全文获取类型
收费全文 | 770830篇 |
免费 | 90815篇 |
国内免费 | 563篇 |
专业分类
862208篇 |
出版年
2016年 | 8308篇 |
2015年 | 12358篇 |
2014年 | 14157篇 |
2013年 | 20172篇 |
2012年 | 22793篇 |
2011年 | 23000篇 |
2010年 | 15259篇 |
2009年 | 14255篇 |
2008年 | 20271篇 |
2007年 | 21097篇 |
2006年 | 19527篇 |
2005年 | 19131篇 |
2004年 | 18847篇 |
2003年 | 17998篇 |
2002年 | 17533篇 |
2001年 | 34950篇 |
2000年 | 35656篇 |
1999年 | 28492篇 |
1998年 | 10141篇 |
1997年 | 10487篇 |
1996年 | 10036篇 |
1995年 | 9304篇 |
1994年 | 9274篇 |
1993年 | 9146篇 |
1992年 | 22955篇 |
1991年 | 22084篇 |
1990年 | 21571篇 |
1989年 | 21086篇 |
1988年 | 19367篇 |
1987年 | 18628篇 |
1986年 | 17463篇 |
1985年 | 17320篇 |
1984年 | 14526篇 |
1983年 | 12546篇 |
1982年 | 10001篇 |
1981年 | 9133篇 |
1980年 | 8418篇 |
1979年 | 14075篇 |
1978年 | 11096篇 |
1977年 | 10201篇 |
1976年 | 9559篇 |
1975年 | 10484篇 |
1974年 | 11453篇 |
1973年 | 11278篇 |
1972年 | 10357篇 |
1971年 | 9470篇 |
1970年 | 8085篇 |
1969年 | 7960篇 |
1968年 | 7185篇 |
1967年 | 6183篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
R Mendelsohn J W Brauner L Faines H H Mantsch R A Dluhy 《Biochimica et biophysica acta》1984,774(2):237-246
Glycophorin has been isolated in pure form from human erythrocyte membranes and reconstituted into lipid vesicles composed of binary mixtures of bovine brain phosphatidylserine (PS) and acyl-chain perdeuterated dipalmitoylphosphatidylcholine (DPPC-d62). The effect of protein on lipid melting behavior and order has been monitored with differential scanning calorimetry and Fourier transform infrared spectroscopy (FT-IR). The phase diagram for PS/DPPC-d62 is consistent with that previously reported for PS/DPPC (Stewart et al. (1979) Biochim. Biophys. Acta 556, 1-16) and indicates that acyl chain perdeuteration does not greatly alter the lipid mixing characteristics. The use of deuterated lipid allows the examination of lipid order by FT-IR of each lipid component in the binary mixtures as well as in the ternary (lipid/lipid/protein) systems. Addition of glycophorin to a 30:70 PS/DPPC-d62 binary lipid mixture results in a preferential glycophorin/PS interaction leading to bulk lipid enriched in DPPC-d62. This is revealed in two ways: first, through cooperative calorimetric transitions increased in temperature from the binary lipid system and second, through FT-IR melting curves of the DPPC-d62 component which shows transitions increased in both onset and completion temperatures in the presence of protein. In addition, non-cooperative melting events are observed at temperatures below the onset of phase separation. The FT-IR data are used to assign these non-cooperative events to the melting of the PS component. For the 50:50 lipid mixture with protein, two transitions are observed in the DSC experiments. The IR results indicate that both lipid components are involved with the lower temperature event. 相似文献
992.
H. -D. Pfannenstiel 《Helgoland Marine Research》1985,39(1):49-53
The dye Lucifer yellow CH was iontophoresed into recently fertilized eggs and early blastomeres ofHydractinia echinata. Iontophoresis was carried out on the stage of an inverted microscope in order to follow filling of the injected cells by short pulses of epifluorescent illumination. Lucifer yellow proved to be nontoxic and development in embryos with injected blastomeres proceeded normally. When zygotes were injected all the cells of the forming embryo contained dye. When one of the first two blastomeres was injected all the progeny of the injected cell also contained dye. Dye-coupling between injected and uninjected blastomeres did not occur in two-cell embryos nor between descendants of either line. Development of Lucifer-yellow-filled blastomeres or zygotes could be stopped by blue light irradiation. In a number of injected cells, the dye tended to accumulate forming brightly shining spots. The dye did not penetrate the nuclear envelope of injected cells. 相似文献
993.
Timm-staining intensity is correlated with the density of Timm-positive presynaptic structures in the cerebral cortex of lizards 总被引:1,自引:0,他引:1
In cortical areas of the lizard, Podarcis hispanica, Timm staining reveals a distinct pattern of lamination. At the electron-microscope level, virtually all of the reaction product is located in the synaptic vesicles of Timm-positive boutons. Using linear-regression analysis, the area density of Timm-positive bouton profiles as well as the numerical and volume density of stained vesicles were found to be closely correlated with the light-microscopic densitometric values obtained for each Timm-positive cortical zone. We discuss the possibility of estimating stereological electron-microscopic data parameters from densitometric measurements at the light-microscope level. 相似文献
994.
Mary H. Moran 《American anthropologist》1998,100(1):235-236
Wives and Warriors: Women and the Military in the United States and Canada. Laurie Weinstein and Christie C. White. eds. Westport, CT: Bergin and Garvey, 1997. 252 pp. 相似文献
995.
996.
997.
998.
A number of drugs cause marked increases in the steroid hydroxylase activity of hepatic microsomes. Beginning 2 days after estrus, 117 mature ewes were each given 14 injections over a 27-day period of phenobarbital sodium, diphenylhydantoin, chlorcyclizine HCl or phenylbutazone. Blood samples for luteinizing hormone (LH) and progesterone determination by radioimmunoassay (RIA) were taken on day 10 of the first estrous cycle (day 18 if no heat was observed) and on days 5 and 10 of the second cycle. On day 10 of the second cycle, the ewes were given an intravenous injection of 1 ml of 6% solution of pentobarbitol sodium anesthetic per 4.5 kg body weight, and the length of anesthetic sleep time was measured. The ewes were then killed and corpora lutea and liver were weighed.In 33 ewes treated with either phenobarbitol sodium or phenylbutazone, sleep time was shortened (18 min 29 min in untreated controls, P<.01), indicating that enzyme induction had occurred. For 41 ewes treated with either chlorcyclizine HCl or diphenylhydantoin, sleep time was lengthened to 93 min (P<.01 controls), indicating impaired liver function. Electron micrographs of liver cells verified that enzyme induction or hepatic degeneration had occurred. 相似文献
999.
The distribution, synthesis transport, and glycosylation of rat-liver DT-diaphorase has been investigated. The enzyme could be isolated using specific antibodies, mainly from the soluble supernatant but also from microsomal vesicles, Golgi membrane, and mitochondria. 40% of the microsomal enzyme was located in the lumen or on the interior side of the membrane, the rest remaining as an integral non-extractable part of the membrane. Synthesis of DT-diaphorase takes place on both free and bound ribosomes, although it was found to be transported in a sequential manner from the rough to the smooth endoplasmic reticulum and also subsequently to the mitochondria. The rough and smooth microsomal DT-diaphorase contains covalently bound carbohydrate, but no sugar moiety could be detected bound to the cytoplasmic form of the enzyme. 相似文献
1000.