全文获取类型
收费全文 | 103046篇 |
免费 | 992篇 |
国内免费 | 812篇 |
出版年
2023年 | 80篇 |
2022年 | 162篇 |
2021年 | 308篇 |
2020年 | 212篇 |
2019年 | 258篇 |
2018年 | 12050篇 |
2017年 | 10875篇 |
2016年 | 7813篇 |
2015年 | 1178篇 |
2014年 | 827篇 |
2013年 | 930篇 |
2012年 | 4907篇 |
2011年 | 13400篇 |
2010年 | 12365篇 |
2009年 | 8553篇 |
2008年 | 10205篇 |
2007年 | 11754篇 |
2006年 | 657篇 |
2005年 | 820篇 |
2004年 | 1238篇 |
2003年 | 1293篇 |
2002年 | 1014篇 |
2001年 | 521篇 |
2000年 | 361篇 |
1999年 | 190篇 |
1998年 | 75篇 |
1997年 | 76篇 |
1996年 | 63篇 |
1995年 | 50篇 |
1993年 | 68篇 |
1992年 | 113篇 |
1991年 | 105篇 |
1990年 | 78篇 |
1989年 | 78篇 |
1988年 | 86篇 |
1987年 | 88篇 |
1986年 | 70篇 |
1985年 | 74篇 |
1984年 | 77篇 |
1983年 | 56篇 |
1982年 | 54篇 |
1979年 | 69篇 |
1977年 | 43篇 |
1976年 | 47篇 |
1975年 | 50篇 |
1974年 | 57篇 |
1972年 | 302篇 |
1971年 | 314篇 |
1970年 | 53篇 |
1969年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Syed Tabia Andrabi Bilqeesa Bhat Mahak Gupta Bijender Kumar Bajaj 《Probiotics and antimicrobial proteins》2016,8(3):121-129
Wide variations among multifaceted-health benefitting attributes of probiotics fueled investigations on targeting efficacious probiotics. In the current study, lactic acid bacteria (LAB) isolated from poultry gut, feces of rat, chicken, human infants, and fermented foods were characterized for desired probiotic functional properties including the phytase-producing ability which is one of the wanted characteristics for probiotics for potential applications for upgrading animal nutrition, enhancing feed conversion, and minimizing anti-nutritional properties. Among 62 LAB isolates Weissella kimchii R-3 an isolate from poultry gut exhibited substantial phytase-producing ability (1.77 U/ml) in addition to other functional probiotic characteristics viz. hydrophobicity, autoaggregation, coaggregation with bacterial pathogens, and antimicrobial activity against pathogens. Survival of W. kimchii R-3 cells (in free and calcium alginate encapsulated state) was examined sequentially in simulated gastric and intestinal juices. Encapsulated cells exhibited better survival under simulated gut conditions indicating that encapsulation conferred considerable protection against adverse gut conditions. Furthermore, simulated gastric and intestinal juices with pepsin and pancreatin showed higher survival of cells than the juices without pepsin and pancreatin. W. kimchii R-3 due to its significant functional probiotic attributes may have prospective for commercial applications in human/animal nutrition. 相似文献
992.
Liliana Serna-Cock Omar Vladimir Pabón-Rodríguez 《Probiotics and antimicrobial proteins》2016,8(2):111-119
A teat bio-sealant was developed using Weissella cibaria, and the bio-sealant’s technological and functional properties were assessed. The development included four experimental phases that were analyzed using independent experimental designs. Initially, sterilized or pasteurized Aloe vera gels were used, and the effect of heat treatment was investigated. In the second phase, the effects of time, storage temperature, and addition of cryopreservatives on the viability of the probiotic were observed. The third phase consisted of evaluating the synergistic effects of the cryopreservatives. The fourth phase involved selecting a material that would provide viscosity to the teat sealant. Technological and functional properties were measured in terms of viability of W. cibaria, and antimicrobial activity against Staphylococcus aureus and Streptococcus agalactiae was also analyzed. A mixture of milk powder and glycerol preserved this antimicrobial activity. Pullulan provided greater viscosity and maintained the technological and functional properties of the bio-sealant for 29 days. This teat bio-sealant can be used as an alternative for the prevention of bovine mastitis. 相似文献
993.
