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   6097篇
  免费   370篇
  国内免费   45篇
耳鼻咽喉   29篇
儿科学   157篇
妇产科学   167篇
基础医学   1012篇
口腔科学   79篇
临床医学   501篇
内科学   1600篇
皮肤病学   276篇
神经病学   576篇
特种医学   143篇
外科学   454篇
综合类   11篇
一般理论   2篇
预防医学   355篇
眼科学   37篇
药学   381篇
中国医学   26篇
肿瘤学   706篇
  2024年   6篇
  2023年   54篇
  2022年   148篇
  2021年   208篇
  2020年   118篇
  2019年   175篇
  2018年   199篇
  2017年   132篇
  2016年   151篇
  2015年   204篇
  2014年   258篇
  2013年   300篇
  2012年   467篇
  2011年   530篇
  2010年   290篇
  2009年   243篇
  2008年   401篇
  2007年   392篇
  2006年   424篇
  2005年   373篇
  2004年   349篇
  2003年   303篇
  2002年   292篇
  2001年   32篇
  2000年   26篇
  1999年   47篇
  1998年   59篇
  1997年   58篇
  1996年   49篇
  1995年   46篇
  1994年   33篇
  1993年   30篇
  1992年   17篇
  1991年   18篇
  1990年   13篇
  1989年   17篇
  1988年   13篇
  1987年   5篇
  1986年   5篇
  1985年   3篇
  1984年   7篇
  1983年   3篇
  1981年   5篇
  1980年   4篇
  1979年   1篇
  1977年   4篇
排序方式: 共有6512条查询结果,搜索用时 9 毫秒
91.
In this study, we have investigated in vivo the time-dependent effects of TSH on vascular endothelial growth factor (VEGF) production in patients monitored for thyroid carcinoma. Serum VEGF, thyroglobulin (Tg), and TSH levels were assayed at baseline and 6, 24, 30, 48, 72, and 96 h and 1 wk after administration of recombinant human TSH (rhTSH) in 45 thyroidectomized patients affected by differentiated thyroid carcinoma. At baseline, the patients with metastasis (18 cases) showed serum Tg and VEGF values significantly higher than those seen in the cured patients (27 cases). During rhTSH stimulation, the mean VEGF levels decreased significantly in both patient groups. In 60% of patients with metastasis, VEGF nadir occurred at the same time as serum TSH reached the highest values, whereas in 85.7% of the cured patients VEGF decreased after the TSH peak (P = 0.003). In conclusion, we demonstrate for the first time that short-term administration of rhTSH in patients monitored for differentiated thyroid carcinoma induces a significant reduction in serum VEGF values even in the absence of thyroid tissue. This result would suggest that TSH may be able in vivo to regulate VEGF production from tissues other than the thyroid gland.  相似文献   
92.
OBJECTIVE: To evaluate the vasodilation induced by topical application of methyl nicotinate (MN) and to compare it with the vasodilatory response to acetylcholine (ACh) and sodium nitroprusside (SNP) in healthy subjects and diabetic neuropathic patients. RESEARCH DESIGN AND METHODS: Ten diabetic patients with peripheral neuropathy (DN) and 10 age- and sex-matched healthy control subjects (C) were enrolled. The vasodilatory response to topical application of 1% MN and a placebo emulsion at the forearm and dorsum of the foot skin at 5, 15, 30, 60 and 120 min was measured using Laser Doppler Perfusion Imaging. The vasodilatory response to iontophoresis of 1% ACh and 1% SNP solutions was also evaluated. RESULTS: The maximal vasodilatory response to ACh, SNP and MN was similar at the forearm and foot level in the diabetic patients. In the control group, the responses to MN, ACh and SNP were similar on the forearm but in the foot, the MN vasodilatory response was higher when compared to the ACh and SNP responses. MN-related vasodilation was present 5 min after the application, reached its peak at 15-30 min and declined to pre-application levels 120 min afterward. CONCLUSIONS: Topical application of MN at the forearm and foot levels of diabetic neuropathic patients results in skin vasodilation that is comparable to the maximal vasodilation that can be induced by iontophoresis of ACh or SNP and lasts for less than 2 h. Further studies will be required to explore the potential of MN to increase blood flow and to prevent diabetic foot problems in clinical practice.  相似文献   
93.
Haemochromatosis is an autosomal recessive disorder common among Caucasians that leads to iron overload. Molecular studies have shown that the disease is prevalently due to a mutation in the HFE gene. Although C282Y in the homozygous state remains the most common patient's genotype, other genes and genetic mutations are associated with haemochromatosis. Haemochromatosis type 2, a severe form with juvenile onset, is due to mutations in an unidentified gene on chromosome 1q. Haemochromatosis type 3 is linked to a locus on 7q22 and is due to mutations in the transferrin receptor 2. Haemochromatosis type 4, the only autosomal dominant form, is caused by mutations in ferroportin 1 on 2q32. The genes responsible for African and neonatal forms of iron overload are still unknown. The identification of all of the genes associated with haemochromatosis is critical for molecular-based diagnosis and central to our understanding of the regulation of iron homeostasis.  相似文献   
94.
95.

