全文获取类型
| 收费全文 | 112121篇 |
| 免费 | 18414篇 |
| 国内免费 | 6808篇 |
专业分类
| 林业 | 7986篇 |
| 农学 | 5935篇 |
| 基础科学 | 6171篇 |
| 11888篇 | |
| 综合类 | 58098篇 |
| 农作物 | 8155篇 |
| 水产渔业 | 5666篇 |
| 畜牧兽医 | 19109篇 |
| 园艺 | 8914篇 |
| 植物保护 | 5421篇 |
出版年
| 2025年 | 191篇 |
| 2024年 | 2910篇 |
| 2023年 | 2979篇 |
| 2022年 | 5726篇 |
| 2021年 | 5364篇 |
| 2020年 | 5213篇 |
| 2019年 | 4981篇 |
| 2018年 | 3443篇 |
| 2017年 | 5698篇 |
| 2016年 | 3739篇 |
| 2015年 | 5685篇 |
| 2014年 | 6013篇 |
| 2013年 | 7264篇 |
| 2012年 | 9948篇 |
| 2011年 | 10240篇 |
| 2010年 | 9913篇 |
| 2009年 | 8787篇 |
| 2008年 | 8771篇 |
| 2007年 | 7754篇 |
| 2006年 | 6334篇 |
| 2005年 | 5022篇 |
| 2004年 | 3138篇 |
| 2003年 | 1866篇 |
| 2002年 | 1973篇 |
| 2001年 | 1772篇 |
| 2000年 | 1609篇 |
| 1999年 | 565篇 |
| 1998年 | 59篇 |
| 1997年 | 32篇 |
| 1996年 | 20篇 |
| 1995年 | 29篇 |
| 1994年 | 32篇 |
| 1993年 | 30篇 |
| 1992年 | 34篇 |
| 1991年 | 22篇 |
| 1990年 | 7篇 |
| 1989年 | 4篇 |
| 1988年 | 4篇 |
| 1987年 | 24篇 |
| 1986年 | 20篇 |
| 1981年 | 17篇 |
| 1980年 | 3篇 |
| 1976年 | 3篇 |
| 1966年 | 3篇 |
| 1965年 | 3篇 |
| 1964年 | 5篇 |
| 1962年 | 31篇 |
| 1957年 | 3篇 |
| 1956年 | 35篇 |
| 1955年 | 14篇 |
排序方式： 共有10000条查询结果，搜索用时 0 毫秒
61.
AIM To investigate the effect of forsythiaside A (FA) on immune function in rats with ulcerative colitis and its related mechanism. METHODS Healthy SD rats were randomly divided into 5 groups: control group (no treatment, normal feeding), model group (establishment of rat ulcerative colitis model), and low, medium and high doses of FA groups (treatment of the model rats with FA at 5 mg/kg, 20 mg/kg and 80 mg/kg, respectively). The malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in rat colon tissues were measured by colorimetry, and the serum levels of tumor necrosis factor-α (TNF-α), interleukin-2 (IL-2) and IL-4 were detected by ELISA. The spleen index and thymus index, the percentages of CD3+, CD4+ and CD8+ T-lymphocytes in peripheral blood mononuclear cells （PBMC）, the serum IgA and IgG levels, and the serum complement C3 and C4 levels were also determined. RESULTS The colon tissues of the rats in model group showed obvious inflammation and ulceration, indicating that the animal model was successfully established. Compared with model group, the colonic inflammation and ulceration were significantly attenuated in FA groups, among which the high dose had the best effect. Compared with control group, the spleen index and thymus index of the rars in model group were decreased (P <0.05), MDA content in colon tissues was increased (P <0.05), and SOD activity in colon tissues was decreased (P <0.05). The levels of CD3+, CD4+, CD8+ and CD4+/CD8+ T-lymphocytes in PBMC, and the serum levels of C3, C4 and IL-4 were decreased (P <0.05), while the serum levels of IgA, IgG, TNF-α, and IL-2 were increased in model group as compared with control group. Furthermore, the spleen index and thymus index of the rats in FA groups were increased (P <0.05), the MDA content in the colon tissues was decreased (P <0.05), and the SOD activity in the colon tissues was increased (P <0.05). The levels of CD3+, CD4+, CD8+ and CD4+/CD8+ T-lymphocytes in PBMC, and the serum levels of C3, C4 and IL-4 were increased (P <0.05), while serum IgA, IgG, TNF-α and IL-2 levels were decreased in FA groups as compared with model group (P <0.05). CONCLUSION Forsythiaside A effectively attenuates the colonic lesions in rats with ulcerative colitis, and its mechanism may be related to reinforcement of oxygen free radical scavenging power, alleviation of inflammatory response, and enhancement of immune function. 相似文献
62.
