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71.
Olivier Cohen Christine Cans Jean Louis Gilardi Hubert Roth Marie-Ange Mermet Pierre Jalbert Jacques Demongeot Martine Cuillel 《Human genetics》1996,97(5):659-667
Reciprocal translocations (rcp) are among the most common constitutional chromosomal aberrations in man. Using a European
database of 1574 families carrying autosomal rcp, a cartographic study was done on the breakpoints involved. The breakpoints
are non-randomly distributed along the different chromosomes, indicating “hot spots”. Breakpoints of rcp that result in descendants
that are unbalanced chromosomally at birth are more frequent in a distal position on chromosomal arms, and 65% of them are
localised in R-bands. Among the R-bands, bands rich in GC islands and poor in Alu repetitive sequences are more frequently
the site of breakpoints, as well as bands that include a fragile site. This result suggests that the variation in degree of
methylation in GC islands could be involved in chromosomal breakage and hence in chromosomal rearrangements.
Received: 10 April 1995 / Revised: 1 July 1995 相似文献
72.
73.
Frenette Jean-Jacques; Demers Serge; Legendre Louis; Boule Michel 《Journal of plankton research》1996,18(1):45-61
Phytoplankton photosynthetic responses were studied in two basinsof an oligotrophic lake (Québec, Canada). which are characterizedby the absence (shallow Basin 1) and presence (deeper Basin2) of seasonal thermal stratification. Size-fractionated photosynthesiswas used to characterize changes in phytoplankton characteristicsduring periods of seasonal mixing and stratification. Seasonalvariations of P max showed size-related differences, with maximumvalues in July for the picoplankton and in November for thenanoplankton. Similar patterns of variability in 相似文献
74.
Conserved function of anopheles gambiae midgut-specific promoters in the fruitfly. 总被引:1,自引:0,他引:1 下载免费PDF全文
Control of malaria by a methodology that would permit the effective blockage of the Anopheles gambiae midgut wall penetration by Plasmodium parasites requires a detailed understanding of both the physiology of the mosquito's digestion, and of the interactions between the parasite and its host. We have transformed Drosophila melanogaster with several constructs that allow the study of the promoter region of two of the major late trypsin genes of A. gambiae. Using several deletions, we have identified, for both genes, small genomic segments that are sufficient to confer tissue specificity to the promoter in a species that is far away in evolution from the mosquito. This will allow further studies that will enable both the understanding of the blood meal digestion, and may potentially be useful for the design of anti-plasmodial constructs at a later stage. 相似文献
75.
Louis I. Dublin 《Obesity (Silver Spring, Md.)》1995,3(1):107-112
The very expression “well built” has become a part of our language. It implies that persons of a particular build or structure are better coordinated or somehow can function better than other people and may, therefore, be expected to have a greater life span. Variations in the structure of individuals are marked and serve to distinguish fairly definite types. Insurance experience has crystallized into a number of fairly definite conclusions with regard to the relative longevity of certain of these types. Extremes of stature, for example, are decided handicaps. Extreme overweight and underweight carry with them increased mortality and correspondingly shorter life. Very heavy people are more likely to succumb prematurely to such conditions as diabetes, organic heart disease, renal impairment, hardening of the arteries, and very light persons, particularly at the younger ages, are more likely to develop tuberculosis. Insurance experience has confirmed the popular judgment that the individuals who approach the mean of these body measures are better able to withstand the hazards of life and to round out a fairly full expectation. 相似文献
76.
Pradip Bhatnagar William Huffman Andrew King Louis Pelus William Potts et al. 《Journal of Ornithology》1994,135(1):61-71
Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressMorphology and Physiology: Endocrinology
Subject: Endocrinology and chronobiology 相似文献77.
