全文获取类型
| 收费全文 | 4185篇 |
| 免费 | 182篇 |
| 国内免费 | 207篇 |
专业分类
| 林业 | 219篇 |
| 农学 | 108篇 |
| 基础科学 | 243篇 |
| 343篇 | |
| 综合类 | 1713篇 |
| 农作物 | 236篇 |
| 水产渔业 | 185篇 |
| 畜牧兽医 | 816篇 |
| 园艺 | 453篇 |
| 植物保护 | 258篇 |
出版年
| 2024年 | 26篇 |
| 2023年 | 50篇 |
| 2022年 | 124篇 |
| 2021年 | 105篇 |
| 2020年 | 89篇 |
| 2019年 | 122篇 |
| 2018年 | 82篇 |
| 2017年 | 196篇 |
| 2016年 | 121篇 |
| 2015年 | 201篇 |
| 2014年 | 247篇 |
| 2013年 | 360篇 |
| 2012年 | 489篇 |
| 2011年 | 494篇 |
| 2010年 | 441篇 |
| 2009年 | 365篇 |
| 2008年 | 361篇 |
| 2007年 | 285篇 |
| 2006年 | 191篇 |
| 2005年 | 125篇 |
| 2004年 | 60篇 |
| 2003年 | 17篇 |
| 2002年 | 11篇 |
| 2001年 | 7篇 |
| 2000年 | 3篇 |
| 1999年 | 1篇 |
| 1998年 | 1篇 |
排序方式： 共有4574条查询结果，搜索用时 437 毫秒
81.
大青叶樱桃根际微生物种群结构及其变化动态 总被引：3，自引：0，他引：3
利用选择性培养基,对2年生大青叶樱桃(Cerasus pseudocerasus)根际微生物进行了分离、鉴定和分类,分析了不同物候期根际微生物种群结构的变化。结果表明,从大青叶樱桃根际分离纯化获得的细菌分别属于15个属,以芽孢杆菌属(Bacillus)、假单胞菌属(Pseudomonas)为主;放线菌属于链霉菌属的6个类群,以白色类群(Albosporus)、黄色类群(Flavus)为主;真菌以镰刀菌(Fusarium)和木霉属(Trichoderma)为主。不同生育期根际微生物种群结构不同,落叶期根际细菌种群结构最丰富,萌芽期最少。 相似文献
82.
利用阿魏菇（Pleurotus ferulae Lanzi）A0501菌株进行工厂化袋栽生产工艺试验。主要介绍了阿魏菇的生产工艺流程：母种的制备、原种的制备、茵袋的制备、接种发茵、后熟管理、搔茵与催蕾、修菇及育菇和出菇期管理，以及生产过程中出现茵袋污染和出菇期间发生病虫害的问题和解决办法。在控制污染的过程中，采用高压蒸汽灭菌，无菌过滤单元接种，对发茵棚进行严格的科学管理方法。针对病虫害的防治，采用不同的方法防治不同的病虫害，从而提高阿魏菇生产的经济效益。 相似文献
83.
以黄瓜(Cucumis sativus L.)幼苗为试材,研究了不同浓度极多产溶液(壳聚糖的酸性溶液)的处理对其低温胁迫后的生长势和生理生化特性变化的影响.结果表明:在低温胁迫后恢复生长过程中,极多产处理浓度为100mg/L和200mg/L的黄瓜幼苗恢复生长较快,常温下恢复生长15d幼苗的光曲线净光合速率及活性氧清除酶SOD、APX和POD也明显高于对照,同时植株的株高、最大叶面积、鲜重和干重也都显著高于对照.说明适宜浓度的极多产处理能有效地促进冷胁迫后黄瓜幼苗的生长,对低温胁迫有一定的缓解效应. 相似文献
84.
中药复方多糖及其均一组分对雏鸡免疫功能的影响 总被引：1，自引：0，他引：1
目的:观察从自拟中药复方免疫增强剂中提取的复方多糖及其均一组分对雏鸡免疫功能的影响。方法:将14日龄健康雏鸡660只随机分为12组,每组55只。分别于15、16、17日龄口服黄芪多糖 环磷酰胺、复方多糖 环磷酰胺、GCPS-1-A-Ⅰ(多糖均一组分Ⅰ) 环磷酰胺、GCPS-2-A-Ⅱ(多糖均一组分Ⅱ) 环磷酰胺、GCPS-3-A-Ⅲ(多糖均一组分Ⅲ) 环磷酰胺、黄芪多糖、复方多糖、GCPS-1-A-Ⅰ、GCPS-2-A-Ⅱ、GCPS-3-A-Ⅲ、生理盐水、肌注环磷酰胺。分别在用药前、用药后7 d、14 d、21 d、28 d、35 d、42 d采血,测定红细胞数量;分别在NDⅣ系疫苗首免后7、14、21 d,二免后7、14、21 d采血、分离血清,测定ND-H I抗体效价。结果:中药复方多糖及其均一组分可使雏鸡红细胞数量、首免和二免后ND-H I抗体效价明显升高,其中以GCPS-2-A-Ⅱ组效果最佳;环磷酰胺可使上述指标明显下降,中药多糖能使环磷酰胺所致免疫抑制逆转至正常水平,复方多糖 环磷酰胺组、GCPS-2-A-Ⅱ 环磷酰胺组、GCPS-1-A-Ⅰ组、GCPS-3-A-Ⅲ组与生理盐水对照组相比差异不显著,复方多糖组、GCPS-2-A-Ⅱ组与黄芪多糖组相比差异显著。结论:中药复方多糖均一组分具有很好的免疫增强作用,但是其纯度与免疫增强效果不成正比。 相似文献
85.
