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   851篇
  免费   51篇
  国内免费   10篇
林业   30篇
农学   40篇
基础科学   10篇
  69篇
综合类   303篇
农作物   36篇
水产渔业   19篇
畜牧兽医   336篇
园艺   25篇
植物保护   44篇
  2023年   7篇
  2022年   28篇
  2021年   15篇
  2020年   21篇
  2019年   25篇
  2018年   17篇
  2017年   31篇
  2016年   22篇
  2015年   31篇
  2014年   31篇
  2013年   31篇
  2012年   54篇
  2011年   47篇
  2010年   37篇
  2009年   34篇
  2008年   55篇
  2007年   44篇
  2006年   42篇
  2005年   25篇
  2004年   37篇
  2003年   38篇
  2002年   28篇
  2001年   17篇
  2000年   11篇
  1999年   4篇
  1998年   9篇
  1997年   4篇
  1996年   4篇
  1995年   5篇
  1994年   5篇
  1993年   6篇
  1991年   10篇
  1990年   4篇
  1989年   10篇
  1987年   4篇
  1985年   5篇
  1984年   6篇
  1979年   4篇
  1976年   6篇
  1975年   6篇
  1974年   5篇
  1973年   5篇
  1972年   3篇
  1970年   4篇
  1969年   3篇
  1967年   3篇
  1900年   3篇
  1899年   5篇
  1898年   3篇
  1892年   3篇
排序方式: 共有912条查询结果,搜索用时 15 毫秒
91.
BCL-2 family proteins constitute a critical control point for the regulation of apoptosis. Protein interaction between BCL-2 members is a prominent mechanism of control and is mediated through the amphipathic alpha-helical BH3 segment, an essential death domain. We used a chemical strategy, termed hydrocarbon stapling, to generate BH3 peptides with improved pharmacologic properties. The stapled peptides, called "stabilized alpha-helix of BCL-2 domains" (SAHBs), proved to be helical, protease-resistant, and cell-permeable molecules that bound with increased affinity to multidomain BCL-2 member pockets. A SAHB of the BH3 domain from the BID protein specifically activated the apoptotic pathway to kill leukemia cells. In addition, SAHB effectively inhibited the growth of human leukemia xenografts in vivo. Hydrocarbon stapling of native peptides may provide a useful strategy for experimental and therapeutic modulation of protein-protein interactions in many signaling pathways.  相似文献   
92.
The aim of this study was to determine the prevalence of Tritrichomonas foetus infection and associated clinical signs in purebred cats in Germany, to investigate the role of co-infection, and identify determinants of infection. Faecal specimens accompanied by epidemiological questionnaires were scored and collected from 230 purebred cats. Faeces were examined for trichomonads and other enteroparasites. The prevalence of T foetus was 15.7% among cats and 18.5% among catteries. An abnormal faecal score and history of diarrhoea were observed in 64% and 61% of T foetus-positive cats, respectively, and correlated significantly with infection. Co-infection, observed in 36% of T foetus-infected cats, was not associated with diarrhoea. Norwegian Forest cats were infected significantly more often than other breeds. No association was found with any environmental factors. This study demonstrated a high prevalence of symptomatic T foetus infections in purebred cats in Germany. Co-infection with other enteroparasites did not worsen clinical signs of trichomonosis.  相似文献   
93.
Objective To estimate mean Schirmer tear test (STT) and intraocular pressure (IOP) values in healthy koalas both conscious and anesthetized. Methods Data were gathered from koalas in Victoria, Australia. Conscious examinations were performed on captive koalas. Free‐ranging (wild) koalas were examined under anesthesia. Anesthesia was induced using alfaxalone, and animals were maintained on oxygen and isoflurane if required. All animals were healthy and had no surface ocular pathology detectable during slit lamp biomicroscopy. STT I tests were performed using commercial STT test strips placed in the lower fornix for 1 min. IOP was measured using an applanation tonometer after topical anesthesia. The higher value of the two eyes for both STT and IOP was analyzed. STT was measured in 53 koalas (34 conscious, 19 anesthetized) and IOP was measured in 43 koalas (30 conscious, 13 anesthetized). A two‐sample t‐test was used to compare means. A P‐value <0.05 was regarded as significant. Mean ± SD is presented. Results The mean higher STT in conscious koalas was 10.3 ± 3.6 mm wetting/min and in anesthetized koalas it decreased to 3.8 ± 4.0 mm wetting/min (P < 0.0001). The mean higher IOP in conscious koalas was 15.3 ± 5.1 mmHg, and in anesthetized koalas it was 13.8 ± 3.4 mmHg (P = 0.32). There was no effect of sex on either STT or IOP. Conclusions The mean and SD of STT and IOP values for koalas both conscious and anesthetized were reported. The mean STT was significantly reduced by alfaxalone anesthesia.  相似文献   
94.
A 14-yr-old female eastern black rhinoceros (Diceros bicornis michaeli) presented with progressive suppurative osteomyelitis in her left hind lateral toe. beta-Hemolytic Streptococcus sp. was isolated. The animal was treated with multiple systemic antibiotics, and topical wound cleansing. Repeated debridements and nail trimmings were performed for 5 mo prior to electing amputation. The toe was surgically amputated under general anesthesia between the first and second phalanges. Analgesia was diffused into the wound topically via a catheter and elastomeric pump. The open amputation site was covered with adherent drapes and a negative-pressure wound therapy device provided vacuum-assisted closure (V.A.C.) for 72 hr. Three months later this animal developed a deep dermal ulcer on the lateral aspect of the right hind limb, at the level of the stifle. Methicillin-resistant Staphylococcus aureus was isolated. The wound was managed by initial daily lavage, followed by 1 mo of V.A.C. therapy, with 72 hr between dressing changes. Clinically, this therapy expedited the formation of healthy granulation tissue and overall healing was accelerated. The animal tolerated the machine and bandage changes well via operant conditioning. The use of negative-pressure wound therapy appeared to shorten time to resolution of slow-healing wounds in black rhinoceros.  相似文献   
95.
