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961.
962.
Jonas Boström Valera Veryazov Francesco Aquilante Thomas Bondo Pedersen Roland Lindh 《International journal of quantum chemistry》2014,114(5):321-327
An algorithm for computing analytical gradients of the second‐order Møller–Plesset (MP2) energy using density fitting (DF) is presented. The algorithm assumes that the underlying canonical Hartree–Fock reference is obtained with the same auxiliary basis set, which we obtain by Cholesky decomposition (CD) of atomic electron repulsion integrals. CD is also used for the negative semidefinite MP2 amplitude matrix. Test calculations on the weakly interacting dimers of the S22 test set (Jure?ka et al., Phys. Chem. Chem. Phys. 2006, 8, 1985) show that the geometry errors due to the auxiliary basis set are negligible. With double‐zeta basis sets, the error due to the DF approximation in intermolecular bond lengths is better than 0.1 pm. The computational time is typically reduced by a factor of 6–7. © 2013 Wiley Periodicals, Inc. 相似文献
963.
964.
The synthesis of a new derivative of tryptophan Fmoc-Trp(Boc-Sar-Sar)-OH is described. Fmoc-Trp(Boc-Sar-Sar)-OH is introduced into peptides by solid-phase peptide synthesis and during treatment with TFA at the end of the synthesis, the Boc group is cleaved and the peptide is obtained with the indole nucleus modified with the sarcosinyl-sarcosinyl (Sar-Sar) moiety. This modification will introduce a cationic charge that improves the solubility of the peptide during HPLC purification. The Sar-Sar moiety is cleaved upon exposure to physiological pH. The Boc-Sar-Sar group might, therefore, also find use in the design of pro-drugs of indole-containing compounds. 相似文献
965.
Sami-Pekka Hirvonen Mikko Mänttäri Valter Wigren Mikko Salomäki Carita Kvarnström Heikki Tenhu 《Colloid and polymer science》2011,289(9):1065-1072
Poly(benzimidazobenzophenanthroline) (BBL) was prepared according to literature method and modified with poly(ethylene oxide)
in a one pot synthesis. After precipitation in aqueous sodium carbonate solution and subsequent purification, aqueous dispersions
were prepared by ultrasonication. Particle sizes in the dispersions ranged from few tens of nanometers to several micrometers
and most of the particles had sizes of 50–250 nm. Further studies indicated that the colloidal stability is a combined result
of steric stabilization caused by excluded volume interactions of PEO chains on particle surface and electrostatic stabilization
by the dissociated carboxylic acid groups on the particle surface. The product could be processed into uniform films 20–30 nm
in thickness by spin coating onto gold-plated silicon substrates having aminethiol monolayer as the top most layer. 相似文献
966.
Fall AB Lindström SB Sundman O Ödberg L Wågberg L 《Langmuir : the ACS journal of surfaces and colloids》2011,27(18):11332-11338
Cellulose nanofibrils constitute an attractive raw material for carbon-neutral, biodegradable, nanostructured materials. Aqueous suspensions of these nanofibrils are stabilized by electrostatic repulsion arising from deprotonated carboxyl groups at the fibril surface. In the present work, a new model is developed for predicting colloidal stability by considering deprotonation and electrostatic screening. This model predicts the fibril-fibril interaction potential at a given pH in a given ionic strength environment. Experiments support the model predictions that aggregation is induced by decreasing the pH, thus reducing the surface charge, or by increasing the salt concentration. It is shown that the primary mechanism for aggregation upon the addition of salt is the surface charge reduction through specific interactions of counterions with the deprotonated carboxyl groups, and the screening effect of the salt is of secondary importance. 相似文献
967.
Sarı MM Armutcu C Bereli N Uzun L Denizli A 《Colloids and surfaces. B, Biointerfaces》2011,84(1):140-147
Affinity adsorption technique is increasingly used for protein purification, separation and other biochemical applications. Therapeutic molecules such as antibodies, cytokines, therapeutic DNA and plasma proteins must be purified before characterization and utilization. The aim of this study was to prepare micronsized spherical polymeric beads and to investigate the extent of their human insulin adsorption capability. Monosize poly(ethylene glycol dimethacrylate-N-methacryloyl-(L)-histidine) [poly(EDMA-MAH)] beads were prepared by modified suspension copolymerization. Functional monomer (MAH) was synthesized using methacryloyl chloride and L-histidine. The beads were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, swelling test and elemental analysis. MAH incorporation into monosize polymeric beads, having an average size around 2-3 μm, was estimated as 55.3 μmol MAH/g bead. Equilibrium swelling ratios of poly(EDMA-MAH) and poly(EDMA) beads were 65% and 55%, respectively. Adsorption experiments were performed under different conditions (i.e., pH, temperature, protein concentration and ionic strength). It was found that adsorption characteristics are strongly depend on these conditions. Maximum insulin adsorption capacity was achieved as 24.7 mg insulin/g poly(EDMA-MAH) beads. Results were well fitted to the Langmuir isotherm model. Compared with poly(EDMA-MAH), nonspecific insulin adsorption onto poly(EDMA) beads was very low (0.61 mg insulin/g bead) and can be negligible. It was observed that insulin could be repeatedly adsorbed and desorbed (at least 10 times) without significant loss in adsorption capacity. 相似文献
968.
Two novel silver(I) complexes, namely [Ag2(μ3-sac)2(μ-nmpen)]n (1) and [Ag(sac)(mpr)]2 (2) (sac = saccharinate; nmpen = N-methyl-1,3-propanediamine; mpr = 2-methyl-1-pyrroline) have been synthesized and characterized by IR spectra, thermal (TG, DTG and DTA) analysis and single crystal X-ray diffraction techniques. Complexes crystallize in the monoclinic system with the space group C2/c and P21/c, respectively. In 1, Ag(I) ion exhibits a distorted tetrahedral geometry by tridentate μ3-bridging sac and μ2-bridging nmpen ligands. The sac ligand exhibits a new μ3-coordination mode by means of μ2-bridging O atom of sulfonyl group and N atom of imino group. Furthermore, complex 1 exhibits a two-dimensional polynuclear structure. In 2, the silver(I) ion is linearly coordinated by the N atoms of a sac and a mpr ligands, forming mononuclear species. The individual molecules are linked into dimers by Ag···Csac (η1) interactions between silver(I) ion and phenyl ring of the adjacent complex and these dimers are assembled into two-dimensional layered networks through weak Ag···Ag (3.507 Å), SO···Ag (2.961 Å) and π···π interactions. The most interesting structural features of complexes is the presence of obvious C-H···M hydrogen-bonding interactions between the Ag centers and H atoms of nmpen or mpr ligands. 相似文献
969.
Tommy Sonne Alstrøm Mads Peter Sørensen Niels Falsig Pedersen Søren Madsen 《Acta Appl Math》2011,115(1):63-74
The time-dependent Ginzburg-Landau equation is solved numerically for type-II superconductors of complex geometry using the
finite element method. The geometry has a marked influence on the magnetic vortex distribution and the vortex dynamics. We
have observed generation of giant vortices at boundary defects, suppressing the superconducting state far into the superconductor. 相似文献
970.