全文获取类型
| 收费全文 | 516篇 |
| 免费 | 18篇 |
| 国内免费 | 1篇 |
专业分类
| 林业 | 28篇 |
| 农学 | 21篇 |
| 73篇 | |
| 综合类 | 72篇 |
| 农作物 | 13篇 |
| 水产渔业 | 18篇 |
| 畜牧兽医 | 274篇 |
| 园艺 | 8篇 |
| 植物保护 | 28篇 |
出版年
| 2021年 | 9篇 |
| 2020年 | 11篇 |
| 2019年 | 10篇 |
| 2018年 | 5篇 |
| 2017年 | 14篇 |
| 2016年 | 10篇 |
| 2014年 | 7篇 |
| 2013年 | 15篇 |
| 2012年 | 25篇 |
| 2011年 | 34篇 |
| 2010年 | 11篇 |
| 2009年 | 14篇 |
| 2008年 | 25篇 |
| 2007年 | 29篇 |
| 2006年 | 20篇 |
| 2005年 | 27篇 |
| 2004年 | 19篇 |
| 2003年 | 15篇 |
| 2002年 | 16篇 |
| 2001年 | 6篇 |
| 2000年 | 11篇 |
| 1999年 | 15篇 |
| 1998年 | 6篇 |
| 1997年 | 4篇 |
| 1996年 | 4篇 |
| 1993年 | 4篇 |
| 1992年 | 12篇 |
| 1991年 | 6篇 |
| 1990年 | 13篇 |
| 1989年 | 9篇 |
| 1988年 | 12篇 |
| 1987年 | 3篇 |
| 1986年 | 8篇 |
| 1985年 | 11篇 |
| 1984年 | 3篇 |
| 1983年 | 3篇 |
| 1982年 | 6篇 |
| 1981年 | 3篇 |
| 1980年 | 3篇 |
| 1979年 | 4篇 |
| 1978年 | 8篇 |
| 1977年 | 6篇 |
| 1974年 | 7篇 |
| 1973年 | 3篇 |
| 1972年 | 3篇 |
| 1970年 | 3篇 |
| 1969年 | 7篇 |
| 1968年 | 7篇 |
| 1967年 | 3篇 |
| 1966年 | 3篇 |
排序方式： 共有535条查询结果，搜索用时 593 毫秒
1.
K A Hahn D W Knapp R C Richardson C L Matlock 《Journal of the American Veterinary Medical Association》1992,200(3):355-357
In 11 dogs with nasal adenocarcinoma, IV treatment with 2 to 8 cycles of cisplatin at a dosage of 60 mg/m2 of body surface, given at 3-week intervals, resulted in a survival time of 8 to 128 weeks (mean, 32.7 weeks; median, 20 weeks). Radiography revealed complete remission in 2 dogs and partial remission in 1 dog, for an overall response rate of 27%. Clinical problems such as nasal discharge (n = 11), sneezing (n = 6), and epistaxis (n = 4) resolved in 1 to 2 weeks in all dogs after beginning chemotherapy. 相似文献
2.
J Hahn 《DTW. Deutsche tier?rztliche Wochenschrift》1989,96(2):72-73
New biotechnical methods in reproduction have been introduced in animal breeding via embryo transfer. There are no serious objections against these methods as long as the variety of species is reassured and the animal protection law is considered. More substantial objections exist against genetic engineering methods which alter the genome of animals. Beside for legal protection there is a strong public demand for the adequete awareness and responsibility of scientists who are active in this field. Comprehensive information on such research projects can lead to a better understanding of the aims and methods and might, therefore, help to reduce inadequate apprehensions. 相似文献
3.
4.
5.
6.
7.
