全文获取类型
收费全文 | 8311篇 |
免费 | 441篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 97篇 |
儿科学 | 342篇 |
妇产科学 | 97篇 |
基础医学 | 844篇 |
口腔科学 | 175篇 |
临床医学 | 635篇 |
内科学 | 2111篇 |
皮肤病学 | 126篇 |
神经病学 | 562篇 |
特种医学 | 388篇 |
外科学 | 1348篇 |
综合类 | 127篇 |
一般理论 | 6篇 |
预防医学 | 433篇 |
眼科学 | 282篇 |
药学 | 628篇 |
中国医学 | 21篇 |
肿瘤学 | 565篇 |
出版年
2024年 | 3篇 |
2023年 | 56篇 |
2022年 | 120篇 |
2021年 | 241篇 |
2020年 | 164篇 |
2019年 | 184篇 |
2018年 | 233篇 |
2017年 | 174篇 |
2016年 | 224篇 |
2015年 | 230篇 |
2014年 | 358篇 |
2013年 | 424篇 |
2012年 | 706篇 |
2011年 | 743篇 |
2010年 | 419篇 |
2009年 | 345篇 |
2008年 | 544篇 |
2007年 | 615篇 |
2006年 | 565篇 |
2005年 | 529篇 |
2004年 | 493篇 |
2003年 | 417篇 |
2002年 | 361篇 |
2001年 | 69篇 |
2000年 | 66篇 |
1999年 | 72篇 |
1998年 | 62篇 |
1997年 | 35篇 |
1996年 | 34篇 |
1995年 | 34篇 |
1994年 | 33篇 |
1993年 | 21篇 |
1992年 | 29篇 |
1991年 | 34篇 |
1990年 | 21篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 7篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1970年 | 4篇 |
1968年 | 4篇 |
1965年 | 2篇 |
排序方式: 共有8787条查询结果,搜索用时 15 毫秒
41.
Human immune response to outer membrane protein CD of Moraxella catarrhalis in adults with chronic obstructive pulmonary disease 下载免费PDF全文
Moraxella catarrhalis is a common cause of lower respiratory tract infection in adults with chronic obstructive pulmonary disease (COPD). The antibody response to outer membrane protein (OMP) CD, a highly conserved surface protein of M. catarrhalis under consideration as a vaccine antigen, was studied in adults with COPD following 40 episodes of infection or colonization. Following infection or colonization, 9 of 40 patients developed new serum immunoglobulin G (IgG) to OMP CD, as measured by enzyme-linked immunosorbent assay. Adsorption assays revealed that a proportion of the serum IgG was directed toward surface-exposed epitopes on OMP CD in six of the nine patients who developed new IgG to OMP CD. Immunoblot assays with fusion peptide constructs indicated that the new antibodies that developed after infection or colonization recognized conformational epitopes, particularly in the carboxy region of the protein. Three of 28 patients developed new mucosal IgA to OMP CD in sputum supernatants. This study establishes that OMP CD is a target of a systemic and mucosal immune response following infection and colonization in some patients with COPD. 相似文献
42.
43.
44.
The individual leaves of a multileaf collimator (MLC) have a tongue-and-groove or stepped-edge design to minimize leakage radiation between adjacent leaves. This design element has a drawback in that it creates areas of underdosages in intensity-modulated photon beams unless a leaf trajectory is specifically designed such that for any two adjacent leaf pairs, the direct exposure under the tongue-and-groove is equal to the lower of the direct exposures of the leaf pairs. In this work, we present a systematic study of the optimization of a leaf sequencing algorithm for segmental multileaf collimator beam delivery that completely eliminates areas of underdosages due to tongue-and-groove or stepped-edge design of the MLC. Simultaneous elimination of tongue-and-groove effect and leaf interdigitation is also studied. This is an extension of our previous work (Kamath et al 2003a Phys. Med. Biol. 48 307) in which we described a leaf sequencing algorithm that is optimal for monitor unit (MU) efficiency under most common leaf movement constraints that include minimum leaf separation. Compared to our previously published algorithm (without constraints), the new algorithms increase the number of sub-fields by approximately 21% and 25%, respectively, but are optimal in MU efficiency for unidirectional schedules. 相似文献
45.
Myotonic dystrophy, a progressive autosomal dominant disorder, is associated with an expansion of a CTG repeat tract located in the 3'-untranslated region of a serine/threonine protein kinase, DMPK. DMPK modulates skeletal muscle Na channels in vitro, and thus we hypothesized that mice deficient in DMPK would have altered muscle Na channel gating. We measured macroscopic and single channel Na currents from cell-attached patches of skeletal myocytes from mice heterozygous (DMPK(+/-)) and homozygous (DMPK(-/-)) for DMPK loss. In DMPK(-/-) myocytes, Na current amplitude was reduced because of reduced channel number. Single channel recordings revealed Na channel reopenings, similar to the gating abnormality of human myotonic muscular dystrophy (DM), which resulted in a plateau of Na current. The gating abnormality deteriorated with increasing age. In DMPK(+/-) muscle there was reduced Na current amplitude and increased Na channel reopenings identical to those in DMPK(-/-) muscle. Thus, these mouse models of complete and partial DMPK deficiency reproduce the Na channel abnormality of the human disease, providing direct evidence that DMPK deficiency underlies the Na channel abnormality in DM. 相似文献
46.
