全文获取类型
收费全文 | 6900篇 |
免费 | 604篇 |
国内免费 | 4篇 |
专业分类
林业 | 54篇 |
农学 | 34篇 |
235篇 | |
综合类 | 498篇 |
农作物 | 60篇 |
水产渔业 | 107篇 |
畜牧兽医 | 6398篇 |
园艺 | 40篇 |
植物保护 | 82篇 |
出版年
2023年 | 102篇 |
2022年 | 6篇 |
2021年 | 55篇 |
2020年 | 228篇 |
2019年 | 60篇 |
2018年 | 169篇 |
2017年 | 189篇 |
2016年 | 135篇 |
2015年 | 189篇 |
2014年 | 278篇 |
2013年 | 317篇 |
2012年 | 311篇 |
2011年 | 367篇 |
2010年 | 244篇 |
2009年 | 299篇 |
2008年 | 293篇 |
2007年 | 254篇 |
2006年 | 197篇 |
2005年 | 241篇 |
2004年 | 249篇 |
2003年 | 274篇 |
2002年 | 286篇 |
2001年 | 170篇 |
2000年 | 124篇 |
1999年 | 126篇 |
1998年 | 188篇 |
1997年 | 184篇 |
1996年 | 164篇 |
1995年 | 165篇 |
1994年 | 142篇 |
1993年 | 155篇 |
1992年 | 177篇 |
1991年 | 151篇 |
1990年 | 189篇 |
1989年 | 133篇 |
1988年 | 114篇 |
1987年 | 149篇 |
1986年 | 60篇 |
1985年 | 84篇 |
1984年 | 86篇 |
1983年 | 80篇 |
1982年 | 38篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1972年 | 3篇 |
1965年 | 3篇 |
1963年 | 3篇 |
1956年 | 3篇 |
排序方式: 共有7508条查询结果,搜索用时 31 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.
Glyphosate was recently evaluated for its potential to interact with the estrogen, androgen and thyroid (EAT) hormone pathways, including steroidogenesis, under the United States Environmental Protection Agency's (USEPA) Endocrine Disruptor Screening Program (EDSP), then by Germany, the rapporteur Member State who led the European Annex 1 renewal for glyphosate, and then by the European Food Protection Agency (EFSA) also as part of the Annex 1 renewal for glyphosate. Under the EDSP, 11 Tier 1 assays were run following the USEPA's validated 890‐series test guidelines and included five in vitro and six in vivo assays to evaluate the EAT pathways. Steroidogenesis was evaluated as part of the estrogen and androgen pathways. An up‐to‐date critical review has been conducted that considered results from the EDSP Tier 1 battery, guideline regulatory studies and an in‐depth analysis of the literature studies that informed an endocrine assessment. A strength of this evaluation was that it included data across multiple levels of biological organization, and mammalian and nonmammalian test systems. There was strong agreement across the in vitro and in vivo Tier 1 battery, guideline studies and relevant literature studies, demonstrating that glyphosate does not interact with EAT pathways including steroidogenesis. Based on an analysis of the comprehensive toxicology database for glyphosate and the literature, this review has concluded that glyphosate does not have endocrine‐disrupting properties through estrogen, androgen, thyroid and steroidogenic modes of action. © 2020 Society of Chemical Industry 相似文献
3.
Mayara de Moura Pereira Mariana Machado Evangelista Enric Gisbert Elizabeth Romagosa 《Aquaculture Research》2019,50(8):2181-2190
The aim of this study was to assess the activity of gastric, pancreatic and intestinal digestive enzymes during the embryonic and larval development of Nile tilapia (Oreochromis niloticus) GIFT strain Aqua America® 1 obtained from a broodstock fed two levels of crude protein (CP). A total of 72 females and 24 males, 10 hapas, two CP levels (32% and 38%) and six phases of embryonic (cleavage, blastula, gastrula) and larval (hatching, 7 and 10 days post hatch, dph) stages were used. The eggs were collected in cleavage, blastula and gastrula stages, 300 mg was collected, and kept in cryogenic tubes in liquid nitrogen. For the samples at larval stage, the remaining eggs were separated according to crude protein level and kept in hatcheries and samples were collected on 7 and 10 dph the same way as before. A total of 48 samples were collected: at each protein level (32% and 38% CP), four samples were collected in each phase of embryonic and larval development. Statistical differences were not observed during embryonic development for acid proteases, trypsin, amylase and lipase activity at both levels of crude protein (32 and 38% CP). Differences for acid proteases were noticed on 7 dph; trypsin and amylase on 7 dph and 10 dph. Significant differences on blastula and 7 dph for protease; as for aminopeptidase, there was significant difference on 7 dph. The data indicated early appearance of digestive enzymes in Nile tilapia broodfish receiving 32% CP taking into account the rapid growth and development of this species. 相似文献
4.
5.
Elizabeth A. Fulton Andr E. Punt Catherine M. Dichmont Chris J. Harvey Rebecca Gorton 《Fish and Fisheries》2019,20(1):66-96
Understanding the strengths and weaknesses of alternative assessment methods, harvest strategies and management approaches are an important part of operationalizing single‐species and ecosystem‐based fisheries management. Simulations run using two variants of a whole‐of‐ecosystem model for the Southern and Eastern Scalefish and Shark Fishery (SESSF) area shows that (a) data‐rich assessments outperform data‐poor assessments for target species and that this performance is reflected in the values of many system‐level ecosystem indicators; (b) ecosystem and multispecies management outperforms single‐species management applied over the same domain; (c) investment in robust science‐based fisheries management pays dividends even when there are multiple jurisdictions, some of which are not implementing effective management; and (d) that multispecies yield‐oriented strategies can deliver higher total catches without a notable decline in overall system performance, although the resulting system structure is different to that obtained with other forms of ecosystem‐based management. 相似文献
6.
Barrera-Reyes Paloma K de Lara Josué Cortés-Fernández González-Soto Melissa Tejero M Elizabeth 《Plant foods for human nutrition (Dordrecht, Netherlands)》2020,75(1):1-11
Plant Foods for Human Nutrition - The effects of cocoa-derived polyphenols on cognitive functions have been analyzed through numerous studies using different interventions (doses, vehicles, time... 相似文献
7.
Solis-Badillo Elizabeth Agama-Acevedo Edith Tiessen Axel Lopez Valenzuela Jose A. Bello-Perez Luis A. 《Plant foods for human nutrition (Dordrecht, Netherlands)》2020,75(1):76-82
Plant Foods for Human Nutrition - ADP-glucose pyrophosphorylase (AGPase) is a key enzyme of starch synthesis in seeds, tubers and fruits. UDP-glucose pyrophosphorylase (UGPase) is an important... 相似文献
8.
Yadav Sudhir Mondal Manoranjan K. Shew Aaron Jagadish S. V. Krishna Khan Zahirul Haque Sutradhar Asish Bhandari Humnath Humphreys Elizabeth Bhattacharya Jayanta Parvin Rokhsana Rahman Mahabubur Chandna Parvesh 《Paddy and Water Environment》2020,18(2):331-343
Paddy and Water Environment - Most of the lands of the southern coastal zone of Bangladesh are protected from tidal flooding and storm surges by embankments constructed during the 1960s and 1970s,... 相似文献
9.
10.