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991.
Unlike the common high temperature pyrolysis of carboxymethylcellulose (CMC) targeting activated carbon, this study investigates the pyrolytic behaviour of plain CMC at low temperatures ranging between 260 and 300 °C. Preliminary experiments were conducted using differential scanning calorimetry to define the temperature range necessary for the process. Low-temperature pyrolysis was then simulated using thermogravimetric analysis under inert atmosphere. Investigations reveal that a minimum holding temperature of 260 °C is required for an isothermal process, at which pyrolysis is terminated after around 26 min. Increasing exposure temperature reduces pyrolysis time. Within the range of the investigated sample and CMC particle size, no significant effects could be measured regarding the decomposition behaviour. The resulting char was further analysed using X-ray diffraction and Fourier transform infrared spectroscopy. Visual inspection was conducted using scanning electron microscopy. Upon pyrolysis, originally longitudinally shaped CMC was found to be converted into spherical particles of functionalised amorphous carbon with an average particle size of 41 µm. 相似文献
992.
Nada M. Mostafa Mohamed L. Ashour Omayma A. Eldahshan 《Natural product research》2016,30(18):2093-2100
A novel biflavonoid [kaempferol (6→8″) apigenin] was isolated from the leaves of Jacaranda acutifolia. The structure was elucidated based on chemical evidence, 1D and 2D spectroscopic analyses as well as spectrometric techniques. The compound showed promising cytotoxic activity against breast cancer cell line MCF-7. The anticancer activity was explained via virtual docking of the isolated compound to the main sites in the human cyclin-dependent kinase2 (CDK2) crystal structure. 相似文献
993.
Mamdouh Nabil Samy Ashraf Nageeb El-Sayed Hamed Sachiko Sugimoto Hideaki Otsuka Mohamed Salah Kamel 《Natural product research》2016,30(8):967-972
A new lignan glucoside, officinalioside (1), was isolated from n-BuOH fraction of the aerial parts of Borago officinalis L., together with four known compounds: actinidioionoside (2), roseoside (3), crotalionoside C (4) and kaempferol 3-O-β-D-galactopyranoside (5). The structure of the new compound was established by means of spectroscopic and chemical analyses. Compounds 1 and 2 showed a moderate DPPH radical scavenging activity (IC50: 52.6 ± 1.70 and 41.3 ± 0.25 μM, respectively) comparable with that of the standard trolox (16.6 ± 2.2 μM) without any significant cytotoxicity towards human cell line A549 (IC50 > 100 μM). 相似文献
994.
Terrenolide S, a new butenolide derivative (6), together with six known compounds: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), stigmasta-4,6,8(14),22-tetraen-3-one (3), terretonin A (4), terretonin (5) and butyrolactone VI (7) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were established by extensive spectroscopic analyses (1D, 2D NMR and HRESIMS), as well as optical rotation measurement and comparison with literature data. Compound 1 displayed a potent activity towards methicillin-resistant Staphylococcus aureus (MRSA) and Cryptococcus neoformans with IC50 values of 2.29 and 10.68 µM, respectively. Moreover, 1, 2 and 6 exhibited antileishmanial activity towards Leishmania donovani with IC50 values of 11.24, 15.32 and 27.27 µM, respectively and IC90 values of 14.68, 40.56 and 167.03 µM, respectively. 相似文献
995.
In this paper, we consider the solution to Wente's problem with the fractional Laplace operator (?Δ)α/2, where 0 < α < 2. We derive a Wente‐type inequality for this problem. Next, we compute the optimal constant in such inequality. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
996.
Mohamed Amine Bencheikh Le Hocine Salah Boulaaras Mohamed Haiour 《Numerical Functional Analysis & Optimization》2016,37(1):1-18
In this article, an optimal error estimate for parabolic variational inequalities is studied. Existence and uniqueness of the solution is provided by the introduction of a constructive algorithm. An optimally L∞-asymptotic behavior in uniform norm is proved using the semi-implicit time scheme combined with the finite element spatial approximation. The approach is based on the concept of subsolutions. 相似文献
997.
We discuss the representability almost everywhere (a.e.) in C of an irreducible algebraic function as the Cauchy transform of a signed measure supported on a finite number of compact semi-analytic curves and a finite number of isolated points. This brings us to the study of trajectories of the particular family of quadratic differentials A(z ? a)(z ? b)×(z ? c)?2 dz2. More precisely, we give a necessary and sufficient condition on the complex numbers a and b for these quadratic differentials to have finite critical trajectories. We also discuss all possible configurations of critical graphs. 相似文献
998.
Attia MI Güclü D Hertlein B Julius J Witt-Enderby PA Zlotos DP 《Organic & biomolecular chemistry》2007,5(13):2129-2137
A structure for the self-condensation product of 2-(1H-indol-2-yl)ethyl tosylate 2a, previously proposed as 6,7,14,15-tetrahydro-15aH-azocino[1,2-a:6,5-b]diindole 3a, was revised based on the (13)C-2D-INADEQUATE experiment, and proved to be 7,7a,13,14-tetrahydro-6H-cyclobuta[b]pyrimido[1,2-a:3,4-a']diindole 4a. A mechanism for the unexpected formation of this novel hexacyclic heterocycle was proposed and its NMR solution structure was elucidated. Five derivatives of the title ring skeleton 12-16 designed as melatonin receptor ligands were synthesized and their affinities for the human MT(1) and MT(2) receptors were determined. Both butyramides 13 and 15, as well as the non-methoxy acetamide 12 exhibited micromolar binding affinities for both receptors being slightly MT(2) selective. The methoxy acetamide 14 showed the best pharmacological profile exhibiting a five times higher affinity for MT(1) (K(i) = 49 nM) than for MT(2) (K(i) = 246 nM) receptor. 相似文献
999.
A stereoselective synthesis of heavily functionalized six-membered ring subunits, which possess functionality at sites appropriate for further elaboration, is described. The cyclopentanone moiety of hydrindenediol is required to achieve total facial selectivity during the pre-domino installation of the second quaternary center, while oxidative cleavage is responsible for the ring-expanding rearrangement. A microwave-assisted version of the key domino transformation and a test of concept approach toward the iridal core structure are also presented. 相似文献
1000.
Mothi Mohamed Ebrahim Antonia Neels Helen Stoeckli-Evans Krishnaswamy Panchanatheswaran 《Polyhedron》2007
The reaction of mercury(II) halides with 1,2-bis(diphenylphosphino)ethane monoxide (dppeO) in 1:1 molar ratio yielded P,O-coordinated polymers having the empirical formula [HgX2(dppeO)]n [X = Cl (1), Br (2), I (3)]. In contrast, the reaction between the same reactants in a 1:2 molar ratio yielded the P, P-coordinated monomeric complexes, HgX2(dppeO)2[X = Cl (4), Br (5), I (6)]. The structures of 2, 3, 4 and 5 have been characterized crystallographically. The results indicate that the geometry around the mercury atom in each of these molecules is tetrahedral with considerable distortion. The 31P NMR spectra of the 1:1 complexes indicate the dissociation of the Hg–O bond in solution. 相似文献