全文获取类型
收费全文 | 28856篇 |
免费 | 1195篇 |
国内免费 | 136篇 |
专业分类
耳鼻咽喉 | 304篇 |
儿科学 | 495篇 |
妇产科学 | 315篇 |
基础医学 | 3861篇 |
口腔科学 | 638篇 |
临床医学 | 1818篇 |
内科学 | 7242篇 |
皮肤病学 | 347篇 |
神经病学 | 2457篇 |
特种医学 | 1091篇 |
外科学 | 4519篇 |
综合类 | 162篇 |
一般理论 | 2篇 |
预防医学 | 821篇 |
眼科学 | 794篇 |
药学 | 2279篇 |
中国医学 | 148篇 |
肿瘤学 | 2894篇 |
出版年
2023年 | 126篇 |
2022年 | 245篇 |
2021年 | 395篇 |
2020年 | 206篇 |
2019年 | 309篇 |
2018年 | 378篇 |
2017年 | 296篇 |
2016年 | 406篇 |
2015年 | 453篇 |
2014年 | 581篇 |
2013年 | 786篇 |
2012年 | 1341篇 |
2011年 | 1486篇 |
2010年 | 800篇 |
2009年 | 681篇 |
2008年 | 1327篇 |
2007年 | 1523篇 |
2006年 | 1500篇 |
2005年 | 1614篇 |
2004年 | 1564篇 |
2003年 | 1492篇 |
2002年 | 1546篇 |
2001年 | 826篇 |
2000年 | 837篇 |
1999年 | 800篇 |
1998年 | 453篇 |
1997年 | 387篇 |
1996年 | 372篇 |
1995年 | 308篇 |
1994年 | 317篇 |
1993年 | 256篇 |
1992年 | 601篇 |
1991年 | 611篇 |
1990年 | 562篇 |
1989年 | 522篇 |
1988年 | 425篇 |
1987年 | 387篇 |
1986年 | 405篇 |
1985年 | 379篇 |
1984年 | 289篇 |
1983年 | 237篇 |
1982年 | 158篇 |
1981年 | 140篇 |
1980年 | 161篇 |
1979年 | 208篇 |
1978年 | 151篇 |
1977年 | 138篇 |
1975年 | 104篇 |
1974年 | 117篇 |
1972年 | 114篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Effects of estrogen and progesterone on the expression of connexin-36 mRNA in the suprachiasmatic nucleus of female rats 总被引:1,自引:0,他引:1
In rat, helium pressures induce locomotor and motor activity which requires dopaminergic and N-methyl-D-aspartate (NMDA) receptor activities at striatal level. However, biochemical studies have suggested that pressure exposure may increase striatal glutamate level. We used microdialysis technique to study the effects of pressure on glutamate level in the striatum and the effects of local administration of D1 (SCH23390) or D2 (sulpiride) on these changes. Pressures increase both glutamate and glutamine levels in striatal microdialysates. Administration of sulpiride (1 microM) or SCH23390 (1 microM) by reverse microdialysis did not affect significantly pressure induced glutamate increase. So, protective effects of D1 and D2 antagonists against locomotor and motor hyperactivity (LMA) are probably independent of the processes involved in the striatal glutamate increase evoked by pressure. 相似文献
152.
Myelin Degeneration in Multiple System Atrophy Detected by Unique Antibodies 总被引:2,自引:4,他引:2 下载免费PDF全文
Akinori Matsuo Ichiro Akiguchi Gregory C. Lee Edith G. McGeer Patrick L. McGeer Jun Kimura 《The American journal of pathology》1998,153(3):735-744
A rabbit antiserum (anti-EP), induced against a synthetic peptide corresponding to residues 68 to 86 of guinea pig myelin basic protein, powerfully immunostained abnormal-appearing oligodendrocytic processes and cell bodies in demyelinating areas associated with multiple system atrophy (MSA). However, as we reported previously, the antiserum, which is highly specific for the sequence QDENPVV corresponding to human myelin basic protein residues 82 to 88, failed to recognize any structures in normal human brain. QD-9, a mouse monoclonal antibody raised against human myelin basic protein residues 69 to 88, which also recognizes specifically the epitope QDENPVV, gave the same results as did anti-EP. The unusual epitope recognized by anti-EP/QD-9 antibodies appears to be accessible in areas of myelin degeneration, and the antibodies have been shown to detect such areas in multiple sclerosis and infarcted brains. These antibodies detect myelin degeneration more widely than previous conventional methods. The present study emphasizes the importance of myelin degeneration in the pathogenesis of multiple system atrophy. 相似文献
153.
