全文获取类型
收费全文 | 815篇 |
免费 | 56篇 |
国内免费 | 4篇 |
出版年
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 27篇 |
2015年 | 32篇 |
2014年 | 40篇 |
2013年 | 42篇 |
2012年 | 46篇 |
2011年 | 29篇 |
2010年 | 29篇 |
2009年 | 21篇 |
2008年 | 33篇 |
2007年 | 32篇 |
2006年 | 22篇 |
2005年 | 25篇 |
2004年 | 29篇 |
2003年 | 16篇 |
2002年 | 30篇 |
2001年 | 23篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 24篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1973年 | 3篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1950年 | 5篇 |
1928年 | 4篇 |
排序方式: 共有875条查询结果,搜索用时 500 毫秒
121.
122.
123.
J. Bonaventure C. Philippe G. Plessis J. Vigneron C. Lasselin P. Maroteaux S. Gilgenkrantz 《Human genetics》1992,90(1-2):164-168
Summary A three generation family with Stickler syndrome is reported. Affected patients exhibited myopia with frequent retinal detachment or glaucoma. Most of them had characteristic facial dysmorphism, the Pierre-Robin sequence being observed in four individuals. Neonatal radiological signs of the Weissenbacher-Zweymüller syndrome were also noticed but early arthopathy was not reported in adults. Restriction fragment length polymorphism studies with the type II collagen gene (COL2A1) showed a recombination event between the disease locus and COL2A1, thus excluding collagen type II as the candidate gene. Although the calculation of the likelihood of genetic heterogeneity versus homogeneity based on 10 families was not statistically significant, we suggest that a second locus is probably involved in this highly variable syndrome. 相似文献
124.
R. M. du Bois 《BMJ (Clinical research ed.)》1994,309(6948):175-179
125.
126.
Eapsa?Berry Shiva?K.?Sharma Maharaj?K.?Pandit R.?GeetaEmail author 《Plant Systematics and Evolution》2018,304(2):219-230
Floral symmetry and pigmentation are features of flowers that are believed to be associated due to their shared influence on pollinator behaviour. However, the evolution of such associations has so far not been examined. We analysed variation in Rhododendron flowers, in a phylogenetic context, to test whether the evolution of floral symmetry types and pigment patterns are correlated. Variation in floral symmetry due to variation in corolla form, stamen flexion, stamen arrangement, pistil flexion, as well as corolla pigment patterns was documented in 98 species of Rhododendron. Phylogenetic relations among these species were estimated using maximum likelihood (ML) and Bayesian methods, building on a published molecular dataset of sequences of RNA Polymerase II subunit (RPB2-I). Evolution of the floral traits was studied using phylogenetic correlation tests and ancestral state reconstructions (maximum parsimony, MP and ML methods). Significant correlations were found between corolla pigment pattern and type of floral symmetry at the level of corolla form, stamen flexion or arrangement, and pistil flexion. As expected from their similar roles in enhancing attractability to pollinator, monosymmetric corollas and presence of pigment pattern are correlated; in addition, monosymmetry involving other whorls too shows such a relationship with pigment patterns, and with each other. Multiple evolutionary shifts were detected between monosymmetry and polysymmetry of floral traits in Rhododendron. The relationship between floral monosymmetry attributes and presence of corolla pigment patterns, and additionally, frequent evolutionary shifts in these traits suggest pollinator-mediated selective pressures in Rhododendron. 相似文献
127.
L. Catoire I. Braccini N. Bouchemal-Chibani L. Jullien C. Herve du Penhoat S. Perez 《Glycoconjugate journal》1997,14(8):935-943
Over the past decade molecular mechanics and molecular dynamics studies have demonstrated considerable flexibility for carbohydrates.
In order to interpret the corresponding NMR parameters, which correspond to a time-averaged or 'virtual' conformer, it is
necessary to simulate the experimental data using the averaged geometrical representation obtained with molecular modelling
methods. This structural information can be transformed into theoretical NMR data using empirical Karplus-type equations for
the scalar coupling constants and the appropriate formalism for the relaxation parameters. In the case of relaxation data,
the 'model-free' spectral densities have been widely used in order to account for the internal motions in sugars. Several
studies have been conducted with truncated model-free spectral densities based on the assumption that internal motion is very
fast with respect to overall tumbling.
In this report we present experimental and theoretical evidence that suggests that this approach is not justified. Indeed,
recent results show that even in the case of moderate-sized carbohydrates internal motions are occurring on the same timescale
as molecular reorientation. Simulations of relaxation parameters (NOESY volumes, proton cross-relaxation rates, carbon T1
and nOe values) in the dispersion range (0.1<Tc<5 ns) show that rates of internal motion can be fairly precisely defined with
respect to overall tumbling. Experimental data for a variety of oligosaccharides clearly indicate similar timescales for internal
and overall motion.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
128.
Spectral karyotyping refines cytogenetic diagnostics of constitutional chromosomal abnormalities 总被引:12,自引:0,他引:12
E. Schröck T. Veldman Hesed Padilla-Nash Y. Ning Jack Spurbeck Syed Jalal Lisa G. Shaffer Peter Papenhausen Chahira Kozma Mary C. Phelan Eigil Kjeldsen Stephen A. Schonberg Patricia O’Brien Les Biesecker Stan du Manoir Thomas Ried 《Human genetics》1997,101(3):255-262
Karyotype analysis by chromosome banding is the standard method for identifying numerical and structural chromosomal aberrations
in pre- and postnatal cytogenetics laboratories. However, the chromosomal origins of markers, subtle translocations, or complex
chromosomal rearrangements are often difficult to identify with certainty. We have developed a novel karyotyping technique,
termed spectral karyotyping (SKY), which is based on the simultaneous hybridization of 24 chromosome-specific painting probes
labeled with different fluorochromes or fluorochrome combinations. The measurement of defined emission spectra by means of
interferometer-based spectral imaging allows for the definitive discernment of all human chromosomes in different colors.
Here, we report the comprehensive karyotype analysis of 16 samples from different cytogenetic laboratories by merging conventional
cytogenetic methodology and spectral karyotyping. This approach could become a powerful tool for the cytogeneticists, because
it results in a considerable improvement of karyotype analysis by identifying chromosomal aberrations not previously detected
by G-banding alone. Advantages, limitations, and future directions of spectral karyotyping are discussed.
Received: 4 August 1997 / Accepted: 8 September 1997 相似文献
129.
130.
A M Joubert A Panzer F Joubert M L Lottering P C Bianchi P J du Toit J C Seegers 《Prostaglandins, leukotrienes, and essential fatty acids》2001,65(3):173-177
The effects of 20 microg/ml exogenous arachidonic acid (AA) and prostaglandin A(2) (PGA(2)) were evaluated on total tyrosine kinase (TK) activity and tyrosine phosphorylation status in HeLa and MCF-7 cells. AA and PGA(2) increased TK activity in both HeLa and MCF-7 cells. Western blotting employing an anti-phosphotyrosine antibody showed only one protein of approximately 55 kDa (approximately 55 kDa) to be phosphorylated in the MCF-7 cells, while a variety of proteins were phosphorylated in the HeLa cells, including the approximately 55 kDa protein. Amino acid analyses as well as Matrix Assisted Laser Desorption Ionization were conducted on this protein from different cell lines and it was shown to be similar. Comparison to p53 did not show similarities. The identity of this protein needs to be further characterized to help elucidate the signal transduction pathways of AA and PGA(2). 相似文献