全文获取类型
收费全文 | 12565篇 |
免费 | 863篇 |
国内免费 | 5篇 |
专业分类
13433篇 |
出版年
2023年 | 81篇 |
2022年 | 93篇 |
2021年 | 205篇 |
2020年 | 153篇 |
2019年 | 172篇 |
2018年 | 290篇 |
2017年 | 248篇 |
2016年 | 355篇 |
2015年 | 599篇 |
2014年 | 631篇 |
2013年 | 842篇 |
2012年 | 957篇 |
2011年 | 934篇 |
2010年 | 565篇 |
2009年 | 480篇 |
2008年 | 750篇 |
2007年 | 730篇 |
2006年 | 650篇 |
2005年 | 638篇 |
2004年 | 612篇 |
2003年 | 561篇 |
2002年 | 486篇 |
2001年 | 234篇 |
2000年 | 173篇 |
1999年 | 166篇 |
1998年 | 102篇 |
1997年 | 85篇 |
1996年 | 69篇 |
1995年 | 74篇 |
1994年 | 59篇 |
1993年 | 57篇 |
1992年 | 92篇 |
1991年 | 74篇 |
1990年 | 77篇 |
1989年 | 65篇 |
1988年 | 60篇 |
1987年 | 55篇 |
1986年 | 51篇 |
1985年 | 65篇 |
1984年 | 58篇 |
1983年 | 44篇 |
1982年 | 48篇 |
1981年 | 57篇 |
1980年 | 38篇 |
1979年 | 63篇 |
1978年 | 65篇 |
1976年 | 40篇 |
1975年 | 36篇 |
1974年 | 49篇 |
1971年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
We herein report the joint occurrence of an autistic disorder (AD) and X-linked hypophosphatemia. X-linked hypophosphatemia (XLH), an X-linked dominant disorder, is the most common of the inherited renal phosphate wasting disorders. Autism is a pervasive developmental disorder that occurs mainly due to genetic causes. In approximately 6-15% of cases, the autistic phenotype is a part of a broader genetic condition called syndromic autism.Therefore, reports of cases with the joint occurrence of a known genetic syndrome and a diagnosis of ASD by a child psychiatrist are relevant. A joint occurrence does not, however, mean that there is always a causal link between the genetic syndrome and the autistic behavioural phenotype. In this case, there are a number of arguments countering a causal link. 相似文献
52.
Summary A protocol was developed for the preparation of Cucumis sativus var Straight 8 protoplasts that incorporates a two-step Ficoll® gradient and results in a high percentage of viable, debris-free protoplasts suitable for the transient expression of foreign genes. Polyethylene glycol and electroporation were compared for their effect on protoplast transfection with commonly used reporter genes. Using a polyethylene glycol method, cucumber protoplasts transfected with a plasmid containing the -glucuronidase gene showed high expression levels, while protoplasts transfected with a plasmid containing the chloramphenicol acetyl transferase gene showed levels of activity that were barely distinguishable from mock-transfected controls. Tomato ringspot virus genomic RNA was also transfected into the protoplasts, and the assembly of viral particles was confirmed. 相似文献
53.
54.
Célia Bordier Claire Saraux Vincent A. Viblanc Hélène Gachot-Neveu Magali Beaugey Yvon Le Maho Céline Le Bohec 《PloS one》2014,9(12)
As the number of breeding pairs depends on the adult sex ratio in a monogamous species with biparental care, investigating sex-ratio variability in natural populations is essential to understand population dynamics. Using 10 years of data (2000–2009) in a seasonally monogamous seabird, the king penguin (Aptenodytes patagonicus), we investigated the annual sex ratio at fledging, and the potential environmental causes for its variation. Over more than 4000 birds, the annual sex ratio at fledging was highly variable (ranging from 44.4% to 58.3% of males), and on average slightly biased towards males (51.6%). Yearly variation in sex-ratio bias was neither related to density within the colony, nor to global or local oceanographic conditions known to affect both the productivity and accessibility of penguin foraging areas. However, rising sea surface temperature coincided with an increase in fledging sex-ratio variability. Fledging sex ratio was also correlated with difference in body condition between male and female fledglings. When more males were produced in a given year, their body condition was higher (and reciprocally), suggesting that parents might adopt a sex-biased allocation strategy depending on yearly environmental conditions and/or that the effect of environmental parameters on chick condition and survival may be sex-dependent. The initial bias in sex ratio observed at the juvenile stage tended to return to 1∶1 equilibrium upon first breeding attempts, as would be expected from Fisher’s classic theory of offspring sex-ratio variation. 相似文献
55.
