全文获取类型
收费全文 | 8145篇 |
免费 | 638篇 |
国内免费 | 211篇 |
专业分类
8994篇 |
出版年
2023年 | 59篇 |
2022年 | 112篇 |
2021年 | 217篇 |
2020年 | 166篇 |
2019年 | 221篇 |
2018年 | 308篇 |
2017年 | 286篇 |
2016年 | 367篇 |
2015年 | 371篇 |
2014年 | 416篇 |
2013年 | 553篇 |
2012年 | 523篇 |
2011年 | 509篇 |
2010年 | 429篇 |
2009年 | 353篇 |
2008年 | 422篇 |
2007年 | 382篇 |
2006年 | 333篇 |
2005年 | 311篇 |
2004年 | 315篇 |
2003年 | 334篇 |
2002年 | 287篇 |
2001年 | 251篇 |
2000年 | 214篇 |
1999年 | 141篇 |
1998年 | 74篇 |
1997年 | 94篇 |
1996年 | 44篇 |
1995年 | 49篇 |
1994年 | 51篇 |
1993年 | 41篇 |
1992年 | 62篇 |
1991年 | 60篇 |
1990年 | 63篇 |
1989年 | 56篇 |
1988年 | 51篇 |
1987年 | 27篇 |
1986年 | 22篇 |
1985年 | 40篇 |
1984年 | 41篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 17篇 |
1980年 | 24篇 |
1979年 | 27篇 |
1978年 | 28篇 |
1977年 | 21篇 |
1976年 | 24篇 |
1974年 | 18篇 |
1970年 | 20篇 |
排序方式: 共有8994条查询结果,搜索用时 0 毫秒
81.
Fleur E van de Geijn Manfred Wuhrer Maurice HJ Selman Sten P Willemsen Ya?l A de Man André M Deelder Johanna MW Hazes Radboud JEM Dolhain 《Arthritis research & therapy》2009,11(6):R193
Introduction
Improvement of rheumatoid arthritis (RA) during pregnancy has been causatively associated with increased galactosylation of immunoglobulin G (IgG) N-glycans. Since previous studies were small, did not include the postpartum flare and did not study sialylation, these issues were addressed in the present study. 相似文献82.
83.
Barrionuevo P Delpino MV Velásquez LN García Samartino C Coria LM Ibañez AE Rodríguez ME Cassataro J Giambartolomei GH 《Microbes and infection / Institut Pasteur》2011,13(3):239-250
The strategies that allow Brucella abortus to persist for years inside macrophages subverting host immune responses are not completely understood. Immunity against this bacterium relies on the capacity of IFN-γ to activate macrophages, endowing them with the ability to destroy intracellular bacteria. We report here that infection with B. abortus down-modulates the expression of the type I receptor for the Fc portion of IgG (FcγRI, CD64) and FcγRI-restricted phagocytosis regulated by IFN-γ in human monocytes/macrophages. Both phenomena were not dependent on bacterial viability, since they were also induced by heat-killed B. abortus (HKBA), suggesting that they were elicited by a structural bacterial component. Accordingly, a prototypical B. abortus lipoprotein (L-Omp19), but not its unlipidated form, inhibited both CD64 expression and FcγRI-restricted phagocytosis regulated by IFN-γ. Moreover, a synthetic lipohexapeptide that mimics the structure of the protein lipid moiety also inhibited CD64 expression, indicating that any Brucella lipoprotein could down-modulate CD64 expression and FcγRI-restricted phagocytosis. Pre-incubation of monocytes/macrophages with anti-TLR2 mAb blocked the inhibition of the CD64 expression mediated by HKBA and L-Omp19. These results, together with our previous observations establish that B. abortus utilizes its lipoproteins to inhibit the monocytes/macrophages activation mediated by IFN-γ and to subvert host immunonological responses. 相似文献
84.
Chiakang Ho Ya Gao Danning Zheng Yanjun Liu Shengzhou Shan Bin Fang Yixuan Zhao Dingzhong Song Yifan Zhang Qingfeng Li 《Journal of cellular and molecular medicine》2019,23(8):5108-5118
Obesity and its associated metabolic disorders such as diabetes, hepatic steatosis and chronic heart diseases are affecting billions of individuals. However there is no satisfactory drug to treat such diseases. In this study, we found that alisol A, a major active triterpene isolated from the Chinese traditional medicine Rhizoma Alismatis, could significantly attenuate high‐fat‐diet‐induced obesity. Our biochemical detection demonstrated that alisol A remarkably decreased lipid levels, alleviated glucose metabolism disorders and insulin resistance in high‐fat‐diet‐induced obese mice. We also found that alisol A reduced hepatic steatosis and improved liver function in the obese mice model.In addition, protein expression investigation revealed that alisol A had an active effect on AMPK/ACC/SREBP‐1c pathway. As suggested by the molecular docking study, such bioactivity of alisol A may result from its selective binding to the catalytic region of AMPK.Therefore, we believe that Alisol A could serve as a promising agent for treatment of obesity and its related metabolic diseases. 相似文献
85.
