全文获取类型
收费全文 | 4488篇 |
免费 | 358篇 |
国内免费 | 1篇 |
出版年
2023年 | 14篇 |
2022年 | 33篇 |
2021年 | 71篇 |
2020年 | 39篇 |
2019年 | 55篇 |
2018年 | 67篇 |
2017年 | 68篇 |
2016年 | 118篇 |
2015年 | 163篇 |
2014年 | 213篇 |
2013年 | 272篇 |
2012年 | 305篇 |
2011年 | 295篇 |
2010年 | 236篇 |
2009年 | 186篇 |
2008年 | 264篇 |
2007年 | 265篇 |
2006年 | 219篇 |
2005年 | 227篇 |
2004年 | 244篇 |
2003年 | 246篇 |
2002年 | 218篇 |
2001年 | 73篇 |
2000年 | 52篇 |
1999年 | 60篇 |
1998年 | 79篇 |
1997年 | 41篇 |
1996年 | 34篇 |
1995年 | 36篇 |
1994年 | 30篇 |
1993年 | 35篇 |
1992年 | 53篇 |
1991年 | 50篇 |
1990年 | 35篇 |
1989年 | 35篇 |
1988年 | 32篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1974年 | 16篇 |
1973年 | 11篇 |
1972年 | 13篇 |
1970年 | 11篇 |
排序方式: 共有4847条查询结果,搜索用时 412 毫秒
971.
Jean-Silvain Lacroix Serge Auberson Denis R. Morel Elvar Theodorsson Thomas Hkfelt Jan M. Lundberg 《Regulatory peptides》1992,40(3):373-387
By means of immunohistochemistry and radioimmunoassay (RIA), we have investigated the possible occurrence of somatostatin (SOM)-like immunoreactivity (-LI) in the autonomic innervation of the pig nasal mucosa. SOM-immunoreactive (-IR) fibres were present around nasal arteries, arterioles and venous sinusoids. Double-labelling experiments revealed that SOM-LI was co-localized with the noradrenaline (NA) markers tyrosine hydroxylase and dopamine-β-hydroxylase as well as with neuropeptide Y (NPY) in a subpopulation of neurons in the superior cervical sympathetic ganglion and in perivascular nerve terminals. Furthermore, SOM-LI was also present in perivascular fibres containing vasoactive intestinal polypeptide (VIP) and NPY of presumably parasympathetic origin. The parasympathetic fibres that were associated with glands contained peptide histidine isoleucine (PHI), VIP and NPY but not SOM, suggesting that in the nasal mucosa SOM-IR is restricted to perivascular nerves. As revealed by RIA, the content of SOM-LI in biopsies of both nasal mucosa and superior cervical sympathetic ganglion was about 12 pmol/g and the reverse phase HPLC characterisation of SOM-LI shown two separate peaks for SOM-28 and SOM-14. 相似文献
972.
973.
M Denis 《Cellular immunology》1991,134(1):42-53
Susceptible BALB/c mice were infected iv with a strain of Mycobacterium avium and infused with different biological response modifiers (BRM) in a gel delivery system so as to modify the progression of the infection in a beneficial fashion. Infusion of IL-2 or IL-4 in hydrophobic gels led to no significant enhancement of resistance. Infusion of muramyl dipeptide in hypromellose led to a significant enhancement of resistance against the M. avium, as seen by a significant reduction of colony-forming units (CFU) in the spleens of infected mice. Similarly, infusion of interleukin-1 beta in hypromellose in infected mice led to a significant reduction in CFU counts in the organs of mice. The mechanism(s) responsible for this enhanced resistance was studied further. It was found that infected mice developed profound immunosuppression, as judged by mitogenic and antigenic stimulation. Mice infused with MDP/hypromellose developed a similar immuno-suppression, suggesting that this adjuvant immunotherapy did not act by stimulating a T-cell response or by abrogating a putative suppressive phenomenon. Macrophages from mice infused with MDP alone were no more bacteriostatic for a virulent M. avium than control cells. However, macrophages from infected mice infused with MDP/hypromellose were more bacteriostatic for M. avium than cells from mice infected with M. avium and infused with the hydrophobic gel only. Overall, these results suggest that adjuvant immunotherapy is beneficial in M. avium infections. 相似文献
974.
