全文获取类型
收费全文 | 1510篇 |
免费 | 110篇 |
国内免费 | 2篇 |
专业分类
林业 | 117篇 |
农学 | 41篇 |
基础科学 | 6篇 |
313篇 | |
综合类 | 168篇 |
农作物 | 47篇 |
水产渔业 | 235篇 |
畜牧兽医 | 505篇 |
园艺 | 62篇 |
植物保护 | 128篇 |
出版年
2024年 | 6篇 |
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 29篇 |
2020年 | 37篇 |
2019年 | 53篇 |
2018年 | 53篇 |
2017年 | 48篇 |
2016年 | 61篇 |
2015年 | 58篇 |
2014年 | 44篇 |
2013年 | 83篇 |
2012年 | 101篇 |
2011年 | 109篇 |
2010年 | 91篇 |
2009年 | 70篇 |
2008年 | 94篇 |
2007年 | 82篇 |
2006年 | 89篇 |
2005年 | 77篇 |
2004年 | 71篇 |
2003年 | 79篇 |
2002年 | 55篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有1622条查询结果,搜索用时 15 毫秒
951.
Ariadna Chediack Patrick J Liesch Hailey N Shanovich Brian H Aukema 《Journal of insect science (Online)》2022,22(4)
There is a lack of knowledge of the arthropod communities in both wild hazelnut and cultivated hybrid hazelnut ecosystems in the Midwestern United States. Our goal was to characterize the composition of these arthropod communities in hazelnut plantings. We surveyed six experimental plantings of hazelnuts in Wisconsin and two in Minnesota during growing seasons, from May 2017 to August 2021. We used four methods to survey the arthropod community of these plantings: ad libitum survey of specimen observations and collection, dissection of hazelnut buds and nuts, cone traps placed on the ground, and beat sheet sampling of plants. We registered 116 different morphospecies of five classes and 83 families. Arthropods with known feeding habits were grouped into four guilds: 59 herbivores, 36 carnivores (predators, parasites, and parasitoids), 4 decomposers (detritivores and scavengers), and 4 omnivores. While we registered 12 herbivorous species that could potentially cause damage to hazelnuts, we directly observed nine of them feeding upon or damaging plant parts: Phytoptus avellanae s.l. Nalepa (Eriophyoidea: Phytoptidae), Curculio obtusus Blanchard and Strophosoma melanogrammum Förster (Coleoptera: Curculionidae), Popillia japonica Newman (Coleoptera: Scarabeidae), Parthenolecanium sp. (Hemiptera: Coccidae), Euschistus servus euschistoides Say (Hemiptera: Pentatomidae), aphids (Hemiptera: Aphididae), Acleris sp., and Choristoneura rosaceana Harris (Lepidoptera: Tortricidae). We also registered eight species of parasites or parasitoids that could offer biocontrol services in the cropping system. These findings provide a foundation for future targeted studies on potential pests and beneficial arthropods, as well as ecological interactions within the hybrid hazelnut ecosystem in the Midwest. 相似文献
952.
Neil Wang S N M Mandiki Emilie Henrotte Abdel-Ghany Bouyahia Guillaume Mairesse Carole Rougeot Charles Melard & Patrick Kestemont 《Aquaculture Research》2009,40(3):376-383
The aim of this preliminary study was to evaluate the influence of different feeding regimes on the quality of reproduction in pikeperch. Three diets were tested: forage fish (FF), a commercial dry feed (DD) and a mix of both (FD). The diets were given to fish throughout a complete reproductive cycle. During the spawning season, couples were injected with human chorionic gonadotropin (hCG) and let to spawn on nests. Proportion of running males, spawning and hatching success and larval quality (weight, length, body protein, total lipid, fatty acid and lipid class compositions and resistances to osmotic shock and starvation stress tests at hatching) were evaluated. The proportion of running male was lower in the DD group than in the FF and FD groups (54% for DD against 76–89% for FF and FD). In addition, 25%, 62.5% and 75% of injected couples gave spawning that hatched in DD, FF and FD groups respectively. Larval quality parameters were not significantly different between treatments. The results indicate that overall quality of reproduction was higher in FF and FD treatments than in DD. It suggests that the dry feed used was not totally adequate for pikeperch reproduction. Relations between breeder reproductive performances and the feed compositions are discussed. 相似文献
953.
Robert T. Cooney J. R. Allen M. A. Bishop D. L. Eslinger T. Kline B. L. Norcross C. P. Mcroy J. Milton J. Olsen V. Patrick A. J. Paul D. Salmon D. Scheel G. L. Thomas S. L. Vaughan T. M. Willette 《Fisheries Oceanography》2001,10(Z1):1-13
Five years of field, laboratory, and numerical modelling studies demonstrated ecosystem‐level mechanisms influencing the mortality of juvenile pink salmon and Pacific herring. Both species are prey for other fishes, seabirds, and marine mammals in Prince William Sound. We identified critical time‐space linkages between the juvenile stages of pink salmon and herring rearing in shallow‐water nursery areas and seasonally varying ocean state, the availability of appropriate zooplankton forage, and the kinds and numbers of predators. These relationships defined unique habitat dependencies for juveniles whose survivals were strongly linked to growth rates, energy reserves, and seasonal trophic sheltering from predators. We found that juvenile herring were subject to substantial starvation losses during a winter period of plankton diminishment, and that predation on juvenile pink salmon was closely linked to the availability of alternative prey for fish and bird predators. Our collaborative study further revealed that juvenile pink salmon and age‐0 herring exploit very different portions of the annual production cycle. Juvenile pink salmon targeted the cool‐water, early spring plankton bloom dominated by diatoms and large calanoid copepods, whereas young‐of‐the‐year juvenile herring were dependent on warmer conditions occurring later in the postbloom summer and fall when zooplankton was composed of smaller calanoids and a diversity of other taxa. The synopsis of our studies presented in this volume speaks to contemporary issues facing investigators of fish ecosystems, including juvenile fishes, and offers new insight into problems of bottom‐up and top‐down control. In aggregate, our results point to the importance of seeking mechanistic rather than correlative understandings of complex natural systems. 相似文献
954.
