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   9929篇
  免费   847篇
  国内免费   9篇
  2022年   49篇
  2021年   109篇
  2020年   52篇
  2019年   73篇
  2018年   101篇
  2017年   91篇
  2016年   159篇
  2015年   265篇
  2014年   341篇
  2013年   467篇
  2012年   555篇
  2011年   566篇
  2010年   390篇
  2009年   362篇
  2008年   564篇
  2007年   553篇
  2006年   540篇
  2005年   556篇
  2004年   516篇
  2003年   542篇
  2002年   485篇
  2001年   128篇
  2000年   137篇
  1999年   187篇
  1998年   169篇
  1997年   138篇
  1996年   123篇
  1995年   108篇
  1994年   108篇
  1993年   99篇
  1992年   115篇
  1991年   113篇
  1990年   112篇
  1989年   105篇
  1988年   108篇
  1987年   64篇
  1986年   75篇
  1985年   86篇
  1984年   109篇
  1983年   87篇
  1982年   108篇
  1981年   95篇
  1980年   84篇
  1979年   63篇
  1978年   73篇
  1977年   74篇
  1976年   59篇
  1975年   66篇
  1974年   61篇
  1973年   69篇
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
111.
112.
1. The effect of iodination on the distribution of peptide hormones into the aqueous two-phase dextran-polyethylene glycol system and on the solubility of these hormones in aqueous polyethylene glycol and in water was assessed. Hormones that were studied included insulin, glucagon and parathyroid hormone. 2. The partition coefficient of native insulin in the dextran-polyethylene glycol system showed a minimum (about 1) near the isoelectric point of the hormone (pH 5). Partial iodination of insulin (one atom per molecule) caused little change in the distribution of the hormone. More extensive iodination markedly decreased the partition coefficient in the region of the isoelectric point and displaced the pH value at which the partition coefficient was a minimum towards lower values. 3. The solubility of native insulin in aqueous polyethylene glycol and in water showed a pH-dependence similar to that observed for the distribution in the dextran-polyethylene glycol system. Iodination of insulin decreased the solubility of the hormone in polyethylene glycol and in water in parallel, and decreased the pH value at which solubility was a minimum. The changes in solubility correlated with the degree of iodination and accounted for the changes in distribution observed at high concentrations of insulin. 4. Comparable effects of iodination on distribution and solubility were also observed with glucagon. 5. At concentrations of insulin below its maximum solubility, serum proteins caused a decrease in the partition coefficient of iodinated hormone, but not of native hormone. These effects correlated with the degree of iodination and resulted from a co-precipitation of iodinated insulin with serum proteins.  相似文献   
113.
Scleronodular type of Hodgkin''s disease: experience at the Centre hospitalier universitaire de SherbrookeThe nodular sclerosis type of Hodgkin''s disease appears to be a distinct clinical entity. However, the incidence, the initial localization of the tumour and the survival of the patients are variable. The present study was carried out on a group of 17 patients, all French Canadians living in the province of Quebec, from a total of 31 with Hodgkin''s disease, an incidence of 55%. There were more males (10) than females (7). The mean age of the group was 37 years, but that of the females was lower than that of the males. The mediastinum was involved at the onset in 47% of the patients. The initial staging (according to the classification of Rye) in 76% of the patients was I or II.Four patients showed disease below the diaphragm. The lungs were infiltrated three times, the spleen six times, and the liver five times. The duration of survival of the 17 patients was twice that of the patients with the three other types of the disease.  相似文献   
114.
115.
116.
Mixtures of (14)C-labelled glucose plus pyruvate were incubated either with rat diaphragm or slices of rat liver. Incorporation of glucose carbon into glycogen was compared with its incorporation into glucose 6-phosphate relative to the incorporation of pyruvate carbon into these metabolic products. There was no preferential incorporation of glucose carbon relative to pyruvate carbon into glycogen compared with glucose 6-phosphate in the liver slices, but there was in diaphragm. On the assumption that glucose 6-phosphate is a necessary intermediate in the conversion of pyruvate carbon into glycogen, this is evidence for the existence in muscle, but not in liver, of more than one pool of glucose 6-phosphate or of a pathway from glucose to glycogen without glucose 6-phosphate as an intermediate. Galactose carbon, relative to pyruvate carbon, was preferentially incorporated into liver glycogen, so that a substrate converted in liver into glycogen without glucose 6-phosphate as an intermediate could be detected by this approach.  相似文献   
117.
