全文获取类型
收费全文 | 709篇 |
免费 | 36篇 |
国内免费 | 47篇 |
专业分类
林业 | 121篇 |
农学 | 102篇 |
基础科学 | 34篇 |
49篇 | |
综合类 | 320篇 |
农作物 | 32篇 |
水产渔业 | 19篇 |
畜牧兽医 | 75篇 |
园艺 | 7篇 |
植物保护 | 33篇 |
出版年
2023年 | 9篇 |
2022年 | 9篇 |
2021年 | 19篇 |
2020年 | 20篇 |
2019年 | 22篇 |
2018年 | 13篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 30篇 |
2013年 | 43篇 |
2012年 | 56篇 |
2011年 | 49篇 |
2010年 | 48篇 |
2009年 | 39篇 |
2008年 | 37篇 |
2007年 | 37篇 |
2006年 | 37篇 |
2005年 | 39篇 |
2004年 | 20篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 1篇 |
排序方式: 共有792条查询结果,搜索用时 15 毫秒
111.
做好高校办公室督查督办工作的理论思考 总被引:1,自引:0,他引:1
督查督办是高校办公室基本的、重要的职能之一。笔者通过对工作实践的理论思考,从找准基点、把握基调、深入基层、总结基本规律等四个方面,对做好高校办公室督查督办工作的前提、本质要求、基本方法和长效机制作了具体阐述。这对高校办公室发挥好督查督办职能,推动学校工作落实具有一定的借鉴意义。 相似文献
112.
113.
114.
115.
Suberoylanilide hydroxamic acid,a novel histone deacetylase inhibitor,improves the development and acetylation level of miniature porcine handmade cloning embryos
下载免费PDF全文
![点击此处可从《Reproduction in domestic animals》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Histone deacetylase inhibitors (HDACis) can change the histone acetylation and significantly enhance the developmental competence of the pre‐implantation SCNT embryo. To select a proper histone deacetylase inhibitor to improve the success rate and potentially developmental ability of handmade cloning (HMC) embryos of miniature porcine, we compared the effect of two histone deacetylase inhibitors (SAHA vs. VPA) on HMC embryo development, their histone acetylation level and the expression level of relevant genes. The blastocyst rate and number of blastocyst cells of HMC embryos treated with SAHA (SAHA‐HMC) or VPA (VPA‐HMC) were significantly higher than those of control (Control‐HMC), respectively, but there were no significant difference between SAHA‐HMC and VPA‐HMC groups. In addition, the acetylation level (AcH4K8) of Control‐HMC and VPA‐HMC embryos at the blastocyst stage, respectively, was significantly lower than that of in vitro fertilized (IVF) and SAHA‐HMC embryos. However, the acetylation H4K8 of the blastocysts had no significant difference between SAHA‐HMC and the IVF groups. The SAHA‐HMC blastocysts indicated comparative expression levels of Oct4 and HDAC1 (histone deacetyltransferase gene) with those of IVF blastocysts. In contrast, the expression levels of Oct4 were lower and those of HDAC1 were higher in the VPA‐HMC and Control‐HMC blastocysts, respectively, compared to those of the IVF blastocysts. Our results demonstrated that the HMC embryos treated by SAHA could promote the pre‐implantation development and increase the levels of histone H4K8 acetylation and the expression of the OCT4 gene, yet decrease the expression of the HDAC1 gene to the comparable level of the IVF embryos. Our results proved that SAHA may be a better histone deacetylase inhibitor for porcine HMC compared to VPA, and furthermore, it may indicate that SAHA can effectively correct the abnormal histone acetylation during the HMC embryo development and subsequently improve the full‐term developmental potential of the HMC embryos after embryo transplantation. 相似文献
116.
117.
[目的]改革开放以来,随着经济社会的发展,城镇化的加速,越来越多的城乡土地问题也应运而生,为实现城镇化发展与土地可持续利用的良性循环,这些问题都亟待解决.研究城镇化进程引发的城乡土地问题的解决方法.[方法]运用持续发展的理论思想,采用理论探索与实证研究相结合的方法对城镇化建设产生的一系列土地问题进行了研究.[结果]经过分析后,得到解决这些土地问题的合适方案,将涉及面展开映射到全国,最终问题的解决方案亦可应用到全国合适的区域.[结论]阐述了伴随着城镇化而来的一些土地资源方面比较大众化的问题,并提供一些解决方案以供参考,具有一定的应用价值. 相似文献
118.
根据保护区的概况和保护类型,论述了保护区的保护价值、保护区的自然生态特征,并对保护区进行了综合评价。 相似文献
119.
120.
Staffieri F De Monte V De Marzo C Grasso S Crovace A 《Veterinary anaesthesia and analgesia》2010,37(6):483-490
ObjectiveTo compare the effects of two fractions of inspired oxygen (FiO2) (0.4 and 1) on lung aeration and gas exchange during general anaesthesia in cats.Study designRandomized, blinded, controlled study.AnimalsThirty healthy, mixed breed, client owned female cats.Materials and methodsCats were premedicated intramuscularly with acepromazine (0.03 mg kg?1) and medetomidine (0.015 mg kg?1). Anaesthesia was induced with propofol (5 mg kg?1) and, after orotracheal intubation, maintained with isoflurane carried by either 100% oxygen (G100, n = 15) or an oxygen-air mixture with 40% oxygen (G40, n = 15). All cats were placed in dorsal recumbency and breathed spontaneously throughout the entire procedure. Following surgery (ovariectomy), a spiral computed tomography (CT) of the thorax was performed, arterial oxygen (PaO2) and carbon dioxide (PaCO2) tensions were measured and alveolar-arterial gradient of oxygen [P(A-a)O2] calculated. The CT images were analysed for lung aeration by the analysis of radiograph attenuations (Hounsfield units, HU), according to the following classification: hyperinflated area (-1000 to -900 HU), normally aerated area (-900 to -500 HU), poorly aerated area (-500 to -100 HU) and non-aerated area (-100 to +100 HU). The groups were compared using one-way anova.ResultsCompared to G100, the normally-aerated lung area was significantly greater and the poorly-aerated and non-aerated areas were significantly smaller in G40. PaCO2 was similar in both groups. PaO2 and P(A-a)O2 were significantly higher in G100. In both groups, pulmonary atelectasis developed preferentially in the caudal lung fields.ConclusionIn cats anaesthetised with isoflurane, the administration of an FiO2 of >0.9 significantly impaired lung aeration and gas exchange as compared to an FiO2 of 0.4.Clinical relevanceAn FiO2 of 0.4 may better preserve lung aeration and gas exchange in anaesthetised spontaneously breathing cats but monitoring is essential to ensure oxygenation is adequate. 相似文献