全文获取类型
收费全文 | 58253篇 |
免费 | 3332篇 |
国内免费 | 37篇 |
专业分类
林业 | 3043篇 |
农学 | 2211篇 |
基础科学 | 351篇 |
7220篇 | |
综合类 | 6763篇 |
农作物 | 2070篇 |
水产渔业 | 3170篇 |
畜牧兽医 | 32833篇 |
园艺 | 723篇 |
植物保护 | 3238篇 |
出版年
2019年 | 495篇 |
2018年 | 957篇 |
2017年 | 1036篇 |
2016年 | 1007篇 |
2015年 | 865篇 |
2014年 | 1011篇 |
2013年 | 2320篇 |
2012年 | 1808篇 |
2011年 | 2199篇 |
2010年 | 1437篇 |
2009年 | 1368篇 |
2008年 | 2033篇 |
2007年 | 2041篇 |
2006年 | 1934篇 |
2005年 | 1789篇 |
2004年 | 1682篇 |
2003年 | 1667篇 |
2002年 | 1510篇 |
2001年 | 2290篇 |
2000年 | 2146篇 |
1999年 | 1670篇 |
1998年 | 645篇 |
1997年 | 579篇 |
1996年 | 587篇 |
1995年 | 669篇 |
1994年 | 571篇 |
1993年 | 554篇 |
1992年 | 1261篇 |
1991年 | 1397篇 |
1990年 | 1448篇 |
1989年 | 1328篇 |
1988年 | 1243篇 |
1987年 | 1230篇 |
1986年 | 1167篇 |
1985年 | 1104篇 |
1984年 | 917篇 |
1983年 | 723篇 |
1982年 | 524篇 |
1979年 | 792篇 |
1978年 | 616篇 |
1977年 | 469篇 |
1976年 | 524篇 |
1975年 | 502篇 |
1974年 | 624篇 |
1973年 | 606篇 |
1972年 | 633篇 |
1971年 | 601篇 |
1970年 | 588篇 |
1969年 | 537篇 |
1967年 | 497篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Peter Kaloki Richard Trethowan Daniel K. Y. Tan 《Journal of Agronomy and Crop Science》2019,205(5):470-476
Chickpea is a major crop grown for its nutritional value, and it is used for both food and feed. However, terminal drought greatly reduces grain yield in many chickpea producing areas. The impacts of drought could be mitigated by adapting chickpea genotypes with higher water‐use efficiency (WUE). To assess genetic variation for WUE, contrasting genotypes were sown in two moisture regimes (well‐watered and water‐limited) and two tillage regimes (tillage and no‐tillage) in north‐western NSW across two consecutive seasons. The well‐watered and no till treatments were higher yielding than their respective rainfed and tillage treatments. Genotypes did not differ (p < 0.05) in their water use but differed significantly in their WUE, and a significant genotype‐by‐moisture treatment effect was observed. The heritability of WUE was higher under tillage (71.3% for tillage under rainfed conditions and 73.0% for tillage and irrigated conditions) than no‐till (43.3% for no till under rainfed conditions and 36.4% for no‐till and irrigated conditions), and no significant genotype‐by‐tillage interaction was observed. 相似文献
52.
Barrera-Reyes Paloma K de Lara Josué Cortés-Fernández González-Soto Melissa Tejero M Elizabeth 《Plant foods for human nutrition (Dordrecht, Netherlands)》2020,75(1):1-11
Plant Foods for Human Nutrition - The effects of cocoa-derived polyphenols on cognitive functions have been analyzed through numerous studies using different interventions (doses, vehicles, time... 相似文献
53.
This article describes the management of a complicated distal epiphyseal Salter–Harris type I fracture of the left tibia in a yearling horse. Closed reduction and internal fixation was attempted in the first surgery using tension band wires. Due to fracture instability 2 weeks after surgery, a full-limb transfixation pin cast was applied to the tibia and maintained for 7 weeks to prevent further fracture displacement and to achieve axial alignment. The full-limb cast was maintained for a total of 12 weeks, including the time with the transfixation pin cast. Cast sores and tendon laxity resolved without further complications. Ten months after the first surgery, the fracture had radiographically healed, and the horse was sound at the walk and trot in a straight line. 相似文献
54.
Waseem Akbar Anilkumar Gowda Jeffrey E Ahrens Jason W Stelzer Robert S Brown Scott L Bollman John T Greenplate Jeffrey Gore Angus L Catchot Gus Lorenz Scott D Stewart David L Kerns Jeremy K Greene Michael D Toews David A Herbert Dominic D Reisig Gregory A Sword Peter C Ellsworth Larry D Godfrey Thomas L Clark 《Pest management science》2019,75(3):867-877
55.
56.
D Loddo D Bozic I M Calha J Dorado J Izquierdo M epanovi K Bari S Carlesi R Leskovsek D Peterson V P Vasileiadis A Veres S Vrbni
anin R Masin 《Weed Research》2019,59(1):15-27
Abutilon theophrasti is a weed that is spreading worldwide and that has had to adapt to different combinations of environmental conditions. Wide interpopulation variability has been reported regarding dormancy and germination. This variability, controlled by the interaction of genetic diversity and maternal effect, could hinder the adoption of Integrated Weed Management (IWM) tools. A collaborative project was conducted to compare emergence dynamics of 12 European and North American populations under diverse environmental conditions. The main aim was to assess interpopulation variability and explain this according to environmental conditions in the seed collection sites. Seeds were sown at six experimental sites, and seedling emergence was monitored. The AlertInf model was tested to evaluate its ability to predict emergence dynamics of the different populations. A wide interpopulation variability was observed for emergence percentage and dynamics with consistent trends across sites and related to different seed dormancy levels. Populations from Catalonia, Iowa and Minnesota reached higher emergence percentage with earlier and concentrated emergence flushes probably due to low dormancy level, while populations from Croatia, Serbia and Hungary, given their low average emergence percentage, presented high dormancy levels. Good predictive accuracy of AlertInf model was obtained at the different sites, confirming the possibility of adopting it across a wide range of environmental conditions. Achieving a better knowledge of interpopulation variability can allow specific control strategies to be designed, facilitating the replacement of solely herbicide‐based management with true IWM. 相似文献
57.
