首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4808篇
  免费   219篇
  国内免费   9篇
耳鼻咽喉   28篇
儿科学   50篇
妇产科学   72篇
基础医学   654篇
口腔科学   129篇
临床医学   322篇
内科学   1078篇
皮肤病学   295篇
神经病学   442篇
特种医学   189篇
外科学   796篇
综合类   22篇
预防医学   159篇
眼科学   42篇
药学   330篇
中国医学   6篇
肿瘤学   422篇
  2023年   30篇
  2022年   92篇
  2021年   102篇
  2020年   35篇
  2019年   73篇
  2018年   98篇
  2017年   56篇
  2016年   77篇
  2015年   80篇
  2014年   118篇
  2013年   123篇
  2012年   239篇
  2011年   200篇
  2010年   122篇
  2009年   101篇
  2008年   159篇
  2007年   194篇
  2006年   175篇
  2005年   214篇
  2004年   194篇
  2003年   184篇
  2002年   176篇
  2001年   167篇
  2000年   173篇
  1999年   176篇
  1998年   55篇
  1997年   36篇
  1996年   49篇
  1995年   50篇
  1994年   25篇
  1993年   38篇
  1992年   129篇
  1991年   149篇
  1990年   150篇
  1989年   111篇
  1988年   120篇
  1987年   90篇
  1986年   78篇
  1985年   104篇
  1984年   78篇
  1983年   41篇
  1982年   23篇
  1981年   30篇
  1979年   39篇
  1978年   29篇
  1977年   29篇
  1975年   20篇
  1973年   28篇
  1972年   20篇
  1971年   19篇
排序方式: 共有5036条查询结果,搜索用时 31 毫秒
51.
An autopsy case of hepatitis associated aplastic anemia was presented. A 58-year-old Japanese female with non-A, non-B hepatitis was admitted on August 2, 1983. Moderate grade of fever and hemorrhagic diathesis appeared on September 16, when hepatitis was evaluated as being under resolving. The peripheral blood and bone marrow findings were consistent with aplastic anemia. Since infection was suggested by increased levels of serum gamma-globulin and CRP, treatment with antibiotics as well as prednisolone and blood transfusion was initiated. Since September 21, gradual tenderness and edema on the right lower abdominal wall appeared. She died on October 3.
On postmortem examination, systemic plasmacytosis with lymphadenopathy and septic monilial infection was revealed. Numerous plasma cells were atypical, but were immunohistochemically proved to be polyclonal. The bone marrow showed a massive and diffuse plasma cell proliferation with extremely scarce myeloid cells and megakaryocytes. There was a large granulomatous lesion with monilial infection in the wall of the ileocecum. By these findings, systemic plasmacytosis was suspected to be due to chronic monilial infection.
The pathogenesis of systemic plasmacytosis in aplastic anemias and in other diseases were discussed with relation to the present case.  相似文献   
52.
A highly sensitive, simple and reliable one-step sandwich enzyme immunoassay (EIA) for the gamma-carboxylated form of osteocalcin (Gla-OC) has been developed using a monoclonal antibody. The minimum amount of Gla-OC detected by this EIA was approximately 0.2 ng/ml when a 10 microliter aliquot of the sample was used. The serum Gla-OC level in 30 healthy subjects was 3.6 +/- 2.19 ng/ml (mean +/- SD). A significant increase was seen in patients with chronic renal failure (20.3 +/- 4.60 ng/ml), atherosclerosis (8.3 +/- 4.94 ng/ml) and osteoporosis (10.1 +/- 4.60 ng/ml). The correlation between the values obtained by the sandwich EIA and competitive RIA methods was given by the linear regression equation, y = 2.896 + 0.759 chi, for which the correlation coefficient (r) was 0.815 (n = 58). This newly developed Gla-OC specific EIA may be useful for the diagnosis of metabolic bone disease and ectopic calcification.  相似文献   
53.
Translation initiation of hepatitis C virus (HCV) RNA is controlled by an internal ribosome entry site (IRES) contained in 5 noncoding region (NCR) and in several nucleotides of the coding region. The ability of a 25-kilodalton cellular protein (p25) to bind the HCV 5 NCR is correlated with the efficiency of translation initiation of HCV RNA, indicating that this protein plays a critical role in HCV translation (S. Fukushi, C. Kurihara, N. Ishiyama, F. B. Hoshino, A. Oya, and K. Katayama, J Virol 71, 1662–1666, 1997). We have extended the study for identification of the IRES region required for p25 binding. For this purpose, we have performed UV cross-linking competition analyses using 5- or 3- deleted mutants of the HCV 5 NCR as competitor RNAs for binding of p25 to wild-type HCV 5 NCR. Competitor RNAs lacking nucleotides (nt) 47–74 or nt 279–331 did not inhibit p25 binding to the HCV IRES, indicating that these regions are necessary for interaction of the p25 and HCV IRES. Since p25 binding was not observed in the IRES elements of encephalomyocarditis virus and poliovirus in UV cross-linking competition analyses, the p25 binding may be specific for the HCV IRES. p25 bound to the HCV IRES was detected when a purified 40S ribosomal subunit was used for UV cross-linking experiment, indicating that p25 is one of 40S ribosomal subunit proteins. These results reveal an unique interaction between the 40S ribosomal subunit and HCV IRES to contribute to translation initiation of the HCV genome.  相似文献   
54.
