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   1207篇
  免费   74篇
  国内免费   1篇
林业   226篇
农学   26篇
基础科学   10篇
  182篇
综合类   89篇
农作物   27篇
水产渔业   45篇
畜牧兽医   546篇
园艺   24篇
植物保护   107篇
  2021年   19篇
  2020年   14篇
  2019年   8篇
  2018年   28篇
  2017年   31篇
  2016年   42篇
  2015年   22篇
  2014年   30篇
  2013年   59篇
  2012年   70篇
  2011年   64篇
  2010年   43篇
  2009年   21篇
  2008年   46篇
  2007年   50篇
  2006年   49篇
  2005年   41篇
  2004年   43篇
  2003年   36篇
  2002年   40篇
  2001年   18篇
  2000年   25篇
  1999年   19篇
  1998年   9篇
  1992年   9篇
  1991年   18篇
  1990年   13篇
  1989年   22篇
  1988年   11篇
  1987年   18篇
  1986年   10篇
  1985年   15篇
  1984年   8篇
  1983年   12篇
  1982年   8篇
  1979年   13篇
  1978年   11篇
  1975年   8篇
  1974年   9篇
  1973年   17篇
  1972年   15篇
  1971年   13篇
  1970年   12篇
  1969年   12篇
  1968年   8篇
  1967年   12篇
  1931年   8篇
  1930年   9篇
  1929年   28篇
  1926年   11篇
排序方式: 共有1282条查询结果,搜索用时 15 毫秒
61.
Surveillance of H5 avian influenza virus in wild birds found dead   总被引:1,自引:0,他引:1  
  相似文献   
62.
63.
64.
Ohne Zusammenfassung  相似文献   
65.
Caudal epidural analgesia induced by xylazine administration in cows   总被引:6,自引:0,他引:6  
Xylazine (0.05 mg/kg of body weight diluted to a 5-ml volume, using 0.9% NaCl) or 5 ml of 0.9% NaCl was administered epidurally into the first caudal intervertebral space (Co1-Co2) in 8 cows (mean +/- SD body weight, 583 +/- 150 kg). Cows were observed for responses to deep needle pricking of the caudal dermatomes (S3 to Co), sedation, and ataxia. Heart rate, respiratory rate, body temperature, rate of ruminal contractions, coccygeal arterial blood pressure, pHa, blood gas tension (PaO2, PaCO2), base excess, total solids concentration, and PCV were determined before and after xylazine administration. Epidurally administered xylazine induced sedation and selective (S3 to Co) analgesia for at least 2 hours. Mild ataxia of hind limbs was observed in 6 cows, but all cows remained standing. Heart rate, respiratory rate, rate of ruminal contractions, arterial blood pressure, PaO2, PCV, and total solids concentration were significantly (P less than 0.05) decreased, and PaCO2, base excess, and bicarbonate concentration were significantly (P less than 0.05) increased after xylazine administration. Epidurally administered 0.9% NaCl did not alter sensory perception to needle pricking and did not affect any of the physiologic variables determined. Although epidural administration of xylazine induced analgesia and sedation in healthy cows, it should be avoided for epidural analgesia in cattle with heart disease, lung disease, and/or gastrointestinal disease because of its potent cardiopulmonary and ruminal depressant effects.  相似文献   
66.
Breeders have seldom considered the selection for root traits during the genetic improvement in soybean. It is hypothesized that grain yield would be increased by the root function improvement, especially for the current cultivars. The objective of this grafting experiment was to determine the effect of record‐yield cultivars L14 or Z35 as rootstocks on agronomic traits of cultivars released in different decades. A total of 11 cultivars, released in different decades, were used to graft onto L14 or Z35 rootstocks. The agronomic traits were measured in the pot‐culture experiments. Grafting cultivars released in different decades onto L14 or Z35 rootstocks resulted in higher yield, 100‐seed mass and apparent harvest index as compared with those of non‐grafted or self‐grafted plants. Grain yield gain of cultivars grafted onto record‐yield cultivar rootstocks was 0.40 g/plant/year from 1966 to 2006, which was larger than that of non‐grafts and self‐grafts (0.27 g/plant/year). The yield of current cultivars should increase more if their root functions were improved.  相似文献   
67.
The Kyoto protocol [39] directs the signatory countries including France to establish an inventory of carbon stocks in forests. Precise estimates of carbon stocks are hampered by local spatial variability, in particular in wetland areas [25]. The aims of this work are: (i) to estimate the spatial variability of carbon stocks on two hillslopes presenting respectively, a transition between a well-drained zone and a wetland area over a short-distance, and a very progressive transition; (ii) to correlate this variability with soil waterlogging and topographic variations and (iii) to evaluate carbon stock prediction by modelling waterlogging intensity as soil organic carbon (SOC) stocks increase significantly with waterlogging. However, SOC stocks in redoximorphic soils are highly variable, particularly in zones where carbon is redistributed due to erosion and sedimentation. In the litter and the vegetation, the age and density of the stand are the main explanatory factors of C variability. Topographic modelling of the waterlogging intensity could improve the spatial estimation of SOC stocks but not of the C stocks in the humus and vegetation.  相似文献   
68.
This tropical ant was found 1982 in Halle-Neustadt (kindergarden), 1985 in Rostock (bakery), 1994 in Hamburg (dwelling-house), 1996 in Salzgitter-Lichtenberg (dwelling-house) and since 1994 also observed and controlled in Berlin (dwelling-houses). Important exterior characteristics are: size 1.3–1.5 mm (worker), 2.3–2.5 mm (female and male), petiolus its not scale-like, gaster with 4 from dorsal visible segments. Colour: caput blackbrown to black; gaster is cream to brownyellow (worker), brownish (female), blackbrown to black (male), coloured. Their behaviour distinguished them fromMonomorium pharaonis: they run very quickly and restlessly, “ant roads” are not longer than 6–8 hours existent. Preferred food: lying about food, dead flies and cockroaches, cake, milk, sweets. This species was fed in laboratory with mixture from yolkpowder, biskuitmeal and honey, dead insects. The inquiry of attack-locality results with pig-lever or saturated sugar-solution. Baits-boxes were placed on the attack-locality directly. It was distinctly, that Maxforce-Bait (Hydramethylnon) was visited middling. Baits with a mixture of peanut-fat and boric or of yolkpowder, honey and boric were attractive about a longer time and effective in the control. T. melanocephalum was introduced likely with tropical flowers and fruits, sweets or baking from subtropical-tropical region in dwelling houses.  相似文献   
69.
Integrated Water Resources Management   总被引:1,自引:0,他引:1  
  相似文献   
70.
The nuclear male sterility gene ms8 is expected to facilitate the production of sweet pepper (Capsicum annuum L.) hybrids as it provides means for hybridization without the labor-intensive hand emasculation of female inbred lines. The development of molecular markers linked to ms8 locus will help the breeding practice for the selection of hybrid parental lines. In this study, F2 population resulting from a cross between the sweet pepper male sterile line 320 and the male fertile variety Elf was used to identify DNA markers linked to the ms8 locus. With the use of RAPD–BSA technique, seven markers linked to the ms8 locus were found. Four of them were converted into SCAR markers. In addition, two COSII/CAPS markers linked to the ms8 locus were identified. Comparative mapping with reference pepper maps indicated that the ms8 locus is located on the lower arm of the pepper chromosome P4. Identified markers are useful for molecular breeding, however, at present markers tightly linked to ms8 locus are still lacking. Identification of molecular markers linked to the ms8 locus and determination of its chromosomal localization are useful for fine mapping and also provide the perspective for ms8 gene cloning.  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