全文获取类型
收费全文 | 1216篇 |
免费 | 47篇 |
国内免费 | 1篇 |
专业分类
林业 | 476篇 |
农学 | 28篇 |
基础科学 | 3篇 |
183篇 | |
综合类 | 33篇 |
农作物 | 96篇 |
水产渔业 | 47篇 |
畜牧兽医 | 310篇 |
园艺 | 31篇 |
植物保护 | 57篇 |
出版年
2023年 | 8篇 |
2022年 | 14篇 |
2021年 | 44篇 |
2020年 | 30篇 |
2019年 | 23篇 |
2018年 | 24篇 |
2017年 | 28篇 |
2016年 | 33篇 |
2015年 | 22篇 |
2014年 | 29篇 |
2013年 | 47篇 |
2012年 | 46篇 |
2011年 | 58篇 |
2010年 | 43篇 |
2009年 | 32篇 |
2008年 | 35篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 34篇 |
2004年 | 37篇 |
2003年 | 31篇 |
2002年 | 28篇 |
1997年 | 24篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 16篇 |
1993年 | 12篇 |
1992年 | 22篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1982年 | 13篇 |
1981年 | 26篇 |
1979年 | 25篇 |
1978年 | 8篇 |
1936年 | 7篇 |
1935年 | 12篇 |
1934年 | 7篇 |
1933年 | 12篇 |
1932年 | 16篇 |
1931年 | 10篇 |
1930年 | 15篇 |
1929年 | 8篇 |
1928年 | 7篇 |
1927年 | 11篇 |
1925年 | 13篇 |
1917年 | 7篇 |
排序方式: 共有1264条查询结果,搜索用时 15 毫秒
51.
52.
OBJECTIVE: To report outcome in 13 dogs with distal radial osteosarcoma, without evidence of metastasis, treated by a combination of adjuvant chemotherapy and a pasteurized autograft limb-sparing procedure. STUDY DESIGN: Prospective clinical study. ANIMALS: Thirteen dogs with distal radial osteosarcoma. METHODS: Limb-sparing procedure was performed using an autograft from the excised tumoral segment, pasteurized at 65 degrees C for 40 minutes. Adjuvant chemotherapy (cisplatin or cisplatin and doxorubicin) was administered in all dogs. RESULTS: Mean and median survival times were 531 and 324 days, respectively (range, 180 to 1,868 days). Overall survival was 100% at 6 months, 50% at 12 months, 44% at 18 months, and 22% at 24 months. Lung metastasis occurred in 5 (38%) dogs. Observed complications were local recurrence (2 dogs, 15%), allograft infection (4 dogs, 31%), and implant failure (3 dogs, 23%). Limb function was good in 12 dogs (92%) and fair in 1 dog. CONCLUSIONS: Pasteurized bone autograft derived from the tumoral bone segment was an effective alternative to cortical bone allograft for limb sparing in canine distal radial osteosarcoma, in terms of feasibility, pattern of healing, complications, and survival. CLINICAL RELEVANCE: Use of a pasteurized bone autograft eliminates the need for a canine bone allograft bank and has the added advantage of good fit to the recipient site. 相似文献
53.
Marina A. Lima Domingos S. C. Paciullo Mirton J. F. Morenz Carlos A. M. Gomide Renato A. R. Rodrigues Fernanda H. M. Chizzotti 《Grass and Forage Science》2019,74(1):160-170
Silvopastoral system (SPS) has been suggested to ensure sustainability in animal production systems in tropical ecosystems. The objective of this study was to evaluate the productive and nutritive value traits of Brachiaria decumbens and performance of dairy heifers in SPS and open pasture (OP) during the summer and autumn of two consecutive years in the SPS and OP (17th and 18th years after establishment). Experimental design was a randomized complete block with two treatments (SPS and OP) and three replications in subdivided plots with repeated measures in time. There was reduction in the tiller population density, total and green forage mass, and total and green forage bulk density in the SPS when compared to the OP in the summer. In the autumn, no difference was observed between the systems. Shading in SPS increased crude protein content of the grass pasture by 25% and 33% when compared to the OP during the first and second experimental years, respectively, and reduced neutral detergent fibre content. However, it did not change acid detergent fibre or lignin content. OP provided higher stocking rate and weight gain per area than the SPS. Average daily gain was higher in the OP in the second experimental year. Severe shading conditions should be avoided, because in the long ‐ term they may threaten the persistence and sustainability of pasture in the SPS. It is recommended to plant a low density of trees or implement management strategies of the tree component by either thinning or pruning over the years after planting. 相似文献
54.
