全文获取类型
收费全文 | 35456篇 |
免费 | 2045篇 |
国内免费 | 3189篇 |
专业分类
林业 | 3000篇 |
农学 | 1949篇 |
基础科学 | 1674篇 |
3726篇 | |
综合类 | 16265篇 |
农作物 | 2396篇 |
水产渔业 | 1980篇 |
畜牧兽医 | 5447篇 |
园艺 | 2688篇 |
植物保护 | 1565篇 |
出版年
2024年 | 295篇 |
2023年 | 750篇 |
2022年 | 1706篇 |
2021年 | 1742篇 |
2020年 | 1659篇 |
2019年 | 1551篇 |
2018年 | 1147篇 |
2017年 | 1743篇 |
2016年 | 1144篇 |
2015年 | 1759篇 |
2014年 | 1792篇 |
2013年 | 2280篇 |
2012年 | 3121篇 |
2011年 | 3011篇 |
2010年 | 2796篇 |
2009年 | 2520篇 |
2008年 | 2392篇 |
2007年 | 2245篇 |
2006年 | 1834篇 |
2005年 | 1417篇 |
2004年 | 885篇 |
2003年 | 611篇 |
2002年 | 652篇 |
2001年 | 587篇 |
2000年 | 554篇 |
1999年 | 217篇 |
1998年 | 67篇 |
1997年 | 26篇 |
1996年 | 26篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 21篇 |
1992年 | 21篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1962年 | 8篇 |
1959年 | 1篇 |
1956年 | 16篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
21.
针对我国花椰菜产业不断发展壮大、种植面积不断扩大,尤其是松花菜的种植面积和市场占有率迅速增长的情况,从种植情况、种子研发企业和松花菜栽培情况3大部分展开,介绍了京津冀地区花椰菜产业的发展现状,列举了京津冀地区花椰菜品种品质、育种技术及商品物流方面存在的问题,并提出了发展趋势及应对策略,如加强优质、多抗、适应性强的花椰菜新品种选育,重视花椰菜现代育种技术的创新,加强育种技术的交流与合作,培育龙头企业,加大品牌宣传力度,推进京津冀花椰菜产业发展进程。 相似文献
22.
23.
24.
以聚L-乳酸(PLLA)和麦草(WS)为原料,以N-甲基吗啉-N-氧化物(NMMO)为溶剂,采用溶液共混法制备了PLLA/WS共混物。首先将麦草溶解在NMMO后,再添加聚L-乳酸并溶解,制备聚L-乳酸与麦草的共混溶液。共混溶液采用浇膜法制备PLLA/WS共混物,采用差示扫描量热法、X射线衍射法、傅里叶变换红外光谱、热重分析和扫描电镜等方法对所得的共混物进行表征。结果表明,聚L-乳酸与麦草可以形成均匀的共混溶液。共混物中PLLA与麦草组分之间具有较强的相互作用,相容性较好。当共混物中PLLA的质量分数为50%时,共混物可以形成结晶结构,且随着PLLA含量的增加,其结晶更加完美,熔点与热稳定性提高。共混物薄膜断面结构较为致密,这说明PLLA与麦草相容性较好,混合均匀。通过调节聚L-乳酸和麦草的配比,可以制备不同性能的生物高分子材料。 相似文献
25.
普陀水仙花大球栽培技术试验初报 总被引:4,自引:0,他引:4
对普陀水仙花采用优质种球繁育技术、湿生栽培技术、种球阉割技术、病害综合防治技术和氮、磷、钾合理配方施肥技术5项技术措施后,其病害减轻,分生球减少,主球的大球率从原来的30%以下提高到60%以上. 相似文献
26.
原料表面碱液处理对稻草碎料板力学性能的影响 总被引:1,自引:0,他引:1
在实验室条件下探索了稻草原料表面碱液处理对稻草碎料板力学性能的影响.试验表明,处理后的稻草碎料板的内结合强度比处理前有大幅度提高,弯曲弹性模量和静曲强度比处理前则有所下降,但都达到了相关的国家标准;2h吸水厚度膨胀率升高,超过国家标准.因此稻草表面碱液处理提高了稻草原料表面润湿性和胶合强度,但对稻草碎料板的力学性能有影响. 相似文献
27.