Alice S. Denis Ophélie Payet Samuel Danflous Nicolas Gouix Frédéric Santoul Laëtitia Buisson Laurent Pelozuelo 《Journal of Insect Conservation》2018,22(3-4):419-431
Changes in phenology and in body size are two of the three main consequences of global warming on organisms. We investigated whether living in a warm artificial habitat would induce changes in the phenology and body size of dragonflies. We monitored in natura the emergence pattern of three protected and red-listed dragonfly species in three geographically close systems which differ in thermal profiles: a medium-sized river, one of its tributaries and an artificial lake fed by the water of the tributary. We also investigated the morphological variability of one of the species between the three systems. We showed an asynchrony of emergence for the three species, as well as morphological variability between the lake and the two rivers. Individuals from the lake emerged earlier and were smaller than those from the two rivers. These results are in agreement with a temperature-induced response hypothesis as the lake is warmer than the two rivers. Asynchrony of emergence between neighbouring populations triggers questions related to metapopulation functioning and about the fitness and the fate of the early-emerging individuals. Understanding the response of these species to local thermal conditions will help to improve population monitoring and conservation. 相似文献
975.
In‐line monitoring of amino acids in mammalian cell cultures using raman spectroscopy and multivariate chemometrics models
下载免费PDF全文
![点击此处可从《Engineering in Life Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hemlata Bhatia Hamidreza Mehdizadeh Denis Drapeau Seongkyu Yoon 《Engineering in Life Science》2018,18(1):55-61
The application of PAT for in‐line monitoring of biopharmaceutical manufacturing operations has a central role in developing more robust and consistent processes. Various spectroscopic techniques have been applied for collecting real‐time data from cell culture processes. Among these, Raman spectroscopy has been shown to have advantages over other spectroscopic techniques, especially in aqueous culture solutions. Measurements of several process parameters such as glucose, lactate, glutamine, glutamate, ammonium, osmolality and VCD using Raman‐based chemometrics models have been reported in literature. The application of Raman spectroscopy, coupled with calibration models for amino acid measurement in cell cultures, has been assessed. The developed models cover four amino acids important for cell growth and production: tyrosine, tryptophan, phenylalanine and methionine. The chemometrics models based on Raman spectroscopy data demonstrate the significant potential for the quantification of tyrosine, tryptophan and phenylalanine. The model for methionine would have to be further refined to improve quantification. 相似文献
976.
Molla F. Mengist Sheila Alves Denis Griffin Joanne Creedon Mike J. McLaughlin Peter W. Jones Dan Milbourne 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2018,131(4):929-945
Key message
Cd is a toxic metal, whilst Zn is an essential for plant and human health. Both can accumulate in potato tubers. We examine the genetic control of this process.Abstract
The aim of this study was to map quantitative trait loci (QTLs) influencing tuber concentrations of cadmium (Cd) and zinc (Zn). We developed a segregating population comprising 188 F1 progeny derived from crossing two tetraploid cultivars exhibiting divergent tuber-Cd-accumulation phenotypes. These progeny were genotyped using the SolCap 8303 SNP array, and evaluated for Cd, Zn, and maturity-related traits. Linkage and QTL mapping were performed using TetraploidSNPMap software, which incorporates all allele dosage information. The final genetic map comprised 3755 SNP markers with average marker density of 2.94 per cM. Tuber-Cd and Zn concentrations were measured in the segregating population over 2 years. QTL mapping identified four loci for tuber-Cd concentration on chromosomes 3, 5, 6, and 7, which explained genetic variance ranging from 5 to 33%, and five loci for tuber-Zn concentration on chromosome 1, 3, 5, and, 6 explaining from 5 to 38% of genetic variance. Among the QTL identified for tuber-Cd concentration, three loci coincided with tuber-Zn concentration. The largest effect QTL for both tuber-Cd and Zn concentration coincided with the maturity locus on chromosome 5 where earliness was associated with increased tuber concentration of both metals. Coincident minor-effect QTL for Cd and Zn sharing the same direction of effect was also found on chromosomes 3 and 6, and these were unrelated to maturity The results indicate partially overlapping genetic control of tuber-Cd and Zn concentration in the cross, involving both maturity-related and non-maturity-related mechanisms.977.
