全文获取类型
收费全文 | 1144篇 |
免费 | 54篇 |
出版年
2022年 | 9篇 |
2021年 | 17篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 7篇 |
2016年 | 19篇 |
2015年 | 41篇 |
2014年 | 48篇 |
2013年 | 69篇 |
2012年 | 84篇 |
2011年 | 62篇 |
2010年 | 38篇 |
2009年 | 39篇 |
2008年 | 41篇 |
2007年 | 75篇 |
2006年 | 56篇 |
2005年 | 55篇 |
2004年 | 43篇 |
2003年 | 59篇 |
2002年 | 40篇 |
2001年 | 21篇 |
2000年 | 20篇 |
1999年 | 19篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 25篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1974年 | 6篇 |
1968年 | 6篇 |
1966年 | 6篇 |
1965年 | 5篇 |
1964年 | 7篇 |
排序方式: 共有1198条查询结果,搜索用时 31 毫秒
21.
The low percentage of living bacteria commonly obtained when comparing viable counts with total direct counts in seawater could be due more to inappropriate techniques for appreciating the growth ability of living cells than to unadapted culture conditions. The most-probable-number counts in filtered seawater cultures and the microscopic counts of 4(prm1),6-diamidino-2-phenylindole (DAPI)-stained aggregate-forming units grown on black polycarbonate filters appeared significantly correlated to the direct counts. Both these techniques show that in the superficial and intermediate water masses, the living cells may constitute an important (frequently higher than 20%) but highly variable part of the total populations. These viable counts appear more realistic than the conventional CFU counts, which provide only 0.001 to 0.2% of the total counts. 相似文献
22.
Giuliano Callaini Maria Giovanna Riparbelli Marcella Cintorino Sergio Antonio Tripodi Giorgio Bianciardi Piero Tosi Romano Dallai 《Biology of the cell / under the auspices of the European Cell Biology Organization》1994,81(1):39-45
Summary— Immunofluorescence and immunoelectron microscopy indicated that the antibody raised against the nuclear antigen Ki-67 of mammalian cells recognized antigenic determinants of early Drosophila embryos, localized on the outside of the nuclear envelope. Hence, the nuclear envelope of Drosophila appears to share a similar epitope with the chromosome scaffold of mitotic mammalian cells. With the progression of mitosis the antigen persisted around the mitotic spindle region and was also found in the pole regions at metaphase and anaphase. The antibody also stained the equatorial regions of the spindles from anaphase to late telophase. The antibody may therefore be used as a biochemical marker of the nuclear envelope for studying nuclear membrane biogenesis and behavior during the mitotic divisions of the Drosophila embryo. 相似文献
23.
Maria Giovanna Riparbelli Romano Dallai Giuliano Callaini 《Biology of the cell / under the auspices of the European Cell Biology Organization》1993,78(3):223-227
Rhodamine phalloidin-staining was used to study the organization of the cortical actin cytoskeleton of the early Ceratitis capitata embryo. The dynamics of the actin aggregates and their changes in distribution during the formation of the syncytial blastoderm, were followed in detail. It was found that these aggregates formed a shell-like cluster around the interphase nuclei, and concentrated toward the poles of the mitotic apparatus when the nuclei divided. Laser scanning confocal microscopy revealed that aggregates not clustered at the poles of the mitotic apparatus were closely associated with fine fibers of a dense cytoplasmic network of actin filaments. 相似文献
24.
25.
P. Rizzu E. A. Lindsay C. Taylor H. O’Donnell A. Levy P. Scambler A. Baldini 《Mammalian genome》1996,7(9):639-643
We have identified and cloned a gene, ES2, encoding a putative 476 amino acid protein with a predicted M
r
of 52,568. The gene is localized within the DiGeorge/Velocardiofacial syndrome locus on 22q11.2 and is deleted in all the
patients in which a deletion within 22q11 could be demonstrated, with the exception of one patient. ES2 is expressed in all
the tissues studied. Sequence comparison showed identity with five ESTs and at the amino acid level the sequence was highly
similar to, and collinear with, a hypothetical C. elegans protein of unknown function. Mutation analysis was performed in 16 patients without deletion, but no mutation has been found.
The cDNA sequence is conserved in mouse and is localized on MMU16B1-B3, known to contain a syntenic group in common with HSA
22q11.2.
Received: 25 March 1996 / Accepted: 15 May 1996 相似文献
26.
