全文获取类型
收费全文 | 7453篇 |
免费 | 613篇 |
国内免费 | 2篇 |
出版年
2022年 | 35篇 |
2021年 | 95篇 |
2020年 | 76篇 |
2019年 | 76篇 |
2018年 | 115篇 |
2017年 | 90篇 |
2016年 | 144篇 |
2015年 | 243篇 |
2014年 | 276篇 |
2013年 | 409篇 |
2012年 | 440篇 |
2011年 | 437篇 |
2010年 | 313篇 |
2009年 | 250篇 |
2008年 | 366篇 |
2007年 | 366篇 |
2006年 | 367篇 |
2005年 | 333篇 |
2004年 | 304篇 |
2003年 | 369篇 |
2002年 | 333篇 |
2001年 | 105篇 |
2000年 | 85篇 |
1999年 | 128篇 |
1998年 | 121篇 |
1997年 | 73篇 |
1996年 | 90篇 |
1995年 | 93篇 |
1994年 | 81篇 |
1993年 | 92篇 |
1992年 | 93篇 |
1991年 | 65篇 |
1990年 | 77篇 |
1989年 | 75篇 |
1988年 | 55篇 |
1987年 | 69篇 |
1986年 | 50篇 |
1985年 | 75篇 |
1984年 | 84篇 |
1983年 | 52篇 |
1982年 | 84篇 |
1981年 | 55篇 |
1980年 | 81篇 |
1979年 | 65篇 |
1978年 | 50篇 |
1977年 | 49篇 |
1976年 | 46篇 |
1975年 | 40篇 |
1974年 | 44篇 |
1973年 | 40篇 |
排序方式: 共有8068条查询结果,搜索用时 15 毫秒
11.
Nathalie Jeanray Rapha?l Marée Benoist Pruvot Olivier Stern Pierre Geurts Louis Wehenkel Marc Muller 《PloS one》2015,10(1)
Zebrafish is increasingly used to assess biological properties of chemical substances and thus is becoming a specific tool for toxicological and pharmacological studies. The effects of chemical substances on embryo survival and development are generally evaluated manually through microscopic observation by an expert and documented by several typical photographs. Here, we present a methodology to automatically classify brightfield images of wildtype zebrafish embryos according to their defects by using an image analysis approach based on supervised machine learning. We show that, compared to manual classification, automatic classification results in 90 to 100% agreement with consensus voting of biological experts in nine out of eleven considered defects in 3 days old zebrafish larvae. Automation of the analysis and classification of zebrafish embryo pictures reduces the workload and time required for the biological expert and increases the reproducibility and objectivity of this classification. 相似文献
12.
13.
We isolated a Zea mays cDNA encoding the 40S subunit cytoplasmic ribosomal protein S11. The nucleotide sequence was determined and the derived amino acid sequence compared to the corresponding Arabidopsis thaliana protein showing an homology of 90%. This ribosomal protein is encoded by a small multigene family of at least two members. The mRNA steady-state level is about one order of magnitude higher in rapidly growing parts of the plant such as the roots and shoots of seedlings compared to fully expanded leaf tissue. 相似文献
14.
Adriana Calderaro Giovanna Piccolo Chiara Gorrini Sara Montecchini Sabina Rossi Maria Cristina Medici Carlo Chezzi Georges Snounou 《PloS one》2012,7(10)
It has been proposed that ovale malaria in humans is caused by two closely related but distinct species of malaria parasites: P. ovale curtisi and P. ovale wallikeri. We have extended and optimized a Real-time PCR assay targeting the parasite’s small subunit ribosomal RNA (ssrRNA) gene to detect both these species. When the assay was applied to 31 archival blood samples from patients diagnosed with P. ovale, it was found that the infection in 20 was due to P. ovale curtisi and in the remaining 11 to P. ovale wallikeri. Thus, this assay provides a useful tool that can be applied to epidemiological investigations of the two newly recognized distinct P. ovale species, that might reveal if these species also differ in their clinical manifestation, drugs susceptibility and relapse periodicity. The results presented confirm that P. ovale wallikeri is not confined to Southeast Asia, since the majority of the patients analyzed in this study had acquired their P. ovale infection in African countries, mostly situated in West Africa. 相似文献
15.
Louis C. Parkes 《BMJ (Clinical research ed.)》1899,2(2032):1648-1649
16.
17.
18.
The Spanish ``Asturiana' cattle breed is characterized by the segregation of a genetically determined muscular hypertrophy
referred to as double-muscling or ``culones'. We demonstrate by linkage analysis that this muscular hypertrophy involves
the mh locus previously shown to cause double-muscling in the Belgian Blue cattle breed, pointing towards locus homogeneity of this
trait across both breeds. Moreover, using a twopoint and multipoint maximum likelihood approach, we show that flanking microsatellite
markers are in linkage disequilibrium with the mh locus in both breeds albeit with different alleles. Finally, we discuss how allelic homogeneity across breeds might be exploited
to achieve efficient genetic fine-mapping of the mh locus.
Received: 13 September 1996 / Accepted: 20 January 1997 相似文献
19.
Michiel L. Houben Marloes J. M. Olde Nordkamp Peter G. J. Nikkels Cornelis K. van der Ent Linde Meyaard Louis Bont 《PloS one》2013,8(12)
The soluble form of the inhibitory immune receptor leukocyte-Associated Ig-like Receptor-1 (sLAIR-1) is present in plasma, urine and synovial fluid and correlates to inflammation. We and others previously showed inflammatory protein expression in normal amniotic fluid at term. We hypothesized that sLAIR-1 is present in amniotic fluid during term parturition and is related to fetal lung function development. sLAIR-1 was detectable in all amniotic fluid samples (n=355) collected during term spontaneous deliveries. First, potential intra-uterine origins of amniotic fluid sLAIR-1 were explored. Although LAIR-1 was expressed on the surface of amniotic fluid neutrophils, LAIR-1 was not secreted upon ex vivo neutrophil stimulation with LPS, or PMA/ionomycin. Cord blood concentrations of sLAIR-1 were fourfold lower than and not related to amniotic fluid concentrations and placentas showed no or only sporadic LAIR-1 positive cells. Similarly, in post-mortem lung tissue of term neonates that died of non-pulmonary disorders LAIR-1 positive cells were absent or only sporadically present. In fetal urine samples, however, sLAIR-1 levels were even higher than in amniotic fluid and correlated with amniotic fluid sLAIR-1 concentrations. Second, the potential relevance of amniotic fluid sLAIR-1 was studied. sLAIR-1 concentrations had low correlation to amniotic fluid cytokines. We measured neonatal lung function in a convenient subset of 152 infants, using the single occlusion technique, at a median age of 34 days (IQR 30-39). The amniotic fluid concentration of sLAIR-1 was independently correlated to airway compliance (ρ=0.29, P=.001). Taken together, we show the consistent presence of sLAIR-1 in amniotic fluid, which originates from fetal urine. Concentrations of sLAIR-1 in amniotic fluid during term deliveries are independent from levels of other soluble immune mediators. The positive association between concentrations of amniotic fluid sLAIR-1 and neonatal lung compliance suggests that amniotic fluid sLAIR-1 may be useful as a novel independent marker of neonatal lung maturation. 相似文献
20.