Chettry Upasna Chrungoo Nikhil K. 《Plant foods for human nutrition (Dordrecht, Netherlands)》2021,76(4):399-409
Plant Foods for Human Nutrition - While intensification of farming systems is essential for achieving the Millennium Development Goal of “Zero hunger”, issues such as availability of... 相似文献
58.
Andr Z. Boaratti Thiago M. T. Nascimento Kifayat U. Khan Cleber F. M. Mansano Thaís S. Oliveira Daniel M. A. Queiroz Rafael S. Romaneli Andressa T. Rodrigues Nilva K. Sakomura Joo B. K. Fernandes 《Journal of the World Aquaculture Society》2021,52(1):88-104
The present study aimed to determine the ideal ratios of digestible essential amino acids (EAAs) for pacu (Piaractus mesopotamicus) juveniles by the amino acid (AA) deletion method. A completely randomized design which consisted of 11 treatments and three replicates each was used. The treatments included a control diet (CD) containing 55% of nonpurified natural ingredients and 45% of purified synthetic amino acids and ingredients, and other ten isonitrogenous and isoenergetic EAA limiting diets (LDs), each being deficient in 44.4 ± 0.02% of the respective EAA. Pacu juveniles with initial average body weight of 6.22 ± 0.09 g were distributed among 33 fiber glass tanks. Fish were fed with semipurified and extruded diets for 113 days two times a day until apparent satiation. The ideal ratio of each dietary EAA was calculated on the basis of the relationship between body N retention and amount of EAA deleted from the respective EAA LD. Based on the AA deletion method, the ideal ratios of digestible EAAs for pacu juveniles, relative to lysine requirement of 100% were estimated as: methionine 14.6%, threonine 35.0%, tryptophan 6.6%, arginine 62.8%, histidine 13.6%, isoleucine 26.3%, leucine 43.7%, phenylalanine 27.2%, and valine 35.8%. 相似文献
59.
Feeding ragworm (Nereis virens Sars) to common sole (Solea solea L.) alleviates nutritional anaemia and stimulates growth 下载免费PDF全文
Jeroen Kals Robbert J W Blonk Arjan P Palstra Tim K Sobotta Fulvio Mongile Oliver Schneider Josep V Planas Johan W Schrama Johan A J Verreth 《Aquaculture Research》2017,48(3):752-759
Common sole fed with commercial pellets develop anaemia and are restricted in their growth performance. The anaemia can be the result of a difference in feed intake, a nutritional deficiency, an inflammatory response to infection or combinations of these aspects. In this study, it was investigated whether feeding ragworm would alleviate the anaemia and stimulate growth. Sole were fed one of three diets: a commercial feed, a commercial feed treated with ragworm extract or chopped ragworm. By comparing groups, three hypotheses were tested: (1) feeding ragworm alleviates the anaemia and positively affectS the sole's metabolic performance reflected in feed intake, feed efficiency and growth; (2) anaemia is alleviated by a higher feed intake when feeding ragworm and (3) anaemia is caused by an inflammatory response to infection. The sole fed with a commercial diet suffered from anaemia. Feeding sole with ragworm alleviated the anaemia as the average haematocrit level nearly doubled in these fish as compared to fish fed pellets. Investigation of the expression of genes in the liver indicated that the anaemia in sole fed pellets is a nutritional anaemia and not an anaemia due to an inflammatory response. Sole fed ragworm showed improved growth which may be a consequence of the higher haematocrit levels in these fish increasing their oxygen carrying capacity. Addition of ragworm extract to the pellets levelled the feed intake between pellets and ragworm, but did not improve the anaemic state of sole and had only a limited effect on growth. 相似文献
60.
Exploring tropical fisheries through fishers’ perceptions: Fishing down the food web in the Tonlé Sap,Cambodia 下载免费PDF全文
K. B. KC N. Bond E. D. G. Fraser V. Elliott T. Farrell K. McCann N. Rooney C. Bieg 《Fisheries Management and Ecology》2017,24(6):452-459
Tropical fisheries are among the most productive fisheries in the world, often providing the primary source of protein for the local population. Despite their importance, data on these systems are relatively limited, thus hampering management and policy development. Here, the implications of increasing fishing pressure are explored by critically evaluating the perceptions of the fishers who rely on these ecosystems to survive. A total of 169 fishers in 26 different fish‐dependent communities in the Tonlé Sap Lake, Cambodia, were surveyed to understand their perceptions of the impact that fishing has had on the ecosystem. The Tonlé Sap is one of the largest, yet poorest studied, freshwater fisheries in the world. Consistent with “fishing down the food web” theory of fisheries, survey data revealed that although fishers observed the total size of fish catch remaining consistent over recent years there has been a drastic decline in the size of individual fish, as well as a reduction in the diversity of species caught. These perceptions are examined with reference to food web theories that explore how fishing pressure leads to ecosystem change, including the more recent “indiscriminate fisheries” theory. 相似文献