全文获取类型
收费全文 | 887篇 |
免费 | 62篇 |
国内免费 | 86篇 |
专业分类
林业 | 171篇 |
农学 | 145篇 |
基础科学 | 49篇 |
104篇 | |
综合类 | 259篇 |
农作物 | 71篇 |
水产渔业 | 39篇 |
畜牧兽医 | 134篇 |
园艺 | 20篇 |
植物保护 | 43篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 29篇 |
2021年 | 36篇 |
2020年 | 33篇 |
2019年 | 40篇 |
2018年 | 26篇 |
2017年 | 36篇 |
2016年 | 23篇 |
2015年 | 28篇 |
2014年 | 26篇 |
2013年 | 37篇 |
2012年 | 42篇 |
2011年 | 49篇 |
2010年 | 57篇 |
2009年 | 51篇 |
2008年 | 49篇 |
2007年 | 56篇 |
2006年 | 49篇 |
2005年 | 42篇 |
2004年 | 15篇 |
2003年 | 21篇 |
2002年 | 21篇 |
2001年 | 24篇 |
2000年 | 21篇 |
1999年 | 27篇 |
1998年 | 22篇 |
1997年 | 24篇 |
1996年 | 31篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有1035条查询结果,搜索用时 15 毫秒
111.
对桉属7个种11个种批进行生长和耐冻性的联合选择研究.选出在冷凉地区较有潜力的邓恩桉17913、20665和17922以及本沁桉18788共4个种批,蓄积量14.80 ~20.93 m3/a·hm2,这为国内冷凉地区发展短轮伐期桉树用材林提供了可供选择的速生、耐冻的种植材料.另外,多雷苷桉虽然生长中等(蓄积量10.03 m3/a·hm2),但耐冻性好,可以作为进一步选择和杂交育种的备用材料. 相似文献
112.
113.
In order to analyze the effect of different temperatures on PAOs decay, a lab scale EBPR culture with PAOs over 90%±2% of the entire bacterial was used under different conditions (10℃ anaerobic, 10℃ aerobic, 20℃ anaerobic, 20℃ aerobic). The results show that the decay rate increases with the increase of temperature; the average rate during 1~9 days is (respectively: 10℃ anaerobic, 10℃ aerobic, 20℃ anaerobic, 20℃ aerobic) 0.053/d, 0.50/d, 0.072/d, and 0.145/d; the cell death rate is 0.019/d, 0.017/d, 0.019/d, and 0.03/d, which accounts for 35.8%, 34%, 26.4%, and 20.7% of the decay rate, respectively. The concentration of PHA and glycogen decreases during the decay period. And Glycogen degrades quickly in anaerobic conditions than in aerobic conditions under the same temperature. The glycogen degrade rate is higher with the increase of temperature under the same anaerobic and aerobic conditions. 相似文献
114.
H Zhang K Nagaoka K Imakawa Y Nambo G Watanabe K Taya Q Weng 《Reproduction in domestic animals》2013,48(3):423-428
The establishment of equine pregnancy is a unique and long process during which a series of physical and possibly biochemical interactions are required between the conceptus and uterus. In this study, we investigated the expression pattern of inhibin/activin subunits in the uterus during early pregnancy. The uteri from four adult mares on cyclic day 13 or pregnancy day 25 were obtained. Immunohistochemical experiments suggested that inhibin/activin subunits were immunolocalized in the luminal and glandular epithelium on pregnancy day 25. In addition, the inhibin α and inhibin/activin βB subunits were not detected, and inhibin/activin βA subunit was detected, in the luminal and glandular epithelium on cyclic day 13. Real‐time polymerase chain reaction and Western blotting results for the inhibin/activin subunits suggested a significant increase in the expression of inhibin/activin subunit βB and a significant decrease in the expression of inhibin/activin subunit βA on pregnancy day 25 compared with those on cyclic day 13. Enzyme‐linked immunosorbent assays suggested a significant decrease in the concentration of activin A in endometrium extracts from cyclic day 13 to pregnancy day 25. These results suggest that inhibins or activins synthesized in the uterus, as endocrine factors and necessary nutriments, have different expression patterns and may play different, important roles during early embryonic development of the equine. 相似文献
115.
116.
Rongbo Wang Shuzhun Chen Bowen Zheng Peiqing Liu Benjin Li Qiyong Weng Qinghe Chen 《Forest Pathology》2019,49(5)
Taxus chinensis is a valuable tree with uses for timber, medicinal, ornamental and landscape purposes. Most importantly, it is a source of the anti‐cancer drug paclitaxel. In 2016, needle spot disease was observed on T. chinensis in Fujian Province of China. Five isolates of similar morphology were isolated from diseased samples. The pathogen was identified as Neopestalotiopsis clavispora based on morphological and cultural characteristics and confirmed by sequence analysis of the internal transcribed spacer region (ITS) and the large subunit ribosomal RNA gene (LSU). The pathogenicity of the isolates was confirmed by fulfilling Koch's postulates. To the best of our knowledge, this is the first report to indicate that the causal agent of needle spot disease on Chinese yew in China is N. clavispora. 相似文献
117.
