全文获取类型
收费全文 | 5139篇 |
免费 | 447篇 |
国内免费 | 2篇 |
专业分类
林业 | 302篇 |
农学 | 40篇 |
基础科学 | 11篇 |
407篇 | |
综合类 | 124篇 |
农作物 | 69篇 |
水产渔业 | 138篇 |
畜牧兽医 | 4303篇 |
园艺 | 40篇 |
植物保护 | 154篇 |
出版年
2023年 | 53篇 |
2021年 | 25篇 |
2020年 | 153篇 |
2019年 | 27篇 |
2018年 | 162篇 |
2017年 | 145篇 |
2016年 | 121篇 |
2015年 | 147篇 |
2014年 | 209篇 |
2013年 | 297篇 |
2012年 | 250篇 |
2011年 | 212篇 |
2010年 | 178篇 |
2009年 | 242篇 |
2008年 | 176篇 |
2007年 | 160篇 |
2006年 | 141篇 |
2005年 | 125篇 |
2004年 | 168篇 |
2003年 | 135篇 |
2002年 | 171篇 |
2001年 | 158篇 |
2000年 | 116篇 |
1999年 | 111篇 |
1998年 | 118篇 |
1997年 | 90篇 |
1996年 | 94篇 |
1995年 | 116篇 |
1994年 | 74篇 |
1993年 | 111篇 |
1992年 | 131篇 |
1991年 | 141篇 |
1990年 | 130篇 |
1989年 | 102篇 |
1988年 | 100篇 |
1987年 | 98篇 |
1986年 | 82篇 |
1985年 | 68篇 |
1984年 | 52篇 |
1983年 | 56篇 |
1982年 | 31篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1973年 | 18篇 |
1972年 | 16篇 |
1971年 | 13篇 |
1970年 | 12篇 |
1969年 | 12篇 |
1967年 | 12篇 |
1929年 | 28篇 |
排序方式: 共有5588条查询结果,搜索用时 15 毫秒
111.
112.
M. Ryan Smith DVM DACVECC Virginie A. Wurlod MS Dr vet med DACVECC DECVECC Chin-Chi Liu MS MApStat PhD 《Journal of Veterinary Emergency and Critical Care》2023,33(6):648-655
Objective
To describe hemostatic derangements associated with canine anaphylaxis and to assess for association with syndrome severity.Design
Prospective observational study.Setting
University teaching hospital.Animals
Twenty-seven client-owned dogs, recruited from November 2018 to January 2022, diagnosed with anaphylaxis of varying severity were included. Study inclusion required presentation <6 hours after initiation of clinical signs, no medications or history of illness within the prior 2 weeks, lack of comorbidities expected to affect hemostasis, and lack of a disease state that could alternatively explain the clinical presentation.Interventions
Blood samples were collected within the first hour of presentation for CBC, serum biochemistry, prothrombin time (PT), activated partial thromboplastin time (aPTT), and viscoelastic coagulation testing for use with a cartridge-based point-of-care device.Measurements and main results
Clotting time and clot formation time were prolonged, alpha angle and maximum clot firmness were decreased, PT and aPTT were prolonged, and platelet counts were lower in severe cases compared to mild and moderate cases. There were no differences for any parameter between mild and moderate cases. The presence or absence of abdominal effusion was not associated with hemostatic status.Conclusions
Global hemostatic derangements consistent with hypocoagulability are a prominent feature of severe anaphylaxis in dogs and should be considered for routine evaluation. 相似文献113.
114.
115.
116.
117.
Goyette Jean-Olivier Cimon-Morin Jérôme Mendes Poliana Thériault Maxime Pellerin Stéphanie Poulin Monique 《Landscape Ecology》2021,36(9):2691-2706
Landscape Ecology - Human activities have led to the degradation of wetlands, impinging on their capacity to deliver essential ecosystem services to society. Wetland restoration now appears an... 相似文献
118.
Stergiadis S Leifert C Seal CJ Eyre MD Nielsen JH Larsen MK Slots T Steinshamn H Butler G 《Journal of agricultural and food chemistry》2012,60(29):7270-7281
There is increasing concern that the intensification of dairy production reduces the concentrations of nutritionally desirable compounds in milk. This study therefore compared important quality parameters (protein and fatty acid profiles; α-tocopherol and carotenoid concentrations) in milk from four dairy systems with contrasting production intensities (in terms of feeding regimens and milking systems). The concentrations of several nutritionally desirable compounds (β-lactoglobulin, omega-3 fatty acids, omega-3/omega-6 ratio, conjugated linoleic acid c9t11, and/or carotenoids) decreased with increasing feeding intensity (organic outdoor ≥ conventional outdoor ≥ conventional indoors). Milking system intensification (use of robotic milking parlors) had a more limited effect on milk composition, but increased mastitis incidence. Multivariate analyses indicated that differences in milk quality were mainly linked to contrasting feeding regimens and that milking system and breed choice also contributed to differences in milk composition between production systems. 相似文献
119.
Inge Håkansson Tomas Rydberg Thomas Keller 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(8):701-710
Abstract Extensive experiments were carried out in shallow plastic boxes placed directly on the ground in the field to study the effects of seedbed properties on the emergence of various crops in a cool temperate climate. In a group of experiments with barley (Hordeum vulgare L.), we studied the effects on crop emergence of firming (slight compaction) of the seedbed, simulating the recompacting effects of rolling after sowing or press wheels on the seed coulters. Most of the experiments were carried out without irrigation after sowing. The firming usually had a slightly positive effect on emergence when the water content in the surface layer at sowing was below the wilting point. When the water content in the surface layer was higher, firming often reduced emergence drastically, particularly with deep sowing and in coarse-textured soils. The main reason for negative effects was harmful hardening of the surface layer when the more firm seedbed gradually dried out. When irrigation kept the seedbed continuously moist, the negative effect of firming was almost eliminated. Very high initial water content in the basal layer tended to delay surface layer drying and hardening, and to reduce the negative effect of firming. Firming only slightly influenced the evaporative water losses from the soil. In contrast to the results presented here, previous field trials with cereals have usually resulted in more positive effects of rolling after sowing. This indicates that other effects than firming, such as modification of sowing depth and reshaping of the soil surface, are other important effects of rolling. 相似文献
120.
Agronomic traits of soybean cultivars released in different decades after grafting record‐yield cultivar as rootstock
下载免费PDF全文
![点击此处可从《Plant Breeding》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shengyou Li Fei Teng Demin Rao Xingdong Yao Huijun Zhang Haiying Wang Shuhong Song Steven K. St. Martin Futi Xie 《Plant Breeding》2017,136(2):133-138
Breeders have seldom considered the selection for root traits during the genetic improvement in soybean. It is hypothesized that grain yield would be increased by the root function improvement, especially for the current cultivars. The objective of this grafting experiment was to determine the effect of record‐yield cultivars L14 or Z35 as rootstocks on agronomic traits of cultivars released in different decades. A total of 11 cultivars, released in different decades, were used to graft onto L14 or Z35 rootstocks. The agronomic traits were measured in the pot‐culture experiments. Grafting cultivars released in different decades onto L14 or Z35 rootstocks resulted in higher yield, 100‐seed mass and apparent harvest index as compared with those of non‐grafted or self‐grafted plants. Grain yield gain of cultivars grafted onto record‐yield cultivar rootstocks was 0.40 g/plant/year from 1966 to 2006, which was larger than that of non‐grafts and self‐grafts (0.27 g/plant/year). The yield of current cultivars should increase more if their root functions were improved. 相似文献