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   513篇
  免费   23篇
林业   62篇
农学   15篇
基础科学   2篇
  108篇
综合类   68篇
农作物   30篇
水产渔业   29篇
畜牧兽医   176篇
园艺   5篇
植物保护   41篇
  2023年   4篇
  2022年   7篇
  2021年   12篇
  2020年   11篇
  2019年   11篇
  2018年   10篇
  2017年   11篇
  2016年   10篇
  2015年   12篇
  2014年   16篇
  2013年   25篇
  2012年   38篇
  2011年   42篇
  2010年   28篇
  2009年   29篇
  2008年   37篇
  2007年   28篇
  2006年   29篇
  2005年   35篇
  2004年   24篇
  2003年   26篇
  2002年   26篇
  2001年   6篇
  2000年   7篇
  1999年   2篇
  1998年   6篇
  1997年   1篇
  1996年   4篇
  1995年   5篇
  1994年   6篇
  1993年   5篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1976年   1篇
  1974年   1篇
  1971年   3篇
  1970年   2篇
  1968年   2篇
  1961年   1篇
排序方式: 共有536条查询结果,搜索用时 0 毫秒
531.
Two Great Dane puppies developed cervical discospondylitis following routine surgery for sterilization. One animal was affected at C4–C5 and the other at C6–C7 intervertebral discs. Pseudomonas aeruginosa was obtained in pure culture from ultrasound-guided disc aspiration in 1 case. Both animals were successfully treated with long-term antibiotics.  相似文献   
532.
The plant minimal exchangeable K (EPl,min) defines the lower accessible limit of the most available pool of soil K to plants. It is also an index of long‐term K reserve in soils. However, its estimation by the classical method of exhaustion cropping is laborious. This study aimed at comparing EPl,min values obtained by the exhaustion cropping method with EPl,min values estimated by an alternative approach based on the cationic exchange capacity (CEC) of the infinitely high selective sites for K (i.e., always saturated with K) in the K‐Ca exchange (EK‐Ca,min). A set of 45 soil samples, corresponding to the various fertilization K treatments of 15 long‐term K fertilization trials, was used in this study. The selected soil samples presented a wide range of texture, CEC, and exchangeable K. The plant minimal exchangeable K was found more or less independent of the K treatment, whereas EK‐Ca,min increased when the soil exchangeable K content increased. The plant minimal exchangeable K was systematically lower than EK‐Ca,min, showing that EK‐Ca,min is at least partially available to the plant. Hence, EK‐Ca,min is not a surrogate of EPl,min. Conversely, the plant minimal exchangeable K was strongly, positively correlated to soil CEC (measured at soil pH; r2 = 0.90***). This soil property can consequently be used as a proxy of EPl,min.  相似文献   
533.
ObjectiveTo assess the accuracy of contrast material injection and the dispersion of injectate following ultrasound guided injections at the level of L6 and L7, in canine cadavers.Study designProspective, randomized, experimental study.AnimalsTwenty nine mixed breed canine cadavers (28.9 ± 6.0 kg).MethodsThree ultrasound-guided approaches to the lumbar plexus (LP) were compared: 1) a dorsal pre-iliac approach at the level of L6; 2) a lateral paravertebral approach at mid-L6; and 3) a lateral paravertebral approach at mid-L7. An isovolumic mixture of iodine-based contrast with new methylene blue (0.1 mL kg−1) was injected bilaterally in the juxta-foraminal region along the L6 or L7 nerve root. Computed tomography was performed followed by segmentation and 3D reconstruction of the lumbar spine and contrast material volumes using dedicated software. Distances between contrast material and the fifth through seventh lumbar foraminae, and length of femoral (FN) and obturator (ON) nerve staining were measured and compared between approaches (p < 0.05).ResultsInjectate moved cranial and caudal to the site of injection, and dispersed into an ovoid shape between the quadratus lumborum, iliopsoas and psoas minor muscles. Injections at L7 resulted in significantly closer contrast proximity to the L6 and L7 foraminae (p < 0.001). Femoral nerve staining was similar for all approaches, ON staining was more consistent after L7 injections (p < 0.001).Conclusion and clinical relevanceAn ultrasound-guided lateral paravertebral approach to the LP proved very practical and accurate, with easy visualization of the plexus and associated nerves. To ensure that the ON is covered by injectate, an approach at the level of L7 is recommended. Further studies are necessary to determine if this correlates with clinically effective local anesthesia.  相似文献   
534.
Dehulled soybean meal prepared from genetically modified, herbicide (glyphosate)-tolerant Roundup Ready soybeans containing the CP4 EPSPS protein and near-isogenic conventional soybeans were assessed in an experiment with growing-finishing pigs. The soybeans were grown in the yr 2000 under similar agronomic conditions except that the Roundup Ready soybeans were sprayed with Roundup herbicide. Both were processed at the same plant. The composition of the two types of soybeans and the processed soybean meal were similar. Corn-soybean meal diets containing conventional or Roundup Ready soybean meal and fortified with minerals and vitamins were fed to 100 cross-bred pigs from 24 to 111 kg BW. Diets contained approximately 0.95% lysine initially and were reduced to 0.80 and 0.65% lysine when pigs reached 55 and 87 kg BW, respectively. There were 10 pens (five pens of barrows and five pens of gilts) per treatment with five pigs per pen. All pigs were scanned at 107 kg mean BW and all barrows were killed at the end of the test for carcass measurements and tissue collection. Rate and efficiency of weight gain, scanned backfat and longissimus area, and calculated carcass lean percentage were not different (P > 0.05) for pigs fed diets containing conventional or Roundup Ready soybean meal. Gilts gained slower, but they were more efficient and leaner (P < 0.05) than barrows. Responses to the type of soybean meal were similar for the two sexes with no evidence of a diet x sex interaction for any of the traits. In most instances, carcass traits of barrows were similar for the two types of soybean meal. Longissimus muscle samples from barrows fed conventional soybean meal tended (P = 0.06) to have less fat than those fed Roundup Ready soybean meal, but water, protein, and ash were similar. Sensory scores of cooked longissimus muscles were not influenced (P > 0.05) by diet. The results indicate that Roundup Ready soybean meal is essentially equivalent in composition and nutritional value to conventional soybean meal for growing-finishing pigs.  相似文献   
535.
536.
This research examines the structure and development of the organic sesame network from Burkina Faso to explain the declining trend in organic sesame export. The paper addresses particularly the question whether the organic sesame network is structurally (re)shaped as a conventional mainstream market or whether it still presents a real alternative to conventional sesame production and trade. It is found that over the last decade organic sesame is increasingly incorporated into mainstream market channels. But contrary to the well-known case of conventionalization in California, where organic agriculture grew into mainstream agro-food arrangements, this study illustrates a case where organic sesame agriculture shrank into mainstream agro-food arrangements. The weak coherence between the production and marketing nodes in the organic sesame chain resulted in failures to vertically mediate information, balance power relationships in and across sesame chains, build trust, and limit price volatility and speculation, resulting in a shrinking organic sesame market. For developing a viable alternative to conventional sesame trading, relations between production and trading nodes in the organic networks need to be strengthened through public–private partnerships, combined with other public and legal reinforcement.  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