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   619篇
  免费   35篇
  国内免费   33篇
林业   30篇
农学   14篇
基础科学   15篇
  47篇
综合类   177篇
农作物   24篇
水产渔业   26篇
畜牧兽医   297篇
园艺   22篇
植物保护   35篇
  2024年   5篇
  2023年   14篇
  2022年   12篇
  2021年   14篇
  2020年   24篇
  2019年   23篇
  2018年   15篇
  2017年   31篇
  2016年   10篇
  2015年   22篇
  2014年   32篇
  2013年   34篇
  2012年   48篇
  2011年   32篇
  2010年   45篇
  2009年   28篇
  2008年   38篇
  2007年   17篇
  2006年   20篇
  2005年   19篇
  2004年   14篇
  2003年   12篇
  2002年   12篇
  2001年   18篇
  2000年   16篇
  1999年   9篇
  1998年   7篇
  1997年   6篇
  1996年   2篇
  1995年   5篇
  1994年   2篇
  1993年   7篇
  1992年   3篇
  1991年   8篇
  1990年   7篇
  1989年   6篇
  1988年   6篇
  1986年   6篇
  1985年   3篇
  1984年   5篇
  1983年   5篇
  1976年   2篇
  1975年   2篇
  1973年   2篇
  1966年   2篇
  1947年   2篇
  1912年   4篇
  1902年   2篇
  1901年   3篇
  1900年   1篇
排序方式: 共有687条查询结果,搜索用时 15 毫秒
71.
The impact of TCM‐199 supplemented with different proteins and heterologous hormones on the in vitro maturation (IVM) rate of bitch oocytes was evaluated by nuclear staining under fluorescence microscopy. Oocytes were recovered by slicing of ovaries from bitches presented at various stages of oestrous cycle to ovariohysterectomy. The basic culture medium was TCM‐199 supplemented with 25 mM Hepes/l, with 10% heat‐inactivated oestrous cow serum (ECS), 50 μg/ml gentamicin, 2.2 mg/ml sodium bicarbonate and 22‐μg/ml pyruvic acid, 1.0‐μg/ml oestradiol (E 8875; Sigma), 0.5‐μg/ml follicle‐stimulating hormone (FSH) (Folltropin‐V; Vetrepharm Inc., Ontario, Canada) and 0.03 IU/ml human gonadotropin (hCG) (Profasi HP; Serono, Aubonne, Switzerland). Oocytes were distributed randomly between basic culture medium (control) and the corresponding experimental treatment. Hormone treatments were: oocytes cultured in; (1) medium without FSH, (2) control medium supplemented with 20 μg/ml oestradiol, or (3) medium supplemented with 1 μg/ml human somatotropin (hST; Humatrope, Lilly, Saint Cloud, France). The second experiment consisted of oocytes cultured in medium supplemented with 0.4% (w/v) bovine serum albumin (BSA, fraction V; Gibco Grand Island, NY, USA) instead of ECS, or oocytes cultured in medium with 10% inactivated oestrous bitch serum (EBS) instead of ECS. Oocytes were cultured in 100 μl droplets (up to 25 oocytes per drop) under mineral oil at 37°C in a 100% humidified atmosphere containing 5% CO2 in air. After 72 h of IVM, the highest rates (p < 0.05) of meiotic resumption were achieved with the 0.4% BSA supplementation. A positive influence on the metaphase II (MII) acquisition rate was observed with hST supplement. Oocytes cultured with 10% EBS supplementation did not develop to the MII stage. The results in this study show that the protein and hormone supplements to TCM‐199 culture medium tested did not promote the final steps of IVM of bitch oocytes.  相似文献   
72.
Spraying programmes for apple scab and mildew control sometimes had residual effects for one or even two years. Thus, benomyl (0.025% a.i.) and pyridinitril (0.035% a.i.) drastically reduced the subsequent incidence of cankers caused by Nectria galligena on young wood. Apple scab fruit infection, caused by Venturia inaequalis, was also less on trees on which benomyl had been used in the previous season. In the bark of such trees, toxic residues equivalent to 1 to 4 μg benomyl/g fresh wt. were detected by bioassay 7 months after spraying.  相似文献   
73.
The ability of the SAV 6 high-frequency jet ventilator to effectively ventilate three anesthetized, paralyzed cats (3.2–4.2 kg), two small dogs (7.2 and 10.0 kg), six medium-sized dogs (20.5–25.0 kg), and three large dogs (36.0–43.0 kg) via a 14-gauge (dogs) or a 16-gauge (cats) catheter placed percutaneously into the trachea via the cricothyroid membrane or into a preplaced endotracheal tube was evaluated. The lowest driving pressure within the range of 0.25 to 2.0 kg/cm2 (1 kg/cm2= 14.2 psi) and the highest cycle rate within the range of 60 to 240 per minute that would generate a PaCO2 of 30 ± 3 mm Hg were determined.
