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   3842篇
  免费   342篇
  国内免费   332篇
  4516篇
  2024年   9篇
  2023年   47篇
  2022年   111篇
  2021年   203篇
  2020年   133篇
  2019年   166篇
  2018年   155篇
  2017年   123篇
  2016年   185篇
  2015年   228篇
  2014年   253篇
  2013年   286篇
  2012年   322篇
  2011年   293篇
  2010年   188篇
  2009年   166篇
  2008年   206篇
  2007年   156篇
  2006年   174篇
  2005年   150篇
  2004年   141篇
  2003年   107篇
  2002年   115篇
  2001年   97篇
  2000年   85篇
  1999年   79篇
  1998年   46篇
  1997年   44篇
  1996年   38篇
  1995年   34篇
  1994年   29篇
  1993年   21篇
  1992年   19篇
  1991年   23篇
  1990年   11篇
  1989年   6篇
  1988年   10篇
  1987年   14篇
  1986年   8篇
  1985年   8篇
  1984年   8篇
  1983年   4篇
  1982年   2篇
  1981年   5篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1974年   1篇
  1971年   1篇
排序方式: 共有4516条查询结果,搜索用时 15 毫秒
91.
Metaeritrichium has been considered monotypic and endemic to China in traditional taxonomic treatments. However, our examinations of specimens and bibliography, combined with field observations, reveal that Metaeritrichium microuloides is conspecific with Actinocarya acaulis. Metaeritrichium is therefore treated as a synonym of Actinocarya. We also clarify the typification of Actinocarya acaulis.  相似文献   
92.
Bao  Zhonglei  Liu  Jianghua  Fu  Jin 《Amino acids》2022,54(6):859-875
Amino Acids - Human microtubule-associated protein Tau (τ) is abundant in the axons of neurons where it stabilizes microtubule bundles; abnormally hyperphosphorylated τ is a hallmark of...  相似文献   
93.
Zea mays (Z. mays) is one of the main cereal crops in the world, and it′s by-products have exhibited medicinal properties to explore. This article intends to review the chemical compositions and pharmacological activities of by-products of Z. mays (corn silks, roots, bract, stems, bran, and leaves) which support the therapeutic potential in the treatment of different diseases, with emphasis on the natural occurring compounds and detailed pharmacological developments. Based on this review, 231 natural compounds are presented. Among them, flavonoids, terpenes, phenylpropanoids, and alkaloids are the most frequently reported. The by-products of Z. mays possess diuretic effects, hepatoprotective, anti-diabetic, antioxidant, neuroprotective, anti-inflammatory, anti-cancer, plant protection activity, and other activities. This article reviewed the phytochemistry and pharmacological activities of Z. mays for comprehensive quality control and the safety and effectiveness to enhance future application.  相似文献   
94.
95.
A new computational approach for real protein folding prediction   总被引:4,自引:0,他引:4  
An effective and fast minimization approach is proposed for the prediction of protein folding, in which the 'relative entropy' is used as a minimization function and the off-lattice model is used. In this approach, we only use the information of distances between the consecutive Calpha atoms along the peptide chain and a generalized form of the contact potential for 20 types of amino acids. Tests of the algorithm are performed on the real proteins. The root mean square deviations of the structures of eight folded target proteins versus the native structures are in a reasonable range. In principle, this method is an improvement on the energy minimization approach.  相似文献   
96.
Aims: Our objectives were to determine the variations in phenotypic traits of Armeniaca sibirica populations and their spatial patterns. Methods: We used nested variation, coefficient of variation, multi-comparison, correlation analysis and principal component analysis to analyze the 23 phenotypic traits for 130 individuals in 13 populations of A. sibirica. Important findings: The results showed that there were significant differences in phenotypic variations among and within populations. The variation was greater among populations (47.15%) than within population (16.43%). The mean phenotypic differentiation coefficient was 73.03% among populations, indicating the variance among populations being the main source of the phenotypic variation. The average variation coefficient of 23 traits ranged from 7.01% to 27.23%, with an average of 14.28%. The variation coefficient of nutlet was highest (15.67%), and the variation coefficient of fruit was smallest (12.11%). The phenotypic diversity is highest in Wanjiagou Tumotezuoqi and smallest in Horqin, Right Front Banner Chaersen. Longitude, mean annual precipitation and sunshine duration were significantly correlated with major traits of phenotypic. The 13 populations could be divided into four groups according to the principal component analysis. Leaf traits of Wula Mountain and nutlet traits of Archorchin Banner were significantly correlated with ecological and geographic factors.  相似文献   
97.
