全文获取类型
收费全文 | 213060篇 |
免费 | 3944篇 |
国内免费 | 120篇 |
专业分类
耳鼻咽喉 | 1499篇 |
儿科学 | 7658篇 |
妇产科学 | 3707篇 |
基础医学 | 22001篇 |
口腔科学 | 2183篇 |
临床医学 | 16374篇 |
内科学 | 38937篇 |
皮肤病学 | 1448篇 |
神经病学 | 20273篇 |
特种医学 | 10361篇 |
外国民族医学 | 11篇 |
外科学 | 33907篇 |
综合类 | 2756篇 |
一般理论 | 31篇 |
预防医学 | 21052篇 |
眼科学 | 3486篇 |
药学 | 12065篇 |
中国医学 | 718篇 |
肿瘤学 | 18657篇 |
出版年
2023年 | 316篇 |
2022年 | 516篇 |
2021年 | 997篇 |
2020年 | 695篇 |
2019年 | 924篇 |
2018年 | 22892篇 |
2017年 | 18104篇 |
2016年 | 20353篇 |
2015年 | 1925篇 |
2014年 | 2196篇 |
2013年 | 2496篇 |
2012年 | 9637篇 |
2011年 | 23690篇 |
2010年 | 20280篇 |
2009年 | 12771篇 |
2008年 | 21488篇 |
2007年 | 23844篇 |
2006年 | 2724篇 |
2005年 | 4118篇 |
2004年 | 5214篇 |
2003年 | 5892篇 |
2002年 | 3921篇 |
2001年 | 916篇 |
2000年 | 1067篇 |
1999年 | 765篇 |
1998年 | 543篇 |
1997年 | 477篇 |
1996年 | 356篇 |
1995年 | 334篇 |
1994年 | 293篇 |
1993年 | 227篇 |
1992年 | 397篇 |
1991年 | 434篇 |
1990年 | 477篇 |
1989年 | 364篇 |
1988年 | 341篇 |
1987年 | 359篇 |
1986年 | 341篇 |
1985年 | 338篇 |
1984年 | 271篇 |
1983年 | 226篇 |
1982年 | 169篇 |
1980年 | 169篇 |
1979年 | 275篇 |
1978年 | 187篇 |
1977年 | 161篇 |
1976年 | 149篇 |
1975年 | 140篇 |
1974年 | 172篇 |
1973年 | 154篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Ana J. Alarcos Jorge A. Etchegoin Florencia Cremonte 《Acta parasitologica / Witold Stefański Institute of Parasitology, Warszawa, Poland》2008,53(4):365-368
In this paper Steringotrema microacetabularis (Suriano et Martorelli, 1983) is redescribed and transferred to Bacciger Nicoll, 1924 in the Faustulidae Poche, 1926 based on newly collected material from the type-host, Paralichthys orbignyanus Valenciennes, 1839 and the type-locality, Mar Chiquita coastal lagoon, Buenos Aires Province, Argentina. A careful re-examination
of the new specimens shows that some anatomical characteristics were ignored or incompletely described by the previous authors
and they are included herein. The species is tentatively transferred to Bacciger with which it appears to have closest affinity. Despite the anatomical differences detailed in this paper, confirmation of
this proposal must await further work, including molecular studies. 相似文献
993.
Sunil Tomar Varsha Ganesan Ankit Sharma Chang Zeng Lisa Waggoner Andrew Smith Chang H. Kim Paula Licona-Limón Richard L. Reinhardt Richard A. Flavell Yui-Hsi Wang Simon P. Hogan 《The Journal of allergy and clinical immunology》2021,147(1):280-295
- Download : Download high-res image (233KB)
- Download : Download full-size image
994.