AIM: To investigate the changes of peroxisome proliferator-activated receptors (PPAR)α/peroxisome proliferator activated receptor coactivator 1 alpha (PGC-1α) in doxorubicin (DOX) induced dilated cardiomyopathy (DCM) and its effect on the energy metabolism and myocardial function in mice. METHODS: Forty mice were randomly divided into 4 groups: control group, DOX group, PPARα inhibitor group and PPARα agonist group. The DCM model was established by injection of DOX. The protein levels of PPARα/PGC-1α were detected. The PPARα inhibitor and PPARα agonist were used 2 weeks beforeinjection of DOX. The contents of adenine acid and phosphocreatine (Pcr) in the mitochondria were measured by high-performance liquid chromatography (HPLC). The ANT activity was analyzed by the atractyloside-inhibitor stop technique. The changes of the echocardiography and hemodynamics were also observed. RESULTS: DOX induced DCM model was successfully established. The protein levels of PPARα and PGC-1α in control group were significantly higher than those in DOX group (P<0.05). Both of the high-energy phosphate contents and the transport activity of ANT were decreased in DOX group (P<0.05), and the hemodynamic parameters were disordered (P<0.01). Compared with DOX group, PPARα inhibitor pre-treatment significantly reduced the PPARα/PGC-1α expression. Meanwhile, high-energy phosphate contents in the mitochondria and the ANT transport activity of the mitochondria decreased, as well as the left ventricular function (P<0.05). On the other hand, PPARα agonist significantly increased the expression of PPARα and PGC-1α, and improved the transport activity of ANT. In addition, the hemodynamic parameters were ameliorated, but the high-energy phosphate contents of the mitochondria did not significantly change. CONCLUSION: PPARα/PGC-1α plays an important role in the regulation of ANT transport activity in dilated cardiomyopathy induced by DOX, and the activation of PPARα/PGC-1α has protective effects on the DCM induced by DOX. 相似文献
28.
LI Feng YAO Li ZHANG Xi-hong XIA Yu-hong CHENG Jie LOU Xue-ling JIANG Qiu-hui 《园艺学报》2016,32(12):2251-2255
AIM: To examine the expression of miRNA-22 in the ovarian tissues and the effect of miRNA-22 over-expression on the proliferation, migration and invasion in SKOV-3 cells. METHODS: The expression levels of miRNA-22 in different ovarian tissues and SKOV-3 cells were determined by qPCR. miRNA-22 was over-expressed by transfection of miRNA-22 mimic. The cell viability was examined by CCK-8 assay. The cell migration was measured by wound healing test. The cell invasion was analyzed by Transwell assay. The protein expression levels of VEGF and P53 were determined by Western blot. RESULTS: Compared with the normal ovarian tissue, the expression level of miRNA-22 was remarkably decreased in the ovarian tumor tissues. After transfection with miRNA-22 mimic, the expression level of miRNA-22 in the SKOV-3 cells was significantly increased, while the cell viability, migration and invasion were obviously decreased. Moreover, the protein expression of VEGF and P53 was dramatically inhibited after over-expression of miRNA-22. CONCLUSION: The decreased miRNA-22 expression may be correlated with the development of ovarian can-cer. Over-expression of miRNA-22 decreases the cell viability, migration and invasion by reducing the protein expression of VEGF and P53. 相似文献
29.
大豆抗旱的生理生态基础 总被引:13,自引:0,他引:13
大豆抗旱的生理基础和生态基础 ,前人已做过研究。综述前人在大豆抗旱的形态特征、解剖组织特点及影响抗旱的各生态因子方面的研究成果 ,为大豆的高产优质低耗栽培提供理论依据 相似文献
30.