全文获取类型
收费全文 | 555篇 |
免费 | 77篇 |
国内免费 | 21篇 |
专业分类
林业 | 14篇 |
农学 | 113篇 |
基础科学 | 11篇 |
15篇 | |
综合类 | 108篇 |
农作物 | 19篇 |
水产渔业 | 3篇 |
畜牧兽医 | 348篇 |
园艺 | 16篇 |
植物保护 | 6篇 |
出版年
2024年 | 1篇 |
2023年 | 22篇 |
2022年 | 20篇 |
2021年 | 20篇 |
2020年 | 45篇 |
2019年 | 27篇 |
2018年 | 21篇 |
2017年 | 22篇 |
2016年 | 28篇 |
2015年 | 30篇 |
2014年 | 31篇 |
2013年 | 33篇 |
2012年 | 33篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 17篇 |
2008年 | 24篇 |
2007年 | 25篇 |
2006年 | 14篇 |
2005年 | 16篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 1篇 |
排序方式: 共有653条查询结果,搜索用时 15 毫秒
101.
van den Hoven R Duvigneau JC Hartl RT Gemeiner M 《Veterinary research communications》2006,30(8):921-928
On four occasions, four horses with heaves and four horses with small airway inflammatory diseases inhaled 0.9% saline based
aerosol mixtures with or without lipopolysaccharides (LPS). Prior to the first saline and LPS inhalation, horses were untreated,
while three and a half days prior to the third and forth inhalation horses had received 0.8 μ g/kg clenbuterol intravenously
twice daily.
The messenger RNA (mRNA) expression of tumour necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10 and
interferon- γ (IFN- γ) was investigated by RT-PCR, all of which were expressed in the white blood cells of samples collected.
Inhalation of LPS only changed the cytokine expression profile of IL-10, IL-4 and TNF-α mRNA which were higher after challenge
with LPS. However in those horses that were treated with clenbuterol the LPS-induced IL-10 mRNA expression was shown to be
suppressed. Further changes in IL-4 and TNF-α were not significant. Thus the results of this study indicated that clenbuterol
can modulate the expression of IL-10 mRNA in peripheral white blood cells in those horses with small airway diseases that
have been exposed to LPS.
van den Hoven, R., Duvigneau, J.C., Hartl, R.T. and Gemeiner, M., 2006. Clenbuterol affects the expression of messenger RNA
for interleukin 10 in peripheral leukocytes from horses challenged intrabronchially with lipopolysaccharides. Veterinary Research
Communications, 30(8), 921–928 相似文献
102.
谌新年 《中南林业科技大学学报(自然科学版)》2007,27(3):87-90
讨论了时滞recurrent神经网络模型的全局渐近稳定性,通过构造适当的Lyapuov函数,利用线性矩阵不等式,给出了一类常时滞recurrent神经网络的新的充分条件,所获的稳定性条件是时滞相关的,稳定性判别条件更宽松.最后通过一个实例说明方法的可行性. 相似文献
103.
