全文获取类型
收费全文 | 17550篇 |
免费 | 1138篇 |
国内免费 | 3122篇 |
专业分类
林业 | 814篇 |
农学 | 2598篇 |
基础科学 | 419篇 |
2183篇 | |
综合类 | 6876篇 |
农作物 | 4432篇 |
水产渔业 | 355篇 |
畜牧兽医 | 2425篇 |
园艺 | 1225篇 |
植物保护 | 483篇 |
出版年
2024年 | 129篇 |
2023年 | 353篇 |
2022年 | 530篇 |
2021年 | 647篇 |
2020年 | 607篇 |
2019年 | 726篇 |
2018年 | 657篇 |
2017年 | 647篇 |
2016年 | 1012篇 |
2015年 | 1245篇 |
2014年 | 1333篇 |
2013年 | 1343篇 |
2012年 | 1377篇 |
2011年 | 1169篇 |
2010年 | 1071篇 |
2009年 | 1051篇 |
2008年 | 961篇 |
2007年 | 1126篇 |
2006年 | 1043篇 |
2005年 | 889篇 |
2004年 | 505篇 |
2003年 | 386篇 |
2002年 | 343篇 |
2001年 | 347篇 |
2000年 | 343篇 |
1999年 | 245篇 |
1998年 | 242篇 |
1997年 | 198篇 |
1996年 | 188篇 |
1995年 | 184篇 |
1994年 | 164篇 |
1993年 | 137篇 |
1992年 | 105篇 |
1991年 | 100篇 |
1990年 | 100篇 |
1989年 | 73篇 |
1988年 | 51篇 |
1987年 | 33篇 |
1986年 | 26篇 |
1985年 | 31篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1963年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
介绍了山地橄榄2种病害:叶斑病、炭疽病;5种虫害:橄榄星室木虱、黑刺粉虱、恶性叶甲、橄榄枯叶蛾、橄榄野螟的主要特征和危害症状,并提出了防治措施。 相似文献
42.
Storage proteins and glutathione in wheat play an important role in gluten network formation and can be modified by supplementation of nitrogen (N) and sulphur (S) in wheat plants. The glutathione thiol-disulfide status and its relationship to the molecular weight distribution wheat polymeric protein and dough rheological properties have been examined after different foliar S fertilizations (S derived from micronized elemental S and NS, a mixture of N urea and elemental S) applied at the post-anthesis stage. Changes in levels of reduced glutathione (GSH), glutathione disulfide (GSSG), polymeric protein-glutathione mixed disulfide (PPSSG) were analysed by reversed phase high performance liquid chromatography, during grain development using the wheat cultivars, Soissons and Trémie. During the grain desiccation phase, S supplementation (i) increased the GSSG/GSH ratio by 23–25% (ii) induced PPSSG accumulation, and (iii) decreased the formation of SDS-unextractable polymeric protein (UPP) and its molecular mass distribution. However, simultaneous N and S supplementation results in: (i) a decrease in PPSSG formation by 20–30% and (ii) an increase of UPP by 7–18% by enhancing both the branching of the aggregated proteins and their molecular weight. The mixograph parameters show that all forms of endogenous glutathione are linked to dough weakening and are negatively correlated with dough mixing tolerance, dough strength and consistency, while UPP is positively correlated with dough strength and consistency. These findings indicate that S nutrition influences dynamics of the glutathione forms in the grain and results in modification the degree of polymerization of storage protein. Thus both the changes in the form of glutathione and protein polymerization influence the rheological properties of dough. 相似文献
43.
Late blight, caused by Phytophthora infestans , is an ongoing threat to potato and tomato crop production worldwide and considerable fundamental and applied research is conducted with the long-term aim of improved disease control. Understanding the mechanisms, processes and rates of P. infestans evolution is an important factor in predicting the effectiveness and durability of new management practices. A range of phenotypic and genotypic tests has been applied to achieve this goal, but each has limitations and new methods are sought. Recent progress in P. infestans genomics is providing the raw data for such methods and new high-throughput codominant biomolecular markers are currently being developed that have tremendous potential in the study of P. infestans population biology, epidemiology, ecology, genetics and evolution. This paper reviews some key applications, recommends some changes in approach and reports on the status and potential of new and existing methods for probing P. infestans genetic diversity. 相似文献
44.
中国梅的变异与分布研究 总被引:8,自引:0,他引:8
通过文献阅读、标本查阅及实地考察,发现了梅的一些变异类型。提出了梅的地理分布格局,对梅分布的历史迁作的探讨。种、滇、藏交界的横断山区是梅的自然分布中心,另外还有一些亚中心;在对种群数量和变异类型研究的基础上,确认梅的自然分布中心即梅的变异中心。 相似文献
45.
徐海祥 《湖南农业大学学报(自然科学版)》1989,16(1)
本文对于二阶椭圆型Euler方程组 -∑D_αF_(q_α~i)(x,u,Du)+F_(ui)(x,u,Du)=0得到了一些积分恒等式,利用这些恒等式证明了某些方程组非平凡解的不存在性。 相似文献
46.
47.
CTGF, a member of the CCN family of immediate early genes, is a recently discovered profibrotic growth factor, which is involved in many pathophysiologic procedures. CTGF acts as a downstream effector of TGF-β acting on interstitial cells to enhance the progression of fibrotic renal diseases. It has been shown that CTGF gene expression can be induced or blocked by some kinds of cytokine and drugs. It is an interesting candidate target for future intervention strategies of renal interstitial fibrosis. 相似文献
49.
50.
小麦矮秆育种中性状间关系的多元分析 总被引:12,自引:0,他引:12
以7个株高梯度系列的35个系统及5个亲本品种为材料,采用典范分析和逐步回归分析研究了株高及其构成因子与产量因子、产量生理性状间的关系。结果表明:①株高因子通过产量生理性状影响产量因子,一定的生物学产量是获得高产的基础。②矮秆品种的高化对提高产量、千粒重和收获指数有利,对蛋白质含量的影响不明显;高秆品种矮化能显著提高收获指数,对籽粒的蛋白质含量影响不大。③在主要性状符合育种目标的前提下,选择倒二节间较长、第一和第二叶间距略长、穗颈和穗部较长的类型可能对提高产量有利。 相似文献