Pablo M. Vergara Luis O. Meneses Audrey A. Grez Madelaine S. Quiroz Gerardo E. Soto Christian G. Pérez-Hernández Paola A. Diaz Ingo J. Hahn Andrés Fierro 《Landscape Ecology》2017,32(2):279-293
Context
Interactions between landscape-scale processes and fine-grained habitat heterogeneity are usually invoked to explain species occupancy in fragmented landscapes. In variegated landscapes, however, organisms face continuous variation in micro-habitat features, which makes necessary to consider ecologically meaningful estimates of habitat quality at different spatial scales.Objectives
We evaluated the spatial scales at which forest cover and tree quality make the greatest contribution to the occupancy of the long-horned beetle Microplophorus magellanicus (Coleoptera: Cerambycidae) in a variegated forest landscape.Methods
We used averaged data of tree quality (as derived from remote sensing estimates of the decay stage of single trees) and spatially independent pheromone-baited traps to model the occurrence probability as a function of multiple cross-scale combinations between forest cover and tree quality (with scales ranging between 50 and 400 m).Results
Model support and performance increased monotonically with the increasing scale at which tree quality was measured. Forest cover was not significant, and did not exhibit scale-specific effects on the occurrence probability of M. magellanicus. The interactive effect between tree quality and forest cover was stronger than the independent (additive) effects of tree quality and particularly forest cover. Significant interactions included tree quality measured at spatial scales ≥200 m, but cross-scale interactions occurred only in four of the seven best-supported models.Conclusions
M. magellanicus respond to the high-quality trees available in the landscape rather than to the amount of forest per se. Conservation of viable metapopulations of M. magellanicus should consider the quality of trees at spatial scales >200 m.8.
9.
Azin Rekowski Monika A. Wimmer Bernd Hitzmann Bernhard Hermannseder Heike Hahn Christian Zrb 《植物养料与土壤学杂志》2020,183(2):260-270
Background: Nitrogen losses is an economic problem for wheat production and a high risk to the environment. Therefore, improved N fertilizer management is a key to increasing the N efficiency and minimizing N losses. To increase N efficiency, enhanced fertilizers such as urea combined with urease inhibitor can be used. Aims: The aim of present study was to evaluate the effects of different N forms on grain storage protein subunits in winter wheat and to examine whether the observed changes correlate with parameters of baking quality. Methods: The investigation was performed over two consecutive years at two locations in Germany. Protein subunits were analyzed by SDS‐PAGE. Results: Protein concentrations were similarly increased after fertilization with ammonium nitrate and urea + urease inhibitor. Analysis of the individual storage protein fractions indicated that both fertilizers specifically enhanced ω‐gliadins and HMW glutenins, but the effect was more pronounced in the ammonium nitrate treatment. Application of urea + urease inhibitor had greater influence on the protein composition and resulted in higher specific baking volume as well as the best fresh keeping ability, in comparison with urea treatment. Conclusion: Considering that the urea + urease inhibitor treatment resulted in almost comparable improvements of NUE and baking quality, with the additional benefit of reduced N losses in combination with easy handling, urea + urease inhibitor can be recommended as a viable alternative to both urea alone and ammonium nitrate treatments. This opens up an opportunity for the reduction of N loss in wheat production when use of urea is preferred. 相似文献
10.
Revisiting the Roles of the University in Regional Economic Development: A Triangulation of Data 
下载免费PDF全文
下载免费PDF全文 Heike Mayer 《Growth and change》2017,48(4):787-804
There is a general understanding that university plays a crucial role in regional development under the current age of knowledge economy. At the same time, we have observed a fair number of counter‐evidentiary studies, demonstrating several regions that do not thrive despite strong research universities or other patterns of development in the absence of research universities. However, they are based on case studies of individual universities or regions, and the findings currently cannot be generalized. Another set of studies that have challenged the effect of universities at the nationwide scale and demonstrated its disproportionately small impact of universities, but their scope is limited to spin‐offs, patents, and license activities. In this article, we propose to investigate this subject more systematically by triangulating three methods: 1) national‐scale regression models with Business Dynamics Statistics and National Establishment Time Series data, 2) a regional survey of IT and life science firms in four so‐called “second tier regions,” and 3) a microeconomic firm‐level analysis based on interviews with founders of technology intensive firms. Furthermore, we test the roles of university beyond those explicit, direct measures of spin‐offs and patents by analyzing the firm formation rate and firm growth rate at the regional level, as well as the sources of growth at the company level. All results point in the same direction: The research function of the university has been overstated, and the teaching function of the university has been underappreciated. These findings provide profound implications for the policy of regional development. 相似文献