全文获取类型
收费全文 | 15135篇 |
免费 | 1097篇 |
国内免费 | 4篇 |
专业分类
16236篇 |
出版年
2024年 | 14篇 |
2023年 | 91篇 |
2022年 | 170篇 |
2021年 | 373篇 |
2020年 | 268篇 |
2019年 | 344篇 |
2018年 | 415篇 |
2017年 | 338篇 |
2016年 | 533篇 |
2015年 | 865篇 |
2014年 | 875篇 |
2013年 | 1091篇 |
2012年 | 1318篇 |
2011年 | 1197篇 |
2010年 | 804篇 |
2009年 | 740篇 |
2008年 | 889篇 |
2007年 | 880篇 |
2006年 | 776篇 |
2005年 | 715篇 |
2004年 | 677篇 |
2003年 | 556篇 |
2002年 | 558篇 |
2001年 | 152篇 |
2000年 | 101篇 |
1999年 | 133篇 |
1998年 | 183篇 |
1997年 | 136篇 |
1996年 | 90篇 |
1995年 | 89篇 |
1994年 | 98篇 |
1993年 | 83篇 |
1992年 | 63篇 |
1991年 | 58篇 |
1990年 | 58篇 |
1989年 | 46篇 |
1988年 | 43篇 |
1987年 | 33篇 |
1986年 | 30篇 |
1985年 | 40篇 |
1984年 | 49篇 |
1983年 | 29篇 |
1982年 | 38篇 |
1981年 | 28篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
111.
Alda M Luciano JV Andrés E Serrano-Blanco A Rodero B del Hoyo YL Roca M Moreno S Magallón R García-Campayo J 《Arthritis research & therapy》2011,13(5):R173
Introduction
No randomised, controlled trials have been conducted to date on the efficacy of psychological and pharmacological treatments of pain catastrophising (PC) in patients with fibromyalgia. Our aim in this study was to assess the effectiveness of cognitive-behaviour therapy (CBT) and the recommended pharmacological treatment (RPT) compared with treatment as usual (TAU) at the primary care level for the treatment of PC in fibromyalgia patients. 相似文献112.
113.
Colmenero-Flores JM Martínez G Gamba G Vázquez N Iglesias DJ Brumós J Talón M 《The Plant journal : for cell and molecular biology》2007,50(2):278-292
Chloride (Cl(-)) is an essential nutrient and one of the most abundant inorganic anions in plant tissues. We have cloned an Arabidopsis thaliana cDNA encoding for a member of the cation-Cl(-) cotransporter (CCC) family. Deduced plant CCC proteins are highly conserved, and phylogenetic analyses revealed their relationships to the sub-family of animal K(+):Cl(-) cotransporters. In Xenopus laevis oocytes, the A. thaliana CCC protein (At CCC) catalysed the co-ordinated symport of K(+), Na(+) and Cl(-), and this transport activity was inhibited by the 'loop' diuretic bumetanide, a specific inhibitor of vertebrate Na(+):K(+):Cl(-) cotransporters, indicating that At CCC encodes for a bona fide Na(+):K(+):Cl(-) cotransporter. Analysis of At CCC promoter-beta-glucuronidase transgenic Arabidopsis plants revealed preferential expression in the root and shoot vasculature at the xylem/symplast boundary, root tips, trichomes, leaf hydathodes, leaf stipules and anthers. Plants homozygous for two independent T-DNA insertions in the CCC gene exhibited shorter organs such as inflorescence stems, roots, leaves and siliques. The elongation zone of the inflorescence stem of ccc plants often necrosed during bolt emergence, while seed production was strongly impaired. In addition, ccc plants exhibited defective Cl(-) homeostasis under high salinity, as they accumulated higher and lower Cl(-) amounts in shoots and roots, respectively, than the treated wild type, suggesting At CCC involvement in long-distance Cl(-) transport. Compelling evidence is provided on the occurrence of cation-chloride cotransporters in the plant kingdom and their significant role in major plant developmental processes and Cl(-) homeostasis. 相似文献
114.
