全文获取类型
收费全文 | 685篇 |
免费 | 33篇 |
国内免费 | 20篇 |
专业分类
林业 | 44篇 |
农学 | 19篇 |
基础科学 | 42篇 |
96篇 | |
综合类 | 134篇 |
农作物 | 54篇 |
水产渔业 | 33篇 |
畜牧兽医 | 241篇 |
园艺 | 26篇 |
植物保护 | 49篇 |
出版年
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 17篇 |
2019年 | 19篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 22篇 |
2015年 | 19篇 |
2014年 | 22篇 |
2013年 | 33篇 |
2012年 | 25篇 |
2011年 | 32篇 |
2010年 | 34篇 |
2009年 | 36篇 |
2008年 | 37篇 |
2007年 | 33篇 |
2006年 | 43篇 |
2005年 | 34篇 |
2004年 | 27篇 |
2003年 | 23篇 |
2002年 | 32篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 3篇 |
1990年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1973年 | 4篇 |
1928年 | 4篇 |
1925年 | 6篇 |
1924年 | 6篇 |
1905年 | 2篇 |
1902年 | 2篇 |
1899年 | 4篇 |
排序方式: 共有738条查询结果,搜索用时 15 毫秒
731.
Scintigraphy of normal mouse ovaries with monoclonal antibodies to ZP-2, the major zona pellucida protein 总被引:1,自引:0,他引:1
The zona pellucida is an extracellular glycocalyx, made of three sulfated glycoproteins, that surrounds mammalian oocytes. Parenterally administered monoclonal antibodies specific for ZP-2, the most abundant zona protein, localize in the zona pellucida. When labeled with iodine-125, these monoclonal antibodies demonstrate a remarkably high target-to-nontarget tissue ratio and provide clear external radioimaging of ovarian tissue. 相似文献
732.
M. Dean R. Shepherd A. Arvola M. Vassallo M. Winkelmann E. Claupein L. Lähteenmäki M.M. Raats A. Saba 《Journal of Cereal Science》2007
Using a survey, this study investigated public perceptions relating to different healthy grain foods (bread, pasta and biscuits) and how these perceptions are influenced by gender, nationality, base product (staple vs. fun food), type of health claim (general vs. specific) and people's perceptions associated with different production methods. Two thousand and ninety-four (50.4% women, 49.5% men) members of the public from the UK, Italy, Finland and Germany completed the survey questionnaire. The participants were over 18 years of age and were solely or jointly responsible for the family's grocery shopping. 相似文献
733.
B. J. Daniels-Lake R. K. Prange W. Kalt C. L. Liew J. Walsh P. Dean R. Coffin 《American Journal of Potato Research》1996,73(10):469-481
Ozone and 1,8-cineole were investigated as alternatives to isopropyl-n-(3-chloro-phenyl)carbamate (CIPC) to control sprout development of potato (Solatium tuberosum) tubers cv Russet Burbank during long-term storage. Sprout development was similar in ozone-treated and air-stored tubers, but both had much larger and more numerous sprouts than CIPC-treated tubers. Sucrose and reducing sugars in ozone-treated tubers were similar to levels in air-stored potatoes. Fry color was not different among potatoes stored in ozone, air and CIPC. Conversely, potatoes treated with 1,8-cineole did not produce any sprouts during the 25 week study. The fry color of tubers exposed to cineole was darker than either air-stored or CIPC-treated tubers. Sucrose and reducing sugar levels were higher in cineole-treated tubers than in tubers treated with CIPC. 相似文献
734.
Yang Chuanping Liu Guifeng Xu Jiachun Cai Baoming Xia Dean Yang Shuwen Zhang Peigao 《林业研究》1997,8(1):3-9
On the basis of the data of provenance test for 10 years in the total natural range ofLarix olgensis from 10 seeds collection sites, the geographic variation patterns have been made by means of canonical correlation analysis:
(1) The basic variation patterns of growth characters is in vertical gradual change along the elevation gradient as principal,
and gradual change along the latitude as supplement. (2) The Xiaobehu provenance with low elevation and low equivalent latitude
is the good gene resource center ofL. olgensis. It has the genetic characters of rapid growth, high stability and fine timber quality. (3) The synthetical interaction between
water and heat factors is the major factor to produce the variation ofL. olgensis and the temperature is the principal one. (4) Among the genetic variations of geographic population characters, the variation
of growth is the most obvious one, and it could be taken as the main character for provenance division. (5) By allocating
the seeds from the low equivalent latitude region to the northern suitable afforestation areas, the greater genetic gain could
be obtained.
