首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1332篇
  免费   47篇
  国内免费   2篇
林业   109篇
农学   41篇
基础科学   1篇
  203篇
综合类   94篇
农作物   34篇
水产渔业   95篇
畜牧兽医   731篇
园艺   8篇
植物保护   65篇
  2023年   6篇
  2022年   11篇
  2021年   19篇
  2020年   17篇
  2019年   17篇
  2018年   29篇
  2017年   24篇
  2016年   24篇
  2015年   19篇
  2014年   40篇
  2013年   120篇
  2012年   78篇
  2011年   77篇
  2010年   37篇
  2009年   34篇
  2008年   65篇
  2007年   66篇
  2006年   63篇
  2005年   79篇
  2004年   55篇
  2003年   47篇
  2002年   34篇
  2001年   51篇
  2000年   42篇
  1999年   30篇
  1998年   11篇
  1997年   4篇
  1996年   8篇
  1995年   6篇
  1994年   4篇
  1993年   8篇
  1992年   20篇
  1991年   28篇
  1990年   29篇
  1989年   25篇
  1988年   17篇
  1987年   26篇
  1986年   16篇
  1985年   23篇
  1984年   10篇
  1983年   8篇
  1981年   3篇
  1980年   4篇
  1979年   7篇
  1978年   4篇
  1977年   6篇
  1971年   3篇
  1969年   4篇
  1964年   2篇
  1933年   2篇
排序方式: 共有1381条查询结果,搜索用时 31 毫秒
61.
62.
Strains of Pseudomonas aeruginosa isolated from diseased dogs in Tokyo area during 1983 through 1986 were serotyped and assayed for antimicrobial susceptibility to obtain an epizootiological aspect of canine P. aeruginosa infection. Major sources of specimens were ear and nasal discharges and urine. The results of O-antigen typing using a monoclonal antibody kit showed that the most predominant serotype was type M. Types G and B were also major serotypes. In a yearly distribution of serotypes, type I was almost limited in 1986, and was isolated mainly from surgical wounds, which showed an episode of nosocomial infection, whereas that of type M or B was dispersed during 4 years from 1983 to 1986. As a result of antimicrobial susceptibility test, most canine strains were considered to be susceptible to 4 drugs, which were commonly used in both human and veterinary clinics, in contrast to human isolates.  相似文献   
63.
64.
65.
This paper focuses on N balance in a paddy field planted with whole crop rice (Oryza sativa cv. Kusahonami). The experiment was conducted with two treatments during two rice-growing seasons: one was fertilized with N (160 kg N ha–1; 16N plot) and the other unfertilized (0N plot); both plots were fertilized with P and K. The N input from precipitation was 15 and 12 kg N ha–1 in 2002 and 2003, respectively. The N input from irrigation water reached as much as 123 and 69 kg N ha–1 in 2002 and 2003, respectively. This was because irrigation water contained higher NO3 concentrations ranging from 4 to 8 mg N l–1. The N uptake by rice plants was the major output: 118 and 240 kg N ha–1 in the 0N and 16N plots in 2002 and 103 and 238 kg N ha–1 in 2003, respectively. N losses by leaching were 4.8–5.3 and 6.5–7.3 kg N ha–1 in 2002 and in 2003, respectively. Laboratory experiments were carried out to estimate the amounts of N2 fixation and denitrification. Amount of N2 fixation was 43 and 0 kg N ha–1 in the 0N and 16N plots, respectively. Denitrification potential was quite high in both the plots, and 90% of the N input through irrigation water was lost through denitrification. Collectively, the total N inputs were relatively large due to irrigation water contaminated with NO3, but N outflow loading, expressed as leaching–(irrigation water + precipitation + fertilizer), showed large negative values, suggesting that the whole crop rice field might serve as a constructed wetland for decreasing N.  相似文献   
66.