A rapid and sensitive method is described for the quantitation of erythromycin A (EA) in edible salmon tissue by liquid chromatography (LC) analysis using either electrochemical detection (ED) or electrospray ionization mass spectrometric (ESI/MS) detection. The salmon tissue is extracted with 10 mM ammonium formate. The extract is then purified by solid phase extraction using a hydrophilic-lipophilic balanced (HLB) polymeric-based C18 packing, followed by partitioning of EA into methylene chloride at alkaline pH, evaporation, and final dilution. The mean recoveries of EA at 50, 100, 200, and 400 ppb levels in fortified salmon tissue were 63.8 +/- 6.0 and 75.5 +/- 5.4% by LC-ED and LC-ESI/MS, respectively. There was no evidence of formation of the anhydro-EA (m/z 716) decomposition product of EA (m/z 734) that was reported to occur by other published methods.  相似文献   
96.
The degradation profile of glucosamine bulk form stressed at 100 degrees C for 2 h in an aqueous solution was studied. Column chromatography of acetylated product mixture led to isolation of two pure compounds (1b and 2b) and a mixture of at least three isomers (3b). 1a and 2a were identified as 5-(hydroxymethyl)-2-furaldehyde (5-HMF) and 2-(tetrahydroxybutyl)-5-(3',4'-dihydroxy-1'-trans-butenyl)pyrazine, respectively, by utilizing a variety of analytical techniques, such as GC-MS, LC-MS, on-line UV spectrum, (1)H and (13)C NMR, and DEPT, as well as (1)H-(1)H COSY. 3a was identified as 2-(tetrahydroxybutyl)-5-(2',3',4'-trihydroxybutyl)pyrazine, commonly known as deoxyfructosazine. In addition, glucosamine solid dosage form was exposed to 40 degrees C/75% relative humility for 10 weeks. Methanol extract of glucosamine solid dosage form was analyzed after acetylation by LC-MS, resulting in degradants 3b and 4b. 3a and 4a were, therefore, determined as deoxyfructosazine and 2,5-bis(tetrahydroxybutyl)pyrazine (fructosazine), respectively. Furthermore, the mechanisms of formation of identified degradation products are proposed and briefly discussed.  相似文献   
97.
以无精蛋、鲜蛋为原料加工成咸鸭蛋,研究在15℃下不同盐浓度腌制液和不同腌制用水的最佳腌制天数,确定最佳盐浓度和腌制用水。结果表明,15%、17%和19%盐浓度生水腌制液腌制无精蛋均需25 d;21%和23%盐浓度生水腌制液腌制无精蛋需23 d;25%盐浓度生水腌制液腌制无精蛋仅需21 d,与相同浓度生水腌制液腌制鲜蛋的出缸时间相同,而25%盐浓度的凉开水和桶装水腌制液腌制鲜蛋则需23 d;说明生水腌制液腌制无精蛋和鲜蛋可以缩短腌制周期,且用无精蛋与鲜蛋制作的咸鸭蛋的特性相差不大,可以提高无精蛋的利用率。  相似文献   
98.
为分析KT预处理液对洋桔梗(Eustoma russellianum)切花的保鲜效果,采用不同浓度的KT预处理液处理洋桔梗,干藏后检测鲜切花的瓶插寿命、可溶性糖、花青素、SOD、MDA等生理生化指标。结果表明,干藏洋桔梗切花使用KT预处理液处理后SOD活性增强,MDA含量降低,可溶性糖含量升高,可延缓花青素降解和延长切花瓶插寿命,且提高了洋桔梗切花的观赏品质。其中,2%蔗糖+40 mg/L KT+80 mg/L柠檬酸+200 mg/L 8-HQ配方对洋桔梗切花的保鲜效果最佳。  相似文献   
99.
In order to clarify the mechanism of rockburst, using the specified loading equipment and the CT machine, the real-time computerized tomography testing of coal under the uniaxial compression was completed. Through CT scanning, the clear CT images which included the stage from the microcrack clousre to the microcrack growth, bifurcation, development, failure and the post-failure stage were obtained. According to the CT values, the meso-damage evolution of coal under uniaxial compression was analysed, which provided the basis for the meso-damage evolution.  相似文献   
100.
The acute single dose oral toxicity of carbophenothion (S-4-chlorophenylthiomethyl OO-diethyl phosphorodithioate) has been determined in Canada geese (Branta canadensis), pigeons (Columba livia) and Japanese quail (Coturnix coturnix japonica). At post mortem examination gross pathological changes were observed in Canada geese and pigeons and esterase levels were determined by conventional and electrophoretic methods on extracts of liver and brain from these two species. Carbophenothion residue levels were determined in liver, brain and gizzard contents from the geese and pigeons. The overall pattern of results suggests that esterase inhibition may not be the dominant factor in carbophenothion poisoning in geese. It is suggested that a brain carbophenothion residue level of 1 part/106 is indicative of death by poisoning in geese.  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