Kazuo Soga Takeshi Shiono Yoshiharu Doi 《Macromolecular chemistry and physics.》1988,189(7):1531-1541
Three kinds of MgCl2-supported TiCl4 catalysts (ester-free, ethyl benzoate (EB, monoester) and dibutyl phthalate (DNBP, diester) as internal donors) were prepared. Polymerization of propylene was carried out using these catalysts with and without phenyltriethoxysilane (PTES) as an external donor. Significant differences were observed in the kinetic behavior of polymerization among ester-free, monoester, and diester systems. Addition of PTES, however, did not change the kinetic behavior. The polymers produced were separated into three fractions by extraction with boiling heptane and octane, and the molar mass distribution (MMD) curves were measured for these three fractions. The heptane-insoluble, isotactic polymer obtained in the absence of PTES was found to consist of two fractions, octane-soluble and -insoluble. The octane-soluble polymer having lower molar mass contained appreciable amounts of syndiotactic stereoblocks in the chains, whereas the octane-insoluble polymer did not contain such stereoblocks. Addition of PTES drastically increased the octane-insoluble fraction without changing the average molar mass. On the other hand, the MMD curve for the heptane-soluble, atactic polymer gradually shifted to the lower molar mass range with an increase in the concentration of PTES. From these results, the effects of internal and external donors on catalyst activity and stereospecificity were discussed putting emphasis on the differences between monoesters and diesters. 相似文献
154.
Takehiko Ohzeki Keiichi Hanaki Nobuo Ishitani Hiroko Ohtahara Hirofumi Urashima Toshinori Tsukuda Jun-Ichi Nagaishi Kazuo Shiraki 《American journal of human biology》1995,7(2):237-240
Skinfold thicknessess (SFT) were measured at ulnar, triceps, subscapular and suprailiac sites in 730 boys and 724 girls (age 3–12 years) whose stature ranged from 100 to 150 cm and whose weight was within ±20% of the average. Means and standard deviation (SD) were calculated after logarithmic transformation of the original skinfold readings to demonstrate stature-based standards of SFT in Japanese children. The means of SFT exhibited nadirs (boys/ girls: ulnar 5.1/5.9 mm, triceps 7.9/9.5 mm, subscapular 4.9/6.1 mm, suprailiac 4.5/6.2 mm) in subjects 110–115 cm tall except for ulnar SFT in girls. SFT values increased as children increased in stature. Standard deviations of SFT at the four sites in short children (staturte < mean ?1 SD) were estimated using the stature-based standard as well as an age-based standard. Susms of the SDs assessed by the age-based standard were significantly smaller than those assessed by the stature-based standard in boys (P < 0.05) and girls (P < 0.01) with short stature, suggesting that SFT in short children was falsely understimated by the age-based standard. Thus, the stature-based standard is beneficial for the assessment of SFT, especially in children whose stature is below the mean ?-1 SD. © 1995 Wiley-Liss, Inc. 相似文献
155.