Salinas-Tobon Mdel R Navarrete-Leon A Mendez-Loredo BE Esquivel-Aguirre D Martínez-Abrajan DM Hernandez-Sanchez J 《Experimental parasitology》2007,115(2):160-167
In this work, we analyzed the kinetics of anti-Trichinella spiralis newborn larva (NBL) antibodies (Ab) and the antigenic recognition pattern of NBL proteins and its dose effects. Wistar rats were infected with 0, 700, 2000, 4000 and 8000 muscle larvae (ML) and bled at different time intervals up to day 31 post infection (p.i.). Ab production was higher with 2000 ML dose and decreased with 8000, 4000 and 700 ML. Abs were not detected until day 10, peaked on day 14 for the 2000 ML dose and on day 19 for the other doses and thereafter declined slowly from 19 to 31 days p.i. In contrast, Abs to ML increased from day 10, peaked on day 19 and remained high until the end of the study. Abs bound strongly at least to three NBL components of 188, 205 and 49 kDa. NBL antigen of 188 and 205 kDa were recognized 10-26 days p.i. and that of 49 kDa from day 10 to day 31 p.i. A weak recognition towards antigens of 52, 54, 62 and 83 kDa was also observed during the infection. An early recognition of 31, 43, 45, 55, 68 and 85 kDa ML antigens was observed whereas the response to those of 43, 45, 48, 60, 64 and 97 kDa (described previously as TSL-1 antigens) occurred late in the infection. A follow-up of antigen recognition up to day 61 with the optimal immunization dose (2000 ML) evidenced a decline of Ab production to the 49 kDa NBL antigen 42 days p.i., which suggested antigenic differences with the previously reported 43 kDa ML antigen strongly recognized late in the infection. To analyze the stage-specificity of the 49 kDa NBL antigen, polyclonal antibodies (PoAb) were obtained in rats immunized with 49 kDa NBL antigen. PoAb reacted strongly with the 49 kDa NBL component in NBL total soluble extract but no reactivity was observed with soluble antigen of the other T. spiralis stages. Albeit with less intensity, the 49 kDa component was also recognized by PoAb together with other antigens of 53, 97 and 107 kDa, in NBL excretory-secretory products (NBL-ESP). Thus, our results reveal differences in the kinetics of anti-NBL and ML Ab responses. While anti-NBL Abs declined slowly from day 19 until the end of the experiment, Abs to ML antigen remained high in the same period. It is remarkable the optimal Ab response to NBL antigens with 2000 ML infective dose and the reduced number of NBL antigens identified throughout the experimental T. spiralis infection, standing out the immunodominant 49 kDa antigen. Interestingly, this antigen, which was prominently expressed in NBL somatic proteins, was also detected in NBL-ESP. 相似文献
115.
Yurixhi Maldonado–López Edelmira Linares–Mazari Robert Bye Guillermo Delgado Francisco J. Espinosa–García 《Economic botany》2008,62(2):161-170
Mexican Arnica Anti–Inflammatory Action: Plant Age Is Correlated with the Concentration of Anti–inflammatory Sesquiterpenes
in the Medicinal Plant
Heterotheca inuloides
Cass. (Asteraceae). Mexican árnica (Heterotheca inuloides Cass.) is a widely used anti–inflammatory medicinal plant in Mexican folk medicine. Although it has been suggested that plant
age, fertilization, and harvesting regime influence the concentration of secondary compounds affecting the therapeutic activity
of the plant, the effect of these variables on the concentration of the Mexican árnica anti–inflammatory compounds was not
known. We quantified anti–inflammatory sesquiterpenes (caryolan–1, 9β–diol, cadalen–15–oic acid, 7–hydroxycadalene, 4–hydroxy–2–isopropyl–4,
7–dimethyl–1[4H] naftalinone, 7–hydroxy–4αH–3, 4–dihydrocadalene, β–caryophyllene, and β–caryophyllene epoxide) in Mexican
árnica plants subjected to fertilization and successive harvests of flowering stems, conditions that mimic the cultivation
and harvesting for árnica in México. Fertilization and successive harvesting and their interaction had no significant effect
on the concentration of anti–inflammatory compounds. However, the concentrations of these compounds were 60% higher in flowering
stems from 15–month–old plants than in those from 4– or 8–month–old plants and was independent of the number of harvests and
fertilization regime applied. 相似文献
116.
117.
Francisco Romero Francisco Javier Caballero Francisco Castillo José Manuel Roldán 《Archives of microbiology》1985,143(2):111-116
Anti-glutamine synthetase serum was raised in rabbits by injecting purified glutamine synthetase (GS) of the phototrophic bacterium Rhodopseudomonas capsulata E1F1. The antibodies were purified to monospecificity by immunoaffinity chromatography in GS-sepharose gel. These anti-GS antibodies were used to measure the antigen levels in crude extracts from bacteria, grown phototrophically with dinitrogen, nitrate, nitrite, ammonia, glutamate, glutamine or alanine as nitrogen sources. The amount of GS detected by rocket immunoelectrophoresis was proportional to Mn2+-dependent transferase activity measured in the crude extracts. Addition of GS inhibitor l-methionine-d,l-sulfoximine (MSX) to the actively growing cells promoted increased antigen levels, that were not found in the presence of glutamine or chloramphenicol. The ammonia-induced decrease in GS relative levels was reverted by MSX. GS levels remained constant when phototrophically growing cells were kept in the dark.Abbreviations GS
glutamine synthetase
- MOPS
2-(N-morpholine) propane sulfonate
- MSX
l-methionine-d,l-sulfoximine 相似文献
118.