(Responsible Editor: Chai Ruihai) 相似文献
735.
In-house composting involves treating manure where it accumulates on the floor of high-rise, caged layer facilities. This process produces a partially composted material and can aid in house fly (Musca domestica L.) control by generating temperatures in the thermophilic range (≥43°C). Two trials were conducted to determine the effect of material volume and the use of previously composted material (starter) or wheat (Triticum aestivum L.) straw as bulking agents on compost temperatures and material properties. In Trial 1, starter combined with wheat straw or wheat straw alone were added to separate quadrants in a layer building, formed into windrows, and turned biweekly. Temperatures were consistently higher with the starter treatment, but both treatments followed a distinct pattern where temperatures peaked on the day of turning and declined rapidly thereafter. The starter treatment had higher initial volume (0.19 m3 m?1 row) than straw alone (0.13 m3 m?1 row), and maintained proportionately higher volumes throughout the trial. Volume in both treatments increased linearly with time and was correlated with peak compost temperature on the day of turning. Regression analysis indicated that a critical volume of 0.18 m3 m?1 row was required to consistently achieve compost temperatures ≥43°C. In a second trial, starter alone was compared to wheat straw at two rates. Volumes for all treatments initially ranged from 0.20 to 0.28 m3 m?1 row and increased linearly throughout the trial. Temperatures consistently exceeded 43°C on the day of turning. Analysis of the materials from both trials indicated that starter or straw had little effect on %moisture, %carbon, %nitrogen, or carbon:nitrogen ratio of composting materials beyond the first week after windrow establishment. These results indicate that material volume is more important than the use of starter or straw materials as bulking agents to achieve in-house composting temperatures ≥ 43°C. 相似文献
736.
737.
模拟酸雨对假俭草叶绿素荧光特性的影响 总被引:5,自引:0,他引:5
研究模拟酸雨(pH 2.5、pH 3.0)对假俭草叶绿素荧光特性的影响.结果表明:酸雨6 h胁迫引起假俭草PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/F0)、光化学猝灭系数(qP)、PSⅡ电子传递量子产率(ФPSⅡ)、光合电子传递速率(ETR)和非光化学猝灭系数(NPQ)下降,pH 2.5处理比pH 3.0处理的下降幅度大;酸雨处理停止24 h后, Fv/Fm、Fv/F0、qP、ФPSⅡ、ETR、NPQ回升;酸雨处理停止48 h后,回升至接近对照.研究还表明,利用非损伤的叶绿素荧光技术可快速检测草对环境因子变化的响应. 相似文献
738.
为了减少噪声对苹果采摘机器人的目标识别所带来的影响,对含噪苹果图像的分割方法进行了研究。该研究设计一种针对噪声具有鲁棒性的苹果图像分割方法,首先计算苹果图像的三维空间特征点的紧致性函数,用以构造邻近点的相似矩阵实现苹果图像的去噪效果;再利用离群点矩阵拆分并由其他剩余列向量线性表示,对相似矩阵进行离群点调优实现聚类优化,进而提出基于空间特征的谱聚类含噪苹果图像分割的优化算法,旨在提高分割算法的效率和识别准确率。通过对两幅苹果图像添加不同程度的高斯和椒盐噪声(方差分别为0.01、0.05和0.1的高斯噪声和概率为0.01、0.05和0.1的椒盐噪声)进行试验,分别求出谱聚类方法、基于空间特征的谱聚类方法和该文优化方法的苹果目标图像的分割图,并计算三类方法的分割准确率。该文优化方法对于单个苹果受不同噪声影响下的分割准确率均在99%以上,对于重叠苹果的分割准确率均在98%以上,对于所选取的30幅苹果图在方差为0.05的高斯噪声和概率为0.01的椒盐噪声影响下的平均分割准确率为99.014%。结果表明:谱聚类方法受噪声的影响较大;基于空间特征的谱聚类方法的分割效果受噪声的影响较小,但在边界区域仍然有很多错分的像素;优化方法在边界区域的分割要优于基于空间特征的谱聚类方法;在设定的试验条件下,其分割结果准确率相对于基于空间特征的谱聚类方法和传统的谱聚类方法可分别提高5%~6%和9%~25%。在分割效率方面,该文优化方法的分割时间低于传统的谱聚类算法,且与基于空间特征谱聚类方法接近。研究结果为苹果采摘机器人的快速目标识别提供参考。 相似文献