全文获取类型
收费全文 | 491507篇 |
免费 | 47726篇 |
国内免费 | 210篇 |
专业分类
539443篇 |
出版年
2018年 | 5434篇 |
2017年 | 4971篇 |
2016年 | 6812篇 |
2015年 | 9015篇 |
2014年 | 10204篇 |
2013年 | 14818篇 |
2012年 | 16303篇 |
2011年 | 16190篇 |
2010年 | 10962篇 |
2009年 | 9554篇 |
2008年 | 14094篇 |
2007年 | 14560篇 |
2006年 | 13871篇 |
2005年 | 12835篇 |
2004年 | 12949篇 |
2003年 | 12430篇 |
2002年 | 12057篇 |
2001年 | 18917篇 |
2000年 | 18903篇 |
1999年 | 15230篇 |
1998年 | 5553篇 |
1997年 | 5692篇 |
1996年 | 5474篇 |
1995年 | 5142篇 |
1994年 | 5018篇 |
1992年 | 13026篇 |
1991年 | 12785篇 |
1990年 | 12768篇 |
1989年 | 12608篇 |
1988年 | 11782篇 |
1987年 | 11143篇 |
1986年 | 10418篇 |
1985年 | 10875篇 |
1984年 | 8982篇 |
1983年 | 7766篇 |
1982年 | 6031篇 |
1981年 | 5408篇 |
1980年 | 5062篇 |
1979年 | 8663篇 |
1978年 | 6751篇 |
1977年 | 6371篇 |
1976年 | 6074篇 |
1975年 | 6661篇 |
1974年 | 7253篇 |
1973年 | 7106篇 |
1972年 | 6606篇 |
1971年 | 5973篇 |
1970年 | 5249篇 |
1969年 | 5310篇 |
1968年 | 4961篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Studies of gastric morphology in North American Chiroptera (Emballonuridae, Noctilionidae, and Phyllostomatidae) 总被引:1,自引:0,他引:1
G L Forman 《Journal of mammalogy》1973,54(4):909-923
912.
P Minoia G M Lacalandra A Zarrilli 《Bollettino della Società italiana di biologia sperimentale》1983,59(11):1625-1630
In this experiment we used nine goats to which we administered GnRH in fractioned doses at a pulse like rhythm in order to obtain follicular growth and oestrus. The average length of treatment was 5.5 days; the animals were injected with a daily amount of 0.05 mg of GnRH subdivided in three doses (0.017 mg each). All the 9 experimental goats came into oestrus and became pregnant. The GnRH treatment in fractioned and repeated daily doses proves a valid method to induce follicular growth and ovulation in anoestrus goats. 相似文献
913.
Using a sequential method for the simultaneous demonstration of lysozyme and mucins, the possible existence of a transitional cell intermediate in form between Paneth and goblet cells has been investigated in childhood coeliac disease. Mixed staining for both mucins and lysozyme has not been encountered within intestinal cells of affected mucosae and controls. 相似文献
914.
915.
C. M. Hooijmans T. A. Abdin G. J. Alaerts 《Applied microbiology and biotechnology》1995,43(5):781-785
Lipid phosphate, which is a measure of viable biomass, was determined using biofilm samples from three different laboratory-scale
reactors. The analysis procedure proposed in the literature was modified and tested for suitability in experiments with biofilm
reactors. The microbial contents of the biofilms studied are compared in three types of reactor.
Received: 2 November 1994/Accepted: 23 January 1995 相似文献
916.
Role of different lymphoid tissues in the initiation and maintenance of DNA-raised antibody responses to the influenza virus H1 glycoprotein. 下载免费PDF全文
Antibody responses in mice immunized by a single gene gun inoculation of plasmid expressing the influenza virus H1 hemagglutinin and in mice immunized by a sublethal H1 influenza virus infection have been compared. Both immunizations raised long-lived serum responses that were associated with the localization of antibody-secreting cells (ASC) to the bone marrow. However, the kinetics of these responses were 4 to 8 weeks slower in the DNA-immunized than in the infection-primed mice. Following a gene gun booster, the presence of ASC in the inguinal lymph nodes, but not in other lymph nodes, revealed gene gun responses being initiated in the nodes that drain the skin target site. Both pre- and postchallenge, the DNA-immunized mice had 5- to 10-times-lower levels of antibody and ASC than the infection-primed mice. 相似文献
917.
C Holliger S W Kengen G Schraa A J Stams A J Zehnder 《Journal of bacteriology》1992,174(13):4435-4443
Reductive dechlorination of 1,2-dichloroethane (1,2-DCA) to ethylene and chloroethane (CA) by crude cell extracts of Methanobacterium thermoautotrophicum delta H with H2 as the electron donor was stimulated by Mg-ATP. The heterodisulfide of coenzyme M (CoM) and 7-mercaptoheptanoylthreonine phosphate together with Mg-ATP partially inhibited ethylene production but stimulated CA production compared Mg-ATP alone. The pH optimum for the dechlorination was 6.8 (at 60 degrees C). Michaelis-Menten kinetics for initial product formation rates with different 1,2-DCA concentrations indicated the enzymatic character of the dechlorination. Apparent Kms for 1,2-DCA of 89 and 119 microM and Vmaxs of 34 and 20 pmol/min/mg of protein were estimated for ethylene and CA production, respectively. 3-Bromopropanesulfonate, a specific inhibitor for methyl-CoM reductase, completely inhibited dechlorination of 1,2-DCA. Purified methyl-CoM reductase, together with flavin adenine dinucleotide and a crude component A fraction which reduced the nickel of factor F430 in methyl-CoM reductase, converted 1,2-DCA to ethylene and CA with H2 as the electron donor. In this system, methyl-CoM reductase was also able to transform its own inhibitor 2-bromoethanesulfonate to ethylene. 相似文献
918.
T Werfel G Sonntag M H Weber O G?tze 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(11):3909-3914
Rapid increases in the membrane expression of C3 receptors on granulocytes and monocytes in response to the anaphylatoxin C5a have previously been described. In this study we demonstrate increases in the membrane expression of neutral endopeptidase (NEP, CD10, CALLA), aminopeptidase N (APN, CD13), tyrosine phosphatase (CD45/CD45Ro) and the Fc R Fc gamma-RIII (CD16) on granulocytes within minutes of treatment with human C5a. Monocytes responded to C5a with increases in CD13 and CD45/CD45Ro. These membrane modulations could be prevented by preincubating the C5a preparations with anti-C5a mAb C17/5 but not by pretreating the cells with cycloheximide. Increases of CD10, CD13, and CD11b but not CD11a (LFA-1) were also observed in leukocytes from patients undergoing hemodialysis with cuprophan membranes. The increase of CD16 on granulocytes was dependent on the presence of plasma during in vitro activation with C5a indicating that plasma contains inhibitors which prevent the previously described loss of Fc gamma-RIII upon stimulation of the cells. 相似文献
919.
920.