全文获取类型
收费全文 | 2102篇 |
免费 | 141篇 |
国内免费 | 201篇 |
专业分类
林业 | 159篇 |
农学 | 96篇 |
基础科学 | 98篇 |
253篇 | |
综合类 | 1032篇 |
农作物 | 140篇 |
水产渔业 | 96篇 |
畜牧兽医 | 313篇 |
园艺 | 186篇 |
植物保护 | 71篇 |
出版年
2024年 | 27篇 |
2023年 | 53篇 |
2022年 | 88篇 |
2021年 | 92篇 |
2020年 | 72篇 |
2019年 | 69篇 |
2018年 | 68篇 |
2017年 | 84篇 |
2016年 | 70篇 |
2015年 | 103篇 |
2014年 | 94篇 |
2013年 | 126篇 |
2012年 | 136篇 |
2011年 | 171篇 |
2010年 | 174篇 |
2009年 | 178篇 |
2008年 | 160篇 |
2007年 | 162篇 |
2006年 | 108篇 |
2005年 | 86篇 |
2004年 | 74篇 |
2003年 | 52篇 |
2002年 | 62篇 |
2001年 | 70篇 |
2000年 | 42篇 |
1999年 | 8篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1946年 | 1篇 |
排序方式: 共有2444条查询结果,搜索用时 15 毫秒
91.
AIM:To observe the influence of APP17-mer peptide on the learning and memory,and oxidative stress in mitochondria in hipp ocampal neurons of senescence accelerated mouse/prone 10 (SAMP10).METHODS:The 4-month-old SAMP 10s were randomly divided into mod el group and APP17-mer peptide group (the model group+APP17-mer peptide).The se nescence accelerated mouse/resistance1 (SAMR1) were used for normal control.The APP17-mer peptide group was injected with APP17-mer peptide subcutaneously in a dose of 0.34 μg/per mouse,three times a week;while the model group and the control group were injected with saline.After 28 weeks,water maze test was use d to evaluate the learning and memory of these mice.Then hydroxy lamine reactio n and thiobarbituric acid reaction were used to assay the activity of superoxid e dismutase (SOD) and contents of malondialdehyde (MDA) in mitochondria in hippo campal neurons,respectively.RESULTS:(1) The water maze test showed that the full-course swi mming time and numbers of error committed in model group were significantly incr eased as compared with the normal control (P<0.05).The results in APP17-me r peptide treated group were the same as that in normal control group.(2) Compa red with the normal control,the activity of SOD decreased in model group (P <0.01),and the contents of MDA increased (P<0.01).APP17-mer partially re versed the increase in MDA and the decrease in SOD.The content of MDA was lower and the activity of SOD was higher in APP17-mer peptide group than those in mod el group (P<0.05).CONCLUSION:The learning and memory deficit in SAMP10 are observ ed,and the balance of free radical generation/free radical scavenger is impai red.APP17-mer peptide has an antioxidant character and corrects the abnormal ch ange of SOD and MDA,which may be related to its protective effect of learning and memory. 相似文献
92.
AIM: Cinnamyl aldehyde (CA) is one alcohol ingredient derived from Cinnamomum cassia,which is widely used in treating chronic skin wound in Chinese medicine with the curative effect of ‘rescuing YANG’.The purpose of the present study was to investigate the expression of c-Fos,c-Myc proteins at different time points in NIH3T3 treated with CA and explore the possible mechanism of promoting cell proliferation by CA.METHODS: MTT assay was used for observing cell proliferation.Expression of c-Fos and c-Myc proteins in NIH3T3 cells were assessed by immunocytochemistry assay.RESULTS: The cell proliferation was promoted obviously when CA concentration was between 8.8×10-2 μg/L and 8.8×10 μg/L.CA at concentration of 5.5 μg/L significantly induced expression of c-Fos,c-Myc proteins at 2-3 h after the stimulation compared with control group (P<0.01).CONCLUSION: CA increases expression of c-Fos and c-Myc proteins,which may be one of mechanisms for CA to promote NIH3T3 cell proliferation. 相似文献
93.
94.
95.
