全文获取类型
收费全文 | 408篇 |
免费 | 38篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 22篇 |
2012年 | 27篇 |
2011年 | 25篇 |
2010年 | 9篇 |
2009年 | 15篇 |
2008年 | 16篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1995年 | 11篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 11篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有446条查询结果,搜索用时 15 毫秒
411.
Grazing by large mammalian herbivores impacts climate as it can favor the size and stability of a large carbon (C) pool in the soils of grazing ecosystems. As native herbivores in the world's grasslands, steppes, and savannas are progressively being displaced by livestock, it is important to ask whether livestock can emulate the functional roles of their native counterparts. While livestock and native herbivores can have remarkable similarity in their traits, they can differ greatly in their impacts on vegetation composition which can affect soil-C. It is uncertain how these similarities and differences impact soil-C via their influence on microbial decomposers. We test competing alternative hypotheses with a replicated, long-term, landscape-level, grazing-exclusion experiment to ask whether livestock in the Trans-Himalayan ecosystem of northern India can match decadal-scale (2005–2016) soil-C stocks under native herbivores. We evaluate multiple lines of evidence from 17 variables that influence soil-C (quantity and quality of C-input from plants, microbial biomass and metabolism, microbial community composition, eDNA, veterinary antibiotics in soil), and assess their inter-relationships. Livestock and native herbivores differed in their effects on several soil microbial processes. Microbial carbon use efficiency (CUE) was 19% lower in soils under livestock. Compared to native herbivores, areas used by livestock contained 1.5 kg C m−2 less soil-C. Structural equation models showed that alongside the effects arising from plants, livestock alter soil microbial communities which is detrimental for CUE, and ultimately also for soil-C. Supporting evidence pointed toward a link between veterinary antibiotics used on livestock, microbial communities, and soil-C. Overcoming the challenges of sequestering antibiotics to minimize their potential impacts on climate, alongside microbial rewilding under livestock, may reconcile the conflicting demands from food-security and ecosystem services. Conservation of native herbivores and alternative management of livestock is crucial for soil-C stewardship to envision and achieve natural climate solutions. 相似文献
412.
413.
C S Rao N Muralidhar M U Naidu A Y Junnarkar P P Singh 《Indian journal of experimental biology》1991,29(2):120-122
Carrageenin (2%) was used to produce edema and hyperalgesia; indomethacin, phenylbutazone, aspirin, ibuprofen, analgin, paracetamol and phenacetin were tested at different doses for anti-inflammatory and analgesic activity in the same rats as the peak for the edema reached at the end of 3rd hr and for the hyperalgesia at the end of 4th hr. Indomethacin, phenylbutazone and ibuprofen reduced edema and increased the pain threshold. Analgin and aspirin increased the pain threshold relatively at a low dose. Paracetamol and phenacetin were inactive in the doses tested. Carrageenin (2%) was observed to possess both phlogistic and allogenic properties. 相似文献
414.
415.
416.
The effects of lime and P on the chemical composition of the tropical legume Leucaena leucocephala were studied in a controlled climate laboratory experiment using 4 (Koronivia, Nadroloulou, Batiri, and Seqaqa) highly-weathered, acid soils from Fiji. For all soils, changes in the concentration of P in the Leucaena tops followed trends similar to the yield response curve, i.e., the concentration of P was highest at the soil pH at which maximum growth occurred. The concentration of Al in plant tops increased on either side of the pH of maximum growth, but Al uptake by the whole plant (tops plus roots) declined steadily with increasing pH. Although complete major (except P) and minor nutrients were added regularly, there was variation in the uptake of nutrients with pH. Poor growth at low pH values was attributed to an Al-induced P deficiency within the plant and at high pH to a soil P deficiency and, to a smaller extent, to the increased concentration of Al in the plant tops. 相似文献
417.
