全文获取类型
收费全文 | 21918篇 |
免费 | 1499篇 |
国内免费 | 9篇 |
专业分类
23426篇 |
出版年
2024年 | 19篇 |
2023年 | 126篇 |
2022年 | 311篇 |
2021年 | 580篇 |
2020年 | 351篇 |
2019年 | 470篇 |
2018年 | 593篇 |
2017年 | 478篇 |
2016年 | 809篇 |
2015年 | 1215篇 |
2014年 | 1343篇 |
2013年 | 1659篇 |
2012年 | 1948篇 |
2011年 | 1892篇 |
2010年 | 1174篇 |
2009年 | 1016篇 |
2008年 | 1376篇 |
2007年 | 1287篇 |
2006年 | 1179篇 |
2005年 | 1081篇 |
2004年 | 981篇 |
2003年 | 927篇 |
2002年 | 751篇 |
2001年 | 117篇 |
2000年 | 106篇 |
1999年 | 135篇 |
1998年 | 125篇 |
1997年 | 115篇 |
1996年 | 89篇 |
1995年 | 86篇 |
1994年 | 90篇 |
1993年 | 88篇 |
1992年 | 53篇 |
1991年 | 56篇 |
1990年 | 62篇 |
1989年 | 45篇 |
1988年 | 50篇 |
1987年 | 38篇 |
1986年 | 42篇 |
1985年 | 51篇 |
1984年 | 39篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 42篇 |
1980年 | 26篇 |
1979年 | 34篇 |
1978年 | 32篇 |
1977年 | 29篇 |
1976年 | 25篇 |
1975年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
Anna Särnblad Magnus Danbolt Love Dalén Omar A. Amir Per Berggren 《Marine Mammal Science》2011,27(2):431-448
Phylogenetic placement of bottlenose dolphins from Zanzibar, East Africa and putative population differentiation between animals found off southern and northern Zanzibar were examined using variation in mtDNA control region sequences. Samples (n= 45) from animals bycaught in fishing gear and skin biopsies collected during boat surveys were compared to published sequences (n= 173) of Indo‐Pacific bottlenose dolphin, Tursiops aduncus, from southeast Australian waters, Chinese/Indonesian waters, and South African waters (which recently was proposed as a new species) and to published sequences of common bottlenose dolphin, Tursiops truncatus. Bayesian and maximum parsimony analyses indicated a close relationship between Zanzibar and South African haplotypes, which are differentiated from both Chinese/Indonesian and Australian T. aduncus haplotypes. Our results suggest that the dolphins found off Zanzibar should be classified as T. aduncus alongside the South African animals. Further, analyses of genetic differentiation showed significant separation between the T. aduncus found off northern and southern Zanzibar despite the relatively short distance (approximately 80 km) between these areas. Much less differentiation was found between southern Zanzibar and South Africa, suggesting a more recent common evolutionary history for these populations than for the northern and southern Zanzibar populations. 相似文献
902.
903.
A PBX1 transcriptional network controls dopaminergic neuron development and is impaired in Parkinson's disease 下载免费PDF全文
J Carlos Villaescusa Bingsi Li Enrique M Toledo Pia Rivetti di Val Cervo Shanzheng Yang Simon RW Stott Karol Kaiser Saiful Islam Daniel Gyllborg Rocio Laguna‐Goya Michael Landreh Peter Lönnerberg Anna Falk Tomas Bergman Roger A Barker Sten Linnarsson Licia Selleri Ernest Arenas 《The EMBO journal》2016,35(18):1963-1978
904.