Laryngeal mask airway insertion requires less propofol than endotracheal intubation in dogs 总被引:1,自引:0,他引:1
OBJECTIVE: To compare the doses of propofol required for insertion of the laryngeal mask airway (LMA) with those for endotracheal intubation in sedated dogs. STUDY DESIGN: Randomized prospective clinical study. Animals Sixty healthy dogs aged 0.33-8.5 (3.0 +/- 2.3, mean +/- SD) years, weighing 2.2-59.0 (23.4 +/- 13.6, mean +/- SD) kg, presented for elective surgery requiring inhalation anaesthesia. METHODS: Animals were randomly assigned to receive either a LMA or an endotracheal tube. Pre-anaesthetic medication was intravenous (IV) glycopyrrolate (0.01 mg kg(-1)) medetomidine (10 microg kg(-1)) and butorphanol (0.2 mg kg(-1)). Repeated IV propofol injections (1 mg kg(-1) in 30 seconds) were given until LMA insertion or endotracheal intubation was achieved, when the presence or absence of laryngospasm, the respiratory rate (fr) and the total dose of propofol used were recorded. RESULTS: The total propofol dose (mean +/- SD) required for LMA insertion (0.53 +/- 0.51 mg kg(-1)) was significantly lower than for endotracheal intubation (1.43 +/- 0.57 mg kg(-1)). The LMA could be inserted without propofol in 47% of dogs; the remainder needed a single 1 mg kg(-1) bolus (n = 30). Endotracheal intubation was possible without propofol in 3.3% of the dogs, 47% needed one bolus and 50% required two injections (n = 30). The f(r) (mean +/- SD) was 18 +/- 6 and 15 +/- 7 minute(-1) after LMA insertion and intubation, respectively. CONCLUSION AND CLINICAL RELEVANCE: Laryngeal mask airway insertion requires less propofol than endotracheal intubation in sedated dogs therefore propofol-induced cardiorespiratory depression is likely to be less severe. The LMA is well tolerated and offers a less invasive means of securing the upper airway. 相似文献
104.
黄山花楸种子休眠影响因素 总被引:3,自引:0,他引:3
对黄山花楸(Sorbus amabilis)种子休眠的解剖结构基础与影响条件进行了试验研究。结果表明:黄山花楸种子由种皮和胚2部分组成。胚形态发育完全,种皮表面覆一层角质层,胚根端和子叶端的种皮细胞排列明显比中间部位密集;种子透水性障碍不明显而透气性障碍显著;未处理的完整种子萌发率为0,种胚、种胚去除不同量子叶处理萌发率为86.67%~96.67%;种子去除不同部位种皮的萌发率在90%以上。表明黄山花楸种胚无休眠,种皮透性、特别是透气性对休眠有一定影响,种子休眠主要是种皮的机械障碍引起的物理休眠。 相似文献
105.
玉米轮选系产量配合力和抗病性研究 总被引:1,自引:0,他引:1
研究了东农群体—1的第一轮选出的自交系和组成该群体的较好原始亲本的产量配合力和抗大斑病能力.结果表明,轮选系的一般配合力效应和抗大斑病能力均优于较好原始亲本,且差异达到0.05的显著水平.也证明了用轮回选择法提高玉米自交系的配合力和抗病能力很有效。 相似文献
106.
中国特色的玉米商业育种体系构建 总被引:5,自引:4,他引:1
商业育种理念是将公司的整个研发体系视为一条或多条生产流水线,将功能联系密切的研发过程集中起来,形成相对独立的研发管理模块,实现研发流水线的专业化、规模化和工业化,从而极大地提高研究效率,为公司获得市场份额和赚取利润提供基础。在这样的管理理念下,一套功能健全的育种技术体系能够确保研发流水线的顺利实施。综述玉米商业育种的管理理念和技术体系基础上,结合中国种业的发展现状,提出具有中国特色的玉米商业育种体系,即集中有限的资金建立面向全社会的、高起点大规模的研发和服务平台,实现中国种业行业的跨越式发展。 相似文献
107.
Blackspot, caused by Didymella pinodes (Berk. & Blox.)Vestergr., is one of the most important diseases of field pea, causing significant reduction in seed yield and quality in southern Australia and in other parts of the world. Development of resistant germplasm has been slow because of the low level of resistance found in the available germplasm, poor reliability of screening methods and the polygenic nature of inheritance. Crosses were made between agronomically suitable lines and resistant germplasm from different sources. Their progeny were advanced through the single seed descent method and single plants were selected at F4/F5. The F4/F5 derived lines were screened against blackspot in the field under disease pressure and evaluated for grain yield at multilocations over 2 years. Despite the low level of resistance in the parental germplasm, the level of resistance has increased significantly in the new germplasm. Many of the resistant lines were late and low yielding, but lines with higher resistance and early flowering and high yield potential were also identified indicating that the disease resistance, adaptation and yield potential can be combined. However, the resistance identified in this study is only partial and suitable agronomic practices may need to be supplemented to minimise the yield loss and enhance the benefits of this partial resistance. 相似文献
108.
