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   1128篇
  免费   70篇
林业   93篇
农学   32篇
基础科学   1篇
  244篇
综合类   60篇
农作物   77篇
水产渔业   104篇
畜牧兽医   449篇
园艺   23篇
植物保护   115篇
  2023年   19篇
  2022年   31篇
  2021年   57篇
  2020年   49篇
  2019年   42篇
  2018年   55篇
  2017年   38篇
  2016年   48篇
  2015年   29篇
  2014年   47篇
  2013年   65篇
  2012年   65篇
  2011年   104篇
  2010年   62篇
  2009年   43篇
  2008年   67篇
  2007年   70篇
  2006年   54篇
  2005年   44篇
  2004年   50篇
  2003年   37篇
  2002年   33篇
  2001年   8篇
  2000年   15篇
  1999年   4篇
  1998年   2篇
  1997年   5篇
  1996年   5篇
  1995年   3篇
  1994年   3篇
  1993年   3篇
  1992年   5篇
  1991年   3篇
  1989年   1篇
  1988年   2篇
  1987年   4篇
  1986年   5篇
  1985年   1篇
  1984年   4篇
  1983年   1篇
  1982年   1篇
  1981年   5篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1971年   1篇
  1968年   1篇
  1955年   1篇
排序方式: 共有1198条查询结果,搜索用时 31 毫秒
141.
142.
The population dynamics of naturally-occurring antibiotic producing and nitrogen fixing rhizobacteria, as well as of arbuscular mycorrhizal fungi (AMF) was investigated for a hybrid of maize (Lo964×Lo1016) in comparison to its two parental lines (Lo964 and Lo1016), during four successive 5-week-long growth cycles in the same pot. Beneficial rhizobacteria, such as nitrogen fixers and 2,4-diacetylphloroglucinol (DAPG) and pyrrolnitrin (PRN) producers, as well as AMF were stimulated in the hybrid rhizosphere earlier than in those of the two parental lines. In fact, they were molecularly detected in all rhizospheric samples of the hybrid, independently of the cycle, whereas for the parental lines positive detections occurred only for samples collected after at least two growth cycles. Interestingly, a MPN-PCR approach on rhizospheric DNA samples indicated that, when detected, beneficial rhizobacteria reached similar density in all maize genotypes (2×103 to 2.2×104 target DNA sequences/g?1 of root). Concerning the AMF, even if the three maize genotypes were cultivated in the same soil, it appears that each maize genotype stimulates the AMF population differently. Both the hybrid and the Lo964 line were able to select, in the observed time period, their own adapted phylogenetic AMF subgroups (Glomus A for the hybrid, Archeospora for Lo964), whereas the Lo1016 line was not.  相似文献   
143.
The aims of this study were to develop a dental evaluate any oral cavity disease, develop gypsum models of the dental arches, and to register the occlusions found in coatis (Nasua nasua) in captivity Formulation of the dental chart was assisted by intraoral radiographs from the head of an adult coati cadaver of the same species with the following dental formula.: I 3/3, C 1/1, P 4/3, M 2/2. Seven live coatis of the Nasua nasua species were evaluated. Five of the seven coatis presented with various dental abnormalities as follows: dental plaque (71.4 0%), gingivitis (71.4 %), periodontitis (57.1 %), dental stain (42.9 %), dental abrasion (57.1 %), dental fracture (57.1 %), pulp exposure (42.9 %), malocclusion (57.1 %) and supernumerary teeth (14.2 %).  相似文献   
144.
Marco Quiroz 《中国家禽》2008,30(12):49-50
虽然鸡群中推荐使用水冲洗去除污染物质,但是冲洗不能去除黏液层或者细菌生物膜或者藻类.因此,更多的家禽养殖者添加一些有机酸到饮水和冲洗程序中.这除了抑制饮水系中生物膜形成,还会减少有害细菌,改善动物生长性能和食品安全.  相似文献   
145.
