全文获取类型
收费全文 | 30750篇 |
免费 | 707篇 |
国内免费 | 1796篇 |
专业分类
林业 | 5321篇 |
农学 | 3533篇 |
基础科学 | 1503篇 |
5361篇 | |
综合类 | 4719篇 |
农作物 | 2853篇 |
水产渔业 | 2307篇 |
畜牧兽医 | 3195篇 |
园艺 | 1533篇 |
植物保护 | 2928篇 |
出版年
2024年 | 41篇 |
2023年 | 141篇 |
2022年 | 403篇 |
2021年 | 577篇 |
2020年 | 507篇 |
2019年 | 491篇 |
2018年 | 3046篇 |
2017年 | 3117篇 |
2016年 | 1678篇 |
2015年 | 760篇 |
2014年 | 658篇 |
2013年 | 733篇 |
2012年 | 1602篇 |
2011年 | 3102篇 |
2010年 | 2956篇 |
2009年 | 2111篇 |
2008年 | 2100篇 |
2007年 | 2448篇 |
2006年 | 796篇 |
2005年 | 828篇 |
2004年 | 464篇 |
2003年 | 466篇 |
2002年 | 315篇 |
2001年 | 281篇 |
2000年 | 393篇 |
1999年 | 413篇 |
1998年 | 358篇 |
1997年 | 351篇 |
1996年 | 303篇 |
1995年 | 311篇 |
1994年 | 270篇 |
1993年 | 235篇 |
1992年 | 190篇 |
1991年 | 173篇 |
1990年 | 140篇 |
1989年 | 127篇 |
1988年 | 142篇 |
1987年 | 61篇 |
1986年 | 37篇 |
1985年 | 21篇 |
1984年 | 21篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1968年 | 4篇 |
1964年 | 3篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
以正常鸡胚尿囊液和环磷酰胺预处理试验兔, 再以Ⅰ型鸭肝炎病毒(Duck Hepatitis Virus Type Ⅰ, DHV Ⅰ) 标准强毒(ATCC, C9/D2) 接种后致死鸡胚的尿囊液, 经灭活、乳化制成油佐剂抗原多次免疫试验兔, 获得了鸡胚中和效价(EPD50) 达1∶32 以上的兔抗Ⅰ型鸭肝炎病毒高免血清(DHV ⅠS) 。 相似文献
52.
Shanli Zhu Mark Portman Beth M Cleveland Andrew D Magnuson Kun Wu Wendy Sealey Xin Gen Lei 《Journal of animal science》2021,99(1)
Dietary fish oil supplementation provides n-3 long-chained polyunsaturated fatty acids for supporting fish growth and metabolism and enriching fillet with eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; c22:6n-3). Two experiments were performed as a 3 × 2 factorial arrangement of dietary treatments for 16 wk to determine effects and mechanisms of replacing 0%, 50%, and 100% fish oil with DHA-rich microalgae in combination with synthetic vs. microalgal source of astaxanthin in plant protein meal (PM)- or fishmeal (FM)- based diets for juvenile rainbow trout (Oncorhynchus mykiss). Fish (22 ± 0.26 g) were stocked at 17/tank and 3 tanks/diet. The 100% fish oil replacement impaired (P < 0.0001) growth performance, dietary protein and energy utilization, body indices, and tissue accumulation of DHA and EPA in both diet series. The impairments were associated (P < 0.05) with upregulation of hepatic gene expression related to growth (ghr1and igf1) and biosynthesis of DHA and EPA (fads6 and evol5) that was more dramatic in the FM than PM diet-fed fish, and more pronounced on tissue EPA than DHA concentrations. The source of astaxanthin exerted interaction effects with the fish oil replacement on several measures including muscle total cholesterol concentrations. In conclusion, replacing fish oil by the DHA-rich microalgae produced more negative metabolic responses than the substitution of synthetic astaxanthin by the microalgal source in juvenile rainbow trout fed 2 types of practical diets. 相似文献
53.
It has been found that fibroblast growth factor receptor (FGF-FGFR) signaling can regulate the expression of adipocyte differentiation genes. FGF9 is one of the members of FGFs that mainly binds receptors FGFR2 and FGFR3. FGF9 is highly expressed in the adipose tissue of humans and mice, but there are few reports on the role of FGF9 in goat intramuscular adipocyte differentiation. Therefore, this study explored the effect of FGF9 on adipocyte differentiation through cell culture, interference, and overexpression. The expression of receptors FGFR1–FGFR4 in adipocyte differentiation and their effects on differentiation were detected to screen receptor gene of FGF9. Finally, the interaction between FGF9 and the receptor was tested by cotransfection. Our results showed that FGF9 interacts with FGFR2 to inhibit goat intramuscular adipocyte differentiation by regulating peroxisome proliferator-activated receptor gamma (PPARγ) and preadipocyte factor 1 (Pref1), which is a data support for subsequent pathway research. 相似文献
54.
55.
