全文获取类型
收费全文 | 6192篇 |
免费 | 370篇 |
国内免费 | 33篇 |
专业分类
耳鼻咽喉 | 69篇 |
儿科学 | 151篇 |
妇产科学 | 123篇 |
基础医学 | 1041篇 |
口腔科学 | 48篇 |
临床医学 | 583篇 |
内科学 | 1373篇 |
皮肤病学 | 84篇 |
神经病学 | 718篇 |
特种医学 | 340篇 |
外科学 | 871篇 |
综合类 | 27篇 |
一般理论 | 6篇 |
预防医学 | 281篇 |
眼科学 | 83篇 |
药学 | 416篇 |
中国医学 | 6篇 |
肿瘤学 | 375篇 |
出版年
2023年 | 28篇 |
2022年 | 69篇 |
2021年 | 173篇 |
2020年 | 87篇 |
2019年 | 135篇 |
2018年 | 187篇 |
2017年 | 132篇 |
2016年 | 137篇 |
2015年 | 191篇 |
2014年 | 231篇 |
2013年 | 352篇 |
2012年 | 482篇 |
2011年 | 504篇 |
2010年 | 282篇 |
2009年 | 284篇 |
2008年 | 414篇 |
2007年 | 425篇 |
2006年 | 408篇 |
2005年 | 405篇 |
2004年 | 372篇 |
2003年 | 292篇 |
2002年 | 308篇 |
2001年 | 55篇 |
2000年 | 25篇 |
1999年 | 44篇 |
1998年 | 46篇 |
1997年 | 46篇 |
1996年 | 39篇 |
1995年 | 46篇 |
1994年 | 24篇 |
1993年 | 23篇 |
1992年 | 22篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 21篇 |
1988年 | 9篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 15篇 |
1982年 | 25篇 |
1981年 | 23篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1974年 | 9篇 |
1972年 | 14篇 |
1971年 | 6篇 |
1968年 | 7篇 |
排序方式: 共有6595条查询结果,搜索用时 800 毫秒
31.
32.
Detection of ethambutol-resistant Mycobacterium tuberculosis strains by multiplex allele-specific PCR assay targeting embB306 mutations 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mokrousov I Narvskaya O Limeschenko E Otten T Vyshnevskiy B 《Journal of clinical microbiology》2002,40(5):1617-1620
We describe a multiplex allele-specific (MAS)-PCR assay to detect simultaneously mutations in the first and third bases of the embB gene codon 306ATG. These mutations are known to confer ethambutol (EMB) resistance in the majority of clinical Mycobacterium tuberculosis isolates worldwide. The mutated bases are revealed depending on the presence or absence of the respective indicative fragments amplified from the embB306 wild-type allele. Initially optimized on purified DNA samples, the assay was tested on crude cell lysates and auramine-stained sputum slide DNA preparations with the same reproducibility and interpretability of the generated profiles in agarose gel electrophoresis. Since EMB resistance is generally linked to multiple-drug resistance (MDR), the MAS-PCR assay for EMB resistance detection can be used in clinical laboratory practice in areas with a high prevalence and a high transmission rate of MDR-EMB-resistant tuberculosis. 相似文献
33.
Mosquito densoviruses generally establish persistent infections in mosquito cell lines including the C6/36 Aedes albopictus cell line. In contrast, the closely related Haemagogus equinus densovirus (HeDNV) causes dramatic cytopathic effects in the C6/36 Aedes albopictus cell line. Infection of C6/36 cells by HeDNV causes internucleosomal fragmentation of host chromosomal DNA, changes in cellular morphology (membrane budding, apoptotic bodies), caspase activation and exposure of phosphatidylserine on the cellular membrane. This is accompanied by a higher rate of infection and more vigorous production of virus in these cells. These observations are consistent with the induction of apoptosis during infection. In contrast, expression of AeDNV proteins in C6/36 cells does not cause obvious cytopathic effects although NS1 expression causes accumulation of cells in G2 phase. C6/36 cells persistently infected with AeDNV were not protected from superinfection with HeDNV. Thus, there does not seem to be an antiviral state induced by AeDNV persistent infection. 相似文献
34.
35.
Human nm23 has been implicated in suppression of metastasis in various cancers, but the underlying mechanism of such activity has not been fully understood. Using Drosophila tracheal system as a genetic model, we examined the function of the Drosophila homolog of nm23, the awd gene, in cell migration. We show that loss of Drosophila awd results in dysregulated tracheal cell motility. This phenotype can be suppressed by reducing the dosage of the chemotactic FGF receptor (FGFR) homolog, breathless (btl), indicating that btl and awd are functionally antagonists. In addition, mutants of shi/dynamin show similar tracheal phenotypes as in awd and exacerbate those in awd mutant, suggesting defects in vesicle-mediated turnover of FGFR in the awd mutant. Consistent with this, Btl-GFP chimera expressed from a cognate btl promoter-driven system accumulate at high levels on tracheal cell membrane of awd mutants as well as in awd RNA duplex-treated cultured cells. Thus, we propose that awd regulates tracheal cell motility by modulating the FGFR levels, through a dynamin-mediated pathway. 相似文献
36.
