全文获取类型
收费全文 | 1536篇 |
免费 | 34篇 |
国内免费 | 4篇 |
专业分类
化学 | 1004篇 |
晶体学 | 19篇 |
力学 | 29篇 |
数学 | 88篇 |
物理学 | 434篇 |
出版年
2024年 | 11篇 |
2023年 | 16篇 |
2022年 | 31篇 |
2021年 | 33篇 |
2020年 | 29篇 |
2019年 | 29篇 |
2018年 | 29篇 |
2017年 | 37篇 |
2016年 | 49篇 |
2015年 | 30篇 |
2014年 | 43篇 |
2013年 | 147篇 |
2012年 | 103篇 |
2011年 | 102篇 |
2010年 | 68篇 |
2009年 | 74篇 |
2008年 | 84篇 |
2007年 | 55篇 |
2006年 | 42篇 |
2005年 | 49篇 |
2004年 | 40篇 |
2003年 | 25篇 |
2002年 | 36篇 |
2001年 | 26篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 7篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 21篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有1574条查询结果,搜索用时 15 毫秒
951.
Jyotsana Pandey Kapil Dev Sourav Chattopadhyay Sleman Kadan Tanuj Sharma Rakesh Maurya Sabyasachi Sanyal Mohammad Imran Siddiqi Hilal Zaid Akhilesh Kumar Tamrakar 《Molecules (Basel, Switzerland)》2021,26(11)
Estrogenic molecules have been reported to regulate glucose homeostasis and may be beneficial for diabetes management. Here, we investigated the estrogenic effect of β-sitosterol-3-O-D-glucopyranoside (BSD), isolated from the fruits of Cupressus sempervirens and monitored its ability to regulate glucose utilization in skeletal muscle cells. BSD stimulated ERE-mediated luciferase activity in both ERα and ERβ-ERE luc expression system with greater response through ERβ in HEK-293T cells, and induced the expression of estrogen-regulated genes in estrogen responsive MCF-7 cells. In silico docking and molecular interaction studies revealed the affinity and interaction of BSD with ERβ through hydrophobic interaction and hydrogen bond pairing. Furthermore, prolonged exposure of L6-GLUT4myc myotubes to BSD raised the glucose uptake under basal conditions without affecting the insulin-stimulated glucose uptake, the effect associated with enhanced translocation of GLUT4 to the cell periphery. The BSD-mediated biological response to increase GLUT4 translocation was obliterated by PI-3-K inhibitor wortmannin, and BSD significantly increased the phosphorylation of AKT (Ser-473). Moreover, BSD-induced GLUT4 translocation was prevented in the presence of fulvestrant. Our findings reveal the estrogenic activity of BSD to stimulate glucose utilization in skeletal muscle cells via PI-3K/AKT-dependent mechanism. 相似文献
952.
Shubham Pandey Vineet Kumar Soni Ganpat Choudhary Pragati R. Sharma 《Supramolecular chemistry》2017,29(5):387-394
The present study describes non-covalent interaction and complexation behaviour of sodium ascorbate (SA) with cucurbit[6]uril (CB[6]) at neutral pH in aqueous Na2SO4 solution. The interaction behaviour is investigated using various analytical techniques like NMR, UV–Vis, fluorescence, TGA and DRS. The substantial increase in the intensity of emission and absorption spectra of sodium ascorbate is observed. The Benesi–Hildebrand evaluation method is used to determine the stoichiometry and equilibrium constant of the cucurbit[6]uril–sodium ascorbate complex, which suggested the 1:1 complex. Time-dependent 1H NMR, 13C CP MAS and CD studies also echoed non-covalent interaction between SA with CB[6]. 相似文献
953.
Kishan Chand Gupta Sumit Kumar Pandey Ayineedi Venkateswarlu 《Designs, Codes and Cryptography》2017,82(1-2):77-94
MDS matrices allow to build optimal linear diffusion layers in the design of block ciphers and hash functions. There has been a lot of study in designing efficient MDS matrices suitable for software and/or hardware implementations. In particular recursive MDS matrices are considered for resource constrained environments. Such matrices can be expressed as a power of simple companion matrices, i.e., an MDS matrix \(M = C_g^k\) for some companion matrix corresponding to a monic polynomial \(g(X) \in \mathbb {F}_q[X]\) of degree k. In this paper, we first show that for a monic polynomial g(X) of degree \(k\ge 2\), the matrix \(M = C_g^k\) is MDS if and only if g(X) has no nonzero multiple of degree \(\le 2k-1\) and weight \(\le k\). This characterization answers the issues raised by Augot et al. in FSE-2014 paper to some extent. We then revisit the algorithm given by Augot et al. to find all recursive MDS matrices that can be obtained from a class of BCH codes (which are also MDS) and propose an improved algorithm. We identify exactly what candidates in this class of BCH codes yield recursive MDS matrices. So the computation can be confined to only those potential candidate polynomials, and thus greatly reducing the complexity. As a consequence we are able to provide formulae for the number of such recursive MDS matrices, whereas in FSE-2014 paper, the same numbers are provided by exhaustively searching for some small parameter choices. We also present a few ideas making the search faster for finding efficient recursive MDS matrices in this class. Using our approach, it is possible to exhaustively search this class for larger parameter choices which was not possible earlier. We also present our search results for the case \(k=8\) and \(q=2^{16}\). 相似文献
954.
