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1.
以尖峰岭地区为研究区域,探讨了森林生态系统服务功能的内涵,并使用市场价值,影子工程、机会成本和替代花费等方法评价了海南岛尖峰岭地区热带森林生态系统服务功能的生态经济价值,结果表明,在尖峰岭地区,面积为44667.00hm^2的热带森林生态系统服务功能价平均每年6638.49万元,其中林产品价值为7164.11万元,涵养水源价值为39429.21万元,保持土壤减少侵蚀价值为247.26万元,固定CO  相似文献
2.
This paper reviews the recent advances in understanding of metal removal from contaminated soils, using either hyperaccumulator plants, or high biomass crop species after soil treatment with chelating compounds. Progress has been made at the physiology and molecular level regarding Zn and Ni uptake and translocation in some hyperaccumulators. It is also known that natural hyperaccumulators do not use rhizosphere acidification to enhance their metal uptake. Recently, it has been found that some natural hyperaccumulators proliferate their roots positively in patches of high metal availability. In contrast, non-accumulators actively avoid these areas, and this is one of the mechanisms by which hyperaccumulators absorb more metals when grown in the same soil. However, there are few studies on the exudation and persistence of natural chelating compounds by these plants. It is thought that rhizosphere microorganisms are not important for the hyperaccumulation of metals from soil. Applications of chelates have been shown to induce large accumulations of metals like Pb, U and Au in the shoots of non-hyperaccumulators, by increasing metal solubility and root to shoot translocation. The efficiency of metal uptake does vary with soil properties, and a full understanding of the relative importance of mass flow and diffusion in the presence and absence of artificial chelates is not available. To successfully manipulate and optimise future phytoextraction technologies, it is argued that a fully combined understanding of soil supply and plant uptake is needed.  相似文献
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4.
Arsenic hyperaccumulation by different fern species   总被引:26,自引:3,他引:23  
5.
The capacity of the human complement regulatory protein CD59 to interact with terminal complement proteins in a species-selective manner was examined. When incorporated into chicken E, CD59 (purified from human E membranes) inhibited the cytolytic activity of the C5b-9 complex in a manner dependent on the species of origin of C8 and C9. Inhibition of C5b-9-mediated hemolysis was maximal when C8 and C9 were derived from human (hu) or baboon serum. By contrast, CD59 showed reduced activity when C8 and C9 were derived from dog or sheep serum, and no activity when C8 and C9 were derived from either rabbit or guinea pig (gp) serum. Similar specificity on the basis of the species of origin of C8 and C9 was also observed for CD59 endogenous to the human E membrane, using functionally blocking antibody against this cell surface protein to selectively abrogate its C5b-9-inhibitory activity. When E bearing human CD59 were exposed to C5b-8hu, CD59 was found to inhibit C5b-9-mediated lysis, regardless of the species of origin of C9, suggesting that the inhibitory function of CD59 can be mediated through recognition of species-specific domains expressed by human C8. Consistent with this interpretation, CD59 was found to bind to C5b-8hu but not to C5b67hu or C5b67huC8gp. Although CD59 failed to inhibit hemolysis mediated by C5b67huC8gpC9gp, its inhibitory function was observed for C5b67huC8gpC9hu, suggesting that, in addition to its interaction with C5b-8hu, CD59 also interacts in a species-selective manner with C9hu incorporated into C5b-9. Consistent with this interpretation, CD59 was found to bind both C5b67huC8gpC9hu and C5b-8huC9gp, but not C5b67huC8gpC9gp. Taken together, these data suggest that the capacity of CD59 to restrict the hemolytic activity of human serum complement involves a species-selective interaction of CD59, which involves binding to both the C8 and C9 components of the membrane attack complex. Although CD59 expresses selectivity for C8 and C9 of human origin, this "homologous restriction" is not absolute, and this human complement regulatory protein retains functional activity toward C8 and C9 of some nonprimate species.  相似文献
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7.
