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   10780篇
  免费   540篇
  国内免费   96篇
耳鼻咽喉   151篇
儿科学   191篇
妇产科学   65篇
基础医学   1185篇
口腔科学   228篇
临床医学   625篇
内科学   3027篇
皮肤病学   186篇
神经病学   749篇
特种医学   390篇
外科学   1809篇
综合类   48篇
预防医学   237篇
眼科学   219篇
药学   680篇
中国医学   60篇
肿瘤学   1566篇
  2024年   7篇
  2023年   73篇
  2022年   154篇
  2021年   322篇
  2020年   184篇
  2019年   249篇
  2018年   324篇
  2017年   221篇
  2016年   318篇
  2015年   314篇
  2014年   379篇
  2013年   452篇
  2012年   699篇
  2011年   836篇
  2010年   458篇
  2009年   354篇
  2008年   653篇
  2007年   727篇
  2006年   693篇
  2005年   706篇
  2004年   696篇
  2003年   690篇
  2002年   675篇
  2001年   112篇
  2000年   63篇
  1999年   90篇
  1998年   117篇
  1997年   116篇
  1996年   95篇
  1995年   85篇
  1994年   75篇
  1993年   65篇
  1992年   40篇
  1991年   41篇
  1990年   42篇
  1989年   31篇
  1988年   38篇
  1987年   12篇
  1986年   17篇
  1985年   23篇
  1984年   14篇
  1983年   28篇
  1982年   18篇
  1981年   22篇
  1980年   17篇
  1978年   12篇
  1977年   9篇
  1976年   8篇
  1975年   10篇
  1973年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The antitumor 3'-ethynyl nucleosides, 1-(3-C-ethynyl-beta-D-ribopentofuranosyl)cytosine (ECyd) and 1-(3-C-ethynyl-beta-D-ribopentofuranosyl)uridine (EUrd), are potent inhibitors of RNA polymerases and show excellent antitumor activity against various human solid tumors in xenograft models. ECyd is being investigated in phase I clinical trials as a novel anticancer drug possessing a unique antitumor action. ECyd and EUrd require the activity of uridine/cytidine kinase (UCK) to produce the corresponding active metabolite. The UCK family consists of two members, UCK1 and UCK2, and both UCKs are expressed in many tumor cells. It was unclear, however, whether UCK1 or UCK2 is responsible for the phosphorylation of the 3'-ethynyl nucleosides. We therefore established cell lines that are highly resistant to the 3'-ethynyl nucleosides from human fibrosarcoma HT-1080 and gastric carcinoma NUGC-3. All the resistant cell lines showed a high cross-resistance to ECyd and EUrd. As a result of cDNA sequence analysis, we found that UCK2 mRNA expressed in EUrd-resistant HT-1080 cells has a 98-base pair deletion of exon 5, whereas EUrd-resistant NUGC-3 cells were harboring the point mutation at nucleotide position 484 (C to T) within exon 4 of UCK2 mRNA. This mutation was confirmed by genome sequence analysis of the UCK2 gene. Moreover, the expression of UCK2 protein was decreased in these resistant cells. In contrast, no mutation in the mRNA or differences in protein expression levels of UCK1 were shown in the EUrd-resistant HT-1080 and NUGC-3 cells. These results suggest that UCK2 is responsible for the phosphorylation and activation of the antitumor 3'-ethynyl nucleosides.  相似文献   
102.
103.
Unrelated cord blood transplantation (CBT) is an alternative curative option for adult patients with acute myeloid leukemia (AML) who need allogeneic hematopoietic cell transplantation (HCT) but lack an HLA-matched related or unrelated donor. However, large-scale data are lacking on CBT outcomes for unselected adult AML. To investigate the trends of survival and engraftment after CBT over the past 22 years, we retrospectively evaluated the data of patients with AML in Japan according to the time period of CBT (1998–2007 vs 2008–2013 vs 2014–2019). A total of 5504 patients who received single-unit CBT as first allogeneic HCT for AML were included. Overall survival (OS) at 2 years significantly improved over time. The improved OS among patients in ≥ complete remission (CR)3 and active disease at CBT was mainly due to a reduction of relapse-related mortality, whereas among patients in first or second CR at CBT, this was due mainly to a reduction of non-relapse mortality. The trends of neutrophil engraftment also improved over time. This experience demonstrated that the survival and engraftment rate after CBT for this group has improved over the past 22 years.Subject terms: Acute myeloid leukaemia, Cancer immunotherapy  相似文献   
