全文获取类型
收费全文 | 194篇 |
免费 | 8篇 |
国内免费 | 14篇 |
专业分类
林业 | 15篇 |
农学 | 10篇 |
基础科学 | 12篇 |
36篇 | |
综合类 | 39篇 |
农作物 | 13篇 |
水产渔业 | 2篇 |
畜牧兽医 | 79篇 |
园艺 | 5篇 |
植物保护 | 5篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 19篇 |
2010年 | 2篇 |
2009年 | 8篇 |
2008年 | 14篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 2篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有216条查询结果,搜索用时 187 毫秒
1.
2.
介绍了X射线分选的具体原理,指出了目前X射线分选存在的问题,综述了国内外报废汽车回收X射线分选的研究进展与相关设备应用现状,展望了X射线分选技术的发展趋势. 相似文献
3.
4.
澜沧江上游森林珍稀草本植物生态位研究 总被引:14,自引:1,他引:14
20 0 2年和 2 0 0 3年 7— 8月 ,笔者采用常规调查方法对三江源自然保护区内澜沧江上游物种进行了调查研究 .以不同群落类型和海拔高度作为资源位 ,分别以物种重要值和个体多度为生态位计测的状态指标 ,对澜沧江上游桃儿七、星叶草和角盘兰及选取的几种对照草本植物进行生态位的计测和分析 .结果表明 :桃儿七、星叶草、角盘兰生态位宽度值小 ,充分显示了它们的稀有性 ,在该地区应优先保护 .桃儿七种群在海拔 36 0 0~ 36 5 0m分布最多 ,并且种群数量随海拔高度的增加逐渐减少 ;星叶草种群在海拔 36 5 0~ 375 0m分布最多 ,但种群数量不随海拔高度变化呈现规律性变化 .草本植物物种的生态位相似性比例值大于 0 5的占 5 0 % ,桃儿七、星叶草、角盘兰的生态位相似性比例大 ,说明它们在该地区的生态位相似程度大 .草本植物的生态位重叠值较小 ,大于 0 0 1的占 2 1 4 3% .桃儿七、星叶草、角盘兰之间生态位重叠程度小 ,它们分布的群落类型相似程度小 . 相似文献
5.
为了探索柑橘小实蝇入侵扩散与危害规律,提高其监测与防控水平,2008—2010年应用柑橘小实蝇专用性诱剂和诱捕器,在全市19个镇(街道)35个柑橘园建立监测点进行全市性入侵扩散分布普查;在古城伏龙柑橘园和市区水果市场,建立2个系统监测点开展全年种群数量消长监测,结果表明柑橘小实蝇种群入侵扩散与时空分布呈塔型趋势,即以城区为中心,并呈向周边区域扩散蔓延趋势;全年种群时序数量变化主要呈单峰型曲线变化,一般于6月中下旬至7月上中旬初见性诱成虫,8月上旬形成增长拐点,9—10月形成数量高峰,影响种群数量消长的主要因子有种群基数、气候和生境条件等,从而创建柑橘小实蝇基数(m6)与全年种群诱量(M)关系模型M=23.8339m6+59.8003(n=6,r=0.9735**)、当旬虫口密度(mn)与其前3个月的旬平均气温(tn-9)关系模型mn=1.9248tn-9-14.88063(n=72,r=0.5123**),以及柑橘挂果期成虫诱量(M)、有虫株率(R%)、有虫果率(P%)、每虫果幼虫量(N)等关系模型:R=0.3667M-1.2746(n=11,r=0.8901**);P=0.0581R+0.3112(n=11... 相似文献
6.
以新品种‘隆丰黑李’闽东种植示范基地核心区为调查点,观测该病害在果园的发生区位情况,记录发病症状,分析各栽培管理措施及自然环境变化对病害发生产生的影响,并室内筛选了对该病害病原菌具抑制作用的杀菌剂.结果表明:以叶片病斑数及病斑面积占叶片面积百分比为依据划分的病情指数等级较为合理;该病在黑李园4月中下旬开始发病,平均发病率为26.04%,平均病情指数为9.62,主要危害叶片,亦可危害枝梢和果实;该病的发生与果园方位、果园管理及气侯条件存在一定的相关性,南面果园发病较重.在供测的5种杀菌剂中,6%春雷霉素和72%农用链霉素对该病病原菌的抑制效果最好,EC50分别为1.085 5 mg/mL和1.7799 mg/mL;联合毒力测定结果表明,72%农用链霉素和6%春雷霉素以6∶1和3∶1混配具增效作用,1:1配比具相加作用,1∶3和1∶6配比具拮抗作用. 相似文献
7.
