全文获取类型
收费全文 | 61128篇 |
免费 | 3908篇 |
国内免费 | 6篇 |
专业分类
65042篇 |
出版年
2023年 | 447篇 |
2022年 | 377篇 |
2021年 | 812篇 |
2020年 | 754篇 |
2019年 | 740篇 |
2018年 | 1932篇 |
2017年 | 1802篇 |
2016年 | 2348篇 |
2015年 | 3078篇 |
2014年 | 3029篇 |
2013年 | 4075篇 |
2012年 | 4900篇 |
2011年 | 4356篇 |
2010年 | 2718篇 |
2009年 | 2063篇 |
2008年 | 3395篇 |
2007年 | 3193篇 |
2006年 | 3000篇 |
2005年 | 2559篇 |
2004年 | 2485篇 |
2003年 | 2217篇 |
2002年 | 2043篇 |
2001年 | 1374篇 |
2000年 | 1366篇 |
1999年 | 1045篇 |
1998年 | 432篇 |
1997年 | 314篇 |
1996年 | 320篇 |
1995年 | 304篇 |
1994年 | 236篇 |
1993年 | 219篇 |
1992年 | 524篇 |
1991年 | 444篇 |
1990年 | 398篇 |
1989年 | 396篇 |
1988年 | 392篇 |
1987年 | 349篇 |
1986年 | 332篇 |
1985年 | 334篇 |
1984年 | 337篇 |
1983年 | 230篇 |
1982年 | 211篇 |
1980年 | 170篇 |
1979年 | 207篇 |
1978年 | 202篇 |
1975年 | 194篇 |
1974年 | 211篇 |
1973年 | 220篇 |
1972年 | 181篇 |
1969年 | 170篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Carlos Inocencio Cortés-Martínez Norberto Chavarría-Hernández 《Biotechnology and bioengineering》2020,117(12):3968-3985
Monoxenic liquid culture is the most suitable technology for scaling up to industrial production of entomopathogenic nematodes (EPNs); however, the variability of the yield production remains a current problem in the process. The aim of this study was to analyze the parameters and criteria for EPN production in liquid culture based on scientific and technological knowledge from the last two decades. While experimental research has permitted the yield production of Heterorhabditis bacteriophora (362 × 103 infective juveniles [IJs]/ml) and Steinernema carpocapsae (252 × 103 IJs/ml), simultaneously, theoretical approaches have contributed to the understanding of the culture process, based on biological parameters of the bacterium–nematode complex and hydrodynamic and rheological parameters of the complex gas–liquid–solid system. Under this interdisciplinary research approach, bioprocess and biosystem engineering can contribute to design the various control strategies of the process variables, increase the productivity, and reduce the variability that until now distinguishes the in vitro production of EPNs by the liquid culture. 相似文献
112.
113.
114.
115.
Laura Miralles Santiago Lens Antonio Rodríguez-Folgar Manuel Carrillo Vidal Martín Bjarni Mikkelsen Eva Garcia-Vazquez 《PloS one》2013,8(8)
Visual species identification of cetacean strandings is difficult, especially when dead specimens are degraded and/or species are morphologically similar. The two recognised pilot whale species (Globicephala melas and Globicephala macrorhynchus) are sympatric in the North Atlantic Ocean. These species are very similar in external appearance and their morphometric characteristics partially overlap; thus visual identification is not always reliable. Genetic species identification ensures correct identification of specimens. Here we have employed one mitochondrial (D-Loop region) and eight nuclear loci (microsatellites) as genetic markers to identify six stranded pilot whales found in Galicia (Northwest Spain), one of them of ambiguous phenotype. DNA analyses yielded positive amplification of all loci and enabled species identification. Nuclear microsatellite DNA genotypes revealed mixed ancestry for one individual, identified as a post-F1 interspecific hybrid employing two different Bayesian methods. From the mitochondrial sequence the maternal species was Globicephala melas. This is the first hybrid documented between Globicephala melas and G. macrorhynchus, and the first post-F1 hybrid genetically identified between cetaceans, revealing interspecific genetic introgression in marine mammals. We propose to add nuclear loci to genetic databases for cetacean species identification in order to detect hybrid individuals. 相似文献
116.
117.
María Prados-Privado Juan Carlos Prados-Frutos José Luis Calvo-Guirado José Antonio Bea 《Computer methods in biomechanics and biomedical engineering》2016,19(15):1583-1591
To measure fatigue in dental implants and in its components, it is necessary to use a probabilistic analysis since the randomness in the output depends on a number of parameters (such as fatigue properties of titanium and applied loads, unknown beforehand as they depend on mastication habits). The purpose is to apply a probabilistic approximation in order to predict fatigue life, taking into account the randomness of variables. More accuracy on the results has been obtained by taking into account different load blocks with different amplitudes, as happens with bite forces during the day and allowing us to know how effects have different type of bruxism on the piece analysed. 相似文献
118.
Martha L. Bohórquez Alonso Jorge Martínez Cotrina David Aguilar Pardo Enrique Font Miguel Molina-Borja 《Journal of Ethology》2010,28(2):305-311
Many vertebrate species show display behaviors when predators are in their vicinity. Some of these displays may inform the
predator of the improbability of capturing the prey (i.e., pursuit-deterrent displays) and are potentially advantageous to
both predator and prey. Here we present data on a tail display performed by Gonatodes albogularis, a diurnal tropical gecko. We performed transect surveys in three habitats near Bogotá in Colombia. Geckos detected during
transects were approached by the observer in a standardized way, and details of their tail-waving displays were recorded.
In control recordings animals were watched from a distant site without approaching them. Results showed sexual differences
in tail-waving display: when approached by the observer, males performed this behavior more frequently than females. We found
no significant differences between males and females in flight-initiation distances and height above the substratum when they
were initially located. Results also showed that males displayed more frequently when approached than when the simulated predator
remained stationary. We interpret these results as evidence that the display functions as a pursuit-deterrent signal to potential
predators. However, as some tail displays were performed in the presence of conspecifics, the display may also have a social
function. 相似文献
119.
The recovery of Lactobacillus bulgaricus was studied in correlation to the kinetics of cell drying. When bacteria were dehydrated at 30 °C, either in the presence
or the absence of sucrose, the drying kinetics corresponds to a Fickean diffusion in correspondence with a short lag time.
In contrast, when the bacteria were dehydrated at 70 °C in the absence of sugar, the kinetics corresponds to an anomalous
diffusion, and the lag time is four to five times higher than that at 30 °C. However, when drying at 70 °C was carried out
in the presence of sucrose, drying kinetics turned into a Fickean process parallel to a substantial decrease in the lag time.
The pattern of water desorption was correlated with the critical water activity. When the drying kinetics corresponds to a
Fickean diffusion, the lag time started to increase at 0.7 water activity, but when the cells were dried at 70 °C, the damage
started at 0.5 water activity. This observation indicates that the drying rate affects the pattern of water desorption, and
it can change the value of critical water activity. These results put into relevance that the cell recovery is due to the
drying history and that the recovery increase produced by sucrose can be related to the maintenance of kinetic barriers for
water desorption. 相似文献
120.