全文获取类型
收费全文 | 6076篇 |
免费 | 288篇 |
国内免费 | 624篇 |
专业分类
林业 | 630篇 |
农学 | 828篇 |
基础科学 | 502篇 |
981篇 | |
综合类 | 1873篇 |
农作物 | 315篇 |
水产渔业 | 258篇 |
畜牧兽医 | 1007篇 |
园艺 | 194篇 |
植物保护 | 400篇 |
出版年
2024年 | 27篇 |
2023年 | 82篇 |
2022年 | 200篇 |
2021年 | 272篇 |
2020年 | 206篇 |
2019年 | 255篇 |
2018年 | 175篇 |
2017年 | 206篇 |
2016年 | 203篇 |
2015年 | 287篇 |
2014年 | 275篇 |
2013年 | 315篇 |
2012年 | 382篇 |
2011年 | 431篇 |
2010年 | 425篇 |
2009年 | 365篇 |
2008年 | 325篇 |
2007年 | 318篇 |
2006年 | 361篇 |
2005年 | 273篇 |
2004年 | 132篇 |
2003年 | 127篇 |
2002年 | 119篇 |
2001年 | 138篇 |
2000年 | 114篇 |
1999年 | 138篇 |
1998年 | 90篇 |
1997年 | 105篇 |
1996年 | 106篇 |
1995年 | 102篇 |
1994年 | 86篇 |
1993年 | 69篇 |
1992年 | 62篇 |
1991年 | 48篇 |
1990年 | 49篇 |
1989年 | 41篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1965年 | 1篇 |
1964年 | 2篇 |
1948年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有6988条查询结果,搜索用时 15 毫秒
21.
Macroautophagy is a cellular degradation mechanism that involves the delivery of cytosolic components (macromolecules or organelles) by the autophagosome to the lysosome for degradation. In mammalian cells, macroautophagy and the ubiquitin proteasome system are 2 major mechanisms to eliminate abnormal proteins accumulated in pathological conditions. Here, the coordination of the 2 pathways to alleviate endoplasmic reticulum stress is reviewed. Also discussed is the regulatory role of macroautophagy and proteasome activity in cell survival and death, as well as the recent discoveries leading to novel strategies of simultaneous control of the proteasome and autophagy activity in anticancer treatment. 相似文献
22.
抗旱耐热白三叶新品种选育初报 总被引:5,自引:0,他引:5
鄂牧一号白三叶是以美国瑞加和路易斯安那两个白三叶品种为原始材料,经单株抗性造反份系比较鉴定,多系混合杂交,品种比较和区域试验选育而成,历时10年。该品种具有高产,抗旱,耐热和粗蛋白含量高等特性,是南方低山丘陵地区有推广应用前景的优良牧草和草坪植物。 相似文献
23.
Rodan I Sundahl E Carney H Gagnon AC Heath S Landsberg G Seksel K Yin S;American Animal Hospital Association 《Journal of Feline Medicine and Surgery》2011,13(5):364-375
BACKGROUND: The number of pet cats is increasing in most countries, often outnumbering pet dogs, yet cats receive less veterinary care than their canine counterparts.(1) Clients state the difficulty of getting the cat into a carrier at home, driving to the clinic, and dealing with the fearful cat at the veterinary clinic as reasons for fewer visits.(2) Educating and preparing the client and the veterinary team with regard to respectful feline handling is necessary in order to avoid stress and accomplish the goal of good health care. Without such preparation, feline stress may escalate into fear or fear-associated aggression. The resulting stress may alter results of the physical examination and laboratory tests, leading to incorrect diagnoses (eg, diabetes mellitus) and unnecessary treatments.(3-5) Without compassionate and respectful handling by the veterinary team, clients may feel the team lacks skills and compassion, or does not understand cats. Injury may occur to the cat, client and/or veterinary team.(6) Clients who want to avoid stress for their cat may avoid veterinary visits or choose another practice instead. GOALS: The use of feline-friendly handling techniques should reduce these problems. Handling is most successful when the veterinary team adapts the approach to each individual cat and situation. The goal of these guidelines is to provide useful information for handling cats that can lead to: ? Reduced fear and pain for the cat. ? Reinforced veterinarian-client-cat bond, trust and confidence, and thus better lifelong medical care for the cat. ? Improved efficiency, productivity and job satisfaction for the veterinary team. ? Increased client compliance. ? Timely reporting and early detection of medical and behavioral concerns. ? Fewer injuries to clients and the veterinary team. ? Reduced anxiety for the client. 相似文献
24.