The objectives of this study were to evaluate both face and emotion recognition, to detect differences among attention deficit and hyperactivity disorder (ADHD) subgroups, to identify effects of the gender and to assess the effects of methylphenidate and atomoxetine treatment on both face and emotion recognition in patients with ADHD. The study sample consisted of 41 male, 29 female patients, 8–15 years of age, who were diagnosed as having combined type ADHD (N = 26), hyperactive/impulsive type ADHD (N = 21) or inattentive type ADHD (N = 23) but had not previously used any medication for ADHD and 35 male, 25 female healthy individuals. Long-acting methylphenidate (OROS-MPH) was prescribed to 38 patients, whereas atomoxetine was prescribed to 32 patients. The reading the mind in the eyes test (RMET) and Benton face recognition test (BFRT) were applied to all participants before and after treatment. The patients with ADHD had a significantly lower number of correct answers in child and adolescent RMET and in BFRT than the healthy controls. Among the ADHD subtypes, the hyperactive/impulsive subtype had a lower number of correct answers in the RMET than the inattentive subtypes, and the hyperactive/impulsive subtype had a lower number of correct answers in short and long form of BFRT than the combined and inattentive subtypes. Male and female patients with ADHD did not differ significantly with respect to the number of correct answers on the RMET and BFRT. The patients showed significant improvement in RMET and BFRT after treatment with OROS-MPH or atomoxetine. Patients with ADHD have difficulties in face recognition as well as emotion recognition. Both OROS-MPH and atomoxetine affect emotion recognition. However, further studies on the face and emotion recognition are needed in ADHD. 相似文献
994.
995.
It is important to conserve bryophyte diversity in fragmented forests, due to the vulnerability of this group to environmental change. In this study, the utility of bryophyte functional groups (taxonomic classes, substrate classes, and life-forms) was examined as indicators for planning urban area conservation of bryophyte diversity. The study sites comprised 27 fragmented forests in Kyoto City, Japan. Using linear regression models, it was found that the species richness of almost all functional groups was positively correlated with patch size. Furthermore, two types of bryophyte life-form (fans and thalloid mats) were significantly correlated with environmental factors considered important for conservation planning. The species richness of fan bryophytes was positively correlated with the presence of natural forest patches and was negatively correlated with distance from mountainous areas. Similarly, the species richness of thalloid mat bryophytes was negatively correlated with maintenance practices. These results may be explained by the vulnerability of these two bryophyte groups to environmentally caused drought stress, accompanied by decreasing patch size, maintenance practices, disturbance, and/or loss of natural vegetation. Considering that drought stress represents a major threat to bryophyte diversity in fragmented forests, the species richness of hygrophilous life-forms (e.g., fans and thalloid mats) may be used as an indicator of fragmented forests that are less affected by drought stress, and these species should be preferentially conserved to maintain high levels of bryophyte diversity. 相似文献
996.
Intrinsically disordered proteins, proteins that do not have a well-defined three-dimensional structure, make up a significant proportion of our proteome and are particularly prevalent in signaling and regulation. Although their importance has been realized for two decades, there is a lack of high-resolution experimental data. Molecular dynamics simulations have been crucial in reaching our current understanding of the dynamical structural ensemble sampled by intrinsically disordered proteins. In this review, we discuss enhanced sampling simulation methods that are particularly suitable to characterize the structural ensemble, along with examples of applications and limitations. The dynamics within the ensemble can be rigorously analyzed using Markov state models. We discuss recent developments that make Markov state modeling a viable approach for studying intrinsically disordered proteins. Finally, we briefly discuss challenges and future directions when applying molecular dynamics simulations to study intrinsically disordered proteins. 相似文献
997.
Multivariate synchronization index (MSI) has been proved to be an efficient method for frequency recognition in SSVEP-BCI systems. It measures the correlation according to the entropy of the normalized eigenvalues of the covariance matrix of multichannel signals. In the MSI method, the estimation of covariance matrix omits the temporally local structure of samples. In this study, a new spatio-temporal method, termed temporally local MSI (TMSI), was presented. This new method explicitly exploits temporally local information in modelling the covariance matrix. In order to evaluate the performance of the TMSI, we performs a comparison between the two methods on the real SSVEP datasets from eleven subjects. The results show that the TMSI outperforms the standard MSI. TMSI benefits from exploiting the temporally local structure of EEG signals, and could be a potential method for robust performance of SSVEP-based BCI. 相似文献
998.
