全文获取类型
收费全文 | 82374篇 |
免费 | 21067篇 |
国内免费 | 1062篇 |
专业分类
林业 | 11490篇 |
农学 | 6645篇 |
基础科学 | 5231篇 |
11950篇 | |
综合类 | 46130篇 |
农作物 | 4374篇 |
水产渔业 | 2443篇 |
畜牧兽医 | 8041篇 |
园艺 | 3530篇 |
植物保护 | 4669篇 |
出版年
2025年 | 930篇 |
2024年 | 1853篇 |
2023年 | 1893篇 |
2022年 | 2304篇 |
2021年 | 2430篇 |
2020年 | 2492篇 |
2019年 | 2993篇 |
2018年 | 1757篇 |
2017年 | 2932篇 |
2016年 | 3642篇 |
2015年 | 3168篇 |
2014年 | 4477篇 |
2013年 | 4429篇 |
2012年 | 6559篇 |
2011年 | 6812篇 |
2010年 | 5505篇 |
2009年 | 5428篇 |
2008年 | 5031篇 |
2007年 | 5918篇 |
2006年 | 5203篇 |
2005年 | 4335篇 |
2004年 | 3330篇 |
2003年 | 2906篇 |
2002年 | 2247篇 |
2001年 | 2029篇 |
2000年 | 1871篇 |
1999年 | 1475篇 |
1998年 | 1285篇 |
1997年 | 1177篇 |
1996年 | 1118篇 |
1995年 | 1104篇 |
1994年 | 1055篇 |
1993年 | 880篇 |
1992年 | 845篇 |
1991年 | 713篇 |
1990年 | 642篇 |
1989年 | 555篇 |
1988年 | 438篇 |
1987年 | 307篇 |
1986年 | 148篇 |
1985年 | 60篇 |
1984年 | 37篇 |
1983年 | 25篇 |
1982年 | 22篇 |
1981年 | 25篇 |
1980年 | 26篇 |
1979年 | 20篇 |
1978年 | 21篇 |
1976年 | 15篇 |
1962年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
以本校的民族地方文献资源为例,提出了民族高校图书馆在民族地方文献的宣传以及开发利用方面应采取的措施。 相似文献
32.
从高等院校新校区建设的重要性入手,分析了当前基本建设资金的现状。高等院校新校区建设资金需要多渠道筹资。通过对筹资的渠道以及筹资的方式的研究,并结合河北师大的特例,探讨了更有效的项目筹资方式。 相似文献
33.
《Communications in Soil Science and Plant Analysis》2012,43(15-20):2249-2264
Abstract Australia's reef water quality protection plan has a key objective: “reduce the load of pollutants from diffuse sources in the water entering the Reef.” This article reports on a survey to assess the contemporary phosphorus (P) status of fertilized cropping soils across 21 catchments in coastal Queensland, Australia. The survey focused on surface soils from cane farms, vegetable and subtropical/tropical fruit tree sites. There were sampling depth effects on P levels in sugar and fruit tree sites (lower with depth). Importantly, 84% of 105 sugarcane sites were excessively fertile and only 3% rated low (P deficient). Some 75% of 16 vegetable sites and 38% of 8 fruit tree sites had excess ratings for extractable soil P fertility. Highest total P levels (0–10 cm) occurred in fruit tree sites, followed by vegetable and sugarcane soils. There are regional differences in P soil fertility, and the recycling of mill by‐products needs attention. Part 2 (Bloesch and Rayment 2006) examines the potential of these soils to release soluble P in a nutrient‐sensitive area. 相似文献
34.
食品物性学是一门重理论基础,实践性强,涉及面广的课程。该文介绍了我国食品物性学课程教学和研究现状,并提出了提升食品特性学课程的教学质量措施。主要包括:借举国内外教学成果、与多学科相融合、加强实践教学等。 相似文献
35.
Florian Grisel 《Fish and Fisheries》2019,20(3):419-433
This paper offers a socio‐historical study of the Prud'homie de pêche (the “Prud'homie”), a common‐pool institution (“CPI”) that has managed the fishery commons at Marseille since the Middle Ages. The evidence presented here sheds light on specific challenges faced by the Prud'homie during the early stages of globalization: one challenge is the import of a new fishing technique (the madrague) in the early 17th century, and another challenge is the arrival of migrant fishermen from Catalonia throughout the 18th century. On this basis, this paper explores the ways in which globalization has impacted the Prud'homie and identifies the mechanisms through which these challenges might threaten the functioning of CPIs. 相似文献
36.
37.
