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   170篇
  免费   7篇
  国内免费   1篇
林业   4篇
农学   5篇
  63篇
综合类   18篇
农作物   16篇
水产渔业   10篇
畜牧兽医   46篇
园艺   1篇
植物保护   15篇
  2021年   3篇
  2020年   1篇
  2019年   2篇
  2018年   4篇
  2017年   2篇
  2016年   8篇
  2015年   2篇
  2014年   3篇
  2013年   8篇
  2012年   14篇
  2011年   19篇
  2010年   13篇
  2009年   16篇
  2008年   7篇
  2007年   10篇
  2006年   8篇
  2005年   7篇
  2004年   10篇
  2003年   2篇
  2002年   2篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1997年   4篇
  1996年   2篇
  1993年   1篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1987年   1篇
  1982年   1篇
  1981年   1篇
  1979年   2篇
  1975年   2篇
  1974年   1篇
  1969年   2篇
  1965年   2篇
  1963年   2篇
  1945年   1篇
排序方式: 共有178条查询结果,搜索用时 15 毫秒
1.
Respiratory distress is a very common presenting complaint in emergency practice. It is essential that the clinician rapidly determine the underlying cause of the clinical signs using physical examination findings and nonstressful diagnostic tests. Oxygen therapy will often stabilize a patient, allowing for a more complete physical examination and diagnostics, including thoracocentesis, thoracic radiographs, and blood collection for laboratory analysis. The disease processes that cause respiratory distress can be grouped according to anatomic location: the airways, pulmonary parenchyma, pleural space, or thoracic wall. The choice of diagnostic and therapeutic techniques will be dependent on the suspected anatomic origin of disease. Techniques useful in diagnosing airway disorders include oral examination, cervical and thoracic radiographs, fluoroscopy, and bronchoscopy. Therapeutic techniques include intubation and tracheostomy. For parenchymal disease, thoracic radiographs, echocardiography, ultrasound of the thorax, and transtracheal or endotracheal wash can be useful. When the disease process is in the pleural space, thoracocentesis can be both diagnostic and therapeutic. Chest tube placement may be necessary for continuous removal of air or fluid from the pleural space. Monitoring of the respiratory patient can involve serial physical examination, pulse oximetry, and arterial blood gas analysis. It is essential to minimize stress on patients with respiratory distress because decompensation can occur easily, leading to respiratory arrest.  相似文献   
2.

Objective

To determine if neuromuscular monitoring at the pelvic limb accurately reflects neuromuscular function in the larynx after administration of rocuronium in anesthetized dogs.

Study design

Prospective experimental study.

Animals

Six healthy Beagle dogs.

Methods

Anesthesia was maintained in dogs with isoflurane and a continuous infusion of dexmedetomidine. Rocuronium (0.6 mg kg?1) was administered intravenously to induce neuromuscular block. Train-of-four (TOF) impulses were applied to the left recurrent laryngeal nerve (RLn) and the peroneal nerve (Pn). The evoked TOF ratio (TOFR; T4:T1) was measured with electromyography (EMG) simultaneously at the larynx and at the pelvic limb. Spontaneous recoveries of T1 to 25% (T125%) and 75% (T175%) of twitch height, and to TOFR of 0.70 and 0.90 (TOFR0.90) at each EMG site were compared.

Results

Data from five dogs were analyzed. Times to T125% were similar at the pelvic limb and larynx when measured by EMG; time to T175% was slower at the larynx by 6 ± 4 minutes (p = 0.012). The larynx had a slower recovery to TOFR0.70 (41 ± 13 minutes) and TOFR0.90 (45 ± 13 minutes) than did the pelvic limb [29 ± 8 minutes (p = 0.011) and 33 ± 9 minutes (p = 0.003), respectively]. When the pelvic limb EMG returned to TOFR0.70 and TOFR0.90, the larynx EMG TOFR0.70 and TOFR0.90 values were 0.32 ± 0.12 (p = 0.001) and 0.38 ± 0.13 (p = 0.001), respectively.

