全文获取类型
收费全文 | 2683篇 |
免费 | 185篇 |
专业分类
2868篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 65篇 |
2021年 | 102篇 |
2020年 | 76篇 |
2019年 | 87篇 |
2018年 | 93篇 |
2017年 | 89篇 |
2016年 | 118篇 |
2015年 | 172篇 |
2014年 | 195篇 |
2013年 | 227篇 |
2012年 | 258篇 |
2011年 | 236篇 |
2010年 | 151篇 |
2009年 | 93篇 |
2008年 | 172篇 |
2007年 | 126篇 |
2006年 | 135篇 |
2005年 | 98篇 |
2004年 | 89篇 |
2003年 | 65篇 |
2002年 | 62篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2868条查询结果,搜索用时 31 毫秒
71.
João Luiz M. Aranha Filho Leonardo Dias Meireles Peter W. Fritsch Frank Almeda Angela B. Martins 《Brittonia》2012,64(3):252-256
Symplocos minima, a new species of Symplocos section Hopea from the Itatiaia Plateau in the Atlantic Rain Forest biome of southeastern Brazil, is described and illustrated. This species is distinguished by its densely compact shrubby habit, ascending leaves, fasciculate inflorescences with several persistent bracts, corolla with five to six erect lobes, pistillate flowers with the disc not thickened along the margin, fruiting calyx lobes obscuring the disc, and seeds sub-orbicular in cross section. The new species is morphologically related to S. itatiaiae and S. pentandra, but can be differenciated from them mainly due to the tree habit and fruiting calyx lobes not obscuring the disc in S. itatiaiae and the pistillate flowers with a disc that is thickened along the margin in S. pentandra. 相似文献
72.
73.
74.
Delio José Mora Laila Rigolin Fortunato Leonardo Eurípedes Andrade-Silva Kennio Ferreira-Paim Ivonete Helena Rocha Rakel Rocha Vasconcelos David Nascimento Silva-Teixeira Gabriel Antonio Nogueira Nascentes Mario León Silva-Vergara 《PloS one》2015,10(3)
Cryptococcal meningitis (CM) remains as common life-threatening AIDS-defining illness mainly in resource-limited settings. Previous reports suggested that baseline cytokine profiles can be associated to fungal burden and clinical outcome. This study aimed to evaluate the baseline cytokine profiles in AIDS patients with CM and its relation with the outcome at weeks 2 and 10. Thirty AIDS patients with CM diagnosed by cerebrospinal fluid (CSF) Cryptococcus neoformans positive culture, India ink stain and cryptococcal antigen test were prospectively evaluated. As controls, 56 HIV-infected patients without CM and 48 non-HIV individuals were included. Baseline CSF and sera levels of IL-2, IL-4, IL-8, IL-10, IL-12p40, IL-17A, INF-γ and TNF-α were measured by ELISA. Of 30 CM patients, 24 (80%) were male, median age of 38.1. The baseline CSF high fungal burden and positive blood culture were associated with a positive CSF culture at week 2 (p = 0.043 and 0.029). Most CSF and sera cytokines presented higher levels in CM patients than control subjects (p < 0.05). CSF levels of IL-8, IL-12p40, IL-17A, TNF-α, INF-γ and sera TNF-α were significantly higher among survivors at weeks 2 and 10 (p < 0.05). Patients with increased intracranial pression exhibited CSF IL-10 high levels and poor outcome at week 10 (p = 0.032). Otherwise, baseline CSF log10 IFN-γ and IL-17A were negatively correlated with fungal burden (r = -0.47 and -0.50; p = 0.0175 and 0.0094, respectively). The mortality rate was 33% (10/30) at week 2 and 57% (17/30) at week 10. The severity of CM and the advanced immunodeficiency at admission were related to a poor outcome in these patients. Otherwise, the predominant Th1 cytokines profile among survivors confirms its pivotal role to infection control and would be a prognostic marker in cryptococcal meningitis. 相似文献
75.
