全文获取类型
收费全文 | 10996篇 |
免费 | 700篇 |
国内免费 | 656篇 |
专业分类
林业 | 872篇 |
农学 | 766篇 |
基础科学 | 371篇 |
1987篇 | |
综合类 | 3184篇 |
农作物 | 651篇 |
水产渔业 | 791篇 |
畜牧兽医 | 2421篇 |
园艺 | 589篇 |
植物保护 | 720篇 |
出版年
2024年 | 39篇 |
2023年 | 199篇 |
2022年 | 401篇 |
2021年 | 539篇 |
2020年 | 510篇 |
2019年 | 537篇 |
2018年 | 421篇 |
2017年 | 504篇 |
2016年 | 457篇 |
2015年 | 557篇 |
2014年 | 580篇 |
2013年 | 781篇 |
2012年 | 959篇 |
2011年 | 997篇 |
2010年 | 777篇 |
2009年 | 712篇 |
2008年 | 690篇 |
2007年 | 638篇 |
2006年 | 498篇 |
2005年 | 405篇 |
2004年 | 276篇 |
2003年 | 223篇 |
2002年 | 195篇 |
2001年 | 76篇 |
2000年 | 81篇 |
1999年 | 59篇 |
1998年 | 41篇 |
1997年 | 21篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1971年 | 3篇 |
1962年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 554 毫秒
21.
银条茎尖培养快繁及离体根状茎的诱导 总被引:2,自引:3,他引:2
以银条‘二细一粗’品种为试材, 研究了蔗糖浓度、激素组合对茎尖培养和快速繁殖的影响及温度、光照、蔗糖浓度等因素对根状茎离体诱导的影响。结果表明: 茎尖培养较理想的培养基为MS + 蔗糖4 % + 6-BA 0.5 mg·L - 1 + NAA 0.1 mg·L - 1 , 成苗率可达74.0 %。茎尖增殖较适培养基为MS + 6-BA 3.0 mg·L - 1 + NAA 0.5 mg·L - 1 , 每个外植体平均可产生5.6 个芽。根状茎诱导以MS + 蔗糖10 % + 6-BA 510 mg·L - 1+ CCC 500 mg·L - 1培养基, 20 ℃全黑暗培养效果最好。 相似文献
22.
本文根据作者的观察和测量,对西安市白鹿塬塬区的土壤侵蚀状况进行了研究。研究表明,白鹿塬塬区确定土壤侵蚀的主要依据是土层厚度的变化,并非侵蚀面。塬区侵蚀是塬边侵蚀较强,向塬里侵蚀逐渐减弱。塬面上高地侵蚀弱,低地侵蚀强,暂时性线状流水长期汇集而成的冲沟对黄土塬区土壤的侵蚀更加强烈。气候对土壤侵蚀也有影响,冷干和温湿气候均会产生土壤侵蚀,冷干期侵蚀量比温湿期大,前者侵蚀厚度比后者大7倍多。 相似文献
23.
ZHOU Hua ZHANG Dai-fu SHAN Jiang SU Hai NIU Hui-yan WANG Juan YU Ping QI Wei-gang 《园艺学报》2004,20(12):2261-2264
AIM: To investigate the effects of angiotensin-converting enzyme inhibitors (ACEI), fosinopril, captopril and angiotensin II AT1 antagonists, valsartan on tissue factor (TF) expression on monocytes induced by lipopolysaccharide (LPS). METHODS: Mononuclear leukocytes from normal delivered female umbilical veins were incubated with bacterial LPS in presence or absence of different ACE inhibitors .At the end of incubation, the cells were disrupted by 3 freeze-thaw cycles. TF procoagulant activity was assessed by a one-stage clotting assay. RT-PCR was used to check TF mRNA expression, and GAPDH mRNA was used for parallel assay. RESULTS and CONCLUSION: The results showed that increased expression of TF mRNA induced by LPS was inhibited by fosinopril, captopril and valsartan, respectively, and the procoagualant activity of monocytes was also reduced. 相似文献
24.
Carlos R Sanchez Suzan Murray Richard J Montali Lucy H Spelman 《Journal of zoo and wildlife medicine》2004,35(3):397-399
A 37-yr-old female Asian elephant (Elephas maximus) presented with anorexia, restlessness, and dark-colored urine. Urinalyses showed hematuria, leukocyturia, isosthenuria, proteinuria, granular casts, and no calcium oxalate crystals. Bloodwork revealed azotemia. Urine culture revealed a pure growth of Streptococcus zooepidemicus resistant to sulfamethoxazole-trimethoprim but susceptible to cephalosporins. A presumptive diagnosis of pyelonephritis was made based on bloodwork, urinalysis, and urine culture. The animal was treated with intravenous ceftiofur, and intravenous and per rectum fluids were given for hydration. The elephant's attitude and appetite returned to normal, the abnormal blood parameters resolved, and urinary calcium oxalate crystals reappeared after treatment, supporting presumptive diagnosis. Follow-up ultrasonography revealed an abnormal outline of both kidneys with parenchymal hyperechogenicity and multiple uterine leiomyomas. 相似文献
25.
