全文获取类型
收费全文 | 766篇 |
免费 | 58篇 |
国内免费 | 5篇 |
专业分类
829篇 |
出版年
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 27篇 |
2017年 | 30篇 |
2016年 | 37篇 |
2015年 | 54篇 |
2014年 | 54篇 |
2013年 | 61篇 |
2012年 | 53篇 |
2011年 | 55篇 |
2010年 | 56篇 |
2009年 | 31篇 |
2008年 | 35篇 |
2007年 | 19篇 |
2006年 | 27篇 |
2005年 | 32篇 |
2004年 | 24篇 |
2003年 | 14篇 |
2002年 | 26篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 5篇 |
1998年 | 17篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有829条查询结果,搜索用时 15 毫秒
21.
A. J. Pérez Matos R. N. Planken B. J. Bouma M. Groenink A. P. C. M. Backx R. J. de Winter D. R. Koolbergen B. J. M. Mulder S. M. Boekholdt 《Netherlands heart journal》2014,22(5):240-245
Patients with congenital heart disease corrected in early childhood may later in life present with cardiac symptoms caused by other associated congenital anomalies that were initially not diagnosed. Nowadays, several noninvasive imaging modalities are available for the visualisation of cardiac anatomy in great detail. We describe two patients with an unroofed coronary sinus, a rare congenital anomaly which could be diagnosed using a combination of modalities including echocardiography, cardiac CT and cardiac MRI. 相似文献
22.
Nitroso-aldicarb was tested for its ability to induce sister-chromatid exchanges (SCE) and cell-cycle delay in human peripheral blood lymphocytes in vitro. This derivative of aldicarb induced a dose-dependent increase in SCE values per cell. In addition, a slight decrease in the successive mitotic progression of cells in culture was observed. 相似文献
23.
Pinheiro RO Pinto EF Lopes JR Guedes HL Fentanes RF Rossi-Bergmann B 《Microbes and infection / Institut Pasteur》2005,7(13):1317-1323
Leishmania amazonensis and Leishmania braziliensis are the main causal agents of anergic diffuse cutaneous leishmaniasis and hyperergic mucosal leishmaniasis in man, respectively. In this work we demonstrate that intramuscular vaccination of BALB/c mice with whole antigens of L. amazonensis (LaAg) but not L. braziliensis (LbAg) results in increased susceptibility to cutaneous leishmaniasis. LaAg vaccination resulted in an increased capacity of the draining lymph nodes to produce IL-10 and TGF-beta during antigen recall responses. In vitro cultivation with LaAg but not LbAg induced increased apoptosis of CD8+ T cells. Following infection with L. amazonensis, LaAg-vaccinated mice produced significantly more TGF-beta and a higher serum IgG1/IgG2a antibody ratio compared with LbAg-vaccinated and non-vaccinated animals. The association of TGF-beta with enhanced susceptibility to infection was confirmed in mice co-vaccinated with LaAg and neutralizing anti-TGF-beta antibodies. Upon parasite challenge, these animals developed much smaller lesion sizes and parasite burdens, comparable with non-vaccinated controls. The disease-promoting effect of LaAg vaccination is not a general event, as in contrast to BALB/c, the disease outcome in C57Bl/6 mice was unaltered. Together, these findings indicate that species-specific components of L. amazonensis activate overt TGF-beta production that predisposes more susceptible individuals to aggravated disease following vaccination. 相似文献
24.
Isabel C.M. Fensterseifer Mário R. Felício Eliane S.F. Alves Marlon H. Cardoso Marcelo D.T. Torres Carolina O. Matos Osmar N. Silva Timothy K. Lu Maurício V. Freire Natan C. Neves Sónia Gonçalves Luciano M. Lião Nuno C. Santos William F. Porto Cesar de la Fuente-Nunez Octavio L. Franco 《生物化学与生物物理学报:生物膜》2019,1861(7):1375-1387
Infections caused by Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa foremost among them, constitute a major worldwide health problem. Bioinformatics methodologies are being used to rationally design new antimicrobial peptides, a potential alternative for treating these infections. One of the algorithms used to develop antimicrobial peptides is the Joker, which was used to design the peptide PaDBS1R6. This study evaluates the antibacterial activities of PaDBS1R6 in vitro and in vivo, characterizes the peptide interaction to target membranes, and investigates the PaDBS1R6 structure in contact with mimetic vesicles. Moreover, we demonstrate that PaDBS1R6 exhibits selective antimicrobial activity against Gram-negative bacteria. In the presence of negatively charged and zwitterionic lipids the structural arrangement of PaDBS1R6 transits from random coil to α-helix, as characterized by circular dichroism. The tertiary structure of PaDBS1R6 was determined by NMR in zwitterionic dodecylphosphocholine (DPC) micelles. In conclusion, PaDBS1R6 is a candidate for the treatment of nosocomial infections caused by Gram-negative bacteria, as template for producing other antimicrobial agents. 相似文献
25.
