全文获取类型
收费全文 | 4226篇 |
免费 | 189篇 |
国内免费 | 16篇 |
专业分类
化学 | 3463篇 |
晶体学 | 16篇 |
力学 | 67篇 |
数学 | 425篇 |
物理学 | 460篇 |
出版年
2023年 | 50篇 |
2022年 | 138篇 |
2021年 | 177篇 |
2020年 | 141篇 |
2019年 | 120篇 |
2018年 | 59篇 |
2017年 | 56篇 |
2016年 | 176篇 |
2015年 | 179篇 |
2014年 | 163篇 |
2013年 | 236篇 |
2012年 | 337篇 |
2011年 | 371篇 |
2010年 | 211篇 |
2009年 | 172篇 |
2008年 | 291篇 |
2007年 | 258篇 |
2006年 | 254篇 |
2005年 | 181篇 |
2004年 | 190篇 |
2003年 | 148篇 |
2002年 | 125篇 |
2001年 | 27篇 |
2000年 | 29篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 5篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有4431条查询结果,搜索用时 31 毫秒
11.
Farah Diab Hawraa Zbeeb Francesca Baldini Piero Portincasa Mohamad Khalil Laura Vergani 《Molecules (Basel, Switzerland)》2022,27(15)
Numerous plants, plant extracts, and plant-derived compounds are being explored for their beneficial effects against overweight and liver diseases. Obesity is associated with the increased prevalence of non-alcoholic fatty liver disease (NAFLD), becoming the most common liver disease in Western countries. Obesity and NAFLD are closely associated with many other metabolic alternations such as insulin resistance, diabetes mellitus, and cardiovascular diseases. Many herbs of the Lamiaceae family are widely employed as food and spices in the Mediterranean area, but also in folk medicine, and their use for the management of metabolic disorders is well documented. Hereby, we summarized the scientific results of the medicinal and nutraceutical potential of plants from the Lamiaceae family for prevention and mitigation of overweight and fatty liver. The evidence indicates that Lamiaceae plants may be a cost-effective source of nutraceuticals and/or phytochemicals to be used in the management of metabolic-related conditions such as obesity and NAFLD. PubMed, Google Scholar, Scopus, and SciFinder were accessed to collect data on traditional medicinal plants, compounds derived from plants, their reported anti-obesity mechanisms, and therapeutic targets. 相似文献
12.
Ivana Kekez Mihovil Faletar Mario Kekez Laura Cendron Maya Wright Giuseppe Zanotti Dubravka Matkovi-alogovi 《Molecules (Basel, Switzerland)》2022,27(11)
Within this research, the CrdA protein from Helicobacter pylori (HpCrdA), a putative copper-binding protein important for the survival of bacterium, was biophysically characterized in a solution, and its binding affinity toward copper was experimentally determined. Incubation of HpCrdA with Cu(II) ions favors the formation of the monomeric species in the solution. The modeled HpCrdA structure shows a conserved methionine-rich region, a potential binding site for Cu(I), as in the structures of similar copper-binding proteins, CopC and PcoC, from Pseudomonas syringae and from Escherichia coli, respectively. Within the conserved amino acid motif, HpCrdA contains two additional methionines and two glutamic acid residues (MMXEMPGMXXMXEM) in comparison to CopC and PcoC but lacks the canonical Cu(II) binding site (two His) since the sequence has no His residues. The methionine-rich site is in a flexible loop and can adopt different geometries for the two copper oxidation states. It could bind copper in both oxidation states (I and II), but with different binding affinities, micromolar was found for Cu(II), and less than nanomolar is proposed for Cu(I). Considering that CrdA is a periplasmic protein involved in chaperoning copper export and delivery in the H. pylori cell and that the affinity of the interaction corresponds to a middle or strong metal–protein interaction depending on the copper oxidation state, we conclude that the interaction also occurs in vivo and is physiologically relevant for H. pylori. 相似文献
13.
Daniel Koch Massimiliano Cutugno Samuel Karlson Saahil Patel Laura Wessing Paul M. Alsing 《Entropy (Basel, Switzerland)》2022,24(7)
We study an oracle operation, along with its circuit design, which combined with the Grover diffusion operator boosts the probability of finding the minimum or maximum solutions on a weighted directed graph. We focus on the geometry of sequentially connected bipartite graphs, which naturally gives rise to solution spaces describable by Gaussian distributions. We then demonstrate how an oracle that encodes these distributions can be used to solve for the optimal path via amplitude amplification. And finally, we explore the degree to which this algorithm is capable of solving cases that are generated using randomized weights, as well as a theoretical application for solving the Traveling Salesman problem. 相似文献
14.
