全文获取类型
收费全文 | 7509篇 |
免费 | 3397篇 |
国内免费 | 3篇 |
专业分类
林业 | 387篇 |
农学 | 460篇 |
基础科学 | 9篇 |
1636篇 | |
综合类 | 109篇 |
农作物 | 122篇 |
水产渔业 | 2549篇 |
畜牧兽医 | 4301篇 |
园艺 | 20篇 |
植物保护 | 1316篇 |
出版年
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 148篇 |
2020年 | 479篇 |
2019年 | 1044篇 |
2018年 | 916篇 |
2017年 | 952篇 |
2016年 | 947篇 |
2015年 | 835篇 |
2014年 | 820篇 |
2013年 | 1040篇 |
2012年 | 514篇 |
2011年 | 515篇 |
2010年 | 627篇 |
2009年 | 295篇 |
2008年 | 298篇 |
2007年 | 125篇 |
2006年 | 160篇 |
2005年 | 134篇 |
2004年 | 142篇 |
2003年 | 134篇 |
2002年 | 136篇 |
2001年 | 90篇 |
2000年 | 113篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 19篇 |
1996年 | 8篇 |
1995年 | 28篇 |
1994年 | 18篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 18篇 |
1989年 | 11篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1970年 | 11篇 |
1968年 | 9篇 |
1958年 | 6篇 |
1938年 | 10篇 |
1931年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Rudolf Geiger und Hans Amann 《Forstwissenschaftliches Centralblatt》1931,53(10):341-351
Ohne Zusammenfassung 相似文献
12.
A. Levakovi und Hans Muggenthaler 《Forstwissenschaftliches Centralblatt》1927,49(15):555-560
Ohne Zusammenfassung 相似文献
13.
14.
15.
16.
Mycoplasma pneumonia of swine (MPS) resistance and immune characteristics of pig lines generated by crossing an MPS pulmonary lesion selected Landrace line and a highly immune capacity selected Large White line 下载免费PDF全文
Liushiqi Borjigin Tomoyuki Shimazu Yuki Katayama Kouichi Watanabe Haruki Kitazawa Sang‐gun Roh Hisashi Aso Kazuo Katoh Takafumi Uchida Yoshihito Suda Akiko Sakuma Mituru Nakajo Keiichi Suzuki 《Animal Science Journal》2016,87(8):972-981
To understand the influence of crossbreeding on Mycoplasma pneumonia of swine (MPS) resistance and immune characteristics, two crossbred lines were characterized. One crossbred line, LaWa, was generated by crossing the MPS pulmonary lesion selected Landrace line (La) and the highly immune‐selected Large White line (Wa). The second crossbred line, LaWb, was generated by crossing the La line and the nonselected Large White line (Wb). The crossbred LbWb line (nonselected Landrace line × nonselected Large White line) and the La line were used as controls. The LaWa and LaWb lines had an intermediate level of MPS lung lesions between La and LbWb lines, although the difference was not statistically significant. After stimulation with sheep red blood cells (SRBCs), the LaWb and LaWa lines showed immune characteristics similar to that of the La line; the number of monocytes in peripheral blood increased, while B cells, T cells, secretion of SRBC‐specific immunoglobulin G, and interleukin (IL)‐13 decreased. Additionally, the number of natural killer (NK) cells and the expression of IL‐4 and IL‐17 were significantly higher in the LaWb and LaWa lines, respectively. These data suggested that crossbreeding of La and Wa lines resulted in the inheritance of some of the selected immune responses. 相似文献
17.
Effects of road transportation on metabolic and immunological responses in Holstein heifers 下载免费PDF全文
Hyeok‐Joong Kang In Kyu Lee Min‐Yu Piao Chae‐Won Kwak Min Jeong Gu Cheol Heui Yun Hyun‐Jin Kim Hyeon‐Ju Ahn Hee‐Bal Kim Gyeom‐Heon Kim Soo‐Ki Kim Jong‐Youl Ko Jong K. Ha Myunggi Baik 《Animal Science Journal》2017,88(1):140-148
This study examined the effects of road transportation on metabolic and immunological responses in dairy heifers. Twenty Holstein heifers in early pregnancy were divided into non‐transported (NT; n = 7) and transported (T; n = 13) groups. Blood was collected before transportation (BT), immediately after transportation for 100 km (T1) and 200 km (T2), and 24 h after transportation (AT). The T heifers had higher (P < 0.05) blood cortisol and non‐esterified fatty acid concentrations after T1 and T2 than did NT heifers. By contrast, the T heifers had lower (P < 0.05) serum triglyceride concentrations after T1 and T2 than had the NT heifers. The serum cortisol and triglyceride concentrations returned (P > 0.05) to the BT concentrations at 24 h AT in the T heifers. The granulocyte‐to‐lymphocyte ratio and the percentage of monocytes were higher (P < 0.05) after T2 in the T heifers than in the NT heifers, suggesting that transportation stress increased the numbers of innate immune cells. T heifers had higher (P < 0.01) plasma haptoglobin concentrations than NT heifers 24 h AT. In conclusion, transportation increased cortisol secretion and was correlated with increased metabolic responses and up‐regulation of peripheral innate immune cells in dairy heifers. 相似文献
18.
