全文获取类型
收费全文 | 348109篇 |
免费 | 40818篇 |
国内免费 | 165篇 |
专业分类
389092篇 |
出版年
2018年 | 2958篇 |
2016年 | 4039篇 |
2015年 | 5473篇 |
2014年 | 6520篇 |
2013年 | 9411篇 |
2012年 | 10443篇 |
2011年 | 10599篇 |
2010年 | 7191篇 |
2009年 | 6406篇 |
2008年 | 9260篇 |
2007年 | 9734篇 |
2006年 | 9066篇 |
2005年 | 8789篇 |
2004年 | 8884篇 |
2003年 | 8607篇 |
2002年 | 8514篇 |
2001年 | 15910篇 |
2000年 | 15893篇 |
1999年 | 12734篇 |
1998年 | 4490篇 |
1997年 | 4578篇 |
1996年 | 4376篇 |
1995年 | 4186篇 |
1994年 | 4196篇 |
1993年 | 4081篇 |
1992年 | 10766篇 |
1991年 | 10352篇 |
1990年 | 10130篇 |
1989年 | 9863篇 |
1988年 | 9241篇 |
1987年 | 8816篇 |
1986年 | 7931篇 |
1985年 | 8016篇 |
1984年 | 6594篇 |
1983年 | 5787篇 |
1982年 | 4551篇 |
1981年 | 4028篇 |
1980年 | 3831篇 |
1979年 | 6620篇 |
1978年 | 4994篇 |
1977年 | 4665篇 |
1976年 | 4303篇 |
1975年 | 4747篇 |
1974年 | 5121篇 |
1973年 | 5110篇 |
1972年 | 4749篇 |
1971年 | 4361篇 |
1970年 | 3691篇 |
1969年 | 3572篇 |
1968年 | 3191篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Interactions of luciferases isolated from Vibrio fischeri 6 and Escherichia coli JM109(pF3) (bearing cloned V. fischeri luxAB genes) with FMN reductase isolated from E. coli JM109 were studied. FMN reductase formed a stable complex with luciferase, suggesting similar properties of the FMN reductases in the taxonomically close families Vibrionaceae and Enterobacteriaceae. 相似文献
992.
A G Chuchalin V A Babushkina V Ia Arion R D Aspetov T B Sha?khinova 《Biulleten' eksperimental'no? biologii i meditsiny》1984,98(7):76-78
A study was made of the effect of T-activin on the biosynthesis of immune gamma-interferon. It was shown that in 27% of patients with chronic nonspecific pulmonary diseases, production of gamma-interferon by lymphocytes was substantially reduced during exacerbation of inflammatory process in the lungs. It was discovered that T-activin was not an interferon inductor but enhanced its synthesis in patients with a low capacity of producing immune interferon even at small doses of interferon inductor. The preparation does not produce any effect on this process in normal subjects and in patients showing the normal level of gamma-interferon. Thus T-activin can be used for stimulation of interferonogenesis. 相似文献
993.
Yanyan Han Elfriede Eppinger Ingrid G. Schuster Luise U. Weigand Xiaoling Liang Elisabeth Kremmer Christian Peschel Angela M. Krackhardt 《The Journal of biological chemistry》2009,284(48):33409-33417
The formin protein formin-like 1 (FMNL1) is highly restrictedly expressed in hematopoietic lineage-derived cells and has been previously identified as a tumor-associated antigen. However, function and regulation of FMNL1 are not well defined. We have identified a novel splice variant (FMNL1γ) containing an intron retention at the C terminus affecting the diaphanous autoinhibitory domain (DAD). FMNL1γ is specifically located at the cell membrane and cortex in diverse cell lines. Similar localization of FMNL1 was observed for a mutant lacking the DAD domain (FMNL1ΔDAD), indicating that deregulation of autoinhibition is effective in FMNL1γ. Expression of both FMNL1γ and FMNL1ΔDAD induces polarized nonapoptotic blebbing that is dependent on N-terminal myristoylation of FMNL1 but independent of Src and ROCK activity. Thus, our results describe N-myristoylation as a regulative mechanism of FMNL1 responsible for membrane trafficking potentially involved in a diversity of polarized processes of hematopoietic lineage-derived cells. 相似文献
994.