不同的干燥工艺对荷花蜂花粉功能成分的影响 总被引:1,自引:0,他引:1
探讨了5种干燥工艺对荷花蜂花粉功能成分的影响。微波干燥的干燥效率最高,60%火力处理540s可使水分从31.41%降到6.42%;干燥方式对荷花蜂花粉蛋白质影响较小;微波干燥后总黄酮提取率最高,为13.20mg/g;真空冷冻干燥后维生素C和过氧化氢酶含量最高,分别为48.89mg/100g和29.86mg/g·min。总的来说,真空冷冻干燥对荷花蜂花粉的功能成分影响最小;常压恒温干燥对功能成分影响较小、工艺简单、对设备要求低,宜于大规模应用于实际生产中。 相似文献
25.
日粮添加免疫生长促进剂C96对雏鸡若干血液指标的影响 总被引:1,自引:0,他引:1
选择120只1日龄AA商品健康雏鸡,随机分为4组,每组30只。初步观察了日粮添加免疫生长促进剂C96对血液中红细胞总数(RBC)、比容(PCV)、血红蛋白含量(Hb)、网织红细胞比例(RCC)、白细胞总数(WBC)等的影响。结果表明:肉雏鸡在15d时,日粮添加C96为11mg/kg,饲料的C96组和疫苗-C96组,与对照组和疫苗组比较,RBC和Hb增高,WBC显著下降,RCC降低,PCV无明显规律性变化;30d和45d时,添加C96组和疫苗-C96组的RBC、Hb和PCV,与对照组和疫苗组基本相近,WBC和RCC均比对照组和疫苗组低或明显低。但30d时疫苗组的WBC比对照组高。整个试验期,RBC、WBC和PCV随日龄的增长呈上升趋势,RCC呈波动性下降。 相似文献
26.
27.
28.
Du YH Jia RY Yin ZQ Pu ZH Chen J Yang F Zhang YQ Lu Y 《Veterinary parasitology》2008,157(1-2):144-148
The acaricidal activity of the petroleum ether extract, the chloroform extract and the acetic ether extract of neem (Azadirachta indica) oil against Sarcoptes scabiei var. cuniculi larvae was tested in vitro. A complementary log-log (CLL) model was used to analyze the data of the toxicity tests. The results showed that at all test time points, the petroleum ether extract demonstrated the highest activity against the larvae of S. scabiei var. cuniculi, while the activities of the chloroform extract and the acetic ether extract were similar. The activities of both the petroleum ether extract and the chloroform extract against the larvae showed the relation of time and concentration dependent. The median lethal concentration (LC(50)) of the petroleum ether extract (1.3muL/mL) was about three times that of the chloroform extract (4.1muL/mL) at 24h post-treatment. At the concentrations of 500.0muL/mL, the median lethal time (LT(50)) of the petroleum ether extract and the chloroform extract was 8.4 and 9.6h, respectively. 相似文献
29.
30.
Dietary supplementation with high levels of zinc oxide (ZnO) is an effective method to prevent diarrhea and promote growth in weaned piglets. However, the mechanisms behind these beneficial effects are not well understood. Recent advances in this field indicated that the effects of ZnO on piglet growth are achieved through multiple regulatory pathways rather than a single pathway. This review focuses on recent advances in the effects of high level ZnO on:1) Zn status in weaned piglets;2) intestinal microbe flora regulation;3)intestinal structure and function;4 )ion secretion in the intestine epithelium;5) intestinal immunology; and 6) secretion of brain-intestine peptides. ZnO appears to regulate the intestinal microflora and decreases the release of histamine to prevent diarrhea. ZnO also increases the expression of intestinal insulin-like growth factor-1 (IGF-1) and the IGF-1 receptor to ameliorate intestinal injury associated with weaning, and mediates secretion of brain-gut peptides to stimulate food intake, to promote the growth of piglets. Better understanding of the underlying mechanisms should inspire us to supplement the diet for weaned piglets with ZnO and investigate new approaches to prevent diarrhea and enhance growth. 相似文献