全文获取类型
收费全文 | 373661篇 |
免费 | 37774篇 |
国内免费 | 242篇 |
出版年
2016年 | 5594篇 |
2015年 | 10098篇 |
2014年 | 10344篇 |
2013年 | 12223篇 |
2012年 | 12513篇 |
2011年 | 9810篇 |
2010年 | 7333篇 |
2009年 | 7010篇 |
2008年 | 7623篇 |
2007年 | 7811篇 |
2006年 | 7468篇 |
2005年 | 14465篇 |
2004年 | 13087篇 |
2003年 | 11083篇 |
2002年 | 7566篇 |
2001年 | 12009篇 |
2000年 | 11457篇 |
1999年 | 10467篇 |
1998年 | 3873篇 |
1997年 | 3898篇 |
1996年 | 3828篇 |
1995年 | 3601篇 |
1994年 | 3617篇 |
1993年 | 3561篇 |
1992年 | 9879篇 |
1991年 | 9757篇 |
1990年 | 9637篇 |
1989年 | 9486篇 |
1988年 | 8981篇 |
1987年 | 8843篇 |
1986年 | 8110篇 |
1985年 | 8310篇 |
1984年 | 6700篇 |
1983年 | 5879篇 |
1982年 | 4520篇 |
1981年 | 4318篇 |
1980年 | 3922篇 |
1979年 | 6885篇 |
1978年 | 5309篇 |
1977年 | 5005篇 |
1976年 | 4817篇 |
1975年 | 5386篇 |
1974年 | 5938篇 |
1973年 | 5865篇 |
1972年 | 5462篇 |
1971年 | 4993篇 |
1970年 | 4420篇 |
1969年 | 4442篇 |
1968年 | 3959篇 |
1967年 | 3529篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The complete primary structure of the functional site of erythrocyte protein 4.1 involved in spectrin-actin associations has been determined. The sequence of this domain, which contains 67 amino acids and has a molecular mass of 8045 daltons, has been obtained by NH2-terminal sequence analysis of an 8-kDa chymotryptic peptide, three endoproteinase lysine C-cleaved peptides and two peptides obtained by Staphylococcus aureus protease V8 cleavage. All peptides including the 8-kDa domain peptide were purified by reverse-phase high performance liquid chromatography. Antibodies against two different synthetic peptides of the 8-kDa domain are able to inhibit the association between protein 4.1, spectrin, and F-actin, corroborating that the 8-kDa domain is responsible for the formation of a ternary complex. A computer search of the 8-kDa sequence with the National Biomedical Research Foundation database did not detect any significant homologies to known sequences. Protein 4.1 is not related to any known proteins and may represent a new protein superfamily. 相似文献
52.
W.J. Malaisse F. Malaisse-Lagae A. Sener 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,797(2):194-202
1. Because L-asparagine augments insulin release evoked by L-leucine, the metabolism of these two amino acids was investigated in rat pancreatic islets. 2. L-Leucine inhibited the uptake and deamidation of L-asparagine, but failed to exert any obvious primary effect upon the further catabolism of aspartate derived from exogenous asparagine. 3. L-Asparagine augmented the oxidation of L-leucine, and effect possibly attributable to activaion of 2-ketoisocaproate dehydrogenase. 4. The association of L-asparagine and L-leucine exerted a sparing action on the utilization of endogenous amino acids, so that the integrated rate of nutrients oxidation was virtually identical in the sole presence of L-leucine and simultaneous presence of L-asparagine and L-leucine, respectively. 5. It is proposed that the enhancing action of L-asparagine upon insulin release evoked by L-leucine is attributable to an increased generation rate of cytosolic NADPH rather than any increase in nutrients oxidation. 相似文献
53.
54.
55.
Orotate prevents galactosamine hepatitis 总被引:1,自引:0,他引:1
56.
Synaptonemal complexes and meiosis in myxomycetes 总被引:4,自引:0,他引:4
Synaptonemal complexes (SC) have been observed in spores 18–24 hr past cleavage in natural fruitings of Physarum cinereum, P. bogoriense, Hemitrichia stipitata, Tubifera ferruginosa, and Arcyria incarnata. Laboratory fruitings of Arcyria cinerea, Stemonitis herbatica, and a homothallic isolate of Physarum pusillum also have SC's present in spores during the same postcleavage period. The presence of these paired chromosomes of meiotic prophase in spores of species collected in nature and in a diversity of taxa suggests that the usual position of meiosis in Myxomycetes is inside the postcleavage spore. Criteria are proposed for evaluating the validity of the SC as an indicator of meiosis. 相似文献
57.
As part of systematic studies of the genus Porphyrain New Zealand, constituent sugar analyses of cell wall polysaccharidesin situ in dry thalli were found to yield data that weretaxonomically informative. Variation in constituent sugar levels betweenspecieswas sufficient in some cases to be useful in species differentiation. Thereproductive state of thallus regions had a significant impact on the levels ofconstituent sugars, whereas storage of dried thalli for eight months had noeffect. Three epiphytic taxa currently classified as species ofPorphyra appear to be incorrectly placed within the genus,as their constituent sugars and the levels of these sugars differed markedlyfrom those of all other species examined. 相似文献
58.
Maria Rebelo Claudia Sousa Howard M. Shapiro Maria M. Mota Martin P. Grobusch Thomas H?nscheid 《PloS one》2013,8(4)
Resistance of Plasmodium falciparum to almost all antimalarial drugs, including the first-line treatment with artemisinins, has been described, representing an obvious threat to malaria control. In vitro antimalarial sensitivity testing is crucial to detect and monitor drug resistance. Current assays have been successfully used to detect drug effects on parasites. However, they have some limitations, such as the use of radioactive or expensive reagents or long incubation times. Here we describe a novel assay to detect antimalarial drug effects, based on flow cytometric detection of hemozoin (Hz), which is rapid and does not require any additional reagents. Hz is an optimal parasite maturation indicator since its amount increases as the parasite matures. Due to its physical property of birefringence, Hz depolarizes light, hence it can be detected using optical methods such as flow cytometry. A common flow cytometer was adapted to detect light depolarization caused by Hz. Synchronized in vitro cultures of P. falciparum were incubated for 48 hours with several antimalarial drugs. Analysis of depolarizing events, corresponding to parasitized red blood cells containing Hz, allowed the detection of parasite maturation. Moreover, chloroquine resistance and the inhibitory effect of all antimalarial drugs tested, except for pyrimethamine, could be determined as early as 18 to 24 hours of incubation. At 24 hours incubation, 50% inhibitory concentrations (IC50) were comparable to previously reported values. These results indicate that the reagent-free, real-time Hz detection assay could become a novel assay for the detection of drug effects on Plasmodium falciparum. 相似文献
59.
60.
The Biopolymer Markup Language. 总被引:6,自引:0,他引:6
D Feny? 《Bioinformatics (Oxford, England)》1999,15(4):339-340
SUMMARY: An XML derived from a data model designed to be a hierarchical representation of an organism has been specified and a browser to use this language has been developed. AVAILABILITY: The language definition is available in HTML form at http://www.proteometrics.com/BIOML/. The BioML browser is available on request from the author. 相似文献