全文获取类型
| 收费全文 | 4016篇 |
| 免费 | 1417篇 |
| 国内免费 | 436篇 |
专业分类
| 林业 | 60篇 |
| 农学 | 663篇 |
| 基础科学 | 432篇 |
| 508篇 | |
| 综合类 | 1540篇 |
| 农作物 | 572篇 |
| 水产渔业 | 57篇 |
| 畜牧兽医 | 1592篇 |
| 园艺 | 163篇 |
| 植物保护 | 282篇 |
出版年
| 2025年 | 105篇 |
| 2024年 | 111篇 |
| 2023年 | 139篇 |
| 2022年 | 298篇 |
| 2021年 | 289篇 |
| 2020年 | 239篇 |
| 2019年 | 246篇 |
| 2018年 | 177篇 |
| 2017年 | 182篇 |
| 2016年 | 190篇 |
| 2015年 | 242篇 |
| 2014年 | 293篇 |
| 2013年 | 302篇 |
| 2012年 | 479篇 |
| 2011年 | 473篇 |
| 2010年 | 350篇 |
| 2009年 | 366篇 |
| 2008年 | 201篇 |
| 2007年 | 375篇 |
| 2006年 | 351篇 |
| 2005年 | 133篇 |
| 2004年 | 84篇 |
| 2003年 | 30篇 |
| 2002年 | 29篇 |
| 2001年 | 27篇 |
| 2000年 | 16篇 |
| 1999年 | 24篇 |
| 1998年 | 24篇 |
| 1997年 | 14篇 |
| 1996年 | 18篇 |
| 1995年 | 4篇 |
| 1994年 | 2篇 |
| 1991年 | 3篇 |
| 1989年 | 1篇 |
| 1988年 | 2篇 |
| 1987年 | 15篇 |
| 1986年 | 15篇 |
| 1985年 | 1篇 |
| 1984年 | 1篇 |
| 1982年 | 1篇 |
| 1981年 | 2篇 |
| 1980年 | 1篇 |
| 1978年 | 1篇 |
| 1977年 | 1篇 |
| 1963年 | 3篇 |
| 1962年 | 2篇 |
| 1956年 | 6篇 |
| 1955年 | 1篇 |
排序方式： 共有5869条查询结果，搜索用时 420 毫秒
1.
我国地理标志保护问题探析 总被引：4，自引：0，他引：4
加强地理标志保护和管理,是我国实施品牌战略,促进农村经济发展和农民增收面临的新课题。文章分析了地理标志保护制度兴起的国际背景和原因,并从认识、立法和管理层面对我国地理标志保护中存在的问题进行了探讨,提出了加强政府监管、提高生产者保护意识、建立产业内部自我组织和协调机制等对策建议。 相似文献
2.
Xiang ZHANG Qiu-zhi RUI Pan-pan LIANG Chen-hua WEI Guo-qiang DENG Yuan CHEN Yuan CHEN Zhao-di DONG De-hua CHEN 《农业科学学报》2018,17(9):1991-1998
This study was conducted to investigate the effects of alternating high temperature on Cry1Ac protein content on Bt cotton cultivars Sikang 1(SK-1,a conventional cultivar)and Sikang 3(SK-3,a hybrid cultivar).In 2011 and 2012,cotton plants were subjected to high temperature treatments ranging from 32 to 40℃ in climate chambers to investigate the effects of high temperature on boll shell insecticidal protein expression.The experiments showed that significant decline of the boll shell insecticidal protein was detected at temperatures higher than 38℃ after 24 h.Based on the results,the cotton plants were treated with the threshold temperature of 38℃ from 6:00 a.m.to 6:00 p.m.followed by a normal temperature of 27℃ during the remaining night hours(DH/NN)in 2012 and 2013.These treatments were conducted at peak boll growth stage for both cultivars in study periods of 0,4,7,and 10 d.Temperature treatment of 32℃ from 6:00 a.m.to 6:00 p.m.and 27℃ in the remaining hours was set as control.The results showed that,compared with the control,after the DH/NN stress treatment applied for 7 d,the boll shell Cry1Ac protein content level was significantly decreased by 19.1 and 17.5% for SK-1 and by 15.3 and 13.7% for SK-3 in 2012 and 2013,respectively.Further analysis of nitrogen metabolic physiology under DH/NN showed that the soluble protein content and the glutamic pyruvic transaminase(GPT)activities decreased slightly after 4 d,and then decreased sharply after 7 d.The free amino acid content and the protease content increased sharply after 7 d.The changes in SK-1 were greater than those in SK-3.These results suggest that under DH/NN stress,boll shell Cry1Ac protein content decline was delayed.Reduced protein synthesis and increased protein degradation in the boll shell decreased protein content,including Bt protein,which may reduce resistance to the cotton bollworm. 相似文献
3.
