全文获取类型
收费全文 | 6559篇 |
免费 | 381篇 |
国内免费 | 3篇 |
专业分类
6943篇 |
出版年
2021年 | 51篇 |
2020年 | 24篇 |
2019年 | 36篇 |
2018年 | 73篇 |
2017年 | 60篇 |
2016年 | 94篇 |
2015年 | 149篇 |
2014年 | 181篇 |
2013年 | 433篇 |
2012年 | 285篇 |
2011年 | 332篇 |
2010年 | 192篇 |
2009年 | 188篇 |
2008年 | 333篇 |
2007年 | 338篇 |
2006年 | 341篇 |
2005年 | 363篇 |
2004年 | 349篇 |
2003年 | 351篇 |
2002年 | 342篇 |
2001年 | 170篇 |
2000年 | 154篇 |
1999年 | 156篇 |
1998年 | 86篇 |
1997年 | 86篇 |
1996年 | 83篇 |
1995年 | 105篇 |
1994年 | 68篇 |
1993年 | 81篇 |
1992年 | 136篇 |
1991年 | 92篇 |
1990年 | 99篇 |
1989年 | 85篇 |
1988年 | 92篇 |
1987年 | 88篇 |
1986年 | 64篇 |
1985年 | 75篇 |
1984年 | 58篇 |
1983年 | 68篇 |
1982年 | 64篇 |
1981年 | 56篇 |
1980年 | 44篇 |
1979年 | 37篇 |
1978年 | 51篇 |
1977年 | 38篇 |
1976年 | 34篇 |
1975年 | 38篇 |
1974年 | 27篇 |
1973年 | 31篇 |
1970年 | 24篇 |
排序方式: 共有6943条查询结果,搜索用时 0 毫秒
971.
Kinoshita M Mizui K Ishiguro T Ohtsuki M Kansaku N Ogawa H Tsukada A Sato T Sasanami T 《The FEBS journal》2008,275(14):3580-3589
In birds, the egg envelope surrounding the oocyte prior to ovulation is called the perivitelline membrane and it plays important roles in fertilization. In a previous study we demonstrated that one of the components of the perivitelline membrane, ZP3, which is secreted from the ovarian granulosa cells, specifically interacts with ZP1, another constituent that is synthesized in the liver of Japanese quail. In the present study, we investigated whether ZP1 injected exogenously into the blood possesses the ability to reconstruct the perivitelline membrane of Japanese quail. When ZP1 purified from the serum of laying quail was injected into other female birds, the signal of this exogenous ZP1 was detected in the perivitelline membrane. In addition, we revealed, by means of ligand blot analysis, that serum ZP1 interacts with both ZP1 and ZP3 of the perivitelline membrane. By contrast, when ZP1 derived from the perivitelline membrane was administered, it failed to become incorporated into the perivitelline membrane. Interestingly, serum ZP1 recovered from other Galliformes, including chicken and guinea fowl, could be incorporated into the quail perivitelline membrane, but the degree of interaction between quail ZP3 and ZP1 of the vitelline membrane of laid eggs from chicken and guinea fowl appeared to be weak. These results demonstrate that exogenous ZP1 purified from the serum, but not ZP1 from the perivitelline membrane, can become incorporated into the perivitelline membrane upon injection into other types of female birds. To our knowledge, this is the first demonstration that the egg envelope component, when exogenously administered to animals, can reconstruct the egg envelope in vivo. 相似文献
972.
Kishiko Ogawa Katsuhiko Suzuki Mitsuharu Okutsu Kyoko Yamazaki Shoji Shinkai 《Immunity & ageing : I & A》2008,5(1):13
Background
Reactive oxygen species (ROS), including free radicals, oxygen ions, and peroxides, are implicated in cell damage. The objective of this study was to investigate whether the spontaneous production of ROS from neutrophils changes with age and is associated with the conventional inflammatory markers. 相似文献973.
974.
Andoh T Matsubara T Harumi T Yanagimachi R 《The International journal of developmental biology》2008,52(5-6):753-757
The fish egg is surrounded by a thick envelope called the chorion. The fertilizing spermatozoon enters the egg through a canal-like structure in the chorion, the micropyle. Examination of micropyle at fertilization is difficult if eggs are large and have no distinct landmarks surrounding the micropyle, or if they are positively buoyant in water. Eggs of many commercially important fishes (e.g., flounder, sea bream and eel) are buoyant in water or only slightly adhere to solid objects (e.g., sands, rock and water plants), which makes observation of spermatozoa at fertilization difficult. Here, we report that such eggs can be firmly attached to plastic and glass dishes that have been previously coated with poly-L-lysine. These adhering eggs can be fertilized and develop normally on the dishes. Observations of micropyles of three fish species, before and after sperm entry are presented. 相似文献
975.