Patrick Hainfellner Rafael Yutaka Kuradomi Thiago Gonalves de Souza Rafael Tomoda Sato Daniel Guimares Figueiredo‐Ariki Guilherme Antnio de Freitas Luciano Queiroz Wagner C. Valenti Patricia Moraes Valenti Wei Ge Sergio Ricardo Batlouni 《Aquaculture Research》2019,50(11):3382-3391
We evaluated the annual process of oocyte and ovarian development of the planktivorous Amazonian catfish, the mapará (Hypophthalmus marginatus), aiming to support captive reproduction for domestication. A total of 149 females were captured from the Tocantins River at the Tucuruí Dam (3°49'55"S, 49°39'9"W) in 13 sampling events. For each individual, we evaluated ovary histology and plasma steroid concentrations. Two annual reproductive cycles, with similar characteristics, including a long period of rest, a short vitellogenic stage and a well‐defined spawning season from November to March, were described. A 17β‐estradiol (E2) rise and a 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) peak were associated with vitellogenesis and spawning season, respectively, in the first cycle but not in the second reproductive cycle. In conclusion, the studied species presents a reproductive cycle similar to that of other migratory total spawners; however, unusually for this group of fish, there were three (but not two) batches of vitellogenic oocytes in “in maturation” and “mature” stage ovaries, pointing to the possibility of more than one spawn during the spawning season. 相似文献
955.
956.
Foley P Foley JE Levy JK Paik T 《Journal of the American Veterinary Medical Association》2005,227(11):1775-1781
OBJECTIVE: To evaluate 2 county trap-neuter-return (TNR) programs for feral cat population management via mathematical modeling. DESIGN: Theoretical population model. ANIMALS: Feral cats assessed from 1992 to 2003 in San Diego County, California (n = 14,452), and from 1998 to 2004 in Alachua County, Florida (11,822). PROCEDURE: Data were analyzed with a mathematical Ricker model to describe population dynamics of the feral cats and modifications to the dynamics that occurred as a result of the TNR programs. RESULTS: In both counties, results of analyses did not indicate a consistent reduction in per capita growth, the population multiplier, or the proportion of female cats that were pregnant. CONCLUSIONS AND CLINICAL RELEVANCE: Success of feral cat management programs that use TNR can be monitored with an easily collected set of data and statistical analyses facilitated by population modeling techniques. Results may be used to suggest possible future monitoring and modification of TNR programs, which could result in greater success controlling and reducing feral cat populations. 相似文献
957.
J. Illingworth F.M. Patrick P. Redfearn D.M. Rodley 《Aquaculture (Amsterdam, Netherlands)》1979,17(2):181-187
A commercially available diatomaceous earth filter has been successfully modified for microfiltering sea water used to grow bivalve larvae. The filter consistently removes up to 96% of the suspended matter in the water down to at least 2.3 microns, and reduces the number of heterotrophic bacteria to between 1 and 5 × 102 ml?1. Growth and development of bivalve larvae in this water is excellent. 相似文献
958.
959.
This study examined whether urban Chinese consumers with stronger environmental values have higher valuations for plastic beverage bottles that are made of post-consumer recycled material(rPET) or that come in large sizes that use plastic more efficiently. It also assesses the effectiveness of environmental information provision and green identity labeling in increasing consumer willingness to pay for environmentally-friendly packaging. The results suggest that urban Chinese consumers are willin... 相似文献
960.
Engineering investigation of design procedures for closed containment marine aquaculture systems 总被引:1,自引:0,他引:1
The objective of this paper is to investigate potential design procedures for rigid, closed containment aquaculture systems deployed in the marine environment. In this context, closed containment is a term used to describe a range of aquaculture technologies that attempt to restrict and control interactions between farmed fish and the external aquatic environment, with the goal of minimizing impacts. The containment units are often closely spaced and moored to the seafloor bottom. The geographical area of interest is the Straits of Georgia, British Columbia in Canada.In this study, the design configurations of multiple closed containment systems are investigated. The design procedures include examining: (1) local environmental conditions, (2) drag forces on multiple containment units, (3) wave loading, (4) undamped heave motions, (5) mooring gear components and (6) material stresses on a rigid containment structure. Operational and other design considerations are also discussed. Preliminary findings indicate that wave forces could be substantial. In addition, little is known about how containment units, which are closely spaced, will respond individually or as a farm when subjected to surface waves. 相似文献