Wim Salomons 《Journal of Soils and Sediments》2005,5(1):2-8
- Dedicated to Prof. Dr. Ulrich Förstner on his 65th birthdayBackground Sediments pose problems at their deposition sites when there is too little sediment (e.g. wetlands) or too much sediment (e.g. navigable waterways) and, additionally, when they are contaminated. These problems often have their origin upstream in the river catchment. Objective Global aspects of changes concerning sediment quantity and quality, as they affect downstream areas, are reviewed. A case study of estuarine sediments demonstrates how a holistic approach helps in understanding and predicting their present and future quality. Results and Conclusions Globally, large reservoirs intercept between 25 and 30% of the sediment and consequently supply the coast with impacts on wetlands and coastal morphology. In estuaries, the composition of sediments is determined by the mixing of marine sediments supplied from the coast and the supply by rivers. Natural tracers can be used to predict mixing ratios of marine to fluvial sediments in estuaries, and hence their contamination. Scenarios on implementation of pollution abatement, the implementation of regulations as well as climate change are needed to predict future sediment quality in downstream areas. The results show, even for a ‘green’ scenario, that sediment quality in the Rhine catchment will pose future problems due to the temporal storage of contaminants in soils and sediments.Recommendations and Outlook The current methods applied make use of existing models linking sediment transport with point and diffuse sources in the river catchments and scenarios on the development of strength of point and diffuse sources. However, more effort is needed to come to a uniform framework which includes land use changes and links with more advanced scenario methodology for long to medium-term management of sediment quality and quantity in river catchments. 相似文献
38.
Rachayya M. Devarumath Sachin B. Kalwade Peter Bundock Frances G. Eliott Robert Henry 《Plant Breeding》2013,132(6):736-747
The independent target region amplification polymorphism (TRAP) and single‐nucleotide polymorphism (SNP) marker s were used for genetic evaluation of different selected 47 sugarcane genotypes. A total of 23 pairs of TRAP markers generated 925 alleles, of which 74% alleles were polymorphic. Polymorphism was generally high (>50%), ranging from 54 to 98%. The polymorphism information content (PIC) values 0.20 varied among the primer combination ranging from 0.17 in SAI + Arbi 2 to 0.31 in GL 2+ Arbi 1 with an average of 0.24. However, the Pearson correlation between PIC and power of discrimination (PD) was found to be less significant. Single‐nucleotide polymorphisms were used first time for the assessment of genetic diversity among different species of Saccharum and cultivated sugarcane varieties. The SNPs were detected from 454 sequencing. A total of 245 SNP markers were assayed across the 47 genotypes, and 167 SNPs were found to be polymorphic. The PIC values ranged from 0.04 to 0.38 with an average of 0.21, and their respective PD varied from 0.58 to 0.04 with an average value of 0.31. The obtained results relatively significant were compared with the other marker systems through genetic similarity and the clusters formed in different unweighted pair group method with arithmetic mean clustering dendrogram. The clustering analysis established genetic relationship in the order of Erianthus > Sclerostachya > Narenga > Saccharum spontaneum > S. robustum > S. barberi > S. officinarum/cultivars. These results ratify TRAP and SNP marker systems for assessing genetic diversity studies, and more diversified Erianthus spp. can contribute substantially towards sugarcane varietal improvement through breeding with Saccharum spp. or hybrid cultivars. 相似文献
39.
学科馆员制:信息时代党校图书馆服务方式的创新 总被引:2,自引:0,他引:2
邓蓉敬 《农业图书情报学刊》2009,21(3):187-189
学科馆员制度的建立是党校图书馆在信息社会实现主动性、个性化服务的需要。本文结合党校特点,分析了在党校图书馆建立学科馆员制的必要性和主要实现途径。 相似文献
40.
Mirja Ruohoniemi DVM Marjatta Karkkainen Dr.med.vet Pekka Tervahartiala MD PhD 《Veterinary radiology & ultrasound》1997,38(5):344-351
Six Finnhorse cadaver forefeet were selected to represent radiographically different types and grades of ossification of the collateral cartilages of the distal phalanx. These cartilages and adjacent tissues were evaluated with computed tomography (CT) and high field magnetic resonance imaging (MRI). In CT the internal structure of the cartilages was consistent, but in MRI some differences were noted. The shape of the collateral cartilages and their ligamentous attachments varied. The border between ossified and non-ossified cartilage appeared distinct, with considerable variation in the extent of the ossified area in regard to the cross-sectional area of the cartilage. Ossification originating from the palmar processes and extending in the proximaVpalmaroproximal direction, without separate centers of ossification, generally appeared smooth and inactive. Palmar ossification followed the irregular shape of the cartilage. Separate centers of ossification had a medullary cavity or were sclerotic. Presence ofamedullary cavity or sclerosis were also found at the base of the cartilages. The incomplete fusion lines between separate centres of ossification and the ossified base of the cartilage varied from congruent and inactive to reactive with marked sclerosis, flared margins and parachondral changes. Incomplete fusion may be clinically significant. Local conformational adaptations of the hoof were also documented with extensive ossification of the collateral cartilage. 相似文献