Rendal Vázquez ME Díaz Román TM Rodríguez Cabarcos M Zavanella Botta C Domenech García N González Cuesta M Sánchez Dopico MJ Pértega Díaz S Andión Núñez C 《Cell and tissue banking》2008,9(2):101-107
To analyse the influence of cold ischemic time (CIT) (2–24 h) and of cryopreservation (liquid phase) on the viability of the
valvular fibroblasts and in the presence of apoptosis. Cardiac valves from 10 pigs were evaluated by anatomo-pathological
study of the wall, muscle and leaflet. At the same time, the presence of cellular death due to apoptosis was investigated
in two ways; directly on tissue by Apodetec system and by two-colour flow cytometry assay analyzing a suspension of fibroblast
from valve leaflets using Anexina V and propidium iodure (PI). We established three groups of samples to compare different
experimental conditions: 2 h of ischemia (group 1), 24 h of ischemia (group 2), and a programme of cryopreservation (−1°C/min)
after 2 h of ischemia, followed by storage in liquid nitrogen during a week and thawing was performed (group 3). The analysis
of viabilities showed slight differences between all three groups. The results indicated CIT of 24 h undergoing more structural
affectation than CIT of 2 h. Flow cytometry analysis did not show important differences between groups; however cryopreserved
samples (group 3) slightly less viability and a higher percentage of death by apoptosis than group 1 and 2 using flow cytometry.
Apoptosis was confirmed on tissue from all valves but mainly in samples of group 2 and group 3. In summary, the viability
of the valves in the case of ischemic times of 2 h, 24 h or after cryopreservation/thawing differs slightly. The death of
the cells is mainly mediated by necrosis and not by apoptosis. 相似文献
86.
87.
88.
Estimation of root water uptake in crops is important for making many other agricultural predictions. This estimation often
involves two assumptions: (1) that a critical soil water potential exists which is constant for a given combination of soil
and crop and which does not depend on root length density, and (2) that the local root water uptake at given soil water potential
is proportional to root length density.
Recent results of both mathematical modeling and computer tomography show that these assumptions may not be valid when the
soil water potential is averaged over a volume of soil containing roots. We tested these assumptions for plants with distinctly
different root systems. Root water uptake rates and the critical soil water potential values were determined in several adjacent
soil layers for horse bean (Vicia faba) and oat (Avena sativa) grown in lysimeters, and for field-grown cotton (Gossypium L.), maize (Zea mays) and alfalfa (Medicago sativa L.) crops. Root water uptake was calculated from the water balance of each layer in lysimeters. Water uptake rate was proportional
to root length density at high soil water potentials, for both horse bean and oat plants, but root water uptake did not depend
on root density for horse bean at potentials lower than −25 kPa. We observed a linear dependency of a critical soil water
potential on the logarithm of root length density for all plants studied. Soil texture modified the critical water potential
values, but not the linearity of the relationship. B E Clothier Section editor 相似文献
89.
S. Ya. Reznik T. Ya. Umarova N. D. Voinovich 《Entomologia Experimentalis et Applicata》1997,82(2):153-157
Trichogramma principium Sug. & Sor. females were sequentially offered two portions of the grain moth (Sitotroga cerealella Oliv.) eggs, either young (1-day old) or old (eggs that had developed 6 days at a temperature of 20 °C). The probability of host acceptance depended not only on current host age, but also on the age of the previously offered host. Particularly, Trichogramma females more often oviposited in old host eggs when previously offered young eggs (35–45% of Trichogramma females laid eggs) compared to females which were sequentially offered two portions of old eggs (15–20% of Trichogramma females laid eggs). In other words, parasitization by Trichogramma was stable even when transferred from young (preferred) to old (usually rejected) eggs. Dissections showed that refusing females had significantly more mature eggs than ovipositing females, independent of host age. Among ovipositing females, wasps provided with young hosts had fewer mature ovarial eggs than wasps provided with old hosts. Supposedly, Trichogramma females offered old hosts require a higher motivation to oviposit and have a correspondingly higher egg load than females offered young (preferred) hosts. 相似文献
90.
Hasegawa M Fujimoto Y Lucas PC Nakano H Fukase K Núñez G Inohara N 《The EMBO journal》2008,27(2):373-383
Nod1 and Nod2 are intracellular proteins that are involved in host recognition of specific bacterial molecules and are genetically associated with several inflammatory diseases. Nod1 and Nod2 stimulation activates NF-kappaB through RICK, a caspase-recruitment domain-containing kinase. However, the mechanism by which RICK activates NF-kappaB in response to Nod1 and Nod2 stimulation is unknown. Here we show that RICK is conjugated with lysine-63-linked polyubiquitin chains at lysine 209 (K209) located in its kinase domain upon Nod1 or Nod2 stimulation and by induced oligomerization of RICK. Polyubiquitination of RICK at K209 was essential for RICK-mediated IKK activation and cytokine/chemokine secretion. However, RICK polyubiquitination did not require the kinase activity of RICK or alter the interaction of RICK with NEMO, a regulatory subunit of IkappaB kinase (IKK). Instead, polyubiquitination of RICK was found to mediate the recruitment of TAK1, a kinase that was found to be essential for Nod1-induced signaling. Thus, RICK polyubiquitination links TAK1 to IKK complexes, a critical step in Nod1/Nod2-mediated NF-kappaB activation. 相似文献