全文获取类型
收费全文 | 56001篇 |
免费 | 2989篇 |
国内免费 | 5589篇 |
专业分类
林业 | 6039篇 |
农学 | 8227篇 |
基础科学 | 4724篇 |
8486篇 | |
综合类 | 15019篇 |
农作物 | 2674篇 |
水产渔业 | 1977篇 |
畜牧兽医 | 12345篇 |
园艺 | 1668篇 |
植物保护 | 3420篇 |
出版年
2024年 | 152篇 |
2023年 | 598篇 |
2022年 | 1420篇 |
2021年 | 2129篇 |
2020年 | 2055篇 |
2019年 | 1934篇 |
2018年 | 1473篇 |
2017年 | 1966篇 |
2016年 | 1860篇 |
2015年 | 2557篇 |
2014年 | 2445篇 |
2013年 | 2976篇 |
2012年 | 3387篇 |
2011年 | 3650篇 |
2010年 | 3405篇 |
2009年 | 3263篇 |
2008年 | 2922篇 |
2007年 | 2857篇 |
2006年 | 2756篇 |
2005年 | 2726篇 |
2004年 | 1337篇 |
2003年 | 1137篇 |
2002年 | 995篇 |
2001年 | 1032篇 |
2000年 | 1149篇 |
1999年 | 1465篇 |
1998年 | 1367篇 |
1997年 | 1189篇 |
1996年 | 1101篇 |
1995年 | 1033篇 |
1994年 | 1009篇 |
1993年 | 925篇 |
1992年 | 887篇 |
1991年 | 730篇 |
1990年 | 670篇 |
1989年 | 522篇 |
1988年 | 377篇 |
1987年 | 333篇 |
1986年 | 149篇 |
1985年 | 152篇 |
1984年 | 134篇 |
1983年 | 117篇 |
1982年 | 72篇 |
1981年 | 32篇 |
1980年 | 31篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1965年 | 9篇 |
1963年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
PULMONARY MINERALIZATION IN FOUR DOGS WITH CUSHING'S SYNDROME 总被引:1,自引:0,他引:1
Clifford R. Berry DVM Norman Ackerman DVM Kevin Monce DVM 《Veterinary radiology & ultrasound》1994,35(1):10-16
The clinical and imaging features of four dogs with Cushing's syndrome and pulmonary mineralization are reviewed. Three dogs presented with a primary complaint of respiratory distress/dyspnea. Three dogs had pituitary dependent Cushing's syndrome, while the remaining one dog had iatrogenic Cushing's syndrome. Each dog had clinical features typical for Cushing's syndrome. Two of the dogs were euthanized due to progressive hypoxemia. In each dog, the serum calcium, phosphorous, blood urea nitrogen and creatinine were normal.
A generalized increase in unstructured interstitial pulmonary opacity with diffuse mineralization was noted on thoracic radiographs of all dogs. In one dog, an ill-defined nodular interstitial pattern of mineralization was present. Delayed bone phase scintigraphy using99m Technetium methylene diphosphonate documented generalized pulmonary uptake in two dogs. 99m Technetium labeled microaggregated albumin lung perfusion scans were normal in these two dogs. 99m Tc-MDP scintigraphy can provide useful information in diagnosing pulmonary mineralization in Cushingoid dogs. 相似文献
A generalized increase in unstructured interstitial pulmonary opacity with diffuse mineralization was noted on thoracic radiographs of all dogs. In one dog, an ill-defined nodular interstitial pattern of mineralization was present. Delayed bone phase scintigraphy using
62.
Jeffrey R. Crass MD Ronald L. Genovese VMD James A. Render DVM Errol M. Bellon MD 《Veterinary radiology & ultrasound》1992,33(4):206-216
Ultrasonography and MRI have become valuable tools for imaging of tendon injuries. The current study examines the histopathologic basis for the imaging abnormalities. Five injured equine forelimbs and two normal contralateral limbs were studied with high resolution real time ultrasound and MRI. Histologic sections were made and correlated with the diagnostic images. All lesions were readily seen by both modalities. Lesions characterized by hemorrhage, edma, and cellular infiltration were sonolucent on ultrasound and bright on MRI images. MRI returned to normal as fibrogenesis ensued. Ultrasound images remained abnormal until fibrillar reallgnment occured with completion of the healing process. High resolution real time ultrasound and MRI both accurately reflect the tissue abnormalities in acute tendon injuries. The injured horse does appear to be an effective model for correlative imaging studies of tendon injuries. 相似文献
63.
64.
本文在分析水平连铸传热特征的基础上,给出了一维情况下,计算结晶器出口处铸坯凝固层厚度的解析式,建立了计及轴向传热的连续坯凝固模拟模型。进行了连续坯二维传热的凝固数值模拟,其模拟结果与实验结果吻合较好,具有普遍应用价值。 相似文献
65.
仙客来离体叶培养与植株再生 总被引:8,自引:0,他引:8
以仙客来叶片、叶柄及其不同部位为外植体进行诱导,结果幼叶基部(叶子基部与叶柄相连处的断口部分)诱导愈伤组织频率最高,可达100%。愈伤组织在N_6+BA2mg/1+2,4-D0.5mg/1培养基上培养,约40d左右可100%分化出不定芽,其不定芽数量一块愈伤组织最多可分化出30个以上。将幼苗移入1/2MS+NAA 0.5mg/1培养基中生根最好。 相似文献
66.
用两株单克隆抗体混合后包被ELLISA微孔板,加牛冠状病毒抗原,加经白陶土处理过的兔抗牛冠状病毒免血清,再加上辣根氧化物酶标记的羊抗兔IgG抗体,加底物质显色间接ELISA检测牛冠状病毒抗原获得成功。用此方法检测细胞培养的牛冠状病毒上清液,其敏感度高出血凝试验(HA)8倍,从武汉市附近3个奶牛场采集犊牛腹泻粪便105份,用单抗ELISA检测牛冠状病毒抗原,共检出阳性36份,并与血凝及血凝抑制试验, 相似文献
67.
通过实验表明:在冬季最低气温-28.3℃的黑龙江省密山市饲养产蛋鸡,只要鸡舍保温良好,适当增加鸡的饲养密度,不用供热,也可保持鸡舍内温度在13℃—15℃的最佳鸡产蛋环境温度;在151天的冬季里实验组鸡,按入舍鸡计算平均每只鸡产蛋103.8个,产蛋率为68.74%,仅比对供热取暖鸡舍的对照组鸡群产蛋率低0.5%,故在寒冷的黑龙江省推广产蛋鸡舍冬季不供热是完全可能的,其经济效益也是显著的。 相似文献
68.
The absence or presence of metastases on thoracic radiographs in 55 female dogs with mammary gland tumors was assessed by comparing the results of a single radiographic examination, using dorsoventral and left lateral views, with clinical and histologic follow-up data. Radiographic abnormalities found in dogs with thoracic metastases were classified as well-defined pulmonary nodules, ill-defined pulmonary nodules, and involvement of pleural effusion. No obvious difference in the effect on the right or left lung lobes was found. The sensitivity, specificity and accuracy for the detection of thoracic metastases were 65%, 97%, and 87%, respectively. 相似文献
69.
本文分析了现阶段我国人民的食物结构以及食品加工在开发蛋白质食物开源中的地位和作用,并从五个方面进行了论述。 相似文献
70.