全文获取类型
收费全文 | 2980篇 |
免费 | 336篇 |
出版年
2021年 | 42篇 |
2020年 | 26篇 |
2019年 | 32篇 |
2018年 | 43篇 |
2017年 | 35篇 |
2016年 | 48篇 |
2015年 | 108篇 |
2014年 | 109篇 |
2013年 | 124篇 |
2012年 | 159篇 |
2011年 | 144篇 |
2010年 | 94篇 |
2009年 | 108篇 |
2008年 | 117篇 |
2007年 | 131篇 |
2006年 | 124篇 |
2005年 | 116篇 |
2004年 | 100篇 |
2003年 | 99篇 |
2002年 | 98篇 |
2001年 | 80篇 |
2000年 | 89篇 |
1999年 | 66篇 |
1998年 | 38篇 |
1997年 | 33篇 |
1996年 | 26篇 |
1994年 | 25篇 |
1992年 | 53篇 |
1991年 | 64篇 |
1990年 | 52篇 |
1989年 | 44篇 |
1988年 | 54篇 |
1987年 | 28篇 |
1986年 | 47篇 |
1985年 | 44篇 |
1984年 | 49篇 |
1983年 | 33篇 |
1982年 | 46篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 29篇 |
1978年 | 28篇 |
1977年 | 29篇 |
1976年 | 27篇 |
1975年 | 26篇 |
1974年 | 42篇 |
1973年 | 30篇 |
1972年 | 34篇 |
1971年 | 25篇 |
1969年 | 25篇 |
排序方式: 共有3316条查询结果,搜索用时 109 毫秒
61.
Repeated sequences in methionyl-tRNA synthetase from E. coli 总被引:5,自引:0,他引:5
62.
63.
64.
Pulse-chase experiments in embryonic mouse fibroblasts at low and high cell population densities using radioactive phosphate and tritiated glycerol as precursors revealed a blocked turnover of phosphatidylinositol and a blocked biosynthesis of phosphatidylethan-olamine in densely packed cells. 相似文献
65.
66.
67.
68.
CHROMOSOME MICROMANIPULATION : III. Spindle Fiber Tension and the Reorientation of Mal-Oriented Chromosomes 总被引:7,自引:4,他引:3
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kinetochore reorientation is the critical process ensuring normal chromosome distribution. Reorientation has been studied in living grasshopper spermatocytes, in which bivalents with both chromosomes oriented to the same pole (unipolar orientation) occur but are unstable: sooner or later one chromosome reorients, the stable, bipolar orientation results, and normal anaphase segregation to opposite poles follows. One possible source of stability in bipolar orientations is the normal spindle forces toward opposite poles, which slightly stretch the bivalent. This tension is lacking in unipolar orientations because all the chromosomal spindle fibers and spindle forces are directed toward one pole. The possible role of tension has been tested directly by micromanipulation of bivalents in unipolar orientation to artificially create the missing tension. Without exception, such bivalents never reorient before the tension is released; a total time "under tension" of over 5 hr has been accumulated in experiments on eight bivalents in eight cells. In control experiments these same bivalents reoriented from a unipolar orientation within 16 min, on the average, in the absence of tension. Controlled reorientation and chromosome segregation can be explained from the results of these and related experiments. 相似文献
69.
A L Koch 《Journal of theoretical biology》1969,23(2):251-268
70.
Raymond M. Peterson Richard Koch Graciela E. Schaeffler Audrey Wohlers Phyllis B. Acosta David Boyle 《The Western journal of medicine》1968,108(5):350-354
One year''s experience with phenylketonuria during the calendar year 1966, the first year for compulsory newborn screening in California, was reviewed. The over-all prevalence rate from reported cases in California during this period was one case per 19,500 persons tested. Fifty-seven persons suspected of having pku were evaluated, and 25 of them were determined to be phenylketonuric. Eleven of the 25 were infants in whom the abnormality was detected through the newborn screening program or because it was detected in a sibling through a screening program. All the newborn phenylketonuric patients were developing normally at the time of last report (although the follow-up periods were short).In nine of the other children, pku was detected because they were retarded. Five retarded children who were diagnosed as phenylketonuric at another clinic were given dietary assistance.Five additional infants had elevated serum phenylalanines but did not have the classic biochemical findings of pku and are being evaluated further. Nine infants with positive screening tests exhibited biochemical and clinical findings consistent with transient tyrosinemia. Eighteen other children were evaluated and found to have no metabolic abnormality.The newborn screening program for pku is of decided benefit in early identification of a group of infants who have a high rate of potentially serious metabolic disease. Early identification permits treatment soon enough to prevent mental retardation. Newly identified patients should be evaluated in a medical setting capable of careful pediatric, biochemical and nutritional surveillance. 相似文献