全文获取类型
收费全文 | 17976篇 |
免费 | 1053篇 |
国内免费 | 676篇 |
专业分类
林业 | 4148篇 |
农学 | 594篇 |
基础科学 | 1290篇 |
2326篇 | |
综合类 | 6746篇 |
农作物 | 683篇 |
水产渔业 | 1052篇 |
畜牧兽医 | 1264篇 |
园艺 | 317篇 |
植物保护 | 1285篇 |
出版年
2024年 | 94篇 |
2023年 | 301篇 |
2022年 | 340篇 |
2021年 | 501篇 |
2020年 | 567篇 |
2019年 | 652篇 |
2018年 | 429篇 |
2017年 | 521篇 |
2016年 | 664篇 |
2015年 | 560篇 |
2014年 | 972篇 |
2013年 | 1151篇 |
2012年 | 1480篇 |
2011年 | 1476篇 |
2010年 | 1116篇 |
2009年 | 1190篇 |
2008年 | 1082篇 |
2007年 | 1112篇 |
2006年 | 917篇 |
2005年 | 892篇 |
2004年 | 696篇 |
2003年 | 595篇 |
2002年 | 434篇 |
2001年 | 410篇 |
2000年 | 337篇 |
1999年 | 232篇 |
1998年 | 176篇 |
1997年 | 164篇 |
1996年 | 135篇 |
1995年 | 107篇 |
1994年 | 77篇 |
1993年 | 62篇 |
1992年 | 66篇 |
1991年 | 63篇 |
1990年 | 35篇 |
1989年 | 46篇 |
1988年 | 31篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1985年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
2004年8月,江西省开始启动林业产权制度改革,用近一年的时间基本完成了试点工作,目前改革工作已在全省全面铺开.通过林改,明晰林业产权,减免税费,逐渐放活经营,规范流转,林业生产关系更加适应社会主义市场经济发展需要,提高了木材生产收益、群众造林护林积极性及山地租赁价格.但是,在新的林业生产关系下,许多配套管理措施还没有完善,森林保护管理工作出现一些新情况新问题不可避免.为保护好、管理好森林资源,需要对这些新变化、新情况、新问题进行研究,找出规范管理的新途径. 相似文献
32.
王永生 《金陵科技学院学报》1996,(2)
养好肉仔鸡的关键是选择质量可靠的品种苗雏,喂以全价营养饲料,特别要加强雏鸡阶段的饲养管理,如温度、饮水等,按照科学的免疫程序进行免疫,做好肉仔鸡常见病的防制。 相似文献
33.
对家蚕育种亲本及其新品种性状数据档案实行信息化管理,可在家蚕育种和品种的种性维持过程中自动实现完整的信息采集、计算、调用、选择等功能。开发了一个基于B/S结构的家蚕育种与种性维持信息管理系统,主要包括品种管理、计划任务管理、饲育信息管理、蚕茧信息管理、选种信息管理、选优信息管理等功能模块。选种信息管理模块的运行过程是通过电子天平称量蚕茧质量,然后根据计算模型自动进行数据信息处理与统计分析实施选择。用户可以方便地通过网络访问该系统,实现家蚕新品种选育及种性维持工作的自动化。 相似文献
34.
35.
《Veterinary anaesthesia and analgesia》2023,50(5):446-458
ObjectiveBedinvetmab, a fully canine anti-nerve growth factor monoclonal antibody, was evaluated in dogs for control of osteoarthritis-related pain in a study conducted to support registration in the USA.Study designRandomized, double-blind, placebo-controlled, multicenter, parallel-group study.AnimalsGeneral practice client-owned dogs with osteoarthritis (n = 272).MethodsDogs were block randomized 1:1 to placebo (saline, n = 137) or bedinvetmab (n = 135; 0.5–1.0 mg kg–1) administered subcutaneously, once monthly. The primary end point, day 28 Canine Brief Pain Inventory (CBPI) treatment success (TS), required pain severity score (PSS; 0–10) decrease ≥1 and pain interference score (PIS; 0–10) decrease ≥ 2. CBPI TS rates [and number needed to treat (NNT)], change in scores [and standardized effect size (ES)], change in quality of life (QoL) and bedinvetmab half-life were calculated.ResultsSignificant (p < 0.05) improvement with bedinvetmab over placebo occurred (days 28, 42, 56, 84) for CBPI TS. Of cases evaluable for day 28 CBPI TS (placebo, n = 131; bedinvetmab, n = 128), success rates were 36.6% and 47.4%, respectively (p = 0.0410) (NNT, 9.3; PSS and PIS ES, 0.3). CBPI TS increased after the second dose in both groups, plateaued for bedinvetmab at day 42 and decreased for placebo beginning day 84. Day 84 NNT (4.3), PSS (0.4) and PIS (0.5) showed continued improvement with monthly dosing. After the first dose, mean (± standard deviation) bedinvetmab half-life was 19.1 (8.3) days. Adverse events were similar between groups and not considered treatment-related. There was a significant effect of bedinvetmab versus placebo on all CBPI components (PIS, PSS, QoL).Conclusions and clinical relevanceThese results corroborated those previously reported and provide further support of safety and effectiveness of bedinvetmab (0.5–1.0 mg kg–1) administered subcutaneously at monthly intervals to dogs for control of osteoarthritis-related pain. 相似文献
36.