Ohashi S Miyashita H Okada N Iemura T Watanabe T Kobayashi M 《Photosynthesis research》2008,98(1-3):141-149
A short overview is given on the discovery of the chlorophyll d-dominated cyanobacterium Acaryochloris marina and the minor pigments that function as key components therein. In photosystem I, chlorophyll d', chlorophyll a, and phylloquinone function as the primary electron donor, the primary electron acceptor and the secondary electron acceptor, respectively. In photosystem II, pheophytin a serves as the primary electron acceptor. The oxidation potential of chlorophyll d was higher than that of chlorophyll a in vitro, while the oxidation potential of P740 was almost the same as that of P700. These results help us to broaden our view on the questions about the unique photosystems in Acaryochloris marina. 相似文献
976.
Mouse genetic manipulations, such as the production of gene knock-out, knock-in, and transgenic mice, have provided excellent systems for analysis of numerous genes functioning during development. Nevertheless, the lack of specific promoters and enhancers that control gene expression in specific regions and at specific times, limits usage of these techniques. However, progress in in utero systems of electroporation into mouse embryos has opened a new window, permitting new approaches to answering important questions. Simple injection of plasmid DNA solution and application of electrical current to mouse embryos results in transient area- and time-dependent transfection. Further modification of the technique, arising from variations in types of electrodes used, has made it possible to control the relative size of the region of transfection, which can vary from a few cells to entire tissues. Thus, this technique is a powerful means not only of characterizing gene function in various settings, but also of tracing the migratory routes of cells, due to its high efficiency and the localization of gene expression it yields. We summarize here some of the potential uses and advantages of this technique for developmental neuroscience research. 相似文献
977.
Actin-related proteins (Arps) have been reported to be localized in the cell nucleus, and implicated in the regulation of chromatin and nuclear structure, as well as being involved in cytoplasmic functions. We demonstrate here that mouse ArpM1, which closely resembles the conventional actin, is expressed exclusively in the testis, particularly in haploid germ cells. ArpM1 protein first appears in the round spermatid and changes its localization dynamically in the nucleus during spermiogenesis. By co-immunoprecipitation analysis, profilin III was identified as ArpM1-interacting protein. Our findings suggest that the testis-specific profilin III-ArpM1 complex may be involved in conformational changes in the organization of the sperm-specific nucleus. STRUCTURED SUMMARY: 相似文献
978.
Pyruvate dehydrogenase (PDH), branched-chain 2-oxo acid dehydrogenase (BCDH) and 2-oxoglutarate dehydrogenase (OGDH) are multienzyme complexes that play crucial roles in several common metabolic pathways. These enzymes belong to a family of 2-oxo acid dehydrogenase complexes that contain multiple copies of three different components (E1, E2 and E3). For the Thermus thermophilus enzymes, depending on its substrate specificity (pyruvate, branched-chain 2-oxo acid or 2-oxoglutarate), each complex has distinctive E1 (E1p, E1b or E1o) and E2 (E2p, E2b or E2o) components and one of the two possible E3 components (E3b and E3o). (The suffixes, p, b and o identify their respective enzymes, PDH, BCDH and OGDH.) Our biochemical characterization demonstrates that only three specific E3*E2 complexes can form (E3b*E2p, E3b*E2b and E3o*E2o). X-ray analyses of complexes formed between the E3 components and the peripheral subunit-binding domains (PSBDs), derived from the corresponding E2-binding partners, reveal that E3b interacts with E2p and E2b in essentially the same manner as observed for Geobacillus stearothermophilus E3*E2p, whereas E3o interacts with E2o in a novel fashion. The buried intermolecular surfaces of the E3b*PSBDp/b and E3o*PSBDo complexes differ in size, shape and charge distribution and thus, these differences presumably confer the binding specificities for the complexes. 相似文献
979.
Naknukool S Hayakawa S Sun Y Ogawa M 《Bioscience, biotechnology, and biochemistry》2008,72(8):2082-2091
Novel basic proteins, duck basic protein small 1 (dBPS(1)) and 2 (dBPS(2)), were isolated from duck egg white by cation-exchange and gel filtration chromatography. Protein sequence analyses indicated that they possessed 39 amino acid residues with three disulfide bonds. The amino acid sequence of dBPS(1) showed 45% identity with dBPS(2). The amino acid sequence of dBPS(2) was the same as cygnin, a small protein from black swan, and strongly homologous with meleagrin from turkey and chicken. Phylogenic relationships implied that dBPS(1) and dBPS(2) share a common ancestry with cygnin and meleagrin. Based on MALDI-TOF mass spectra, the molecular masses of dBPS(1) and dBPS(2) were 4,373, and the 4,486 Da. pI of dBPS(1) and dBPS(2) elucidated by isoelectric focusing were 9.35 and 9.44. FT-IR spectra classified these proteins as (beta) proteins. Both dBPS(1) and dBPS(2), possessed high heat stability, Td 101.2 and 98.3 degrees C. Indirect ELISA results showed that the dBPS(1)/dBPS(2)-related proteins were distributed in the oviduct and gallbladder. 相似文献
980.