Torii K Kimura H Li X Okada T Imura T Furusaki F Ono T Yoshida H 《Rinsho byori. The Japanese journal of clinical pathology》2005,53(3):207-212
Chronic hypoxia has been newly proposed as a common mechanism of tubulointerstitial fibrosis in the progression of various chronic inflammatory renal diseases, where PAI-1 plays an important role in the accumulation of extracellular matrix (ECM) through inhibition of plasmin-dependent ECM degradation. In the present study, we investigated the presence of PAI-1 in renal tubular cells by immunostaining renal biopsy samples. We also closely examined the effects of hypoxia and TNF-alpha on PAI-1 expression in cultured human proximal renal tubular cells (HRCs). Confluent cells growth-arrested in DMEM for 24h were exposed to hypoxia (1% O2) and/or TNF-alpha at 10 ng/ml for 24 hours. Amounts of PAI-1 protein and mRNA after stimulation were measured by ELISA and TaqMan quantitative PCR, respectively and compared to those in cells incubated under control conditions (18% O2 without TNF-alpha). HIF-1alpha was demonstrated by immunoblot analysis. In crescentic glomerulonephritis, clusters of proximal tubules were specifically stained for PAI-1. Treatment of 24 hours with hypoxia, TNF-alpha and their combination induced a 2.7-fold, a 1.8-fold, and a 4.6-fold increase in PAI-1 protein secretion, and produced a 3.6-fold, a 3.3-fold, and a 12.1-fold increase at the PAI-1 mRNA level, respectively. Immunoblot analysis revealed that hypoxia-inducible factor-1alpha (HIF-1alpha) was markedly accumulated in the nuclear fraction after 16-hours exposure of HPTECs to hypoxia but not to TNF-alpha. In conclusion, hypoxia induces PAI-1 expression via remarkable nuclear accumulation of HIF-1alpha in HRCs. TNF-alpha can enhance this hypoxia-induced PAI-1 expression. 相似文献
156.
Kitada S Maekura R Toyoshima N Naka T Fujiwara N Kobayashi M Yano I Ito M Kobayashi K 《Clinical and diagnostic laboratory immunology》2005,12(1):44-51
We report the development of a serodiagnostic method for Mycobacterium avium complex (MAC) disease with an enzyme immunoassay (EIA) with the MAC-specific glycopeptidolipid (GPL) core as the antigen. In this study, we confirmed by EIA that the GPL core antibody was in the sera of immunocompetent patients with MAC disease. The EIA for quantifying the GPL core antibody was evaluated as a clinical tool for serodiagnosis of pulmonary MAC disease. A significant increase in GPL core antibodies (immunoglobulins G, A, and M) was detected in sera of patients with MAC pulmonary diseases when they were compared to patients who were colonized with MAC, patients with Mycobacterium kansasii disease or tuberculosis, and healthy subjects. The sensitivities and specificities of the GPL core-based EIA for diagnosis of MAC pulmonary disease were 72.6% and 92.2%, respectively, for IgG, 92.5% and 95.1%, respectively, for IgA, and 78.3% and 91.0%, respectively, for IgM. The best sensitivity and specificity were obtained by measuring immunoglobulin A antibodies against GPL core antigen. The level of GPL core antibodies reflected disease activity, since it decreased in cured MAC patients who had responded to chemotherapy. Measurement of serum antibodies against GPL core is useful for both diagnosis and assessment of disease activity in MAC disease of the lung. 相似文献
157.
Kazuo Nagashima Hisako Endo Koko Sakakibara Yumiko Konishi Ko Miyachi Jau Jinn Wey Yoshiyuki Suzuki Jinichi Onisawa 《Pathology international》1976,26(1):115-132
An autopsy case of a 19-year-old boy who had shown typical gargoyle features, strictly consistent with mucopolysaccharidosis type II (Hunter's syndrome) was reported. Histologically, cytoplasmic vacuolar change was found In hepatocytes, sinusoidal epithelium of spleen, follicular cells of thyroid, Sertoli cells of testis, chromophobe cell of pituitary and generalized fibroblast-like cells including meninges, cardiac valve and periosteum. The vacuoles consisting of membrane-bound structures with flocculus protein-like material and occasional electron dense bodies on electron microscopy, were considered to be the site of mucopolysaccharide deposition by histochemical analysis. Deposition of lipid material consistent with so-called membranous cytoplasmic body was observed in the neurons of central, peripheral and autonomic nervous system. Hepatosplenomegaly could be explained by cytoplasmic deposition, but the cause of cardiomegaly remained further to be studied. Biochemically hepatic mucopolysaccharide was identified as heparan sulfate, while in the kidney dermatan sulfate and heparan sulfate were detected. The correlation between morphology and biochemistry, and between deposition and degeneration was discussed. 相似文献
158.