Seung-Yeol Park Seon-Joo Yoon Leonardo Freire-de-Lima Jung-Hoe Kim Sen-itiroh Hakomori 《Carbohydrate research》2009,344(12):1479-1486
Growth of epidermoid carcinoma cell lines, A431 and KB, has been known to be controlled by the interaction of epidermal growth factor (EGF) and its receptor (EGFR) with tyrosine kinase. Ganglioside GM3 was previously found to interact with EGFR and to inhibit EGFR tyrosine kinase. However, motility of these cells, controlled by EGFR and ganglioside, was not studied. The present study is focused on the control mechanism of the motility of these cells through interaction of ganglioside, tetraspanin (TSP), and EGFR. Key results are as follows: (i) The level of EGFR expressed in A431 cells is 6 times higher than that expressed in KB cells, and motility of A431 cells is also much higher than that of KB cells, yet growth of A431 cells is either not affected or is inhibited by EGF. In contrast, growth of KB cells is enhanced by EGF. (ii) Levels of TSPs (CD9, CD82, and CD81) expressed in A431 cells are much higher than those expressed in KB cells, and TSPs expressed in A431 cells are reduced by treatment of cells with EtDO-P4, which inhibits the synthesis of glycosphingolipids (GSLs) and gangliosides. (iii) These TSPs are co-immunoprecipitated with EGFR in both A431 and KB cells, indicating that TSPs are closely associated with EGFR. (iv) High motility of A431 cells is greatly reduced, while low motility of KB cells is not affected, by treatment of cells with EtDO-P4. These results, taken together, suggest that there is a close correlation between high motility of A431 cells and high expression of EGFR and TSPs, and between ganglioside GM3/GM2 and TSP. A similar correlation was suggested between the low motility of KB cells and low levels of EGFR and TSP. The correlation between high motility and high level of EGFR with the ganglioside–TSP complex in A431 cells is unique. This is in contrast to our previous studies that indicate that motility of many types of tumor cells is inhibited by a high level of CD9 or CD82, together with growth factor receptors and integrins. 相似文献
76.
Morandi A Pinelli L Petrone A Vatin V Buzzetti R Froguel P Meyre D 《Obesity (Silver Spring, Md.)》2009,17(1):202-206
Ectonucleotide Pyrophosphatase Phosphodiesterase 1 (ENPP1) downregulates insulin signaling by inhibiting the insulin receptor's tyrosine-kinase. K121Q and other ENPP1 single-nucleotide polymorphisms (SNPs), IVS20delT-11 and A/G+1044TGA, have been previously associated with obesity in French children, and the risk haplotype QdelTG has also been associated with this condition in both French and German children. Our aim was to perform a case-control replication study in order to assess the possible association of childhood obesity and overweight with the above-mentioned ENPP1 SNPs, and with the QdelTG haplotype, in the Italian population. A total of 865 healthy Italian children were studied: 453 normal-weight, 243 overweight and 169 obese subjects. Genotyping was performed by Taq-Man or Light-Cycler Technology. The Q variant of K121Q showed a negative association with overweight-obesity under both additive (odds ratio (OR) = 0.74, 95% confidence interval (CI) = 0.57-0.97, P = 0.030) and recessive (OR = 0.32, 95% CI = 0.10-0.97, P = 0.035) modes of inheritance. The Z-score of BMI showed a significant decreasing trend from children K/K homozygous to K/Q heterozygous, and to Q/Q homozygous (0.45 vs. 0.28 vs. -0.19; P = 0.009), according to the additive model. The two other SNPs and the QdelTG haplotype did not exhibit any association with overweight/obesity. This is the first child-based study showing a protective role of the 121Q variant of ENPP1 against overweight/obesity. 相似文献
77.
This contribution describes a new species of Litopeltis from Brazil, L. teresopolitensis
sp. n., which shows similarities with L. paineirensis Lopes & Oliveira, 2010 and L. ribeiropretano Lopes & Oliveira, 2010. It differs in characters of morphology genitalia and configuration, with the median sclerite bearing microspines on the sclerotic apex. A map showing the geographic distribution of the Brazilian species and a key to males of the other species of the genus are also presented. 相似文献
78.