Vesna Zupanc Gerhard Kammerer Helena Gr
man Igor antavec Rozalija Cveji Marina Pintar 《Land Degradation \u0026amp; Development》2016,27(2):406-415
Hydropower plants on the lower river Sava, Slovenia, were developed without sealing the underground upstream. As a consequence, without the countermeasures of elevating and recultivating, the agricultural land on the river banks would be inundated because of the water‐table increase of the river. To remedy this, the fields were elevated and recultivated. The goal of this study was to assess soil quality and production potential after land raising and recultivation and to answer the question whether it is possible to recover soil quality and crop yield after large‐scale mass manipulation, such as land raising. After recultivation and after the second year of land reuse for the two cultures grass–clover mixture and corn on two sites, Middle Pijavsko and Lower Pijavsko, soil physical and chemical characteristics and crop yields were evaluated. Mixing of topsoil with the second horizon during removal and during backfill with filling material resulted in uneven soil fertility, plant growth and decreased yield. Driving on the refilled second layer with heavy machinery caused soil compaction in the Middle Pijavsko in spite of favourable soil texture (loam, 38·7% sand). On the areas with very high sand content (over 55%) and low clay content (10%), soil compaction was not as severe or persistent. Recultivation measures restored the agricultural land almost to the production potential prior to powerplant construction. Immediate intensive land use (corn) showed less favourable effect on soil characteristics. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
55.
Antioxidant activity of anthocyanins and their aglycons 总被引:13,自引:0,他引:13
The antioxidant activity of the six common anthocyanidins, pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin, and their glycosidic forms was evaluated in three lipid-containing models [human low-density lipoprotein (LDL) and bulk and emulsified methyl linoleate]. In addition, the radical scavenging activity of the compounds against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was studied. Most anthocyanins and their aglycons acted as strong antioxidants in emulsion and LDL. Many compounds showed an activity comparable to the well-known antioxidants alpha-tocopherol, Trolox, catechin, and quercetin. In bulk methyl linoleate, anthocyanins and anthocyanidins possessed only a weak antioxidant activity or even oxidation-promoting activity. Depending on the anthocyanidin, different glycosylation patterns either enhanced or diminished the antioxidant power. For the most part, the activities of the glycosides and the aglycons did not differ remarkably in emulsion. In LDL the aglycons showed in general higher activities than the glycosides. In bulk oil, to the contrary, the glycosides were more effective than the aglycons. 相似文献
56.
57.
Prof. Dr. H. Weidner 《Journal of pest science》1985,58(4):65-68
Zusammenfassung Rote Würmer, die in Chroniken dreier benachbarter Städte Nordostbayerns als Schädlinge an Gersten und Weizen im Jahr 1692/93 beschrieben wurden, werden als Larven der Sattelmücke,Haplodiplosis equestris (Wagner) interpretiert. Feuchter toniger Boden, kaltes feuchtes Wetter und Anwesenheit vonAgropyron repens (L.) P. B. als Reservoir waren die Voraussetzungen für ihre Massenentwicklung, die bei kontinuierlicher gleichbleibender Fruchtfolge zur Vernichtung der ganzen Ernte führten.
Haplodiplosis equestris (Wagner, 1871) a barley and wheat pest in northeastern Bavaria in the years 1692 and 1693 (Diptera, Cecidomyiidae)
Red vermicules described as barley and wheat pests in cronicles of three neighbouring towns in northeastern Bavaria in the end of 17th century are interpreted as larves ofHaplodiplosis equestris (Wagner, 1871). Moist clayish soil, cold damp weather, and presence ofAgropyron repens (L.), P. B. as a reservoir supposed continuous fruit following caused mass development of the populations and destruction of the whole crop.相似文献
58.
59.
Prof. LUO You-qing 《中国林学(英文版)》2008,10(1):I0003-I0003
About 8.7 million hm^2 of forests in China was ravaged by plant diseases and insect pests each year, resulting in an economic loss of RMB 88 billion. Global warming, frequent abnormal weather and closer international economic and trade ties have aggravated the damage of plant diseases and insects on China's forests over the past few years. 相似文献
60.
Prof. Dr. W. Bäumler 《Journal of pest science》1992,65(4):65-67
Zusammmenfassung Im Rahmen der amtlich vorgeschriebenen Prüfung von Rodentiziden wurde beobachtet, daß Jungtiere der Rötelmaus und der Erdmaus, die noch im Familienverband mit ihren Eltern leben, besonders häufig köderscheu werden. Offensichtlich ermöglicht das Lernverhalten der Jungtiere bei der Nahrungsaufnahme der Eltern ein allmähliches Kennenlernen geeigneter oder ungeeigneter Nahrung. Die Jungtiere nehmen häufig feine Nahrungspartikel von den Lippen, insbesondere des Muttertieres auf. Somit können sie allmählich auch Erfahrungen über die Wirkung von akut wirksamen Rodentiziden sammeln, ohne selbst eine letale Dosis aufzunehmen. Hinweise über eine weitergehende Informationsübertragung, die zur Köderscheu führen kann, wurden nicht gefunden.
Mit einer Tabelle 相似文献
Bait shyness of voles
Some rodents like the Common Vole (Microtus agrestis) and the Bank Vole (Clethrionomys glareolus) can cause severe damages in forest cultivations and orchards by gnawing roots and bark of the trees. Among other countermeasures zinc phosphide baits are used to prevent losses. However, some individuals get bait shy against the used acute poison usually. It was observed in some choice tests that young voles can learn very easily from her parents to avoid baits which contain an acute poison. The nestlings are licking the lips especially of her mother during food consumption. In this way they can get some information about palatable and non-palatable food items. Young voles living in her family can become bait shy rapidly during the learning and food imprinting process.
Mit einer Tabelle 相似文献