26.
27.
Juan Daniel Jiménez-Rosales Ricardo Daniel Améndola-Massiotti Juan Andrés Burgueño-Ferreira Rodolfo Ramírez-Valverde Pedro Topete-Pelayo Maximino Huerta-Bravo 《Tropical animal health and production》2018,50(3):531-536
This study aimed to evaluate the hypothesis that mixed sequential grazing of dairy cows and breeding ewes is beneficial. During the seasons of spring–summer 2013 and autumn–winter 2013–2014, 12 (spring–summer) and 16 (autumn–winter) Holstein Friesian cows and 24 gestating (spring–summer) and lactating (autumn–winter) Pelibuey ewes grazed on six (spring–summer) and nine (autumn–winter) paddocks of alfalfa and orchard grass mixed pastures. The treatments “single species cow grazing” (CowG) and “mixed sequential grazing with ewes as followers of cows” (MixG) were evaluated, under a completely randomized design with two replicates per paddock. Herbage mass on offer (HO) and residual herbage mass (RH) were estimated by cutting samples. The estimate of herbage intake (HI) of cows was based on the use of internal and external markers; the apparent HI of ewes was calculated as the difference between HO (RH of cows) and RH. Even though HO was higher in CowG, the HI of cows was higher in MixG during spring–summer and similar in both treatments during autumn–winter, implying that in MixG the effects on the cows HI of higher alfalfa proportion and herbage accumulation rate evolving from lower residual herbage mass in the previous cycle counteracted that of a higher HO in CowG. The HI of ewes was sufficient to enable satisfactory performance as breeding ewes. Thus, the benefits of mixed sequential grazing arose from higher herbage accumulation, positive changes in botanical composition, and the achievement of sheep production without negative effects on the herbage intake of cows. 相似文献
28.
Paula de Aguiar Silva Gleidson Giordano Pinto de Carvalho Aureliano José Vieira Pires Stefanie Alvarenga Santos Douglas dos Santos Pina Robério Rodrigues Silva Carlindo Santos Rodrigues Luis Henrique Almeida de Matos Carlos Emanuel Eiras Daiane Novais-Eiras Wilson Souza Nunes 《Tropical animal health and production》2018,50(4):721-726
In this study, we evaluated the effects of including cassava wastewater in the diet on the feeding behavior of feedlot lambs in 35 male uncastrated Santa Inês × Dorper crossbred lambs at an approximate age of 3 months, with an average live weight of 20.0?±?3.4 kg. Diets were formulated with hay of cassava shoots (roughage) and a concentrate based on corn and soybean, with a roughage:concentrate ratio of 50:50, plus inclusion of cassava wastewater at the levels of 0, 12, 24, 36, or 48 g/kg of the total diet. Feeding behavior was evaluated between the 46th and 52nd days of the experiment. Increasing cassava wastewater levels in the diet reduced (P?<?0.05) the intakes (kg/day) of dry matter and neutral detergent fiber as well as the efficiency of rumination (g/cud and g/h) of dry matter and neutral detergent fiber. The other behavioral parameters were not affected by wastewater inclusion in the diet. Therefore, the inclusion of up to 48 g/kg of cassava wastewater on fresh matter of diets is not recommended for feedlot lambs. 相似文献
29.
肉鸡屠宰加工过程中沙门菌污染定量风险评估 总被引:1,自引:0,他引:1
为了构建肉鸡屠宰加工过程中沙门菌污染定量风险评估模型,分析鸡肉中沙门菌的消长变化规律,明确关键风险防控点,采用2015年部分肉鸡屠宰场沙门菌污染监测和调研数据,构建以烫煺后为评估过程起点,包括净膛、清洗预冷和分割传送的模块化过程风险评估模型,以不同分布描述各变量,并通过@RISK软件模拟运行。结果显示,通过构建的模型模拟屠宰加工后终端鸡肉产品中的沙门菌污染量,90%的可能分布在0~9MPN之间,而依据实际监测数据换算为5.3 MPN,说明模型可信。根据过程中各环节的模拟数据,分析了肉鸡携带的沙门菌消长变化,发现预冷后沙门菌污染总量明显下降,但分割传送后污染总量又有所回升。通过拟合的相关系数分析,明确了传送带上的沙门菌是影响终端鸡肉沙门菌污染的最关键风险点。本研究构建的肉鸡屠宰加工全过程沙门菌定量风险评估模型,可为肉鸡屠宰场沙门菌污染的卫生监管和风险管理提供理论依据。 相似文献
30.
豫南地区野生地被植物资源现状调查与研究 总被引:1,自引:0,他引:1
豫南地区野生地被植物资源丰富,为了在城市绿化中引入新的具有利用价值的种类,对以信阳为中心的河南省南部具有典型立地条件的区域的野生地被植物资源进行了调查。结果表明:筛选统计出野生地被植物56科,359属,822种,其中具有较大开发利用价值的50种。通过对50种野生地被植物中的15种进行利用价值研究得出,随着植物的生态适应性的增强,该种植物同时观赏价值、经济价值也相对增高,在园林应用中可利用价值也越大。 相似文献