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971.
Both in New Zealand and Chile there exist important forest industries based mostly on pine plantations. The management of harvesting requires a series of activities such as building access roads, harvesting with skidders on flat terrain and cable logging for steep terrain, transportation from forest origins to destinations, such as a port, pulp plant and sawmills.These harvesting activities imply some potentially harmful environmental impacts such as water sedimentation, erosion and loss of scenic beauty. This has led to the proposal of several mitigating actions, such as creating riparian strips along rivers, avoiding the use of heavy machinery on fragile soils and minimizing road building.The degree of implementation of these mitigating actions differs in Chile and New Zealand. In New Zealand, the 1991 Resource Management Act regulated the implementation of environmental protection measures. In Chile a series of such measures have been implemented, but a set of definite regulations has not been defined yet and there is a need to develop an economic evaluation of the implementation of environmental measures in terms of reduced timber production and high harvesting costs, together with the benefits to the environment. To support decisions at tactical and operational levels, mathematical models have been developed both in Chile and New Zealand and are being used successfully by the timber industries. These models can be modified to consider diverse environmental protection measures. We analyze the implementation of these modifications and how the new models can help evaluate the economic impact of the protection measures. We show some preliminary results.  相似文献   
972.
Novel corrugated horn have been modelled, manufactured and measured which give low-sidelobe patterns required by CMB Anisotropy experiments. These horns have a Back-to-Back structure with mode filtering at their centres. They are corrugated to give axial symmetric low-sidelobe patterns, profiled to reduce their length, and have a Gaussian flare at their entrance apertures to further suppress sidelobes to -40dB. Modelling and experimental results show excellent agreement to well below 50 dB.  相似文献   
973.
Due to its importance as a model for naturally occurring iron(III) siderophores such as desferriox­amine B, the crystal structure of the title compound, [Fe(C7H6NO2)3]·3H2O, which was reported previously (R = 0.12, one of water mol­ecules disordered), has been redetermined (R = 0.041 without disorder). The complex has pseudo‐octahedral geometry around the FeIII atom, with Fe—O bond lengths ranging from 1.9689 (18) to 2.0585 (17) Å and O—Fe—O bond angles in the chelate rings of 78.01 (7), 78.83 (7) and 78.95 (7)°. There is extensive hydrogen bonding involving the water mol­ecules and the hydro­xamate ligands.  相似文献   
974.
Calculated values of the viscosity, thermal conductivity, and electrical conductivity of hydrogen and mixtures of argon and hydrogen at high temperatures are presented. Combined ordinary, pressure, temperature, and electric field diffusion coefficients are also given for the mixtures. The calculations, which assume local thermodynamic equilibrium, are performed for atmospheric pressure plasmas in the temperature range from 300 to 30,000 K. The results are compared with those of previously published studies. Generally, the agreement is reasonable; those discrepancies that exist are attributed to the improved values of some of the collision integrals used here in calculating the transport coefficients.  相似文献   
975.
Oligodeoxynucleotide conjugates 1 – 15 carrying anchoring groups such as amino, thiol, pyrrole, and carboxy groups were prepared. A post‐synthetic modification protocol was developed. In this method 2′‐deoxy‐O4‐(p‐nitrophenyl)uridine‐3‐phosphoramidite was prepared and incorporated in oligonucleotides. After assembly, the modified nucleoside was made to react with different amines carrying the anchoring groups. At the same time, protecting groups were removed to yield the desired oligonucleotide conjugates. In a second approach, amino, thiol, and carboxylic groups were introduced into the 3′‐end of the oligonucleotides by preparing solid supports loaded with the appropriate amino acids. Oligonucleotide gold conjugates were prepared and their binding properties were examined.  相似文献   
976.
977.
A synthetically simple mixed metal hydride, diisobutylaluminum borohydride [(iBu)2AlBH4], is easily generated from a 1:1 mixture of borane-dimethylsulfide (BMS) and diisobutylaluminum hydride (DIBAL). The reduction of tertiary amides using (iBu)2AlBH4 is complete within five minutes under ambient conditions and the product tertiary amines were isolated in 70–99% yields by a simple acid-base extraction. This new methodology, reported herein, works well for reduction of tertiary aliphatic and aromatic amides as well as lactams to the corresponding amines and product isolation and purification does not require column chromatography.  相似文献   
978.
Electron ionization (EI) gas chromatography/mass spectrometry (GC/MS) analysis of pentafluorobenzyl ester-trimethyl sllyl ether (PFB-TMS) derivatives of hydroxy-subshtuted fatty acids provides structural information comparable to that obtained in analysis of methyl ester-trimethyl silyl ether (Me-TMS) derivatives. Use of this derivative eliminates the need to prepare two separate derivatives, the PFB-TMS derivative for molecular weight determination by electron capture ionization (negative ions) analysis and the Me-TMS derivative for structural determination by EI GC/MS analysis. The relative abundance of fragment ions observed during EI GC/MS analysis of these derivatized unsaturated fatty acids indicates the location of the —OTMS substituents relative to double bond positions in those cases studied. The most abundant fragment ions are observed when the compound contains an unsaturation two carbon atoms removed from the —OTMS ether carbon (the β-OTMS position). The “saddle effect” observed in the GC/MS analyses of some derivatized monohy— droxy unsaturated fatty acids is suggested to be due to a thermally allowed pericyclic double bond rearrangement and indicates the presence of a conjugated diene one carbon atom removed from the —OTMS ether carbon (the α-OTMS position). The saddle effect is most prominent for fatty acids that contain additional unsaturation separated by a single methylene unit from the conjugated diene moiety.  相似文献   
979.
Product ion spectra of fifteen monoglutathione and diglutathione conjugates have been measured using activation by 6000-eV collisions with helium in the third field-free region of a four-sector tandem mass spectrometer of EBEB configuration. Fragmentation patterns in the cation spectra have been analyzed for decompositions of the glutathione moiety that would permit recognition of an unknown as a glutathione conjugate. Five spectra from an earlier study of high-energy collisional activation on a BEEB four-sector instrument have also been included in this analysis. A suite of appropriate ions was found to occur consistently, including ions of m/z 307 comprising the glutathione tripeptide and the complementary ion [MH — 307]+ or the ion radical [MH — 306]+’.  相似文献   
980.
It is proved that the maximum number of collisions among three identical hard spheres in more than one dimension is four. It is conjectured that the maximum number of collisions amongn hard spheres ind dimensions is independent ofd, provideddn-1.  相似文献   
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