全文获取类型
收费全文 | 27713篇 |
免费 | 2138篇 |
国内免费 | 2947篇 |
专业分类
林业 | 2083篇 |
农学 | 1678篇 |
基础科学 | 4763篇 |
9111篇 | |
综合类 | 9034篇 |
农作物 | 765篇 |
水产渔业 | 1635篇 |
畜牧兽医 | 953篇 |
园艺 | 451篇 |
植物保护 | 2325篇 |
出版年
2024年 | 100篇 |
2023年 | 513篇 |
2022年 | 762篇 |
2021年 | 877篇 |
2020年 | 958篇 |
2019年 | 1067篇 |
2018年 | 865篇 |
2017年 | 1278篇 |
2016年 | 1575篇 |
2015年 | 1141篇 |
2014年 | 1382篇 |
2013年 | 1694篇 |
2012年 | 2273篇 |
2011年 | 2111篇 |
2010年 | 1716篇 |
2009年 | 1575篇 |
2008年 | 1562篇 |
2007年 | 1762篇 |
2006年 | 1472篇 |
2005年 | 1250篇 |
2004年 | 1052篇 |
2003年 | 879篇 |
2002年 | 723篇 |
2001年 | 684篇 |
2000年 | 555篇 |
1999年 | 438篇 |
1998年 | 391篇 |
1997年 | 343篇 |
1996年 | 321篇 |
1995年 | 286篇 |
1994年 | 305篇 |
1993年 | 199篇 |
1992年 | 166篇 |
1991年 | 162篇 |
1990年 | 103篇 |
1989年 | 84篇 |
1988年 | 55篇 |
1987年 | 56篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1963年 | 1篇 |
1962年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Sensitivity to Drought Stress of Three Soybean Cultivars During Different Growth Stages 总被引:1,自引:0,他引:1
Three soybean ( Glycine max L.) culivars, Lee-74, Wright , and Ra 401 , were subjected to 100 % (control), 75 %, and 50 % of field capacity during vegetative (VI), flowering (R2), and pod-filling (R4) stages in greenhouse and field studies. Stress applied at R2 significantly reduced the yield in the greenhouse, while in the field, the maximum reduction was observed when the plants were subjected to stress at R4. Stress during VI reduced the yield components less than stress applied during R2 or R4 stages in both studies. The pod number and seed weight were the yield components most affected by drought stress, and the number of seeds per pod the least affected. Yield stress index was significantly correlated with the yield and its components. The reproductive stage was clearly more sensitive to drought than the vegetative stage. The cultivar Lee 74 had the highest yield and the second highest yield stress index whereas the cultivar Ra 401 had the lowest yield. 相似文献
992.
CHEN Deng-fu SUN Ming-yue FENG Ke ZHAO Zhan-feng DONG Ling-yan WEN Liang-ying PAN Yan-hua 《保鲜与加工》2004,(9):67-71
A numerical simulation commercial software has been developed by the object-oriented Visual Basic programming language on the basis of the 2D mathematical model of secondary cooling Process in billet continuous casting. Thereby an effective experimenting tool for computer simulation of continuous casting process is gained. By simulation with the software, the caster structures and operating parameters in continuous casting can be designed and optimized. The simulating calculation examples on several casters and its production applications indicate that the commercial software developed has more accuracy, practicability and commonality, as also as simpler operating capability. The simulated results have been successfully applied to the design and production of the high-efficiency modification for several billet casters interiorly. 相似文献
993.
John Connell 《Asia Pacific viewpoint》2006,47(3):342-350
Abstract: Effective global competitiveness is rare in the Pacific islands, yet FIJI Water has been a major success story since 1997, exporting bottled water to the USA and elsewhere. A bland commodity has been linked to an ‘exotic’ place, and sold to elite consumers, as a form of cultural capital. The company website and newspaper extol the virtues of a ‘pristine’ product, produced in a natural context, in an environmentally sensitive manner. Marketing these themes and product placement have enabled success in a highly competitive market. Place has been used as a means of marketing perceived taste, distinctiveness and quality. 相似文献
994.