The present study was conducted to determine the nitrogen transformation test of abamectin 3.6 g/L EC. This study was conducted as per OECD Guidelines for the Testing of Chemicals OECD 216. The test item abamectin 3.6 g/L emulsifiable concentrate (EC) was applied in a loamy sand soil and incubated over a period of 28 days for nitrogen transformation test at concentrations of 3.2 μL/kg soil dry weight and 16 μL/kg soil dry weight. The concentrations tested were based on one and five times the maximum recommended field application rates of 1200 mL/ha and 6000 mL/ha of abamectin 3.6 g/L EC, respectively. The deviation in soil nitrate content determined at 28 days after application of the test item to soil compared to the control was 0.14% and ? 9.25% for the single and five times test concentrations, respectively. There is no significant variation between the treatment groups and control sample. The rate of nitrate formation between 14 and 28 days after application of the test item to soil deviate from control by 10.41% and 13.74% for 3.2 and 16 μL/kg soil dry weight, respectively. Deviations in nitrate levels and nitrate formation rates in soil treated with up to and including 16 μL/kg of test item/kg soil dry weight were < 25%, compared to control indicating no significant effect occurred in nitrogen transformation. 相似文献
418.
Rationalization of the effects of compatible solutes on protein stability in terms of thermodynamic nonideality. 总被引:5,自引:0,他引:5
C L Winzor D J Winzor L G Paleg G P Jones B P Naidu 《Archives of biochemistry and biophysics》1992,296(1):102-107
Inhibition by compatible solutes such as proline and glycine betaine of the rate of coagulation, at 60 degrees C, of bovine serum albumin in 0.1 M acetate buffer, pH 5, is used as a model system to substantiate the concept that the production of high concentrations of osmolytes by plants and other organisms in response to stress (e.g., drought) results in stabilization of native enzyme structures via nonspecific excluded volume effects. The paradoxical situation whereby this effect of compatible solutes counters to some extent the protein-precipitating effect of poly(ethylene glycol) is also seemingly resolved. 相似文献
419.
Toxic shock syndrome toxin-1 (TSST-1) producing strains of Staphylococcus aureus isolated from 18 patients with toxic shock syndrome (TSS) and from 56 patients with other diagnoses were compared for capacity to interact with various serum and connective tissue proteins. TSS associated isolates showed significantly stronger binding of Type-I collagen (Cn-I) and Cn-II than non-TSS strains, in a particle agglutination assay (PAA) as well as in 125I labelled Cn uptake experiments. 125I Cn-IV binding, was similar between the two groups, whereas in PAA, a stronger interaction was observed for non-TSS than TSS associated strains. The median binding of 125I Cn to TSS-associated strains were 52.2 (Cn-I), 30.6 (Cn-II) and 20.0 (Cn-IV) compared to 20.0 (Cn-I), 14.4 (Cn-II) and 24.4 (Cn-IV) values of non-TSS strains. A saturation with 125I Cn-I and Cn-II binding was established for TSS (30 min) and non-TSS (15 min) strains. 125I Cn-IV binding reached a saturation in 10 min and 90 min with TSS and non-TSS strains respectively. Finally, the binding profiles of TSS associated and non-TSS strains to fibronectin, fibrinogen, laminin and IgG did not differ in both PAA and radioisotope assays. In scanning electron microscopy, cells of TSS associated strains bound to the reprecipitated native Cn-I fibrils. In contrast, most cells of non-TSS strains were localized to the distal end or were trapped between the Cn fibrils.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
420.
Characterization of a new lignin peroxidase gene (GLG6) from Phanerochaete chrysosporium 总被引:7,自引:0,他引:7
P S Naidu Y Z Zhang C A Reddy 《Biochemical and biophysical research communications》1990,173(3):994-1000
Sequence analysis of a new lignin peroxidase (LIP) gene, GLG6, from P. chrysosporium showed that it encodes a mature LIP protein with a predicted Mr of 36,454. A 28 aa signal peptide precedes the mature protein. The coding region of GLG6 is interrupted by nine introns ranging in size from 50-57 bp. GLG6 encoded-LIP has 72%, 88% and 82% homology, respectively, to the LIP isozymes H2, H3, and H10. Comparison of the N-terminal sequence of GLG6-encoded LIP to that of the LIP proteins H2, H8, H10 also showed that the former is relatively less related to the H2 protein than it is to the H8 and H10 proteins. Expression of GLG6, similar to the other LIP genes, occurs only during secondary metabolism. 相似文献