Chon D Simon BA Beck KC Shikata H Saba OI Won C Hoffman EA 《Respiratory physiology & neurobiology》2005,148(1-2):65-83
Xenon-enhanced computed tomography (Xe-CT) has been used to measure regional ventilation by determining the wash-in (WI) and wash-out (WO) rates of stable Xe. We tested the common assumption that WI and WO rates are equal by measuring WO-WI in different anatomic lung regions of six anesthetized, supine sheep scanned using multi-detector-row computed tomography (MDCT). We further investigated the effect of tidal volume, image gating (end-expiratory EE versus end-inspiratory EI), local perfusion, and inspired Xe concentration on this phenomenon. RESULTS: WO time constant was greater than WI in all lung regions, with the greatest differences observed in dependent base regions. WO-WI time constant difference was greater during EE imaging, smaller tidal volumes, and with higher Xe concentrations. Regional perfusion did not correlate with WI-WO. We conclude that Xe-WI rate can be significantly different from the WO rate, and the data suggest that this effect may be due to a combination of anatomic and fluid mechanical factors such as Rayleigh-Taylor instabilities set up at interfaces between two gases of different densities. 相似文献
995.
The plasminogen activation system reduces fibrosis in the lung by a hepatocyte growth factor-dependent mechanism 总被引:12,自引:0,他引:12
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hattori N Mizuno S Yoshida Y Chin K Mishima M Sisson TH Simon RH Nakamura T Miyake M 《The American journal of pathology》2004,164(3):1091-1098
Mice deficient in the plasminogen activator inhibitor-1 gene (PAI-1-/- mice) are relatively protected from developing pulmonary fibrosis from bleomycin administration. We hypothesized that one of the protective mechanisms may be the ability of the plasminogen system to enhance hepatocyte growth factor (HGF) effects, which have been reported to be anti-fibrotic in the lung. HGF is known to be sequestered in tissues by binding to extracellular matrix components. Following bleomycin administration, we found that HGF protein levels were higher in bronchoalveolar lavage fluid from PAI-1-/- mice compared to wild-type (PAI-1+/+) mice. This increase could be suppressed by administering tranexamic acid, which inhibits plasmin activity. Conversely, intratracheal instillation of urokinase into bleomycin-injured PAI-1+/+ mice to activate plasminogen caused a significant increase in HGF within bronchoalveolar lavage and caused less collagen accumulation in the lungs. Administration of an anti-HGF neutralizing antibody markedly increased collagen accumulation in the lungs of bleomycin-injured PAI-1-/- mice. These results support the hypothesis that increasing the availability of HGF, possibly by enhancing its release from extracellular matrix by a plasmin-dependent mechanism, is an important means by which activation of the plasminogen system can limit pulmonary fibrosis. 相似文献
996.
Detection of HIV-1 antiretroviral resistance from patients with persistently low but detectable viraemia 总被引:3,自引:0,他引:3
We modified the Abbott diagnostics HIV-1 Viroseq version 2 assay trade mark in order to detect the presence of HIV-1 drug resistance mutations in patients with viraemia below 1000 copies/ml of plasma. One hundred and forty-four patients with a detectable HIV-1 plasma viral load below 1000 copies/ml were selected and HIV-1 genetic analysis carried out using a modification of the Abbott Diagnostics Viroseq 2.0 assay trade mark. The procedure differs from the standard protocol in that a nested PCR amplification step was introduced. The oligonucleotide primers for the first round of PCR were those supplied in the RT-PCR module of the kit. The nested PCR primers were primers A and H taken from the sequencing module. One hundred and twenty-eight out of 144 (89%) plasma samples with an HIV-1 viral load of less than 1000 copies/ml (ranging from 54 to 992 copies) were successfully sequenced. HIV-1 genotypes were obtained from 68 out of 81 (84%) samples with a viral load of greater than 50 but less than 300 copies/ml and 60/63 (95%) of samples with a viral load of greater than 300 but less than 1000 copies/ml. Serial dilution of a sample with a high viral load did not affect the detection of resistance mutations. Multiple sequencing of samples with low viral load did not result in detection of additional mutations, although, in one sample the K103N mutation was detected in 3/6 replicates while wild-type was detected in 2/6 and a mixture of wild-type/mutant in 1/6. Samples from patients infected with both clade B and non-B clades of HIV-1 could be genotyped at low copy number. Modification of the Abbott Viroseq assay allows reproducible sequencing of the HIV-1 genome from patients with low, but detectable, plasma virus burden. 相似文献
997.