AIM: To investigate the possible effect of hyperlipidemia on golmerular podocytes,the nitric oxide synthase (NOS) availability and the synthesis of NOS in podocyte damage by hyperlipidemia,further to study the protective effect of simvastatin on podocytes.METHODS: 4 groups of Wistar rats were fed high fat diet for 18 weeks.Serum lipid,urinary protein excretion and renal pathological changes were detected.Immunohistochemistry was used to determine the expression of desmin.The expression of nNOS was detected by Western blotting.RESULTS: The level of serum lipid was increased significantly in hyperlipidemic group and treated group after 4 weeks (P<0.01) and was decreased significantly in simvastatin treated group compared with hyperlipidemic group (P<0.01).Podocyte injury was detected under electronic microscopy in hyperlipidemic group after 4 weeks,and the injury became more serious during the lasting time.The expression of desmin was increased in hyperlipidemic group after 4 weeks,and the level was significantly decreased in treated groups (P<0.01).The urinary protein excretion was increased significantly after 6 weeks (P<0.01),and the level was significantly lower in treated groups (P<0.01).The expression of nNOS was significantly decreased in hyperlipidemic and treated groups (P<0.01),and the level significantly decreased in simvastatin group (P<0.01).CONCLUSION: Hyperlipidemia induces podocyte injury.The injury seems to be associated with NO deficiency and decreased renal NOS activity.The injury can be relieved by simvastatin. 相似文献
86.
87.
JUAN M. MARTI LV Cert SAO MVM MRCVS SIMON C. ROE BVSc MS PhD Diplomate ACVS 《Veterinary surgery : VS》1998,27(5):423-428
Objective —To compare the insertional characteristics of external fixator pins with hollow ground (HG), modified HG, and trocar (T) points.
Study Design —An acute, in vitro biomechanical evaluation.
Sample Population—Thirteen radii from canine cadavers.
Methods —A total of 16 T-tipped and 16 HG-tipped pins were inserted into 8 canine radii. Ten pins of each modification of the HG tip (length of the cutting edge reduced by 0.127 mm and 0.254 mm, respectively) were inserted into another five radii. All pins were inserted with low-speed power drilling and 80 N drilling load. Differences between peak tip temperature, drilling energy, and pullout force were determined for each pin type at both diaphyseal and metaphyseal locations.
Results —HG-tipped pins showed a 40% lower tip temperature in diaphyseal bone, a 25% reduction in drilling energy in diaphyseal bone, and a reduction of pullout force in both diaphyseal (65%) and metaphyseal (50%) bone compared with T-tipped pins. HG 0.254-mm pins generated higher tip temperatures and had greater pullout than HG pins in diaphyseal bone.
Conclusions —The HG tip was a more efficient design; however, the reduction in pullout force suggests that, because a better hole was drilled, radial preload is reduced. Reduction of the cutting edge by 0.254 mm increased the pullout force but also increased the temperatures.
Clinical Relevance —Thermal and microstructural damage are reduced by the HG tip, but pin-bone interface stability is also compromised. The use of a tip with 0.254 mm reduction in the cutting edge may optimize the biological and mechanical factors at the pin-bone interface. 相似文献
Study Design —An acute, in vitro biomechanical evaluation.
Sample Population—Thirteen radii from canine cadavers.
Methods —A total of 16 T-tipped and 16 HG-tipped pins were inserted into 8 canine radii. Ten pins of each modification of the HG tip (length of the cutting edge reduced by 0.127 mm and 0.254 mm, respectively) were inserted into another five radii. All pins were inserted with low-speed power drilling and 80 N drilling load. Differences between peak tip temperature, drilling energy, and pullout force were determined for each pin type at both diaphyseal and metaphyseal locations.
Results —HG-tipped pins showed a 40% lower tip temperature in diaphyseal bone, a 25% reduction in drilling energy in diaphyseal bone, and a reduction of pullout force in both diaphyseal (65%) and metaphyseal (50%) bone compared with T-tipped pins. HG 0.254-mm pins generated higher tip temperatures and had greater pullout than HG pins in diaphyseal bone.
Conclusions —The HG tip was a more efficient design; however, the reduction in pullout force suggests that, because a better hole was drilled, radial preload is reduced. Reduction of the cutting edge by 0.254 mm increased the pullout force but also increased the temperatures.
Clinical Relevance —Thermal and microstructural damage are reduced by the HG tip, but pin-bone interface stability is also compromised. The use of a tip with 0.254 mm reduction in the cutting edge may optimize the biological and mechanical factors at the pin-bone interface. 相似文献
88.
文章针对如何致力于提高高中物理教学质量这一问题进行研究探讨,并制定改善这一问题的相关措施,从而来对物理教育这一事业做出贡献,希望它能够有更好的发展. 相似文献
89.
90.
湛江市甘蔗良种场引进甘蔗新品种，优选出优良株系，暂命名为湛引8号。2006年以来在湛江通过试种，证明该品种具有高产、稳产、早熟、高糖等特点，适合湛江蔗区种植。本文主要介绍该品种在当地的种植表现及配套栽培技术。 相似文献