All animals could be ventilated to a PaC02 of 30 ± 3 mm Hg by the endotracheal tube and transtracheal route, except the largest dogs, which couid be ventilated to an average PaC02 of 36 mm Hg by the transtracheal route. The transtracheal route consistently required higher driving pressures and lower cycle rates than did the endotracheal tube route. Cats could be ventilated with a driving pressure of 0.25 kg/cm2; small dogs could be ventilated with 0.5 to 1.0 kg/cm2; medium-sized dogs with 1.0 to 1.5 kg/cm2; and large dogs with 1.5 to 2.0 kg/cm2.
The SAV 6 high-frequency jet ventilator can effectively ventilate cats and dogs (7.2–43.0 kg) via a transtracheal catheter and an endotracheal tube.  相似文献   
74.
A 6-month-old stunted female Doberman Pinscher was found to have a 77,X0 chromosomal complement. The ovaries were small, consisting primarily of interstitial-type cells and solid epithelial cords. The dam, sire, and a male littermate had normal karyotypes.  相似文献   
75.
A standardized investigation was conducted to compare the biophysical properties of hyaluronate products used in the treatment of joint dysfunction in horses. Results showed that two of the five products, Hyvisc® and Hylartin®V, contained higher-weight molecular hyaluronate (greater than 1.5×106). Other investigations have shown that higher molecular weight hyaluronate is effective in providing physical resistance to shear, in stimulating endogenous hyaluronate synthesis, and in inhibiting excess cell proliferation which may be associated with synovial pannus formation. It is suggested that the therapeutic benefits of hyaluronate products may be dependent on the molecular size of the hyaluronate molecules. Higher molecular weight hyaluronate products would be expected to be more effective than lower molecular hyaluronate products in providing therapeutic benefits.  相似文献   
76.
This new research discovery indicates that the energy requirement of horses for maintenance and performance must take into consideration their body condition, as well as the environmental temperature. Performance horses, especially in the hot months, should not be too fleshy. During the hotter and more humid times of the year, it is also advisable for performance to be accomplished in the cooler parts of the day especially early morning or late evening. This is more critical with horses that are in a fleshy condition.Horses in fleshy condition will consume more feed. This may help explain why halter horses with considerable body condition eat large amounts of grain. They need more energy to maintain their body weight and have an extra maintenance requirement for being “fleshy.”Adding fat (10%) to the ration of performance horses will decrease feed intake and therefore feed cost. It will be metabolically beneficial to all horses in hot/humid weather but especially to those that may be over-conditioned.  相似文献   
77.
OBJECTIVE: (1) To determine whether an extracapsular patellar ligament/fascia lata graft would provide stability in the cranial cruciate ligament (CrCL)-deficient stifle comparable with that of the intact stifle. (2) To determine if different tibial anchor points would enhance stability of the CrCLdeficient stifle when compared with the standard fabellar-tibial suture (FTS) placement. STUDY DESIGN: Experimental. ANIMALS: Twenty-eight canine cadaver hind limbs. METHODS: Stifles were mounted in a jig and tested between loads of -65 and 80 N. After testing the intact CrCL, 4 stabilization techniques were tested after CrCL transection: lateral graft technique (LGT) and 3 FTS with different tibial anchor points. RESULTS: There were no significant differences in displacement between the LGT and standard FTS, between the LGT and the intact CrCL, or between the FTS and the intact CrCL, in either the Securos or the Screw-washer experiments. Stiffness of the intact CrCL was significantly greater than that of any stabilization technique and the cut CrCL. The standard FTS showed the least displacement of all suture stabilization techniques. Differences in stiffness were not significant between the suture stabilization techniques. CONCLUSIONS: Securely anchored, the LGT results in a reduction in drawer motion similar to that of the intact CrCL and the standard FTS. Altering the tibial anchor point for the FTS does not improve stiffness or enhance stabilization of the CrCL-deficient stifle. CLINICAL RELEVANCE: The LGT could be used for the treatment of CrCL ruptures in the dog. A clinical study is recommended.  相似文献   
78.
79.
80.
【目的】建立羊踯躅嫩叶离体培养及植株高效再生体系。【方法】以羊踯躅新生嫩叶为外植体,筛选嫩叶愈伤组织诱导、再分化及生根培养基,并以再生植株茎节为试材,建立高效植株再生体系。【结果】最适合羊踯躅嫩叶愈伤组织诱导的培养基为1/2 DR+2.40 mg/L 2ip+0.80 mg/L NAA,诱导率为99.5%;愈伤组织再分化的最佳培养基为1/2 DR+2.90 mg/L 2ip+0.01 mg/L NAA+1.75 mg/L KT,分化率为99.7%;适宜生根的培养基为1/4 DR+0.06 mg/L ZT+0.02 mg/L NAA,生根率达99.0%。利用再生植株茎节的快繁结果表明,在28 d的培养周期内,每节段平均增殖达5倍以上。【结论】成功建立了羊踯躅嫩叶愈伤组织诱导、再分化芽苗和植株高效再生体系,可以满足羊踯躅工厂化育苗的需要。  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