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   1012篇
  免费   45篇
  国内免费   7篇
林业   106篇
农学   31篇
基础科学   3篇
  135篇
综合类   45篇
农作物   24篇
水产渔业   131篇
畜牧兽医   515篇
园艺   12篇
植物保护   62篇
  2024年   1篇
  2023年   3篇
  2022年   13篇
  2021年   29篇
  2020年   14篇
  2019年   14篇
  2018年   18篇
  2017年   24篇
  2016年   24篇
  2015年   44篇
  2014年   36篇
  2013年   59篇
  2012年   60篇
  2011年   58篇
  2010年   43篇
  2009年   38篇
  2008年   79篇
  2007年   85篇
  2006年   64篇
  2005年   66篇
  2004年   49篇
  2003年   60篇
  2002年   47篇
  2001年   23篇
  2000年   14篇
  1999年   5篇
  1998年   13篇
  1997年   5篇
  1996年   3篇
  1995年   1篇
  1994年   3篇
  1993年   2篇
  1992年   4篇
  1991年   3篇
  1990年   10篇
  1989年   5篇
  1988年   18篇
  1987年   6篇
  1986年   9篇
  1985年   6篇
  1984年   1篇
  1980年   3篇
  1979年   1篇
  1977年   1篇
排序方式: 共有1064条查询结果,搜索用时 15 毫秒
101.
102.
Several glutathione S-transferases which catalyze the conjugation of reduced glutathione with organophosphorus triesters were separated from fat bodies of adult female American cockroaches, Periplaneta americana (L.). Two transferases (I, V) were active on diazinon and three transferases (II, III, IV) were active on methyl parathion. The transferase (I) active on the pyrimidinyl moiety of diazinon was distinguishable from the other transferases on the O-methyl portion of methyl parathion, as shown by chromatographic properties, and additionally it was almost inactive or less active on 3,4-dichloronitrobenzene, methyl iodide, p-nitrobenzyl chloride, trans-cinnamaldehyde, and 1,2-epoxy-3-(p-nitrophenoxy)propane. Transferase II had high activities with “aryl” and “aralkyl” compounds, transferase III with “epoxide” and “alkene,” and transferase IV with “alkyl,” “aryl,” and “aralkyl” compounds. This indicated that the transferases had overlapping substrate specificities. The molecular weight was 35,000–37,000 for both of the enzymes active on methyl parathion and diazinon. The pH optima with methyl parathion and diazinon were about 8.5 and 6.5, respectively. At a glutathione concentration of 5 mM, Michaelis constants were 0.28 and 0.13 mM for methyl parathion and diazinon, respectively.  相似文献   
103.
Total serum creatine kinase (CK) and its isozyme activities were determined in dogs with dirofilariasis. Before heartworm removal, total CK and isozyme activities in dogs of the mild group were not different from those in dogs of the heartworm-free group. BB activity was higher in dogs of the hemoptysis group. Dogs of the ascites group displayed a mild increase in MM activity. In dogs of the caval syndrome (CS) group, total CK and MM activities were highest among the heartworm-free and heartworm-infected dogs, and MM isozyme accounted for most (75%) of total CK activity. MB and BB activities were also higher. However, there were no significant differences in CK activities between the surviving and non-surviving cases. In dogs with pulmonary heartworm disease (mild and ascites groups), MM activity correlated significantly with the number of heartworms (r = 0.45), hematocrit value (Ht, r = -0.40), serum alanine aminotransferase (ALT, r = 0.42) and lactate dehydrogenase (LDH, r = 0.46) activities, mean pulmonary arterial pressure (r = 0.64) and total pulmonary resistance (r = 0.50). In dogs with CS, MM activity did not correlate with any parameter, but BB activity correlated with the number of heartworms at the right atrium (r = 0.61), Ht (r = -0.53), ALT (r = 0.80), LDH (r = 0.73) and serum urea nitrogen (r = 0.47). At 1 week after heartworm removal, BB and MM activity decreased in dogs of the hemoptysis and ascites groups, respectively. In dogs of the CS group, total CK and MM isozyme activities decreased markedly (P less than 0.01) regardless of their prognosis.  相似文献   
104.
Cardiopulmonary values were determined in dogs with an artificial model of heartworm caval syndrome, which was produced by insertion of heartworm-like silicone tubes into the tricuspid valve orifice and right atrium. Fifteen to 25 tubes with some knots were inserted in 6 dogs (knot group), and 7 to 11 tubes (small-number group) or 29 to 37 tubes (large-number group) without a knot in 3 dogs, respectively. After tube insertion, angiographic contrast medium infused into the right ventricle regurgitated to the right atrium in all cases, and the regurgitation was the most severe in the large-number group. On electrocardiographic findings, the atrial and/or ventricular premature beat developed. The height of a- and v-wave of right atrial pressure curves elevated in all groups. The elevation in v-wave was obvious in the large-number group. The pulmonary arterial pressure tended to fall or to elevate slightly, and total pulmonary resistance increased in all groups. The right cardiac output decreased significantly in all cases. The right heart hemodynamics of the model might resemble those in spontaneous cases without disturbed pulmonary circulation.  相似文献   
105.
