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   4632篇
  免费   236篇
  国内免费   2篇
林业   200篇
农学   234篇
基础科学   13篇
  820篇
综合类   361篇
农作物   697篇
水产渔业   403篇
畜牧兽医   1831篇
园艺   69篇
植物保护   242篇
  2023年   29篇
  2022年   89篇
  2021年   163篇
  2020年   98篇
  2019年   123篇
  2018年   146篇
  2017年   135篇
  2016年   148篇
  2015年   153篇
  2014年   207篇
  2013年   271篇
  2012年   331篇
  2011年   388篇
  2010年   222篇
  2009年   206篇
  2008年   298篇
  2007年   299篇
  2006年   265篇
  2005年   225篇
  2004年   217篇
  2003年   187篇
  2002年   140篇
  2001年   134篇
  2000年   94篇
  1999年   58篇
  1998年   28篇
  1997年   18篇
  1996年   9篇
  1995年   9篇
  1994年   3篇
  1993年   8篇
  1992年   16篇
  1991年   16篇
  1990年   23篇
  1989年   17篇
  1988年   8篇
  1987年   9篇
  1986年   7篇
  1985年   5篇
  1984年   4篇
  1983年   6篇
  1980年   5篇
  1978年   11篇
  1975年   3篇
  1974年   5篇
  1972年   5篇
  1971年   3篇
  1970年   4篇
  1969年   4篇
  1968年   4篇
排序方式: 共有4870条查询结果,搜索用时 15 毫秒
21.
22.
A 3-year-old Texas Longhorn steer had a long history of progressive swelling of the soft tissues of the jaw and neck. At necropsy, multifocal to coalescing dermal and subcutaneous pyogranulomas were surrounded by fibrous tissue. Microscopically, the pyogranulomas contained aggregates of gram-negative coccobacilli surrounded by Splendore-Hoeppli material and were separated by bands of fibrovascular tissue (botryomycosis). Phylogenetic analysis of multilocus sequence-typing data revealed that the bacteria recovered in pure culture from swabs of submandibular tissue were most closely related to Bibersteinia [Pasteurella] trehalosi. The bacterial colonies were immunohistochemically reactive with a rabbit polyclonal anti-Pasteurella class C acid phosphatase antibody. Botryomycosis is a pyogranulomatous inflammation caused by a variety of nonbranching, nonfilamentous bacteria that elicit the formation of Splendore-Hoeppli material. This case of botryomycosis is unique for its association with Bibersteinia trehalosi.  相似文献   
23.
24.
25.
We analyzed alcoholic extracts of herbs possessing anti-neosporal activity against Neospora (N.) caninum. To identify the chemical components of Sophora (S.) flavescens and Torilis (T.) japonica associated with anti-neosporal activity, specific fractions were isolated by high-performance liquid chromatography (HPLC). In vitro activity of the fractions against N. caninum was then assessed. Gas chromatography/mass spectrometry (GC/MS) was used to identify and quantify specific anti-neosporal molecules in the herbal extracts. Almost all HPLC fractions of S. flavescens and T. japonica had higher levels of anti-neosporal activity compared to the not treated control. Active constituents of the extracts were sophoridane, furosardonin A, and tetraisopropylidene-cyclobutane in S. flavescens; 5,17-β-dihydroxy-de-A-estra-5,7,9,14-tetraene, furanodiene, and 9,12-octadecadienoic acid (Z,Z)-(CAS,1) in T. japonica.  相似文献   
26.
Renal length, height, width, resistive index (RI), size of cortex, and medulla were determined by renal ultrasonography in 50 healthy Korean domestic short-hair cats. In the sagittal plane, the renal length was 3.83 ± 0.51 cm (mean ± SD) in the left kidney and 3.96 ± 0.48 cm in the right kidney, whereas the renal height was 2.42 ± 0.27 cm in the left kidney and 2.36 ± 0.28 cm in the right kidney. In the transverse plane, the renal height was 2.42 ± 0.28 cm in the left kidney and 2.38 ± 0.27 cm in the right kidney, whereas the renal width was: 2.65 ± 0.35 cm in the left kidney and 2.63 ± 0.31 cm in the right kidney. In the dorsal plane, the renal length was 3.84 ± 0.53 cm in the left kidney and 3.97 ± 0.54 cm in the right kidney, whereas the renal width was 2.65 ± 0.34 cm in the left kidney and 2.66 ± 0.33 cm in the right kidney. There were no significant differences (p > 0.05) among the same structure sizes measured in different planes. In the sagittal plane, the size of the renal cortex was 0.47 ± 0.08 cm in the left kidney and 0.47 ± 0.08 cm in the right kidney, whereas of the size of the renal medulla was 0.55 ± 0.30 cm in the left kidney and 0.50 ± 0.07 cm in the right kidney. RI evaluated by pulsed wave Doppler sonography was 0.52 ± 0.05 in the left kidney and 0.55 ± 0.05 in the right kidney. The actual renal dimensions determined by gross examination were not statistically different from those determined by ultrasonography. Furthermore the renal dimensions and RI were statistically correlated to the body weight of cats.  相似文献   
27.
