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   2727篇
  免费   142篇
  国内免费   11篇
耳鼻咽喉   34篇
儿科学   60篇
妇产科学   164篇
基础医学   376篇
口腔科学   104篇
临床医学   270篇
内科学   486篇
皮肤病学   31篇
神经病学   263篇
特种医学   88篇
外科学   275篇
综合类   33篇
一般理论   1篇
预防医学   199篇
眼科学   146篇
药学   161篇
中国医学   11篇
肿瘤学   178篇
  2024年   5篇
  2023年   29篇
  2022年   98篇
  2021年   126篇
  2020年   72篇
  2019年   103篇
  2018年   125篇
  2017年   93篇
  2016年   100篇
  2015年   94篇
  2014年   143篇
  2013年   159篇
  2012年   269篇
  2011年   264篇
  2010年   141篇
  2009年   118篇
  2008年   158篇
  2007年   174篇
  2006年   118篇
  2005年   118篇
  2004年   106篇
  2003年   87篇
  2002年   65篇
  2001年   13篇
  2000年   12篇
  1999年   9篇
  1998年   10篇
  1997年   9篇
  1996年   9篇
  1995年   4篇
  1994年   7篇
  1993年   6篇
  1992年   5篇
  1991年   1篇
  1990年   2篇
  1989年   3篇
  1987年   1篇
  1986年   3篇
  1984年   1篇
  1983年   3篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1976年   2篇
  1975年   1篇
  1973年   3篇
  1971年   1篇
  1969年   1篇
  1968年   1篇
排序方式: 共有2880条查询结果,搜索用时 15 毫秒
1.
Effective antitumor photodynamic therapy (PDT) may be related to damage of vasculature within the tumor. The purpose of this study was to determine if tumor cells secrete factors that stimulate proliferation of human umbilical vein endothelial cells (HUVEC) and result in enhanced sensitivity of HUVEC to aluminum-sulfonated phthalocyanine (AISPc)-PDT. Three human tumor cell lines—pharyngeal squamous carcinoma, colonic carcinoma, and mammary carcinoma—were used in this study. Co-culture of HUVEC and either squamous carcinoma or colonic carcinoma, but not mammary carcinoma, significantly increased HUVEC proliferation and AlSPc-PDT mediated cell damage. In addition, supernatant from squamous carcinoma and colonic carcinoma cultures also stimulated HUVEC proliferation and sensitivity to AISPc-PDT. Both supernatant and cell lysate from squamous carcinoma cells contained angiogenic factors consistent with basic and acidic fibroblast growth factors, as evidenced by Western blot analysis and BALB/c 3T3 fibroblast cell proliferation assays. Collectively, these results suggest that selected tumor cell lines produce angiogenic factors that induce HUVEC proliferation and subsequently enhance sensitivity to AISPc-PDT. © 1994 Wiley-Liss, Inc.  相似文献   
2.
MRI studies of first-pass contrast enhancement with polylysine-Gd-DTPA and myocardial tagging using spatial modulation of magnetization (SPAMM) were performed to assess the feasibility of a combined regional myocardial blood flow and 2D deformation exam. Instrumented closed-chest dogs were imaged at a baseline control state (Cntl) followed by two interventions: moderate coronary stenosis (St) achieved by partial occlusion of the left anterior descending (LAD) and moderate coronary stenosis with dobutamine loading (StD). Hypoperfusion of the anterior region (ANT) of the myocardium (LAD distribution) relative to the posterior wall (POS) based on the upslope of the signal intensity time curve from the contrast-enhanced MR images was demonstrated only with dobutamine loading (ANT:POS Cntl=1.077 ± 0.15 versus ANT:POS StD=0.477 ± 0.11, P<0.03) and was confirmed with radio-labeled microspheres measurements (ANT:POS Cntl=1.18 ± 0.2 ml/min/g versus ANT:POS StD=0.44 ± 0.1 ml/min/g; P<0.002). Significant changes in regional myocardial shortening were only seen in the StD state (P<0.02); the anterior region showed impaired myocardial shortening with dobutamine loading (P=NS), whereas the nonaffected POS region showed a marked increase in shortening when compared with Cntl (Cntl=0.964 ± 0.02 versus StD=0.884 ± 0.03; P<0.001). These results demonstrate that an integrated quantitative assessment of regional myocardial function and semiquantitative assessment of myocardial blood flow can be performed noninvasively with ultrafast MRI.  相似文献   
3.