104.
Life‐threatening cardiac events may be misdiagnosed as acute aortic dissection because of notable symptom mimicry. We report the case of a 72‐year‐old male patient with presentations presumed to be of aortic origin. However, surgery revealed posterior free‐wall perforation in the left ventricle caused by the occlusion of an obtuse marginal branch.  相似文献   
105.
In order to determine whether 5-[bis(carboxymethyl) amino]-2-carboxy4-cyano-3-thiopheneacetic acid distrontium salt (S12911-2) inhibits bone resorption by acting on the differentiation and/or function of osteoclasts, its effects were assessed on the 1,25-dihydroxyvitamin D(3)-induced expression of carbonic anhydrase II and vitronectin receptor in chicken bone marrow cells, and on the resorbing activity of authentic rat osteoclasts cultured on bone slices. S12911-2 dose-dependently inhibited, after a 6-day exposure, the expression of carbonic anhydrase II and vitronectin receptor in stimulated osteoclasts (46% and 40%, respectively, at 10(-3) M Sr(2+), P<0.05). A pre-incubation of bone slices with S12911-2 induced a dose-dependent inhibition of bone resorbing activity from 32% at 10(-4) M Sr(2+) to 66% at 10(-3) M Sr(2+) (P<0.05 in each case). A continuous incubation (10(-3) M Sr(2+)) induced a greater inhibition of bone resorbing activity (73%, P<0.05). The inhibition of bone resorption obtained specifically with S12911-2 is related to an inhibition of the differentiation and resorbing activity of the osteoclasts.  相似文献   
106.
The clinical features and morphological findings in 31 Japanese infants with trisomy 18 are presented. The majority were small-for-date infants. There was no sex predominance in our series, as opposed to male female ratios of 1:3 reported in the literature. The average age at death was greater in females than in males. Cardiovascular anomalies were consistently present; ventricular septar defect and patent ductus arteriosus being the most common malformations. Various other internal malformations including the Arnold-Chiari malformation were observed.  相似文献   
107.
Background and PurposeAmyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease. Selective deficiency of edited adenosine deaminase acting on RNA 2 (ADAR2), a key molecule in the acquisition of Ca2+ resistance in motor neurons, has been reported in sporadic ALS (sALS) spinal motor neurons. Since ADAR2 activity is positively regulated by prolyl isomerase Protein never in mitosis gene A interacting-1 (Pin1), a known phosphorylation-dependent peptidyl-prolyl cis/trans isomerase, we investigated Pin1 expression in spinal motor neurons in sALS.MethodsSpecimens of the spinal cord were obtained from the lumbar region in eight sALS patients and age-matched five controls after postmortem examinations. The specimens were double stained with anti-Pin1 and anti-TAR DNA-binding protein of 43 kDa (TDP-43) antibodies, and examined under a fluorescence microscope.ResultsThis study analyzed 254 and 422 spinal motor neurons from 8 sALS patients and 5 control subjects, respectively. The frequency of motor neurons with high cytoplasmic Pin1 expression from the spinal cord did not differ significantly between sALS specimens without cytoplasmic TDP-43 inclusions and control specimens. However, in sALS specimens, neurons for which the Pin1 immunoluminescence intensity in the cytoplasm was at least twice that in the background were more common in specimens with cytoplasmic TDP-43 inclusions (p<0.05 in χ2 test).ConclusionsIn sALS, neurons with higher expression levels of Pin1 levels had more TDP-43 inclusions. Despite the feedback mechanism between Pin1 and ADAR2 being unclear, since Pin1 positively regulates ADAR2, our results suggest that higher Pin1 expression levels in motor neurons with TDP-43 pathology from sALS patients represent a compensatory mechanism.  相似文献   
108.