106.
107.
108.
Staphylococci were isolated from the external auditory meatus in 14 (48.3%) of 29 dogs affected with otitis externa (OE dogs) and 28 (68.3%) of 41 dogs without OE (non-OE dogs). Twenty-two OE isolates were identified as belonging to 12 species, and 42 non-OE isolates were identified as belonging to 13 species. The predominant species found in both OE and non-OE isolates were S. intermedius, and S. epidermidis. Thirty-eight (59.4%) of 64 isolates were resistant to one or more of the 17 antimicrobial agents tested. Resistance to PCG and ABPC was most frequent. S. schleiferi subsp. coagulans, a recent etiologic agent of canine OE, was isolated from OE and non-OE dogs. All of the 5 S. schleiferi subsp. coagulans isolates showed typical characteristics. No clear difference in the extracellular enzyme or toxin profiles, nor in the PFGE patterns, was demonstrated between the OE and non-OE isolates of S. schleiferi subsp. coagulans. A new PCR primer set specific for 16S rDNA was designed to identify strains of S. schleiferi subsp. coagulans. The amplified fragment was detected in all of the 5 isolates as well as the type strain GA 211 (=JCM 7470) and a reference strain GA 11, but was not detected in any strains of the related species, S. aureus, S. intermedius and S. hyicus. The PCR may allow a simple, rapid and precise identification of S. schleiferi subsp. coagulans, in addition to the standard tube test for free coagulase.  相似文献   
109.
Two experiments were conducted to compare the effect of estrus induction by controlled internal drug release (CIDR) and intravaginal cream containing 500 mg progesterone (P cream) in ewes during the non-breeding season. In the first experiment, twenty-four ewes were randomly grouped for two treatments with the different intravaginal devices for 12 days: Group A was the CIDR group and Group B was the P cream group. Blood was collected from all treated ewes, and progesterone (P(4)), estradiol 17-beta (E(2)) and luteinizing hormone (LH) concentrations were measured by enzyme immunoassay. In the second experiment, the conception rates from natural mating, estrus-detected AI (inseminated 12 h after estrus detection), or fixed-time AI (inseminated 42 h after removal of an intravaginal device) in 127 ewes treated with CIDR or P cream were compared. In Experiment 1, the rate of estrus induction and the time of estrus onset after device removal were 91.7% and 36.3 +/- 15.7 h in Group A, and 100% and 35.0 +/- 12.6 h in Group B, respectively. There were no significant differences between the devices. The mean plasma P(4) concentration in Group B was significantly (P < 0.01) lower than Group A between day -9 and day -1 (Day 0: the day of device removal). However, no significant differences were found in the mean E(2) concentrations of the two groups after treatment. The mean time of estrus onset in ewes with an observed LH surge and the time of LH surge after treatment were 23.3 +/- 8.7 h and 30.3 +/- 5.0 h for Group A and 27.6 +/- 6.5 and 26.3 +/- 8.0 h for Group B, respectively, and there were no significant differences. However, a significant difference (P < 0.05) was found in the mean time from the time of estrus onset to LH surge between Group A (6.4 +/- 6.7 h) and Group B (-1.3 +/- 4.1 h). In Experiment 2, the conception rates for natural mating, estrus-detected AI, and fixed-time AI were 55.0, 29.4, and 25.0% for Group A and 40.7, 25.0, and 42.1% for Group B, respectively, and there were no significant differences. These results suggest that the effect of induction of estrus and ovulation and the rate of conception after treatment were comparable to CIDR even though the plasma P(4) concentration of the P cream method tended to be low during the insertion period.  相似文献   
110.
A survey on the presence of Cryptosporidium oocyst and Giardia cyst in livestock drinking water as well as the urban tap water throughout Taiwan was carried out. Water examination for the presence of the protozoa was conducted by filtering through a PTFE membrane followed by immunomagnetic separation (IMS) and immunostaining the sediment with commercially available monoclonal antibody against Cryptosporidium and Giardia. Of the 55 different water samples from various sources examined, 2 were found to contain both of Cryptosporidium oocyst and Giardia cyst, 1 was found to contain Cryptosporidium oocyst only. These protozoa-positive water samples, originating from underground well and from the mountain spring, were also used as drinking water for livestock. However, no Cryptosporidium oocyst was found in the city tap water. This is the first report of Cryptosporidium oocyst and Giardia cyst being found in the drinking water for livestock.  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