Production of interferon-like substance by mouse spleen cells through contact with BHK cells persistently infected with HVJ 总被引:3,自引:0,他引:3
A virus inhibitor, an interferon-like substance, was found in the culture fluid of mouse spleen cells cocultivated with BHK-HVJ cells, the BHK cells persistently infected with HVJ, but not in the medium of cocultivation of mouse spleen cells and normal BHK cells. Neither the culture fluid of spleen cells alone nor that of BHK-HVJ cells alone was shown to contain the virus inhibitor. No virus inhibitory activity could be detected in the culture fluid of mouse spleen cells incubated with either the culture fluid of BHK-HVJ cells contained noninfectious HVJ particles or sonicated BHK-HVJ cell suspension. L cells or mouse liver cells, when cocultivated with BHK-HVJ cells, did not release a virus inhibitor.These findings suggest that mouse lymphoid cells have a capacity to produce a virus inhibitor when cocultivated with BHK-HVJ cells, and that nonlymphoid somatic cells may lack this capacity.Interposition of a Millipore filter between BHK-HVJ monolayer and mouse spleen cells or pretreatment of BHK-HVJ cells with anti-HVJ antiserum resulted in a blockade of virus inhibitor production. These findings suggest that the following sequence is necessary for the mouse spleen cells cocultivated with BHK-HVJ cells to produce the virus inhibitor: first, attachment of the spleen cells to BHK-HVJ cells and, second, recognition by the former of virus antigen(s) present on the surface of the latter.The BHK-HVJ cell membrane, isolated by sucrose density gradient centrifuge, was found to be an active inducer of the virus inhibitor. Moreover, some artificial membranous structures, such as HVJ-erythrocyte complex as well as HVJ spike-erythrocyte complex, exhibited a similar activity.This virus inhibitor induced in the present system appears to have all biologic attributes of interferon and its production might be initiated by membrane-membrane interaction between lymphoid cells and HVJ infected cells. 相似文献
159.
Analysis of the detailed genomic structure of human N-cadherin revealed that the 16-exon gene is more than 72 kb in length
and that it consists of a mosaic of exons. Five repeated cadherin domains, a transmembrane domain, and a cytoplasmic domain
are encoded by exons 4 to 13, 13 and 14, and 14 to 16, respectively. A search for molecular variants in the entire coding
region in 96 Japanese individuals resulted in the identification of eight sequence polymorphisms including three CCT- or GCC-type
trinucleotide repeat polymorphisms adjacent to the initiation codon and five other novel single-nucleoticle polymorphisms
(SNPs) in the coding region. Three of the five SNPs accompanied an amino acid substitution: Ala118Thr, Ala826Thr, and Asn845Ser.
Knowlege of the fine gene structure and eight novel polymorphisms will be useful for the genetic study of the role of N-cadherin
in diseases involving cell adhesion in the brain and in cardiomyocytes.
Received: January 23, 2002 / Accepted: March 12, 2002 相似文献
160.
Junko Watanabe Masami Taniguchi Kiyoshi Takahashi Takemasa Nakagawa Yukihiro Ooya Akira Akazawa Kazuo Akiyama 《Arerugī》2006,55(11):1421-1428
PURPOSE: To enable international comparison of prevalence in asthma, we translated and evaluated ECRHS Questionnaire, which is introduced in GINA. Considering COPD prevalence in elder people, we added two questions to the ECRHS Questionnaire. METHOD: The Japanese edition of ECRHS Questionnaire was responded by 366 patients who were diagnosed asthma without COPD, 61 patients who were diagnosed COPD without asthma, and 137 healthy persons who were not diagnosed asthma or COPD. We analyzed the answers of the each group and evaluated the validity of the questionnaire to use for the nation-wide prevalence study of adult asthma in future. RESULTS: The question of 'Wheezing at any time in the last 12 months' had the highest Youden's index and validity to pick up asthma patients. The questions of 'Waking up with a feeling of tightness in chest at any time in the last 12 months' and 'Waking up by an attack of shortness of breath at any time in the last 12 month' had the highest specificity to pick up asthma patients. Most of the questions which were related asthma were able to be answered by asthma patients properly, but some questions were improperly answered by patients and healthy persons in elderly. The results in this study showed the less recognition of their diseases in elderly patients than younger patients and the limitation of the study with written questionnaire for elderly people. Not a few COPD patients complained wheezing or whistling in the chests as same as asthma patients in this study. CONCLUSION: We concluded that we had almost enough reliability in the Japanese edition of the ECRHS questionnaire for screening survey of asthma prevalence in Japan. 相似文献