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951.
W. Van Landuyt L. Vanhecke I. Hoste F. Hendrickx D. Bauwens 《Biodiversity and Conservation》2008,17(12):3045-3060
In large parts of Western Europe agricultural intensification after World War II has led to an increased use of fertilisers.
The resulting nutrient enrichment (=eutrophication) has a huge impact on the occurrence and distribution of plant species
and is one of the main pressures on native plant communities. We used the distribution maps (grid size: 16 km2) of individual
plant species, obtained through two consecutive survey projects (1939–1971 and 1972–2004) in Flanders (northern Belgium),
to estimate the relative change in their distribution area. The comparison of changes in range size among groups of taxa classified
according to habitat preference and Ellenberg indicator values, demonstrated a marked decline in distribution area in species
that are characteristic for nutrient-poor habitats. To assess geographic patterns in the change of species assemblages, we
calculated the mean Ellenberg N- and R-values for every grid cell during each of both survey periods. Differences between
these values were analysed in relation to soil type and estimates of atmospheric nitrogen deposition. The largest shifts in
Ellenberg N-values, reflecting a decline of species from nutrient-poor conditions and/or an increase of nitrophilous plants,
were observed in areas with nutrient-poor, acid sandy soils and high nitrogen deposition rates. Hence, shifts in species composition
were modulated by geographic variation in soil type and levels of nitrogen deposition. As the levels of atmospheric nitrogen
deposition are still very high in Flanders, it is likely that species from nutrient-poor habitats such as heathlands, will
further decline in the near future.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Nomenclature—Lambinon et al. (2004) for vascular plants. 相似文献
952.
Males of gregarious pinnipeds are often aggressive to conspecifics and sexual coercion of females is commonplace. Males of
some pinniped species have been known to attempt interspecific copulation, occasionally being successful in producing hybrid
offspring. The most extreme case of interspecific sexual coercion reported concerned species from different families. We report
a case of interspecific sexual harassment bridging the rank of vertebrate class. 相似文献
953.
Campion SN Johnson R Aleksunes LM Goedken MJ van Rooijen N Scheffer GL Cherrington NJ Manautou JE 《American journal of physiology. Gastrointestinal and liver physiology》2008,295(2):G294-G304
During acetaminophen (APAP) hepatotoxicity, increased expression of multidrug resistance-associated proteins 2, 3, and 4 (Mrp2-4) occurs. Mrp4 is the most significantly upregulated transporter in mouse liver following APAP treatment. Although the expression profiles of liver transporters following APAP hepatotoxicity are well characterized, the regulatory mechanisms contributing to these changes remain unknown. We hypothesized that Kupffer cell-derived mediators participate in the regulation of hepatic transporters during APAP toxicity. To investigate this, C57BL/6J mice were pretreated with clodronate liposomes (0.1 ml iv) to deplete Kupffer cells and then challenged with APAP (500 mg/kg ip). Liver injury was assessed by plasma alanine aminotransferase and hepatic transporter protein expression was determined by Western blot and immunohistochemistry. Depletion of Kupffer cells by liposomal clodronate increased susceptibility to APAP hepatotoxicity. Although increased expression of several efflux transporters was observed after APAP exposure, only Mrp4 was found to be differentially regulated following Kupffer cell depletion. At 48 and 72 h after APAP dosing, Mrp4 levels were increased by 10- and 33-fold, respectively, in mice receiving empty liposomes. Immunohistochemistry revealed Mrp4 staining confined to centrilobular hepatocytes. Remarkably, Kupffer cell depletion completely prevented Mrp4 induction by APAP. Elevated plasma levels of TNF-alpha and IL-1beta were also prevented by Kupffer cell depletion. These findings show that Kupffer cells protect the liver from APAP toxicity and that Kupffer cell mediators released in response to APAP are likely responsible for the induction of Mrp4. 相似文献
954.
Advances and limitations of individual-based models to analyze and predict dynamics of mangrove forests: A review 总被引:12,自引:8,他引:4
955.