Manish K. Jaiswal Pradeep K. Muwal Shubha Pandey Pramod S. Pandey 《Tetrahedron letters》2017,58(22):2153-2156
A novel hybrid macrocyclic receptor based on bile acid and calix[4]arene has been synthesized using the α-face of the bile acid and cone-conformation of calix[4]arene. Metal recognition properties of receptor were investigated. The receptor showed the strongest affinity for Hg2+ in acetonitrile. The stoichiometry of the Receptor:Hg2+ was 1:1. 相似文献
955.
An efficient asymmetric total synthesis of phomonol 1 is presented, starting from (S)-1,2-epoxypentane. The synthesis features Sharpless asymmetric dihydroxylation (AD), diastereoselective reductive etherification and Wacker oxidation as key steps. 相似文献
956.
Anuj Nehra Khyati Pandey Saurabh Ahalawat Rajendra Prasad Joshi 《Analytical letters》2017,50(12):1897-1911
A biosensor for the determination of Escherichia coli using graphene oxide on the crystal (gold) surface was fabricated by the drop cast method. The E. coli sensing characteristics of the biosensor, such as a change in frequency, were examined by exposing the graphene oxide-coated crystal to various functionalization steps at room temperature. Graphene oxide was functionalized by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride–N-hydroxysuccinimide to covalently conjugate β-galactosidase antibodies to recognize microorganisms that produce this material. Frequency changes in the quartz crystal microbalance are dependent on the absorbed/desorbed masses of the analytes on the functional surface of the crystal. In addition, various characterization techniques were optimized for the morphological elemental analysis of the nanocoating that included field emission scanning electron microscopy, scanning electron microscopy, and electron diffraction spectroscopy. This surface was used in a quartz crystal microbalance nanoplatform for the rapid, sensitive, and label-free detection of E. coli. Under optimal conditions, the frequency of quartz crystal microbalance biosensor was directly proportional to the concentration of antigen with a dynamic range from 0.5?mg?mL?1 to 5?ng?mL?1 and a minimum detection limit of 5?ng?mL?1, and a sensitivity of 0.037?Hz?g?ml?1?cm?1. These results show that the graphene oxide-coated crystal had excellent performance for E. coli. This research reports a simple, inexpensive, and effective highly stable biosensor using graphene oxide as the sensing medium. 相似文献
957.
Kalicharan Chattopadhyay Anil Yadav Dheer Singh Anju Chopra Kavita Rai J. N. Pandey V. Kagdiyal D. Saxena 《Chromatographia》2017,80(1):145-150
A two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOFMS) method was developed for the hydrocarbon class composition analysis and benzene, toluene, ethylbenzene, and xylene (BTEX) estimation of raffinate column bottom (RCB), which is generated as a by-product from linear alkyl benzene (LAB) plants. The molecular level characterization of RCB is important to generate value-added products for the petrochemical industry. GC×GC–TOFMS was found to be an excellent tool for estimation of hydrocarbon class composition (paraffins, naphthenes, monoaromatics, diaromatics, and polyaromatic hydrocarbons) and trace level BTEX in a single run. The hydrocarbon class composition was validated with the standard method based on HPLC (ASTM D6591) and good correlation was obtained. Finally, RCB is anticipated to be a useful nonhazardous safe by-product which could be used further for generating added value. 相似文献
958.
