全文获取类型
收费全文 | 26691篇 |
免费 | 1758篇 |
国内免费 | 2743篇 |
专业分类
林业 | 2390篇 |
农学 | 2350篇 |
基础科学 | 1690篇 |
3183篇 | |
综合类 | 11405篇 |
农作物 | 1948篇 |
水产渔业 | 1410篇 |
畜牧兽医 | 3908篇 |
园艺 | 1631篇 |
植物保护 | 1277篇 |
出版年
2024年 | 106篇 |
2023年 | 447篇 |
2022年 | 1003篇 |
2021年 | 1097篇 |
2020年 | 1025篇 |
2019年 | 987篇 |
2018年 | 712篇 |
2017年 | 1227篇 |
2016年 | 950篇 |
2015年 | 1374篇 |
2014年 | 1380篇 |
2013年 | 1658篇 |
2012年 | 2215篇 |
2011年 | 2293篇 |
2010年 | 2100篇 |
2009年 | 1902篇 |
2008年 | 1880篇 |
2007年 | 1791篇 |
2006年 | 1489篇 |
2005年 | 1160篇 |
2004年 | 775篇 |
2003年 | 595篇 |
2002年 | 704篇 |
2001年 | 642篇 |
2000年 | 531篇 |
1999年 | 276篇 |
1998年 | 161篇 |
1997年 | 138篇 |
1996年 | 77篇 |
1995年 | 95篇 |
1994年 | 101篇 |
1993年 | 66篇 |
1992年 | 55篇 |
1991年 | 55篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 15篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1962年 | 5篇 |
1956年 | 4篇 |
1955年 | 4篇 |
1932年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
81.
Powdery Mildew of Prairie Gentian: Characteristics,Molecular Phylogeny and Pathogenicity 总被引:3,自引:0,他引:3
OKAMOTO Jun LIMKAISANG Saranya NOJIMA Hidenobu TAKAMATSU Susumu 《Journal of General Plant Pathology》2002,68(3):200-207
In March 1999, we found prairie gentian (Eustoma grandiflorum) infected with powdery mildew in a greenhouse in Oita Prefecture, Japan. Morphological observation revealed that the causal
fungus belongs to the mitosporic genus Oidium subgenus Pseudoidium [teleomorph: Erysiphe sensu Braun and Takamatsu (2000)]. Precise taxonomic position of the fungus, however, is uncertain due to lack of the perfect stage.
We determined the nucleotide sequence of the rDNA ITS region of the fungus. Comparison of the sequence with those obtained
from DNA databases of this fungal group revealed that the sequence is identical to those of powdery mildews from garden four-o'clock
(Mirabilis jalapa) and broad bean (Vicia faba). Inoculation of an isolate from garden four-o'clock caused mildew on prairie gentian and broad bean, suggesting that the
prairie gentian mildew originates from garden four-o'clock or broad bean. Molecular phylogenetic analysis indicated a close
relationship of this fungus to Erysiphe baeumleri on Vicia spp. and E. trifolii on Trifolium pratense. From these results, we propose that prairie gentian mildew diverged from a Fabaceae-parasitic ancestor.
Received 14 March 2002/ Accepted in revised form 28 May 2002 相似文献
82.
区域旅游资源开发定位研究——以内蒙古赤峰市为例 总被引:7,自引:1,他引:7
区域旅游资源开发是发展区域旅游的基础 ,开发的定位研究有助于为一地旅游业的发展指明方向。本文从区域角度和空间经济一体化思想出发 ,以赤峰市为例 ,通过对旅游资源的定量与定性研究 ,得到旅游资源的综合评价图式 ,结合区际分析归纳出赤峰市旅游资源开发利用的方向和层次。从而为区域旅游开发的定位研究进行了一般理论的探讨及例证分析 相似文献
83.
84.
85.
86.
87.
AIM:To investigate the effect of metallothionein(MT) on proliferation of rat vascular smooth muscle cells (VSMCs) stimulated by homocysteine and its mechanism. METHODS:VSMCs proliferation was measured by [3-H]-TdR incorporation, mitogen-activated protein kinase(MAPK)activity were determined by immunoprecipitation method, the intracellular contents of MT and malondialdehyde (MDA)were assayed by -hemoglobin saturation method and TBA reaction, respectively, and lactate dehydrogenase (LDH) leakage was measured by NADH oxidation. RESULTS:Hcy(10-6-10-4 mmol/L) stimulated [3-H]-TdR incorporation by the VSMCs in a concentration-dependent manner. Compared with control, [3-H]-TdR incorporation in VSMCs treated with 0.1 mmol/L Hcy was increased by 4.2 fold (P<0.01). Meanwhile, Hcy enhanced MAPK activity, MDA formation and LDH release (P<0.01)in a concentration-dependent manner. Treatment of VSMCs with MT alone did not change above parameters, compared with control. However, MT (10-6-10-4 mol/L)attenuated significantly Hcy-stimulated proliferation of VSMCs (P<0.01)in a concentration-dependent manner. And MT inhibited obviously Hcy-induced activation of MAPK activity, MDA formation and LDH release. Preincubation of VSMCs with 0.5 mmol/L ZnCl2 for 6 h induced an increase cellular MT content by 5.7-fold (P<0.01). The MT-overexpressed VSMCs resisted Hcy-stimulating action on MAPK activity, MDA formation and LDH leakage (P<0.01). CONCLUSION:These results show that MT has an inhibitory effect on Hcy-induced VSMCs proliferation, and that MT could inhibit Hcy-stimulated MAPK activity and lipid peroxidation. 相似文献
88.
AIM:To study the effect of environment of liver regeneration on the proliferation of rat fetal hepatocytes after intrasplenical transplantation. METHODS:Fetal hepatocytes isolated from 3-week SD rat fetuses bred were transplanted into the spleens of liver regeneration model rats with 70% partial hepatectomy. The cell cycle of the hepatocytes in the remnants liver was analyzed by flow cytometer and the density dimensions of the donor fetal hepatocytes in spleen were measured by image analysis system 7 and 30 days post-transplantation, respectively. RESULTS:Compared with the control group, the proportions of S and G2 /M cells in the remnants liver were obviously decreased (P<0.05), but the density dimensions of the donor fetal hepatocytes in spleen increased significantly (P<0.05) in rats with hepatectomy 7 days post-transplantation. CONCLUSION:The environment of liver regeneration is propitious to the proliferation of fetal hepatocytes after transplantation into spleen. 相似文献
89.
LIN Jun SUN Jie ZHOU Yan HUANG Xing XIONG Ping WANG Ya-ping DENG Chang-sheng 《园艺学报》2002,18(9):1112-114
AIM: To probe into the genetic susceptibility of HLA-DRB1 alleles to esophageal neoplasm in Hubei Han Chinese. METHODS: HLA-DRB1 gene polymorphism in 42 patients with esophageal neoplasm and 136 normal control subjects was studied by PCR and sequence. RESULTS: Allele frequency of HLA-DRB1 *0901 allele was significantly higher in esophageal cancer patients than those in normal controls(0.2500 vs 0.1397, P =0.028; the odds ratiO2.053; etiologic fraction 0.1282).There were no association between the rested HLA-DRB1 alleles with patients. CONCLUSION: Individuals carrying HLA-DRB1 *0901 may be susceptible to esophagealo carcinoma, its nucleotide sepuence approachs to the corresponded allele sequence(exoN2)published in GenBank. 相似文献
90.