BACKGROUND:

Acute nonarteritic anterior ischemic optic neuropathy (NAION) is considered to be acute ischemia of the posterior ciliary arteries. Prostaglandin E1 (PGE1), a powerful microcirculation vasodilator, has been shown to improve ocular blood flow.

DESIGN:

A nonrandomized, comparative trial.

METHODS:

Eight consecutive cases of NAION were treated with intravenous steroids and PGE1. Seven control cases of NAION were treated with acetylsalicylic acid and oral steroids. Fisher’s exact test was used for statistical analysis.

RESULTS:

The visual acuity improved in seven cases of NAION treated with PGE1 and was unchanged in one. Of the seven control cases, four had no change in vision and three lost further visual acuity on follow-up visits.

CONCLUSIONS:

Intravenous PGE1 and steroids should be considered in cases of NAION to immediately restore blood flow to the optic nerve and improve visual acuity.  相似文献   
96.
HIV-1 protease inhibitors (PIs) may improve hematopoietic functions owing to their direct effects on bone marrow (BM) progenitor cells. In this study we investigated this hypothesis evaluating the effect of adding ritonavir (RTV) and indinavir (IND) on hematopoietic colony formation assays by colony-forming cell (CFC) and long-term culture-initiating cell (LTC-IC) assays, on apoptosis, on cytokine production and stromal cells, in subjects with HIV-1 infection, and in seronegative controls. After PI addition, CFC and LTC-IC assays in HIV-1-infected patients showed levels of colony growth significantly higher than those observed at baseline; the same PI activity on colony formation was observed in healthy subjects. No significant modifications on Fas, the membrane form of Fas (mFas) and Fas-ligand (FasL) expression, and on cytokine production were observed at BM level after the addition of PIs. At baseline, in HIV-1-infected patients, the majority of the stromal cells appeared as large and rounded, whereas after the addition of RTV or IND the stromal cells exhibited a "fibroblast-like" morphology and produced higher stem cell factor (SCF) and lower MIP-1alpha levels when compared with the stromal production without the addition of IND. RTV and IND increased colony growth of BM obtained either from HIV-1-infected patients or from normal individuals, in parallel with the normalization of functional and morphological characteristics of stromal cells.  相似文献   
97.
98.
The human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus, is a gamma herpesvirus associated with AIDS-related body cavity-based lymphomas (BCBL), also called primary effusion lymphomas (PEL). These are a rare form of non-Hodgkin lymphomas in which HHV-8 is present, often associated with Epstein-Barr virus (EBV) infection. HHV-8 is also present in a latent state or in a state of low-level persistence in different primary effusion lymphoma-derived cell lines, such BCBL-1 cells, that lack EBV infection. This cell line was induced to produce mature virions by treatment with 12- O -tetradecanoyl phorbol-13-acetate (TPA) and the characteristic ultrastructural features of HHV-8 lytic replication were identified and compared to those of the other members of Herpesviridae family.  相似文献   
99.
In order to assess the frequency of clinically relevant linezolid-resistant staphylococcal isolates, and the role of linezolid in maintaining and coselecting multiple resistance mechanisms (cfr, 23S rRNA, L3/L4 mutations), a prospective Italian study was performed from 2010 to 2011 to confirm the diffusion of three major multidrug-resistant clones (ST2, ST5, ST23).  相似文献   
100.
Testicular germ cell tumors account for about 1% of all cancers. The incidence of these tumors is increasing and they represent the most common solid malignancies of young men aged 15–40 years with seminoma being one of the most common histotype. Pathogenesis of testicular germ cell tumors remains unknown and, although cryptorchidism is considered the main risk factor, there is evidence of an association with environmental and genetic risk factors. Human papillomaviruses (HPV) are a family of DNA viruses and represent a major risk factor for cervical cancer. In addition, they have been associated with other human non‐malignant and malignant diseases, including breast and head and neck cancer. HPV sequences have been detected throughout the male lower genitourinary tract as well as in seminal fluid and an increased testicular tumorigenesis has been reported in HPV transgenic mice. Aim of this study was to evaluate the potential involvement of HPV in human testicular tumorigenesis. Real‐time PCR employing GP5+/GP6+ consensus HPV primers was used to examine the presence of HPV sequences in a subset of human seminoma (n = 61) and normal testicles (n = 23). None of the specimens tested displayed the presence of HPV DNA. These findings do not support an association between HPV and human seminoma and warrant further studies to assess definitively the role of these viruses in human testicular tumorigenesis. J. Med. Virol. 85:105–109, 2012. © 2012 Wiley Periodicals, Inc.  相似文献   
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