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951.
Mónica Aguilar-Fernández Víctor J. Jaramillo Lucía Varela-Fregoso Mayra E. Gavito 《Mycorrhiza》2009,19(3):179-186
Rates of land conversion from forest to cultivated land by slash-and-burn practices are higher in tropical dry forest (TDF)
than any other Neotropical forest type. This study examined the short-term consequences of the slash-and-burn process on arbuscular
mycorrhizal fungi (AMF). We expected that slash-and-burn would reduce mycorrhizal colonization and propagules and change species
richness and composition. Soil and root samples were taken from TDF control and pasture plots originated after slash-and-burn
at four dates during the year of conversion to examine species composition, spore abundance, and infective propagules. Additionally,
spore abundance and viability and viable intraradical colonization were measured twice during the second year after conversion.
Forest and pasture plots maintained similar species richness and an overall 84% similarity during the first year after conversion.
Infective propagules were reduced in pasture plots during the first year after slash-and-burn, whereas spore abundance and
intraradical colonization remained similar in TDF and pasture plots both years of the study. Our results suggest, contrary
to the expected, that forest conversion by means of slash-and-burn followed by cultivation resulted in few immediate changes
in the AMF communities, likely because of the low heat conductivity of the soil and rapid combustion of plant residues. 相似文献
952.
Eklou-Lawson Mamy Bernard Françoise Neveux Nathalie Chaumontet Catherine Bos Cécile Davila-Gay Anne-Marie Tomé Daniel Cynober Luc Blachier François 《Amino acids》2009,37(4):751-760
The highest ammonia concentration in the body is found in the colon lumen and although there is evidence that this metabolite
can be absorbed through the colonic epithelium, there is little information on the capacity of the colonic mucosa to transfer
and metabolize this compound. In the present study, we used a model of conscious pig with a canula implanted into the proximal
colon to inject endoluminally increasing amounts of ammonium chloride and to measure during 5 h the kinetics of ammonia and
amino acid concentration changes in the portal and arterial blood. By injecting as a single dose from 1 to 5 g ammonia into
the colonic lumen, a dose-related increase in ammonia concentration in the portal blood was recorded. Ammonia concentration
remained unchanged in the arterial blood except for the highest dose tested, i.e. 5 g which thus apparently exceeds the hepatic
ureagenesis capacity. By calculating the apparent net ammonia absorption, it was determined that the pig colonic epithelium
has the capacity to absorb 4 g ammonia. Ammonia absorption through the colonic epithelium was concomitant with increase of
l-glutamine and l-arginine concentrations in the portal blood. This coincided with the expression of both glutamate dehydrogenase and glutamine
synthetase in isolated colonic epithelial cells. Since l-glutamine and l-arginine are known to represent activators for liver ureagenesis, we propose that increased portal concentrations of these
amino acids following increased ammonia colonic luminal concentration represent a metabolic link between colon mucosa and
liver urea biosynthesis. 相似文献
953.
954.
Lucía de la Torre Luz María Calvo-Irabién Carmen Salazar Henrik Balslev Finn Borchsenius 《Biodiversity and Conservation》2009,18(11):2837-2853
We analyze the relationship between palm species diversity and diversity of palm use in two areas (Amazonian Ecuador; Yucatan
Peninsula) of equivalent size but with contrasting characteristics in palm species diversity and morphology, and in the phylogenetic
composition of palm flora. The areas also differ in their cultural and socioeconomic contexts. Palm use diversity is significantly
higher in the Ecuadorian Amazon than in the Yucatan Peninsula and the lower species diversity of palms in the Yucatan Peninsula
is not matched by a more intensive use of the fewer species found there. The taxonomic composition of the palm flora is a
poor predictor of extent of use and morphological characteristics of palm species affect usefulness only in the Ecuadorian
Amazon. The Yucatecans’ more limited reliance on forest products might explain the observed patterns. Ornamental palm use
is an indicator of a general change in plant use patterns associated with tourism and macro-economic development in the Yucatan
Peninsula. We find a positive relationship between ecosystem plant diversity and plant use diversity, but socioeconomic factors
such as market integration strongly influence the use of local biodiversity. Palms represent a diverse and important natural
resource that deserves further investigation to secure its sustainable management and conservation in the two studied sites,
regardless of their degree of market integration. 相似文献
955.
956.
Biological membranes are interesting interfaces, at which important biological processes occur. In addition to integral membrane proteins, a number of proteins bind to the membrane surface and associate with it. Posttranslational lipid modification is one important mechanism, by which soluble molecules develop a propensity towards the membrane and reversibly bind to it. Membrane binding by insertion of hydrophobic lipid moieties is relevant for up to 10% of all cellular proteins. A particular interesting lipid-modified protein is the small GTPase Ras, which plays a key role in cellular signal transduction. Until recently, the structural basis for membrane binding of Ras was not well-defined. However, with the advent of new synthesis techniques and the advancement of several biophysical methods, a number of structural and dynamical features about membrane binding of Ras proteins have been revealed. This review will summarize the chemical biology of Ras and discuss in more detail the biophysical and structural features of the membrane bound C-terminus of the protein. 相似文献
957.
958.
959.
Jean-Michel Escoffre Chloé Mauroy Thomas Portet Luc Wasungu Chrystelle Rosazza Yoann Gilbart Laetitia Mallet Elisabeth Bellard Muriel Golzio Marie-Pierre Rols Justin Teissié 《Biophysical reviews》2009,1(4):185-191
Gene electrotransfer can be obtained not just on single cells in diluted suspension. For more than 10 years, this is a quasi routine strategy in tissue on the living animal and a few clinical trials have now been approved. New problems have been brought by the close contacts of cells in tissue both on the local field distribution and on the access of DNA to target cells. They need to be solved to provide a further improvement in the efficacy and safety of protein expression. There is a competition between gene transfer and cell destruction. Nevertheless, present results are indicative that electrotransfer is a promising approach for gene therapy. High level and long-lived expression of proteins can be obtained in muscles. This is used for a successful method of electrovaccination. 相似文献
960.
Elías Barquero-Calvo Raquel Conde-Alvarez Carlos Chacón-Díaz Lucía Quesada-Lobo Anna Martirosyan Caterina Guzmán-Verri Maite Iriarte Mateja Mancek-Keber Roman Jerala Jean Pierre Gorvel Ignacio Moriyón Edgardo Moreno Esteban Chaves-Olarte 《PloS one》2009,4(6)