Francisco G. Acién Fernández Celeste Brindley Alias José A. Sánchez Pérez José M. Fernández Sevilla María J. Ibáñez González Emilio Molina Grima 《Journal of applied phycology》2003,15(2-3):229-237
An integrated process for the indoor production of 13C labelled PUFA from Phaeodactylum tricornutum is presented. The core of the process is a bubble column photobioreactor from which the exhaust gas from the reactor is returned to the culture by a low pressure compressor. To avoid accumulation of dissolved oxygen in the culture medium, the exhaust gas is bubbled through a sodium sulphite solution before returning it to the reactor. Carbon is removed from the medium before inoculating the alga, then labelled 13CO2 is injected for pH control and carbon supply. The reactor has been operated in semicontinuous mode at a dilution rate of 0.01 h–1, a biomass productivity of 0.1 g L–1 d–1 being obtained. Under this conditions both pH and dissolved oxygen were correctly controlled and the adequacy of the system for autotrophic production of labelled biomass was demonstrated. Analysis by GC-MS revealed that the fatty acids content of the biomass obtained was 10% d.wt., the content of eicosapentaenoic acid was 2.5% d.wt. All the fatty acids were labelled, more that 90% of the carbon present in these fatty acids was 13C. Element analysis of biomass and supernatant showed that 59.5% of injected carbon was assimilated into the biomass whereas 33% remained in the supernatant, and 7.5% remained undetected. Due to the high cost of 13CO2 different strategies for the optimisation of labelled carbon use are proposed. 相似文献
119.
Alves Luís Cyrne Luisa Amaral-Collaço M.T. Gírio Francisco M. 《World journal of microbiology & biotechnology》2003,19(2):201-208
Antisera against metal(Mo)-containing dye-linked dehydrogenases from sulphate-reducing bacteria were used to screen for immunological similarities with NAD+-linked dehydrogenases detected in aerobic methanol-utilizing bacterial isolates. Out of eleven strains tested, the strains #5, 8, 9 and 11 were shown to have specific formate and aldehyde dehydrogenases displaying antibody cross-reaction against highly purified Mo-containing dye-linked dehydrogenases. The apparent molecular mass of the identified proteins observed during the antibody reaction correlated with the molecular mass of the dehydrogenases obtained after native PAGE electrophoresis. The strains #8 and 11 exhibited one formate dehydrogenase apparently of identical molecular mass 140–145 kDa, whereas strains #5, 9 and 11 synthesized aldehyde dehydrogenases with apparent molecular masses of about 110, 120 and 155 kDa (two forms) and 120 kDa, respectively. All these aerobic enzymes shared antigenic properties with the anaerobic metalloproteins, indicating the existence of structural similarities between those enzymes in spite of having different cofactor moieties. 相似文献
120.
Summary. The aim of this work was to study the activity of NAD(P)H:(quinone acceptor) oxidoreductase 1 (EC 1.6.99.2) in the regeneration
of lipophilic antioxidants, alpha-tocopherol, and reduced-coenzyme Q analogs. First, we tested whether or not two isoforms
of the NAD(P)H:(quinone acceptor) oxidoreductase 1 designated as “hydrophilic” and “hydrophobic” (H. J. Prochaska and P. Talalay,
Journal of Biological Chemistry 261: 1372–1378, 1986) show differential enzyme activities towards hydrophilic or hydrophobic
ubiquinone homologs. By chromatography on phenyl Sepharose, we purified the two isoforms from pig liver cytosol and measured
their reduction of several ubiquinone homologs of different side chain length. We also studied by electron paramagnetic resonance
the effect of NAD(P)H:(quinone acceptor) oxidoreductase 1 on steady-state levels of chromanoxyl radicals generated by linoleic
acid and lipooxygenase and confirmed the enzyme's ability to protect alpha-tocopherol against oxidation induced with H2O2-Fe2+. Our results demonstrated that the different hydrophobicities of the isoforms do not reflect different reactivities towards
ubiquinones of different side chain length. In addition, electron paramagnetic resonance studies showed that in systems containing
the reductase plus NADH, levels of chromanoxyl radicals were dramatically reduced. Morever, in the presence of oxidants, alpha-tocopherol
was preserved by NAD(P)H:(quinone acceptor) oxidoreductase 1, supporting our hypothesis that regeneration of alpha-tocopherol
may be one of the physiologic functions of this enzyme.
Received May 20, 2002; accepted September 20, 2002; published online May 21, 2003
RID="*"
ID="*" Correspondence and reprints: Departamento de Biología Celular, Fisiología e Inmunología, Facultad de Ciencias, Edificio
Severo Ochoa, Campus de Rabanales, Universidad de Córdoba, 14014 Córdoba, Spain. 相似文献