全文获取类型
收费全文 | 24147篇 |
免费 | 1489篇 |
国内免费 | 214篇 |
专业分类
耳鼻咽喉 | 402篇 |
儿科学 | 364篇 |
妇产科学 | 339篇 |
基础医学 | 4054篇 |
口腔科学 | 399篇 |
临床医学 | 2082篇 |
内科学 | 4721篇 |
皮肤病学 | 763篇 |
神经病学 | 2072篇 |
特种医学 | 1212篇 |
外科学 | 3201篇 |
综合类 | 106篇 |
一般理论 | 5篇 |
预防医学 | 1096篇 |
眼科学 | 512篇 |
药学 | 2208篇 |
中国医学 | 298篇 |
肿瘤学 | 2016篇 |
出版年
2024年 | 25篇 |
2023年 | 216篇 |
2022年 | 524篇 |
2021年 | 878篇 |
2020年 | 463篇 |
2019年 | 652篇 |
2018年 | 741篇 |
2017年 | 571篇 |
2016年 | 836篇 |
2015年 | 1052篇 |
2014年 | 1206篇 |
2013年 | 1447篇 |
2012年 | 2139篇 |
2011年 | 2028篇 |
2010年 | 1183篇 |
2009年 | 958篇 |
2008年 | 1503篇 |
2007年 | 1404篇 |
2006年 | 1309篇 |
2005年 | 1166篇 |
2004年 | 1023篇 |
2003年 | 911篇 |
2002年 | 788篇 |
2001年 | 430篇 |
2000年 | 404篇 |
1999年 | 344篇 |
1998年 | 164篇 |
1997年 | 128篇 |
1996年 | 117篇 |
1995年 | 104篇 |
1994年 | 81篇 |
1993年 | 71篇 |
1992年 | 102篇 |
1991年 | 103篇 |
1990年 | 78篇 |
1989年 | 73篇 |
1988年 | 77篇 |
1987年 | 67篇 |
1986年 | 54篇 |
1985年 | 54篇 |
1984年 | 38篇 |
1983年 | 41篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1979年 | 41篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1969年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This study examined the long-term substance use outcomes of 2 brief interventions designed for general population families of young adolescents. Thirty-three public schools were randomly assigned to 3 conditions: the 5-session Preparing for the Drug Free Years Program, the 7-session Iowa Strengthening Families Program, and a minimal contact control condition. The pretest involved 667 6th graders and their families. Assessments included multiple measures of initiation and current use of alcohol, tobacco, and marijuana. Pretest data were collected in the 6th grade and the reported follow-up data were collected in the 10th grade. Significant intervention-control differences in initiation and current use were found for both interventions. It is concluded that brief family skills-training interventions designed for general populations have the potential to reduce adolescent substance use and thus have important public health implications. 相似文献
72.
After the gamma-irradiation sterilization, the most widely used orthopaedic grade polymer bearing liner material for the total joint replacement, ultra-high molecular weight polyethylene (UHMWPE), degrades through the progressive in vivo oxidation. The oxidative degradation makes UHMWPE brittle and leads to reduction of its mechanical properties. In this study, the effect of the in vivo post-irradiation ageing time on the wear of UHMWPE was investigated. Twelve retrieved polyethylene hip liners implanted for 3-16 years and then stored in the air for 1.5-8 years were used. Two types of the pin-on-disk wear testing were conducted. The uni-directional repeat pass rotating and the linear reciprocating wear testing were done with stainless steel disks against stationary polyethylene pins under 4MPa at 1Hz with bovine serum lubrication. Wear of the retrieved polyethylene hip liners does not have significant correlation with the in vivo or total ageing time. The linear reciprocal sliding motion generated a more pronounced wear than the uni-directional repeat pass sliding motion. This indicates that the kinematic motion significantly affects the wear of aged UHMWPE, having a brittle, white band region. 相似文献
73.
Antimicrobial agents played a miraculous role in the treatment of bacterial infections until resistant bacteria became widespread. Besides antimicrobial-resistant bacteria, many factors can influence the cure of infection. Nocardia infection may be a good example which is difficult to cure with antimicrobial agents alone. A 66-year-old man developed soft tissue infection of the right buttock and thigh. He was given prednisolone and azathioprine for pachymeningitis 3 months prior to admission. Despite surgical and antimicrobial treatment (sulfamethoxazole-trimethoprim), the infection spread to the femur and osteomyelitis developed. The case showed that treatment of bacterial infection is not always as successful as was once thought because recent isolates of bacteria are more often resistant to various antimicrobial agents, intracellular parasites are difficult to eliminate even with the active drug in vitro, and infections in some sites such as bone are refractory to treatment especially when the patient is in a compromised state. In conclusion, for the treatment of infections, clinicians need to rely on laboratory tests more than before and have to consider the influence of various host factors. 相似文献
74.
