全文获取类型
收费全文 | 19450篇 |
免费 | 1532篇 |
国内免费 | 479篇 |
学科分类
工业技术 | 21461篇 |
出版年
2024年 | 73篇 |
2023年 | 351篇 |
2022年 | 668篇 |
2021年 | 821篇 |
2020年 | 731篇 |
2019年 | 640篇 |
2018年 | 444篇 |
2017年 | 579篇 |
2016年 | 512篇 |
2015年 | 513篇 |
2014年 | 1008篇 |
2013年 | 996篇 |
2012年 | 1501篇 |
2011年 | 1457篇 |
2010年 | 1189篇 |
2009年 | 1100篇 |
2008年 | 950篇 |
2007年 | 1250篇 |
2006年 | 1022篇 |
2005年 | 942篇 |
2004年 | 806篇 |
2003年 | 733篇 |
2002年 | 530篇 |
2001年 | 452篇 |
2000年 | 424篇 |
1999年 | 368篇 |
1998年 | 297篇 |
1997年 | 233篇 |
1996年 | 184篇 |
1995年 | 127篇 |
1994年 | 140篇 |
1993年 | 122篇 |
1992年 | 89篇 |
1991年 | 61篇 |
1990年 | 36篇 |
1989年 | 16篇 |
1988年 | 22篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Inga Baasch Christensen Lei Cheng Jonathan R. Brewer Udo Bartsch Robert A. Fenton Helle H. Damkier Jeppe Praetorius 《International journal of molecular sciences》2021,22(4)
(1) Background: The unusual accumulation of Na,K-ATPase complexes in the brush border membrane of choroid plexus epithelial cells have intrigued researchers for decades. However, the full range of the expressed Na,K-ATPase subunits and their relation to the microvillus cytoskeleton remains unknown. (2) Methods: RT-PCR analysis, co-immunoprecipitation, native PAGE, mass spectrometry, and differential centrifugation were combined with high-resolution immunofluorescence histochemistry, proximity ligase assays, and stimulated emission depletion (STED) microscopy on mouse choroid plexus cells or tissues in order to resolve these issues. (3) Results: The choroid plexus epithelium expresses Na,K-ATPase subunits α1, α2, β1, β2, β3, and phospholemman. The α1, α2, β1, and β2, subunits are all localized to the brush border membrane, where they appear to form a complex. The ATPase complexes may stabilize in the brush border membrane via anchoring to microvillar actin indirectly through ankyrin-3 or directly via other co-precipitated proteins. Aquaporin 1 (AQP1) may form part of the proposed multi-protein complexes in contrast to another membrane protein, the Na-K-2Cl cotransporter 1 (NKCC1). NKCC1 expression seems necessary for full brush border membrane accumulation of the Na,K-ATPase in the choroid plexus. (4) Conclusion: A multitude of Na,K-ATPase subunits form molecular complexes in the choroid plexus brush border, which may bind to the cytoskeleton by various alternative actin binding proteins. 相似文献
52.
Emilia Piosik Marta Ziegler-Borowska Dorota Cheminiak-Dudkiewicz Tomasz Martyski 《International journal of molecular sciences》2021,22(5)
An adsorption process of magnetite nanoparticles functionalized with aminated chitosan (Fe3O4-AChit) showing application potential in nanomedicine into cell membrane models was studied. The cell membrane models were formed using a Langmuir technique from three selected phospholipids with different polar head-groups as well as length and carbon saturation of alkyl chains. The research presented in this work reveals the existence of membrane model composition-dependent regulation of phospholipid-nanoparticle interactions. The influence of the positively charged Fe3O4-AChit nanoparticles on a Langmuir film stability, phase state, and textures is much greater in the case of these formed by negatively charged 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DPPG) than those created by zwitterionic 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC). The adsorption kinetics recorded during penetration experiments show that this effect is caused by the strongest adsorption of the investigated nanoparticles into the DPPG monolayer driven very likely by the electrostatic attraction. The differences in the adsorption strength of the Fe3O4-AChit nanoparticles into the Langmuir films formed by the phosphatidylcholines were also observed. The nanoparticles adsorbed more easily into more loosely packed POPC monolayer. 相似文献
53.
James I. Mitchell-White Thomas Stockner Nicholas Holliday Stephen J. Briddon Ian D. Kerr 《International journal of molecular sciences》2021,22(6)
The five members of the mammalian G subfamily of ATP-binding cassette transporters differ greatly in their substrate specificity. Four members of the subfamily are important in lipid transport and the wide substrate specificity of one of the members, ABCG2, is of significance due to its role in multidrug resistance. To explore the origin of substrate selectivity in members 1, 2, 4, 5 and 8 of this subfamily, we have analysed the differences in conservation between members in a multiple sequence alignment of ABCG sequences from mammals. Mapping sets of residues with similar patterns of conservation onto the resolved 3D structure of ABCG2 reveals possible explanations for differences in function, via a connected network of residues from the cytoplasmic to transmembrane domains. In ABCG2, this network of residues may confer extra conformational flexibility, enabling it to transport a wider array of substrates. 相似文献
54.