Gene flow is a fundamental evolutionary force in adaptation that is especially important to understand as humans are rapidly changing both the natural environment and natural levels of gene flow. Theory proposes a multifaceted role for gene flow in adaptation, but it focuses mainly on the disruptive effect that gene flow has on adaptation when selection is not strong enough to prevent the loss of locally adapted alleles. The role of gene flow in adaptation is now better understood due to the recent development of both genomic models of adaptive evolution and genomic techniques, which both point to the importance of genetic architecture in the origin and maintenance of adaptation with gene flow. In this review, we discuss three main topics on the genomics of adaptation with gene flow. First, we investigate selection on migration and gene flow. Second, we discuss the three potential sources of adaptive variation in relation to the role of gene flow in the origin of adaptation. Third, we explain how local adaptation is maintained despite gene flow: we provide a synthesis of recent genomic models of adaptation, discuss the genomic mechanisms and review empirical studies on the genomics of adaptation with gene flow. Despite predictions on the disruptive effect of gene flow in adaptation, an increasing number of studies show that gene flow can promote adaptation, that local adaptations can be maintained despite high gene flow, and that genetic architecture plays a fundamental role in the origin and maintenance of local adaptation with gene flow. 相似文献
905.
Building strong relationships between conservation genetics and primary industry leads to mutually beneficial genomic advances 下载免费PDF全文
Stephanie J. Galla Thomas R. Buckley Rob Elshire Marie L. Hale Michael Knapp John McCallum Roger Moraga Anna W. Santure Phillip Wilcox Tammy E. Steeves 《Molecular ecology》2016,25(21):5267-5281
Several reviews in the past decade have heralded the benefits of embracing high‐throughput sequencing technologies to inform conservation policy and the management of threatened species, but few have offered practical advice on how to expedite the transition from conservation genetics to conservation genomics. Here, we argue that an effective and efficient way to navigate this transition is to capitalize on emerging synergies between conservation genetics and primary industry (e.g., agriculture, fisheries, forestry and horticulture). Here, we demonstrate how building strong relationships between conservation geneticists and primary industry scientists is leading to mutually‐beneficial outcomes for both disciplines. Based on our collective experience as collaborative New Zealand‐based scientists, we also provide insight for forging these cross‐sector relationships. 相似文献
906.
In vitro micropropagation by direct organogenesis and somatic embryogenesis via callus was developed for Crambe tataria (Brassicaceae). C. tataria is an endemic species of the Pontic-Pannonic region, but it is also present in Italy, where it is localized in Friuli on
a characteristic grassland formation, called “magredi”. C. tataria is regarded as an endangered species. Leaf and root explants were subjected to plant regulator treatments, which invoked
different morphogenic responses. Leaf explants produced more callus than root explants and a higher amount of callus was obtained
with 1 mg l−1 2,4-D in combination with 2 mg l−1 Kin. Somatic embryogenesis was obtained in calli maintained in a delayed subculture regime on media containing BAP in combination
with NAA. Root explants cultured with BAP combined with NAA developed adventitious rosette shoots. Shoots rooted on half-strength
MS media, and the number of roots per plantlet and their length were heavily dependent on sucrose content. The in vitro regenerated
plantlets were acclimatized ex vitro and a mean of 50% of the plantlets survived and showed a true-to-type growth habit. This
study describes the development of two in vitro micropropagation protocols, via direct organogenesis and via embryogenesis
from callus, that are the basis for the application of in vitro tools for the establishment of basal collections with representative
genetic diversity and for the long-term storage of plant genetic material. 相似文献
907.
908.
