全文获取类型
收费全文 | 94943篇 |
免费 | 406篇 |
国内免费 | 887篇 |
专业分类
96236篇 |
出版年
2022年 | 17篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 22篇 |
2018年 | 11856篇 |
2017年 | 10684篇 |
2016年 | 7477篇 |
2015年 | 643篇 |
2014年 | 336篇 |
2013年 | 395篇 |
2012年 | 4291篇 |
2011年 | 12889篇 |
2010年 | 12044篇 |
2009年 | 8267篇 |
2008年 | 9850篇 |
2007年 | 11448篇 |
2006年 | 363篇 |
2005年 | 583篇 |
2004年 | 1050篇 |
2003年 | 1094篇 |
2002年 | 853篇 |
2001年 | 327篇 |
2000年 | 223篇 |
1999年 | 90篇 |
1998年 | 18篇 |
1997年 | 37篇 |
1996年 | 21篇 |
1994年 | 16篇 |
1993年 | 41篇 |
1992年 | 61篇 |
1991年 | 68篇 |
1990年 | 39篇 |
1989年 | 42篇 |
1988年 | 41篇 |
1987年 | 37篇 |
1986年 | 20篇 |
1985年 | 23篇 |
1984年 | 32篇 |
1983年 | 41篇 |
1981年 | 16篇 |
1979年 | 18篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1975年 | 20篇 |
1974年 | 21篇 |
1972年 | 268篇 |
1971年 | 287篇 |
1970年 | 20篇 |
1965年 | 20篇 |
1962年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Jason J. Kolbe Johanna E. Wegener Yoel E. Stuart Ushuaia Milstead Katherine E. Boronow Alexis S. Harrison Jonathan B. Losos 《Biological invasions》2017,19(7):1989-1998
Human-mediated dispersal has reshaped distribution patterns and biogeographic relationships for many taxa. Long-distance and over-water dispersal were historically rare events for most species, but now human activities can move organisms quickly over long distances to new places. A potential consequence of human-mediated dispersal is the eventual reintroduction of individuals from an invasive population back into their native range; a dimension of biological invasion termed “cryptic back-introduction.” We investigated whether this phenomenon was occurring in the Cayman Islands where brown anole lizards (Anolis sagrei) with red dewlaps (i.e., throat fans), either native to Little Cayman or invasive on Grand Cayman, have been found on Cayman Brac where the native A. sagrei have yellow dewlaps. Our analysis of microsatellite data shows strong population-genetic structure among the three Cayman Islands, but also evidence for non-equilibrium. We found some instances of intermediate multilocus genotypes (possibly 3–9% of individuals), particularly between Grand Cayman and Cayman Brac. Furthermore, analysis of dewlap reflectance data classified six males sampled on Cayman Brac as having red dewlaps similar to lizards from Grand Cayman and Little Cayman. Lastly, one individual from Cayman Brac had an intermediate microsatellite genotype, a red dewlap, and a mtDNA haplotype from Grand Cayman. This mismatch among genetic and phenotypic data strongly suggests that invasive A. sagrei from Grand Cayman are interbreeding with native A. sagrei on Cayman Brac. To our knowledge, this is the first evidence of cryptic back-introduction. Although we demonstrate this phenomenon is occurring in the Cayman Islands, assessing its frequency there and prevalence in other systems may prove difficult due to the need for genetic data in most instances. Cryptic back-introductions may eventually provide some insight into how lineages are changed by the invasion process and may be an underappreciated way in which invasive species impact native biodiversity. 相似文献
992.
Yong-Yeon Jo Sang-Wook Kim Sung-Woo Cho Duck-Ho Bae Hyunok Oh 《Cluster computing》2017,20(2):1155-1166
An intuitive way to process the big data efficiently is to reduce the volume of data transferred over the storage interface to a host system. This is the reason that the notion of intelligent SSD (iSSD) was proposed to give processing power to SSD. There is rich literature on iSSD, however, its real implementation has not been provided to the public yet. Most prior work aims to quantify the benefits of iSSD with analytical modeling. In this paper, we first develop on iSSD simulator and present the potential of iSSD in data mining through the iSSD simulator. Our iSSD simulator performs on top of the gem 5 simulator and fully simulates all the processes of data mining algorithms running in iSSD with cycle-level accuracy. Then, we further addresse how to exploit all the computing resources for efficient processing of data mining algorithms. These days, CPU, GPU, and SSD are recently equipped together in most computing environment. If SSD is replaced with iSSD later on, we have a new computing environment where the three computing resources collaborate one another to process big data quite effectively. For this, scheduling is required to decide which computing resource is going to run for which function at which time. In our heterogeneous scheduling, types of computing resources, memory sizes in computing resources, and inter-processor communication times including IO time in SSD are considered. Our scheduling results show that processing in the collaborative environment outperforms that in the traditional one by up to about 10 times. 相似文献
993.
