全文获取类型
收费全文 | 1159篇 |
免费 | 125篇 |
国内免费 | 1篇 |
专业分类
1285篇 |
出版年
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 27篇 |
2015年 | 44篇 |
2014年 | 47篇 |
2013年 | 41篇 |
2012年 | 62篇 |
2011年 | 49篇 |
2010年 | 48篇 |
2009年 | 37篇 |
2008年 | 45篇 |
2007年 | 60篇 |
2006年 | 51篇 |
2005年 | 45篇 |
2004年 | 50篇 |
2003年 | 42篇 |
2002年 | 37篇 |
2001年 | 45篇 |
2000年 | 52篇 |
1999年 | 26篇 |
1998年 | 16篇 |
1997年 | 17篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 27篇 |
1991年 | 27篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 12篇 |
1974年 | 9篇 |
1972年 | 6篇 |
1971年 | 8篇 |
1967年 | 6篇 |
1966年 | 8篇 |
排序方式: 共有1285条查询结果,搜索用时 15 毫秒
991.
A partially purified enzyme (120-fold) from Leuconostoc mesenteroides catalyzed the reversible N-acetylation of d-glucosamine-6-phosphate. Coenzyme A was not required and inhibited the reaction rate. Neither d-glucosamine nor N-acetyl-d-glucosamine served as a substrate for the reversible reaction. The enzyme preparation retained 50% of its original activity after 5 min at 100 C. The K(m) for acetate was 7.7 x 10(-2)m in the presence of 2 x 10(-2)md-glucosamine-6-phosphate. The K(m) for d-glucosamine-6-phosphate was 5.0 x 10(-3)m in the presence of 0.64 m acetate. The product of the reaction was characterized by comparison with N-acetyl-d-glucosamine-6-phosphate prepared by enzymatic phosphorylation of N-acetyl-d-glusamine. The characterization tests were: chromatographic migration, acid hydrolysis, enzymatic dephosphorylation, sodium borohydride reduction, and periodate oxidation. The equilibrium constant for the reaction was about 7.5 m for the expression K = (d-glucosamine-6-phosphate)(acetate)/N-acetyl-d-glucosamine-6-phosphate. The standard free energy of the reaction was approximately 1,200 cal per mole. 相似文献
992.
Markus Moser Umesh B. Mathur Franz T. Fürsich Dhirendra K. Pandey Neera Mathur 《Pal?ontologische Zeitschrift》2006,80(1):34-51
Fragmentary isolated remains of large (up to 20 m or more) sauropods from the Middle Jurassic (Bajocian) Khadir Formation
of Khadir Island (Kachchh, W India) are described and compared in detail. Three of the bone fragments (a metacarpal, a first
pedal claw and a fibula) can be assigned with confidence to the Camarasauromorpha and represent the oldest known record of
that derived dinosaur group. The new finds from western India further close a temporal and geographical gap in our knowledge
of sauropods and contribute to understanding their early phylogeny.
相似文献
993.
Robin K. Pettit George R. Pettit Ernest Hamel Fiona Hogan Bryan R. Moser Sonja Wolf Sandy Pon Jean-Charles Chapuis Jean M. Schmidt 《Bioorganic & medicinal chemistry》2009,17(18):6606-6612
As part of a broad-based SAR investigation of E-resveratrol (strong sirtuin activator and antineoplastic) and the anticancer vascular-targeting combretastatin-type stilbenes, a series of twenty-three β-E-nitrostyrenes was synthesized in order to evaluate potential antineoplastic, antitubulin, and antimicrobial activities. The β-E-nitrostyrenes evaluated ranged from monosubstituted phenols to trimethoxy and 3-methoxy-4,5-methylenedioxy derivatives. Two of the β-nitrostyrenes were synthesized as water-soluble sodium phosphate derivatives (4t, 4v). All except four (4r, 4s, 4t, 4u) of the series significantly inhibited a minipanel of human cancer cell lines. All but eight led to an IC50 of <10 μM for inhibition of tubulin polymerization, and all except three (4l, 4t, 4v) displayed antimicrobial activity. 相似文献
994.
