全文获取类型
收费全文 | 1539篇 |
免费 | 114篇 |
国内免费 | 3篇 |
出版年
2023年 | 16篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 49篇 |
2017年 | 25篇 |
2016年 | 43篇 |
2015年 | 91篇 |
2014年 | 92篇 |
2013年 | 100篇 |
2012年 | 104篇 |
2011年 | 121篇 |
2010年 | 70篇 |
2009年 | 59篇 |
2008年 | 94篇 |
2007年 | 84篇 |
2006年 | 69篇 |
2005年 | 69篇 |
2004年 | 64篇 |
2003年 | 58篇 |
2002年 | 41篇 |
2001年 | 15篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1993年 | 4篇 |
1992年 | 18篇 |
1991年 | 22篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1983年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 11篇 |
1972年 | 8篇 |
1971年 | 6篇 |
1970年 | 7篇 |
排序方式: 共有1656条查询结果,搜索用时 15 毫秒
71.
Zvezdochkina NV Muranova LN Andrianov VV Arkhipova SS Gaĭnutdinov KhL Golubev AI Pleshchinskiĭ IN 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2004,90(11):1381-1392
Two groups of rats with different level of motor activities: high- and low-active animals, were distinguished. The blockade of dopamine receptors by haloperidol led to depression of locomotor activity in both groups of rats; in grape snails, haloperidol caused a decrease of the velocity of locomotor responses. In was found that within 5 minutes of intravenous injection of haloperidol the excitability of spinal centers of rats decreased; but in 30 minutes in started restoring. Chronic application of the preparation depressed the effect of posttetanic potentiation of H-response in gastrocnemius muscle of spinal rats. In command neurons of grape snail, chronic injections of haloperidol causes a significant hyperpolarization shift of membrane potential and an increase of threshold of the generation of action potential. It was shown that the selective pharmacological inhibition of dopaminergic system of the brain led to a decrease of excitability in some determined neurons of the snail and spinal motor centers of rats, as well as inhibited the locomotor responses both in vertebrate and in invertebrate animals. 相似文献
72.
In this report, we compared activation of NH2-terminal FLAG-labelled thrombopoietin receptor (Mpl) by anti-FLAG antibodies and by thrombopoietin (TPO). We found that anti-FLAG monoclonal antibodies M1 dimerize FLAG-labelled receptor and trigger proliferation of BaF3/FLAG-Mpl cells. In UT7/FLAG-Mpl cells, activation of the FLAG-Mpl receptor by low TPO concentrations triggered proliferation, while high concentrations triggered differentiation. Activation of FLAG-Mpl receptors in these cells by all tested concentrations of M1 antibodies induced proliferation but not differentiation. Low TPO concentrations induced similar to M1 antibodies level of Jak2, Stat3, Stat5 and Akt phosphorylation. In contrast, only TPO and not M1 antibodies activated Erks phosphorylation. Since the anti-FLAG antibodies do not react with the TPO binding site of the receptor, we hypothesize that they can trigger a distinct signal by dimerizing Mpl in a manner different from that induced by TPO. 相似文献
73.
Géraldine?Verquin Ga?lle?Fontaine Marc?Bria Elena?Zhilinskaya Edmond?Abi-Aad Antoine?Abouka?s Brigitte?Baldeyrou Christian?Bailly Jean-Luc?BernierEmail author 《Journal of biological inorganic chemistry》2004,9(3):345-353
Oxovanadium(IV) complexes of hydroxysalen derivatives have been prepared and tested as DNA reactive agents. The nuclease activity has been investigated under oxidative or reducing conditions, on the basis of the various oxidation states of vanadium: VIII, VIV and VV. In the absence of an activating agent, none of the compounds tested was able to induce cleavage of DNA, whereas in the presence of mercaptopropionic acid (MPA) or Oxone the four complexes induced DNA modifications. Under both conditions, the para-hydroxy complex was found to be the most active compound. Reaction of these salen complexes with DNA occurs essentially at guanine residues and is more efficient in the presence of Oxone than under reducing conditions. The extent of Oxone-mediated DNA oxidation by the four vanadyl complexes was clearly superior to VOSO4
and was observed without piperidine treatment. EPR studies provided information on the reactive metal-oxo species involved under each conditions and a mechanism of reaction with DNA is discussed.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00775-004-0529-0Abbreviations BPE buffer
bis-phosphate EDTA buffer
- DMPO
5,5-dimethylpyrroline
N-oxide
- DMS
dimethyl sulfate
- HFS
hyperfine structure
- Lin
linear
- MPA
3-mercaptopropionic acid
- Nck
nicked
- salen
(salicylidene)ethylenediamine
- Sc
supercoiled
- TBE buffer
tris-borate EDTA buffer
- Tris
tris(hydroxymethyl)aminomethane 相似文献
74.
A cytosolic glucosyltransferase is required for conversion of starch to sucrose in Arabidopsis leaves at night 总被引:7,自引:0,他引:7
Chia T Thorneycroft D Chapple A Messerli G Chen J Zeeman SC Smith SM Smith AM 《The Plant journal : for cell and molecular biology》2004,37(6):853-863
Maltose is exported from the Arabidopsis chloroplast as the main product of starch degradation at night. To investigate its fate in the cytosol, we characterised plants with mutations in a gene encoding a putative glucanotransferase (disproportionating enzyme; DPE2), a protein similar to the maltase Q (MalQ) gene product involved in maltose metabolism in bacteria. Use of a DPE2 antiserum revealed that the DPE2 protein is cytosolic. Four independent mutant lines lacked this protein and displayed a decreased capacity for both starch synthesis and starch degradation in leaves. They contained exceptionally high levels of maltose, and elevated levels of glucose, fructose and other malto-oligosaccharides. Sucrose levels were lower than those in wild-type plants, especially at the start of the dark period. A glucosyltransferase activity, capable of transferring one of the glucosyl units of maltose to glycogen or amylopectin and releasing the other, was identified in leaves of wild-type plants. Its activity was sufficient to account for the rate of starch degradation. This activity was absent from dpe2 mutant plants. Based on these results, we suggest that DPE2 is an essential component of the pathway from starch to sucrose and cellular metabolism in leaves at night. Its role is probably to metabolise maltose exported from the chloroplast. We propose a pathway for the conversion of starch to sucrose in an Arabidopsis leaf. 相似文献
75.