994.
Objectives
With the view of designing a single biocatalyst for biorefining, carbazole dioxygenase was cloned from Pseudomonas sp. and expressed in Rhodococcus sp.Results
The recombinant, IGTS8, degraded both carbazole and dibenzothiophene at 400 mg/l in 24 h. Maximum carbazole degradation was in 1:1 (v/v) hexadecane/aqueous phase. Anthracene, phenanthrene, pyrene, fluoranthene and fluorine were also degraded without affecting the aliphatic component.Conclusions
Recombinant Rhodococcus sp. IGTS8 can function as a single biocatalyst for removing major contaminants of fossil fuels viz. dibenzothiophene, carbazole and polyaromatic compounds.995.
Dongping Mo Daheng Yang Xuelian Xiao Ruihong Sun Lei Huang Jian Xu 《Biotechnology letters》2017,39(5):701-710
Objective
To investigate the roles of miR-145 in lung adenocarcinoma (LAC) and to clarify the regulation of N-cadherin by miR-145.Results
In 57 paired clinical LAC tissues, diminished miR-145 was significantly correlated with the lymph node metastasis and was negatively correlated with N-cadherin mRNA level expression. Wound healing and transwell assays revealed a reduced capability of tumor metastasis induced by miR-145 in LAC. miR-145 negatively regulated the invasion of cell lines through targeting N-cadherin by directly binding to its 3′-untranslated region. Silencing of N-cadherin inhibited invasion and migration of LAC cell lines similar to miR-145 overexpression.Conclusions
MiR-145 could inhibit invasion and migration of lung adenocarcinoma cell lines by directly targeting N-cadherin.996.
Giordana Grossi 《Biology & philosophy》2017,32(6):1047-1082
“Hardwired” is a term commonly used to describe the properties of certain behaviors or brain regions. As its usage has increased exponentially in the past 50 years, both in popular media and the scholarly literature, the concept appears to have gained a cloak of respectability in scientific discourse. However, its specific meaning is difficult to pinpoint. In this paper, I examine how “hardwired” has been used in the psychological and neuroscientific literature. The analysis reveals two major themes: one centers on certain purported characteristics of behaviors or brain regions, such as fixedness; the other places these and other characteristics within an evolutionary framework. Overall, the analysis reveals a degree of overlap between “hardwiring” and the folk biology concept of innateness. Various complications arise from such overlap, casting doubts on the usefulness and legitimacy of “hardwired” in scientific discourse. 相似文献
997.
Dongmei Chen Qinwei Song Runan Zhu Yuan Qian Yu Sun Jie Deng Fang Wang Yaxin Ding Run Tian Chuanhe Liu Wenjing Zhu Linqing Zhao 《中国病毒学》2017,32(2):171-174
<正>Dear Editor,Cumulative evidence supports the role of early-life viral infections,especially respiratory syncytial virus(RSV)and human rhinovirus(HRV),as major antecedents of childhood asthma(Lemanske,2002;Jackson et al.,2008).In this study,the x TAG respiratory viral panel FAST(RVP FAST)assay,a multiplex polymerase chain reaction(PCR)-based method(Arens et al.,2010;BaladaLlasat et al.,2011;Gharabaghi et al.,2011;Selvaraju,2012),was used to investigate the association of infec- 相似文献
998.
999.
Moheb Ali Pourgholam Hossein Khara Reza Safari Mohammad Ali Yazdani Sadati Mohammad Sadegh Aramli 《Probiotics and antimicrobial proteins》2017,9(1):32-40
A feeding trial was conducted to investigate the effects of different levels of dietary Lactobacillus plantarum on hemato-immunological parameters and resistance against Streptococcus iniae infection in juvenile Siberian sturgeon Acipenser baerii. Fish (14.6 ± 2.3 g) were fed three experimental diets prepared by supplementing a basal diet with L. plantarum at different concentrations [1 × 107, 1 × 108 and 1 × 109 colony-forming units (cfu) g?1] and a control (non-supplemented basal) diet for 8 weeks. Innate immune responses (immunoglobulin (Ig), alternative complement activity (ACH50) and lysozyme activity) were significantly higher in fish fed the 1 × 108 and 1 × 109 cfu g?1 L. plantarum diet compared to the other groups (P < 0.05). Furthermore, fish fed on various levels of L. plantarum significantly showed higher red blood cell (RBC), hemoglobin (Hb), white blood cell (WBC) and monocyte compared to those of the control group (P < 0.05). At the end of the feeding experiment, some fish were challenged with S. iniae to quantify the level of disease resistance. The mortality after S. iniae challenge was decreased in fish fed a probiotic. These results indicated that dietary supplementation of L. plantarum improved immune response and disease resistance of Siberian sturgeon juvenile. 相似文献
1000.