28.
To evaluate potential of an auxotrophic Edwardsiella tarda mutant (Δalr Δasd E. tarda) as a delivery vehicle for DNA vaccine in fish, olive flounder (Paralichthys olivaceus) were immunized with the E. tarda mutant harboring plasmids (pG02-ASD-CMV-eGFP) for eukaryotic expression of the enhanced green fluorescent protein (eGFP) gene through either intraperitoneal (i.p.) or oral route, and the expression of eGFP in the internal organs and generation of antibody against eGFP in fish were analyzed. In fish i.p. injected with 2×10(7)CFU/fish of Δalr Δasd E. tarda harboring pG02-ASD-CMV-eGFP, expression of eGFP was detected in liver, kidney, and spleen from 1 day to 28 days post-injection. In fish orally administered with 1×10(9)CFU/fish of the bacteria, the eGFP band was detected in liver, kidney, and spleen from 1 day to 14 days post-administration, whereas, in intestine, the band was detected only at 1 day post-administration. Either oral or i.p. immunization of olive flounder with recombinant E. tarda that carried eGFP-expressing eukaryotic plasmids was successful to induce humoral adaptive immunity against not only E. tarda that was used as a delivery vehicle but also eGFP that was used as the reporter protein of DNA vaccine, suggesting attenuated E. tarda-vectored DNA vaccine has a potential to be used as a combined vaccine against infectious diseases in fish.  相似文献   
29.
30.
An experiment involving 560 crossbred pigs (28 replications of 4 to 6 pigs per pen) was conducted at 9 research stations to assess the effects of dietary concentrations of corn distillers dried grains with solubles (DDGS) on pig performance and belly firmness. Fortified corn-soybean meal diets containing 0, 15, 30, or 45% DDGS were fed in 3 phases from 33 to 121 kg of BW. A common source of DDGS containing 90.1% DM, 26.3% CP, 0.96% Lys, 0.18% Trp, 9.4% crude fat, 34.6% NDF, 0.03% Ca, and 0.86% P was used at each station. Diets were formulated to contain 0.83, 0.70, and 0.58% standardized ileal digestible (SID) Lys during the 3 phases with diets changed at 60 and 91 kg of BW, respectively. The DDGS replaced corn and soybean meal, and up to 0.172% Lys and 0.041% Trp were added to maintain constant SID concentrations of Lys and Trp in each phase. At each station, 2 pigs from each pen in 2 replications were killed and a midline backfat core was obtained for fatty acid analysis and iodine value. In most instances, there were differences among stations (P < 0.01), but the station × treatment interactions were few. Body weight gain was linearly reduced in pigs fed the greater amounts of DDGS (0 to 45%) during phase I (950, 964, 921, and 920 g/d; P < 0.01) and over the entire experimental period (944, 953, 924, and 915 g/d; P = 0.03), but ADFI (2.73, 2.76, 2.68, and 2.70 kg) and G:F (347, 347, 345, and 341 g/kg) were not affected (P = 0.15 and P = 0.33, respectively) during the entire test. Backfat depth was reduced (linear, P < 0.02) by increasing amounts of DDGS (22.5, 22.7, 21.4, and 21.6 mm), but LM area (47.4, 47.4, 46.1, and 45.4 cm(2)) was not affected (P = 0.16) by treatments. Estimated carcass fat-free lean was 51.9, 52.2, 52.4, and 52.1% for 0 to 45% DDGS, respectively (linear, P = 0.06). Flex measures obtained at 6 stations indicated less firm bellies as dietary DDGS increased (lateral flex: 11.9, 8.6, 8.4, and 6.6 cm; linear, P < 0.001; vertical flex: 26.1, 27.4, 28.2, and 28.7 cm; linear, P < 0.003). Saturated and monounsaturated fatty acid concentrations in subcutaneous fat decreased linearly (P < 0.001) and PUFA concentrations increased linearly (P < 0.001) with increasing DDGS in the diet. Iodine values in inner (61.1, 68.2, 74.7, and 82.2) and outer (67.9, 73.6, 79.6, and 85.8) backfat increased linearly (P < 0.001) as DDGS in the diet increased. In this study, feeding diets with 30 or 45% DDGS did not have major effects on growth performance, but resulted in softer bellies. Regression analysis indicated that iodine values increased 4.3 units for every 10 percentage unit inclusion of DDGS in the diet.  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