全文获取类型
收费全文 | 4040篇 |
免费 | 366篇 |
专业分类
4406篇 |
出版年
2023年 | 21篇 |
2022年 | 42篇 |
2021年 | 76篇 |
2020年 | 46篇 |
2019年 | 90篇 |
2018年 | 90篇 |
2017年 | 77篇 |
2016年 | 155篇 |
2015年 | 191篇 |
2014年 | 211篇 |
2013年 | 257篇 |
2012年 | 256篇 |
2011年 | 229篇 |
2010年 | 160篇 |
2009年 | 170篇 |
2008年 | 175篇 |
2007年 | 172篇 |
2006年 | 184篇 |
2005年 | 178篇 |
2004年 | 168篇 |
2003年 | 152篇 |
2002年 | 140篇 |
2001年 | 114篇 |
2000年 | 124篇 |
1999年 | 83篇 |
1998年 | 60篇 |
1997年 | 59篇 |
1996年 | 39篇 |
1995年 | 35篇 |
1994年 | 37篇 |
1993年 | 42篇 |
1992年 | 68篇 |
1991年 | 51篇 |
1990年 | 56篇 |
1989年 | 46篇 |
1988年 | 47篇 |
1987年 | 43篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1975年 | 12篇 |
1968年 | 5篇 |
排序方式: 共有4406条查询结果,搜索用时 15 毫秒
71.
72.
73.
Paulo FP Pimenta Alessandra S Orfano Ana C Bahia Ana PM Duarte Claudia M Ríos-Velásquez Fabrício F Melo Felipe AC Pessoa Giselle A Oliveira Keillen MM Campos Luis Martínez Villegas Nilton Barnabé Rodrigues Rafael Nacif-Pimenta Rejane C Sim?es Wuelton M Monteiro Rogerio Amino Yara M Traub-Cseko José BP Lima Maria GV Barbosa Marcus VG Lacerda Wanderli P Tadei Nágila FC Secundino 《Memórias do Instituto Oswaldo Cruz》2015,110(1):23-47
In the Americas, areas with a high risk of malaria transmission are mainly located in
the Amazon Forest, which extends across nine countries. One keystone step to
understanding the Plasmodium life cycle in Anopheles species from the Amazon Region
is to obtain experimentally infected mosquito vectors. Several attempts to colonise
Ano- pheles species have been conducted, but with only short-lived success or no
success at all. In this review, we review the literature on malaria transmission from
the perspective of its Amazon vectors. Currently, it is possible to develop
experimental Plasmodium vivax infection of the colonised and field-captured vectors
in laboratories located close to Amazonian endemic areas. We are also reviewing
studies related to the immune response to P. vivax infection of Anopheles aquasalis,
a coastal mosquito species. Finally, we discuss the importance of the modulation of
Plasmodium infection by the vector microbiota and also consider the anopheline
genomes. The establishment of experimental mosquito infections with Plasmodium
falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide
interesting models for studying malaria in the Amazonian scenario is important.
Understanding the molecular mechanisms involved in the development of the parasites
in New World vectors is crucial in order to better determine the interaction process
and vectorial competence. 相似文献
74.
Felipe Couñago Ana Aurora Díaz Gavela Gemma Sancho Irene Ortiz Francisco José Marcos Manuel Recio Julio Fernández Raquel Cano Mar Jiménez Israel J. Thuissard David Sanz-Rosa Juan Castro Nováis Eduardo Pardo Yolanda Molina Hugo Pérez García Elia del Cerro 《Reports of Practical Oncology and Radiotherapy》2019,24(5):472-480
AimTo analyse the efficacy and toxicity of postprostatectomy SRT in patients with a BCR evaluated with mpMRI.BackgroundMultiparametric magnetic resonance imaging (mpMRI) has the ability to detect the site of pelvic recurrence in patients with biochemical recurrence (BCR) after radical prostatectomy (RP). However, we do not know the oncological outcomes of mpMRI-guided savage radiotherapy (SRT).ResultsLocal, lymph node, and pelvic bone recurrence was observed in 13, 4 and 2 patients, respectively. PSA levels were significantly lower in patients with negative mpMRI (0.4 ng/mL [0.4]) vs. positive mpMRI (2.2 ng/mL [4.1], p = 0.003). Median planning target volume doses in patients with visible vs. non-visible recurrences were 76 Gy vs. 70 Gy. Overall, mean follow-up was 41 months (6–81). Biochemical relapse-free survival (bRFS) at 3 years was 82.3% and 82.5%, respectively, for the negative and positive mpMRI groups (p = 0.800). Three-year rates of late grade ≥2 urinary and rectal toxicity were 14.8% and 1.9%, respectively; all but one patient recovered without sequelae.ConclusionSRT to the macroscopic recurrence identified by mpMRI is a feasible and well-tolerated option. In this study, there were no differences in bRFS between MRI-positive and MRI-negative patients, indicating effective targeting of MRI-positive lesions. 相似文献
75.
We have previously described a novel cancer chemotherapeutic approach based on the induction of apoptosis in targeted cells by homing pro-apoptotic peptides. In order to improve this approach we developed a computational method (approach for detecting potential apoptotic peptides, APAP) to detect short PAPs, based on the prediction of the helical content of peptides, the hydrophobic moment, and the isoelectric point. PAPs are toxic against bacteria and mitochondria, but not against mammalian cells when applied extracellularly. Among other peptides, substance P was identified as a PAP and subsequently demonstrated to be a pro-apoptotic peptide experimentally. APAP thus provides a method to detect and ultimately improve pro-apoptotic peptides for chemotherapy. 相似文献
76.
