全文获取类型
收费全文 | 14782篇 |
免费 | 981篇 |
国内免费 | 91篇 |
专业分类
耳鼻咽喉 | 124篇 |
儿科学 | 495篇 |
妇产科学 | 347篇 |
基础医学 | 2149篇 |
口腔科学 | 250篇 |
临床医学 | 1311篇 |
内科学 | 3615篇 |
皮肤病学 | 448篇 |
神经病学 | 1559篇 |
特种医学 | 308篇 |
外科学 | 1307篇 |
综合类 | 41篇 |
一般理论 | 7篇 |
预防医学 | 1259篇 |
眼科学 | 278篇 |
药学 | 1132篇 |
中国医学 | 40篇 |
肿瘤学 | 1184篇 |
出版年
2024年 | 23篇 |
2023年 | 202篇 |
2022年 | 509篇 |
2021年 | 857篇 |
2020年 | 406篇 |
2019年 | 613篇 |
2018年 | 671篇 |
2017年 | 413篇 |
2016年 | 479篇 |
2015年 | 561篇 |
2014年 | 706篇 |
2013年 | 924篇 |
2012年 | 1291篇 |
2011年 | 1280篇 |
2010年 | 765篇 |
2009年 | 591篇 |
2008年 | 914篇 |
2007年 | 894篇 |
2006年 | 792篇 |
2005年 | 718篇 |
2004年 | 587篇 |
2003年 | 516篇 |
2002年 | 475篇 |
2001年 | 63篇 |
2000年 | 38篇 |
1999年 | 69篇 |
1998年 | 85篇 |
1997年 | 77篇 |
1996年 | 42篇 |
1995年 | 31篇 |
1994年 | 32篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1977年 | 9篇 |
1975年 | 5篇 |
1974年 | 10篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Recent research has shown that pseudowords created by transposing letters are very effective for activating the lexical representation of their base words (e.g., relovution activates REVOLUTION). Furthermore, pseudoword transpositions of consonants are more similar to their corresponding base words than the transposition of vowels. We report one experiment using pseudowords created by the transposition of two consonants, two vowels, and their corresponding control conditions (i.e., the replacement of two consonants or two vowels) in a lexical decision task while Event Related Potentials (ERPs) were recorded. The results showed a modulation of the amplitude of the N400 component as a function of the type of pseudoword (transposed-letter versus replacement letter pseudowords), and this modulation was different for transposed consonants and vowels. These results suggest that consonants and vowels play a different role during word processing. 相似文献
42.
Thi Thu Ha Hoang Carina Bengtsson Dac Cam Phung Mikael Srberg Marta Granstrm 《Clinical and Vaccine Immunology : CVI》2005,12(1):81-85
Helicobacter pylori-associated diseases, such as peptic ulcer and gastric cancer, are common in Vietnam, but the prevalence of the infection is largely unknown. A validated enzyme-linked immunosorbent assay was used for seroepidemiology with 971 samples from the general population, ages 0 to 88 years, with 546 samples from an urban population (Hanoi), and with 425 samples from a poor, rural province (Hatay). The overall seroprevalence of the infection was 746 per 1,000, with a prevalence of 788 per 1,000 in Hanoi and 692 per 1,000 in Hatay (P = 0.0007). The risk for infection in the rural area of Hatay was 40% lower than in the urban population of Hanoi, with the odds ratio being 0.59 (95% confidence interval, 0.43 to 0.81). The study shows that the prevalence of H. pylori infection is high in Vietnam and especially high in a large urban area, such as the city of Hanoi. 相似文献
43.
Distribution of putative adhesins in different seropathotypes of Shiga toxin-producing Escherichia coli
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)
Toma C Martínez Espinosa E Song T Miliwebsky E Chinen I Iyoda S Iwanaga M Rivas M 《Journal of clinical microbiology》2004,42(11):4937-4946
The distribution of eight putative adhesins that are not encoded in the locus for enterocyte effacement (LEE) in 139 Shiga toxin-producing Escherichia coli (STEC) of different serotypes was investigated by PCR. Five of the adhesins (Iha, Efa1, LPF(O157/OI-141), LPF(O157/OI-154), and LPF(O113)) are encoded in regions corresponding to genomic O islands of E. coli EDL933, while the other three adhesins have been reported to be encoded in the STEC megaplasmid of various serotypes (ToxB [O157:H7], Saa [O113:H21], and Sfp [O157:NM]). STEC strains were isolated from humans (n = 54), animals (n = 52), and food (n = 33). They were classified into five seropathotypes (A through E) based on the reported occurrence of STEC serotypes in human disease, in outbreaks, and in the hemolytic-uremic syndrome (M. A. Karmali, M. Mascarenhas, S. Shen, K. Ziebell, S. Johnson, R. Reid-Smith, J. Isaac-Renton, C. Clark, K. Rahn, and J. B. Kaper, J. Clin. Microbiol. 41:4930-4940, 2003). The most prevalent adhesin was that encoded by the iha gene (91%; 127 of 139 strains), which was distributed in all seropathotypes. toxB and efa1 were present mainly in strains of seropathotypes A and B, which were LEE positive. saa was present only in strains of seropathotypes C, D, and E, which were LEE negative. Two fimbrial genes, lpfA(O157/OI-141) and lpfA(O157/OI-154), were strongly associated with seropathotype A. The fimbrial gene lpfA(O113) was present in all seropathotypes except for seropathotype A, while sfpA was not present in any of the strains studied. The distribution of STEC adhesins depends mainly on serotypes and not on the source of isolation. Seropathotype A, which is associated with severe disease and frequently is involved in outbreaks, possesses a unique adhesin profile which is not present in the other seropathotypes. The wide distribution of iha in STEC strains suggested that it could be a candidate for vaccine development. 相似文献
44.