Thiago Corsi Filiponi Lúcio Roberto Requi?o-Moura Eduardo José Tonato Ana Cristina Carvalho de Matos Alvaro Pacheco e Silva-Filho Marcelino de Souza Dur?o Junior 《PloS one》2015,10(9)
The incidence and outcomes of acute kidney injury (AKI) in kidney transplantation are poorly known. Retrospective cohort analysis was performed on the data of all patients (≥3 months after transplantation and ≥16 years of age) admitted to the hospital due to medical or surgical complications from 2007 to 2010. We analyzed 458 kidney transplant recipients, 55.2% men, median age 49 (IQR, 36–58) years, median of 12.5 (IQR, 3–35) months after kidney transplantation; admitted to the hospital due to medical or surgical complications. Most of the patients received a kidney from a deceased donor (62.2%), the primary cause for hospital admission was infection (60.7%) and 57 (12.4%) individuals were diagnosed with acute rejection (AR). The incidence of AKI was 82.3%: 31.9% stage 1, 29.3% stage 2 and 21.2% stage 3. Intensive care unit (ICU) admission (OR 8.90, 95% CI: 1.77–44.56 p = 0.008), infection (OR 5.73, 95% CI: 2.61–12.56, p<0.001) and the use of contrast media (OR 9.34, 95% CI: 2.04–42.70, p = 0.004) were the independent risk factors for AKI development. The mortality rate was 2.1% and all patients who died were diagnosed with AKI. Even after the exclusion of AR cases, at the end of 12 months, the individuals with AKI exhibited higher percent changes in creatinine values when compared with individuals without AKI (9.1% vs. -4.3%; p<0.001). According to KDIGO system, we found a high incidence of AKI among the complications of renal transplantation. As in other scenarios, AKI was associated with renal function loss at 1-year after the hospital discharge. 相似文献
26.
27.
Geert Zegels Geert AA Van Raemdonck Edmond P Coen Wiebren AA Tjalma Xaveer WM Van Ostade 《Proteome science》2009,7(1):17-16
Background
Cervical-vaginal fluid (CVF) plays an important role in the prevention of gynecological infections, although little is known about the contribution of CVF proteins to the immunity of the lower female genital tract. In order to analyze the protein composition of human CVF, we used CVF samples that are routinely collected during colposcopy, but are usually discarded. Since these samples are available in large quantities we aimed to analyze their usefulness for proteomics experiments. The samples were analyzed using different prefractionation techniques (ultrafiltration and C4(RP)-LC protein separation) followed by C18(RP)-LC peptide separation and identification by MALDI-TOF-TOF mass spectrometry. To determine the reproducibility of this proteomics platform we analyzed three technical replicates. Using spectral counting, protein abundances were estimated in a semiquantitative way. We also compared the results obtained in this study with those from previous studies derived from patients with different physiological conditions in order to determine an overlapping protein set. 相似文献28.
The interplay between event and background sedimentation and the origin of fossil‐rich carbonate concretions: a case study in Permian rocks of the Paraná Basin,Brazil 下载免费PDF全文
João G. Bondioli Suzana A. Matos Lucas V. Warren Mário L. Assine Cláudio Riccomini Marcello G. Simões 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2015,48(4):522-539
The Permian Serra Alta Formation was generated under transgressive conditions within a large, calm epeiric sea. A monotonous succession of ‘barren’, massive mudstones deposited under oxygen‐deficient conditions (mainly below storm wave base) is the main lithofacies of this unit. Fossils are generally rare and diluted in the matrix, but certain intervals contain shell‐rich concentrations with well‐preserved, closed articulated bivalves, mixed with shells and comminuted debris with variable quality of preservation, all encased in carbonate concretions. Two main scenarios may account for the origin of these bivalve‐rich concretions (i.e. unique events in sea‐water chemistry or unique burial‐starvation couplets). Sedimentological and taphonomic information indicates that the final deposition of the original shell‐rich mudstone intervals was probably tied to episodic influx of fine‐grained sediments in distal settings. Moderate bioturbation is also recorded suggesting low rates of sedimentation prior to early diagenesis. Hence, the fossil concentrations in concretions were formed due to the interplay of event and background sedimentation. These are internally simple concentrations with complex depositional histories. The concretion‐bearing beds are not randomly distributed in the Serra Alta Formation. Rather, they are found in the sparsely fossiliferous offshore deposits of the basal to intermediate portions of the unit. Thus, the concretionary mudstone beds and associated deposits are preserved in particular intervals and can be tracked for kilometres. This indicates that the conditions essential for concretion development existed only at particular stratigraphical intervals. Finally, our study strongly corroborates the idea that concretions are critical sources of sedimentological, taphonomic and stratigraphical information. 相似文献
29.
Patrícia Ferraz de Matos 《The journal of the Royal Anthropological Institute》2020,26(1):211-212
30.
Tamara Daiane de Souza Antonio Teixeira de Matos Renato Welmer Veloso Amanda Fernandes Braga 《International journal of phytoremediation》2018,20(11):1129-1135
This study aimed to evaluate the pH, phosphate, and nitrate in the process of arsenic absorption by Eichhornia crassipes (water hyacinth), using the surface response methodology, in order to optimize the process. The plants were exposed to a concentration of arsenic of 0.5 mg L?1 (NaAsO2) over a period of 10 days. The results indicated optimal levels for the absorption of arsenic by E. crassipes at pH equal to 7.5, absence of phosphate, and minimum nitrate level of 0.0887 mmol L?1. For the tested concentration, E. crassipes was able to accumulate 498.4 mg kg?1 of As (dry base) in its plant tissue and to reduce 83% of the initial concentration present in the aqueous medium where it was cultivated. The concentration of phosphorus in solution linearly increased the phosphorus content in the plants and negatively influenced the absorption of arsenic. The concentration of 0.5 mg L?1 of As did not significantly affect the relative growth rate (RGR) and the tolerance index (TI). 94% of As (III) initially solubilized in water was converted by the end of the experiment period into As (V). The water hyacinth was important in the phytoremediation of arsenic when cultivated under optimal conditions for its removal. 相似文献