Conclusions and clinical relevance

After administration of rocuronium, neuromuscular function assessed by EMG recovered approximately 36% slower at the larynx than at the pelvic limb. The results in these dogs suggest that quantitative neuromuscular monitoring instrumented at a pelvic limb may be unable to exclude residual block at the larynx in anesthetized dogs.  相似文献   
3.
纹枯病菌絲在田間稻株上的消长受水稻各生育期、及当时气候条件影响很大;一般在孕穗职前菌絲量少,孕穗至乳熟初期分布量大、蔓延速度快;抽穗期后10天达到最高峯。早稻成熟期菌絲停止蔓延或消失;晚稻(尤其連作晚稻)抽穗期后因寒潮或低温而停止蔓延;乳熟期趋于消失。纹枯病菌核的发育一般要通过四个时期,无休眠期。病情的水平扩展速度以孕穗至抽穗期最快,乳熟期几停止;而垂直扩展速度以水稻分蘖期最慢,抽穗至乳熟期最快。矮稈品种2—3天,高稈品种3—5天便可士升一个叶位,乳熟后緩慢。晚稻則以抽穗期最快,抽穗后緩慢,乳熟后病势停滞不前。在水稻易感期(孕穗—抽穗),遇到梅雨的两端低温,职及矮稈品种、多肥、密植,在一定有效菌核量下,是本病流行期、流行程度的关鍵因素。防治适期应以菌絲蔓延前期,卽在分蘖期至孕穗期施药,以杀伤菌絲为主;有必要时可在抽穗期再施药一次,保护剑叶,以抑制菌核形成、兼杀菌絲为主。如对矮稈品种、多肥栽培的水稻,于分蘖期施药保护是很必要的。  相似文献   
4.
5.
用本实验室分离鉴定的致病性牦牛大肠埃希氏菌,按常规方法制备了4批氢氧化铝胶灭活疫苗。对牦牛大肠埃希氏菌的菌液培养、纯粹检验、活菌计数、灭活等进行了探索,并对用该菌研制成的疫苗进行了常规检验。结果4批灭活疫苗经无菌检验为阴性;经物理性状检验为:静置后上层是淡黄色的澄明液体,下层为灰白色沉淀,振荡后呈均匀混浊液;经牦牛安全检验结果为安全;经牦牛效力试验有效。牦牛大肠埃希氏菌病灭活疫苗为免疫预防该病打下了良好的基础。  相似文献   
6.
台湾农村生活废水之水质特性及其影响研究   总被引:8,自引:0,他引:8  
本研究之目的乃以桃园灌区农村生活废水为对象,调查其水质特性受季节变化之影响等,并与桃园大圳第二支线上游之灌溉水质进行比较。结果显示,农村生活废水的各项水质浓度与社区户数间并没有一致性存在,而是与社区规划、社区生活形态有关。其中,若因洗车、花园浇灌水等的稀释作用较小时,社区生活废水的化学需氧量约为 159~563mg/L、总氮 15~68mg/L,总磷 0.6~5.7mg/L。在季节变化的影响方面,发现生活废水中的 pH值乃随雨季初期→中期→末期而逐渐降低;电导度、生化需氧量、有机氮、凯氏氮及总氮的平均污染浓度则随雨季初期→中期→末期的顺序而升高;至于化学需氧量、氨氮、硝酸盐氮、亚硝酸盐氮及总磷,是以雨季中期之污染值最高。最后,研究指出,农村生活废水的污染浓度非常高,其中,电导度是桃园大圳第二支线上游灌溉水质的 2.2倍,化学需氧量为 22.5倍,生化需氧量 45.6倍,氨氮 2.2倍,有机氮 122.4倍,凯氏氮 44.0倍,亚硝酸盐氮 2.4倍,总氮 14.3倍及总磷 128.3倍。因此,若不慎将生活废水排入灌溉水道,将严重影响灌溉水的品质。  相似文献   
7.
Meiotic disturbances in F1 hybrids and their progenies are still major problems in wide hybridization.To investigate the genome affinity reflected in chromosome pairing and segregation,we studied chromosome behaviors during meiosis in two interspecific F1 hybrids[O.minuta×O.australiensis(Om×Oa,BCE genome)and Oa×O.ridleyi(Or,EHJ genome)]by using both traditional staining methods and genomic in situ hybridization(GISH).GISH analysis has been successfully performed on mitotic chromosomes to distinguish different Oryza genomes,but relatively fewer systematic analyses of meiotic chromosomes of interspecific hybrids have been reported.In the hybrids,highly irregular chromosome behaviors through meiosis resulted in producing microspores with unbalanced genome.At diakinesis of these two hybrids,most chromosomes present as univalent,with low frequency as bivalents and occasionally as trivalents.In a pollen mother cell,2 to 8 bivalents and 0 to 4 trivalents were observed in the hybrid Oa×Or,and 1 to 8 bivalents and 0 to 5 trivalents were observed in the hybrid Om×Oa.GISH results indicated that 51.52%bivalents in Oa×Or and 79.65%bivalents in Om×Oa involved allosyndetic association,which indicates that recombination and introgression should be possible if viable backcrosses can be recovered even from triploid hybrids.In this study,we revealed that the meiotic disturbance due to low affinities between parental genomes is the major reason for the sterility of these two triploid interspecific hybrids.The two hybrids showing vigor in reproductive growth are potential genetic resources in future breeding programs.A better understanding of genomic affinities between these distant Oryza species can facilitate planning an effective breeding program by using wide hybridization,and efficient and routine GISH analysis is helpful to monitor alien introgression in the process.  相似文献   
8.
9.
Maltooligosyltrehalose synthase (MTSase) is one of the key enzymes involved in trehalose production from starch and catalyzes an intramolecular transglycosylation reaction by converting the alpha-1,4- to alpha,alpha-1,1-glucosidic linkage. Mutations at residues F206, F207, and F405 were constructed to change the selectivity of the enzyme because the changes in selectivity could reduce the side hydrolysis reaction of releasing glucose and thus increase trehalose production from starch. As compared with wild-type MTSase, F405Y and F405M MTSases had decreased ratios of the initial rate of glucose formation to that of trehalose formation in starch digestion at 75 degrees C when wild-type and mutant MTSases were, respectively, used with isoamylase and maltooligosyltrehalose trehalohydrolase (MTHase). The highest trehalose yield from starch digestion was by the mutant MTSase having the lowest initial rate of glucose formation to trehalose formation, and this predicted high trehalose yield better than the ratio of catalytic efficiency for hydrolysis to that for transglycosylation.  相似文献   
10.
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