A metagenomic approach based on the use of genus specific primers was developed and utilized to characterize Colletotrichum species associated with the olive phyllosphere and carposphere. Selected markers enabled the specific amplification of almost the entire ITS1-5.8S-ITS2 region of the rDNA and its use as barcode gene. The analysis of different olive samples (green and senescent leaves, floral residues, symptomatic and asymptomatic fruits, and litter leaves and mummies) in three different phenological phases (June, October and December) enabled the detection of 12 genotypes associated with 4 phylotypes identified as C. godetiae, C. acutatum s.s., C. gloeosporioides s.s. and C. kahawae. Another three genotypes were not identified at the level of species but were associated with the species complexes of C. acutatum, C. gloeosporioides and C. boninense sensu lato. Colletotrichum godetiae and C. acutatum s.s. were by far the most abundant while C. gloeosporioides s.s. was detected in a limited number of samples whereas ther phylotypes were rarely found. The high incidence of C. acutatum s.s. represents a novelty for Italy and more generally for the Mediterranean basin since it had been previously reported only in Portugal. As regards to the phenological phase, Colletotrichum species were found in a few samples in June and were diffused on all assessed samples in December. According to data new infections on olive tissues mainly occur in the late fall. Furthermore, Colletotrichum species seem to have a saprophytic behavior on floral olive residues. The method developed in the present study proved to be valuable and its future application may contribute to the study of cycle and aetiology of diseases caused by Colletotrichum species in many different pathosystems. 相似文献
79.
Biogeographical analyses are applied to skipper (Hesperioidea) presence/absence data from the Western Mediterranean mainland and the three largest islands (Sardinia, Corsica and Sicily) in order to identify potential conservation issues. The analyses performed on species, both collectively and individually, indicate that regional species richness and occurrence in the Mediterranean zone are largely predicted by latitude and area but that islands have impoverished faunas. Several species, predicted to be present on these islands from logistic regression of their continental distributions, are actually absent. The number of species predicted to be present from logistic regression analyses for each island, closely matched the number of species predicted to occur in regional-focused multiple regression analysis. This suggests that missing species have been identified. When compared with species that occur in Sicily and Corsica, the missing species are shown to differ for ecological traits, mainly those linked to altitudinal tolerance. No ecological distinctions were disclosed for Sardinian skippers suggesting a mainly stochastic colonisation. These results, and those from an analogous study carried out on Papilionoidea, point to Hesperioidea having (i) overall more impoverished faunas on islands and (ii) being subject to stochastic or historical colonisation events more than Papilionoidea. Species not predicted to occur on islands based on their mainland distributions and ecological traits, are foci for conservation attention. However, as many species becoming extinct on the islands may be irreplaceable, all species, in particular the Sardinian ones, deserve to be conserved. 相似文献
80.
Leonardo Faoro Patrick A. Singleton Gustavo M. Cervantes Frances E. Lennon Nicholas W. Choong Rajani Kanteti Benjamin D. Ferguson Aliya N. Husain Maria S. Tretiakova Nithya Ramnath Everett E. Vokes Ravi Salgia 《The Journal of biological chemistry》2010,285(24):18575-18585
Non-small cell lung cancer (NSCLC) has a poor prognosis and improved therapies are needed. Expression of EphA2 is increased in NSCLC metastases. In this study, we investigated EphA2 mutations in NSCLC and examined molecular pathways involved in NSCLC. Tumor and cell line DNA was sequenced. One EphA2 mutation was modeled by expression in BEAS2B cells, and functional and biochemical studies were conducted. A G391R mutation was detected in H2170 and 2/28 squamous cell carcinoma patient samples. EphA2 G391R caused constitutive activation of EphA2 with increased phosphorylation of Src, cortactin, and p130Cas. Wild-type (WT) and G391R cells had 20 and 40% increased invasiveness; this was attenuated with knockdown of Src, cortactin, or p130Cas. WT and G391R cells demonstrated a 70% increase in focal adhesion area. Mammalian target of rapamycin (mTOR) phosphorylation was increased in G391R cells with increased survival (55%) compared with WT (30%) and had increased sensitivity to rapamycin. A recurrent EphA2 mutation is present in lung squamous cell carcinoma and increases tumor invasion and survival through activation of focal adhesions and actin cytoskeletal regulatory proteins as well as mTOR. Further study of EphA2 as a therapeutic target is warranted. 相似文献