全文获取类型
收费全文 | 2965篇 |
免费 | 220篇 |
国内免费 | 1篇 |
出版年
2022年 | 15篇 |
2021年 | 39篇 |
2020年 | 20篇 |
2019年 | 16篇 |
2018年 | 28篇 |
2017年 | 29篇 |
2016年 | 44篇 |
2015年 | 67篇 |
2014年 | 98篇 |
2013年 | 151篇 |
2012年 | 166篇 |
2011年 | 171篇 |
2010年 | 125篇 |
2009年 | 104篇 |
2008年 | 154篇 |
2007年 | 170篇 |
2006年 | 162篇 |
2005年 | 150篇 |
2004年 | 168篇 |
2003年 | 142篇 |
2002年 | 148篇 |
2001年 | 86篇 |
2000年 | 68篇 |
1999年 | 86篇 |
1998年 | 31篇 |
1997年 | 39篇 |
1996年 | 39篇 |
1995年 | 44篇 |
1994年 | 36篇 |
1993年 | 24篇 |
1992年 | 58篇 |
1991年 | 48篇 |
1990年 | 49篇 |
1989年 | 48篇 |
1988年 | 43篇 |
1987年 | 39篇 |
1986年 | 44篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 27篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 16篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有3186条查询结果,搜索用时 15 毫秒
1.
2.
Genotoxicity of ptaquiloside, a bracken carcinogen, in the hepatocyte primary culture/DNA-repair test 总被引:2,自引:0,他引:2
The genotoxicity of ptaquiloside (PT), recently isolated from bracken fern and shown to be carcinogenic, was examined by means of the hepatocyte primary culture/DNA-repair test. PT elicited clear unscheduled DNA synthesis with a dose-response effect. The result indicates that PT is a genotoxic carcinogen. 相似文献
3.
Eiji Niwa En-Sheng Chen Satoshi Kanoh Teruo Nakayama 《Bioscience, biotechnology, and biochemistry》2013,77(11):3067-3071
The linearity of the stress-strain relationship for food gel is limited to a very narrow range of the strain (usually less than 0.1 as a Cauchy measure). The reason is thought due to the change in cross-sectional area of the gel upon deformation. In this report, the cross-sectional area was approximately corrected of the compressed gel on the assumption that the gel expanded uniformly without changing its volume upon compression. In cases when the initial Young’s modulus was calculated from the thus-corrected area for some food gels, the linearity was increased for a wider range of strain. 相似文献
4.
Hidekatsu Yokoyama Shin-ichi Niwa Kenji Itoh Reiko Mazuka 《Biological cybernetics》1996,75(2):137-140
On the basis of a temporal model of animal behavior we conducted temporal analysis of eye movements in schizophrenic subjects
(n=10) and normal controls (n=10). We found a fractal property in schizophrenic subjects, the fixation time of eye movement during reading ambiguous and
difficult sentences showing a clear inverse power law distribution. An exponential distribution of a nonfractal nature was
found in normal controls.
Received: 21 July 1995/Accepted in revised form: 30 April 1996 相似文献
5.
Feedbacks between nutrient cycling and vegetation predict plant species coexistence and invasion 总被引:5,自引:0,他引:5
To investigate the role of species‐specific litter decomposability in determining plant community structure, we constructed a theoretical model of the codevelopmental dynamics of soil and vegetation. This model incorporates feedback between vegetation and soil. Vegetation changes the nutrient conditions of soil by affecting mineralization processes; soil, in turn, has an impact on plant community structure. The model shows that species‐level traits (decomposability, reproductive and competitive abilities) determine whether litter feedback effects are positive or negative. The feedback determines community‐level properties, such as species composition and community stability against invasion. The model predicts that positive feedback may generate multiple alternative steady states of the plant community, which differ in species richness or community composition. In such cases, the realized state is determined by initial abundance of co‐occurring species. Further, the model shows that the importance of species‐level traits depends on environmental conditions such as system fertility. 相似文献
6.
O Niwa T Saigusa T Ikushima T Sugahara 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1987,52(6):949-956
The effect of thermal neutrons on the induction of murine endogenous viruses from a mouse fibroblast cell line was investigated. Thermal neutrons were more effective than X-rays in induction of endogenous virus as well as in killing of the cells. However, when measured as a function of cell killing, both radiations had similar efficiency of induction. The RBEs of thermal neutrons alone were calculated on the assumption that the contribution of contaminating gamma-rays was additive. It was 4.2 for the killing effect and 4-5 for virus induction. 相似文献
7.
An electrophoretic karyotype for Schizosaccharomyces pombe by pulsed field gel electrophoresis. 总被引:44,自引:25,他引:19
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
C L Smith T Matsumoto O Niwa S Klco J B Fan M Yanagida C R Cantor 《Nucleic acids research》1987,15(11):4481-4489
The three chromosomal DNAs of S. pombe have been fractionated by pulsed field gel electrophoresis. The resulting molecular karyotype will greatly speed gene mapping in this organism, and it indicates that the separation range of the technique extends to DNA molecules as large as 9,000,000 base pairs. 相似文献
8.
9.
Spontaneous excretion of D-alanine in urine in mutant mice lacking D-amino-acid oxidase. 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Urine from mutant mice lacking D-amino-acid oxidase contained a large amount of alanine compared with that from normal mice. Urinary alanine of the mutant mice was sensitive to D-amino-acid oxidase. H.p.l.c. showed that about 94% of the urinary alanine had the D-configuration. These results suggest that D-amino-acid oxidase functions to decompose D-amino acid(s) in normal mice. 相似文献
10.
Characterization of Schizosaccharomyces pombe minichromosome deletion derivatives and a functional allocation of their centromere. 总被引:8,自引:1,他引:7
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A 530 kb long Schizosaccharomyces pombe linear minichromosome, Ch16, containing a centric region of chromosome III, has previously been made. In the present study, we constructed a number of deletions in the right and/or left arms of Ch16, and compared their structure and behaviour with Ch16. The functional centromere, cen3, is allocated within a 120 kb long region which is covered by the shortest derivative, Ch10, and is comprised mostly of centromeric repeating sequences. The shortest minichromosome is stable in mitosis and the copy number control is apparently precise. In monosomic meiosis it segregates normally. In disomic meioses, however, the frequency of non-disjunction is very high, suggesting that it may not form a pair. The mitotic loss rate of one of the left-arm deletions, ChR32, which lacks a part of the centromeric repeating sequence, is the highest of all the deletions. This deletion also exhibits the highest precocious sister chromatid separation in meiosis I, suggesting that sister chromatid association might become weakened in ChR32. Our results indicate that the proper meiotic segregation of S.pombe minichromosomes is dependent upon the formation of a bivalent. S.pombe may not have the 'distributive segregation' found with Saccharomyces cerevisiae minichromosomes. 相似文献