全文获取类型
收费全文 | 7622篇 |
免费 | 551篇 |
国内免费 | 2篇 |
出版年
2023年 | 78篇 |
2022年 | 133篇 |
2021年 | 211篇 |
2020年 | 156篇 |
2019年 | 219篇 |
2018年 | 244篇 |
2017年 | 236篇 |
2016年 | 303篇 |
2015年 | 442篇 |
2014年 | 423篇 |
2013年 | 556篇 |
2012年 | 600篇 |
2011年 | 655篇 |
2010年 | 413篇 |
2009年 | 335篇 |
2008年 | 438篇 |
2007年 | 425篇 |
2006年 | 373篇 |
2005年 | 336篇 |
2004年 | 292篇 |
2003年 | 270篇 |
2002年 | 243篇 |
2001年 | 75篇 |
2000年 | 62篇 |
1999年 | 65篇 |
1998年 | 51篇 |
1997年 | 49篇 |
1996年 | 44篇 |
1995年 | 36篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 34篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 33篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1977年 | 12篇 |
1976年 | 14篇 |
1975年 | 11篇 |
1974年 | 7篇 |
1971年 | 9篇 |
排序方式: 共有8175条查询结果,搜索用时 31 毫秒
91.
It is demonstrated that because of limitations in the magnitude of the specific activity of radiolabeled hormone derivatives, direct binding studies of hormone-receptor interactions of high affinity (10?9–10?11 M, depending on whether 3H- or 123I-labeled hormones are used) will be subject to artifactual distortions due to the need to utilize high concentrations of the receptor. If the concentration of the receptor is not ten times lower than the true affinity constant, the apparent dissociation constant obtained from direct concentration binding curves will vary as a linear function of the receptor concentration. In addition, at high receptor concentrations saturability becomes difficult to demonstrate experimentally and the binding data yield apparently non-hyperbolic, sigmoidal curves which can be mistakenly interpreted to depict cooperative interactions. Similar artifacts related to receptor concentration are predicted for measurements of the hormone concentration dependence of biological processes (e.g. activation of adenylate cyclase, transport processes, etc.). Methods for detecting these effects, and correctly measuring affinities for labeled and unlabeled hormones under these conditions, are described. The implications for measuring the binding properties of hormone-receptor interactions are discussed, especially in reference to studies of the comparative analysis of receptor function in altered metabolic states and to studies relating the biological and binding properties of hormones. 相似文献
92.
93.
Pedro Santamaria 《Molecular & general genetics : MGG》1979,172(2):161-163
Summary Heat shock of 37°C applied to Drosophila embryos at blastoderm stage induces phenocopies of some dominant mutants of the bithorax complex. Heat shock might shut down functions of cis regulator genes involved in embryonic pattern formation. 相似文献
94.
Pedro Manuel Sánchez JuradoLuis Romero Rizos María Luisa García-Mauriño GuelbenzuPedro Abizanda Soler 《Revista espa?ola de geriatría y gerontología》2011,46(1):43
A case of primary pulmonary non-Hodgkin's lymphoma is presented. On this occasion, the lymphoma invaded the myocardium, an event which has not previously been reported in the literature. These neoplasms spread by proximity, and invasion of the pericardium, thoracic wall and oesophagus have been described. Our patient died from heart failure. Tumour myocardial infiltration may well have been the determinant cause through various mechanisms, including a decrease in myocardial contractility. Spread into the myocardium may be facilitated by bulky tumour infiltrates in the pleural space. 相似文献
95.
96.
