全文获取类型
收费全文 | 6514篇 |
免费 | 380篇 |
国内免费 | 674篇 |
专业分类
林业 | 1176篇 |
农学 | 501篇 |
基础科学 | 654篇 |
806篇 | |
综合类 | 2441篇 |
农作物 | 319篇 |
水产渔业 | 67篇 |
畜牧兽医 | 849篇 |
园艺 | 409篇 |
植物保护 | 346篇 |
出版年
2024年 | 26篇 |
2023年 | 98篇 |
2022年 | 206篇 |
2021年 | 213篇 |
2020年 | 200篇 |
2019年 | 269篇 |
2018年 | 184篇 |
2017年 | 261篇 |
2016年 | 332篇 |
2015年 | 343篇 |
2014年 | 368篇 |
2013年 | 409篇 |
2012年 | 548篇 |
2011年 | 480篇 |
2010年 | 393篇 |
2009年 | 392篇 |
2008年 | 312篇 |
2007年 | 374篇 |
2006年 | 339篇 |
2005年 | 246篇 |
2004年 | 232篇 |
2003年 | 172篇 |
2002年 | 132篇 |
2001年 | 144篇 |
2000年 | 114篇 |
1999年 | 112篇 |
1998年 | 89篇 |
1997年 | 75篇 |
1996年 | 68篇 |
1995年 | 59篇 |
1994年 | 69篇 |
1993年 | 55篇 |
1992年 | 51篇 |
1991年 | 42篇 |
1990年 | 35篇 |
1989年 | 32篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有7568条查询结果,搜索用时 31 毫秒
31.
32.
33.
种植方式与种植密度对大力士高粱的影响 总被引:1,自引:0,他引:1
本试验用裂区设计,研究了大力士高粱在16种不同种植密度、3种种植方式下,产草量、生产速度、茎叶比、茎粗的变化情况。结果表明,在撒播密度为18 kg/hm2、条播为22.5 kg/hm2、穴播为28.5 kg/hm2时达到最高产量;生长速度在第53-55 d时最高,达5.7 cm/d;茎叶比随着产量的增加逐渐减少;茎粗随着种植密度的增大而有减小的趋势。 相似文献
34.
体尺细分法在竞赛用伊犁马选择上的应用研究 总被引:3,自引:0,他引:3
本文采用体尺细分法 ,测定了乌鲁木齐马术俱乐部 2 4匹伊犁马 1 9个细分体尺及 1 0 0 0m速度成绩。分析细分体尺与速度的相关性 ,结果为 :颈长、肩长、肱骨长、股骨长、胫骨长、肩倾角、股骨倾角、髋骨倾角与速度呈显著 (P <0 0 5)或极显著 (P <0 0 1 )相关 相似文献
35.
AIM: To investigate whether berberine can induce rat mesenchymal stem cells (MSCs) to differentiate into neuron -like cells in vitro. METHODS: MSCs were separated from young rat femurs marrow and expanded in culture medium. MSCs were induced to differentiate by berberine. The morphological changes of MSCs were evaluated by light microscope.Neuron-spcific enolase (NSE), neurofilament (NF), glial fibrillary acidic protein (GFAP) were detected by immunohistochemistry. RESULTS: Induced by berberine for 8 hours,MSCs exhibited neurotype . The expression of NSE and NF in the neuron-like cells was positive, but the glial astrocyte marker GFAP didn't express. CONCLUSION: Berberine may induce adult rat MSCs to differentiate into neuron-like cells in vitro. 相似文献
36.
AIM: To evaluate the different conditions inducing mouse embryonic stem cells (ESC) in vitro to differentiate into cardiomyocytes. METHODS: BRL conditioned medium was used to promote the growth of ESC and maintain them in an undifferentiated state. During the inducing process, retinoic acid (RA), DMSO, activin-A and TGF-β1 were used as inducing reagents, and made up six kinds of differentiating medium. Then a three-step method inducing ESC cultured in hanging drops, in suspension and in plating was used to induce the differentiation of ESC. RESULTS: ESC were induced in vitro to differentiate into cardiomyocytes. Of all groups, the highest differentiating rate was observed in the group induced by activin-A (20 μg/L) and TGF-β1 (2 μg/L). CONCLUSION: The inducing conditions including activin-A (20 μg/L) and TGF-β1 (2 μg/L) is very valuable in inducing ESC differentiation into cardiomyocytes. 相似文献
37.
