of nitrogen (N) and phosphorus (P), to that of traditional grower practices considering water savings, nutrient inputs, crop yield, crop nutrient status, soil nutrient status, and economic analyses. The study consisted of six treatments: (1) control (i.e., a grower irrigation rate and N and P fertilizer rates); (2) irrigation system automated to irrigate when soil water suction exceeded 5 kPa and the grower N and P rates; (3) irrigation system automated to irrigate when soil water suction exceeded 15 kPa and the grower N and P rates; (4) irrigation system automated to irrigate when soil water suction exceeded 15 kPa and 50% of the grower N and P rates; (5) the grower irrigation rate and 75% of the grower N and P rates; and (6) the grower irrigation rate and 50% of the grower N and P rates. Irrigation water volume applied, plant diameters, and plant heights were measured periodically throughout the study and plant tissue samples and soil samples were collected periodically for analysis of N and P content. Significant differences among treatments were only observed for the irrigation water volume applied. Automating the irrigation system to irrigate at soil suction exceeding 5 and 15 kPa resulted in 75 and 96% less water applied, respectively, than traditional irrigation scheduling practices used by a grower. Economic analyses suggested that all treatments would result in financial savings ranging from 7 to 34% per ha considering a 5-year, 2 ha investment. Thus, automating irrigation based on soil water suction for palm production in southern Florida, USA and similar locations will result in more sustainable agricultural production systems by benefiting the environment (less nutrients and water applied) and the grower (lower cost).  相似文献   
45.
Irrigation with treated wastewaters can improve nutrient levels and yield of crops planted on degraded soils. This study evaluated how irrigation with treated industrial wastewater affected biomass production and nutrition of maize plants and physio-chemical properties of a degraded soil. The experiment was conducted in a greenhouse using PVC columns. Treatments consisted of 8 treatments irrigated with clean water and increasing doses of N and P, and 8 treatments with 4 proportions of wastewater irrigation (25%, 50%, 75% and 100% v/v). In general, maize biomass did not differ between irrigation water sources. Differences were largely associated with N nutrition. We observed increases in concentrations of N, P, K, S, Mn, Na, Cu, and Zn in tissue of maize under irrigation with wastewater. The addition of treated wastewater increased the P and Na concentrations, and EC values in the soil without affecting clay dispersion in water. An associated economic analysis indicated that wastewater irrigation would not be economically feasible without including environmental benefits. In southern Brazil, the proportion of irrigation water that is wastewater should not exceed 50%.  相似文献   
46.
Diffuse large B‐cell lymphoma (DLBCL) is the most common haematopoietic malignancy in dogs. Recently, MYC and BCL2 expression levels determined with immunohistochemistry (IHC) were found to be prognostic in people with DLBCL. We hypothesized that canine DLBCL can be similarly subdivided into prognostic subtypes based on expression of MYC and BCL2. Cases of canine DLBCL treated with CHOP chemotherapy were retrospectively collected and 43 dogs had available histologic tissue and complete clinical follow‐up. Median values of percent immunoreactive versus immunonegative cells were used to determine positive or negative expression status. Completion of CHOP was significantly associated with a positive outcome. Compared with human patients, our canine DLBCL patients had high IHC expression of both MYC and BCL2, and relative expression levels of one or both markers were not associated with clinical outcome.  相似文献   
47.
Seven experiments were conducted to study the effect of freezing extenders, antioxidants, motility stimulants, thawing temperature, incubation temperature and time, centrifugation and capacitation on sperm chromatin instability (CI) as well as the influence of sperm CI on pregnancy rates of heifers (n = 360) after AI with frozen semen. Semen was collected once a week from Blonde d’Aquitaine and Limousine bulls (n = 3/breed) via an artificial vagina and only individual ejaculates (n = 300) of >0.3 × 109 sperm/ml and ≥ 70% progressive motility were used. Sperm CI was evaluated by nuclear DNA susceptibility to acid‐induced denaturation using acridine orange fluorescence and by chromatin susceptibility to decondensation using quantitative transmission electron microscopy. Bioxcell extender was better than AndroMed and egg yolk extenders in terms of low incidence of sperm CI in one bull (p < 0.05). Neither antioxidants (EDTA–2Na, Na‐pyruvate and albumin) nor motility stimulants (caffeine and blood serum) had any significant effect on sperm CI. Thawing of frozen semen at 45°C for 30 s decreased (p < 0.025) CI in one bull. Incubation of frozen sperm at 25 and 39°C for 240 min increased sperm CI percentages from 3.47 ± 0.48 and 4.50 ± 0.41% to 6.70 ± 0.36 and 9.71 ± 0.53%, respectively (p < 0.001). Although centrifugation and removal of extracellular milieu increased CI of cooled sperm, it decreased CI of frozen–thawed sperm (p < 0.025). Follicular fluid as a capacitating agent destabilized chromatin structure (p < 0.001). Sperm vulnerability to CI had a negative impact (r2 = 0.37–0.77, p < 0.001) on fertility of frozen ejaculates. In conclusion, in vitro manipulation of bovine semen can influence incidence of sperm CI, whereas integrity of sperm chromatin contributes significantly to heifers’ fertility. We would recommend selection of the appropriate extender and thawing temperature for each bull together with careful manipulation of frozen semen to minimize damage of sperm chromatin.  相似文献   
48.
49.
This paper describes a primary extraskeletal osteogenic sarcoma arising in the spleen of an 11-year-old, male, cross-bred Terrier. Initial diagnosis was made after surgical removal of a splenic mass, at which time the liver and other abdominal viscera appeared grossly normal. However, elevations in the activities of alanine aminotransferase and alkaline phosphatase in blood taken 7 days after laparotomy suggested that hepatic metastases were developing. This was confirmed when the dog died 3.5 months after surgery, with massive hepatic metastatic involvement. There appears to be no previous report of the spleen being the primary site of such a neoplasm in the dog.  相似文献   
50.
Amitraz, a formamidine insecticide, is used topically in the treatment of demodicosis and other ectoparasitic infestations. When 3.78 L (containing 2.1 g) of amitraz (twice the recommended concentration) was applied to 5 dogs 4 hours before glucose (0.6 g/kg of body weight) was administered IV, plasma glucose concentration increased, but the increase in plasma insulin concentration, which usually follows IV administered glucose, was suppressed. The results suggested that amitraz induced hyperglycemia at least partly by inhibiting insulin release.  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