以小尺度范围内的木兰科、壳斗科和樟科各8种木本植物为研究对象,从分类单元科与种、功能群角度分析了叶功能性状特征及其关联性。结果表明:壳斗科树种的叶柄直径(1.08±0.22)和比叶面积(SLA)(90.87±25.35)显著低于樟科和木兰科,而樟科和木兰科之间差别不明显。叶含氮量在科间没有显著差异。从功能群比较,常绿树种比叶面积(90.10±23.15)显著低于落叶树种(134.65±27.77),但单位叶面积含氮量常绿树种(1.95±0.50)显著高于落叶树种(1.31±0.26)。在不同功能群中,叶面积与叶柄质量有很好的拟合直线关系。叶氮含量仅在常绿树种与其他叶性状有较好的拟合直线关系。叶性状相关性系数大于0.900的有:群落水平物种间叶面积与叶柄质量之间;功能群水平常绿树种叶面积与叶柄直径和叶柄质量间,落叶树种叶柄质量与叶面积和叶柄长间。其他叶性状间也表现不同程度的相关性,表明叶性状之间存在生长发育非同步也即异速生长现象。 相似文献
96.
97.
人工落叶松林降雨截留再分配及其水化学特征 总被引:4,自引:0,他引:4
以凉水国家级自然保护区内的人工落叶松林为研究对象,对其林冠截留再分配和水化学特征变化进行了系统研究,结果表明:(1)一个生长季内(4-9月),人工落叶松林林冠总截留量为109.19 mm,占同期降雨量21.71%,穿透雨量为393.39 mm,占同期降雨量的78.20%;树干茎流量为0.47 mm,占同期降雨量的0.093%;(2)按照各养分元素月平均浓度排序,林外雨为:CaKMgSiMnNaFe,穿透雨为:CaKSiNaMgFeMn,树干茎流为;CaNaMgSiKMnFe,且不同样品按照养分元素浓度稳定度排序为;树干茎流穿透雨林外雨;(3)人工落叶松林养分元素净输入排序为;KMgMnNaFeCaSi,净输入量依次为22.339,2.920,0.856,-0.216,-0.260,-1.280,-2.478 kg/hm2,其中,穿透雨占人工落叶松林(穿透雨+树干茎流)元素输入量的98.23%,树干茎流占1.77%. 相似文献
98.
采用"穗茎注射法"将高粱BTx623基因组DNA导入超级杂交稻亲本9311,获得了高着粒密度的大穗变异系"高粱稻"GLR。用225对In Del分子标记对原始变异株及其自交3代株系与供体和受体进行多态性检测,发现两者与受体9311相比分别有20.4%和10.7%的多态位点,并在原始变异株及其自交3代株系中发现受体9311不存在而与供体高粱同源的片段,从分子水平证明了供体高粱DNA片段向受体水稻基因组的转移。比较分析5个已克隆的穗部性状相关基因在变异系与受体9311中的多态性,发现DEP3、D1和Gnla 3个基因共存在35个SNP和6个In Del,其中9个SNP和2个In Del位于外显子。 相似文献
99.
以信息农业推进农业产业化建设 总被引:2,自引:0,他引:2
信息化已成为各个行业竞相发展的战略产业。信息化对农业影响已日趋激烈,用信息化装备农业成为农业产业化发展的重大课题。农业产业化依赖于信息化,信息化的发展又催生农业产业化质的跨越。 相似文献
100.
As an important digestive enzyme gene, the serine protease gene AlSP 3 plays a key role in Apolygus lucorum for digesting conventional cotton. To understand the effect of different temperatures on the expression level of AlSP 3, we analyzed the expression patterns of AlSP 3 in A. lucorum reared at different temperatures using real-time polymerase chain reaction. The results showed that at the normal temperature of 24 ℃, the expression of AlSP 3 in A .lucorum at different nymphal stages was similar. The expressions of AlSP 3 in the female adult at the pre-mating stage and the male adult at post-mating stage were 19.71- and 7.16-fold higher than their control at the 1st nymphal stage, respectively, which were significantly higher than at any other stages. However, expression in the 4th to 5th A. lucorum at the nymphal stage increased with rising temperature in the range of 21~30 ℃. At 30 ℃, the expression of AlSP 3 in the 2nd to 5th A. lucorum was the highest. The expression levels of AlSP 3 in adult A. lucorum reared at different temperatures during the new emergence and pre-mating stages were significantly higher than that of the control reared at 24 ℃ (P < 0.01), while the expression during the post-mating stage at 18℃ was higher than that at other temperatures. When incubated at extreme temperatures (4 ℃ and 40 ℃), the expression of AlSP 3 in female and male adult A. lucorum was significantly higher than that at 24 ℃ (P < 0.01). Taken together, our results showed that the external environment temperature and the internal stage of A. lucorum or its sex all had significant effects on the expression of AlSP 3 in A. lucorum (P < 0.01), and that there was some interactions between them. Therefore, AlSP 3 is very important for the female adult A. lucorum to obtain nutrition at the early stages and temperature is an important limiting factor for the expression of AlSP 3. 相似文献