全文获取类型
收费全文 | 6772篇 |
免费 | 525篇 |
国内免费 | 1篇 |
专业分类
7298篇 |
出版年
2023年 | 56篇 |
2022年 | 107篇 |
2021年 | 224篇 |
2020年 | 148篇 |
2019年 | 177篇 |
2018年 | 245篇 |
2017年 | 209篇 |
2016年 | 305篇 |
2015年 | 374篇 |
2014年 | 457篇 |
2013年 | 489篇 |
2012年 | 544篇 |
2011年 | 495篇 |
2010年 | 282篇 |
2009年 | 264篇 |
2008年 | 333篇 |
2007年 | 290篇 |
2006年 | 232篇 |
2005年 | 227篇 |
2004年 | 194篇 |
2003年 | 159篇 |
2002年 | 158篇 |
2001年 | 127篇 |
2000年 | 106篇 |
1999年 | 97篇 |
1998年 | 46篇 |
1997年 | 45篇 |
1996年 | 38篇 |
1995年 | 32篇 |
1994年 | 36篇 |
1993年 | 28篇 |
1992年 | 56篇 |
1991年 | 65篇 |
1990年 | 51篇 |
1989年 | 41篇 |
1988年 | 39篇 |
1987年 | 41篇 |
1986年 | 57篇 |
1985年 | 36篇 |
1984年 | 35篇 |
1983年 | 30篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 20篇 |
1978年 | 28篇 |
1977年 | 27篇 |
1976年 | 17篇 |
1975年 | 30篇 |
1974年 | 20篇 |
排序方式: 共有7298条查询结果,搜索用时 0 毫秒
151.
Summary Large numbers of nuclear inclusions have been found in the nerve cells of the sphenopalatine ganglia of six healthy adult dogs. Their morphological characteristics are similar to those previously described elsewhere. The presence of simple and granular bodies in normal cells seems to support the hypothesis that these nuclear structures might be considered as normal nuclear organelles related to cellular metabolic activity. 相似文献
152.
Summary The presence of aromatic 1-amino acid decarboxylase (AADC) in nerve cell bodies of the intrinsic plexuses of the guinea-pig small intestine was demonstrated by incubating segments of intestine with 1-dopa in the presence of an inhibitor of monoamine oxidase, pargyline. After such incubation, some nerve cell bodies gave a fluorescence histochemical reaction indicative of the presence of a decarboxylated product of 1-dopa, probably dopamine. No fluorescence reaction occurred in the unincubated control or if the inhibitor of AADC, RO 4-4602, was included in the incubation mixture. The AADC-containing cell bodies apparently do not take up and store dopamine, because no fluorescence could be detected after incubation with dopamine and a monoamine oxidase inhibitor. The AADC-containing cells were found in about half of the ganglia of the submucous plexus of the guinea-pig small intestine, but were considerably less frequent in the myenteric plexus. They were also found in the other areas examined in this study, that is, in both enteric plexuses of the guinea-pig distal colon and of the small intestines of rabbits and rats. 相似文献
153.
The induction of − “petite” mutants by guanidine hydrochloride (GuHCl) is inhibited in several conditions. Anaerobiosis inhibited the induction either with or without cell multiplication. Both nalidixic acid (NA) and cycloheximide (CH) inhibited the induction of mutants. On the other hand, chloramphenicol (CAP) produced a dual effect: at low concentration it stimulated, at high concentration it inhibited, the induction. The effect of these different inhibitors on the transformation of + mother cells into − by GuHCl is discussed. 相似文献
154.
155.
1. The enzymic utilization of O-acetyl-l-carnitine other than via carnitine acetyltransferase (EC 2.3.1.7) was investigated in liver homogenates from rats, sheep and dry cows. 2. An enzymic utilization of O-acetyl-l-carnitine via hydrolysis of the ester bond to yield stoicheiometric quantities of acetate and l-carnitine was demonstrated; 0.55, 0.53 and 0.30mumol of acetyl-l-carnitine were utilized/min per g fresh wt. of liver homogenates from rats, sheep and dry cows respectively. 3. The acetylcarnitine hydrolysis activity was not due to a non-specific esterase or non-specific cholinesterase. O-Acetyl-d-carnitine was not utilized. 4. The activity was associated with the enriched outer mitochondrial membrane fraction from rat liver. Isolation of this fraction resulted in an eightfold purification of acetylcarnitine hydrolase activity. 4. The K(m) for this acetylcarnitine utilization was 2mm and 1.5mm for rat and sheep liver homogenates respectively. 6. There was a significant increase in acetylcarnitine hydrolase in rats on starvation and cows on lactation and a significant decrease in sheep that were severely alloxan-diabetic. 7. The physiological role of an acetylcarnitine hydrolase is discussed in relation to coupling with carnitine acetyltransferase for the relief of ;acetyl pressure'. 相似文献
156.
157.