Summary Human labial salivary glands, obtained by biopsy from 32 subjects, were studied by light and electron microscopy. Intranuclear inclusions, unrelated to nucleoli, were present in many of the acinar nuclei in glands from 16 of the 32 donors. More than one inclusion was sometimes observed within a single nucleus. They measured about 1 in diameter, and were stainable in a variety of ways. They were eosinophilic, some were stained by Nile blue sulphate, some were PAS-positive, and all were Feulgen-negative. They were bounded by a single membrane, which never exhibited continuity with the nuclear envelope, and they showed considerable morphological variation. The more complex inclusions consisted of alternating shells of light and dark material with tiny dense granules embedded in the latter. The intranuclear inclusions, which apparently were non-viral in origin, were in some way related to the secretory cycle of the mucous cells, since they were found only in immature cells, and never in cells in which secretory products were abundant.This work was supported in part by grants from the Henry Spenadel Trust and the Max C. Fleischmann Foundation of Nevada, by grant CA-08748 from the National Cancer Institute, by grant 5 SO1 FR 05335-07 from the National Institutes of Health, by a grant from the National Cystic Fibrosis Research Foundation, and by an Institutional Grant to the School of Dental and Oral Surgery, Columbia University, from the National Institutes of Health.The authors are indebted to Dr.Louis Mandel for performing the biopsies used in this study. The expert technical assistance of Mrs.Mona Seggio is acknowledged.  相似文献   
118.
119.
Summary In addition to mitochondrion-desmosome complexes, peroxisome-desmosome complexes were present in mouse hepatocytes. The latter complexes consisted of a desmosome which was flanked on one or both sides by a peroxisome. Occasional desmosomes were confronted on one side by a peroxisome and on the other by a mitochondrion. It is suggested that the association between organelles and desmosomes is fortuitous, and that no functional significance can be inferred from this association.This work was supported in part by grants from the Heart Association of Northeastern Ohio, Inc., by grant 3C179 from the Cleveland Foundation, by American Cancer Society Institutional Grant In-57-H, and by grant 5 SO1 FR05335-09 from the National Institutes of Health. The expert technical assistance of Merry A. Hetrick and Jeanne Luschin is acknowledged.  相似文献   
120.
The morphological supports of integration, including the nervous system, are to be found.After a morphological observation, ecto and endoderms and their intercellular junctions are presented.The regionally different mesogleal synaptic nerve nets are surrounded by ecto and endodermal nervous structures.The presence of behavioural activity centers is also discussed.
Liste des abréviations des figures AS autozoïde sectionné - AU autozoïde - CAL canal longitudinal - CAV cavité gastrique - CC corps compact - CGL cellule globuleuse myo-épitheliale MESlame mésentériale MF microfilament - CGR cellule granuleuse myo-épithéliale - CLC cloison commune à deux autozoïdes - CLR cloison radiale - CLT cloison transversale - CM corps myélinique - CME cellule mesenchymateuse - CNE cellule nerveuse ectodermique - CNEN cellule nerveuse endodermique - CNM cellule nerveuse mésogléenne - COL colonne - CSP cellule spumeuse - CSPH cellule sphéruleuse - CU cellule urticante - D dépot de matériel intercellulaire (zonula adhaerens) - DS desmosome septé - ECT ectoderme - EE empilement d'ergastoplasme rappelant un corps de Nissl - FF fibres fasciculées h structure - G glycogène - GA granule aréolé - IC inclusion crênelée - M mitochondrie - MB membrane basale - ME mésoglée - MES lame mésentériale - MF microfilament - MT figure interprétée on terme de microtubule - MV microvilli - N noyau - E neurite - NO nodosité - P pédoncule - PC paroi des canaux - PE perforation - R rachis - SF siphonozoïde fendu - SIPH siphonozoïde - SM sipment musculaire d'une cellule myoépithéliale - T travé ous-siphonozoïdale - TME travée mésogléenne - VC vésicule claire - VME vésicule mésenchymateuse - ZI zône intermédiaire - I synapse polarisée - 2 synapse réciproque - 3 figure ressemblant à un desmosome septé - 4 contact par apposition Cc travail correspond à la première partie d'une thèse de Doctorat d'Etat, consacrée aux «Structures et aux mécanismes de l'intégration dans la colonie de Veretillum cynomoriurra» — Il a été effectué au sein de l'Equipe de Recherche Associée au C.N.R.S., n°183 (Directeur Al. Pavans de Ceccatty) avec le concours du Laboratoire Arago à Banyuls sur Mer (France) et la collaboration technique de Madame J. Villeneuve.  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