56.
Summary A new form of ectodermal dysplasia was observed in two siblings, offspring of healthy non-consanguineous parents. The main findings in both children are: hypodontia, abnormally shaped teeth, scalp hypotrichosis, pili annulati, follicular hyperkeratosis on the trunk and limbs, intensified delineation and reticular hyperpigmentation of the nape, and hyperopia; one of the siblings also has astigmatism. As both patients have normal nails and are euhidrotic, this is an ectodermal dysplasia of the pilodental subgroup. The cause is probably genetic and autosomal-recessive inheritance is most likely. 相似文献
57.
Chern-En Chiang Lisa Naditch-Br?lé Sandrine Brette José Silva-Cardoso Habib Gamra Jan Murin Oleg J. Zharinov Philippe Gabriel Steg 《PloS one》2016,11(1)
Background
Atrial fibrillation (AF) can be managed with rhythm- or rate-control strategies. There are few data from routine clinical practice on the frequency with which each strategy is used and their correlates in terms of patients’ clinical characteristics, AF control, and symptom burden.Methods
RealiseAF was an international, cross-sectional, observational survey of 11,198 patients with AF. The aim of this analysis was to describe patient profiles and symptoms according to the AF management strategy used. A multivariate logistic regression identified factors associated with AF management strategy at the end of the visit.Results
Among 10,497 eligible patients, 53.7% used a rate-control strategy, compared with 34.5% who used a rhythm-control strategy. In 11.8% of patients, no clear strategy was stated. The proportion of patients with AF-related symptoms (EHRA Class > = II) was 78.1% (n = 4396/5630) for those using a rate-control strategy vs. 67.8% for those using a rhythm-control strategy (p<0.001). Multivariate logistic regression analysis revealed that age <75 years or the paroxysmal or persistent form of AF favored the choice of a rhythm-control strategy. A change in strategy was infrequent, even in patients with European Heart Rhythm Association (EHRA) Class > = II.Conclusions
In the RealiseAF routine clinical practice survey, rate control was more commonly used than rhythm control, and a change in strategy was uncommon, even in symptomatic patients. In almost 12% of patients, no clear strategy was stated. Physician awareness regarding optimal management strategies for AF may be improved. 相似文献58.
Allometric and nonallometric components of Drosophila wing shape respond differently to developmental temperature 总被引:2,自引:0,他引:2
Debat V Bégin M Legout H David JR 《Evolution; international journal of organic evolution》2003,57(12):2773-2784
Phenotypic plasticity of wing size and shape of Drosophila simulans was analyzed across the entire range of viable developmental temperatures with Procrustes geometric morphometric method. In agreement with previous studies, size clearly decreases when temperature increases. Wing shape variation was decomposed into its allometric (24%) and nonallometric (76%) components, and both were shown to involve landmarks located throughout the entire wing blade. The allometric component basically revealed a progressive, monotonous variation along the temperature. Surprisingly, nonallometric shape changes were highly similar at both extremes of the thermal range, suggesting that stress, rather than temperature per se, is the key developmental factor affecting wing shape. 相似文献
59.
Matthieu Amor Mickaël Tharaud Alexandre Gélabert Arash Komeili 《Environmental microbiology》2020,22(3):823-831
Magnetotactic bacteria (MTB) are ubiquitous aquatic microorganisms that mineralize dissolved iron into intracellular magnetic crystals. After cell death, these crystals are trapped into sediments that remove iron from the soluble pool. MTB may significantly impact the iron biogeochemical cycle, especially in the ocean where dissolved iron limits nitrogen fixation and primary productivity. A thorough assessment of their impact has been hampered by a lack of methodology to measure the amount of, and variability in, their intracellular iron content. We quantified the iron mass contained in single MTB cells of Magnetospirillum magneticum strain AMB-1 using a time-resolved inductively coupled plasma-mass spectrometry methodology. Bacterial iron content depends on the external iron concentration, and reaches a maximum value of ~10−6 ng of iron per cell. From these results, we calculated the flux of dissolved iron incorporation into environmental MTB populations and conclude that MTB may mineralize a significant fraction of dissolved iron into crystals. 相似文献
60.