Guang‐Min Yu Yue Wu Xian‐Long Wang Shuan Zhao Teruo Maeda Shen‐Ming Zeng 《Animal Science Journal》2018,89(4):640-647
When European Union regulations restricted the use of estrogenic compounds in food‐producing animals, refined hormonal protocols were no longer applicable for anovulatory cows. However, Ovsynch and its adaptations are routinely and uniformly applied to all cows regardless of ovarian function. To evaluate their efficacy on anovulatory cows, 143, 147 and 144 anovulatory cows received Ovsynch, Presynch and G6G protocols, respectively. In comparison, 150 cyclic cows were bred without using a synchronized protocol. Results showed that cows in the Presynch group had luteolysis responding to the last prostaglandin F2α (PGF2α) injection greater than the Ovsynch group. The serous progesterone levels at the first gonadotropin‐releasing hormone of Ovsych and the last PGF2α injection was greater in the G6G group than the other two hormonal treatment groups. Concentrations of Ca2+ and total protein in cervical mucus in all three hormone‐treated groups before artificial insemination (AI) were significantly different from the controls. The G6G group obtained a greater pregnancy rate compared with Ovsynch and Presynch, but significantly less than the controls. For open cows in the Ovsynch group, estrus rate within 24 days after the first AI was significantly less than the controls. In conclusion, the G6G treatment resulted to better reproductive performance in anovulatory cows. 相似文献
4.
YANG Yan-yan ZHU Li-qian YANG Ji-fei TENG Man CAI Shu-jun WANG Li LUO Jun DENG Rui-guang ZHANG Gai-ping 《中国农业科学(英文版)》2010,9(2):294-298
This article aims to establish an efficient assay for screening monoclonal antibodies （McAbs） against the membrane proteins of chicken embryo fibroblast （CEF） for further studies of the cellular receptors of infectious bursal disease virus （IBDV）. McAbs against the membrane proteins of CEF were prepared by cell fusion. The monolayer CEF pre-incubated with the CEF-specific McAbs for 2 h were infected with IBDV and incubated with F22-EA6-biotin postinfection. Then, the cells were reacted with streptavidin-horseradish peroxidase （HRP） and finally stained by 3-amino-9-ethylcarbazole （AEC）. The inhibitive percentage of IBDV infection was calculated by counting the IBDV-infected cells to determine the inhibition efficiency of the CEF-specific McAbs. Compared with the control cells, the IBDV-infected cells pretreated with CEF-specific antibody significantly decreased; supernatant fluids of a total of 768 hybridomas were analyzed. The results of immunohistochemistry assays showed that six of them （1A5, 1H11, 2B 12, 3G1, 4D10, and 4B8） have the abilities to block the infection of IBDV to CEF, among which 4B8 can perfectly block the infection. This novel method is a sensitive and specific assay for the screening of CEF membrane protein-specific McAbs, which can block the infection of IBDV to CEF, and these McAbs can be used for the further investigations of the cellular receptors of IBDV. 相似文献
5.
针对目前抽油机井系统效率分析中光杆功率的计算中存在的问题.提出一种简单实用且具有较高精度的计算方法,并在现场生产中进行推广应用,为精细分析抽油机井系统效率提供了一种计算分析方法. 相似文献
6.