Abstract: The excitatory amino acid analogues l -glutamate ( l -Glu), l -aspartate ( l -Asp), d -Asp, and trans -(±)-1-amino-1,3-cyclopentanedicarboxylate ( trans -ACPD) stimulate the hydrolysis of phosphoinositides (PI). In the present studies, the effects of noncompetitive and competitive inhibitors on PI hydrolysis stimulated by excitatory amino acid analogues were examined. When agonist and inhibitor were added simultaneously to hippocampal tissue, the noncompetitive inhibitor l -2-amino-3-phosphonopropionate ( l -AP3) did not block the effects of l -Glu, l -Asp, or d -Asp at concentrations that block the effects of trans -ACPD by more than 80%. When tissue was pre-incubated with l -AP3, the effects of l -Glu, l -Asp, or d -Asp were blocked (IC50 values between 65 and 210 µ M ). Unlike l -AP3, l -aspartate-β-hydroxamate ( l -AβHA) inhibited PI hydrolysis stimulated by trans -ACPD, l -Glu, l -Asp, or d -Asp when agonist and inhibitor were added simultaneously in hippocampus; its effects were not time-dependent. In cerebellum, both l -AP3 and l -AβHA had agonist activity. Inhibition by the recently identified competitive inhibitor (+)-α-methyl-4-carboxyphenylglycine [(+)-MCPG] of PI hydrolysis was also examined. (+)-MCPG blocked PI hydrolysis stimulated by trans -ACPD, l -Asp, or d -Asp in both hippocampus and cerebellum (IC50 values between 220 and 1,700 µ M ). The effects of (+)-MCPG were consistent with a competitive mechanism of action. (+)-MCPG (up to 3 m M ) blocked PI hydrolysis stimulated by l -Glu by less than 25% in both hippocampus and cerebellum. 相似文献
78.
The effect of fire on nutrient losses and cycling in aQuercus coccifera garrigue (southern France) 总被引:1,自引:0,他引:1
Louis Trabaud 《Oecologia》1994,99(3-4):379-386
The effects of burning on plant nutrient budgets and rates of carbonic gas and particulate matter emission during fires were evaluated in aQuercus coccifera (garrigue) shrubland. Nutrient levels were determined in field-collected pre-fire vegetation and combustion residues. The losses (increased elemental transfer) were calculated as the difference between the quantity of an element in the fuel (combustible standing vegetation plus litter) before burning and that present in the postfire residues (ash). Weight losses of elements are correlated with weight losses of burnt plant biomass. The relative order of nutrient losses was: N>C>Na>Ca>P>K>Mg. Estimated losses of N, C and P from combustible plant matter exceeded 98, 97 and 79% respectively. Copious N, C and P volatilization during burning was promoted by high concentrations of these elements in foliage and fine woody biomass of the aboveground vegetation and leaf litter of the garrigue. Elements were principally removed in the smoke. The quantities of gaseous emissions of CO2, CO and particulate matter produced were estimated. 相似文献
79.
Iman Abdelmoty Fernando Albericio Louis A. Carpino Bruce M. Foxman Steven A. Kates 《Letters in Peptide Science》1994,1(2):57-67
Summary X-ray structure determinations of HBTU and HATU, well-known reagents for peptide bond formation, show that the solid-state structures of these compounds differ markedly from those commonly presented in the literature. The solid-state structures are isomers of the N,N,N',N'-tetramethyluronium salt formulation commonly written for HBTU and HATU. HBTU and HATU, obtained either directly from synthesis or from CH3CN solution, crystallize as the guanidinium N-oxide isomers. Both compounds crystallize in nearly identical conformations, despite marked differences in crystal packing. 相似文献
80.
EPR spectroscopy is a powerful tool to identify at a molecular level, the different steps of catalyst preparation, and of catalytic reactions: - the distribution among the different sites in zeolites can be determined; - the dispersion of the active phase may be appreciated; - the unsaturation degree of the active site may be evaluated using probe molecules such as water or13C enriched carbon monoxide.
- Deposition of paramagnetic transition metal ions onto a support is monitored, and the coordination sphere of the metallic center is characterized by EPR.
- The catalyst is also characterized after activation (thermal oxidation or reduction):
- The catalytic mechanisms can be investigated by studying the elementary steps of the catalytic reaction, as illustrated for methanol oxidation over Mo/SiO2 catalysts whose EPR results have extended the reaction mechanism proposed on the basis of kinetic data. In addition, reaction intermediates may be isolated inquasi-in situ conditions as in the case of olefin oligomerization catalyzed by Ni/SiO2 systems.