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   524篇
  免费   39篇
  国内免费   4篇
  2023年   5篇
  2022年   12篇
  2021年   13篇
  2020年   11篇
  2019年   18篇
  2018年   16篇
  2017年   9篇
  2016年   32篇
  2015年   35篇
  2014年   37篇
  2013年   28篇
  2012年   37篇
  2011年   34篇
  2010年   22篇
  2009年   14篇
  2008年   37篇
  2007年   34篇
  2006年   25篇
  2005年   19篇
  2004年   25篇
  2003年   13篇
  2002年   8篇
  2001年   10篇
  2000年   7篇
  1999年   3篇
  1998年   7篇
  1997年   6篇
  1996年   4篇
  1994年   1篇
  1993年   2篇
  1992年   6篇
  1991年   2篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1987年   7篇
  1986年   3篇
  1985年   1篇
  1984年   2篇
  1983年   4篇
  1982年   4篇
  1979年   1篇
  1978年   1篇
  1970年   1篇
  1963年   1篇
  1931年   2篇
排序方式: 共有567条查询结果,搜索用时 46 毫秒
31.
32.
33.
34.
35.
MOTIVATION: Numerous database management systems have been developed for processing various taxonomic data bases on biological classification or phylogenetic information. In this paper, we present an integrated system to deal with interacting classifications and phylogenies concerning particular taxonomic groups. RESULTS: An information-theoretic view (taxon view) has been applied to capture taxonomic concepts as taxonomic data entities. A data model which is suitable for supporting semantically interacting dynamic views of hierarchic classifications and a query method for interacting classifications have been developed. The concept of taxonomic view and the data model can also be expanded to carry phylogenetic information in phylogenetic trees. We have designed a prototype taxonomic database system called HICLAS (HIerarchical CLAssification System) based on the concept of taxon view, and the data models and query methods have been designed and implemented. This system can be effectively used in the taxonomic revisionary process, especially when databases are being constructed by specialists in particular groups, and the system can be used to compare classifications and phylogenetic trees. AVAILABILITY: Freely available at the WWW URL: http://aims.cps.msu.edu/hiclas/ CONTACT: pramanik@cps.msu.edu; lotus@wipm.whcnc.ac.cn  相似文献   
36.
A cDNA for a putative 42 kD spermidine synthase (OsSPDS2) was cloned from rice. The deduced OsSPDS2 sequence showed highest similarity with Arabidopsis AtSPDS3. Phylogenetic analysis revealed that OsSPDS2 and AtSPDS3 form a distinctive subclass in the spermidine synthase family in plants. OsSPDS2 mRNA accumulated in roots during long term exposure to chilling temperature (12 degrees C). In contrast, no such induction of the paralogous OsSPDS1 was observed during the chilling treatment. ABA treatment up-regulated OsSPDS2, whereas salt stress did not change OsSPDS2 levels significantly. Data suggested a distinct function of OsSPDS2 in chilling response in rice.  相似文献   
37.
We describe a new dysmorphic syndrome in an inbred Saudi Arabian family with 21 members. Five males and one female have similar craniofacial features including wide open calvarial sutures with large and late-closing anterior fontanels, frontal bossing, hyperpigmentation with capillary hemangioma of the forehead, significant hypertelorism, and a broad and prominent nose. In addition, these individuals have Y-shaped sutural cataracts diagnosed by 1-2 years of age. No chromosomal or biochemical abnormalities were identified. A genome-wide scan was performed, and two-point LOD score analysis, assuming autosomal recessive inheritance, detected linkage to chromosome 14q13-q21. The highest LOD scores were obtained for marker GATA136A04 (LOD=4.58 at theta=0.00) and for the adjacent telomeric marker D14S1048 (LOD=4.32 at theta=0.00). Multipoint linkage analysis resulted in a maximum LOD score of 5.44 between markers D14S1048 and GATA136A04. Model independent analysis by SIBPAL confirmed linkage to the same chromosomal region. Haplotype analysis indicated that all affected individuals were homozygous for the interval on chromosome 14q13-q21 with two recombinants for D14S1014 (centromeric) and one recombinant for D14S301 (telomeric). These recombinations limit the disease locus to a region of approximately 7.26 Mb. Candidate genes localized to this region were identified, and analysis of PAX9 did not identify mutations in these patients. The unique clinical phenotype and the mapping data suggest that this family represents a novel autosomal recessive syndrome.  相似文献   
38.
39.
Glucose oxidase (GOD) from Aspergillus niger was expressed in Saccharomyces cerevisiae under the regime of GAL-10 promoter and GAL-7 terminator of S. cerevisiae and -amylase signal sequence of Aspergillus oryzae. The enhancement of the expression level was achieved in pH-stat feed-back controlled fed-batch culture. The highest titre of extracellular GOD was 199 U/ml which marked two fold improvement over the batch (95 U/ml) and 28% above that of non-feed back controlled fed-batch (154 U/ml) operation. © Rapid Science Ltd. 1998  相似文献   
40.
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