《Agricultural Water Management》2005,71(2):131-143
Soil water and salinity are crucial factors influencing crop production in arid regions. An autumn irrigation system employing the application of a large volume of water (2200–2600 m3 ha−1) is being developed in the Hetao Irrigation District of China, since the 1980s with the goal to reduce salinity levels in the root zone and increase the water availability for the following spring crops. However, the autumn irrigation can cause significant quantities of NO3− to leach from the plant root zone into the groundwater. In this study, we investigated the changes in soil water content, NO3–N and salinity within a 150 cm deep soil profile in four different types of farmlands: spring wheat (FW), maize (FM), spring wheat–maize inter-planting (FW–M) and sunflower (FS). Our results showed that (1) salt losses mainly occurred in the upper 60 cm of the soil and in the upper 40 cm for NO3–N; (2) the highest losses of salt and NO3–N could be observed in FW, whereas the lowest losses were found in FW–M.NO3–N concentration, pH and electrical conductivity (EC) in the groundwater were also monitored before and after the autumn irrigation. We found that the autumn irrigation caused the groundwater concentration of NO3–N to increase from 1.73 to 21.6 mg L−1, thereby, exceeding the standards of the World Health Organization (WHO). Our results suggest that extensive development of inter-planting tillage might be a viable measure to reduce groundwater pollution, and that the application of optimized minimum amounts of water and nitrogen to meet realistic yield goals, as well as the timely application of N fertilizers and the use of slow release fertilizers can be viable measures to minimize nitrate leaching. 相似文献
7.
大豆降压肽的生产工艺研究 总被引：1，自引：0，他引：1
应用4种蛋白酶酶解大豆分离蛋白,研究其水解效果和降压活性。实验选定碱性蛋白酶为生产大豆降压肽的最适酶,并对其酶解条件进行了优化,确定生产大豆降压肽的最佳条件为：温度60℃,pH8.0,底物浓度4%,碱性蛋白酶浓度4%,水解度14.4%,优化后的ACE抑制率可达到84.1%。 相似文献
8.
9.
为了提高轴流泵非设计工况的运行效率,拓宽轴流泵高效区范围,对轴流泵进行多工况优化设计。结合轴流泵段的模型试验,采用数值模拟手段和数值优化技术,改变叶轮的几何设计参数。对轴流泵叶片进行参数化建模,再对轴流泵叶轮结果进行泵段数值模拟。最后以轴流泵段3个流量工况点的加权平均效率最高,扬程为约束条件,改变轴流泵叶轮的设计参数,对轴流泵段进行多工况优化设计。研究结果表明:优化后轴流泵段效率曲线较初始泵段明显变宽,其中小流量工况点效率提高约2.6%,设计工况点效率提高约0.5%,大流量工况点效率提高最多,约7.4%,而对于扬程变化范围较小,各工况点扬程均能满足运行要求,大大降低了运行成本,缩短了优化设计的周期。同时采用CFD计算的学科分析方式,结合试验研究的手段取代人工凭经验的优化方式,证实了轴流泵段多工况优化设计的可靠性、高效性。该研究将为泵站的高效运行和轴流泵的多工况优化设计提供参考。 相似文献
10.
为了分析苯丙氨酸解氨酶基因(CsPAL)在黄瓜侵染白粉菌中的转录应答响应,对CsPAL基因(GenBank No.JN 675927)及其启动子进行了克隆与序列分析,再利用qRT-PCR技术分析了该基因在黄瓜高抗白粉病品种‘Jin5-508’接种白粉菌后不同时间的相对表达量。结果表明:CsPAL基因全长2 142 bp,编码713个氨基酸;推测CsPAL蛋白存在于细胞质中;系统发育进化树分析发现与拟南芥基因进化距离较近;启动子克隆及序列分析显示该基因能够响应真菌的侵染;组织特异性表达发现CsPAL在在叶片中的表达量最高;qRTPCR结果表明‘:Jin5-508’叶片在接菌16 h内,CsPAL基因的相对表达量于对照间无显著差异;接菌16 h后,CsPAL基因表达量迅速上升,显著高于对照,并在24 h达到最大值;接菌48 h后,CsPAL基因的表达量逐渐下降,但在96 h内仍显著高于相应对照的表达量。综上所述,黄瓜CsPAL基因为白粉菌侵染响应基因,可能与黄瓜对白粉病的抗性具有一定的相关性。 相似文献