全文获取类型
收费全文 | 1776篇 |
免费 | 88篇 |
国内免费 | 1篇 |
专业分类
1865篇 |
出版年
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 24篇 |
2016年 | 26篇 |
2015年 | 59篇 |
2014年 | 64篇 |
2013年 | 130篇 |
2012年 | 112篇 |
2011年 | 90篇 |
2010年 | 56篇 |
2009年 | 60篇 |
2008年 | 88篇 |
2007年 | 77篇 |
2006年 | 93篇 |
2005年 | 77篇 |
2004年 | 86篇 |
2003年 | 92篇 |
2002年 | 102篇 |
2001年 | 44篇 |
2000年 | 40篇 |
1999年 | 36篇 |
1998年 | 25篇 |
1997年 | 10篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 34篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1975年 | 10篇 |
1974年 | 16篇 |
1973年 | 14篇 |
1972年 | 22篇 |
1971年 | 12篇 |
1967年 | 7篇 |
排序方式: 共有1865条查询结果,搜索用时 0 毫秒
71.
Noriyasu Ota Satoko Soga Akira Shimotoyodome 《Bioscience, biotechnology, and biochemistry》2016,80(12):2412-2417
Our previous studies demonstrated that dietary supplementation with tea catechins combined with exercise improved endurance capacity in mice. This study aimed to demonstrate the effect of daily tea catechin consumption on aerobic capacity in humans. Sixteen Japanese non-athlete male subjects (aged 25–47 years) took 500 mL of a test beverage with or without tea catechins (570 mg) daily for 8 weeks and attended a training program twice a week. Aerobic capacity was evaluated by indirect calorimetry and near-infrared spectroscopy during graded cycle exercise. Catechin beverage consumption was associated with a significantly higher ventilation threshold during exercise and a higher recovery rate of oxygenated hemoglobin and myoglobin levels after graded cycle exercise when compared to subjects receiving the placebo beverage. These results indicate that daily consumption of tea catechins increases aerobic capacity when combined with semiweekly light exercise, which may be due to increased skeletal muscle aerobic capacity. 相似文献
72.
Jonathan P. Rast Michele K. Anderson Ronda T. Litman M. Margittai Gary W. Litman Tatsuya Ota Michael J. Shamblott 《Immunogenetics》1994,40(2):83-99
The prototypic chondrichthyan immunoglobulin (Ig) light chain type (type I) isolated from Heterodontus francisci (horned shark) has a clustered organization in which variable (V), joining (J), and constant (C) elements are in relatively close linkage (V-J-C). Using a polymerase chain reaction-based approach on a light chain peptide sequence from the holocephalan, Hydrolagus colliei (spotted ratfish), it was possible to isolate members of a second light chain gene family. A probe to this light chain (type II) detects homologs in two orders of elasmobranchs, Heterodontus, a galeomorph and Raja erinacea (little skate), a batoid, suggesting that this light chain type may be present throughout the cartilaginous fishes. In all cases, V, J, and C regions of the type II gene are arranged in closely linked clusters typical of all known Ig genes in cartilaginous fishes. All representatives of this type II gene family are joined in the germline. A third (kappa-like) light chain type from Heterodontus is described. These findings establish that a degree of light chain class complexity comparable to that of the mammals is present in the most phylogenetically distant extant jawed vertebrates and that the phenomenon of germline-joined (pre-rearranged) genes, described originally in the heavy chain genes of cartilaginous fishes, extends to light chain genes. 相似文献
73.
A culture of Thaumatomastix was isolated from a sediment sample collected in Oslofjorden and established as a monospecific strain (UIO286). Based on this culture, light and transmission electron microscopy and phylogenetic analyses were carried out. Thaumatomastix species are confined within the order Thaumatomonadida of the class Imbricatea and phylum Cercozoa. They are heterotrophic and their cell bodies are covered with silica scales. Observations of thin sections as well as whole mounts indicate that the morphology and ultrastructure of UIO286 is identical to T. salina, which was initially described from salt pools in Denmark. Detailed examination revealed some new features such as the presence of pseudopodia and silica deposition vesicles producing spine scales. The phylogeny presented here includes ribosomal DNA sequences from both imbricatean cultures and environmental samples. The 18S rDNA phylogenetic tree suggests that (i) Thaumatomastix is paraphyletic within the Thaumatomonadida clade, (ii) there is no close affinity between T. salina and other cultured and sequenced strains, but it is closely related to a sequence obtained from environmental DNA; we propose the present strain to serve as a reference culture of Thaumatomastix species and T. salina. Further, we discuss the distribution, habitats, and evolution of scale formation among euglyphids and thaumatomonads. 相似文献
74.