High throughput T-DNA insertion mutagenesis in rice: a first step towards in silico reverse genetics 总被引:23,自引:0,他引:23
76.
Popov VF Iunasova TN Gaĭderova LA Aksenov LA Averina OB Shitikova OIu 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》2004,(6):41-43
The work was aimed at the evaluation of the antigenic activity and reactogenicity of antirubella vaccine, manufactured by the Serum Institute of India, on the basis of the active observation of 373 children. Vaccinal reactions were registered in 8.8% of the vaccinees. Seroconversion after the injection of the vaccine was 100%. The results of the epidemiological trial demonstrated that the Indian antirubella vaccine was faintly reactogenic and had high antigenic activity. 相似文献
77.
Gataullin AG Mikhaĭlova NA Blinkova LP Romanenko EE Elkina SI Gaĭderov AA Kalina NG 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》2004,(2):91-94
The cultural, physiologo-biochemical adhesive and antagonistic properties of B. subtilis strains with good prospects for use as biotherapeutic preparations were studied. For further studies B. subtilis strain No. 1719 was chosen. In experiments on non-inbred white mice the animals were treated by the preparation Cifran used for their selective decontamination from opportunistic microflora and for the creation of the state of dysbiosis. The influence of the spore-forming microbe on the parietal microflora of the large intestine of the animals was shown. Reliable data on the changes in the number of microorganisms (CFU/ml) per 1 cm of the surface of the large intestine were established. As markers making it possible to evaluate the action of biotherapeutic and other medicinal remedies, easily determinable ratios of lac+/lac- of bacteria and Staphylococcus aureus/Staphylococcus spp. was proposed. 相似文献
78.
Gaĭnutdinova TKh Tagirova RR Ismailova AI Muranova LN Gaĭnutdinov KhL Balaban PM 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2004,54(6):795-800
We investigated influence of anisomycine injection on reconsolidation of contextual memory after development of environmental conditioned reflex in terrestrial snail Helix. Testing the amplitude of behavioral reactions (tentacle withdrawal) in response to standard tactile stimulation of the skin in two contexts: a) when the snail was fixed by the shell and was moving on the surface of the ball floating in water, or b) was moving on the flat surface of glass terrarium, has shown no difference in response amplitudes. After a session of electric shocks (5 days) in one context only (ball) the associative learning was clearly observed as the significant difference of response amplitudes in two contexts. On the other day following testing was performed a session of "reminding", immediately after which the snails were injected by anisomycine (control snails were injected by saline solution). Testing has shown that injection of anisomycine led to impairment of the context conditioning. Results suggest that the mechanisms of consolidation of new memory and memory reconsolidation after retrieval are not identical. 相似文献
79.
Eugeniusz?ParysEmail author El?bieta?Romanowska Maria?Siedlecka 《Acta Physiologiae Plantarum》2004,26(1):37-46
The respiration rate of leaves and mesophyll protoplasts of pea (Pisum sativum L.), from plants which were previously kept in darkness for 24 h was doubled following a period of photosynthesis at ambient
level of O2 (21 %), whereas the low level of O2 (1 % and 4 % for leaves and protoplasts, respectively) reduced this light-enhanced dark respiration (LEDR) to the rate as
noted before the illumination. Similarly to respiration rate, the oxygen at used concentrations had no effect on the ATP/ADP
ratio in the dark-treated leaves. However, the ATP/ADP ratio in leaves photosynthesizing at 21 % O2 was higher (up to 40 %, dependence on CO2 concentration in the range 40–1600 1 dm−3) than in those photosynthesizing at 1 % O2 or darkened at air (21 % O2). Also, at 1 % O2 the accumulation of malate was suppressed (by about 40 %), to a value noted for leaves darkened at 21 % O2. The dark-treatment of leaves reduced the ability of isolated mitochondria to oxidize glycine (by about twofold) and succinate,
but not malate. Mitochondria from both the light- and dark-treated leaves did not differ in qualitative composition of free
amino acids, however, there were significant quantitative differences especially with respect to aspartate, alanine, glutamate
and major intermediates of the photorespiratory pathway (glycine, serine). Our results suggest that accumulation of photorespiratory
and respiratory metabolites in pea leaves during photosynthesis at 1 % O2 is reduced, hence the suppression of postillumination respiration rate. 相似文献
80.
El-Sayed NM Ghedin E Song J MacLeod A Bringaud F Larkin C Wanless D Peterson J Hou L Taylor S Tweedie A Biteau N Khalak HG Lin X Mason T Hannick L Caler E Blandin G Bartholomeu D Simpson AJ Kaul S Zhao H Pai G Van Aken S Utterback T Haas B Koo HL Umayam L Suh B Gerrard C Leech V Qi R Zhou S Schwartz D Feldblyum T Salzberg S Tait A Turner CM Ullu E White O Melville S Adams MD Fraser CM Donelson JE 《Nucleic acids research》2003,31(16):4856-4863