全文获取类型
收费全文 | 8987篇 |
免费 | 799篇 |
出版年
2021年 | 80篇 |
2019年 | 64篇 |
2018年 | 96篇 |
2017年 | 82篇 |
2016年 | 144篇 |
2015年 | 222篇 |
2014年 | 262篇 |
2013年 | 364篇 |
2012年 | 457篇 |
2011年 | 439篇 |
2010年 | 278篇 |
2009年 | 297篇 |
2008年 | 404篇 |
2007年 | 407篇 |
2006年 | 397篇 |
2005年 | 391篇 |
2004年 | 383篇 |
2003年 | 454篇 |
2002年 | 462篇 |
2001年 | 217篇 |
2000年 | 149篇 |
1999年 | 201篇 |
1998年 | 156篇 |
1997年 | 138篇 |
1996年 | 132篇 |
1995年 | 112篇 |
1994年 | 94篇 |
1993年 | 96篇 |
1992年 | 166篇 |
1991年 | 132篇 |
1990年 | 103篇 |
1989年 | 116篇 |
1988年 | 118篇 |
1987年 | 127篇 |
1986年 | 90篇 |
1985年 | 126篇 |
1984年 | 104篇 |
1983年 | 82篇 |
1982年 | 99篇 |
1981年 | 108篇 |
1980年 | 92篇 |
1979年 | 112篇 |
1978年 | 103篇 |
1977年 | 75篇 |
1976年 | 76篇 |
1975年 | 67篇 |
1974年 | 76篇 |
1973年 | 64篇 |
1971年 | 62篇 |
1970年 | 62篇 |
排序方式: 共有9786条查询结果,搜索用时 713 毫秒
41.
42.
43.
Summary A new restriction fragment length polymorphism detected with the restriction endonuclease BglII (AGATCT) is presented. 相似文献
44.
Methanogenic bacteria as a key factor involved in changes of town gas stored in an underground reservoir 总被引:1,自引:0,他引:1
P. migá M. Greksák J. Kozánková F. Buzek V. Onderka I. Wolf 《FEMS microbiology letters》1990,73(3):221-224
Growth of Phanerochaete chrysosporium in a nitrogen-limited medium buffered with sodium acetate, instead of the commonly used 2,2-dimethylsuccinate (DMS), resulted in quantitative and qualitative differences in the production of various extracellular lignin peroxidases (LIPs) and manganese-dependent peroxidases (MNPs) involved in lignin degradation. The results indicate that production of LIPs and MNPs can be selectively enhanced by manipulation of culture conditions. Partial N-terminal analyses of the major LIPs and MNPs have made it possible to assign a specific protein to the specific genes and cDNAs that have been reported recently. The LIPs and MNPs differed widely in their ability to decolorize various dyes that are known to be degraded by the lignin degrading enzyme system of P. chrysosporium. 相似文献
45.
46.
Marc-Henri Stern Fangrong Zhang Gilles Thomas Claude Griscelli Alain Aurias 《Human genetics》1988,81(1):18-22
Summary To delimit the 14q32.1 recurrent breakpoint of ataxia telangiectasia clones, we performed an in situ hybridization study with various probes located on the 14q32 band. We thus mapped this breakpoint between the D14S1 and Pi loci. Furthermore, an interstitial duplication including D14S1 and a part of the IgH locus was demonstrated on a t(14;14) clone. 相似文献
47.
Raymond Hellio Dr. Claude Fréhel Jean-Yves Rauzier Nalin Rastogi 《Current microbiology》1988,17(4):235-242
Cytochemical characterization of mycobacterial surfaces was carried out on virulent (H37Rv) and avirulent (H37Ra) strains ofMycobacterium tuberculosis. The results were quantified and compared with those obtained with three colony types of the opportunistic pathogenMycobacterium avium. Mycobacterium aurum, a rapidly growing, nonpathogenic species, served as a model for the cytochemical methods. Concanavalin A (ConA) reacted with -d-mannose and -d-glucose residues, whereas negative charged residues were detected with either the ionized ferritin (CF) or the colloidal ferric hydroxide (CIH) method. Strongly acidic sulfate groups were detected by their selective blockage with alcian blue (AB) at pH 1 prior to the CIH labeling at pH 1.8. Weakly acidic groups were demonstrated by AB blockage at pH 2.5 prior to staining with CF stain. Except forM. aurum, all other strains showed a marked heterogeneity in regard to the abundance of their surface labeling. Accessible sulfate groups were present on the cell surface of the virulent H37Rv strain ofM. tuberculosis, but not on the avirulent strain H37Ra. Distribution of ConA receptors, on the other hand, was unrelated to the virulence or pathogenicity of the bacterial strain. 相似文献
48.