Thlaspi caerulescens (J. and C. Presl) and Thlaspi ochroleucum (Boiss. ex Heldr) were grown in three different soils containing moderate to high amounts of heavy metals in a pot experiment, using a rhizobag technique. T. caerulescens accumulated significantly more Zn in the shoots than T. ochroleucum. The concentrations of Zn in the shoots of T. caerulescens ranged from 3100 to 8100 mg kg-1 dry matter (DM), but only from 800 to 1600 mg kg-1 DM in T. ochroleucum. Total uptake of Zn in the shoots of T. caerulescens was about 5 times that of T. ochroleucum. In contrast, the differences between the two species in the uptake of Cd, Cr, Cu, Ni and Pb were generally small. Concentrations of mobile Zn (extractable with 1M NH4NO3) in the rhizosphere and non-rhizosphere soils decreased considerably after growth of both plants, but the decreases were greater with T. caerulescens than with T. ochroleucum. The decreases in the mobile fraction accounted for less than 10% of the total Zn uptake by T. caerulescens indicating that this species was effective in mobilising Zn from less soluble fractions in the soils. The rhizosphere soils tended to have higher concentrations of mobile Zn than the non-rhizosphere soils, probably because of the lower pH in the rhizosphere. The pH in the rhizosphere soils was 0.2-0.4 units lower than that in the non-rhizosphere soils at the end of the experiment. However, there were no significant differences between the two species in the degree of rhizosphere acidification. The results suggest that T. caerulescens has potential for removing Zn from moderately to highly contaminated soils, but that this ability was not related to the pH changes in the rhizosphere.  相似文献
8.
Identical G+1 mutations in three different introns of the gene for type III procollagen (COL3A1) that cause aberrant splicing of RNA were found in three probands with life-threatening variants of Ehlers-Danlos syndrome. Because the three mutations were in a gene with multiple and homologous exons, they provided an interesting test for factors that influence aberrant splicing. The G+1 to A mutation in intron 16 caused extensive exon skipping, the G+1 to A mutation in intron 20 caused both use of a cryptic splice site and retention of all the intron sequences, and the G+1 to A mutation in intron 42 caused efficient use of a single cryptic splice site. The different patterns of RNA splicing were not explained by evaluation of potential cryptic splice sites in the introns by either their homology with 5'-splice sites from other genes or by their delta G(0)37 values for binding to U1 RNA. Instead, the results suggested that the patterns of aberrant RNA splicing were primarily determined by the relative rates at which adjacent introns were normally spliced.  相似文献
9.
Searching for a function for nuclear actin   总被引:18,自引:0,他引:18  
The abundant cytoskeletal protein actin has numerous cytoplasmic roles. Although there are many reports of the presence of actin in the nucleus, in general they have been discounted as artifactual. However, recent work has begun to provide evidence for important roles for actin in nuclear processes ranging from chromatin remodelling to splicing. In addition, several regulators of actin polymerization are localized to the nucleus or translocate to the nucleus in a regulated manner, suggesting that there is some function of actin in the nucleus that is subject to regulation. This review discusses the evidence for actin in the nucleus and summarizes recent work suggesting that actin or actin-related proteins are involved in the regulation of nuclear processes such as chromatin remodelling.  相似文献
10.
The hyperaccumulator Thlaspi caerulescens J & C Presl. was grown in seven different soils collected from around Europe that had been contaminated with heavy metals by industrial activity or the disposal of sewage sludge to land. Zinc accumulation factors (shoot concentration/initial soil solution concentration) ranged from 3500–85 000 with a mean value of around 36 000. This compares with mean accumulation factors of 636, 66 and 122 for Cd, Ca and Mg, respectively. The concentration of Zn in the shoots was much greater than in the roots. The total removal of Zn and Cd ranged from 8 to 30 and from 0.02 to 0.5 mg kg-1 soil, respectively. The Zn concentration in shoots of T. caerulescens correlated, using a curvilinear relationship, with the initial Zn concentration in soil solution (R2 = total Zn 0.78; Zn2+ 0.80). There was no relationship between the uptake of Zn and the total Zn concentration in the soil. In most soils, solution pH increased only slightly after growth of T. caerulescens, indicating that acidification was not the mechanism used to mobilise Zn in the soil. Dissolved organic carbon concentrations generally increased but characterisation of the component organic compounds was not attempted. The concentrations of Zn and Cd in soil solution decreased considerably after growth of T. caerulescens. The percentages of Zn and Cd in soil solution present as free ions also decreased. However, the decrease of Zn in soil solution after growth accounted for only about 1% of the total Zn uptake by T. caerulescens. This was much lower than for Cd, Ca and Mg. The results suggest that either T. caerulescens was highly efficient at mobilising Zn which was not soluble initially, or the soils used had large buffering capacities to replenish soil solution Zn within a short time. This work highlights the need to investigate the role of root exudates on the mobilisation of Zn and Cd in soils by the hyperaccumulator T. caerulescens.  相似文献
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