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151.
152.
试验研究了热应激对肉鸡的影响以及电解质添加剂对肉鸡生产性能和屠体品质的影响。结果表明 ,(1 )热应激可显著降低肉仔鸡采食量、日增重和饲料利用率 ;(2 )与高温对照组相比 ,在日粮中添加抗热应激添加剂的 1 4~ 3 1日龄肉鸡 ,其平均日增重提高了 6.43 % (P<0 .0 5 ) ;3 8~ 46日龄肉鸡 ,平均日增重和饲料利用率分别提高了 2 7.5 4% (P<0 .0 5 )和 2 0 .1 9% (P<0 .0 5 ) ;但这种抗热应激添加剂对肉鸡采食量无显著效果。此外 ,热应激能显著地增加肉鸡腹脂率 ,而添加抗热应激添加剂能显著降低腹脂率。 相似文献
153.
154.
A methodology for ranking and classifying performance of irrigation systems through multidimensional performance indicators is developed using fuzzy set theory. The procedure uses the concepts of fuzzy resemblance and fuzzy dominance. Preference levels reflecting management priorities are incorporated into the analysis using appropriate weighting factors. The application of the procedure is demonstrated through two case studies: the Shi-Jin irrigation district in Hebei Province, China and the Goulburn irrigation region in Victoria, Australia. The classification of performance periods for the Australian system shows three clusters indicating the predominant effect of the increase in waterlogged area when higher priority is given to this indicator. No clear trend appeared when equal weight was assigned to all indicators. The effect of economic reforms implemented in 1977–78 in China is clearly reflected in the resulting ranking and clustering of the performance periods in the Shi-Jin irrigation district. Performance levels following reforms are shown to be consistently higher.Units mu
unit of area equal to 1/15 ha (666 m2)
- jin
unit of weight equal to 0.5 kg. 相似文献
155.
156.
N. Zapata E. Playán A. Martínez-Cob I. Sánchez J.M. Faci S. Lecina 《Agricultural Water Management》2007
In this paper, a contribution to the design of collective pressurised irrigation networks in solid-set sprinkler-irrigated windy areas is presented. The methodology is based on guaranteeing minimum on-farm performance, using a historical hourly wind speed database and a ballistic solid-set irrigation simulation model. The proposed method was applied to the Montesnegros Irrigation District (central Ebro basin, Spain). The district irrigates an area of 3493 ha using an on-demand schedule. The average wind speed in the area is 2.8 m s−1. An analysis of district water records showed that farmers often reduce water demand when the wind speed is high, but their irrigation decision making is limited by the capacity of the irrigation network and by the unpredictable character of local winds. Simulations were performed for 11 irrigation seasons, 2 triangular sprinkler spacings (18 m × 18 m and 18 m × 15 m), and 2 sprinkler models. The percentage of monthly suitable time for irrigation was determined for four management strategies. The first one was based on a wind speed threshold (3 m s−1), while the other three were based on three levels (standard, relaxed and restrictive) of two irrigation performance parameters: the Christiansen Uniformity Coefficient (CU) and the Wind Drift and Evaporation Losses (WDEL). The standard strategy classified the time as suitable for irrigation when CU ≥ 84% and WDEL ≤ 20%. The thresholds limits of the irrigation parameters for the relaxed strategy were CU ≥ 80% and WDEL ≤ 25%. Finally, the restrictive strategy used thresholds of CU ≥ 90% and WDEL ≤ 15%. The suitable time for the first strategy (56%) was always lower than for the standard and the relaxed strategies (with respective average values of 75 and 86%), and higher than for the restrictive strategy (30%). In order to design the collective network, the hydrant operating time was equalled to the suitable time for irrigation. The differences in the cost of the collective network plus the on-farm equipment were particularly relevant between the restrictive strategy and the other three. Differences in suitable operating time were clear between sprinkler spacings, and less evident between sprinkler models. The application of the proposed methodology may be limited by the availability of historical wind speed records and CU estimates for different combinations of sprinkler models, sprinkler spacings and wind speed. 相似文献
157.
企业作为社会的最基本的经济组织,其经营绩效的好坏直接关系到其自身的生存与发展。在企业绩效评价过程中,需要考虑大量定性和定量因素,其中有些因素具有不确定性、模糊性、随机性特点,而且因素间可能相互影响,这也就给科学客观的评价自身经营管理绩效带来一定的困难。网络分析法(ANP)是AHP基础上发展形成的一种新的决策方法,该方法考虑了不同层次之间的信息反馈与同一层次元素之间的相互依存关系。为此,将网络分析法应用于企业绩效评价,提出了基于网络分析法(ANP)的绩效评价模型。应用实例表明,ANP方法可有效的解决企业绩效评价问题,并使决策更为科学、合理。 相似文献
158.
159.
迷宫流道转角对灌水器水力性能的影 总被引:3,自引:2,他引:3
为研究齿形、梯形以及矩形流道转角变化对水力性能的影响,采用Fluent软件对不同形状下不同转角的流道进行了数值模拟.研究结果表明:当其他条件相同时,转角的变化与流量系数、流态指数呈负相关,其变化对梯形流道灌水器的流量系数影响最大,最多下降了19.03%,齿形流道次之,下降了10.14%,矩形流道是梯形流道转角角度增加的延伸,具有相同的水力性能变化规律;随着角度的增加,梯形流道总的局部水头损失系数最多增加了32.5%,而齿形流道总的局部水头损失系数最多增加了23.4%,变化都很明显;压力较高时,摩阻系数基本保持不变,流体为紊流状态. 相似文献
160.
介绍了汽车综合性能检测站数据库类型、设计、访问技术,论述了车型参数数据库系统的结构、特点和要求等.其结果表明,通过两年多的使用,车型参数数据库是一种有利解决广东省汽车综合性能检测的有效手段,能够更好地满足广东省汽车综合性能检测发展的实际需要,表明了数据库在广东省汽车综合性能检测站中的作用和意义. 相似文献