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   1059篇
  免费   100篇
  国内免费   52篇
林业   32篇
农学   97篇
基础科学   20篇
  63篇
综合类   365篇
农作物   16篇
水产渔业   32篇
畜牧兽医   308篇
园艺   226篇
植物保护   52篇
  2024年   6篇
  2023年   33篇
  2022年   41篇
  2021年   54篇
  2020年   62篇
  2019年   54篇
  2018年   39篇
  2017年   51篇
  2016年   51篇
  2015年   54篇
  2014年   59篇
  2013年   62篇
  2012年   76篇
  2011年   79篇
  2010年   67篇
  2009年   68篇
  2008年   48篇
  2007年   60篇
  2006年   41篇
  2005年   48篇
  2004年   22篇
  2003年   15篇
  2002年   19篇
  2001年   12篇
  2000年   12篇
  1999年   17篇
  1998年   12篇
  1997年   6篇
  1996年   7篇
  1995年   4篇
  1994年   6篇
  1993年   2篇
  1992年   4篇
  1991年   1篇
  1990年   4篇
  1989年   2篇
  1988年   2篇
  1986年   3篇
  1985年   3篇
  1984年   1篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
排序方式: 共有1211条查询结果,搜索用时 734 毫秒
111.
樱桃主要病害及其防治措施探讨   总被引:1,自引:0,他引:1  
樱桃(Cerasus Mill.)在湖北省内多地普遍种植,近年来发展成为一种新兴的种植产业,随着果园规模的扩大,樱桃上的病害不容忽视,通过对湖北省内樱桃上病害的调查,分析了为害樱桃叶部、枝干、根部、果实的主要病害的为害特性,并提出了切实可行的防治措施。  相似文献   
112.
B-mode ultrasonography using a 7.5 megahertz (MHz) transducer was performed on 95 equine cadaver eyes submerged in a water bath. Identification and measurement of the anterior to posterior diameters of the intraocular structures and of the axis bulbi was done. The dorsal ventral axis of the eye was also measured. The eyes were then frozen, sectioned in a saggital plane and the same measurements were made using calipers. Two sets of measurements were then compared statistically.
With the exception of the cornea and the dorsal ventral axis measurements of male horses there was no statistically significant difference in the measurements obtained by the two methods.
The use of B-mode ultrasonography at a frequency of 7.5 MHz to examine the architecture of the equine eye is suggested as a valuable clinical tool. Biometry of the intraocular structures at this frequency may be reasonably accurate.  相似文献   
113.
Magnetic resonance (MR) images were acquired in five dogs and one cat with ocular and orbital disease. MR images were obtained in the dorsal or oblique dorsal, and oblique sagittal planes. Pathologic changes identified in MR images included inflammatory lesions, cystic structures, and neoplasms. All abnormalities were readily apparent in TI-weighted images. MR findings in affected animals were often similar in signal intensity, location, and growth pattern to those found in people with comparable diseases. Although no MR changes were considered pathognomonic for a given disease, MR imaging provided detailed information on the homogeneity, extent and invasiveness of the lesions.  相似文献   
114.
Summary About 13,000 somaclones of 17 cultivars and clones of potato were obtained from in vitro callus cultures and individually planted in a greenhouse, followed by tuber generations grown in the field. These plants were subjected to the multistage selection procedure commonly used in potato breeding. Over a period of five years and three field generations the tuber number, size, shape, eye depth, starch content, starch yield and tuber appearance of these somaclones were assessed and compared with that of the controls. These characters varied depending on donor genotype and trait. The frequency of variants was assessed and there were acceptable proportions of desirable abberrants and invariants among the somaclones. Depending on trait the average gain rate for all donor genotypes ranged between 0.2 and 2.3% for-deviants, between 12.2 and 15.5% for invariants and between 0.1–1.4% for +deviants. It is concluded that this technique should be used into potato breeding programmes to improve commercially important characteristics of specific cultivars and breeding clones.  相似文献   
115.
Phacoemulsification in a clouded leopard (Neofelis nebulosa)   总被引:1,自引:0,他引:1  
Phacoemulsification and prophylactic retinopexy were performed on a 3‐month‐old hand‐raised clouded leopard with a unilateral mature cataract. The same procedures were repeated 3 months later when a cataract developed in the fellow eye. Examination procedures, anesthetic protocols, and surgical techniques were similar to those utilized in domestic cats. The patient retains highly functional aphakic vision at the present age of 2.5 years. An inherited basis for the cataracts is proposed. Although the cub was hand raised, the cataracts were unlike nutritional cataracts reported previously in domestic cats and dogs. To the author’s knowledge this is the first report of cataract formation and phacoemulsification in a clouded leopard.  相似文献   
116.