77.
Patrick Jung Michael Schermer Laura Briegel‐Williams Karen Baumann Peter Leinweber Ulf Karsten Lukas Lehnert Sebastian Achilles Jrg Bendix Burkhard Büdel 《Journal of phycology》2019,55(6):1306-1318
In the Atacama Desert, cyanobacteria grow on various substrates such as soils (edaphic) and quartz or granitoid stones (lithic). Both edaphic and lithic cyanobacterial communities have been described but no comparison between both communities of the same locality has yet been undertaken. In the present study, we compared both cyanobacterial communities along a precipitation gradient ranging from the arid National Park Pan de Azúcar (PA), which resembles a large fog oasis in the Atacama Desert extending to the semiarid Santa Gracia Natural Reserve (SG) further south, as well as along a precipitation gradient within PA. Various microscopic techniques, as well as culturing and partial 16S rRNA sequencing, were applied to identify 21 cyanobacterial species; the diversity was found to decline as precipitation levels decreased. Additionally, under increasing xeric stress, lithic community species composition showed higher divergence from the surrounding edaphic community, resulting in indigenous hypolithic and chasmoendolithic cyanobacterial communities. We conclude that rain and fog water, respectively, cause contrasting trends regarding cyanobacterial species richness in the edaphic and lithic microhabitats. 相似文献
78.
Fachuang Lu Steven D. Karlen Bronwen G. Smith Philip J. Harris José Carlos del Río John Ralph 《The Plant journal : for cell and molecular biology》2016,88(6):1046-1057
Tricin [5,7‐dihydroxy‐2‐(4‐hydroxy‐3,5‐dimethoxyphenyl)‐4H‐chromen‐4‐one], a flavone, was recently established as an authentic monomer in grass lignification that likely functions as a nucleation site. It is linked onto lignin as an aryl alkyl ether by radical coupling with monolignols or their acylated analogs. However, the level of tricin that incorporates into lignin remains unclear. Herein, three lignin characterization methods: acidolysis; thioacidolysis; and derivatization followed by reductive cleavage; were applied to quantitatively assess the amount of lignin‐integrated tricin. Their efficiencies at cleaving the tricin‐(4′–O–β)‐ether bonds and the degradation of tricin under the corresponding reaction conditions were evaluated. A hexadeuterated tricin analog was synthesized as an internal standard for accurate quantitation purposes. Thioacidolysis proved to be the most efficient method, liberating more than 91% of the tricin with little degradation. A survey of different seed‐plant species for the occurrence and content of tricin showed that it is widely distributed in the lignin from species in the family Poaceae (order Poales). Tricin occurs at low levels in some commelinid monocotyledon families outside the Poaceae, such as the Arecaceae (the palms, order Arecales) and Bromeliaceae (Poales), and the non‐commelinid monocotyledon family Orchidaceae (Orchidales). One eudicotyledon was found to have tricin (Medicago sativa, Fabaceae). The content of lignin‐integrated tricin is much higher than the extractable tricin level in all cases. Lignins, including waste lignin streams from biomass processing, could therefore provide a large and alternative source of this valuable flavone, reducing the costs, and encouraging studies into its application beyond its current roles. 相似文献
79.
Purpose
Cardiovascular responses of traditional resistance (TS) training have been extensively explored. However, the fatigue mechanisms associated with an intra-set rest configuration (ISR) have not been investigated. This study compares two modalities of set configurations for resistance exercise that equates work to rest ratios and measures the central and peripheral fatigue in combination with cortical, hemodynamic and cardiovascular measures.Methods
11 subjects performed two isometric knee extension training sessions using TS and ISR configurations. Voluntary activation (VA), single twitch amplitude, low frequency fatigue (LFF), Mwave, motor evoked potential (MEP), short intracortical inhibition (SICI), intracortical facilitation (ICF) and heart rate variability were evaluated before and after each training session. During each session beat to beat heart rate, blood pressure and rate pressure product (RPP) were also evaluated.Results
After exercise VA decreased significantly for TS but not for ISR (P < 0.001), single twitch amplitude and LFF values were lower for TS than ISR (P < 0.004), and SICI was reduced only for the TS configuration (P = 0.049). During exercise RPP values were significantly higher for the TS than for ISR (P = 0.001). RPP correlated with VA for TS (r = -.85 P < 0.001) suggesting a relationship between central fatigue and cardiovascular stress.Conclusions
We conclude that ISR induced lower central and peripheral fatigue as well as lower cardiovascular stress in comparison with TS configuration. Our study suggests that set configuration is a key factor in the regulation of the neuromuscular and cardiovascular responses of resistance training. 相似文献80.
Juan Ortín Concepción Martínez Lucía del Río Mercedes Dávila Cecilio López-Galíndez Nieves Villanueva Esteban Domingo 《Gene》1983,23(2):233-239
The complete genetic information contained in the influenza virus RNA segment 7 of the A/Bangkok/ (H3N2) strain has been cloned by in vitro synthesis of the complementary dsDNA and its insertion into plasmid pBR322. The nucleotide sequence of the viral RNA segment has been determined from the cDNA insert. It is 1027 nucleotides long, and contains two open reading frames, as shown for other influenza virus strains. When compared with the previously published sequence for the A/Udorn/72 (H3N2) strain, 15 nucleotide exchanges are observed, most of them silent mutations, and only two causing amino acid changes in each of the M1 and M2 protein sequences. 相似文献