Marcos A. L. Teixeira Pedro E. Vieira Fredrik Pleijel Bruno R. Sampieri Ascensão Ravara Filipe O. Costa Arne Nygren 《Zoologica scripta》2020,49(2):222-235
We report on two new lineages of the Eumida sanguinea complex from Great Britain and describe one of them as a new species using a multilocus approach, including the mitochondrial DNA COI-5P and the nuclear markers ITS (ITS1, 5.8S rRNA and ITS2) and 28S rRNA. The molecular analysis placed Eumida mackiei sp. nov. in a monophyletic clade with 19.1% (COI), 10.1% (ITS) and 1.7% (28S) mean distance to its nearest neighbour. Molecular diagnoses were also applied to nine lineages within the E. sanguinea complex. This was complemented with morphometric data employing multivariate statistical analysis and the incorporation of statistical dissimilarities against three other described species from the complex. Eumida mackiei sp. nov. can be distinguished from E. notata and E. maia by the larger distance between the eyes and differences in morphometric proportions mainly in the dorsal and ventral cirri as well as in the prostomial appendages. E. sanguinea sensu stricto failed to produce a cluster of its own in the morphometric analysis, probably due to juvenile bias. Integrative taxonomy provided strong evidence to formally describe a new cryptic species that can now be used in biomonitoring or other relevant ecological research. 相似文献
97.
da Silva Mateus V. C. Souza Amanda B. de Castro Heizir F. Aguiar Leandro G. de Oliveira Pedro C. de Freitas Larissa 《Bioprocess and biosystems engineering》2020,43(4):615-623
Bioprocess and Biosystems Engineering - This study investigated the synthesis of 2-ethylhexyl oleate catalyzed by Candida antarctica lipase immobilized on magnetic poly(styrene-co-divinylbenzene)... 相似文献
98.
99.
Josephine Joy Hubloher Sabine Zeidler Pedro Lamosa Helena Santos Beate Averhoff Volker Müller 《Environmental microbiology》2020,22(12):5156-5166
The stress protectant trehalose is synthesized in Acinetobacter baumannii from UPD-glucose and glucose-6-phosphase via the OtsA/OtsB pathway. Previous studies proved that deletion of otsB led to a decreased virulence, the inability to grow at 45°C and a slight reduction of growth at high salinities indicating that trehalose is the cause of these phenotypes. We have questioned this conclusion by producing ∆otsA and ∆otsBA mutants and studying their phenotypes. Only deletion of otsB, but not deletion of otsA or otsBA, led to growth impairments at high salt and high temperature. The intracellular concentrations of trehalose and trehalose-6-phosphate were measured by NMR or enzymatic assay. Interestingly, none of the mutants accumulated trehalose any more but the ∆otsB mutant with its defect in trehalose-6-phosphate phosphatase activity accumulated trehalose-6-phosphate. Moreover, expression of otsA in a ∆otsB background under conditions where trehalose synthesis is not induced led to growth inhibition and the accumulation of trehalose-6-phosphate. Our results demonstrate that trehalose-6-phosphate affects multiple physiological activities in A. baumannii ATCC 19606. 相似文献
100.
Cassilda Pereira Inês S. Rodrigues Liliana M.G. Pereira Johnny Lisboa Rute D. Pinto Leonor Araújo Pedro Oliveira Roland Benz Nuno M.S. dos Santos Ana do Vale 《Cellular microbiology》2020,22(1)
Apoptosis‐inducing protein of 56 kDa (AIP56) is a major virulence factor of Photobacterium damselae subsp. piscicida, a gram‐negative pathogen that infects warm water fish species worldwide and causes serious economic losses in aquacultures. AIP56 is a single‐chain AB toxin composed by two domains connected by an unstructured linker peptide flanked by two cysteine residues that form a disulphide bond. The A domain comprises a zinc‐metalloprotease moiety that cleaves the NF‐kB p65, and the B domain is involved in binding and internalisation of the toxin into susceptible cells. Previous experiments suggested that disruption of AIP56 disulphide bond partially compromised toxicity, but conclusive evidences supporting the importance of that bond in intoxication were lacking. Here, we show that although the disulphide bond of AIP56 is dispensable for receptor recognition, endocytosis, and membrane interaction, it needs to be intact for efficient translocation of the toxin into the cytosol. We also show that the host cell thioredoxin reductase‐thioredoxin system is involved in AIP56 intoxication by reducing the disulphide bond of the toxin at the cytosol. The present study contributes to a better understanding of the molecular mechanisms operating during AIP56 intoxication and reveals common features shared with other AB toxins. 相似文献