Defining the protein complexome of translation termination factor eRF1: Identification of four novel eRF1‐containing complexes that range from 20S to 57S in size
下载免费PDF全文
![点击此处可从《Proteins》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Clyde L. Denis Roy Richardson Shiwha Park Chongxu Zhang Wen Xi Thomas M. Laue Xin Wang 《Proteins》2018,86(2):177-191
The eukaryotic eRF1 translation termination factor plays an important role in recognizing stop codons and initiating the end to translation. However, which exact complexes contain eRF1 and at what abundance is not clear. We have used analytical ultracentrifugation with fluorescent detection system to identify the protein complexome of eRF1 in the yeast Saccharomyces cerevisiae. In addition to eRF1 presence in translating polysomes, we found that eRF1 associated with five other macromolecular complexes: 77S, 57S, 39S, 28S, and 20S in size. Generally equal abundances of each of these complexes were found. The 77S complex primarily contained the free 80S ribosome consistent with in vitro studies and did not appear to contain significant levels of the monosomal translating complex that co‐migrates with the free 80S ribosome. The 57S and 39S complexes represented, respectively, free 60S and 40S ribosomal subunits bound to eRF1, associations not previously reported. The novel 28S and 20S complexes (containing minimal masses of 830 KDa and 500 KDa, respectively) lacked significant RNA components and appeared to be oligomeric, as eRF1 has a mass of 49 KDa. The majority of polysomal complexes containing eRF1 were both substantially deadenylated and lacking in closed‐loop factors eIF4E and eIF4G. The thirteen percent of such translating polysomes that contained poly(A) tails had equivalent levels of eIF4E and eIF4G, suggesting these complexes were in a closed‐loop structure. The identification of eRF1 in these unique and previously unrecognized complexes suggests a variety of new roles for eRF1 in the regulation of cellular processes. 相似文献
978.
Karine Monceau Mariangela Arca Lisa Leprêtre Olivier Bonnard Gérard Arnold Denis Thiéry 《Journal of Insect Behavior》2018,31(1):1-11
Invasive species are now recognized as a major cause of native biodiversity loss worldwide. In the current deleterious context for pollinators, the invasive yellow-legged hornet, Vespa velutina, represents an additional threat to the domestic honeybee, Apis mellifera, in Europe. Therefore, understanding the impact of this predator on honeybee colonies is of major importance. In the present study, we tried to assess the impact of V. velutina on the honeybee foraging and defence behaviour based on the video monitoring of two hives. Balling behaviour is reported here for the first time under natural conditions in A. mellifera against V. velutina in Europe. Although these results are preliminary and should be carefully considered, we found that the number of hornets impacted honeybee foraging and defence behaviours. More defensive behaviours were notified in the hive, which survives slightly longer. This may suggest that selecting for more defensive colonies may provide an interesting perspective. 相似文献
979.
980.
Sergey I. Dikalov Anna E. Dikalova Denis A. Morozov Igor A. Kirilyuk 《Free radical research》2018,52(3):339-350
AbstractNitroxides are widely used in biology as antioxidants, spin labels, functional spin probes for pH, oxygen and thiol levels, and tissue redox status imaging using electron paramagnetic resonance (EPR); however, biological applications of nitroxides is hindered by fast bioreduction to EPR-silent hydroxylamines and rapid clearance. In this work, we have studied pyrrolidine nitroxides with acetoxymethoxycarbonyl groups which can undergo hydrolysis by cellular esterases to hydrophilic carboxylate derivatives resistant to bioreduction. Nitroxides containing acetoxymethoxycarbonyl groups were rapidly absorbed by cells from the media, 3,4-bis-(acetoxymethoxycarbonyl)-proxyl (DCP-AM2) and 3-(2-(bis(2-(acetoxymethoxy)-2-oxoethyl)amino)acetamido)-proxyl (DCAP-AM2) showing the strongest EPR signal of the cellular fraction. Remarkably, the EPR parameters of 3,4-dicarboxy-proxyl (DCP) and its mono- and di-acetoxymethyl esters are different, and consequent intracellular hydrolysis of acetoxymethoxycarbonyl groups in DCP-AM2 can be followed by EPR. To elucidate intracellular location of the resultant DCP, the mitochondrial fraction has been isolated. EPR measurements showed that mitochondria were the main place where DCP was finally accumulated. TEMPO derivatives showed expectedly much faster decay of EPR signal in the cellular fraction, compared to pyrrolidine nitroxides. It was found that supplementation of endothelial cells with 50?nM of DCP-AM2 completely normalised the mitochondrial superoxide level. Moreover, administration of DCP-AM2 to mice (1.4?mg/kg/day) resulted in substantial nitroxide accumulation in the tissues and significantly reduced hypertension. We found that hydroxylamine derivatives of dicarboxyproxyl nitroxide DCP-AM-H can be used for the detection of superoxide in vivo in angiotensin II model of hypertension. Infusion of DCP-AM-H in mice leads to accumulation of persistent EPR signal of nitroxide in the blood and vascular tissue in angiotensin II-infused wild-type but not in SOD2 overexpressing mice. Our data demonstrate that acetoxymethoxycarbonyl group containing nitroxides accumulate in mitochondria and demonstrate site-specific antioxidant activity. 相似文献