全文获取类型
收费全文 | 14693篇 |
免费 | 752篇 |
国内免费 | 1890篇 |
专业分类
林业 | 3540篇 |
农学 | 993篇 |
基础科学 | 1011篇 |
4198篇 | |
综合类 | 4730篇 |
农作物 | 812篇 |
水产渔业 | 279篇 |
畜牧兽医 | 754篇 |
园艺 | 207篇 |
植物保护 | 811篇 |
出版年
2024年 | 119篇 |
2023年 | 300篇 |
2022年 | 470篇 |
2021年 | 520篇 |
2020年 | 560篇 |
2019年 | 636篇 |
2018年 | 469篇 |
2017年 | 803篇 |
2016年 | 888篇 |
2015年 | 726篇 |
2014年 | 832篇 |
2013年 | 988篇 |
2012年 | 1172篇 |
2011年 | 1055篇 |
2010年 | 834篇 |
2009年 | 841篇 |
2008年 | 726篇 |
2007年 | 849篇 |
2006年 | 714篇 |
2005年 | 636篇 |
2004年 | 453篇 |
2003年 | 358篇 |
2002年 | 288篇 |
2001年 | 290篇 |
2000年 | 253篇 |
1999年 | 233篇 |
1998年 | 206篇 |
1997年 | 180篇 |
1996年 | 156篇 |
1995年 | 132篇 |
1994年 | 122篇 |
1993年 | 117篇 |
1992年 | 129篇 |
1991年 | 75篇 |
1990年 | 56篇 |
1989年 | 54篇 |
1988年 | 40篇 |
1987年 | 24篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1962年 | 4篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
红酵母的性质及其应用研究 总被引:10,自引:0,他引:10
红酵母是酵母菌的一个属,腐生,分布广泛,在医学、食品、化工和农业等方面都有一定的应用,但目前并没有引起人们足够的重视。综述了红酵母的种属特性、理化特性、培养及其应用。 相似文献
92.
93.
Jointing of titanium alloy and stainless steel is very often in the fields like aviation, chemical plants etc. The combination of materials has the advantages of both titanium alloy and stainless steel and will reduce the consumption of titanium resource. The phase transformation diffusion bonding of TA17 titanium alloy to 0CriSNigTi stainless steel are carried out on Gleeble - 1500D. The effcet of maximum thermal cycle temperature, the tensile strength, the fracture surface and microstruture of the joints are investigated. The results show that TiFe and TiFe2 intermetallics and some solid solutions are formed along the interface, when maximum thermal cycle temperature increase, the area proportion of intermetallics in the fracture surface increase, which are detrimental to the mechanical properties of the transition joints. 相似文献
94.
At present 18 wastewater treatment plants operateing in the Small towns of Three Gorge Areas of Chongqing Municipality, producing 132.95 tons surplus sludge everyday. As regards to the disposition of such numerous surplus sludge, the major disposition technique in these wastewater water treatment plants, i. e. , thickening and mechanical dewatering technique followed by feeding into the municipal solid waste landfill, seems to have a rather bad effect on the normal operation of the municipal solid waste landfill, due to the unstabilized sludge resulted from this technique of the sludge disposition and high moisture in the sludge, which is higher than 80%. This paper has paid some attention to this phenomenon. With respect to the small towns having the the municipal solid waste landfill, the techniques of mechanical dewatering, calcareousness stabilized etc. before feeding into the municipal solid waste landfill, seem to be feasible, while the composting and comprehensive utilization of sludge is available in the small towns which have no municipal solid waste landfills. 相似文献
95.
96.
In 1995, Padmanabhan and Vrat presented inventory models for deteriorating items with a constant selling price and stock dependent selling rate . Based on the result, in 2000, Kun-Jen Chung, Peter Chu and Shaw-Ping Lan devoloped the necessary and sufficient conditions of the existence and uniqueness of the optimal solutions of the profit per unit time functions without backlogging and with complete backlogging. Actually, the selling price need not be constant, it may be variable . This paper puts forward an EOQ model when the selling price is variable without backlogging, discusses the existence and uniqueness of optimum solution. The example is provided to illustrate the model. The theoretical evidence is provided for the inventory system to make management decision. 相似文献
97.
98.
Chen Qigao Feng Ya 《保鲜与加工》1993,(1)
This paper analyses the thermal moist characteristics of the hull layer beside an air layer at lower temperature in an envelope for a cold storage and presents a new method of waterproof by air layer. With test data from engineering practice, the theory on the barrier of self moisture proof at the surface sublayer of the hull layer in an attic on a cold storage is proven. The dried zone about three phase point is confirmed. It is a new knowledge for thermophysics on thermal design of a cold storage with an optimum thermal performance. 相似文献
99.
以乙二醇乙醚和精制大豆油在金属钠催化下合成出了豆油乙二醇乙醚酯生物柴油,考察了该生物柴油作为替代燃料在性能方面与柴油的差别;研究了作为柴油添加剂,其加入量对混合燃料性能的影响。结果表明,豆油乙二醇乙醚酯生物柴油的燃料特性达到了国外生物柴油生产标准,可以直接作为柴油使用,也可与矿物柴油掺合使用,提高了柴油的使用性能。 相似文献
100.