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   1711篇
  免费   130篇
  2022年   8篇
  2021年   8篇
  2020年   7篇
  2019年   7篇
  2018年   19篇
  2017年   18篇
  2016年   31篇
  2015年   44篇
  2014年   37篇
  2013年   73篇
  2012年   75篇
  2011年   64篇
  2010年   58篇
  2009年   45篇
  2008年   70篇
  2007年   77篇
  2006年   93篇
  2005年   62篇
  2004年   79篇
  2003年   64篇
  2002年   77篇
  2001年   81篇
  2000年   86篇
  1999年   60篇
  1998年   26篇
  1997年   33篇
  1996年   21篇
  1995年   17篇
  1994年   10篇
  1993年   20篇
  1992年   58篇
  1991年   43篇
  1990年   50篇
  1989年   34篇
  1988年   38篇
  1987年   38篇
  1986年   33篇
  1985年   19篇
  1984年   11篇
  1983年   12篇
  1982年   12篇
  1981年   8篇
  1980年   9篇
  1979年   14篇
  1977年   7篇
  1974年   7篇
  1973年   8篇
  1970年   7篇
  1969年   13篇
  1967年   9篇
排序方式: 共有1841条查询结果,搜索用时 15 毫秒
61.
62.
63.
Thirty-eight strains of 12Microsporum and 10Arthroderma (Nannizzia) species were investigated by analysis of mitochondrial DNA with 6 restriction enzymes, and classified into 13 genetic groups. The phylogenetic tree of the 13 groups thus established was constructed. On the tree,M. audouinii, M. langeronii, M. rivalieri, M. distortum, M. equinum, M. ferrugineum andA. otae comprise one genetic group and are suggested to be the same species.A. gypseum, A. fulvum, M. duboisii, M. ripariae, A. incurvatum, A. persicolor andA. obtusum are clustered on one of five boughs of the tree indicating their close relation.A. racemosum andA. cajetani are also closely related.  相似文献   
64.
To determine whether the acid phosphatase in Micrococcus denitrificans participates in hydrolysis of thiamine phosphate in the synthesis of thiamine pyrophosphate, acid phosphatase was purified 280-fold by conventional procedures, which removed thiamine phosphate phosphatase completely. Studies showed that this acid phosphatase is a different protein from thiamine phosphate phosphatase and that it has no binding site for thiamine phosphate on its active site.  相似文献   
65.
Intraventricular administration of muscimol (25–100 ng) and intravenously applied aminooxyacetic acid (2.5–10 mg/kg) depressed the crossed extensor reflex response in a dose-dependent manner. The inhibitory effects of both drugs were clearly antagonized by a subconvulsive dose of bicuculline. A very small dose of bicuculline (10–40 μg/kg, i.v.) produced a dose-related enhancement of the crossed extensor reflex response without any sign of convulsion. These results suggest that the crossed extensor reflex response is very sensitive to GABAergic drugs and central GABAergic mechanisms play a role in the modulation of the crossed extensor reflex response.  相似文献   
66.
From the aerial parts of Fritillaria thunbergii, three glycosidal Solanum alkaloids (basic steroid saponins) were isolated together with minor  相似文献   
67.
The effect of amytal on energy metabolism and acid secretion in an isolated gastric mucosa of the guinea-pig were studied. Determination of adenine nucleotides, creatine phosphate, pyruvate and lactate in the gastric mucosa showed that amytal depressed the levels of ATP, creatine phosphate and energy charge with elevation of the AMP and pyruvate levels. This treatment inhibited concomitantly acid secretion and active chloride transport detected by short circuit current. The addition of menadione with ascorbate to the medium in the presence of amytal partially restored ATP and energy charge levels and also induced a partial recovery of acid secretion and active chloride transport. These results suggest that ATP is a direct energy donor for acid secretion in the gastric mucosa of the guinea-pig.  相似文献   
68.
The amounts of d-alanine derivatives, γ-l-glutamyl-d-alanine and N-malonyl-d-alanine, increase rapidly during the early growth of pea seeds. Pyruvate-[1?14C], l-alanine-[U?14C], d-alanine-[U?14C], l-alanine-[15N] and 15NH4Cl were therefore fed to the seedlings and the incorporation investigated. Labelling results revealed that pea seedlings can utilize these erogenous compounds to form d-alanine and that labelled l-alanine is effectively converted to the d-enantiomer with retention of 14C and, largely, 15N label. Enzyme analyses in vitro provided additional evidence that the extract of pea seedlings catalyzes the direct conversion of l-alanine to d-alanine. The data suggest that the de novo synthesis of d-alanine in pea seedlings occurs by a racemase reaction.  相似文献   
69.
A complementary DNA (cDNA) clone that encodes phosphatidylinositol 4-kinase (PI 4-kinase) was isolated from a rat brain cDNA library. The deduced amino acid sequence of 697 residues revealed that the protein contains two putative transmembrane sequences and that the N-terminal part of the protein has several sequences representing potential phosphorylation sites for cAMP- and calmodulin-dependent kinase. The C-terminal region is probably a phosphotransferase domain homologous to the kinase region of protein kinase family proteins. Specific antibody against the protein expressed in Escherichia coli successfully immunoprecipitated rat brain PI 4-kinase. The messenger RNA for PI 4-kinase was found predominantly in brain and rat neural cell lines. This PI kinase may play a specific role in neural signal transduction.  相似文献   
70.
The asparagine-linked sugar chains of blood coagulation factor VIII preparations purified from human plasma of blood group A donors and from the culture media of recombinant BHK cells were released as oligosaccharides by hydrazinolysis. These sugar chains were converted to radioactive oligosaccharides by reduction with sodium borotritide and separated into neutral and acidic fractions by paper electrophoresis. Most of the acidic oligosaccharides were converted to neutral ones by sialidase digestion, indicating that they are sialyl derivatives. The neutral and sialidase-treated acidic oligosaccharides were fractionated by serial chromatography on immobilized lectin columns and Bio-Gel P-4 column. Structural study of each oligosaccharide by sequential exo- and endoglycosidase digestion and by methylation analysis revealed that both factor VIII preparations contain mainly high mannose-type and bi-, tri-, and tetra-antennary complex-type sugar chains. Some of the biantennary complex-type sugar chains from human plasma factor VIII contain blood group A and/or H determinant, while those from recombinant product do not. Some of the bi-, tri- and tetra-antennary complex-type sugar chains of the recombinant factor VIII contain the Gal alpha 1----3Gal group. A small number of the triantennary complex-type sugar chains from both preparations was found to contain the Gal beta 1----4(Fuc alpha 1----3)GlcNAc beta 1----4 (Gal beta 1----4GlcNAc beta 1----2)Man group. Studies of pharmacokinetic parameters of the recombinant factor VIII infused into baboons revealed that its half-life in blood circulation is similar to that of plasma derived factor VIII, suggesting that the oligosaccharide structural differences between them do not affect the fate of factor VIII in vivo.  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