全文获取类型
收费全文 | 102263篇 |
免费 | 8119篇 |
国内免费 | 165篇 |
专业分类
林业 | 4338篇 |
农学 | 3237篇 |
基础科学 | 720篇 |
13569篇 | |
综合类 | 15494篇 |
农作物 | 3905篇 |
水产渔业 | 7124篇 |
畜牧兽医 | 53827篇 |
园艺 | 1214篇 |
植物保护 | 7119篇 |
出版年
2021年 | 903篇 |
2020年 | 1291篇 |
2019年 | 1873篇 |
2018年 | 2229篇 |
2017年 | 2440篇 |
2016年 | 2354篇 |
2015年 | 1989篇 |
2014年 | 2331篇 |
2013年 | 4671篇 |
2012年 | 3549篇 |
2011年 | 4163篇 |
2010年 | 2802篇 |
2009年 | 2570篇 |
2008年 | 3631篇 |
2007年 | 3296篇 |
2006年 | 3165篇 |
2005年 | 2823篇 |
2004年 | 2745篇 |
2003年 | 2703篇 |
2002年 | 2413篇 |
2001年 | 2984篇 |
2000年 | 3028篇 |
1999年 | 2327篇 |
1997年 | 851篇 |
1995年 | 1089篇 |
1994年 | 928篇 |
1993年 | 878篇 |
1992年 | 2000篇 |
1991年 | 2139篇 |
1990年 | 1985篇 |
1989年 | 2000篇 |
1988年 | 1881篇 |
1987年 | 1972篇 |
1986年 | 2020篇 |
1985年 | 1934篇 |
1984年 | 1522篇 |
1983年 | 1344篇 |
1982年 | 912篇 |
1979年 | 1415篇 |
1978年 | 1164篇 |
1977年 | 1004篇 |
1976年 | 954篇 |
1975年 | 996篇 |
1974年 | 1306篇 |
1973年 | 1348篇 |
1972年 | 1261篇 |
1971年 | 1176篇 |
1970年 | 1095篇 |
1969年 | 981篇 |
1967年 | 880篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Richard R. Budnik Joseph D. Conroy Richard D. Zweifel Stuart A. Ludsin Elizabeth A. Marschall 《Ecology of Freshwater Fish》2021,30(1):31-47
Rising temperatures caused by climate change are likely to affect cool‐water and warm‐water fishes differently. Yet, forecasts of anticipated temperature effects on fishes of different thermal guilds are lacking, especially in freshwater ecosystems. Towards this end, we used spatially explicit, growth rate potential (GRP) models to project changes in seasonal habitat quality for a warm‐water piscivore (largemouth bass Micropterus salmoides), a cool‐water piscivore (walleye Sander vitreus) and a hybrid piscivore (saugeye S. vitreus × S. canadensis) in two Midwestern reservoirs. We assessed habitat quality for two periods (early and middle 21st century) under two realistic greenhouse gas emission scenarios (a mid‐century emissions peak and a rapid continuous increase in emissions). Largemouth bass were projected to experience enhanced or slightly reduced habitat during all seasons, and throughout the mid‐21st century. By contrast, walleye habitat was projected to decline with anticipated warming, except during the spring in the smaller of our two study reservoirs and during the fall in the larger of our two study reservoirs. Saugeye habitat was projected to either increase modestly or decline slightly during the spring and fall and declines in habitat quality and quantity that were smaller than those for walleye were identified during summer. Collectively, our findings indicate that climate warming will differentially alter habitat suitability for reservoir piscivores, favouring warm‐water species over cool‐water species. We expect these changes in habitat quality to impact the dynamics of reservoir fish populations to varying degrees necessitating the consideration of climate when making future management decisions. 相似文献
2.