Pei-Pei Zhang Jing-Jing Wang Chong-Yang Li Hai-sheng Hao Hao-Yu Wang Wei-Hua Du Yun-Wei Pang Shan-Jiang Zhao Hui-Ying Zou Tong Hao Sha Yang Wei-Min Ruan Jin-Ming Huang Peng-cheng Jiao Hua-Bin Zhu Xue-Ming Zhao 《Reproduction in domestic animals》2020,55(9):1103-1114
The fertilization capacity of sex-sorted sperms is seriously decreased, which inhibits its wide application. However, little information is still available about the effect of vitamin C (VC) and lycopene (Lyc) on the fertilization capacity of sex-sorted bull sperm. In this study, the washing medium and fertilization medium of sex-sorted sperm from three bull individuals were supplemented with different concentrations of VC (0, 1 × 10–3, 1 × 10–4, 1 × 10–5, 1 × 10–6 M) or Lyc (0, 1 × 10–4, 1 × 10–5, 1 × 10–6, 1 × 10–7). After washing twice and incubation for 1.5 hr, the malondialdehyde (MDA) level, phosphatidylserine (PS) translocation, membrane potential (Δψm) and IVF (in vitro fertilization) ability of sex-sorted sperm were investigated. For the sex-sorted sperm of bulls A, B and C, 1 × 10–3 M VC or 1 × 10–4 M Lyc treatment significantly decreased their MDA levels and PS translocation and increased their Δψm levels and cleavage rates after IVF. When blastocysts were concerned, 1 × 10–4 M Lyc significantly improved the blastocyst rates and their IFN-tau expression of bulls A and C. In conclusion, supplementation of 1 × 10–3 M VC or 1 × 10–4 M Lyc in washing and fertilization medium contributed greatly to improving the fertilization capacity of sex-sorted bull sperm during IVF procedure. 相似文献
56.
深秋的北京,红了枫叶,黄了银杏,这是京华最美的季节,雄伟的北京人民大会堂格外庄严。全国饲料战线广大职工期盼已久的庆祝中国饲料工业协会成立20周年暨第五次全国会员代表大会于2005年11月5日在这里隆重举行。在步入会堂的人流中,有一支队伍格外引人注目:他们人数不多,但行进整齐;他们几乎都是年过六旬的老者,但步履矫健,充满自信;他们的头发大多斑白了,但胸前佩戴的红花映红了绽满欢笑的面容。他们就是受中国饲料工业协会特别邀请,来自全国各省、市和在京的部分离、退休的老饲料工作者,是上个世纪我国饲料工业初创阶段的拓荒者。为了弘扬… 相似文献
57.
Depending on its concentration, sodium chloride acts as either an attractant or a repellant to the infective larvae (L3i) of Strongyloides stercoralis. On a concentration gradient, L3i are attracted to 0.05 M NaCl, but repelled by 2.8M. To test the hypothesis that amphidial neurons ASE and ASH might mediate attraction and repulsion, respectively, these neurons, and control neurons as well, were ablated in hatchling larvae with a laser microbeam. After the larvae attained infectivity (L3i), they were tested on a NaCl gradient. When placed at low salinity, 73.5% of normal controls migrated "up" the gradient, while 26.4% crawled randomly. In contrast, only 20.6% of ASE-ablated L3i migrated "up" the gradient, while 79.4% migrated randomly. Ablation-control ASK-ablated L3i (58.8%) migrated "up" the gradient while 41.1% crawled randomly. When placed at a region of high salinity, 100% of normal control L3i migrated "down" the gradient, whereas 62.5% of ASH-ablated L3i migrated randomly, the remaining 37.5% migrating "down" the gradient. In sharp contrast with ASH-ablated L3i, 94.1% of ablation-control larvae, i.e. ASK-ablated L3i, migrated "down" the gradient. Migration behavior of ASE- and ASH-ablated L3i was significantly different (P < 0.001) from that of ASK-ablated L3i and normal controls. It is noteworthy that 87.5% of ASE-ablated L3i that failed to exhibit chemoattractive behavior were actively chemorepelled from high salinity. Also, 70.0% of ASH-ablated L3i that failed to be chemorepelled from high salinity were capable of chemoattractive behavior, indicating that the worms had retained their behavioral responses except for those associated with the targeted neurons. 相似文献
58.
59.
Qizhong SUN Fengqin GAO Zhu YU Ya TAO Shufen ZHAO Yimin CAI 《Animal Science Journal》2012,83(4):305-309
Effects of lactic acid bacteria (LAB) inoculants and cellulase additives on fermentation quality and chemical compositions of shrub silages were studied by using a small‐scale fermentation system. Two LAB inoculants of Qingbao (Lactobacillus plantarum, Pediococcus acidilacticii, Lactobacillus casei and Clostridium phage) and Caihe (Lactobacillus plantarum, Lactobacillus brevis and Pediococcus acidilactici) and a commercial cellulase made from Trichoderma reesei were used as additives for intermediate pea‐shrub, rush bushclover, arborescent ceratoides and shrubby silage preparation. The crude protein, neutral detergent fiber and water‐soluble carbohydrate contents of the four shrub materials were 10.1–14.2, 62.6–67.2 and 1.9–3.5% on a dry matter basis, respectively. All shrub silages had pH 3.40–4.43, ammonia‐N 0.1–0.2% g/kg and lactic acid 1.3–2.9% on a fresh matter basis. The silage quality of LAB‐inoculated silages did not have a greater effect than control silages, except shrubby silage preparation. Silages treated with the cellulase, the pH of rush bushclover and shrubby sweetvetch silage were significantly (P < 0.05) lower and the lactic acid content were significantly (P < 0.05) higher than the control silages. The results confirmed that shrub contained a relatively high content of crude protein; its silages can be preserved in good quality, and they are new potential resources for livestock feed. 相似文献