N. I. Krikunova M. B. Terenina E. L. Ruchkina T. A. Misharina 《Applied Biochemistry and Microbiology》2006,42(3):335-338
Sorption of aromatic compounds from aqueous solutions by cryotextures and suspensions of native cornstarches was studied by capillary gas chromatography. Acetophenone and benzyl alcohol were not sorbed by cryotropic-cornstarch gel and native-cornstarch suspension. A linear concentration dependence was found for aldehydes. Phenylethyl alcohol was characterized by a nonlinear concentration dependence. The presence of a benzene ring contributed to decreased binding (relative to the level characteristic of aliphatic compounds). The degree of binding depended considerably on the type of functional group in the aromatic compounds. Cryotextures were more potent than granules of native cornstarch in binding aromatic compounds. 相似文献
995.
996.
Summary Pollen mother cells at early meiotic prophase fromFritillaria lanceolata, F. mutica, Tulbaghia violacea, the lily “Formobel”,Triticum aegilopoides, T. dicoccoides, T. aestivum and synaptic and asynaptic forms ofT. durum were studied in thin sections with the electron microscope (a) in relation to distribution of nuclear pores (b) in respect
of fine structure of the pore complex in those of the first four. The pores were distributed in random clusters during leptotene
to pachytene in all plants, except in the two forms ofT. durum where there were either no pores or so few that they were not detectable. Probably correlated with this, the two membranes
of the nuclear envelope were often widely separated and frequently sacculated. No pores were seen at leptotene in the part
of the envelope to which, in theFritillarias and lily, the nucleolus was adpressed at this time. Evidence supporting a recent model which proposes that annuli are composed
of three rings of eight granular subunits was obtained. These subunits as well as a dense central element, observed in most
pores, were composed of filaments about 3 nm in diameter and evidently protein in character. There was evidence of a continuity
between filaments in the central element and those in the rings of subunits which encircle the pore aperture at both the nuclear
and cytoplasmic sides of the pore. In profiles of pores knobbed filaments were sometimes seen extending laterally from the
pore wall into the perinuclear space at two sides. Questions concerning the role of the annulus are discussed.
The author wish to thank Mr. R. F. Scott for construction to the model. 相似文献
997.
Treatment of the father with the anticancer alkylating agent cyclophosphamide has negative effects on embryonic development in the rat. Four-week treatment of male rats with a low dose of cyclophosphamide causes a dramatic, dose-dependent increase in postimplantation death of the progeny. Several recent studies have indicated that the paternal genome is required for the development of the extraembryonic tissues. Thus, the purpose of this study was to determine which tissues of the implanting embryo were affected by paternal exposure to cyclophosphamide. Male Sprague-Dawley rats were given cyclophosphamide (6 mg/kg/day) or saline by gavage and bred to untreated female rats after 4 weeks of treatment. Pregnant female rats were killed on day 7 of gestation, and implantation sites were dissected from the uterus, fixed, embedded in Epon for semithin serial sectioning, and stained for subsequent light microscopy. Strikingly, many of the implantation sites of affected embryos sired by treated males displayed an apparently normal trophectoderm enclosing a region of dying cells, containing dark-stained pyknotic nuclei. Very few or no inner cell mass-derived embryonic cells were present in these implantation sites. Therefore, there is a selective death of inner cell mass-derived cells in day 7 implantation sites obtained from the progeny of cyclophosphamide-treated males. The results of this study suggest that treatment of the male with cyclophosphamide can affect paternal genes specifically required for development of the inner cell mass cells of the embryo, without an apparent effect on those genes required for normal trophectoderm. 相似文献
998.
999.
1000.