47.
Punia RS Nanda A Bakshi A Mohan H Gupta S 《Indian journal of pathology & microbiology》2004,47(1):41-42
Diffuse lipomatosis is a rare disorder of adipose tissue occurring in young people . It has a predilection for trunk and proximal extremities where it presents as poorly circumscribed overgrowth of fatty tissue. Definite diagnosis is established by histological examination of tumor. Though it attains extensive size and has a high tendency to recur, the clinical course is benign. 相似文献
48.
Joshi SN Gopalkrishna V Kumar BK Dutta S Nyaynirgune P Thakar M Tripathy S Mehendale S Paranjape R 《Journal of medical virology》2005,76(4):470-475
In view of the dual burden of HIV infection and cervical cancers in India, this study was undertaken to estimate the prevalence of Pap smear abnormalities and human papillomavirus infection among HIV-infected women. Consecutive HIV-infected women attending voluntary counseling testing clinics were enrolled. Written informed consent, demographic information, Pap smears, cervical swabs for HPV typing and a blood sample for CD4+ cell count were collected. Treatment for opportunistic and sexually transmitted infections and reproductive tract infections was provided. Women with Pap smear abnormality were referred for further intervention. Between January 2003 and May 2004, 287 HIV-infected women were enrolled. Pap smear abnormalities were seen in 6.3% women and were more common among women aged 30 and above (P=0.042) and those who had suffered from opportunistic infections (P=0.004). In multivariate analysis, Pap smear abnormalities were associated independently with opportunistic infections (P=0.02, AOR 3.8, 95% CI 1.2--11.5). Of the 100 random cervical specimens screened for HPV 16 and 18 genotypes, 33% (95 CI 23.9--43.1) were positive for HPV 16/18. Of the 122 patients who returned for a follow-up visit, 5 patients (4.1%) who did not have Pap smear abnormality at baseline, had developed Pap smear abnormality. The incidence of Pap smear abnormalities was 5.5 per 100 person year of follow-up. In order to prevent thousands of deaths due to cervical cancer in India, there is a need for strengthening the Pap smear screening program and HPV vaccine development. 相似文献
49.
Egede Leonard E. Walker Rebekah J. Dawson Aprill Z. Zosel Amy Bhandari Sanjay Nagavally Sneha Martin Ian Frank Michael 《Quality of life research》2022,31(8):2387-2396
Quality of Life Research - This study aimed to investigate changes over time in quality of life, perceived stress, and serious psychological distress for individuals diagnosed with COVID-19 in an... 相似文献
50.
Beomyoung Cho Jana L. Hirschtick Bukola Usidame Rafael Meza Ritesh Mistry Stephanie R. Land David T. Levy Theodore Holford Nancy L. Fleischer 《The Journal of adolescent health》2021,68(4):750-757
PurposeThis study examines sociodemographic patterns of exclusive/dual/polytobacco use among U.S. high school students using multiple national surveys.MethodsUsing three national youth surveys (Population Assessment of Tobacco and Health [PATH] Wave 4 [2016–2017], 2017 Youth Risk Behavior Survey, and 2017 National Youth Tobacco Survey), we classified tobacco products into four groups: (1) electronic nicotine delivery systems (ENDS), (2) conventional cigarettes (CCs), (3) other combustible tobacco products, and (4) smokeless tobacco products. We created 16 categories of non/exclusive/dual/polytobacco use within the past 30 days using the four product groups and calculated weighted population prevalence by sex and race/ethnicity (all surveys) and parental education and income (PATH), based on variable availability.ResultsThe results from 9,331, 12,407, and 9,699 high school students in PATH, Youth Risk Behavior Survey, and National Youth Tobacco Survey, respectively, largely agreed and pointed to similar conclusions. ENDS was the most prevalent exclusive use product (3.8%–5.2% across surveys), with CCs falling to second or third (1.2%–2.0% across surveys). By sex, exclusive, dual, and poly smokeless tobacco product use were more common for males, whereas exclusive CC use was more common for females. By race/ethnicity, non-Hispanic Whites had a higher prevalence of exclusive ENDS use and ENDS/CC dual use than non-Hispanic Blacks. As income and parental education levels increased from low to high, the prevalence of exclusive CC use decreased, whereas the prevalence of exclusive ENDS use increased.ConclusionUnderstanding sociodemographic patterns of tobacco use can help identify groups who may be at greater risk for tobacco-related health outcomes. 相似文献