全文获取类型
收费全文 | 35597篇 |
免费 | 1379篇 |
国内免费 | 1576篇 |
专业分类
林业 | 4827篇 |
农学 | 3153篇 |
基础科学 | 359篇 |
2033篇 | |
综合类 | 14380篇 |
农作物 | 2429篇 |
水产渔业 | 1415篇 |
畜牧兽医 | 4077篇 |
园艺 | 2437篇 |
植物保护 | 3442篇 |
出版年
2024年 | 75篇 |
2023年 | 229篇 |
2022年 | 394篇 |
2021年 | 505篇 |
2020年 | 563篇 |
2019年 | 601篇 |
2018年 | 444篇 |
2017年 | 726篇 |
2016年 | 1057篇 |
2015年 | 915篇 |
2014年 | 1406篇 |
2013年 | 1717篇 |
2012年 | 2281篇 |
2011年 | 2282篇 |
2010年 | 1876篇 |
2009年 | 1905篇 |
2008年 | 1946篇 |
2007年 | 2209篇 |
2006年 | 1822篇 |
2005年 | 1759篇 |
2004年 | 1312篇 |
2003年 | 1133篇 |
2002年 | 1060篇 |
2001年 | 1183篇 |
2000年 | 955篇 |
1999年 | 933篇 |
1998年 | 711篇 |
1997年 | 632篇 |
1996年 | 694篇 |
1995年 | 773篇 |
1994年 | 777篇 |
1993年 | 491篇 |
1992年 | 501篇 |
1991年 | 427篇 |
1990年 | 465篇 |
1989年 | 405篇 |
1988年 | 425篇 |
1987年 | 280篇 |
1986年 | 136篇 |
1985年 | 107篇 |
1984年 | 94篇 |
1983年 | 65篇 |
1982年 | 47篇 |
1981年 | 41篇 |
1980年 | 36篇 |
1979年 | 33篇 |
1978年 | 34篇 |
1977年 | 50篇 |
1976年 | 12篇 |
1955年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 362 毫秒
61.
花生DNA导入大豆育种效果的研究 总被引:3,自引:0,他引:3
利用花粉管通道在大豆自花授粉后将花生DNA导入栽培大豆受体中,引起受体的结荚习性、株高、成熟期,主茎节数、分枝数、产量性状和化学品质等性状的广泛变异。对变异株进行选择,获得了产量比受体提高11.9%~25.1%,蛋白质含量提高3.9%~5.3%的变异株系。实验结果表明:利用外源DNA导入技术进行生态性状、产量性状和化学品质方向的育种是可能的。 相似文献
62.
对永城县1982年至1987年土壤养分变化动态进行了定点分析研究.共分析了三十个乡的257个土样。土壤有机质和氮素含量1987年比1982年相应提高25%和41.4%;而速效磷和钾则相应降低36.1%和89.9%;微量元素有效锌、硼、钼含量均属中低级水平。据此提出了相应的培肥措施. 相似文献
63.
64.
水飞蓟对动物机体免疫功能的影响研究 总被引:2,自引:0,他引:2
将小鼠分为四组,分别饲喂10%水飞蓟、20%水飞蓟、环磷酰胺(0.01g/kg)和空白对照(常规饲料),研究对小鼠免疫功能的影响。实验结果证明,水飞蓟各剂量组能增高小鼠外周血白细胞数目(P<0.01、0.001);提高小鼠腹腔巨噬细胞的吞噬率(P<0.001,0.001)及吞噬指数(P<0.05、0.001)并随剂量加大有增强的趋势;能促进小鼠淋巴细胞转化,提高淋巴细胞转化百分率(P<0.01、0 相似文献
65.
本文报道了江西三种危害食用菌的绿色霉菌的生物学特性。它们是:绿色木霉(Trichoderma Viride pers exFn)。产黄青霉(Penicillium Chrysoenum Thom)和构巢曲霉(Aspergillus nidulcms(Eidzm)Winter)。 相似文献
66.
67.
68.
M. Özgen 《Journal of Agronomy and Crop Science》1991,166(5):318-325
The purpose of this study was to compare responsiveness to environment as well as the stability of newly developed promising lines with traditional commercial cultivars. Subject research was conducted in Ankara between 1983-1989 on common and durum wheat cultivars and lines. Regression coefficient (b) was used as the criterion of genotypes' responsiveness to environment whereas deviation from regression (S2 d) and coefficient of determination (r2 ) were used as stability parameters. Each experiment year was regarded as an environment and yield average of each year was used as the environmental index.
In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological regions. 相似文献
In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological regions. 相似文献
69.
The effect of salinity on seed germination, plant yield parameters, and plant Na, Cl and K concentrations of chickpea and lentil varieties was studied. Results showed that in both crops percentage emergence was significantly reduced by increasing NaCl levels (0–8dSm?1). From the plant growth studies it was found that differences existed among chickpea and lentil varieties in their response to NaCl application. In chickpea, the variety Mariye showed the comparatively lowest germination percentage and the lowest seedling shoot dry weight in response to salinity and was also among the two varieties which had the lowest relative plant height, shoot and root dry weight and grain yield at maturity. Similarly, variety DZ-10-16-2, which was the second best in germination percentage and the highest in terms of seedling shoot dry weight, also had the highest relative plant height, shoot and root dry weights, and grain yield at maturity. In lentil, however, such relationships were less pronounced. Chloride concentration (mg g?1) in the plant parts at salt levels other than the control was about 2–5 times that of Na. K concentration in the plants was significantly reduced by increasing NaCl levels. Chickpea was generally more sensitive to NaCl salinity than lentil. While no seeds were produced at salinity levels beyond 2dSm?1 in chickpea (no seeds were produced at this salt level in the most sensitive variety, Mariye), most lentil varieties could produce some seeds up to the highest level of NaCl application. Overall, varieties R-186 (lentil) and Mariye (chickpea) were the most sensitive of all varieties. On the other hand, lentil variety NEL-2704 and chickpea variety DZ-10-16-2 gave comparatively higher mean relative shoot and root dry weights, and grain yield, thus showing some degree of superiority over the others. The observed variations among the varieties may be useful indications for screening varieties of both crops for salt tolerance. 相似文献
70.
本试验所用动物为53—57日龄雄性大白鼠(sprague——Dawley品系),初始体重为121.73±3.95g,试验期为大白鼠生长发育旺期的21天。试验拟研究不同粗蛋白水平(10%、15%、20%、25%和30%)及两个能量水平(消化能:3.6和3.9kcal/g)的饲粮对大白鼠生长发育及各种体成分的影响。结果表明,当饲粮蛋白质供应充分时,大白鼠生长随饲粮能量浓度的提高而改善;而当饲粮蛋白质供应感觉不足时,提高能量浓度对生长无益。机体各项成分指杯中,以蛋白质、脂肪、水分沉积受饲粮蛋白质,能量浓度影响显著;而蛋白质、脂肪沉积在很大程度上受饲粮能朊比的影响,饲粮中添加脂肪可使大白鼠机体肥胖。 相似文献