白背飞虱单克隆抗体的制备及其特性的研究   总被引:5,自引:0,他引:5  
应用杂交瘤技术,制备出4株高度特异性的白背飞虱单克隆抗体,分别命名为WPH-1H9、WPH-2B6、WPH-2E12和WPH-3F12。这些抗体与其它8种昆虫未发生交叉反应,其中WPH-2B6可与白背飞虱所有虫态发生反应,其余3株只与卵和雌成虫发生反应。应用免疫双扩散法鉴定抗体类型及亚类,结果表明:WPH-2B6为IgG2b亚类,其余均为IgG1亚类。SDS-聚丙烯酰胺凝胶电泳和Western blot印迹分析表明,白背飞虱抗原主要由分子量分别为182、116、66.2及40 kD的4个多肽组成,其中WPH-2B6与182、116 kD的多肽结合,其余3株的单抗只与116 kD的多肽具有亲和性。最后对这些单克隆抗体在捕食作用研究中的应用潜力进行了讨论。  相似文献   
98.
重点讨论了端粒酶在肿瘤细胞和永生化细胞中的作用和功能,以及它与细胞衰老和永生化的关系.多数真核细胞的端粒酶能将单一重复序列加到端粒DNA的3′末端.端粒酶主要由模板RNA和端粒酶蛋白催化亚基组成,后者以前者为模板起逆转录酶的作用.端粒酶活性存在于肿瘤细胞中,而在良性肿瘤、体细胞中未发现端粒酶.  相似文献   
99.
巴西蘑菇能够降解棉籽壳和麦草两种培养基中木质纤维素复合体中的全部组分,属于白腐真菌;巴西蘑菇降解的有机物质的绝大部分被菌体的呼吸过程消耗掉,其绝对生物学效率较低,仅为4.41%~5.25%;在栽培前期木质素的降解速率大于纤维素和半纤维素,这对纤维素和半纤维素的降解十分有利;非木质纤维素组分主要在菌丝生长阶段被利用,而木质纤维素是子实体生长发育阶段的主要碳源;就整个栽培过程而言,巴西蘑菇生长发育所需要的82.39%~84.50%的碳源来自木质纤维素。  相似文献   
100.
Avian influenza virus (AIV) non-structural protein 1 (NS1) is a multifunctional protein. It is present at high levels in infected cells and can be used for AIV detection and diagnosis. In this study, we generated monoclonal antibody (MAb) D7 against AIV NS1 protein by immunization of BALB/c mice with purified recombinant NS1 protein expressed in Escherichia coli. Isotype determination revealed that the MAb was IgG1/κ-type subclass. To identify the epitope of the MAb D7, the NS1 protein was truncated into a total of 225 15-mer peptides with 14 amino acid overlaps, which were spotted for a peptide microarray. The results revealed that the MAb D7 recognized the consensus DAPF motif. Furthermore, the AIV NS1 protein with the DAPF motif deletion was transiently expressed in 293T cells and failed to react with MAb D7. Subsequently, the DAPF motif was synthesized with an elongated GSGS linker at both the C- and N-termini. The MAb D7 reacted with the synthesized peptide both in enzyme-linked immunosorbent assay (ELISA) and dot-blot assays. From these results, we concluded that DAPF motif is the epitope of MAb D7. To our knowledge, this is the first report of a 4-mer epitope on the NS1 protein of AIV that can be recognized by MAb using a peptide microarray, which is able to simplify epitope identification, and that could serve as the basis for immune responses against avian influenza.  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