Kaeoket K Persson E Dalin AM 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2003,50(4):169-178
This study investigates the distribution of leucocytes, CD2+, CD4+, CD8+ lymphocyte subpopulations and MHC class II expressing cells in the sow endometrium following post-ovulatory insemination in relation to clinical findings and pregnancy outcome. Crossbred multiparous sows were inseminated once either at 15-20 h after ovulation [experiment 1, slaughtered at 20-25 h (5-6 h after artificial insemination (AI), group 1-A, n = 4), at 70 h after ovulation (group 1-B, n = 4), on day 11 (group 1-C, n = 4, first day of standing oestrus = day 1) or on day 19 (group 1-D, n = 4)] or 30 h after ovulation [experiment 2, slaughtered at 5-6 h after AI (group 2-A, n = 4) or on day 19 (group 2-D, n = 3)]. The uterine horns were flushed to control for the presence of spermatozoa and neutrophils and/or for recovery of oocytes and/or embryos. Mesometrial uterine samples were plastic embedded and stained. Cryofixed uterine samples were analysed by immunohistochemistry using mAbs to lymphocyte subpopulations and MHC class II molecules. Light microscopy was used to examine surface (SE) and glandular epithelia (GE), and connective tissue layers, both subepithelially (SL) and glandular (GL). In experiment 1, group 1-A, only one sow had spermatozoa in the utero-tubal junction (UTJ). Marked/moderated numbers of neutrophils and spermatozoa were observed in the flushings of two sows. In group 1-B, altogether 23 of 48 oocytes were cleaved. Day 11 (1-C), embryos with small diameter were observed. Day 19 (1-D), no embryos were found but small pieces of foetal membrane were observed in one of the sows. In group 1-A, large numbers of neutrophils were found within the SE and SL but with high individual variation. For T lymphocyte subpopulations, in the SE, most CD2+ cells were found in group 1-A. For both SE and GE in all groups, the number of CD8+ cells was significantly larger than that of CD4+ cells. In experiment 2, group 2-A, no sow had spermatozoa in the UTJ or in the uterine flushings. At day 19, no sow was pregnant. In group 2-A, large numbers of neutrophils were found within the SE and SL but with high individual variation. At day 19, high E2 levels showed a hormonal prooestrous stage but the endometrial neutrophil infiltration normally expected at pro-oestrus was absent. In conclusion, post-ovulatory insemination (about 18 h after ovulation) resulted in impaired spermatozoa transport within the uterus and embryonic degeneration. In sows post-ovulatory inseminated at a later stage (30 h after ovulation), no sow was pregnant. In both experiments, disturbed immune cell patterns were observed in some individuals. 相似文献
8.
Dalin AM Andresen O Malmgren L 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2002,49(3):125-131
The aim of the present study was to investigate the effect of active immunization against GnRH in mature Standardbred mares (three experimental and one control mare) on antibody titres, ovarian function, hormonal levels and oestrous behaviour. The mares were individually teased with a stallion once each day. During the first part of the experiment (period I: late April until November), blood was sampled every third day during the first 3 months, thereafter once per week. In the second part of the experiment (period II: December until August), sampling was carried out every second week. Progesterone, oestradiol-17beta and LH were analysed. Rectal gynaecological examination was made with the same intervals as the blood samplings and included palpation of the genital organs and ultrasonography. The experimental mares were immunized against GnRH with a GnRH-BSA conjugate. Equimune (Vetrepharm, Bracetown, Business Park, Clonee, Co. Meath, Republic of Ireland) was used as adjuvant. The mares were immunized on four occasions (20-30 day intervals) and GnRH antibody titre was determined. All immunized mares produced antibodies against GnRH but the maximum titres as well as the duration of a greater than 10% binding capacity varied between the mares (1 : 1600 to 1 : 50 000; 5 to 12 months, respectively). After the first injection, all mares showed one oestrus and ovulated at the regular time. In two of the mares, the immunization resulted in ovarian atrophy. Their hormone levels of progesterone, oestradiol- 17beta and progesterone decreased to basal levels and the cyclical hormone pattern was interrupted from approximately 30 days onwards. They continued to show oestrous signs but with irregular durations and intervals. The third mare showed ovarian suppression only for short periods and not in both ovaries at the same time; the hormone levels were basal for only about 20 days (days 50-70) and the mare ovulated on day 75 after start of immunization. The other mares ovulated after 13.5 and 15 months, respectively. It is concluded that the effect of immunization against GnRH in mature mares was individual concerning antibody titre response and the suppression of ovarian activity and hormone levels. Mares with totally inactive ovaries continued to show oestrous signs but with irregular intervals and durations. 相似文献
9.
10.
After investigating and studying the vegetation, we have established that Makehe Forest, in Sanjiangyuan Nature Reserve, Qinghai
Province, is host to a total of 364 different species, representing 173 “genera” in 55 different vegetative families. We propose
five quantifiable indices for evaluating the level of threat to these plants: 1) the distribution frequency of the “line transect”;
2) the distribution frequency of sample plots; 3) the distribution density inside sample plots; 4) the existing abundance
in the forest region; and 5) plant fidelity. The results show that there are two endangered species, six vulnerable species,
12 nearly threatened species and 344 safe species. The study tried to evaluate the urgency for conserving these plants, according
to coefficients of closeness to disappearance, of genetic loss and of usefulness. Results also showed that the number of species
of primary concern is two; of secondary concern, nine; of the third level, 23; and of least concern, 330 species.
__________
Translated from Journal of Beijing Forestry University, 2006, 28(3): 20–25 [译自: 北京林业大学学报] 相似文献