Hadi Shahrabadi Amir Hossein Haghighi Roya Askari Majid Asadi-Shekaari Daniel Costa Souza Paulo Gentil 《Current issues in molecular biology》2022,44(7):3030
Chronic methamphetamine use increases apoptosis, leading to heart failure and sudden cardiac death. Previous studies have shown the importance of high-intensity interval training (HIIT) in reducing indices of cardiac tissue apoptosis in different patients, but in the field of sports science, the molecular mechanisms of apoptosis in methamphetamine-dependent rats are still unclear. The present article aimed to investigate the changes in cardiac apoptosis markers in methamphetamine-dependent rats in response to HIIT. Left ventricular tissue was used to evaluate caspase-3, melusin, FAK, and IQGAP1 gene expression. Rats were divided into four groups: sham, methamphetamine (METH), METH-control, and METH-HIIT. METH was injected for 21 days and then the METH-HIIT group performed HIIT for 8 weeks at 5 sessions per week. The METH groups showed increased caspase-3 gene expression and decreased melusin, FAK, and IQGAP1 when compared to the sham group. METH-HIIT showed decreased caspase-3 and increased melusin and FAK gene expression compared with the METH and METH-control groups. The IQGAP1 gene was higher in METH-HIIT when compared with METH, while no difference was observed between METH-HIIT and METH-control. Twenty-one days of METH exposure increased apoptosis markers in rat cardiac tissue; however, HIIT might have a protective effect, as shown by the apoptosis markers. 相似文献
158.
Charlotte Repton C. Fiona Cullen Mariana F. A. Costa Christos Spanos Juri Rappsilber Hiroyuki Ohkura 《PLoS genetics》2022,18(6)
Global regulation of spindle-associated proteins is crucial in oocytes due to the absence of centrosomes and their very large cytoplasmic volume, but little is known about how this is achieved beyond involvement of the Ran-importin pathway. We previously uncovered a novel regulatory mechanism in Drosophila oocytes, in which the phospho-docking protein 14-3-3 suppresses microtubule binding of Kinesin-14/Ncd away from chromosomes. Here we report systematic identification of microtubule-associated proteins regulated by 14-3-3 from Drosophila oocytes. Proteins from ovary extract were co-sedimented with microtubules in the presence or absence of a 14-3-3 inhibitor. Through quantitative mass-spectrometry, we identified proteins or complexes whose ability to bind microtubules is suppressed by 14-3-3, including the chromosomal passenger complex (CPC), the centralspindlin complex and Kinesin-14/Ncd. We showed that 14-3-3 binds to the disordered region of Borealin, and this binding is regulated differentially by two phosphorylations on Borealin. Mutations at these two phospho-sites compromised normal Borealin localisation and centromere bi-orientation in oocytes, showing that phospho-regulation of 14-3-3 binding is important for Borealin localisation and function. 相似文献
159.
Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient
下载免费PDF全文
![点击此处可从《Ecology letters》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nikolaos M. Fyllas Lisa Patrick Bentley Alexander Shenkin Gregory P. Asner Owen K. Atkin Sandra Díaz Brian J. Enquist William Farfan‐Rios Emanuel Gloor Rossella Guerrieri Walter Huaraca Huasco Yoko Ishida Roberta E. Martin Patrick Meir Oliver Phillips Norma Salinas Miles Silman Lasantha K Weerasinghe Joana Zaragoza‐Castells Yadvinder Malhi 《Ecology letters》2017,20(6):730-740
One of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait‐spectra and individual‐based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon‐Andes. The model accurately predicted the magnitude and trends in forest productivity with elevation, with solar radiation and plant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, and wood density) collectively accounting for productivity variation. Remarkably, explicit representation of temperature variation with elevation was not required to achieve accurate predictions of forest productivity, as trait variation driven by species turnover appears to capture the effect of temperature. Our semi‐mechanistic model suggests that spatial variation in traits can potentially be used to estimate spatial variation in productivity at the landscape scale. 相似文献
160.
Michael Abberton Jacqueline Batley Alison Bentley John Bryant Hongwei Cai James Cockram Antonio Costa de Oliveira Leland J. Cseke Hannes Dempewolf Ciro De Pace David Edwards Paul Gepts Andy Greenland Anthony E. Hall Robert Henry Kiyosumi Hori Glenn Thomas Howe Stephen Hughes Mike Humphreys David Lightfoot Athole Marshall Sean Mayes Henry T. Nguyen Francis C. Ogbonnaya Rodomiro Ortiz Andrew H. Paterson Roberto Tuberosa Babu Valliyodan Rajeev K. Varshney Masahiro Yano 《Plant biotechnology journal》2016,14(4):1095-1098
Agriculture is now facing the ‘perfect storm’ of climate change, increasing costs of fertilizer and rising food demands from a larger and wealthier human population. These factors point to a global food deficit unless the efficiency and resilience of crop production is increased. The intensification of agriculture has focused on improving production under optimized conditions, with significant agronomic inputs. Furthermore, the intensive cultivation of a limited number of crops has drastically narrowed the number of plant species humans rely on. A new agricultural paradigm is required, reducing dependence on high inputs and increasing crop diversity, yield stability and environmental resilience. Genomics offers unprecedented opportunities to increase crop yield, quality and stability of production through advanced breeding strategies, enhancing the resilience of major crops to climate variability, and increasing the productivity and range of minor crops to diversify the food supply. Here we review the state of the art of genomic‐assisted breeding for the most important staples that feed the world, and how to use and adapt such genomic tools to accelerate development of both major and minor crops with desired traits that enhance adaptation to, or mitigate the effects of climate change. 相似文献