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   143篇
  免费   6篇
  国内免费   9篇
林业   14篇
农学   12篇
  24篇
综合类   11篇
农作物   6篇
水产渔业   11篇
畜牧兽医   70篇
园艺   6篇
植物保护   4篇
  2024年   1篇
  2023年   2篇
  2022年   7篇
  2021年   5篇
  2020年   1篇
  2019年   2篇
  2018年   4篇
  2017年   8篇
  2016年   6篇
  2015年   8篇
  2014年   8篇
  2013年   9篇
  2012年   8篇
  2011年   11篇
  2010年   5篇
  2009年   4篇
  2008年   10篇
  2007年   13篇
  2006年   4篇
  2005年   6篇
  2004年   2篇
  2003年   7篇
  2002年   8篇
  2001年   2篇
  2000年   1篇
  1999年   3篇
  1998年   2篇
  1996年   3篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1975年   1篇
排序方式: 共有158条查询结果,搜索用时 0 毫秒
41.
To develop a new nonchlorine bleaching technology, hardwood and softwood kraft pulps, before and after oxygen-alkali predelignification, were treated with dilute sulfuric acid solutions (pH 1.0-1.8) at 100°C for 1 h and then extracted with aqueous sodium hydroxide at 70°C for l h. Hardwood kraft pulp was successfully bleached. The delignification selectivity was similar to that seen with oxygen-alkali bleaching; and it was greatly enhanced by the addition of sodium nitrate and sodium nitrite. The sulfuric acid bleaching can replace the presently adopted oxygen and chlorine stages if the additives are allowed. This bleaching process was also effective for oxygen-bleached hardwood kraft pulp, but it was less effective for softwood kraft pulp and oxygen-bleached softwood kraft pulp. The effectiveness of the addition of sodium nitrate and sodium nitrite was more apparent for softwood kraft pulp than for hardwood kraft pulp.Part of this report was presented at the 7th International Symposium on Wood and Pulping Chemistry, Beijing, July 1993  相似文献   
42.
Chiral resolution of imazalil, a fungicide, was performed by capillary electrophoresis (CE) using 2-hydroxypropyl-beta-cyclodextrin as a chiral selector. Factors affecting the chiral resolution and migration time of imazalil were studied. The optimum running conditions were found to be 5 mM ammonium dihydrogenphosphate-50 mM phosphate buffer (pH 3.0) containing 4 mM 2-hydroxypropyl-beta-cyclodextrin with an effective voltage of +25 kV at 20 degrees C using direct detection at 200 nm. Under these conditions, the resolution (Rs) of racemic imazalil was approximately 6. The extraction of imazalil from orange samples was done with acetonitrile under basic conditions. The extract was purified with a solid-phase extraction cartridge (Sep-Pak plus PS-2) and was analyzed by the above CE method. Eight orange samples were analyzed, and imazalil was detected in seven samples. In four of these seven oranges, the level of (-)-imazalil was the same as that of (+)-imazalil, but in the other three oranges, the level of (-)-imazalil was found to be lower than that of (+)-imazalil, suggesting that (-)-imazalil was degraded more quickly than (+)-imazalil in oranges.  相似文献   
43.
波纹巴非蛤的形态分析与营养成分评价   总被引:1,自引:0,他引:1  
文章分析了波纹巴非蛤(Paphia undulate)的形态性状、出肉率及蛤肉的主要营养成分,并综合评价了其营养价值。结果显示,波纹巴非蛤的出肉率达35.73%;蛤肉中蛋白质占鲜质量的12.8%;18种氨基酸总量约占干质量的46.21%,其中8种必需氨基酸(EAA)占氨基酸总量的34.67%,4种鲜味氨基酸占氨基酸总量的41.94%;牛磺酸(Tau)的质量分数较高,占干质量的3.03%;不饱和脂肪酸(UFA)占脂肪酸总量的51.9%,C22:6(DHA)和C20:5(EPA)共占32.8%;矿物质丰富,尤其是钾(K)元素的质量分数高达3.407mg·g-1。  相似文献   
44.
A novel enzyme that catalyzes efficient hydrolysis of capsaicin (8-methyl-N-vanillyl-6-nonenamide) was isolated from the culture broth of Streptomyces mobaraensis. The enzyme consisted of two dissimilar subunits with molecular masses of 61 and 19 kDa. The enzyme was activated and stabilized in the presence of Co2+. It showed a pH optimum of about 8 and was stable at temperatures of up to 55 degrees C for 1 h at pH 7.8. The specific activity of the enzyme for the hydrolysis of capsaicin was 10(2)-10(4) times higher than those for the enzymes reported to date. In an aqueous/n-hexane biphasic system, capsaicin analogues such as octanoyl, decanoyl, and lauroyl vanillylamides were synthesized from the corresponding fatty acids and vanillylamine at yields of 50% or greater. In addition, the enzyme catalyzed the deacylation of N-lauroyl-L-amino acids and N-lauroyl-L-dipeptides and the efficient synthesis of Nalpha-lauroyl-L-lysine, Nepsilon-lauroyl-L-lysine, and various N-lauroyl-peptides in aqueous solution in both the absence and the presence of glycerol.  相似文献   
45.