A number of social insect species have recently been shown to have genetically influenced caste determination (GCD), challenging the conventional view that caste determination should be strictly environmental. To date, GCD has been found in phylogenetically isolated species; examples of GCD being present in multiple species of a genus are lacking. Through crossing experiments of neotenic (juvenile) reproductives, we have recently provided the first evidence for a royal versus worker GCD in the termite Reticulitermes speratus. To elucidate whether this system is more widespread, we performed crossing experiments using three additional Reticulitermes species. Offspring caste and sex ratios were found to be highly similar to those found previously in R. speratus, raising the possibility that GCD was present in an ancestral lineage of Reticulitermes, and subsequently maintained throughout several episodes of speciation. 相似文献
75.
76.
Takeshi Kawarabata Masako Funakoshi Yoshinobu Aratake 《Journal of invertebrate pathology》1980,35(1):34-42
Occluded virions of the Bombyx mori nuclear polyhedrosis virus were efficiently liberated from polyhedra by dissolution with the silkworm gut juice. The liberated virions were purified by sucrose density gradient centrifugation and the bands of enveloped virions were observed in the gradients. There was no functional difference between the gut juice-liberated and the carbonate-liberated virions. Disruption of enveloped virions by the gut juice was observed, but the formation of nucleocapsids from the degradation of the occluded virions was not detected. High yields of the enveloped virions from the polyhedra dissolved by the gut juice was obtained by separating the virions through sucrose density gradient centrifugation immediately after the dissolution of the polyhedra. Many factors, e.g., rearing seasons, silkworm strains, and rearing conditions, affect the polyhedra-dissolving property of the larval gut juice. 相似文献
77.
Atsushi Suzuki Yoshinobu Nonami Darrel E. Goll 《Bioscience, biotechnology, and biochemistry》2013,77(7):1461-1467
The nature of the soluble proteins and peptides released from myofibrils by treatment with CASF (Ca2+-activated sarcoplasmic factor) was investigated by using Polyacrylamide gel electrophoresis in both a nondenaturing and a denaturing (sodium dodecyl sulfate=SDS) solvent and by using gel permeation chromatography on Sepharose 6B. Both CASF and trypsin treatment cause removal of Z-disks before causing other ultrastructurally detectable degradation of myofibrils. CASF treatment of myofibrils releases a protein that is identical to α-actinin, one of the known components of the Z-disk, on the basis of mobility in Polyacrylamide gel electrophoresis in a nondenaturing solvent and in SDS and on the basis of elution from gel permeation columns. Trypsin treatment of myofibrils releases a number of smaller molecular weight products that cannot be identified with any of the known myofibrillar proteins. Hence, CASF seems to remove Z-disks from myofibrils by means of a very specific proteolytic activity that releases α-actinin without extensively degrading it. Trypsin, on the other hand, probably seems to remove Z-disks by degrading α-actinin to peptides. 相似文献
78.
Development of a highly sensitive in vitro assay method for biological activity of endotoxin contamination in biological products. 总被引:2,自引:0,他引:2
Akihiko Yamamoto Masaki Ochiai Michiyo Kataoka Hiromi Toyoizumi Yoshinobu Horiuchi 《Biologicals》2002,30(2):85-92
The pyrogen test in rabbits has been replaced by the bacterial endotoxin test. The endotoxin test, however, showed a considerable discrepancy with pyrogenicity and was, therefore, assumed to have an efficacy limitation in directly predicting harmful biological effects of endotoxin. We developed a sensitive in vitro assay method by making use of tumour necrosis factor alpha (TNF-alpha) induction in RAW264.7 cells, which showed a fine correlation with pyrogenicity in rabbits. RAW264.7 cells maintained by serial subculture under an endotoxin-free condition have gained the similar level of sensitivity as the endotoxin test to allow extensive dilutions of a drug for eliminating adverse effects on the cells. The in vitro TNF-alpha induction assay was shown to be capable to detect quantitatively a synergistic effect of a drug and endotoxin. The synergy is assumed necessary to be taken into consideration to define the limit value for the endotoxin test for guaranteeing the similar level of safety as by the pyrogen test. 相似文献
79.
80.