Laan TT Bull S van Nieuwstadt RA Fink-Gremmels J 《Veterinary research communications》2006,30(6):623-635
β-Agonists have been shown to display anti-inflammatory properties in several experimental models. The aim of this study was
to investigate the anti-inflammatory properties of clenbuterol (CB), administered either intravenously or by aerosol, in comparison
with fluticasone propionate (FP) in recurrent airway obstruction (RAO)-susceptible horses. Eight horses, of which five were
known to be susceptible to RAO, underwent an inhalation challenge with Aspergillus fumigatus (AF) antigen and were treated with CB intravenously, CB by aerosol, or FP by aerosol. Twenty-four hours after the challenge,
bronchoalveolar lavage was performed, the total and differential cell counts were assessed, and cytokines were measured in
isolated alveolar macrophages. After challenge with AF, RAO-susceptible horses showed an increase in total cell count, based
on an increase in macrophages and lymphocytes, which was inhibited by treatment with intravenous CB, aerosolized CB and aerosolized
FP. Neutrophil ratios were decreased when treated with aerosolized CB and FP. Expression of interleukin (IL)-1β and IL −8
was significantly increased after AF challenge .Interleukin −1β was significantly decreased following treatment with intravenous
CB, aerosolized CB and aerosolized FP, whereas only FP decreased the expression of IL-8. These data suggest that the anti-inflammatory
property of CB provide new opportunities in the therapeutic intervention of early inflammation in RAO. 相似文献
109.
〔摘要〕目的研究傍康汤对复治性肺结核阴虚毒疲证患者T淋巴细胞的影响、方法将%例阴虚毒疲型复治
性肺结核患者随机分为两组:治疗组48例和对照组48例,并设立正常组48例;对照组采用西医常规治疗,治疗组
在西医常规治疗基础上加服傍康汤,2周为1个疗程,共治疗12个疗程〔观察两组临床疗效及对CD,'',CD,'',CDH''1''
淋巴细胞、CD,''/CDH+比值的影响〔结果治疗组总有效率为89.60Io,与对照组66.7%比较,差异有显著统计学意义(P<
0.01);两组CD,'',CDH''1''淋巴细胞、C D,''/C DH+比值治疗前与正常组比较有显著差异}P<0.01),治疗后与治疗前比较
C D,'' T淋巴细胞、CD,''/CDH+比值明显升高,CDH'' T淋巴细胞则明显卜降,差异有统计学意义(P<0.05 ) ;治疗后治疗组
CD,'',CD,''/CDH''比值的升高、CDH''的h降均优于对照组(P<0.05 )〔结论傍康汤治疗阴虚毒疲型复治性肺结核疗效确
切,其机制可能是通过改善患者T淋巴细胞免疫功能而起作用、 相似文献
110.
运轮1号玉米群体轮回选择改良效果 总被引:1,自引:1,他引:0
种质资源遗传基础狭窄是制约玉米育种的重要因素,而群体轮回选择是拓宽玉米资源遗传多样性的重要方法。以具有中国reid 血缘的8 个自交系组成的群体和美国坚秆种质群体BSSS 杂交后经过一轮混合授粉形成运轮1 号玉米群体。3 轮混合选择后,以昌7-2 为测验种分析了运轮1号群体的产量性状的配合力。结果表明,群体内单株间产量配合力差异显著,遗传变异较丰富。从138 个测交种中筛选出20 个较优良的对应自交单株作为新一轮轮回选择的亲本。预计新一轮合成群体产量配合力将提高11.6%,灌浆脱水速率较对照优越,其他农艺性状也得到相应改良。 相似文献