Prashant Gahtori Rahul Pandey Vinod Kumar Surajit Kumar Ghosh Aparoop Das Jun Moni Kalita Supriya Sahu Anil Prakash Divya Ranjan Bhattacharyya 《Journal of Chemometrics》2016,30(8):462-481
The front‐line antimalarial drugs, for example, chloroquine, mefloquine, sulfadoxine, pyrimethamine, atovaquone, and artemether, are often failing because of the worldwide spread of drug‐resistant parasites. There has been significant recent interest in virtual screening to drive innovative drug discovery and to combat resistance efforts for a wide range of diseases. In fact, virtual screening has become the “gold standard” for major pharmaceutical industries and some university groups. Therefore, we present herein a structure‐based LibDock/CHARMM modeling and a set of appropriate scoring function evaluation criteria: correlation, consensus score, correlation‐based score, generally applicable replacement for root‐mean‐square deviation using a training set of 38 phenylthiazolyl‐1,3,5‐triazines from our previous reports and followed by a ligand‐based model to identify molecular features like hydrogen‐bond acceptor, hydrogen‐bond donor, hydrophobicity, and ring aromatic (RA) using Catalyst HipHop/HypoGen module. Next, TOPKAT module was applied to predict ADME‐Tox properties. The combined structure/ligand‐based approaches inadvertently arrived at a conserved Arg122 binding site from reliable LigScore1_dreiding top scoring function and are subsequently attributed to reserve important interactions and combat mutational drug resistance. The best pharmacophore model suggested that 1 hydrogen‐bond acceptor, 2 hydrophobicities, and 1 ring aromatic feature with good sensitivity at 0.50, specificity at 0.66, enrichment at 1.60, and accuracy at 0.50. Finally, good pharmacokinetics, metabolic stability, and toxicity endpoints were predicted in the comparison of proguanil and cycloguanil. These druggability insights are useful for researchers to deliver more effective, safer, both wild‐type and resistance‐compromised, and more economical dihydrofolate reductase inhibitors in the near future. 相似文献
959.
Magnetic resonance angiographic evaluation of the intracranial vasculature has been predominantly carried out using conventional angiographic techniques such as time of flight and phase contrast sequences. These techniques have good spatial resolution but lack temporal resolution. Newer faster angiographic techniques have been developed to circumvent this limitation. Elliptical centric time-resolved imaging of contrast kinetics (EC-TRICKS) is one such technique which has combined the use of elliptical centric ordering of the k-space with multiphase 3D digital subtraction MR angiogram (MRA) to achieve excellent temporal resolution of the arterial and venous circulations. Its applications have been mainly in the peripheral vasculature. We report the use of this technique in a case of a high-flow, direct carotid-cavernous fistula to demonstrate its potential in intracranial MR angiography. 相似文献
960.
Using a bond fluctuating model (BFM), Monte Carlo simulations are performed to study the film growth in a mixture of reactive hydrophobic (H) and hydrophilic (P) groups in a simultaneous reactive and evaporating aqueous (A) solution on a simple three dimensional lattice. In addition to the excluded volume, short range phenomenological interactions among each constituents and kinetic functionalities are used to capture their major characteristics. The simulation involves thermodynamic equilibration via stochastic movement of each constituent by Metropolis algorithm as well as cross-linking reaction among constituents with evaporating aqueous component. The film thickness (h) and its interface width (W) are examined with a reactive aqueous solvent for a range of temperatures (T). Results are compared with a previous study [Yang et al. Macromol. Theory Simul. 15, 263 (2006)] with an effective bond fluctuation model (EBFM). Simulation data show a much slower power-law growth for h and W with BFM than that with EBFM. With BFM, growth of the film thickness can be described by h proportionaltgamma, with a typical value gamma1 approximately 0.97 in initial time regime followed by gamma2 approximately 0.77 at T=5, for example. Growth of the interface width can also be described by a power law, W proportionaltbeta, with beta1 approximately 0.40 initially and beta2 approximately 0.25 in later stage. Corresponding values of the exponents with EBFM are much higher, i.e., gamma1 approximately 1.84, gamma2 approximately 1.34 and beta1 approximately 1.05, beta2 approximately 0.60 at T=5. Correct restrictions on the bond length with the excluded volume used with BFM are found to have a greater effect on steady-state film thickness (hs) and the interface width (Ws) at low temperatures than that at high temperatures. The relaxation patterns of the interface width with BFM seem to change noticeably from those with EBFM. A better relaxed film with a smoother surface is thus achieved by the improved cross-linking covalent bond fluctuation model which is more realistic in capturing appropriate details of systems such as polyurethane film. The steady-state film thickness increases monotonically with the temperature possibly with two logarithmic dependences. The equilibrium interface width shows a nonmonotonic dependence: on increasing the temperature, Ws seems to increase slowly before it begins to decay Ws=4.12-1.39 ln(T). 相似文献