In most cases, while schwannoma is sporadically manifested as a single benign neoplasm, the presence of multiple schwannomas in one patient is usually indicative of neurofibromatosis 2. However, several recent reports have suggested that schwannomatosis itself may also be a distinct clinical entity. This study examines an extremely rare case of probable schwannomatosis associated with intracranial, intraspinal and peripheral involvements. A 63-year-old woman presented with a seven-year history of palpable lumps on both sides of the supraclavicular area and hearing impairment in both ears. On physical examination, no skin manifestations were evident. Facial sensory change, deafness in the left ear and decreased gag reflex were revealed by neurological examination. Magnetic resonance imaging revealed multiple lesions of the trigeminal nerves, acoustic nerves, lower cranial nerves, spinal accessory nerve, brachial plexuses, and spinal nerves. Pathological examination of tumors from the bilateral brachial plexuses, the spinal nerve in the T8 spinal position and the neck mass revealed benign schwannomas. Following is this patient case report of multiple schwannomas presenting with no skin manifestations of neurofibromatosis. 相似文献
75.
Law CL Hayden-Ledbetter M Buckwalter S McNeill L Nguyen H Habecker P Thorne BA Dua R Ledbetter JA 《International immunology》2002,14(4):389-400
The TCR-CD3 complex consists of the clonotypic disulfide-linked TCRalphabeta or TCRdeltagamma heterodimers, and the invariant CD3delta, epsilon, gamma and zeta chains. We generated plasmid constructs expressing the extracellular domains of the CD3delta, epsilon or gamma subunits fused to human IgG1 Fc. Recombinant fusion proteins consisting of individual CD3delta, epsilon or gamma subunits reacted poorly with anti-CD3 mAb including G19-4, BC3, OKT3 and 64.1. Co-expression of the CD3epsilon-Ig with either the CD3delta-Ig (CD3epsilondelta-Ig) or the CD3gamma-Ig (CD3epsilongamma-Ig) resulted in fusion proteins with much increased binding to G19-4. A brief acid treatment of the purified CD3epsilondelta-Ig fusion protein substantially improved its binding to BC3, OKT3 and 64.1. Surface plasmon resonance analysis revealed that the dissociation constants for CD3epsilondelta-Ig and anti-CD3 mAb ranged from 10(-8) to 10(-9) M. Based on these results, a single-chain (sc) construct encoding the CD3delta chain linked to the CD3epsilon chain with a flexible linker followed by human IgG1 Fc was expressed. The sc CD3deltaepsilon-scIg reacted with anti-CD3 mAb without requiring acid treatment. Moreover, anti-CD3 mAb bound CD3epsilondelta-Ig at a higher affinity than CD3epsilongamma-Ig, suggesting potential structural differences between the CD3epsilondelta and CD3epsilongamma subunits. In summary, we report the expression of soluble recombinant CD3 proteins that demonstrate structural characteristics of the native CD3 complex expressed on the T cell surface. These CD3 fusion proteins can be used to further analyze the structure of the TCR-CD3 complex, and to identify molecules that can interfere with TCR-CD3-mediated signal transduction by disrupting the interaction between CD3 and TCR subunits. 相似文献
76.
Kim SH Shin JW Park SA Kim YK Park MS Mok JM Yang WI Lee JW 《Journal of biomedical materials research. Part B, Applied biomaterials》2004,68(1):69-74
The purpose of this study is to determine the efficacy of bioactive calcium phosphate obtained from porcine cancellous bone for the treatment of bone defects and nonunion. Porcine cancellous bone blocks were heat treated at 1300 degrees C for 2 h. The chemical composition, calcium-to-phosphate ratio, and microstructure of the porcine bone blocks were examined. For in vivo implantation, bone defects were created on the anteromedial aspect of the proximal tibia in seven beagle dogs and the xenograft bone blocks were placed into these defects. Plain radiographs were taken at 2-week intervals for roentgenographic evaluation. At 12 weeks, the specimens were stained with hematoxylin and eosin (H&E). The composition and morphology of heat-treated porcine cancellous bone were found to be similar to heat-treated human cancellous bone. Radiographs showed union between the host bone/bone-block interfaces. At 12 weeks, uniform and substantial new bone formation was observed. It is concluded that heat-treated porcine cancellous bone demonstrated effective osteoconductivity. This high-temperature heat-treatment technique has several advantages, including decreased risk of disease transmission and immunoreactivity, while also offering excellent biocompatibility. 相似文献
77.
