全文获取类型
收费全文 | 1227篇 |
免费 | 79篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 14篇 |
2021年 | 27篇 |
2020年 | 12篇 |
2019年 | 25篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 40篇 |
2015年 | 61篇 |
2014年 | 76篇 |
2013年 | 76篇 |
2012年 | 98篇 |
2011年 | 105篇 |
2010年 | 64篇 |
2009年 | 53篇 |
2008年 | 86篇 |
2007年 | 93篇 |
2006年 | 82篇 |
2005年 | 53篇 |
2004年 | 53篇 |
2003年 | 44篇 |
2002年 | 46篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1306条查询结果,搜索用时 15 毫秒
91.
Lacadena J Alvarez-García E Carreras-Sangrà N Herrero-Galán E Alegre-Cebollada J García-Ortega L Oñaderra M Gavilanes JG Martínez del Pozo A 《FEMS microbiology reviews》2007,31(2):212-237
RNase T1 is the best known representative of a large family of ribonucleolytic proteins secreted by fungi, mostly Aspergillus and Penicillium species. Ribotoxins stand out among them by their cytotoxic character. They exert their toxic action by first entering the cells and then cleaving a single phosphodiester bond located within a universally conserved sequence of the large rRNA gene, known as the sarcin-ricin loop. This cleavage leads to inhibition of protein biosynthesis, followed by cellular death by apoptosis. Although no protein receptor has been found for ribotoxins, they preferentially kill cells showing altered membrane permeability, such as those that are infected with virus or transformed. Many steps of the cytotoxic process have been elucidated at the molecular level by means of a variety of methodological approaches and the construction and purification of different mutant versions of these ribotoxins. Ribotoxins have been used for the construction of immunotoxins, because of their cytotoxicity. Besides this activity, Aspf1, a ribotoxin produced by Aspergillus fumigatus, has been shown to be one of the major allergens involved in allergic aspergillosis-related pathologies. Protein engineering and peptide synthesis have been used in order to understand the basis of these pathogenic mechanisms as well as to produce hypoallergenic proteins with potential diagnostic and immunotherapeutic applications. 相似文献
92.
93.
94.
Cardenas JC Carvajal J Ruiz A 《Plastic and reconstructive surgery》2007,120(6):1741-2; author reply 1743
95.
Rosmaninho-Salgado J Araújo IM Alvaro AR Duarte EP Cavadas C 《Journal of neurochemistry》2007,103(3):896-903
The adrenal chromaffin cells synthesize and release catecholamine (mostly epinephrine and norepinephrine) and different peptides, such as the neuropeptide Y (NPY). NPY stimulates catecholamine release through NPY Y1 receptor in mouse chromaffin cells. The aim of our study was to determine the intracellular signaling events coupled to NPY Y1 receptor activation that lead to stimulation of catecholamine release from mouse chromaffin cells. The stimulatory effect of NPY mediated by NPY Y1 receptor activation was lost in the absence of extracellular Ca2+. On the other hand, inhibition of nitric oxide synthase and guanylyl cyclase also decreased the stimulatory effect of NPY. Moreover, catecholamine release stimulated by NPY or by the nitric oxide donor (NOC-18) was inhibited by mitogen-activated protein kinase (MAPK) and protein kinase C inhibitors. In summary, in mouse chromaffin cells, NPY evokes catecholamine release by the activation the NPY Y1 receptor, in a Ca2+-dependent manner, by activating mitogen-activated protein kinase and promoting nitric oxide production, which in turn regulates protein kinase C and guanylyl cyclase activation. 相似文献
96.
OBJECTIVE: To determine the value of cytology in detecting mature and immature papillary condylomas of the uterine cervix. STUDY DESIGN: We evaluated 240 cases of plane cervical intraepithelial neoplasia, grade 1 (CIN 1), and 23 papillary condylomas by Pap smear and biopsy and classified histologic sections according to maturity and keratinization. We reevaluated corresponding cytologic smears and identified criteria of low grade squamous lesion (LSIL) and human papillomavirus (HPV) infection. RESULTS: Thirteen (56.5%) papillary lesions were histologically classified as mature, 6 (26%) as immature and 4 (17.3%) as mixed. Fifteen lesions (65.2%) were nonkeratinized, 2 (8.6%) keratinized and 6 (26%) partially keratinized. Corresponding smears were cytologically diagnosed as LSIL (6, 26%), atypical squamous cells of undetermined significance (ASCUS) (7, 30.4%) and negative (10, 43.4%). Careful cytologic review diagnosed only two of the 13 mature lesions; few cytological criteria of LSIL and HPV infection were observed. Koilocytes were seen in just 1 case. Sample limiting factors occurred in 4 cases: 2 cytologically diagnosed as LSIL, 1 asASCUS and 1 as negative for lesion. CONCLUSION: Cytology was not effective in the detection of cervical condyloma acuminatum, independent of limitations in sample adequacy and of the degree of maturity or keratinization of the lesions. 相似文献
97.