G. A. Smith H. S. Moser 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,71(2):231-237
Summary In vitro selection procedures for herbicide tolerance were initially developed in the sporophytic generation of sugarbeet (Beta vulgaris L.), and then tested in the gametophytic generation. The primary objective of our study was to develop and evaluate in vitro techniques for identifying genotypes within heterogeneous seedling populations tolerant to specific herbicides, and to use meristematic cloning procedures to synthesize clones genetically tolerant to the herbicide. Seed from cloned selections tolerant to the herbicide ethofumesate were obtained and compared to plants from seed of the original population (using germination, central bud development, and root dry weight). Verification for in vitro selection accuracy was accomplished by pollen germination studies in the gametophyte. The results indicate that in vitro selection of germinated seedlings in the presence of the proper concentration of challenging agent can be effective in identifying genotypes tolerant to ethofumesate. Such identification was accomplished in fully differentiated tissue, but without the necessity of mature plants. Gametophytic studies, via pollen germination, indicated an association between genes operating in the sprophyte and those in the gametophyte. Cloning the seedlings identified as tolerant genotypes, and subsequent intercrossing of these clones provided a convenient method of synthesizing populations with gene frequencies shifted in the direction desired.Joint contribution of the Agricultural Research Service, USDA, and the Colorado State University Experiment Station. Published with the approval of the Director of the Colorado State University Experiment Station as Scientific Series Paper No. 2952 相似文献
995.
Sudden blindness following belpharoplasty. Report of seven cases 总被引:1,自引:0,他引:1
996.
997.
998.
Suppression of antibody secretion by the 2,4,6-trinitrophenol (TNP)-binding BALB/c myeloma, MOPC 315, by idiotype- and hapten-reactive suppressor T cells is mediated by secreted factors (TsF) and requires the presence of accessory cells (AC). Idiotype-specific TsF functions only in the presence of Ia+ AC and is completely idiotype specific. Moreover, no suppression is observed when myeloma targets and AC are separated by cell-impermeable membranes, indicating that the role of AC may be to bind, focus, and/or present TsF to the myeloma cells. In contrast, TNP-specific TsF inhibits myeloma function in the presence of TNP-protein and activated macrophages that are not Ia+. This form of suppression is nonspecific at the effector stage; i.e., anti-TNP TsF inhibits a non-TNP binding cell line, TEPC 15, as long as TNP-protein and activated macrophages are present. Moreover, suppression occurs even when myeloma targets and AC are separated by cell-impermeable membranes. These results are consistent with the view that hapten-reactive TsF binds to antigen on the surface of macrophages and induces these cells to secrete nonspecific immunosuppressive molecules. Thus, different types of AC may play fundamentally different roles in TsF-mediated suppression; they may either bind and present TsF to targets (as in the case of idiotype-specific TsF) or secrete nonspecific immunosuppressants as a consequence of a TsF-antigen interaction (hapten-specific TsF). Autonomous, suppressible targets provide valuable experimental systems for analyzing the cellular interactions in T cell-mediated suppression. 相似文献
999.
The relationship between abnormal color vision and adrenomyeloneuropathy (AMN) was investigated in 27 AMN patients and 31 age-matched controls by using the Farnsworth-Munsell 100 Hue test. Twelve (44%) of 27 patients showed test scores significantly above normal. The axes of bipolarity determined by the testing differed widely between the patients with abnormal scores, compatible with the notion that different alterations in visual pigment genes occur in different AMN kindreds. These observations confirm our earlier impression that the frequency of abnormal color vision is increased in these kindreds, and it supports our contentions that (1) AMN (and its companion, adrenoleukodystrophy) are very closely linked to the visual pigment loci at Xq28 and (2) this proximity might provide the opportunity to observe contiguous gene defects. 相似文献
1000.
Plant Functional Types Differ in Their Long-term Nutrient Response to eCO2 in an Extensive Grassland
Seibert Ruben Andresen Louise C. Jarosch Klaus A. Moser Gerald Kammann Claudia I. Yuan Naiming Luterbacher Jrg Laughlin Ronnie J. Watson Catherine J. Erbs Martin Mller Christoph 《Ecosystems》2022,25(5):1084-1095
Ecosystems - Increasing atmospheric CO2 enhances plant biomass production and may thereby change nutrient concentrations in plant tissues. The objective of this study was to identify the effect of... 相似文献