With the development of industrial automation technology, the monitoring system becomes more and more important in the control system. The paper discusses the monitoring system design based on the pump station for high press water. At first, the paper introduced the base process and the control system of the pump station for high press water. The control system includes two parts: upper part and lower part. The control network consisted of some PLC controls the device in the system. Then the method of the OOP technology application to the monitoring system design are emphatically introduced and discussed. Finally, the paper briefly introduced the main function models and the key technologies. 相似文献
995.
Experimental Study about Activated Water Produced by the Method of Electro-hydraulic Impulse Improving the Mechanical Performance of Mortar 总被引:1,自引:0,他引:1
图1微型库平面示意射阳地区气候湿润、四季多雨,蒜薹味甜微辣、脆嫩、鲜绿、耐贮,主要分布在藕耕、千秋、临海、六垛等地区。种植面积达1.3万hm2,总贮量达4000~8000万t,已成为当地蒜农的经济支柱和政府产业结构调整的重点方向。但蒜薹采收期一般在5月10日左右,正值高温季节,采收时间仅4~5天,常因销售不及时而造成大量损失。为此蒜农和地方政府极为重视蒜薹采后贮藏保鲜、减损、保值、增值工作。当地政府于2000~2001年先后引进35座微型节能冷库简称微型库,使以前只有依靠国家经费或贷款才能建造的… 相似文献
996.
997.
HE Xue-bing 《保鲜与加工》2004,(5):78-80102
The paper introduces an example and its running data of applying conditioning-controlling water-water ejector heating unit developed by the author in heating system. It proves that: the hydraulic stability of the system is very good. When heating medium of heat source and heat consumer are respective high-temperature water and low-temperature water, the hydraulic stability of the heating system is close to 1; when the flow of any consumer of heating network changes, the flow and heating quality of other consumers are almost unchanged. 相似文献
998.
土壤水分胁迫对冬小麦耗水规律及产量的影响 总被引:10,自引:1,他引:10
在温定盆栽和池栽防雨旱棚条件下,研究了土壤水胁迫对冬小麦耗水规律及产量的影响,结果表明,随土壤水分胁迫加剧,干物质积累减少,子粒千物质来自贮藏同化物的比例上升,产量下降,产量构成三因子中穗粒数,亩穗数下降均极显著,而千粒重下降较少,随水分胁迫加剧,拔节前耗水量占总耗水量的比率增高,从播种到拔节期,耗水量占总耗水量的比例愈高,拔节后植株衰老死亡愈早,产量降低就愈大,中度水分胁迫下,虽然水分生产率和经 相似文献
999.
1000.
Summary Significant genetic variation in CO2 assimilation rate (A), stomatal conductance (g), and A: g ratio, which are indicators of intrinsic differences in productivity and water use efficiency (WUE), has been demonstrated in grain sorghum [Sorghum bicolor (L.) Moench] hybrids. The primary objective was to determine the possible parental influence on the components of the A: g relationship in sorghum hybrids across a range of water supplies. Thirty F1 hybrids resulting from a 6 × 6 diallel crossing pattern constituted the genetic material. Field experiments were conducted using four water supply treatments established through differential irrigation. Carbon assimilation rate (A), g, and leaf water potential (w) of individual leaves were monitored every 15 to 20 days. Genetic analyses revealed that general- and specific-combining ability effects were evident for A. However, reciprocal and maternal effects were more important in governing the A-g and A-w relationships. Since the maternal effects were the major determinants in causing reciprocal differences, A can be improved by selecting specific female parents to exploit cytoplasmic factors or physiological characteristics of this parent. Substantial genetic variation in the A-g relationship resulting from significant genetic control of A offers the opportunity to impose selection for high A and stability of A, which might directly contribute to whole plant WUE and productivity in grain sorghum.Abbreviations A
carbon assimilation rate
- g
stomatal conductance to water vapor
- GCA
General Combining Ability
- SCA
Specific Combining Ability
- WUE
Water Use Efficiency 相似文献