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   3269篇
  免费   373篇
  国内免费   193篇
林业   51篇
农学   86篇
基础科学   8篇
  74篇
综合类   993篇
农作物   77篇
水产渔业   407篇
畜牧兽医   2018篇
园艺   102篇
植物保护   19篇
  2024年   3篇
  2023年   44篇
  2022年   70篇
  2021年   130篇
  2020年   149篇
  2019年   196篇
  2018年   109篇
  2017年   180篇
  2016年   202篇
  2015年   162篇
  2014年   170篇
  2013年   185篇
  2012年   211篇
  2011年   225篇
  2010年   161篇
  2009年   185篇
  2008年   140篇
  2007年   157篇
  2006年   137篇
  2005年   132篇
  2004年   128篇
  2003年   79篇
  2002年   68篇
  2001年   66篇
  2000年   60篇
  1999年   43篇
  1998年   56篇
  1997年   40篇
  1996年   31篇
  1995年   47篇
  1994年   42篇
  1993年   28篇
  1992年   30篇
  1991年   26篇
  1990年   26篇
  1989年   36篇
  1988年   11篇
  1987年   14篇
  1986年   7篇
  1985年   3篇
  1984年   6篇
  1982年   4篇
  1980年   8篇
  1979年   6篇
  1978年   3篇
  1977年   2篇
  1975年   2篇
  1974年   4篇
  1973年   4篇
  1956年   3篇
排序方式: 共有3835条查询结果,搜索用时 46 毫秒
91.
The bleeding efficiency of anaesthetized and exhausted Atlantic salmon was studied. Unbled fish were used as control groups for both treatments. Several analytical methods (computer vision, Minolta Chroma Meter, transflectance spectroscopy, haemoglobin iron and visual assessment of smoked fillets) were used to evaluate colour or residual blood contents of pre‐rigor and smoked fillets. In all cases, the amount of residual blood in the fillets was modest and blood was not considered a quality problem in terms of fillet appearance. Perimortem stress did not affect residual blood contents of pre‐rigor fillets. Only salting and smoking had a significant effect on filet colour. The low levels of residual blood was partly attributed to filleting shortly after killing allowing washing before the blood had time to coagulate. In addition, a computer vision method was developed for automated blood inspection of the body cavity after gutting and washing. A classifier (‘no blood’ or ‘blood present’) based on linear discriminant analysis was tested and the classification accuracy was over 90% as evaluated with the leave‐one‐out method.  相似文献   
92.
93.
本文对人工诱导的大黄鱼三倍体与正常数大黄鱼二倍体的血液血细胞常值测定,并对血液生理指标进行比较研究。结果表明:体长25.2~29.2cm,体重180.0~331.0g的二倍体大黄鱼,红细胞平均值为2.33±0.12(×1012个/L);白细胞平均值为23.65±2.45(×109个/L);血栓细胞平均值为42.50±7.14(×109个/L)。体长25.2~27.5cm,体重224.0~281.0g的三倍体大黄鱼,红细胞平均值为1.22±0.18(×1012个/L);白细胞平均值为31.19±3.52(×109个/L);血栓细胞平均值为29.25±5.91(×109个/L)。分析比较大黄鱼二倍体、三倍体各项血液生理指标,除血红蛋白无显著性差异外,其余各项血液生理指标有显著性差异。  相似文献   
94.
为探讨以女贞子、枸杞子、穿心莲、大青叶等多味中药组成的"女贞枸杞散"对断奶仔猪腹泻的预防效果和对外周血各类白细胞数量的影响。根据体重相近、公母各半的原则选用80头体重为10kg左右的"杜长大"三元杂交断奶仔猪,随机分4组,分别为试验Ⅰ组(日粮中加0.4%"女贞枸杞散"),Ⅱ组(添加0.6%),Ⅲ组(添加0.8%)和对照组(普通日粮)。详细记录仔猪腹泻情况,计算腹泻率、腹泻频率、腹泻指数等。试验结束后采血,测定各类白细胞数量,结果表明,"女贞枸杞散"能有效地降低断奶仔猪的腹泻率,改善仔猪的生长性能,促进血液中的白细胞尤其是淋巴细胞的的生成,提高机体免疫力。  相似文献   
95.
杂交鳢(乌鳢♂×斑鳢♀)及其亲本血液指标的比较分析   总被引:3,自引:0,他引:3  
本研究采用血细胞分析仪、流式细胞仪和血涂片制作方法,对杂交鳢及其亲本血液指标进行了比较分析。结果显示,杂交鳢(Channa argus♂×C.maculata♀)与其亲本相比,表现出明显杂种优势:在血液红细胞数目、白细胞数目、血红蛋白含量和血细胞比容上,杂交鳢都比亲本高,差异显著(P<0.05);在红细胞体积上,杂交鳢均比亲本小,差异显著(P<0.05);杂交鳢及其亲本血液中都含有较少比例的DNA合成期(S期)细胞,但彼此差异不显著(P>0.05)。  相似文献   
96.