E. Tichatschek C. C. Zielinski Ch. Müller P. Sevelda E. Kubista K. Czerwenka J. Spona H. Wolf M. M. Eibl 《Cancer immunology, immunotherapy : CII》1988,27(3):278-282
Summary Unstimulated IFN- and IL2-stimulated (NK) cell activities were investigated in patients with breast cancer who had received either local radiotherapy alone or adjuvant chemotherapeutic treatment with CMF combined with radiotherapy 12 to 18 months previously. When tested against the primarily NK-sensitive K562 cell line, patients who had received adjuvant chemotherapeutic treatment with CMF were shown to have a significantly decreased unstimulated and IFN-stimulated NK cell activity, as compared to both patients after radiotherapy only (P<0.002) and P<0.005, respectively) and healthy control persons (P<0.05). The former group of patients also had a significantly decreased IFN-stimulated NK cell activity, when tested against the primarily NK-insensitive Chang hepatoma cell line, as compared to patients after radiotherapy only (P<0.005) and healthy controls (P<0.05). Moreover, patients after radiotherapy only proved to have a significantly increased unstimulated (P<0.01) and IFN-stimulated NK cell activity (K562: P<0.05; Chang hepatoma cell line: P<0.05), as compared to healthy control individuals. In contrast, no difference in IL2-stimulated NK cell activity was detected. The investigation for the expression of CD3 and/or Leu 19 antigens as phenotypic markers of cells with non-MHC restricted cytotoxicity showed a significantly lower percentage of cells with the CD3+ phenotype in patients with breast cancer, irrespective of the chosen post-operative treatment, as compared to healthy controls (P<0.01). Finally, patients with breast cancer who had received radiotherapy only had a significant trend towards an increased percentage of CD3+/Leu 19+ PMNC, as compared to both patients after CMF treatment (P<0.05) and healthy controls (P<0.025). We conclude that patients with breast cancer vary on a long-term basis in their NK activity and in the phenotype of their PMNC depending on their post-operative adjuvant management.Abbreviations NK
natural killer cells
- IFN
interferon
- IL 2
interleukin 2
- CMF
cyclophosphamide, methotrexate, fluorouracil
- ER
oestrogen receptor
- PMNC
peripheral blood mononuclear cells
- MHC
major histocompatibility complex
- CTL
cytotoxic T lymphocytes 相似文献
49.
Synopsis Evidence is presented which suggests that the nonparasitic lamprey, Lampetra (Eudontomyzon) gracilis Kux, 1965, is conspecific with the parasitic lamprey Eudontomyzon danfordi Regan, 1911. The diagnostic characters of the holotype and of the non-type material of E. gracilis are features found in E. danfordi specimens in their second and final year of adult life, thereby making the former a junior synonym of the latter. 相似文献
50.
Properties of the 12-O-Tetradecanoylphorbol-13-Acetate-Stimulated S6 Kinase from Rat Astroglial Cells 总被引:1,自引:0,他引:1
Danièle Toru-Delbauffe Jean-Michel Gavaret Claude Jacquemin Carole Matricon Martine Pomerance Michel Pierre 《Journal of neurochemistry》1988,51(5):1448-1454
The S6 kinase activity of astroglial cells in primary culture stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) has been studied. This activity was eluted as a single peak at 0.15 M NaCl from a DEAE-Sephacel column. The chromatography of this peak on phosphocellulose revealed an activity eluted at 0.15 M NaCl. This partially purified enzyme had a sedimentation coefficient of 3.7S; Km values were 2 X 10(-5) M for ATP and 10(-6) M for 40S ribosomal subunits. The optimal Mg2+ concentration requirement was 2-3 mM. Mn2+ and Co2+ could substitute for Mg2+ (optimum concentrations 1.5 and 0.8 mM, respectively), but these cations were strong inhibitors in the presence of Mg2+. The enzyme was inhibited by N-ethylmaleimide, indicating that it contained thiol groups. This S6 kinase used ATP, but not GTP, as a phosphate donor, and exhibited great specificity for S6 as phosphate acceptor. Whole histones and protamine were slightly phosphorylated whereas phosvitin, histone H1, and surprisingly the peptide Arg-Arg-Leu-Ser-Ser-Leu-Arg-Ala were not phosphorylated. The TPA-stimulated S6 kinase resembles the insulin-, fibroblast growth factor- and cyclic AMP-stimulated enzymes, suggesting that several pathways might activate the same entity. 相似文献