Capillary endothelial proliferation is often a prominent feature of malignant gliomas. The understanding of structural and functional characteristics of the vascular microenvironment in gliomas is essential for the design of future therapeutic strategies against this tumor. Electron microscopic analysis of the capillary endothelial proliferation in malignant gliomas indicated that the complex vascular structures within the tumor were composed essentially of immature capillaries. Immature capillaries had a narrow slitlike lumen composed of endothelial cells with their high nuclear:cytoplasmic ratio and the relative paucity of organelles. They resembled capillary buds seen in normal repair tissue. Immature microvessels caused by angiogenesis were found more frequently in marginal zone of the tumors with increased microvessels. The tubular body was an organelle observed in vascular endothelial cells and was used frequently as a marker of the endothelial cell. Tubular bodies were evaluated by quantitative measurement of the mean percent (%) ratio of the number of endothelial cells with tubular bodies to all endothelial cells in microvessels of tumors. In glioblastomas it yielded a value of 32.4% in the margin, about two times as high as that in the center of the tumors. However, it was lower in all locations of astrocytomas. Tubular bodies in endothelial cells could be increased in proportion to neovascularization, and they might serve as a marker for increasing microvessels in astrocytic tumors. Tumor angiogenesis may be regulated by growth factors with angiogenic activities that are secreted by tumor cells. Vascular endothelial growth factor (VEGF) may play a critical role in the regulation of vascular endothelial proliferation. We found that 86% of 29 glioblastomas and 79% of 14 anaplastic astrocytomas demonstrated immunoreactivity for VEGF in their tumor cells. There tended to be a correlation between VEGF and vascularity. A correlation existed between the grade of immunoreactivity for VEGF and the grade of p53 protein expression in the malignant gliomas. However, the MIB-1 indices did not increase in correlation with increase in the extent of immunoreactivity for VEGF.  相似文献   
55.
In hepatitis C virus (HCV) infection, immune complex (IC)-type virus particles are frequently observed in circulation. The IC leads to cross-linking of Fcgamma receptors (FcgammaR) on monocytes and exerts immunoinhibitory function. To test the roles of IC in HCV-specific cytotoxic T lymphocyte (CTL) induction, we generated HCV CTL from peripheral blood mononuclear cells of chronic hepatitis C patients with or without HCV-IC- or immunoglobulin G (IgG)-coated culture plates and compared their lytic activities. HCV-IC or adherent IgG, which induces FcgammaR cross-linking, significantly reduced CTL activity. Expression of B7-1 on monocytes decreased on adherent IgG. In addition, tumour necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1) production increased from cells on adherent IgG and their mRNA expression in monocytes was enhanced. Anti-TNF-alpha antibody during induction on adherent IgG inhibited lysis; however, anti-TGF-beta completely reversed its inhibitory effect. These results demonstrated that HCV-IC or adherent IgG impaired HCV-CTL induction in vitro. The FcgammaR-mediated CTL suppression occurred via decreased expression of monocyte B7-1 and/or enhanced production of TGF-beta1.  相似文献   
56.
We have established the electrical polarization method of hydroxyapatite (HA) coatings (HAC) for clinical use, such as dental and orthopedic implants. The HAC examined in the current study was prepared in titanium substrates by plasma spraying of beta-tricalcium phosphate (TCP) powders followed by hydrothermal treatment. The prepared HAC consisted of a single phase of HA, because the starting TCP phase was completely transformed to the HA phase during the posthydrothermal treatment. Polarization was carried out at the elevated temperature of 400 degrees C under a d.c. field of 1 kV . cm(-1). The electrical measurements showed that the stored charges of the polarized HAC were greater than the reported value of the sintered ceramic HA. The enhanced bioactivity of the polarized HAC was demonstrated using 1.5 simulated body fluid (SBF). The crystal growth from the SBF solution was accelerated on the negatively charged surface in comparison with the untreated HAC. Similar to the polarized ceramic HA, the current results confirmed that the bioactivity of HAC would be effective for improving the initial fixation by polarization.  相似文献   
57.
58.
Copolymers from 1,6-heptadiene ( 1 ) and SO2 with various mole ratios of their units were prepared. Their structures were studied by elemental analyses, IR and 1H NMR spectroscopy. Structures containing a cyclopentane ring ( 2 ) and such containing a thiane ring ( 3 ) in the main chain are proposed.  相似文献   
59.
Abstract. The purpose of the present study was to examine the changes in maximum voluntary isometric contraction (MVC) in the contralateral untrained limb during unilateral resistance training and detraining, and to examine the factors inducing these changes by means of electrophysiological techniques. Nine healthy males trained their plantar flexor muscles unilaterally 4 days·week–1 for 6 weeks using 3 sets of 10–12 repetitions at 70–75% of one-repetition maximum a day, and detrained for 6 weeks. Progressive unilateral resistance training significantly (P<0.05) increased MVC, integrated electromyogram (iEMG), and voluntary activation in the trained and contralateral untrained limbs. The changes in MVC after training were significantly correlated with the changes in iEMG in both limbs. No significant changes occurred in MVC, voluntary activation, and iEMG in the contralateral limb after detraining. The changes in MVC after detraining did not correlate with the changes in voluntary activation or iEMG in either limb. Training and detraining did not alter twitch and tetanic peak torques in either limb. These results suggest that the mechanisms underlying cross education of muscular strength may be explained by central neural factors during training, but not solely so during detraining. Electronic Publication  相似文献   
60.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号