97.
This experiment was conducted to study the effect of different dietary nutrition levels on fattening effect of Holstein bulls.48 4-month-old Holstein bulls with an average body weight of 128 kg were allocated into two groups,group Ⅰ was fed a low nutrition level diet,group Ⅱ was fed a high nutrition level diet.Each group had 24 Holstein bulls.The pre-test period lasted for 7 days and the trial period lasted for 245 days.The results showed that compared with group Ⅰ,the ADG in group Ⅱ was significantly increased by 6.36% (P<0.01),while the F/G in group Ⅱ was decreased by 6.55%.With the increasing of dietary nutrition levels,the apparent digestibility of CP,EE,NDF,ADF,Ca and P were rising,but there was no significant differences between two groups (P>0.05).Compared with group Ⅰ,the serum GLU,AST,ALT and GH contents in group Ⅱ were increased by 12.52%,12.85%,9.68% and 13.24% (P<0.05),respectively,while the serum BUN content in group Ⅱ was decreased by 10.98% (P<0.05).Compared with group Ⅰ,the feeding profits of group Ⅱ increased by 1.37 yuan/(head·day),the total economic benefit of group Ⅱ increased by 335.65 yuan/head.In conclusion,the improvement of dietary nutrition levels could improve the fattening performance and the economic benefit of Holstein bulls.  相似文献   
98.
This study was designed to compare the blood physiological and biochemical parameters between plateau Juema minipigs and plain Bama minipigs,and provide a theoretical basis for Juema minipigs served as experimental animals in the future.The blood samples of Juema minipigs were taken in Gannan,and the blood samples of the Bama minipigs were taken in Xi'an,24 blood physiological and biochemical parameters were tested using an automatic analyzer of blood cells and biochemistry.Between the plateau Juema minipigs and Bama minipigs,there were significant differences in PLT,RDW-CV and RDW-SD (P< 0.05) and extremely significant differences in RBC,HGB,HCT,MCH,MCMH,GGT,GLU and CRE (P< 0.01).The plateau Juema minipig had an altitude acclimatization,so it was better than Bama minipig in plateau medical science.  相似文献   
99.
以中温碱抽提玉米秸秆渣为研究对象,考察了不同外源添加物对酶解工艺的辅助作用和影响机制。研究结果表明,采用中温碱抽提玉米秸秆可以脱除50.02%木质素,添加PEG6000辅助水解作用明显。当纤维素底物质量浓度40 g/L,酶用量在纤维素酶(Celluclast 1.5 L)15 FPIU/g和纤维二糖酶(Novozyme 188)30 BU/g水解48 h,添加PEG6000 4.0 g/L葡萄糖得率73.51%,酶解率84.51%,较未添加样品上升幅度分别达到26.2%和27.1%。添加PEG不仅可以减轻酶蛋白和碱抽提玉米秸秆渣的吸附,提高酶在液相中的分配,对纤维素酶活力和稳定性也具有显著的促进作用。PEG存在下纤维素酶1.5 L的滤纸酶活提高34.1%,稳定性提高57.3%。  相似文献   
100.
A 6‐month trial was conducted to evaluate the effects of dietary cottonseed meal (CSM) and free gossypol (FG) on allogynogenetic silver crucian carp, Carassius auratus gibelio♀ × Cyprinus carpio♂ with 4 replicates of each treatment. Isonitrogenous and isocaloric diets were formulated with the 0 g kg?1 (control), 200 g kg?1, 400 g kg?1, and 560 g kg?1 CSM. Diets with FG were made by supplementing batches of control diet with 214 mg kg?1, 428 mg kg?1, and 642 mg kg?1. Weight gain, specific growth rate, and protein efficiency ratio increased significantly up to an inclusion level of CSM of 400 g kg?1 in the diet, with a significant decrease in food conversion ratio. Further increase in CSM to 560 g kg?1 did not cause further changes in fish performance. Free gossypol did not affect fish performance significantly at any inclusion level. Neither CSM nor FG caused significant effects in any of the other evaluated parameters such as whole body composition, haemoglobin concentration, activities of serum lysozyme, superoxide dismutase, alanine aminotransferase and aspartate aminotransferase, and histology of hepatic tissues and midgut. Our results suggested that crucian carp can tolerate at least 642 mg kg?1 FG and that it is safe to including 400 g kg?1 CSM in crucian carp feed.  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