Ru-Jia Yan Hai-Qing Gong Pu-Ming Zhang Shi-Gang He Pei-Ji Liang 《Cognitive neurodynamics》2016,10(3):211-223
Dual-peak responses of retinal ganglion cells (RGCs) are observed in various species, previous researches suggested that both response peaks were involved in retinal information coding. In the present study, we investigated the temporal properties of the dual-peak responses recorded in mouse RGCs elicited by spatially homogeneous light flashes and the effect of the inhibitory inputs mediated by GABAergic and/or glycinergic pathways. We found that the two peaks in the dual-peak responses exhibited distinct temporal dynamics, similar to that of short-latency and long-latency single-peak responses respectively. Pharmacological studies demonstrated that the application of exogenous GABA or glycine greatly suppressed or even eliminated the second peak of the cells’ firing activities, while little change was induced in the first peak. Co-application of glycine and GABA led to complete elimination of the second peak. Moreover, application of picrotoxin or strychnine induced dual-peak responses in some cells with transient responses by unmasking a second response phase. These results suggest that both GABAergic and glycinergic pathways are involved in the dual-peak responses of the mouse RGCs, and the two response peaks may arise from distinct pathways that would converge on the ganglion cells. 相似文献
999.
Many saliency computational models have been proposed to simulate bottom-up visual attention mechanism of human visual system. However, most of them only deal with certain kinds of images or aim at specific applications. In fact, human beings have the ability to correctly select attentive focuses of objects with arbitrary sizes within any scenes. This paper proposes a new bottom-up computational model from the perspective of frequency domain based on the biological discovery of non-Classical Receptive Field (nCRF) in the retina. A saliency map can be obtained according to the idea of Extended Classical Receptive Field. The model is composed of three major steps: firstly decompose the input image into several feature maps representing different frequency bands that cover the whole frequency domain by utilizing Gabor wavelet. Secondly, whiten the feature maps to highlight the embedded saliency information. Thirdly, select some optimal maps, simulating the response of receptive field especially nCRF, to generate the saliency map. Experimental results show that the proposed algorithm is able to work with stable effect and outstanding performance in a variety of situations as human beings do and is adaptive to both psychological patterns and natural images. Beyond that, biological plausibility of nCRF and Gabor wavelet transform make this approach reliable. 相似文献
1000.
Jo?o?Custódio?Fernandes?CardosoEmail author Marcelo?Oliveira?Gonzaga Adriano?Cavalleri Pietro?Kiyoshi?Maruyama Estev?o?Alves-Silva 《Arthropod-Plant Interactions》2016,10(6):477-484
Elucidating the factors determining the occurrence of florivorous organisms is an essential step for comprehending arthropod–plant interactions, especially when considering florivores that use flowers/inflorescences as microhabitats. In this study, we characterize the interaction between florivorous thrips (Thysanoptera) and Palicourea rigida (Rubiaceae), a distylous hummingbird-pollinated shrub. We investigated the relative role of different factors in determining thrips occurrence in the flower and inflorescence microhabitats. Furthermore, we experimentally examined the protective role of corolla influencing thrips exploration of floral buds. Frankliniella musaeperda (Thripidae) was the only species recorded on P. rigida, feeding on floral tissue, pollen and nectar. Thrips occurrence was not related to distyly, but rather to floral stage. Open flowers presented the highest abundance of thrips, followed by senescent flowers and then buds. The experimental opening of buds translated in increased thrips occurrence, indicating that F. musaeperda manage to explore the microhabitat offered by the floral chamber, as long as there is an opening in the corolla. In inflorescences, thrips abundance was negatively related to the number of ants visiting extrafloral nectaries. We found that the marked difference between floral morphs of distylous plants is not necessarily reflected in the abundance of florivores. Thrips seek for floral cavities, preferentially those with fresh tissue, which may confer nutrient-rich food and protection. Buds also provide this; however, the enclosed petals are an effective barrier against F. musaeperda entrance. At inflorescence scale, presence of mutualistic ants in high numbers can drive away these flower-feeding insects. Despite the abundance of thrips in the flowers, there was no evidence of any functional relationship, either of pollination for flowers or of breeding for insects. We demonstrate here that in the flower/inflorescence microhabitat, structural and biotic factors play a key role in the exploitation and occupation by insect florivores. 相似文献