Elizabeth M Genega Malathy Kapali Marta Torres-Quinones William C Huang Jill S Knauss Li-Ping Wang Puthiyaveettil N Raghunath Christopher Kozlowski Stanley Bruce Malkowicz John E Tomaszewski 《Modern pathology》2005,18(1):11-18
The classification of urothelial neoplasms of the kidney traditionally has been similar to that of urinary bladder tumors. Several years ago, the classification of papillary urothelial neoplasms was revised. The current study focuses on the application of the 1998 World Health Organization (WHO)/International Society of Urological Pathology classification system to 102 renal pelvic urothelial neoplasms and compares it to the 1973 WHO classification scheme. In this study, all tumors were classified as urothelial carcinomas, and the majority (85%) were papillary. Most patients with papillary tumors presented with 'superficial' disease (< or = pT1). With the 1998 system, most papillary carcinomas were high grade, and were more often invasive as compared to low-grade tumors. Only 34% were low-grade papillary tumors and, of these, most (93%) were noninvasive. With the 1973 system, most papillary tumors were grade 2 or 3, with invasion more common in grade 3 tumors. By 1973 criteria, grade 2 tumors were a heterogeneous group; with 1998 criteria, nearly one-half were high grade and the other half low grade. The grade of papillary urothelial carcinomas with both the 1973 and 1998 grading methods was associated with stage (P=0.001). Our study reveals that papillomas and papillary urothelial neoplasms of low malignant potential are uncommon tumors in the kidney. Renal pelvic papillary urothelial neoplasms are most often carcinomas and are more commonly high grade than low grade. Although both the 1973 and 1998 systems showed a significant association with tumor stage, grade 2 papillary carcinomas are a heterogeneous group by 1973 criteria. The 1998 system provides useful information in that it more clearly defines a papillary tumor's grade and selects for a group of tumors, namely low-grade papillary urothelial carcinomas, for which a low likelihood of invasion can be predicted. 相似文献
45.
Cryptococcus neoformans, an encapsulated yeast, is a common cause of life-threatening meningoencephalitis in immunosuppressed patients. We previously observed that administration of a monoclonal antibody (MAb) to the capsular polysaccharide to mice with pulmonary infection prolonged survival and enhanced granulomatous inflammation without reducing lung CFU. To understand the mechanism of MAb action, we studied leukocyte recruitment and cytokine profiles in lungs of A/JCr mice. B lymphocytes were the predominant cell type in lung infiltrates, comprising 15 to 30% of the leukocytes. Despite alterations in histological appearance, fluorescence-activated cell sorter analysis revealed no significant difference in total numbers of lung leukocytes in MAb-treated mice and controls. Differences in the immune response to C. neoformans between MAb-treated mice and controls included (i) an increase in the percentage of granulocytes among lung leukocytes on day 14, (ii) higher macrophage surface expression of CD86 on day 28, (iii) larger amounts of IL-10 in lung homogenates at day 7, (iv) a trend toward smaller amounts of gamma interferon mRNA and protein on day 7, and (v) a smaller increase in the levels of interleukin-4 mRNA and protein on day 7. Hence, the immune responses to C. neoformans infection in the presence and absence of specific antibody were qualitatively similar, and antibody administration was associated with several subtle quantitative differences in immune response parameters that could translate into enhanced survival. MAb may function partly by down-regulating the inflammatory response and reducing host damage. Our findings demonstrate unexpected complexity in the interaction between specific MAb and other components of the host immune response. 相似文献
46.
Alberto Utrero-Rico Javier Ruiz-Hornillos Cecilia González-Cuadrado Claudia Geraldine Rita Berta Almoguera Pablo Minguez Antonio Herrero-González Mario Fernández-Ruiz Octavio Carretero Juan Carlos Taracido-Fernández Rosario López-Rodriguez Marta Corton José María Aguado Luisa María Villar Carmen Ayuso-García Estela Paz-Artal Rocio Laguna-Goya 《The Journal of allergy and clinical immunology》2021,147(5):1652-1661.e1
47.