FANG Tian-ling MIN Jun DENG Xiao-geng QIAN Shi-kun CHU Zhong-hua CHEN Ya-jin SHAO Jing WEI Jing CHEN Ji-sheng 《园艺学报》2004,20(7):1167-1170
AIM: To explore a new method of hepatocyte growth factor (HGF) inducing bone marrow mesenchymal stem cells (MSC) to differentiate into cardiomyocytes. METHODS: Bone marrow MSC was cultured with DMEM media (10% fetal calf serum) 4-6 passages, and induced by HGF (10 μg/L) for 30 d. Automatical beating of the differentiated cells was observed daily with transverse microscopy, or under condition of 0.1% isoproterenol or cal-cium-deprived incubation. Specific cardiac myosin in the cells was indentified by immunochemistry. RESULTS: At 14-20 d of differentiation, bone marrow mesenchymal stem cells formed clones, in 10%-50% of which spontaneous beating cell-mass had come to continuously exist. Isoproterenol increased the beating rate and calcium-deprived media inhibited the beating. The cells were identified to be cardiomyocytes by expression of cardiac myosin heavy chain. CONCLUSION: HGF may induce bone marrow mesenchymal stem cells into cardiomyocytes with high efficiency, but the differentiating pathway of stem cells remains to be further studied. 相似文献
38.
Mesenchymal stem cells (MSCs) are a population of multipotent cells that can proliferate and differentiate into marrow and non-marrow cell types, such as adipocytes, chondrocytes, myocytes, and so on. In recent years, many researchers have studied whether MSCs are capable of differentiation into neurons in vivo and ex vivo. The result that MSCs-derived neurons express NSE and NF, but don't express GFAP suggests MSCs can differentiate into neurons, some researchers have achieved success in promoting functional recovery in Pakinsons and transactional spinal cord injury rat models by use of MSCs-derived neurons. Therefore, MSCs-derived neurons will play an important role in the therapy for a variety of diseases of the nervous system. 相似文献
39.
To develop the potential function of dairy cow mammary stem cells (DCMECs) in regulation of lactation,we identify putative DCMECs which were BrdU label retaining epithelial cells,at the same time,analysis the location of two new mammary stem cells molecular marks FNDC3B and PROCR to verify the feasibility of them to indicate DCMECs.The mRNA levels of prolactin,growth hormone,insulin-like growth factor-1 and their receptors were detected along with cell passage by Real-time quantitative PCR.The results showed that the proportion of BrdU label-retaining epithelial cells was nearly 0.4% after 25 d continuous culture (passaged 4 times) and few cells were positive for FNDC3B or PROCR.Moreover,we observed the BrdU labelled epithelial cells by asymmetric division.The mRNA levels of prolactin,growth hormone,insulin-like growth factor-Ⅰ and their receptors in primary and passage cells were extremely significant difference(P<0.01).DCMECs would rapidly lose some physiological characteristics and the ability of milk synthesis when not under the condition of induction of lactation differentiation,but a certain percentage of mammary stem/progenitor cells will be retained,whose potential effects on the regulation of lactation and mammary acinar remodeling were worthy of attention. 相似文献
40.
秃杉大径级用材林抚育采伐技术的研究 总被引:1,自引:0,他引:1
结合国家林业行业标准《秃杉速生丰产林》编制的要点,对秃杉大径级用材林抚育采伐进行了专项调查和研究;结合具体实际培育过程,有的放矢地提出了培育目标、分区生长指标以及抚育采伐的原则、对象和范围,为秃杉大径级用材林的培育提供了技术保障。 相似文献