Sedqyar M Weng Q Watanabe G Kandiel MM Takahashi S Suzuki AK Taneda S Taya K 《The Journal of reproduction and development》2008,54(2):100-106
The objective of this study was to investigate the changes in secretion of inhibin and cellular localization of the inhibin alpha and inhibin/activin (beta(A) and beta(B)) subunits in male Japanese quail from 1 to 7 weeks after hatching. The post-hatch profile of plasma luteinizing hormone (LH), immunoreactive (ir) inhibin and testosterone were measured by radioimmunoassay. Testes were immunostained by the avidin-biotin-peroxidase complex method (ABC) using polyclonal antisera raised against inhibin alpha, inhibin/activin beta(A) and inhibin/activin beta(B) from one week of age to sexual maturity. Testicular weight increased gradually until 4 weeks and abruptly increased from 5 weeks of age onwards. The plasma concentrations of LH and ir-inhibin increased significantly at 5 weeks of age, and the plasma concentration of testosterone increased significantly at 6 weeks of age. Pituitary contents of LH showed a steady increase until 6 weeks of age and then abruptly increased at 7 weeks of age. Coincident to the increase in plasma testosterone, the testicular contents of testosterone significantly increased from 5 weeks through sexual maturity. Immunohistochemically, localization of the inhibin/activin alpha, beta(A) and beta(B) subunits was found in the Sertoli and Leydig cells at all ages of development from one week of age to sexual maturity. These results suggest that Sertoli and Leydig cells are the major source of inhibin secretion during development in male Japanese quail. 相似文献
118.
Weng Q Shi Z Kawaguchi M Watanabe G Taya K 《The Journal of reproduction and development》2008,54(5):397-401
Characteristic daily increases in the plasma levels of luteinizing hormone (LH) are present every afternoon during lactation in golden hamsters. The objective of this study was to investigate the effect of the diurnal rhythm of increases in LH on expression of nerve growth factor (NGF), its receptors trkA and p75 and inhibin alpha-subunit in the ovarian interstitial cells of lactating golden hamsters. Both lactating and non-lactating groups of postpartum golden hamsters were used in this study. The expression of NGF, its receptors trkA and p75 and inhibin alpha-subunit were determined by immunohistochemistry. Positive staining of NGF, trkA and p75 was found in the interstitial cells of the lactating group, and no immunoreactivity for NGF, trkA or p75 was observed in the ovarian interstitial cells of the non-lactating group. In addition, immunostaining of inhibin alpha-subunit was also observed in the interstitial cells of the lactating group but not in those of the non-lactating group. Immunostaining of the inhibin/activin beta(A)- and beta(B)-subunits was observed in the granulosa cells of antral follicles, but not in the interstitial cells of the lactating and non-lactating animals. These results suggest that the diurnal rhythm increases in LH can induce expression of NGF, trkA, p75 and inhibin alpha-subunit in the ovarian interstitial cells of lactating golden hamsters and that NGF, its receptors trkA and p75 and inhibin alpha-subunit may have the capacity for autocrine or paracrine modulation of interstitial cell differentiation in golden hamsters. 相似文献
119.
Lee DN Chuang YS Chiou HY Wu FY Yen HT Weng CF 《Journal of animal physiology and animal nutrition》2008,92(4):463-470
This study attempted to determine ingested porcine epidermal growth factor (pEGF) on the gastrointestinal tract development of early-weaned piglets. Thirty-two piglets (14-day weaned) were randomly allotted to supplemented with 0 (control), 0.5, 1.0, or 1.5 mg pEGF/kg diet. Each treatment consisted of four replicates with two pigs per pen for a 14 days experimental period. Piglets were sacrificed and gastrointestinal tract samples were collected to measure mucosa morphology, mRNA expression and activities of digestive enzymes in the gastrointestinal tract of piglets at the end of the experiment. Diets supplemented with pEGF failed to influence growth performance but tended to increase jejunal mucosa weight (p < 0.09) and protein content (p < 0.07). Piglets supplemental pEGF induced incrementally the gastric pepsin activity (p < 0.05) and stimulated jejunal alkaline phosphatase (ALP) and lactase activities accompanied with the increase of jejunal ALP and maltase mRNA expression. No effect of pEGF on the activities of all enzymes in ileum except the stimulation of ileal aminopeptide N mRNA expression. These results reveal that dietary pEGF supplementation might enhance gene expression and activities of digestive enzymes in the stomach and jejunum of piglets. 相似文献
120.