全文获取类型
收费全文 | 594篇 |
免费 | 50篇 |
出版年
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 21篇 |
2014年 | 22篇 |
2013年 | 32篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 32篇 |
2009年 | 29篇 |
2008年 | 25篇 |
2007年 | 25篇 |
2006年 | 23篇 |
2005年 | 31篇 |
2004年 | 21篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 18篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有644条查询结果,搜索用时 15 毫秒
1.
2.
Ricardo Benavente Marie Christine Dabauvalle Ulrich Scheer Nathalie Chaly 《Chromosoma》1989,98(4):233-241
Many nuclear proteins are released into the cytoplasm at prometaphase and are transported back into the daughter nuclei at the end of mitosis. To determine the role of this reentry in nuclear remodelling during early interphase, we experimentally manipulated nuclear protein uptake in dividing cells. Recently we and others have shown that signal-dependent, pore complex-mediated uptake of nuclear protein is blocked in living cells on microinjection of the lectin wheat germ agglutinin (WGA), or of antibodies such as PI1 that are directed against WGA-binding pore complex glycoproteins. In the present study, we microinjected mitotic PtK2 cells with WGA or antibody PI1 and followed nuclear reorganization of the daughter cells by immunofluorescence and electron microscopy. The inhibitory effect on nuclear protein uptake was monitored by co-injection of the karyophilic protein nucleoplasmin. When injected by itself early in mitosis, nucleoplasmin became sequestered into the daughter nuclei as they entered telophase. In contrast, nucleoplasmin was excluded from the daughter nuclei in the presence of WGA or antibody PI1. Although PtK2 cells with blocked nuclear protein uptake completed cytokinesis, their nuclei showed a telophaselike organization characterized by highly condensed chromatin surrounded by a nuclear envelope containing a few pore complexes. These findings suggest that pore complexes become functional as early as telophase, in close coincidence with nuclear envelope reformation. They further indicate that the extensive structural rearrangement of the nucleus during the telophase-G1 transition is dependent on the influx of karyophilic proteins from the cytoplasm through the pore complexes, and is not due solely to chromosome-associated components.Abbreviations
WGA
wheat germ agglutinin
-
GlcNAc
N-acetylglucosamine 相似文献
3.
4.
5.
Solubilization and partial characterization of rat epididymal delta 4-steroid 5 alpha-reductase (cholestenone 5 alpha-reductase). 总被引:1,自引:0,他引:1 下载免费PDF全文
Epididymal delta 4-steroid 5 alpha-reductase (cholestenone 5 alpha-reductase), the enzyme that catalyses the conversion of testosterone into the biologically active metabolite dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one), is a membrane-bound enzyme found in both nuclear and microsomal subcellular fractions. In order to characterize epididymal delta 4-steroid 5 alpha-reductase, it was first necessary to solubilize the enzymic activity. Of the various treatments tested, a combination of 0.5% (w/v) Lubrol WX, 0.1 M-sodium citrate and 0.1 M-KCl maintained enzymic activity at control values and solubilized 66% of total epididymal delta 4-steroid 5 alpha-reductase activity in an active and stable form. The sedimentation coefficient of solubilized delta 4-steroid 5 alpha-reductase, as determined in continuous sucrose density gradients, was greater for the microsomal than for the nuclear enzyme (11.6S compared with 10.1S). Although the apparent Km values of the enzyme for testosterone were similar in nuclear and microsomal subcellular fractions (range 1.75 x 10(-7) - 4.52 x 10(-7)M), the apparent Km of the enzyme for NADPH was about 30-fold greater for the microsomal enzyme than for the nuclear enzyme. The apparent Km of the enzyme for either substrate was not significantly altered after solubilization. The relative capacity of steroids to inhibit the enzymic activity, the pH optima and the effects of Ca2+ and Mg2+ were similar for membrane-bound and solubilized delta 4-steroid 5 alpha-reductase in both the nuclear and the microsomal fractions. The results reported demonstrate that epididymal delta 4-steroid 5 alpha-reductase can be solubilized in an active and stable form with no significant changes in the kinetic characteristics of the enzyme after solubilization; furthermore, kinetic and molecular-size differences observed for the nuclear and the microsomal forms of the enzyme suggest that there may exist at least two forms of epididymal delta 4-steroid 5 alpha-reductase. 相似文献
6.
7.
8.
9.
Mark A. Batzer Santosh S. Arcot Joshua W. Phinney Michelle Alegria-Hartman David H. Kass Stephen M. Milligan Colin Kimpton Peter Gill Manfred Hochmeister Panayiotis A. Ioannou Rene J. Herrera Donald A. Boudreau W. Douglas Scheer Bronya J. B. Keats Prescott L. Deininger Mark Stoneking 《Journal of molecular evolution》1996,42(1):22-29
The Alu family of intersperesed repeats is comprised of ovr 500,000 members which may be divided into discrete subfamilies based upon mutations held in common between members. Distinct subfamilies of Alu sequences have amplified within the human genome in recent evolutionary history. Several individual Alu family members have amplified so recently in human evolution that they are variable as to presence and absence at specific loci within different human populations. Here, we report on the distribution of six polymorphic Alu insetions in a survey of 563 individuals from 14 human population groups across several continents. Our results indicate that these polymorphic Alu insertions probably have an African origin and that there is a much smaller amount of genetic variation between European populations than that found between other populations groups.
Present address: Department of Pathology, Stanley S. Scott Cancer Center, Louisiana State University Medical Center, 1901 Perdido St., New Orleans, LA 70112
Correspondence to: M.A. Batzer 相似文献
10.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献