The voltage-gated proton channel, Hv1, also termed VSOP, was discovered in 2006. It has long been suggested that proton transport through voltage-gated proton channels regulate reactive oxygen species (ROS) production in phagocytes by counteracting the charge imbalance caused by the activation of NADPH oxidase. Discovery of Hv1/VSOP not only confirmed this process in phagocytes, but also led to the elucidation of novel functions in phagocytes. The compensation of charge by Hv1/VSOP sustains ROS production and is also crucial for promoting Ca2+ influx at the plasma membrane. In addition, proton extrusion into neutrophil phagosomes by Hv1/VSOP is necessary to maintain neutral phagosomal pH for the effective killing of bacteria. Contrary to the function of Hv1/VSOP as a positive regulator for ROS generation, it has been revealed that Hv1/VSOP also acts to inhibit ROS production in neutrophils. Hv1/VSOP inhibits hypochlorous acid production by regulating degranulation, leading to reduced inflammation upon fungal infection, and suppresses the activation of extracellular signal-regulated kinase (ERK) signaling by inhibiting ROS production. Thus, Hv1/VSOP is a two-way player regulating ROS production. Here, we review the functions of Hv1/VSOP in neutrophils and discuss future perspectives. 相似文献
55.
Ionically conductive polypyrrole films have been deposited at 295 K from anhydrous acetonitrile, acetonitrile/H2O and NaBF4 aqueous solutions onto platinum, mild steel and stainless steel discs, using cyclic voltammetry, potentiostatic and galvanostatic techniques. Cyclic voltammetry of the polymer films has been studied as a function of water content of the acetonitrile solvent, polypyrrole concentration and potential sweep rate. Potentiostatic growth of thicker (< 30 micron) films on stainless steel allowed free-standing polypyrrole membranes to be produced. Well adherent and conductive films were deposited at constant potential in stirred solutions from acetonitrile electrolytes containing 1% (v/v) of water. The membrane resistivity of the reduced films in 0.5 mol dm− 3 KCl(aq) at 295 K was ≈ 1 × 106 Ω cm, while the resistivity of the oxidised membrane was 2700 Ω cm. 相似文献
56.
通过两步法对聚丙烯(PP)膜进行了亲水改性:首先,通过在碱性条件下水解苯乙烯-马来酸酐共聚物(PSMA)制备了水解的苯乙烯-马来酸酐共聚物(H-PSMA);然后,以聚乙烯醇(PVA)为亲水性改性剂,戊二醛(GA)为交联剂,将H-PSMA/PVA/GA复合材料浸涂在PP基底膜上,制备了亲水性水解苯乙烯-马来酸酐共聚物/聚乙烯醇/聚丙烯(H-PSMA/PVA/PP)复合膜。利用傅里叶变换红外光谱(FT-IR)分析表征了H-PSMA和H-PSMA/PVA/GA的结构;通过测试复合膜表面的静态接触角,探究了PVA和GA含量及成膜溶液的质量浓度等对膜表面润湿性能的影响;最后,测试了复合膜的油水分离效率和重复利用率。结果表明:当GA、PVA和H-PSMA的质量比为0.225∶1∶1,成膜溶液的质量浓度为0.03 g/mL时,所制备的H-PSMA/PVA/PP复合物膜对水包油乳液(O/W)表现出优异的分离性能,初次油水分离效率为99.40%,当重复分离10次后,油水乳液的分离效率仍达到98.83%以上。该复合膜的制备工艺具有安全性好、成本低和环境友好的特点。 相似文献
57.
在粗粒料三轴试验中,橡皮膜嵌入量可造成显著的体积变形量测误差。本文针对颗粒材料的接触特点,利用Nagata Patch方法重建颗粒表面,基于重建曲面进行接触状态的判断和接触几何信息的计算,开发了高效的颗粒接触算法。该法采用dual mortar有限元方法处理颗粒与橡皮膜间的接触模拟,针对橡皮膜变形较大的特点,采用更新坐标的大变形计算格式,并根据重建的颗粒表面对颗粒-橡皮膜的距离进行几何修正,实现了颗粒-橡皮膜接触的精细化模拟,可较好地模拟计算“柔性”橡皮膜嵌入颗粒孔隙的过程。进行了Kramer钢球试验以及粗颗粒料和标准粗砂三轴试验橡皮膜嵌入过程的模拟计算,计算结果符合一般规律,与相应的试验结果吻合较好,验证了本文方法对于粗粒料膜嵌入问题的适用性。 相似文献
58.
Daniel Nedvd Petr Hoek Petr Klíma Klra Hoyerov 《International journal of molecular sciences》2021,22(7)
Cytokinins are a class of phytohormones, signalling molecules specific to plants. They act as regulators of diverse physiological processes in complex signalling pathways. It is necessary for plants to continuously regulate cytokinin distribution among different organs, tissues, cells, and compartments. Such regulatory mechanisms include cytokinin biosynthesis, metabolic conversions and degradation, as well as cytokinin membrane transport. In our review, we aim to provide a thorough picture of the latter. We begin by summarizing cytokinin structures and physicochemical properties. Then, we revise the elementary thermodynamic and kinetic aspects of cytokinin membrane transport. Next, we review which membrane-bound carrier proteins and protein families recognize cytokinins as their substrates. Namely, we discuss the families of “equilibrative nucleoside transporters” and “purine permeases”, which translocate diverse purine-related compounds, and proteins AtPUP14, AtABCG14, AtAZG1, and AtAZG2, which are specific to cytokinins. We also address long-distance cytokinin transport. Putting all these pieces together, we finally discuss cytokinin distribution as a net result of these processes, diverse in their physicochemical nature but acting together to promote plant fitness. 相似文献
59.
60.
To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 103 nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nanoclusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc., properties at the membrane-water interface is attracting increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties. 相似文献