The longitudinal changes in fecal steroid hormone concentrations and sexual behavior in 2 mated/pregnant and 3 non-mated female Hokkaido brown bears were investigated during the breeding season. Behavioral estrus (standing) lasted for 14 and 32 days in the mated females and for 25 to 36 days in the non-mated females. In non-mated females, sexual behavior, such as female-female mounting and masturbation, was observed for several days before and after the estrous period. In mated females, mean fecal estradiol-17beta concentrations were higher in the estrous period than in the post-estrous period, while fecal progesterone concentrations were higher in the post-estrous period than in the estrous period. The similar trends of steroid hormone changes were observed in the non-mated females.  相似文献   
67.
68.
69.
AIM: To study the expression and roles of muscarinic cholinergic receptor 3 (M3R) in human small cell lung cancer (SCLC) cells. METHODS: Human SCLC cell lines SBC3 and H82 were cultured in vitro. RT-PCR and Western blotting were used to investigate the expression of M3R. MTT assay and Boyden chamber assay were carried out to determine the roles of cholinergic receptor agonist acetylcholine iodide (ACh) and M3R antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) in the proliferation and migration of SBC3 cells. RESULTS: M3R was expressed in SBC3 and H82 cells. The relative protein expression of M3R normalized with β-actin in SBC3 was 2.65-fold higher than that in H82. ACh stimulated SBC3 cell proliferation in a dose-dependent manner. Treatment with ACh at concentrations of 10-4 and 10-3 mol/L significantly stimulated SBC3 cell growth at 48 h and 72 h (P<0.01). SBC3 cell proliferation induced by ACh was inhibited by 4-DAMP in a dose-dependent manner. Pretreatment of the cells with 10-5 mol/L 4-DAMP suppressed the effect of ACh at 48 h (P<0.05). Pretreatment with 4-DAMP at concentrations of 10-6, 10-7 (P<0.05) and 10-5 mol/L (P<0.01) inhibited the effect of ACh at 72 h. Treatment with 10-5 or 10-6 mol/L 4-DAMP alone inhibited the cell proliferation at 48 h (P<0.01) and the inhibitory effect of 4-DAMP at concentration of 10-5 mol/L was stronger than that of 4-DAMP at concentration of 10-6 mol/L at 72 h. ACh increased the cell migration towards fibronectin (Fn) in a dose-dependent manner and ACh at concentration of 10-4 mol/L enhanced the cell migration by about 3 folds. The cell migration stimulated by 10-4 mol/L ACh was almost completely blocked by pretreatment with 4-DAMP at concentration of 10-6 or 10-5 mol/L (P<0.01). CONCLUSION: M3R is expressed in human SCLC cells. The M3R antagonist inhibits SBC3 cell proliferation and migration.  相似文献   
70.
‘Niigata S3’ is a new strawberry (Fragaria × ananassa Duch.) cultivar that is early flowering and possesses high soluble solid content and good coloration. It was selected from a cross between Kei812 (seed parent) and ‘Asuka-Ruby’ (pollen parent). The first harvest date of ‘Niigata S3’ was December 27, 34 days earlier than ‘Echigohime’ and 9 days earlier than ‘Asuka-Ruby’ (means of 2007 and 2008). The marketable yield of ‘Niigata S3’ was 85% of ‘Echigohime’, 107% of ‘Asuka-Ruby’, while the early yield was 145% of ‘Echigohime’, 85% of ‘Asuka-Ruby’ (based on 2007 and 2008 means). The shape of the fruit is long conical, and its skin color medium-red. The fruit skin hardness of ‘Niigata S3’ was 31.5 g/mm2, which was harder than ‘Echigohime’, and its average soluble solid content was 11.4%, which was higher than the values for ‘Echigohime’ and ‘Asuka-Ruby’ (2008). Furthermore, ‘Niigata S3’ did not bear apical overripe fruit. This new cultivar is adaptable to the climatic conditions of Niigata, as well as other regions that experience low winter temperatures and insolation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号