Maureen A. Griffin Ingrid M. Balsa Philipp D. Mayhew 《The Canadian veterinary journal. La revue veterinaire canadienne》2021,62(6):572
A 7-month-old, intact male, mixed breed dog with bilateral inguinal hernias underwent general anesthesia for laparoscopic bilateral inguinal herniorrhaphy via a 3-port approach. A 3-dimensional laparoscopic system was used to perform the procedure immediately following prescrotal open castration. Intracorporeal suturing with polypropylene was performed, and 2 cruciate sutures were placed to close each inguinal ring. The caudal aspect of each inguinal ring was left slightly open so as not to disrupt the passage or patency of vessels and nerves. No intra- or post-operative complications occurred. One year after surgery, the dog has no evidence of recurrence of the inguinal hernias.Key clinical message:This case report demonstrates a novel minimally invasive approach to inguinal herniorrhaphy in a dog with no reported complications and a good long-term outcome. Intracorporeally sutured inguinal herniorrhaphy is feasible in dogs with good results, although additional cases are needed to gain experience with this technique in dogs with varying presentations of inguinal hernias. 相似文献
3.
4.
5.
6.
7.
8.
Gustavo Pereira Valani Aline Fachin Martíni Laura Fernanda Simes da Silva Renata Cristina Bovi Miguel Cooper 《Soil Use and Management》2021,37(1):22-36
Integrated crop–livestock–forest is a promising strategy to improve soil quality. It comprises four different integrated farming systems: crop–livestock, crop–forest, forest–livestock and crop–livestock–forest. This work systematically reviewed studies about integrated crop–livestock–forest systems and soil quality. A total of 92 papers were retrieved from the Web of Science—Clarivate Analytics platform, and the following information was analysed: publication year, institution, region of the studied site, type of integrated system, soil type, tillage system, maximum soil depth and the soil quality indicators assessed. Most studies were published in the second half of the 2010s. Brazil is a prominent focus of research about soil quality and integrated crop–livestock–forest systems, with significant contribution from its central and southern regions. The Embrapa was the main publishing institution, present in over one‐third of the studies. Crop–livestock was the most common integrated system, Ferralsols was the most common soil group, and most of the studied soils were clayey. No tillage was the main tillage system. Most studies focused on the topsoil, assessing physical and/or chemical soil quality indicators. More emphasis on biological indicators of soil quality is required, as well as assessments integrating biological, physical and chemical indicators of soil quality. Future works should compare different integrated systems, including assessments deeper in the soil profile, especially in systems with the forest component, and also in sandy and silty soils. Soil quality indicators that have been rarely used should be further tested. Novel indicators should be added to better understand the promotion of soil quality by integrated crop–livestock–forest systems. 相似文献
9.
D R Clements M D Day V Oeggerli S C Shen L A Weston G F Xu F D Zhang X Zhu 《Weed Research》2019,59(3):155-169
Increasingly, weeds have been taking on global distributions. With the proliferation of invasive weeds has come the challenge of managing these species over broad geographical regions, with diverse habitats and political jurisdictions. Here, we review the management of Mikania micrantha Kunth (Asteraceae; mile‐a‐minute) throughout its invaded range, extending through most of the Pacific islands and southern and south‐east Asia. Context matters when determining the best course of action for managing M. micrantha, as it has invaded a large variety of agricultural and natural systems. In Queensland, Australia and Florida, USA, M. micrantha has been targeted in relatively successful eradication campaigns, highlighting the importance of early detection and rapid response methods, while elsewhere in its invaded range, populations are either still increasing or showing limited signs of decline. An inter‐regional approach to research and management should incorporate successful management strategies employed throughout the invaded range including, but not limited to, chemical and cultural control practices, manual and mechanical control, classical biological control using the rust fungus Puccinia spegazzinii, plant–plant competition and integrated approaches utilising two or more control methods concurrently. Additional knowledge of M. micrantha genetics is required to determine if management approaches could be fine‐tuned for particular populations. Countries bordering the Mekong River formed a network in 2011 to co‐ordinate the management of invasive species such as M. micrantha. Expanding such a collaborative approach to other regions could further reduce populations of M. micrantha and limit its spread. 相似文献
10.