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81.
W. Wolters Nadi Selim Ghobrial H. M. Van Leeuwen M. G. Bos 《Irrigation and Drainage Systems》1989,3(2):103-123
A study of the water balances of The Fayoum irrigated lands and Lake Qarun was made to investigate the management of the irrigation
system and the efficiency of irrigation water use. The two water balances are strongly interrelated. The drainage flow to
Lake Qarun and the water level of the Lake are in delicate balance. A rise in Lake level causes the inundation of adjacent
land. Management of The Fayoum water balance assumes control over irrigation water flows, but this control has technical and
organizational limitations.
Also discussed is the influence of irrigation practices in The Fayoum on the water balance (e.g., the autumn flushing of fields
and farmers' preference for not irrigating at night in winter).
Notwithstanding a high overall efficiency, irrigation efficiency during the winter is low. The reasons for this are given,
together with the constraints against improving system management.
Improved uniformity of the division and application of irrigation water will enable a better technical control of flows and
will result in better water management in The Fayoum.
Abbreviations: FID — Fayoum Irrigation Department, 1 feddan (fe) — 0.4 ha, 1 mcm — 1 million cubic metres: an average annual flow of 3.17
m3/s gives 100 mcm, m3/fe.year — supplied volume (m3) per surface area (fe) per year: 1000 m3/fe.year equals 240 mm/year, MSL — Mean Sea Level 相似文献
82.
Summary As hardly any data can be found on the water requirement and yield response to water of Aloe vera, an irrigation experiment on transplanted aloe poles was conducted on the Caribbean island of Aruba. Compared to non-irrigated treatments irrigation shows a positive influence on growth, number of developed leaves, raw gel figure and gel production per plant. The amount of irrigation water to apply can be best calculated based on crop coefficients (Kc) between 0.20 and 0.30. Treatment based on a Kc value higher than 0.30 did not further increase production. A lysimeter study conducted over a relatively short period revealed that the crop coefficient for Aloe vera varied between 0.25 and 0.40 which is characteristic of the so-called agave/pineapple group. 相似文献
83.
This work describes the analysis of the uncertainty linked to the annual direct and indirect losses of different nitrogenous compounds at the scale of a group of farms. The nitrogen (N) forms taken into account are: ammonia (NH3), nitric oxide (NO), nitrous oxide (N2O), dinitrogen (N2) and nitrate (NO3). The gaseous N emissions for the different components of the farms are estimated with a selection of adapted emission factors. The NO3 losses at the farm scale are calculated as the difference between the surplus of the farm-gate N balance and the gaseous N emissions. 相似文献
84.
B. Sterk M.K. van Ittersum C. Leeuwis W.A.H. Rossing H. van Keulen G.W.J. van de Ven 《Agricultural Systems》2006
Whole-farm design models quantitatively analyze the effects of a variety of potential changes at the farm system level. Science-driven technical information is confronted with value-driven objectives of farmers or other social groupings under explicit assumptions with respect to exogenous variables that are important drivers of agricultural systems (e.g., market conditions). Hence, farm design is an outcome of objective specification and the potential of a system. In recent publications, whole-farm design modelling has been proposed to enhance (farm) innovation processes. A number of operational modelling tools now offers the opportunity to assess the true potential of whole-farm design modelling to enhance innovation. In this paper, we demonstrate that it is not trivial to find niches for the application of goal-based farm models. Model outcomes appeared not to match questions of farm managers monitoring and learning from their own and other farmers’ practices. However, our research indicates that whole-farm design modelling possesses the capabilities to make a valuable contribution to reframing. Reframing is the phenomenon that people feel an urge to discuss and reconsider current objectives and perspectives on a problem. Reframing might take place in a situation (i) of mutually felt dependency between stakeholders, (ii) in which there is sufficient pressure and urgency for stakeholders to explore new problem definitions and make progress. Furthermore, our research suggests that the way the researcher enters a likely niche to introduce a model and/or his or her position in this niche may have significant implications for the potential of models to enhance an innovation process. Therefore, we hypothesize that the chances of capitalizing on modelling expertise are likely to be higher when researchers with such expertise are a logical and more or less permanent component of ongoing trajectories than when these researchers come from outside to purposefully search for a niche. 相似文献
85.
Robert M. REES Juliette MAIRE Anna FLORENCE Nicholas COWAN Ute SKIBA Tony van der WEERDEN Xiaotang JU 《农业科学与工程前沿(英文版)》2020,7(1):75-80
Nitrous oxide (N2O) emissions make up a significant part of agricultural greenhouse gas emissions. There is an urgent need to identify new approaches to the mitigation of these emissions with emerging technology. In this short review four approaches to precision managements of agricultural systems are described based on examples of work being undertaken in the UK and New Zealand. They offer the opportunity for N2O mitigation without any reduction in productivity. These approaches depend upon new sensor technology, modeling and spatial information with which to make management decisions and interventions that can both improve agricultural productivity and environmental protection. 相似文献
86.
87.
88.
Seyedeh Masoumeh Fotoukkiaii Zoë Tan Wenxin Xue Nicky Wybouw Thomas Van Leeuwen 《Pest management science》2020,76(3):1154-1163
89.
90.
Aartsma Yavanna Hao Yueyi Dicke Marcel van der Werf Wopke Poelman Erik H. Bianchi Felix J. J. A. 《Landscape Ecology》2020,35(4):907-919
Landscape Ecology - Tritrophic interactions may be affected by local factors and the broader landscape context. At small spatial scales, carnivorous enemies of herbivorous insects use... 相似文献