Martínez H Rodríguez-Larralde A Izaguirre MH De Guerra DC 《Human biology; an international record of research》2007,79(2):201-213
The present Venezuelan population is the product of admixture of Amerindians, Europeans, and Africans, a process that was not homogeneous throughout the country. Blood groups, short tandem repeats (STRs), mtDNA, and Y-chromosome markers have been used successfully in admixture studies, but few such studies have been conducted in Venezuela. In this study we aim to estimate the admixture components of samples from two different socioeconomic levels from Caracas, Venezuela's capital city, compare their differences, and infer sexual asymmetry in the European Amerindian union patterns. Gene frequencies for blood groups ABO and Rh (CDE) and for the STRs VWA, F13A01, and FES/FPS and mtDNA and Y-chromosome haplogroups were studied in a sample of 60 individuals living in Caracas, taken from a private clinic (high socioeconomic level), and 50 individuals, also living in Caracas, drawn from a public maternity clinic (low socioeconomic level). The admixture analysis for the five autosomal markers gives a high European component (0.78) and an almost negligible African sub-Saharan component (0.06) for the high socioeconomic level, whereas for the low socioeconomic level the sub-Saharan, European, and Amerindian components were 0.21, 0.42, and 0.36, respectively. Estimates of admixture based on mtDNA and Y-chromosome markers reveal that the Amerindian contribution to these Caracas samples is almost entirely through females, because the Y-chromosome Amerindian and African sub-Saharan chromosomes found in this study were scarce. Our study reveals that the identification of the grandparents' geographic origin is an important methodological aspect to take into account in genetic studies related to the reconstruction of historical events. 相似文献
98.
Although there is a general understanding of Montagu’s harriers migration routes and wintering areas, detailed information
on the species’ migration is still lacking. However, improvements in satellite tracking technology in recent years, have enabled
the study of medium-sized species by means of satellite telemetry. In 2006, ten adult Montagu’s harriers were fitted with
satellite transmitters in northeastern Spain and tracked during their autumn migration to their wintering grounds in sub-Saharan
Africa. The migration took between 10 and 30 days, and the end point was determined using breakpoint regressions. Whereas
some birds had stopovers of more than a week, others stayed at the same site for only 1 or 2 days at the most. The tagged
birds ultimately established at wintering grounds located along the border of Mauritania with Mali and Senegal, a distance
of nearly 3000 km from the breeding sites. These sites are situated within a small range of latitudes (14° and 17°N), although
distributed over a wider range of longitudes (−15°E and −4°E), with some birds occupying sites more than 1000 km apart. The
distance covered in 1 day during the migration ranged between 93 and 219 km, with peaks of traveling speed of up to 65 km/h.
Harriers were recorded traveling only during daytime, covering the longest distances in the late afternoon, suggesting that
they are daytime migrants. Most of the distance was covered between 1500 and 2000 hours, and no traveling was recorded between
2000 and 0500 hours. During migration, harriers flew close to the ground (40–100 m on average). Improved knowledge of the
harriers’ exact wintering sites may provide insights on the problems Montagu’s harriers face during the winter, highlighting
the need to take into account what happens in both the breeding and wintering grounds to implement successful conservation
measures. 相似文献
99.
Duarte CD Tributino JL Lacerda DI Martins MV Alexandre-Moreira MS Dutra F Bechara EJ De-Paula FS Goulart MO Ferreira J Calixto JB Nunes MP Bertho AL Miranda AL Barreiro EJ Fraga CA 《Bioorganic & medicinal chemistry》2007,15(6):2421-2433
We describe herein the discovery of LASSBio-881 (3c) as a novel in vivo antinociceptive, anti-inflammatory, and in vitro antiproliferative and antioxidant compound, with a cannabinoid ligand profile. We observed that LASSBio-881 (3c) was able to bind to CB1 receptors (71% at 100microM) and also to inhibit T-cell proliferation (66% at 10microM) probably by binding to CB2 receptors, in a non-proapoptotic manner, different from anandamide (1). It was also demonstrated that LASSBio-881 (3c) had an important antioxidant profile toward free radicals (DPPH and hydroxyl), probably due to its particular redox behavior, which reflects the presence of both nitro and 3,5-di-tert-butyl-4-hydroxyphenyl sub-units, as demonstrated by cyclic voltammetry studies. In addition, we showed that these structural sub-units are essential for the observed pharmacological activity. 相似文献
100.
Di Fabio R Alvaro G Bertani B Donati D Pizzi DM Gentile G Pentassuglia G Giacobbe S Spada S Ratti E Corsi M Quartaroli M Barnaby RJ Vitulli G 《Bioorganic & medicinal chemistry letters》2007,17(5):1176-1180
Chiral tetrahydroquinoline derivatives have been prepared by an asymmetric Mannich-type condensation reaction using commercially available vinyloxyethylsilane and a N-arylimino R-(+)-t-butyl lactate ester, in the presence of a catalytic amount of metal triflates as Lewis acids. This synthetic approach gave rise to the target aldehyde intermediate in moderate facial diastereoselectivity and in high chemical yield. This efficient route enabled to scale up the synthesis of an orally bioavailable glycine antagonist showing outstanding in vivo anti-hyperalgesic activity in different animal models of sustained inflammation and chronic neuropathic pain. 相似文献