Gastrointestinal mesenchymal tumours from two Spanish ibex (Capra pyrenaica hispanica) were examined grossly, histologically and immunohistochemically. One neoplasm was a 1.5 kg tan multinodular cavitated mass in the forestomach. The other tumour was a firm mural mass 1.2 cm in diameter in the colon. Microscopically, both tumours were formed mainly by spindle shaped cells arranged in closely packed interlacing fascicles. Neoplastic cells in both tumours labelled positively for KIT (CD117), vimentin and alpha-smooth muscle actin. These findings suggest that both neoplasms were gastrointestinal stromal tumours and most likely to be derived from the interstitial cells of Cajal or their progenitor cells.  相似文献   
146.
147.
This study compared the effects of intravaginal and intravenous routes of oxytocin (OT) administration in 46 oestrous‐induced Santa Inês ewes (6‐day treatment with progestin‐releasing intravaginal sponges and a single injection of 200 IU of eCG at the time of sponge removal) that underwent transcervical embryo recovery 6–7 days after oestrous onset and mating. All ewes received 37.5 μg of d‐cloprostenol via latero‐vulvar route, and 1 mg of oestradiol benzoate i.m. 16 hr before and 50 IU of OT 20 min before non‐surgical embryo recovery (NSER), with OT being administered intravenously (n = 21) or intravaginally (n = 21). An overall oestrous response was 95.6% (44/46), and adequate cervical retraction could be accomplished in 78.6% (33/42) of ewes. The percentage of successful NSER procedures was 57% (24/42) or 72.7% (24/33) of animals with sufficient cervical retraction. The duration of NSER procedure averaged 28 min (range: 17–40 min) and ~96% of flushing fluid could be recovered (range: 85%–100%). Out of 18 ewes that could not undergo NSER, 12 (66.6%) presented various anatomical barriers, whilst the other 33.4% did not present these barriers and still could not be traversed. Excluding the ewes with those anatomical features, the overall success rate of NSER was 80% (24/30). The route of OT administration had no effect on NSER efficiency or the ease with which transcervical embryo flushing was performed. Both routes of OT administration can be used for cervical dilation protocol. Discarding ewes with anatomical features precluding cervical penetration is highly recommended to increase the efficacy of NSER in sheep.  相似文献   
148.
An alpaca presented for emergency evaluation of respiratory distress. Physical examination revealed weakness, pyrexia, and a grade V/VI left apical holosystolic murmur. Initial thoracic examination and radiographs were consistent with left sided congestive heart failure. Blood cultures, echocardiographic evaluation, and necropsy findings established a diagnosis of bacterial endocarditis associated with a Listeria monocytogenes infection. Left ventricular endocarditis is uncommon in ruminants, and to the authors' knowledge there are no other reports of L. monocytogenes being the causative agent in an alpaca.  相似文献   
149.
150.
The aim of this study was to evaluate the peak in luteinizing hormone (LH) and the pregnancy rate of sheep (Texel × Santa Inês) in the tropics using short‐ (6 days) and long‐term (12 days) progesterone protocols followed by artificial insemination (AI) both in and out of the breeding season. Experiment 1 was conducted within (IN) the breeding season (autumn, n = 36), and experiment 2 was conducted outside (OUT) of the breeding season (spring, n = 43). In each experiment, the sheep were divided into two groups (6 or 12 days) according to the duration of treatment with a single‐use progesterone release vaginal device (CIDR®, Pfizer, São Paulo, SP, Brazil), and blood samples were collected from 10 animals per group every 4 hr to measure the LH and progesterone concentrations. In the spring, the characteristics of the LH peak did not differ between groups; but in the autumn, there were differences between groups at the beginning (G‐6 IN: 36.44 ± 5.46 hr; G‐12 IN: 26.57 ± 4.99 hr) and end of the LH peak (G‐6 IN: 46.22 ± 7.51 hr; G‐12 IN: 34.86 ± 8.86 hr). The results showed alterations in the LH peak during the breeding season only in the sheep undergoing the short‐term protocol.  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