Chenlin Feng Xuesong Wang Willem Jespers Rongfang Liu Sofía Denise Zamarbide Losada Marina Gorostiola Gonzlez Gerard J. P. van Westen Erik H. J. Danen Laura H. Heitman 《Molecules (Basel, Switzerland)》2022,27(15)
The adenosine A2A receptor (A2AAR) is a class A G-protein-coupled receptor (GPCR). It is an immune checkpoint in the tumor micro-environment and has become an emerging target for cancer treatment. In this study, we aimed to explore the effects of cancer-patient-derived A2AAR mutations on ligand binding and receptor functions. The wild-type A2AAR and 15 mutants identified by Genomic Data Commons (GDC) in human cancers were expressed in HEK293T cells. Firstly, we found that the binding affinity for agonist NECA was decreased in six mutants but increased for the V275A mutant. Mutations A165V and A265V decreased the binding affinity for antagonist ZM241385. Secondly, we found that the potency of NECA (EC50) in an impedance-based cell-morphology assay was mostly correlated with the binding affinity for the different mutants. Moreover, S132L and H278N were found to shift the A2AAR towards the inactive state. Importantly, we found that ZM241385 could not inhibit the activation of V275A and P285L stimulated by NECA. Taken together, the cancer-associated mutations of A2AAR modulated ligand binding and receptor functions. This study provides fundamental insights into the structure–activity relationship of the A2AAR and provides insights for A2AAR-related personalized treatment in cancer. 相似文献
15.
16.
In this paper, it is considered the inverse kinematics problem, which is faced from a differential point of view. In particular, it is shown that an asymptotic inverse kinematics can be interpreted as a Lie symmetry of the direct kinematics. A parameterization of all Lie symmetries of the direct kinematics is proposed, and the classical Newton and gradient method are obtained as particular cases. 相似文献
17.
This work concerns the nature of chaotic dynamical processes. Sheldon Newhouse wrote on dynamical processes (depending on a parameter )x
x+1=T(x
n
; ), wherex is in the plane, such as might arise when studying Poincaré return maps for autonomous differential equations in IR3. He proved that if the system is chaotic there will very often be existing parameter values for which there are infinitely many periodic attractors coexisting in a bounded region of the plane, and that such parameter values would be dense in some interval. The fact that infinitely many coexisting sinks can occur brings into question the very nature of the foundations of chaotic dynamical processes. We prove, for an apparently typical situation, that Newhouse's construction yields only a set of parameter values of measure zero.This research was supported in part by grants from the Air Force Office of Scientific Research AFOSR 81-0217, the Consiglio Nazionale delle Ricerche-Comitato per le Matematiche, and the National Science Foundation DMS 84-19110On leave from: Dipartimento di Matematica G. Castel nuovo Universita di Roma La Sapienza P. le Aldo Moro 5, I-00185 Rome, Italy 相似文献
18.
The use of the sequential electroless plating method allowed us to obtain the PdAgCu ternary alloy on top of dense stainless steel (SS) 316 L disks. The XRD analysis indicated that initially the nucleation of the two phases of the alloy (FCC and BCC) takes place, but the FCC/BCC ratio increases with the annealing time at 500 °C in H2 stream. After 162 h, the film contained only the FCC phase, which presents promising properties to be applied in the synthesis of hydrogen selective membranes. SEM cross-section results showed that a dense, continuous, defect-free film was deposited on top of the SS support, and the EDS data indicated that no significant gradient was present on the thickness of the film. XPS and LEIS allowed us to determine that Cu and Ag surface segregation takes place after annealing up to 500 °C/5 days. In the top-most surface layer, Ag enrichment takes place as determined by ARXPS experiments which can be the result of the lower surface tension of Ag compared to that of Cu and Pd. Increasing the annealing temperature results in an increase of the Ag surface segregation while the Cu concentration in the top-most surface layer decreases. 相似文献
19.
Laura Äkäslompolo Ana M. Sánchez Qi Hang Qin Antti Hakola Timo Kajava Sebastiaan van Dijken 《Applied Physics A: Materials Science & Processing》2013,110(4):889-894
We report on the growth of all-oxide SrRuO3/CoFe2O4/La2/3Sr1/3MnO3 and La2/3Sr1/3MnO3/CoFe2O4/SrRuO3 heterostuctures on SrTiO3(001) and MgO(001) substrates by pulsed laser deposition. Structural analyses by X-ray diffraction and transmission electron microscopy clearly indicate the preservation of epitaxial relations when the La2/3Sr1/3MnO3 layer is grown first, whereas trilayers with SrRuO3 at the bottom are more disordered. Both the substrate material and the deposition sequence strongly influence the formation of various structural defects such as interfacial dislocations and sub-grain structures, and this is clearly reflected by a reduction of the saturation magnetization in the top electrode. When the substrate material and the deposition sequence are correctly chosen, however, the magnetic moments of the La2/3Sr1/3MnO3 and SrRuO3 layers reverse independently, and the La2/3Sr1/3MnO3 layer retains bulk-like magnetic properties. 相似文献
20.
Laura Ruetsche 《Foundations of Physics Letters》1995,8(4):327-344
Modal interpretations of QM have the welcome consequence that unitarily evolved post-measurement states which superpose eigenstates of the anticipated pointer observable can represent devices registering determinate measurement outcomes. Albert and Loewer have claimed that modal interpretations cannot account for the outcomes of error-prone measurements. But Albert, Loewer, and their commentators have not always appreciated the relation of measurement error to the Albert-Loewer problem. I argue that measurement error is neither necessary nor sufficient to generate the Albert-Loewer problem, and use the Araki-Yanase theorem to show that measurements of a large class of observables, if they are error-free, are beset by the Albert-Loewer problem. 相似文献