Lipomatosis of lymph nodes is defined as the replacement of the lymphatic parenchyma by adipose tissue which grows in the node from the hilus toward the cortical zone. In humans, it is considered as part of the normal aging process and is common in obese patients, but there are no reports in non-human primates. In this report, we describe the first case of lymph node lipomatosis in the bilateral axillary lymph nodes of a young adult cynomolgus monkey. Macroscopically, there were no apparent abnormalities in the axillary lymph nodes on either side, and their volumes were unchanged. At the cut surface, pale yellow fat-like tissue was observed in the medullary area. Histopathologically, well differentiated adipocytes replaced a large part of the lymphatic parenchyma in the area from the hilus to the medulla without any malignant findings. Based on these findings, the patient was diagnosed with lipomatosis of the lymph nodes.  相似文献   
46.
Eleven somatic hybrids (2n = 68 to 74) obtained between S. tuberosum ssp. tuberosum cv. Dejima (2n = 48) and ATDH-1 (2n = 24), an anther-culture-derived dihaploid of S. acaule (Yamada et al., 1997), were characterized by nuclear RFLP markers using 49 single-copy DNA probes distributed throughout the potato genome (2 to 6 probes per chromosome). One of the somatic hybrids, DA8-2, had 72 chromosomes and all the Dejima- and ATDH-1-specific markers (124 and 103 bands, respectively), suggesting the presence of a whole set of both parental chromosomes. The other somatic hybrids lost varying numbers of markers up to seventeen. The pattern of the loss of markers indicated the elimination of five chromosomes among four somatic hybrids. A nucleolar organizer region of chromosome 2 was often eliminated in the somatic hybrids. The somatic hybrids studied here had higher frequencies of multivalent formation than the S. tuberosum parent. They had reasonably good seed set when pollinated with S. tuberosum pollen. Hence, homoeologous recombination between S. acaule and S. tuberosum chromosomes is possible and useful traits from S. acaule may be transferred to the S. tuberosum gene pool. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
47.
The exposure of freesia corms to ethylene (C2H4) at ca. 10 μl/l air for only 5 h was sufficient to promote sprouting, either under a closed system in which corms were treated in a sealed space of 3–10 1 or under a flow system in which corms were exposed to a continuous flow of air containing C2H4. Under the closed system, little change in corm response to C2H4 was found with increasing duration of exposure from 5 to 48 h, and the C02 concentration reached nearly 4% after 48 h. On the other hand, under the flow system, in which CO2 did not accumulate above 0.1%, the promotive effect of C2H4 was diminished by extended exposure from 5 to 48 h.Repeated treatment with C2H4 for 23 h daily on 4 successive days resulted in the lowering of the promotive effect as compared with a single treatment, but repeated application of C2H4 for 5 h daily showed the same effect as a single application and gave a high sprouting rate similar to smoke treatment, independent of ambient temperature ranging from 25 to 35° C.Corms exposed to C2H4 for 5 h daily, or to smoke for 4 days, exhibited a better chilling response and advanced flowering.  相似文献   
48.
49.
Oligodendroglioma is a rare tumor originating from oligodendrocytes found mainly in the cerebrum in aged rats. Only a few reports have shown spontaneous occurrence of this tumor in the spinal cord, and no report has mentioned its occurrence in young rats. We encountered a case of spontaneous oligodendroglioma in the lumbar portion of the spinal cord in a young (9 weeks old) female BrlHan:WIST@Jcl (GALAS) rat. Here we report the detailed histopathological and immunohistochemical characteristics of this case. No clinical signs, no gross lesions at necropsy, and no specific changes in hematology or blood biochemistry were observed. The tumor was located in the dorsal funiculus in the lumbar portion of the spinal cord and widely spread to the dorsal root nerve. The neoplastic cells showed a sheet-like growth pattern and had small round nuclei, clear cytoplasm and distinct cell borders that resulted in a honeycomb pattern. No mitotic figures or other histological lesions were observed. The neoplastic cells were positively stained for Olig2 and PCNA. The present case was considered to be a low-grade oligodendroglioma based on the histological and immunohistochemical features. To our knowledge, our case is considered to be extremely rare and the first report in a young rat.  相似文献   
50.
Non-invasive and immediate estimation of left atrial pressure (LAP) is very useful for the management of mitral regurgitation (MR), and many reports have assessed echocardiographic estimations of LAP to date. However, it has been unclear of which examination and evaluate article possess the best accuracy for the MR severity. The present research aims to establish the echocardiographic estimation equation of LAP that is well applicable for clinical MR dogs. After the chordae tendineae rupture was experimentally induced via left atriotomy in six healthy beagle dogs (three males and three females, two years old, weighing between 9.8 to 12.8 kg), a radio telemetry transmitter catheter was inserted, which allows the continuous recordings of LAP without the use of sedation. Approximately 5 weeks after the surgery, echocardiographic examination, indirect blood pressure measurement, measurement of plasma atrial natriuretic peptide (ANP) and LAP measurement by way of the radio telemetry system was performed simultaneously. Subsequently, simple linear regression equations between LAP and each variable were obtained, and the equations were evaluated whether to be applicable for clinical MR dogs. As a result, the ratio of early diastolic mitral flow to early diastolic lateral mitral annulus velocity (E/Ea) had the strongest correlation as maximum LAP=7.03*(E/Ea)-54.86 (r=0.74), and as mean LAP=4.94*(E/Ea)-40.37 (r=0.70) among the all variables. Therefore, these two equations associated with E/Ea should bring more precise and instant estimations of maximum and mean LAP in clinical MR dogs.  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