Tadeusz Osadnik Joanna Katarzyna Strzelczyk Rafa? Regu?a Kamil Bujak Martyna Fronczek Ma?gorzata Gonera Marcin Gawlita Jaros?aw Wasilewski Andrzej Lekston Anna Kurek Marek Gierlotka Przemys?aw Trzeciak Micha? Hawranek Zofia Ostrowska Andrzej Wiczkowski Lech Poloński Mariusz G?sior 《PloS one》2016,11(3)
Background
Neointima forming after stent implantation consists of vascular smooth muscle cells (VSMCs) in 90%. Growth factors TGF-β1, PDGFB, EGF, bFGF and VEGF-A play an important role in VSMC proliferation and migration to the tunica intima after arterial wall injury. The aim of this paper was an analysis of functional polymorphisms in genes encoding TGF-β1, PDGFB, EGF, bFGF and VEGF-A in relation to in-stent restenosis (ISR).Materials and Methods
265 patients with a stable coronary artery disease (SCAD) hospitalized in our center in the years 2007–2011 were included in the study. All patients underwent stent implantation at admission to the hospital and had another coronary angiography performed due to recurrence of the ailments or a positive result of the test assessing the coronary flow reserve. Angiographically significant ISR was defined as stenosis >50% in the stented coronary artery segment. The patients were divided into two groups–with angiographically significant ISR (n = 53) and without significant ISR (n = 212). Additionally, the assessment of late lumen loss (LLL) in vessel was performed. EGF rs4444903 polymorphism was genotyped using the PCR-RFLP method whilst rs1800470 (TGFB1), rs2285094 (PDGFB) rs308395 (bFGF) and rs699947 (VEGF-A) were determined using the TaqMan method.Results
Angiographically significant ISR was significantly less frequently observed in the group of patients with the A/A genotype of rs1800470 polymorphism (TGFB1) versus patients with A/G and G/G genotypes. In the multivariable analysis, LLL was significantly lower in patients with the A/A genotype of rs1800470 (TGFB1) versus those with the A/G and G/G genotypes and higher in patients with the A/A genotype of the VEGF-A polymorphism versus the A/C and C/C genotypes. The C/C genotype of rs2285094 (PDGFB) was associated with greater LLL compared to C/T heterozygotes and T/T homozygotes.Conclusions
The polymorphisms rs1800470, rs2285094 and rs6999447 of the TGFB1, PDGFB and VEGF-A genes, respectively, are associated with LLL in patients with SCAD treated by PCI with a metal stent implantation. 相似文献909.
Ravi Prakash Suneedh Manthri Shaikh Tayyaba Anna Joy Sunil Saksena Raj Devender Singh Ashok Agarwal 《PloS one》2016,11(3)
Background
Violence against sex workers can heighten their vulnerability to HIV and other sexually transmitted infections (STIs). Evidence suggests the risk of acquiring STI/HIV infections among female sex workers (FSWs) who have experienced violence to be almost three-times higher than FSWs, who have not experienced violence. Moreover, an experience of physical and sexual violence makes it difficult for them to negotiate safer sex with their partners and often act as a barrier to utilization of prevention services.Methods
This study utilizes data from 2785 FSWs aged 18 years and above who participated in a cross-sectional behavioural study conducted during 2013–14 in Thane district, Maharashtra. A probability-based two-stage cluster sampling method was used for data collection. This study assesses the effect of physical violence on self-reported STI symptoms (any STI and multiple STIs) and treatment seeking for the last STI symptom using propensity score matching method.Results
About 18% of sampled FSWs reported physical violence at the time of the survey. The likelihood of experiencing such violence was significantly higher among FSWs who solicited clients at public places, engaged in other economic activities apart from sex work, had savings, and reported high client volume per week. FSWs experiencing violence were also inconsistent condom users while engaging in sex with regular partners and clients. The average adjusted effect of violence clearly depicted an increase in the risk of any STI (11%, p<0.05) and multiple STIs (8%, p<0.10) and reduction in treatment seeking (10%, p<0.05).Conclusions
This study demonstrates a significant effect of physical violence on reporting of any STI symptom and treatment seeking. Findings call for the immediate inclusion of strategies aimed to address violence related challenges in HIV prevention program currently being provided at Thane district. Such strategies would further help in enhancing the access to tailored STI prevention and care services among FSWs in the district. 相似文献910.
Ruslan Hlushchuk Daniel Br?nnimann Carlos Correa Shokiche Laura Schaad Ramona Triet Anna Jazwinska Stefan A. Tschanz Valentin Djonov 《PloS one》2016,11(3)