Marta L. Tamayo Cesar Maldonado Silvia L. Plaza Gustavo M. Alvira Gustavo E. Tamayo Marta Zambrano Jaime L. Frias Jaime E. Bernal 《Clinical genetics》1996,50(3):126-132
We describe the neurological evaluation and MRI analysis of 30 patients, belonging to 16 families with Usher syndrome (US) type I and type II (US1 and US2). In addition to the classic visual and audiological abnormalities seen in these patients, we observed abnormal gait in 88.9% of US1 and in 66.7% of US2 patients and abnormal coordination in 33.4% of US1, and in 58.3% of US2. Borderline mental retardation, depression or bipolar affective disorder were observed in 16.7% of US1 and 33.3% of US2 patients. MRI analysis showed cerebellar abnormalities in 50% of US 1 and 75% of US2 patients, but no clear correlation was observed between structural abnormalities and clinical findings. A pattern for the MRI classification of US patients is suggested. 相似文献
48.
Epitope of the vaccine-type Bordetella pertussis strain 186 lipooligosaccharide and antiendotoxin activity of antibodies directed against the terminal pentasaccharide-tetanus toxoid conjugate
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Niedziela T Letowska I Lukasiewicz J Kaszowska M Czarnecka A Kenne L Lugowski C 《Infection and immunity》2005,73(11):7381-7389
Lipooligosaccharides (LOS) isolated from Bordetella pertussis strains 186 and 606 were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-resolution magic angle spinning nuclear magnetic resonance (NMR). These analyses distinguished between the LOS of strains 186 and 606, suggesting that the structure of LOS in B. pertussis is heterogeneous. The pentasaccharide was selectively cleaved from LOS of B. pertussis strain 186, purified, and covalently linked to a monomer fraction of tetanus toxoid. Injection of rabbits with the neoglycoconjugate emulsified in complete Freund's adjuvant yielded immunoglobulin G antibodies that were reactive with the LOS. These antibodies reacted strongly with B. pertussis LOS possessing the complete dodecasaccharide, as determined by an enzyme-linked immunosorbent assay, immunoblotting, and flow cytometry with intact, live bacterial cells. The binding epitope within the pentasaccharide was investigated by saturation transfer difference (STD) NMR spectroscopy. Protons H-1 and H-4 of the terminal alpha-D-GlcpNAc and proton H-6 and protons of an N-methyl group at H-4 of 3-substituted beta-L-FucpNAc4NMe exhibited the largest saturation transfers. STD NMR experiments confirmed that the immunodominant epitope recognized by the antineoglycoconjugate antibodies is located predominantly in the distal trisaccharide of B. pertussis 186 LOS. The antipentasaccharide antibodies induced by the conjugate inhibited the secretion of tumor necrosis factor alpha, interleukin-6, and NO by LOS-stimulated J774A.1 cells. 相似文献
49.
Premature senescence involving p53 and p16 is activated in response to constitutive MEK/MAPK mitogenic signaling 总被引:35,自引:2,他引:35
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)
Athena W. Lin Marta Barradas James C. Stone Linda van Aelst Manuel Serrano Scott W. Lowe 《Genes & development》1998,12(19):3008-3019
Oncogenic Ras transforms immortal rodent cells to a tumorigenic state, in part, by constitutively transmitting mitogenic signals through the mitogen-activated protein kinase (MAPK) cascade. In primary cells, Ras is initially mitogenic but eventually induces premature senescence involving the p53 and p16INK4a tumor suppressors. Constitutive activation of MEK (a component of the MAPK cascade) induces both p53 and p16, and is required for Ras-induced senescence of normal human fibroblasts. Furthermore, activated MEK permanently arrests primary murine fibroblasts but forces uncontrolled mitogenesis and transformation in cells lacking either p53 or INK4a. The precisely opposite response of normal and immortalized cells to constitutive activation of the MAPK cascade implies that premature senescence acts as a fail-safe mechanism to limit the transforming potential of excessive Ras mitogenic signaling. Consequently, constitutive MAPK signaling activates p53 and p16 as tumor suppressors. 相似文献
50.
Moreno Sabater A Moreno M Moreno FJ Eguiluz C van Rooijen N Benito A 《Parasitology research》2005,95(2):97-105
The main objective of this study was to determine whether a chemical immunomodulation protocol could reduce the resistance of NOD/LtSz-SCID mice to Plasmodium falciparum infection and provide an improved mouse model for screening the antimalarial activity of new compounds. This model was compared with the presently used immunodeficient Beige/Nude/Xid (BNX) mouse model, using the same protocol, in terms of percentage of infected mice, parasite development, leukocyte response and phagocytosis of P. falciparum infected cells in various organs. Our results show that the combination of the chemical immune modulation protocol with the genetic background of NOD/LtSz-SCID mice results in the development of long-lasting P. falciparum infection in a high percentage of mice. A comparison of the results obtained in the histological study for both mouse models suggests that the higher rate of success in NOD/LtSz-SCID mice could be related to the reduced macrophage recruitment developed in different tissues to remove the parasite from blood. 相似文献