全文获取类型
收费全文 | 20302篇 |
免费 | 1276篇 |
国内免费 | 3555篇 |
专业分类
林业 | 921篇 |
农学 | 3502篇 |
基础科学 | 582篇 |
2289篇 | |
综合类 | 8193篇 |
农作物 | 4886篇 |
水产渔业 | 337篇 |
畜牧兽医 | 2474篇 |
园艺 | 1336篇 |
植物保护 | 613篇 |
出版年
2024年 | 136篇 |
2023年 | 405篇 |
2022年 | 610篇 |
2021年 | 710篇 |
2020年 | 685篇 |
2019年 | 812篇 |
2018年 | 737篇 |
2017年 | 741篇 |
2016年 | 1182篇 |
2015年 | 1333篇 |
2014年 | 1446篇 |
2013年 | 1466篇 |
2012年 | 1523篇 |
2011年 | 1330篇 |
2010年 | 1202篇 |
2009年 | 1180篇 |
2008年 | 1090篇 |
2007年 | 1302篇 |
2006年 | 1232篇 |
2005年 | 1033篇 |
2004年 | 635篇 |
2003年 | 493篇 |
2002年 | 442篇 |
2001年 | 401篇 |
2000年 | 429篇 |
1999年 | 293篇 |
1998年 | 306篇 |
1997年 | 275篇 |
1996年 | 232篇 |
1995年 | 227篇 |
1994年 | 211篇 |
1993年 | 203篇 |
1992年 | 142篇 |
1991年 | 130篇 |
1990年 | 139篇 |
1989年 | 107篇 |
1988年 | 74篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 24篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1963年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
AIM: To explore the clinical significance of Krüpple-like factor 15 (KLF15) protein expression in the patients with lung adenocarcinoma for exploring the therapeutic and prognositic biomarkers of lung cancer. METHODS: Four cases of lung adenocarcinoma tissues and matched adjacent tissues were collected from our hospital, and the expression of KLF15 protein in these tissues was analyzed by Western blot. At the same time, 72 cases of archived paraffin-embedded samples and clinical data of the patients with lung adenocarcinoma were also collected. The KLF15 protein expression in the archived paraffin-embedded lung adenocarcinoma samples was detected by immunohistochemical staining. The correlations between KLF15 protein expression and clinical characteristics of the patients including prognosis were also analyzed. In addition, the KLF15 protein was up-regulated in A549 cells, and then the effects of KLF15 protein on the viability of the cells were measured by CCK-8 assay. RESULTS: The protein expression of KLF15 in the 4 cases of lung adenocarcinoma tissues was significantly lower than that in matched paracancerous tissues. Fifty-three cases of lung adenocarcinoma specimens showed low expression or no expression of KLF15 protein in total 72 cases (73.6%). The 5-year survival rate of the patients with high expression of KLF15 protein in their specimens was higher than that of the patients with the low expression of KLF15 protein (P<0.01), and the expression of KLF15 protein was significantly correlated with the pathological staging (P<0.01) and T stage (P<0.01) of the patients with lung adenocarcinoma. Furthermore, the low expression of KLF15 protein was an important poor prognostic indicator of the patients. Up-regulation of KLF15 protein in the A549 cells significantly inhibited the growth of the cells. CONCLUSION: KLF15 inhibits the growth of lung adenocarcinoma cells. It could be used as a therapeutic target and a prognostic biomarker for the patients with lung adenocarcinoma. 相似文献
102.
103.
104.
为进一步探究春化基因VRN1在小麦发育进程中的功能,利用荧光定量PCR分析了VRN1基因在不同发育特性小麦品种新春2号、京841中的表达情况。结果表明,随着生育进程的推进,VRN1基因在新春2号叶片和茎尖中表达量均呈上升趋势,VRN1基因在京841叶片中呈波动上升趋势,在茎尖中表达量趋于0;以p FGC5941载体为基础构建含有VRN1反向重复序列的RNA干扰载体,利用农杆菌介导的茎尖转化法转化新春2号获得了再生植株,并通过PCR法检测获得了转基因阳性植株,为从分子水平上实现小麦发育特性遗传改良和创育小麦新种质奠定了基础。 相似文献
105.
106.
湘紫薯174 是以浙紫薯1 号为母本、浙紫薯3 号为父本杂交选育而成的食用型紫心甘薯新品种,薯块纺锤形,薯皮
紫红色,薯肉紫色,结薯较集中整齐,单株结薯4~5 个,大中薯率82.7% 以上,熟食味好,抗黑斑病,中抗根腐病、茎线
虫病和薯瘟病;每667 m2 鲜薯产量1 913~2 359 kg,薯干产量549~736 kg;花青素含量为714.5 mg · kg-1(FW)。适宜在湖
南、湖北、江西、江苏、浙江等地春夏薯区种植。 相似文献
107.