Magnetic resonance (MR) images of the normal eye and orbit of the dog and cat were acquired. T1-weighted, proton-density, and T2-weighed images were obtained in the oblique dorsal, straight sagittal, and oblique sagittal planes. Signal intensity for the various orbital structures differed among the three resonance techniques. T1-weighted images provided the greatest contrast of the retrobulbar structures. T-1 weighted images also had the highest signal to noise ratio, thereby providing the best anatomic detail. Anatomic components of the globe, retrobulbar structures and ocular adnexa were easily seen in all MR sections. The oblique dorsal and oblique sagittal planes were superior for evaluating the optic nerve in its entirety.  相似文献   
117.
Porcine small intestinal submucosa (SIS) was used as a novel graft material in the management of 10 cases of feline corneal disease. Five cases had stromal ulceration associated with trauma, ocular foreign body and/or suspected infection and required a grafting procedure. Five cases had feline sequestra that were managed by a keratectomy prior to placement of SIS as a graft material. Eight eyes healed with minimal corneal scarring with a very good cosmetic and visual result. One eye with continued aqueous leakage in the immediate postoperative period required a conjunctival pedicle graft to reinforce the SIS graft site. One eye required enucleation 48 h following grafting due to progressive keratomalacia but the SIS material remained intact.  相似文献   
118.
甜樱桃品种吉列玛叶片再生不定梢的研究   总被引:9,自引:0,他引:9  
在基本培养基NN69或WPM上附加BA和低浓度的NAA,IAA,IBA作培养基,诱导甜樱桃品种吉列玛试管苗的叶片产生了不定梢。以WPM附加BA 3mg/L和IAA0.3mg/L的处理,不定梢再生率最高为33.3%。  相似文献   
119.
王齐瑞 《果树学报》2005,22(6):719-721
以红灯为试材,探讨了甜樱桃覆草栽培对其开花结实情况的影响。研究发现覆草栽培可有效地提高甜樱桃结果枝叶片数,使叶片营养水平显著提高,平均花芽数量提高1-2个;同时可使红灯樱桃坐果率提高25.04-28.01个百分点。平均单果重增加18%;果汁的可溶性固形物含量增加1.17个百分点,花期滞后3-5d。  相似文献   
120.
The objective of this retrospective study was to describe signalment, clinical presentation, surgical treatment, outcome, histopathologic, and immunohistochemical characteristics of periocular peripheral nerve sheath tumor in a series of cats. Six cats with a histologic diagnosis of peripheral nerve sheath tumor of the eyelid and/or conjunctiva were identified from 3997 feline ocular histopathologic submissions to the Comparative Ocular Pathology Laboratory of Wisconsin between 1976 and 2002. Medical records were reviewed and data were collected for signalment, eye affected, location, duration, and history of tumor recurrence. Ancillary diagnostic tests, surgical approach, and histopathology were also described. Special stains and immunohistochemistry panels were performed on the tissue. Follow-up information was obtained through telecommunications with the owner and local veterinarian. The mean age of the cats was 8 years (range: 5-15 years). There was an equal distribution of males and females. Breeds represented were two Domestic Long-haired (DLH) cats, three Domestic Short-haired (DSH) cats, and one Manx. The right eye was affected in four cats and the left eye in two cats. The superior eyelid was affected in four cats, the superior conjunctiva in two cats, and the inferior eyelid in one cat. All of the cats that underwent surgical excision, cryoablation, or laser ablation had an average of three recurrences of the tumor. Four of six cats undergoing wide excision with enucleation, exenteration or rhomboid flap had no recurrence of the tumor. Histomorphologically, all of the tumors were of spindle cell type with five of six tumors showing histologic features of Antoni type B tissue. All six tumors stained positive for vimentin. Five of six tumors stained positive for S-100 and laminin. All six tumors were negative for smooth muscle actin. Definitive histologic diagnoses of spindle cell tumors can be difficult. The presence of Antoni A and B histologic patterns as well as immunohistochemical reactivity for vimentin, S-100, and laminin suggest a diagnosis of peripheral nerve sheath tumor. Our findings suggest that local aggressive recurrence is common and that wide surgical excision combined with enucleation or exenteration may be indicated.  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