全文获取类型
收费全文 | 674580篇 |
免费 | 81794篇 |
国内免费 | 312篇 |
专业分类
756686篇 |
出版年
2018年 | 5795篇 |
2016年 | 7687篇 |
2015年 | 10828篇 |
2014年 | 12604篇 |
2013年 | 18257篇 |
2012年 | 20271篇 |
2011年 | 20656篇 |
2010年 | 13963篇 |
2009年 | 12724篇 |
2008年 | 18173篇 |
2007年 | 18931篇 |
2006年 | 17601篇 |
2005年 | 17057篇 |
2004年 | 16770篇 |
2003年 | 16528篇 |
2002年 | 16069篇 |
2001年 | 30122篇 |
2000年 | 30343篇 |
1999年 | 24199篇 |
1998年 | 8700篇 |
1997年 | 9234篇 |
1996年 | 8761篇 |
1995年 | 8315篇 |
1994年 | 8204篇 |
1993年 | 8286篇 |
1992年 | 20730篇 |
1991年 | 20232篇 |
1990年 | 19648篇 |
1989年 | 19197篇 |
1988年 | 17726篇 |
1987年 | 17125篇 |
1986年 | 15784篇 |
1985年 | 15899篇 |
1984年 | 13256篇 |
1983年 | 11563篇 |
1982年 | 8959篇 |
1981年 | 7995篇 |
1980年 | 7697篇 |
1979年 | 12912篇 |
1978年 | 10112篇 |
1977年 | 9295篇 |
1976年 | 8692篇 |
1975年 | 9508篇 |
1974年 | 10101篇 |
1973年 | 10110篇 |
1972年 | 9193篇 |
1971年 | 8531篇 |
1970年 | 7170篇 |
1969年 | 6951篇 |
1968年 | 6235篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
A search for differences due to ANS staining (hydrophobia), Con A and PNA binding capacity, and birefringence was carried out on stratified epithelia of rat skin and human breast cells (HBC) in culture. Microfluorimetric measurements confirm that the ANS fluorescence of the stratum corneum from adults is higher than that of newborns. HBC exhibited an unexpected deep ANS-fluorescence. Differences in the binding capacity of the epithelial layers to Con A and PNA were detected with advancing age. Retardation measurements revealed that the form birefringence of the stratum corneum is higher in adult animals specially as revealed by the fact that its form birefringence curve branch from n = 1.414 to n = 1.479 is steeper, i.e. depict higher values. The strong birefringence of the cytoplasmic tonofilaments presented by cultured human breast cells was considered an unexpected finding and attributed to changes that the cells underwent following the in vitro conditions. 相似文献
952.
N Iu Belenkov E B Korolev M O Gromyko 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1985,35(4):674-677
Reactivity of neurones in orbitofrontal cortex of the cat to the action of light or sound was studied in consecutive stages of alimentary behaviour conditioned by the smell and then the sight of food. Changes were found of the character of neuronal reactions to the light and sound stimuli at the change of smell to the sight of food. A conclusion is drown, that polysensory properties of the neurones of the orbitofrontal cortex provide integral organization of brain sensory function at separate stages of alimentary behaviour. 相似文献
953.
954.
955.
Michelle van der Bank F. H. van der Bank B. -E. van Wyk 《Plant Systematics and Evolution》1999,219(1-2):27-38
We have tested the hypothesis that reseeding is a plesiomorphic character state and that sprouting is a derived state inAspalathus linearis, and that the latter is an adaptation to ensure fire-survival in a fireprone environment. Samples of five seeder and four sprouter populations of A.linearis were examined by horizontal starch gel electrophoresis to assess the amount of genetic differentiation within and between sprouting and seeding populations, and to determine the extent of gene flow between the populations. Leaf extracts were surveyed for ten enzymes and gene products revealed genetic variation at 13 (76%) of 17 protein coding loci. Allele frequency differences were found between sprouting and seeding populations and genetic distance values show that the sprouters are grouped separate from the seeders, thus providing support for the morphological data on which the above mentioned hypothesis is based. It is evident that evolution operates at the population level inA. linearis. 相似文献
956.
957.
958.
959.
Marta Tejera-Alhambra Armanda Casrouge Clara de Andrés Ansgar Seyfferth Rocío Ramos-Medina Bárbara Alonso Janet Vega Lidia Fernández-Paredes Matthew L. Albert Silvia Sánchez-Ramón 《PloS one》2015,10(6)
Multiple sclerosis, the most common cause of neurological disability in young population after trauma, represents a significant public health burden. Current challenges associated with management of multiple sclerosis (MS) patients stem from the lack of biomarkers that might enable stratification of the different clinical forms of MS and thus prompt treatment for those patients with progressive MS, for whom there is currently no therapy available. In the present work we analyzed a set of thirty different plasma cytokines, chemokines and growth factors present in circulation of 129 MS patients with different clinical forms (relapsing remitting, secondary progressive and primary progressive MS) and 53 healthy controls, across two independent cohorts. The set of plasma analytes was quantified with Luminex xMAP technology and their predictive power regarding clinical outcome was evaluated both individually using ROC curves and in combination using logistic regression analysis. Our results from two independent cohorts of MS patients demonstrate that the divergent clinical and histology-based MS forms are associated with distinct profiles of circulating plasma protein biomarkers, with distinct signatures being composed of chemokines and growth/angiogenic factors. With this work, we propose that an evaluation of a set of 4 circulating biomarkers (HGF, Eotaxin/CCL11, EGF and MIP-1β/CCL4) in MS patients might serve as an effective tool in the diagnosis and more personalized therapeutic targeting of MS patients. 相似文献
960.
Mutagenesis of hydroxylamine oxidoreductase in Nitrosomonas europaea by transformation and recombination. 总被引:2,自引:0,他引:2 下载免费PDF全文
Mutagenesis of Nitrosomonas europaea was achieved by electroporation and recombination. To demonstrate this, an aminoglycoside 3'-phosphotransferase (kan) gene was specifically inserted into each of the three gene copies of hao individually. Southern hybridizations and PCR analysis showed the incorporation of the kan gene at the chosen genetic loci. The isolation of mutant strains was achieved in 7 to 14 days when the strains were grown on solid medium. The induced mutations were stable even in the absence of kanamycin-selective pressure for periods of up to 45 days in culture. The mutant strains did not show an observable phenotype different from that of the wild type when grown under the same conditions. 相似文献