Ultrastructure of the tubular glands in the isthmus region of the oviduct in laying and natural moulting commercial egg‐type chickens 下载免费PDF全文
Mary‐Cathrine Nyasha Madekurozwa Mike M. Mpango 《Anatomia, histologia, embryologia》2018,47(5):493-497
The study investigated the ultrastructural characteristics of tubular gland and duct cells, as well as luminal gland cells in the isthmus region of the oviduct of laying and natural moulting hens. Tubular glands in laying birds were composed of type 1 and 2 cells. Based on the preponderance of each cell type, in relation to the location of a developing egg in the oviduct of the domestic fowl, these gland cells may represent different functional states of the same cell. The findings of the study on natural moulting birds suggest that autophagy is a process confined to the early stages of degeneration, while necrosis occurs in the terminal stages. 相似文献
19.
Effects of the dietary protein to energy ratio on growth,feed utilization and body composition in Macrobrachium nipponense 下载免费PDF全文
N.‐N. Zhang Q.‐Q. Ma W.‐J. Fan Q. Xing Y.‐L. Zhao L.‐Q. Chen J.‐Y. Ye M.‐L. Zhang Z.‐Y. Du 《Aquaculture Nutrition》2017,23(2):313-321
Oriental river prawn (Macrobrachium nipponense) has been widely cultured in Asian countries. However, its nutritional studies are very limited. In the present 8‐week study, we investigated the effects of dietary protein to energy ratio (P/E ratio) on the growth, feed utilization and body composition in juvenile M. nipponense (initial weight 0.302 ±0.03 g). Two‐factor experiment was designed and nine semi‐purified diets were formulated to contain three lipid levels (20, 80 and 140 g kg?1) and three protein levels (330, 380 and 430 g kg?1), producing P/E ratios from 16.5 to 23.4 mg KJ?1 protein. The results indicated that the growth, survival rate and protein efficiency were dose dependently improved by the increased dietary lipid, but not dietary protein content. Increased dietary lipid content and/or protein content increased lipid accumulation in whole body, hepatopancreas and muscle, but did not change the feed intake and hepatopancreas weight. In conclusion, our present study indicated that M. nipponense is a species with relatively high‐energy requirement. It could utilize dietary lipid content up to 140 g kg?1, while the dietary protein with more than 330 g kg?1 would not promote growth and protein efficiency. Taken together, 330 g kg?1 dietary protein and 140 g kg?1 dietary lipid level with P/E ratio 16.49 could be optimum for M. nipponense. 相似文献
20.
S. Leal‐Soto R. Barraza‐Guardado R. Castro‐Longoria J. Chvez‐Villalba F. Hoyos‐Chirez 《Journal of the World Aquaculture Society》2011,42(6):789-800
Pen shells are economically important and most are threatened by overexploitation and habitat degradation. Cultivation represents an alternative for preserving the resource and increasing the production. Atrina maura was cultivated in a suspension system which was followed by a bottom phase. Samples of pen shells and tissues were collected monthly to measure absolute growth, shell height increase, and an adductor muscle index. After the trials, adults shell height was 195 ± 10 mm, total weight was 223 ± 28 g, and mean shell height increase was 0.81 cm/mo. Protective devices were vital to avoid predation by crabs and fish; survival was 90% in the suspension phase and 70% in the bottom phase. Variations in the muscle index were apparently related to reproduction, suggesting activity (partial spawning) from August 2008 to April 2009 in juveniles and a major spawning in adults during August 2009. Adductor muscles reached a mean of 21 g after 20 mo of cultivation, but muscle weights decreased significantly after reproduction (August to November 2009). Results indicated that A. maura is suitable for aquaculture and the cultivation system adopted here should be tested in pilot‐scale ventures. This system may work with other species of pen shells. 相似文献