Nicoletta Zini Katia Scotlandi Nicola Baldini Giuseppe Nini Patrixia Sabatelli Nadir M Maraldi 《Biology of the cell / under the auspices of the European Cell Biology Organization》1995,84(3):195-204
Summary— Multidrug-resistant (MDR) variants of a human osteosarcoma cell line (U-2 OS) have been recently obtained by continuous exposure to doxorubicin (DX). The growth and phenotypic characteristics of these cell lines have been demonstrated to be related to the level of expression of P-glycoprotein. In this work, the morphological changes associated with MDR have been evaluated by quantitative image analysis and transmission electron microscopy. Resistant cells present morphological changes with respect to sensitive cells at both cytoplasmic and nuclear level. Some of these changes appear to be related to the degree of resistance but not to the direct presence of DX, since deprived cells maintain some modified characters, while others are partly lost. These findings suggest that DX exposure affects cell metabolism causing progressive changes of the cell morphotype. 相似文献
27.
Early in development the precursors of germ cells in Drosophila migrate at the posterior pole of the embryo and translocate to the bottom of the developing posterior midgut primordium. At the end of germ band elongation the pole cells cross the gut wall to enter in association with the gonadal mesoderm. We used laser scanning confocal microscopy on whole-mount Rh-phalloidin-stained embryos and transmission electron microscopy to investigate how pole cells cross the epithelial wall of the posterior midgut primordium. Our results suggest that pole cells leave the midgut sac by traveling through the intercellular spaces of the epithelium. During this process the epithelial cells at the bottom of the posterior midgut primordium are greatly deformed, but their junctional complexes do not completely release, avoiding breaks in the epithelial wall. 相似文献
28.
E. Baldini Osvaldo Facini Fabrizio Nerozzi Federica Rossi Annalisa Rotondi 《Trees - Structure and Function》1997,12(2):73-81
Light partition has been examined and evaluated on five woody species (Olea europaea, Ficus carica, Pittosporum tobira, Hedera helix maculata, Persica vulgaris) in relation to their leaf morpho-histological characteristics, water and chlorophyll contents. Leaf parameters and optical
properties (reflectance, transmittance, absorbance) in PAR, FR and NIR wavebands (400–1100 nm) were preliminarily submitted
to a canonical correlation analysis where lamina thickness and water content showed a leading role in determining all the
optical properties, while chlorophyll, influential in the PAR region, was remarkably effective only in an extreme pigment
situation when green and albino patches of ivy leaves were compared. Transmittance appeared inversely related to lamina thickness
in accordance with the Lambert Beer law. Significant correlations were found also between mesophyll water content and both
transmittance (positive) and reflectance (negative). Olive leaves showed peculiar optical patterns because of the dense and
continuous trichome layer on their abaxial surface.
Received: 3 January 1997 / Accepted: 5 May 1997 相似文献
29.
Annalisa Botta Elizabeth A. Lindsay Vesna Jurecic Antonio Baldini 《Mammalian genome》1997,8(12):890-895
We have constructed a comparative map in mouse of the critical region of human 22q11 deleted in DiGeorge (DGS) and Velocardiofacial
(VCFS) syndromes. The map includes 11 genes potentially haploinsufficient in these deletion syndromes. We have localized all
the conserved genes to mouse Chromosome (Chr) 16, bands B1-B3. The determination of gene order shows the presence of two regions
(distal and proximal), containing two groups of conserved genes. The gene order in the two regions is not completely conserved;
only in the proximal group is the gene order identical to human. In the distal group the gene order is inverted. These two
regions are separated by a DNA segment containing at least one gene which, in the human DGS region, is the most proximal of
the known deleted genes. In addition, the gene order within the distal group of genes is inverted relative to the human gene
order. Furthermore, a clathrin heavy chain-like gene was not found in the mouse genome by DNA hybridization, indicating that
there is an inconsistent level of gene conservation in the region. These and other independent data obtained in our laboratory
clearly show a complex evolutionary history of the DGS-VCFS region. Our data provide a framework for the development of a
mouse model for the 22q11 deletion with chromosome engineering technologies.
Received: 8 July 1997 / Accepted 11 August 1997 相似文献
30.
The species composition of the damselfly assemblage and the life history patterns of two Coenagrionidae (Ischnura elegans
and Cercion lindeni) were investigated along the urban tract of a river characterized by increasing organic pollution. The
assemblage was dominated by generalist species, usually recorded in lentic habitats, rather than by typical riverine species
and the proportion of the latter decrease at the most polluted sites. At the end of Winter, the mean size and in star distribution
were different between the sampling sites showing that the life history of both species examined were influenced by a degradation
of the environmental quality. A longer reproductive period, absence of diapause, and tolerance of low oxygen concentration
appear to be key factors that allow generalist species I. elegans and C. lindeni to predominate at the polluted sites.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献