Purpose

To examine the properties of corneas tissue-engineered with cultured human corneal endothelial cells (HCEC) and human corneal stroma.

Methods

Primary HCEC cultures were established from endothelial cell layer explants and propagated on culture dishes coated with bovine corneal endothelial extracellular matrix. A cell suspension of HCEC at the fifth passage was transferred onto human corneal stroma deprived of endothelial cells, and the corneas were gently centrifuged to enhance cell attachment. The cell density of the tissue-engineered corneas was examined after staining with alizarin red and trypan blue. The tissue-engineered corneas were histologically examined by light and electron microscopy. The pump function of the tissue-engineered corneas was measured using an Ussing chamber.

Results

The mean endothelial cell density of four tissue-engineered corneas was 2380 ± 264 cells/mm2 (mean ± SD). HCEC on the tissue-engineered corneas had a morphology similar to HCEC in vivo. The pump function parameters of the tissue-engineered corneas were 55%–75% of those of normal corneas.

Conclusions

HCEC on the tissue-engineered corneas have morphology and cellular density similar to HCEC in vivo, whereas the pump function of the tissue-engineered corneas was lower than in normal corneas. Jpn J Ophthalmol 2005;49:448–452 © Japanese Ophthalmological Society 2005  相似文献   
109.
Massive cystic lymphangiomas of a fetus   总被引:1,自引:0,他引:1  
We present a fetus with progressive massive subcutaneous lymphangiomas leading to intrauterine death. A 28-year-old woman was referred to our hospital because of a precordial cystic mass of the fetus. An ultrasound revealed lymphangiomas extending from bilateral axillae to the anterior chest wall. At 18 weeks' gestation, amniocentesis was performed and the karyotype of the fetus was found to be normal 46, XY. Thereafter the lesions increased in size gradually and spread over the body. Amniotic fluid decreased, pericardial, and pleural effusion appeared, and cardiomegaly became evident. The fetus died in utero at 25 weeks' gestation. Postmortem examination revealed a male fetus surrounded with multicystic soft masses spreading over the body, and syndactyly (left third and fourth fingers) was present. Histologically, a number of irregularly dilated lymphatics extended through subcutaneous tissues to the skeletal muscles. No communications between the cysts and the thoracic or abdominal cavity existed, and no lymphatic dilations in the viscera were confirmed. As far as we know, such conditions have rarely been reported. Considering that in previous literature, a favorable prognosis of a fetus with an atypically located (lateral cervical or non-cervical) lymphangioma with a normal karyotype has been reported, our case may be included in a distinct pathological entity. When we find a lymphangioma in a fetus, careful follow-up by ultrasound is mandatory.  相似文献   
110.
Tranexamic acid (TXA) reduces the risk of bleeding trauma death without altering the need for blood transfusion. We examined the effects of TXA on coagulation and fibrinolysis dynamics and the volume of transfusion during the early stage of trauma. This subanalysis of a prospective multicenter study of severe trauma included 276 patients divided into propensity score–matched groups with and without TXA administration. The effects of TXA on coagulation and fibrinolysis markers immediately at (time point 0) and 3 hours after (time point 3) arrival at the emergency department were investigated. The transfusion volume was determined at 24 hours after admission. TXA was administered to the patients within 3 hours (median, 64 minutes) after injury. Significant reductions in fibrin/fibrinogen degradation products and D-dimer levels from time points 0 to 3 in the TXA group compared with the non-TXA group were confirmed, with no marked differences noted in the 24-hour transfusion volumes between the 2 groups. Continuously increased levels of soluble fibrin, a marker of thrombin generation, from time points 0 to 3 and high levels of plasminogen activator inhibitor-1, a marker of inhibition of fibrinolysis, at time point 3 were observed in both groups. TXA inhibited fibrin(ogen)olysis during the early stage of severe trauma, although this was not associated with a reduction in the transfusion volume. Other confounders affecting the dynamics of fibrinolysis and transfusion requirement need to be clarified.  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