AIMTo investigate the role of soluble Klotho protein in THP-1-derived foam cell formation. METHODSTHP-1 monocytes were induced into macrophages by treatment with 160 nmol/L phorbol myristate acetate for 48 h, and then were divided into 6 groups: negative control group (THP-1-derived macrophages), positive control group [THP-1-derived foam cells induced by oxidized low-density lipoprotein (ox-LDL) for 48 h], and 25, 50, 100 and 200 μg/L soluble Klotho protein groups (THP-1-derived macrophages pretreated with soluble Klotho protein at the indicat?ed concentraions for 2 h and then induced by ox-LDL for 48 h). Lipid droplets in cytoplasm were observed by oil red O staining. The cholesterol outflow rate was detected by scintillation counting technique. The content of intracellular total cholesterol, free cholesterol and cholesterol ester was detected by enzyme fluorescence analysis. The expression of acyl-coenzyme A:cholesterol acyltransferase 1 （ACAT1） and ATP-binding cassette transport?er A1 (ABCA1) at mRNA and protein levels was determined by RT-qPCR and Western blot, respectively. RESULTSOil red O staining and lipid mass quantification showed that THP-1-derived foam cell formation was dose-dependently suppressed by soluble Klotho protein. The cholesterol efflux rate of THP-1-derived foam cells was increased by soluble Klotho protein in a dose-dependent manner (P <0.05). In addition, soluble Klotho protein decreased the expression of ACAT1 and increased the expression of ABCA1 in a dose-dependent manner (P <0.05). CONCLUSION The soluble Klotho protein inhibits THP-1-derived foam cell formation in a dose-dependent manner by down-regulating the expression of ACAT1 and up-regulating the expression of ABCA1. 相似文献
63.
AIM: To investigate the effect of Linc00152 on the viability, apoptosis and radiosensitivity of cervical cancer cells. METHODS: RT-qPCR was used to detect the expression levels of Linc00152 and microRNA-376c-3p(miR-376c-3p) in human cervical cancer HeLa cells and SiHa cells, and normal cervical Ect1/E6E7 cells. The cervical cancer HeLa cells with low Linc00152 expression or miR-376c-3p over-expression were established. MTT assay, flow cytometry, colony formation assay and Western blot were used to determine the cell viability, apoptosis, radiosensitivity and related protein expression. The dual-luciferase reporter assay was used to verify the regulatory relationship between Linc00152 and miR-376c-3p in the HeLa cells. RESULTS: Compared with the Ect1/E6E7 cells, Linc00152 was up-regulated in the HeLa cells and SiHa cells, and miR-376c-3p was down-regulated (P < 0.05). Low expression of Linc00152 or over-expression of miR-376c-3p inhibited the viability of HeLa cells, induced apoptosis, enhanced the radiosensitivity, inhibited the protein expression of cyclin D and Bcl-2, and promoted the protein expression of P21 and Bax (P < 0.05). Linc00152 negatively regulated miR-376c-3p expression in the HeLa cells, and inhibition of miR-376c-3p expression reversed the effect of low expression of Linc00152 on HeLa cell viability, apoptosis and radiosensitivity. CONCLUSION: Linc00152 is highly expressed in the cervical cancer cells. Linc00152 affects the viability, apoptosis and radiosensitivity of HeLa cells by targeting miR-376c-3p, which is a potential diagnosis and treatment target for cervical cancer. 相似文献
64.
65.
为优化培育高质量油菜毯状苗的方法,完善育苗体系,以甘蓝型双低油菜品种宁杂1838为材料,采用传统标准的水稻育秧盘进行油菜毯状苗育苗,设置了在试验基质中拌入不同量硫酸铵的处理,通过测定油菜苗在不同时期的农艺性状、器官干重,研究了硫酸铵在不同用量对油菜毯状苗的调控效应;结果显示,试验基质中硫酸铵最佳用量范围为每盘4.37~4.62 g,这一用量条件下可显著增加存苗数、出叶数、绿叶数和单株叶面积,且干物质积累最多,最有利于毯苗移栽后返青活棵。 相似文献
66.
为了解前作大豆对后茬油菜根肿病的影响,采用大田轮作试验和实时荧光定量PCR检测法,研究大豆、白菜、油菜分别作为前作,调查后茬油菜根肿病的发生和土壤中休眠孢子含量,比较分析了不同前作的根系分泌物对休眠孢子萌发的影响,结果表明前作大豆,后茬油菜根肿病的发病率和病情指数分别为34.00%和19.26、土壤休眠孢子含量为1.45×106个/克土壤,显著低于前作为油菜、白菜和撂荒对照的相应量。大豆、油菜和白菜根系分泌物均可刺激根肿菌休眠孢子萌发。与根肿菌休眠孢子共培6 d后,大豆根系分泌物培养的休眠孢子萌发率为29.82%,显著高于白菜（15.52%）、油菜根系分泌物（14.83%）和营养液（6.48%）培养下的萌发率。据此推测,前作种植大豆,后茬油菜根肿病发生和危害减轻,原因应与大豆根系分泌物刺激根肿菌休眠孢子萌发,产生的游动孢子因缺少寄主植物而死亡,导致诱发病害的初侵染源（土壤中休眠孢子含量）减少有关。 相似文献
67.
68.
对近五十年国内外加拿大披碱草的研究进展进行了综述,结果表明,加拿大披碱草高产、叶量大、优质、寿命长且抗性优良,是小麦族内很适于远缘杂交的种之一.目前国内外的研究中,利用抗性基因进行杂交育种是加拿大披碱草研究的热点.主要存在的问题有:缺乏有关加拿大披碱草的基础性研究;缺乏后续的持续性研究. 相似文献
69.
70.