Activation of lipid metabolism contributes to interleukin-8 production during Chlamydia trachomatis infection of cervical epithelial cells 下载免费PDF全文
Chlamydia trachomatis infection is the most common cause of bacterial sexually transmitted diseases. Infection of the urogenital tract by C. trachomatis causes chronic inflammation and related clinical complications. Unlike other invasive bacteria that induce a rapid cytokine/chemokine production, chlamydial infection induces delayed inflammatory response and proinflammatory chemokine production that is dependent on bacterial growth. We present data here to show that the lipid metabolism required for chlamydial growth contributes to Chlamydia-induced proinflammatory chemokine production. By gene microarray profiling, validated with biochemical studies, we found that C. trachomatis LGV2 selectively upregulated PTGS2 (COX2) and PTGER4 (EP4) in cervical epithelial HeLa 229 cells. COX2 is an enzyme that catalyzes the rate-limiting step of arachidonic acid conversion to prostaglandins, including prostaglandin E2 (PGE2) and other eicosanoids, whereas EP4 is a subtype of cell surface receptors for PGE2. We show that Chlamydia infection induced COX2 protein expression in both epithelial cells and peripheral blood mononuclear cells and promoted PGE2 release. Exogenous PGE2 was able to induce interleukin-8 release in HeLa 229 epithelial cells. Finally, we demonstrated that interleukin-8 induction by Chlamydia infection or PGE2 treatment was dependent on extracellular signal-regulated kinase/mitogen-activated protein activity. Together, these data demonstrate that the host lipid remodeling process required for chlamydial growth contributes to proinflammatory chemokine production. This study also highlights the importance of maintaining a balanced habitat for parasitic pathogens as obligate intracellular organisms. 相似文献
78.
We report two cases of lichen planus pigmentosus (LPP) that developed in a unilateral linear pattern. The patients presented with unilateral linear brown macules on the extremities. Skin biopsy showed orthokeratosis, basal hydropic degeneration with scarce lymphohistiocytic infiltrates, and numerous melanophages in both patients. These patients, to the best of our knowledge, are the first cases of LPP presenting with a linear pattern. LPP should be considered in the differential diagnosis of linear hyperpigmented skin lesions. 相似文献
79.
Protective effect of Hypericum perforatum Linn (St. John's wort) against hydrogen peroxide-induced apoptosis on human neuroblastoma cells 总被引:3,自引:0,他引:3
Jang MH Lee TH Shin MC Bahn GH Kim JW Shin DH Kim EH Kim CJ 《Neuroscience letters》2002,329(2):177-180
The medicinal plant Hypericum perforatum Linn, commonly known as St. John's wort, has been used as an antidepressant. To investigate whether St. John's wort possesses a protective effect against hydrogen peroxide (H(2)O(2))-induced cytotoxicity in neuronal cells, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, 4,6-diamidino-2-phenylindole staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, flow cytometry analysis, DNA fragmentation assay, and caspase-3 enzyme assay were performed on SK-N-MC human neuroblastoma cells. Cells treated with H(2)O(2) exhibited several apoptotic features, while those pre-treated with St. John's wort prior to H(2)O(2) exposure showed a decreased occurrence of apoptotic features. In addition, pre-treatment with St. John's wort inhibited H(2)O(2)-induced increase in caspase-3 enzyme activity. These results suggest that St. John's wort may exert a protective effect against H(2)O(2)-induced apoptosis in human neuroblastoma cells. 相似文献
80.
Shin Kobayashi Hiraku Uemura Takashi Kohda Toshiro Nagai Yasutsugu Chinen Kenji Naritomi Ei‐ichi Kinoshita Hirofumi Ohashi Kiyoshi Imaizumi Masato Tsukahara Yoshitsugu Sugio Hidefumi Tonoki Tatsuya Kishino Toshiaki Tanaka Masao Yamada Osamu Tsutsumi Norio Niikawa Tomoko Kaneko‐Ishino Fumitoshi Ishino 《American journal of medical genetics. Part A》2001,104(3):225-231
Silver‐Russell syndrome (SRS) is characterized by prenatal and postnatal growth retardation with morphologic anomalies. Maternal uniparental disomy 7 has been reported in some SRS patients. PEG1/MEST is an imprinted gene on chromosome 7q32 that is expressed only from the paternal allele and is a candidate gene for SRS. To clarify its biological function and role in SRS, we screened PEG1/MEST abnormalities in 15 SRS patients from various standpoints. In the lymphocytes of SRS patients, no aberrant expression patterns of two splice variants (α and β) of PEG1/MEST were detected when they were compared with normal samples. Direct sequence analysis failed to detect any mutations in the PEG1/MEST α coding region, and there were no significant mutations in the 5′‐flanking upstream region containing the predicted promoter and the highly conserved human/mouse genomic region. Differential methylation patterns of the CpG island for PEG1/MEST α were normally maintained and resulted in the same pattern as in the normal control, suggesting that there was no loss of imprinting. These findings suggest that PEG1/MEST can be excluded as a major determinant of SRS. © 2001 Wiley‐Liss, Inc. 相似文献