马是一种独特的家畜,主要用途是娱乐或工作。长期以来,马的营养一直集中在提供足够数量和类型的营养素,以达到最大的运动状态。营养学家的目标是最大限度地发挥营养对运动的影响,因此,本文综述了关于赛马主要营养素的需求特点,为竞技赛马的饲养提供依据。 相似文献
37.
Masahiro Osada Hitomi Iwabuchi Toru Aoki Kika Sasaki Hitoshi Ushijima Takeyuki Ozawa 《Animal Science Journal》2019,90(4):597-603
Artificial insemination using sex‐sorted semen is employed to efficiently increase the number of female dairy calves born. Previous studies have determined that using sex‐sorted semen is beneficial to improve the management, but the mechanism by which it increases cattle numbers through objective indices of breeding remains unclear. This study focused on a Brown Swiss cattle herd in which frozen female sex‐sorted semen was systematically employed to increase the number of cattle. We analyzed the correlation between the increase in the number of cattle and the screening accuracy of sex‐sorted semen, measuring indices such as pregnancy rate and birth rate of female calves. Study revealed that: (1) production cost for female calves is influenced by the pregnancy rate, rate of female calves, and using sex‐sorted semen is less expensive than using nonsorted semen; (2) improvements in screening accuracy nearly doubled the number of cows and tripled the number of heifers in 5 years; and (3) use of sex‐sorted semen improved milk quality. The pregnancy rate was lower when sex‐sorted semen was used, but the birth rate of heifers was improved. Results suggest that artificial insemination using sex‐sorted semen is beneficial because it economically produces offspring to increase the herd. 相似文献
38.
39.
开展生物多样性动态长期监测,了解生态系统结构与功能变化,探明生物多样性变化过程及影响因素是制定有效保护措施的重要基础。本研究在内蒙古赛罕乌拉国家级自然保护区开展10年野生动物多样性动态监测,新发现保护区分布哺乳动物7种、鸟类98种,内蒙古鸟类新纪录2种,内蒙古蛇类新纪录1种。但也未发现一些以往有记录的物种,需要进一步强化野生动物多样性监测,探明物种变化的原因。后续监测工作引入了非损伤采集动物粪样提取DNA技术,从而深入了解保护区野生动物种群长期稳定的遗传学和空间分布特征,为有效管理自然保护区珍稀野生动物提供科技支撑。 相似文献
40.
- 1. Wetlands are declining worldwide, and there is a great need for their restoration and creation. One natural agent of wetland engineering is beavers, Castor spp., which have returned or are returning to many parts of their former range.
- 2. We initially studied the facilitative effect of the beaver Castor canadensis on a waterbird community consisting of three waders and four ducks in boreal wetlands in southern Finland. Both waterbird species diversity and abundance increased when beavers impounded a pond. Common teal Anas crecca and green sandpiper Tringa ochropus were the species showing the most positive numerical response, but the other five species also increased upon flooding.
- 3. This article evaluates how the results of the study have been used in management, both in theory and practice. The whole‐community facilitation concept has been taken up in numerous articles considering the restorative effects of beavers. It has also been used as ecological background when planning and executing man‐made wetland projects in Finland within both the public and the private sectors.
- 4. Our study and its publication in Aquatic Conservation: Marine and Freshwater Ecosystems have set a foundation for further evidence‐based management of waterbird communities. As the results show, having beavers as wetland managers is a feasible tool for creating and restoring wetlands for waterbirds and other biota. Moreover, wetland restoration projects are becoming more popular endeavours, owing to an understanding of the diverse benefits of wetlands. Flooding by beavers is used as a model for managers when creating man‐made wetlands; for example, in urban areas where it is difficult to maintain beavers.