Alveolar macrophages are indispensable for controlling influenza viruses in lungs of pigs 总被引:1,自引:0,他引:1
Kim HM Lee YW Lee KJ Kim HS Cho SW van Rooijen N Guan Y Seo SH 《Journal of virology》2008,82(9):4265-4274
Alveolar macrophages constitutively reside in the respiratory tracts of pigs and humans. An in vivo role of alveolar macrophages in defending against influenza viruses in mice infected with a reassorted influenza virus, 1918 HA/NA:Tx/91, was reported, but there has been no report on an in vivo role of alveolar macrophages in a natural host such as a pig using currently circulating human influenza virus. Here we show that in vivo depletion of alveolar macrophages in pigs by dichloromethylene diphosphonate (MDPCL2) treatment results in 40% mortality when pigs are infected with currently circulating human H1N1 influenza viruses, while none of the infected control pigs died. All infected pigs depleted of alveolar macrophages suffered from more severe respiratory signs than infected control pigs. Induction of tumor necrosis factor alpha in the infected pigs depleted of alveolar macrophages was significantly lower than that in the lungs of infected control pigs, and the induction of interleukin-10, an immunosuppressive cytokine, significantly increased in the lungs of infected pigs depleted of alveolar macrophages compared to infected control pigs. When we measured antibody titers and CD8(+) T lymphocytes expressing gamma interferon (IFN-gamma), lower antibody titers and a lower percentage of CD8(+) T lymphocytes expressing IFN-gamma were detectable in MDPCL2-treated infected pigs than in phosphate-buffered saline- and liposome-treated and infected pigs. Taken together, our findings suggest that alveolar macrophages are essential for controlling H1N1 influenza viruses in pigs. 相似文献
956.
957.
958.
Winnie Dejonghe Nico Boon Dave Seghers Eva M. Top Willy Verstraete 《Environmental microbiology》2001,3(10):649-657
It is generally assumed that increased microbial diversity corresponds to increased catabolic potential and, hence, to better removal of metabolites and pollutants. Yet, microbial diversity, more specifically richness of species in environmental samples and sites, is difficult to assess. It is proposed to interpret this diversity more in the framework of Pareto's law, i.e. 20% of the species govern 80% of the energy flux of the ecosystem. Ecological studies should attempt to delineate the main energy fluxes and that group of species playing quantitative key roles in the system. Consequently, bioaugmentation should aim at the rearrangement of the group of organisms dominantly involved in the overall energy flux, so that specific catabolic traits necessary for the clean up of pollutants are part of that active group. For soil ecosystems, the capacity of plant roots as creators of physical and chemical discontinuity should be used more strategically to bring about such rearrangements. Overall, this paper identifies a number of ecological concepts, such as the Pareto law, the Gompertz model and plant community-induced microbial competence, which may, given careful underpinning, open new perspectives for microbial ecology and biodegradation. 相似文献
959.
Reconstitution of Sec-dependent membrane protein insertion: nascent FtsQ interacts with YidC in a SecYEG-dependent manner 总被引:3,自引:0,他引:3
Martin van der Laan Edith N.G. Houben Nico Nouwen Joen Luirink Arnold J.M. Driessen 《EMBO reports》2001,2(6):519-523
The inner membrane protein YidC is associated with the preprotein translocase of Escherichia coli and contacts transmembrane segments of nascent inner membrane proteins during membrane insertion. YidC was purified to homogeneity and co-reconstituted with the SecYEG complex. YidC had no effect on the SecA/SecYEG-mediated translocation of the secretory protein proOmpA; however, using a crosslinking approach, the transmembrane segment of nascent FtsQ was found to gain access to YidC via SecY. These data indicate the functional reconstitution of the initial stages of YidC-dependent membrane protein insertion via the SecYEG complex. 相似文献
960.
Quantification of the leukocyte common antigen (CD45) in mature B-cell malignancies. 总被引:2,自引:0,他引:2
CD45 is a glycoprotein expressed on all lymphohematopoietic cells. Its expression increases during normal B-cell differentiation and remains stable on mature cells. Although it is widely known that CD45 antigen expression is decreased in B-acute lymphocytic leukemia (ALL), only scarce and contradictory information is available on CD45 expression on mature B-cell malignancies. In healthy adults (n = 15), CD45 expression on B lymphocytes was lower than that on T cells. In patients with chronic lymphocytic leukemia (CLL; n = 22), CD45 expression on malignant cells was lower than that on the whole lymphocyte population of healthy adults (n = 28) and on normal B lymphocytes (n = 15). In 6 of the 22 CLL patients, the malignant cell population could be separated from the normal lymphocyte population on the CD45-side scatter (SSC) plot. In 16 CLL patients, there was some degree of overlap between the malignant and normal cells with respect to CD45 expression. For these patients, there was an inverse correlation between CD45 expression on the whole lymphocyte population and the percentage of malignant cells in this population. In two patients with mantle cell lymphoma (MCL), CD45 expression on the malignant cells appeared lower than that on normal B cells and on the whole lymphocyte population. In six patients with hairy cell leukemia (HCL), CD45 expression on hairy cells was comparable to that on the whole lymphocyte population of healthy adults, but slightly higher than that of normal B cells. Evaluation of CD45 expression may help to characterize mature B-cell malignancies. 相似文献