Charles R. Bursey Stephen R. Goldberg Fred Kraus 《Acta parasitologica / Witold Stefański Institute of Parasitology, Warszawa, Poland》2007,52(2):142-145
Falcaustra papuensis sp. nov. (Ascaridida, Kathlaniidae) from the large intestine of Sphenomorphus simus (Squamata, Sciencidae) is described and illustrated. Falcaustra papuensis represents the 4th Australo-Papuan species assigned to this genus and is distinguished from other Australo-Papuan species
by the distribution pattern of caudal papillae (6 precloacal, 6 adcloacal, 8 postcloacal, and 1 median), length of spicules
(561–714 μm) and presence of a pseudosucker. Sphenomorphus simus was found to harbor 2 additional species of nematodes, Meteterakis crombiei and Oswaldocruzia bakeri. Sphenomorphus simus represents a new host record for each of these nematode species. 相似文献
998.
Anthony J Sharp Paul E Polak Vittoria Simonini Shao X Lin Jill C Richardson Ernesto R Bongarzone Douglas L Feinstein 《Journal of neuroinflammation》2008,5(1):33
Background
The purinergic receptor P2x7 is expressed on myeloid cells as well as on CNS glial cells, and P2x7 activation has been shown to increase both glial and T-cell activation. These properties suggest a role in the development of autoimmune disease including multiple sclerosis. 相似文献999.
Proapoptotic Bak is sequestered by Mcl-1 and Bcl-xL, but not Bcl-2, until displaced by BH3-only proteins 总被引:30,自引:0,他引:30
下载免费PDF全文
![点击此处可从《Genes & development》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Willis SN Chen L Dewson G Wei A Naik E Fletcher JI Adams JM Huang DC 《Genes & development》2005,19(11):1294-1305
Commitment of cells to apoptosis is governed largely by the interaction between members of the Bcl-2 protein family. Its three subfamilies have distinct roles: The BH3-only proteins trigger apoptosis by binding via their BH3 domain to prosurvival relatives, while the proapoptotic Bax and Bak have an essential downstream role involving permeabilization of organellar membranes and induction of caspase activation. We have investigated the regulation of Bak and find that, in healthy cells, Bak associates with Mcl-1 and Bcl-x(L) but surprisingly not Bcl-2, Bcl-w, or A1. These interactions require the Bak BH3 domain, which is also necessary for Bak dimerization and killing activity. When cytotoxic signals activate BH3-only proteins that can engage both Mcl-1 and Bcl-x(L) (such as Noxa plus Bad), Bak is displaced and induces cell death. Accordingly, the BH3-only protein Noxa could bind to Mcl-1, displace Bak, and promote Mcl-1 degradation, but Bak-mediated cell death also required neutralization of Bcl-x(L) by other BH3-only proteins. The results indicate that Bak is held in check solely by Mcl-1 and Bcl-x(L) and induces apoptosis only if freed from both. The finding that different prosurvival proteins have selective roles has notable implications for the design of anti-cancer drugs that target the Bcl-2 family. 相似文献
1000.
Alicja Gryczyńska-Siemiątkowska Alicja Siedlecka Joanna Stańczak Miłosława Barkowska 《Acta parasitologica / Witold Stefański Institute of Parasitology, Warszawa, Poland》2007,52(2):165-170
Sand lizards (Lacerta agilis) were trapped and examined for ticks from May to September in 2002 and 2003 in Northeastern Poland. A total of 233 Ixodes ricinus (L.) ticks (76 larvae and 157 nymphs) was found on 31 of 235 captured lizards (13.2%). The tick infestation is relatively
low compared to that of mammals and passerine birds from the same area (Siński et al. 2006, Gryczyńska et al. 2002). Tick infestation depended on the month of capture, being the highest in spring. In autumn no ticks were recorded on
any of the captured lizards. The oldest lizards carried the highest number of ticks but no differences related to sex of the
host were found. All the collected ticks were analysed by PCR for the presence of Borrelia burgdorferi sensu lato, the etiological agents of Lyme disease. Spirochetes were detected in 11 out of 233 (4.7%) ticks tested. Genetic
analysis confirmed that the spirochetes are members of the Borrelia afzelii, B. garinii and B. burgdorferi sensu stricto genospecies. Mixed infection were not detected. The prevalence of infection was analysed in relation to months
of the capture, age and sex of the lizards, but differences were not statistically significant. The obtained results suggest
that lizards are probably not B. burgdorferi reservoirs, but further studies are required to confirm this. 相似文献