Nicolas M. Bless Shinichiro J. Tojo Hiroko Kawarai Yasuhiro Natsume Alex B. Lentsch Vaishalee A. Padgaonkar Boris J. Czermak Hagen Schmal Hans P. Friedl Peter A. Ward 《The American journal of pathology》1998,153(4):1113-1122
Using two models of acute lung inflammatory injury in rats (intrapulmonary deposition of immunoglobulin G immune complexes and systemic activation of complement after infusion of purified cobra venom factor), we have analyzed the requirements and patterns for upregulation of lung vascular P-selectin. In the immune complex model, upregulation of P-selectin was defined by Northern and Western blot analysis of lung homogenates, by immunostaining of lung tissue, and by vascular fixation of 125I-labeled anti-P-selectin. P-selectin protein was detected by 1 hour (long before detection of mRNA) and expression was sustained for the next 7 hours, in striking contrast to the pattern of P-selectin expression in the cobra venom factor model, in which upregulation was very transient (within the 1st hour). In the immune complex model, injury and neutrophil accumulation were P-selectin dependent. Upregulation of P-selectin was dependent on an intact complement system, and the presence of blood neutrophils was susceptible to the antioxidant dimethyl sulfoxide and required C5a but not tumor necrosis factor α. In contrast, in the cobra venom factor model, upregulation of P-selectin, which is C5a dependent, was also dimethyl sulfoxide sensitive but neutrophil independent. Different mechanisms that may explain why upregulation of lung vascular P-selectin is either transient or sustained are discussed. 相似文献
37.
Ilia Frolov Vladimir Kleiner Boris Krentsel Robert Mardanov Kalyan Munshi Gennady Bukatov Vladimir Zakharov Sergey Sergeev 《Macromolecular chemistry and physics.》1993,194(8):2309-2321
In order to find out correlations between the structure of an external donor and the obtained polymer, the effects of different external donors on the activity and stereospecificity of the MgCl2/TiCl4 catalytic system in the bulk polymerization of 4-methyl-1-pentene (4MP) were carefully studied. Different silane compounds of the structure RnSi(OR')4-n (where: n = 1–3, R = alkyl/phenyl, R = alkyl) and Al(i-Bu)3 (TIBA) were used as external donors and cocatalyst, respectively. The effect of the donor/TIBA mole ratio on the activity and stereospecificity of the catalytic system was studied. Some major effects were observed for the three different external donors, namely, Me3Si(OMe), Me2Si(OMe)2, and Me3Si(OBu)3, in the 4MP polymerization process. It was observed that the effect of the external silane donor on the polymerization strongly depends upon the size of the alkoxy and hydrocarbon (alkyl/phenyl) groups which are attached to the silicon atom. A selective deactivation of the non-stereospecific centers, as well as a transformation of the non-stereospecific into isospecific centers, is assumed to occur. On the basis of the obtained results and literature data available for the propene polymerization, the concept of structural conformity between the ligand-surrounded active center and the monomer molecule was carried forward. 相似文献
38.
Elena Melenevskaya Vladimir Sgonnik Eleonora Dolinskaya Boris Erussalimsky 《Macromolecular chemistry and physics.》1978,179(11):2759-2764
The structure of the butadiene unit C4H6 in the hydrolysis products of the oligomers RMnC4H6Mm'Li and RMnC4H6Li (where R is sec-butyl, M and M' are perdeuterobutadiene or styrene) was estimated by the use of IR- and NMR-spectroscopy. The dependency of the C4H6-structure on the nature of both the preceding unit M and the attacking monomer M' was investigated. The variation of the concentration of the organolithium compounds during the oligomer synthesis on the one hand, and during their hydrolysis on the other hand, showed a dependency of the C4H6-structure on the conditions of the respective experiments. 相似文献
39.
Analysis of the allelic diversity of the mycobacterial interspersed repetitive units in Mycobacterium tuberculosis strains of the Beijing family: practical implications and evolutionary considerations 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mokrousov I Narvskaya O Limeschenko E Vyazovaya A Otten T Vyshnevskiy B 《Journal of clinical microbiology》2004,42(6):2438-2444
A study set comprised 44 Mycobacterium tuberculosis strains of the Beijing family selected for their representativeness among those previously characterized by IS6110-RFLP and spoligotyping (Northwest Russia, 1997 to 2003). In the present study, these strains were subjected to mycobacterial interspersed repetitive units (MIRU) typing to assess a discriminatory power of the 12-MIRU-loci scheme (P. Supply et al., J. Clin. Microbiol. 39:3563-3571, 2001). The 44 Russian Beijing strains were subdivided into 12 MIRU types with identical profiles: 10 unique strains and two major types shared by 10 and 24 strains. Thus, basically, two distinct sublineages appear to shape the evolution of the Beijing strains in Russia. Most of the MIRU loci were found to be (almost) monomorphic in the Russian Beijing strains; the Hunter-Gaston discriminatory index (HGDI) for all 12 loci taken together was 0.65, whereas MIRU26 (the most variable in our study) showed a moderate level of discrimination (0.49). The results were compared against all available published MIRU profiles of Beijing strains from Russia (3 strains) and other geographic areas (51 strains in total), including South Africa (38 strains), East Asia (7 strains), and the United States (4 strains). A UPGMA (unweighted pair-group method with arithmetic averages)-based tree was constructed. Interestingly, no MIRU types were shared by Russian and South African strains (the two largest samples in this analysis), whereas both major Russian types included also isolates from other locations (United States and/or East Asia). This implies the evolution of the Beijing genotype to be generally strictly clonal, although a possibility of a convergent evolution of the MIRU loci cannot be excluded. We propose a dissemination of the prevailing local Beijing clones to have started earlier in South Africa rather than in Russia since more monomorphic loci were identified in Russian samples than in South African samples (mean HGDI scores, 0.08 versus 0.17). To conclude, we suggest to use a limited number of MIRUs for preliminary subdivision of Beijing strains in Russian (loci 26 + 31), South African (10 + 26 + 39), and global settings (10 + 26 + 39). 相似文献
40.