Eleven grape cultivars were analysed to explore the variety differences of fresh grape phenolic profiles. The results showed that free phenolics were predominant in grape skins and pulps, and showed the higher antioxidant activities than bound. In 11 cultivars, Muscat Kyoho extracts had the highest total phenolic content in skins(10.525 mg GAE g~(–1) FW) and pulps(1.134 mg GAE g~(–1) FW), and exhibited the highest DPPH radical scavening capacity(EC_(50)=11.7 μg mL~(–1)) and oxygen radical absorbance capacity(ORAC) value(190.57 μmol TE g~(–1) FW) of free phenolic in skin. In addition, the most abundant phenolics in grape skins were found to be flavonoids such as kaempferol in Kyoho skin(541.2 μg g~(–1) FW), rutin, catechin and epicatechin in Muscat Kyoho skin(262.3, 86.3 and 70.0 μg g~(–1) FW, respectively). Furthermore, the principal component analysis showed a strong difference of phenolic profiles with the cultivars, existing forms and distributions. Pearson correlation coefficient analysis showed a significant linear correlation between total phenolic content and antioxidant activity(P0.05). Therefore, both skins and pulps were rich sources of bioactive phenolic compounds, and Muscat Kyoho was the ideal source among all samples. 相似文献
108.
本研究旨在为科学布局高标准农田建设项目提供技术支持。从分析建设适宜性和空间稳定性入手,提出了基于耦合协调度模型和冷热点分析的项目区遴选方法,并在吉林省舒兰市进行实证研究。结果表明:舒兰市高标准农田建设潜力较大,高适宜区和中适宜区合占耕地总面积的74.91%,主要分布在北部乡镇;空间稳定性与建设适宜性的空间分布大致相同,整体呈现“北部高于南部”的特征;高标准农田建设呈现明显的“北部易于南部”特征,其中优良协调类占耕地总面积的52.92%,主要分布在平安镇、金马镇、七里乡、开原镇、水曲柳镇和天德乡等,该类耕地自然禀赋较好、基础设施完备,并且与城镇、交通干线有一定距离,建设占用的可能性较小,高标准农田建设难度最小;高标准农田建设适宜性和空间稳定性耦合协调度的热点区主要分布在法特镇、莲花乡、天德乡、平安镇、七里乡等北部乡镇,是高标准农田项目的优先选择区域。结合研究区实际,确定舒兰市“十三五”期间高标准农田建设区总面积10828.89 hm 2。 相似文献
109.
青海省农业农村现代化发展水平研究 总被引:7,自引:4,他引:3
实现农业农村现代化是乡村振兴战略的根本目标,农业农村现代化的快速推进对经济社会可持续发展具有非常重要的意义。以青海省为研究对象,从农业现代化和农村现代化2个层面构建一套包含10项准则、42项具体指标的农业农村现代化评价指标体系,并对2006—2016年青海省农业农村现代化发展水平进行测评,探讨近年来青海省农业农村现代化发展的趋势、短板和不足。结果表明:青海省农业农村现代化发展指数从2006年的0.264到2016年的0.401,年均增长0.014,总体发展水平越来越好;农业农村现代化达标率从2006年的31%到2016年的44%,达标程度为中等。从农业现代化和农村现代化2个层面来看,农业现代化发展水平及达标率要高于农村现代化,但农村现代化发展水平及达标率的增速要高于农业现代化。青海省农业农村现代化的难点是改善农村环境;重点是提高农民收入和完善农业经营体系;每千人拥有的农业科技人员、农林牧渔服务业产值占比、农业投资占农村总投资比重和每万人拥有文化站数4项指标是青海省农业农村现代化的最主要短板。鉴于此,青海省要快速推进农业农村现代化,就必须加快制度创新,改善农村生态环境;加快农业政策转型,强化有效支持力度;加快农业科技创新力度,提升科技驱动能力;优先安排农村公共服务投入,实现城乡协调发展。 相似文献
110.
AIM: To observe the treatment effect and its immune regulation of human amnion epithelial cells (hAECs) on Alzheimer's disease (AD)-like pathology rat model. METHODS: The hAECs were isolated from amnion with trypsin digestion, and the phenotype of hAECs was analyzed by flow cytometry. SD rats (n=48) were randomly divided into sham control group, model group, medium group and hAECs group. AD-like pathology rat model was induced by bilateral intraventricular injection of lipopolysaccharide (LPS). hAECs (5×105) were injected into the hippocampus of the AD-like pathology rats. At 2 weeks after transplantation, the animals were tested by Morris water maze to observe the function of learning and memory. The pathological change of the brain was observed by HE staining. The expression of amyloid β-protein 42(Aβ42) and Tau protein and the level of acetylcholine (ACh) in the injury brain were determined by immunohistochemistry. The survival and differentiation of hAECs in the hippocampus were measured by immunofluorescent technique. The percentages of lymphocyte subsets in the peripheral blood mononuclear cells were analyzed by flow cytometry. The contents of serum cytokines were detected by cytometric bead array. RESULTS: Compared with model group and medium group, hAECs group showed shortened escape latency (P<0.01), increased frequency of going through the platform (P<0.05), reduced loss of hippocampal neurons, decreased expression of Tau protein and Aβ42 in the hippocampus (P<0.05), increased ACh level in the hippocampus (P<0.05), decreased percentages of Th1 and Th17 subsets, increased percentages of Th2 and Treg cells (P<0.05), decreased concentrations of IFN-γ and IL-2 in the serum, and increased concentration of IL-4(P<0.05). CONCLUSION: hAECs improve the cognitive learning and memory function and alleviate pathologic damage of hippocampus through immune regulation in AD-like pathology rats. 相似文献