The acid phosphatase (ACP1) locus codes for a low molecular weight protein tyrosine phosphatase (LMPTP) that is found ubiquitously in human tissues. The *A allele of the ACP1 gene is associated with lower total enzymatic activity than the *B and *C alleles. An association between the *A allele and extreme values of body-mass-index (BMI) and dyslipidemia has previously been described in several samples of obese subjects from the Italian population. In the present study, we investigated the relationship between ACP1 *A allele genotypes (*A/*A, *A/*B, and *A/*C) and non-*A allele genotypes (*B/*B, *B/*C, and *C/*C) and metabolic variables in 277 Caucasian post-menopausal subjects consisting of 82 non-obese subjects (BMI/=35) subjects. ACP1 genotypes were found to be significantly associated with total cholesterol (p相似文献   
4.
β-Aminopropionitrile as free base (BAPN) was applied onto the incised or intact skin of rats at the dose of 5, 20, 100, and 200 μl for 9 days, twice daily. Breaking strength of the skin wound or intact skin was significantly reduced at doses of 20 μl and higher; body weight growth was significantly retarded at the two highest dosages. It is concluded that at a given dose (20 μl) collagen polymerization (evaluated by reduced breaking strength and increased extractability of collagen) was specifically inhibited by BAPN. Furthermore, no evidence of topical or general toxic effects were observed, as reflected in histology, body weight growth, and behavior of the rats. Acute LD50 of BAPN base and fumarate, administered either ip or topically, was determined in mice. While BAPN base in ip administration shows LD50 of 1.15 g/kg, in cutaneous application it is more than 12.8 g/kg. It is suggested that topically applied BAPN base is percutaneously absorbed and affects collagen polymerization in the skin and adjacent tissues.  相似文献   
5.
We present an empowerment model that fosters strengths and promotes positive identity development among adolescent females of color. Race, ethnicity, gender, and socioeconomic status are integrated in an African American context. A case study illustrates a strength-based approach to conceptualizing and treating a young, Black adolescent female in her cultural context. We conclude with clinical implications for using an empowerment-based approach in psychotherapy with culturally diverse adolescent females.  相似文献   
6.
HIV-1 p24 antigen testing was introduced to increase sensitivity in the early detection of HIV infection in blood donors. Since the introduction of HIV-1 p24 antigen testing in Saudi Arabia, we have failed to detect a single positive case. Over a three-year period, only four indeterminates were detected out of 24,654 blood donors. All four proved negative by confirmatory testing. Based on this experience, we believe that resources would be better directed to pooled nucleic acid testing and that p24 serological testing should be abandoned.  相似文献   
7.
Polyorchidism is usually diagnosed incidentally when the patient undergoes imaging or surgery for some other reason. Although we are facing lack of evidence in different steps of diagnostic and therapeutic workup of these patients, this disorder is usually considered benign, not requiring any intervention. We report the case of a man complaining of a palpable mass in his scrotum. We evaluated the patient using ultrasound, MRI and serum tumour marker level measurement. The patient was finally diagnosed with polyorchidism (three testes). For the management, we recommended annual physical examination, US examination and serum tumour marker level measurement.  相似文献   
8.
With the increase in the importance of using green energy sources to meet the world''s energy demands, attempts have been made to push perovskite solar cell technology toward industrialization all around the world. Improving the properties of perovskite materials as the heart of PSCs is one of the methods to fabricate favorable photovoltaic (PV) solar cells based on perovskites. Here, cadmium chloride (CdCl2) was used as an additive source for the perovskite precursor to improve its PV properties. Results indicated CdCl2 improves the perovskite growth and tailors its crystalline properties, suggesting boosted charge transport processes in the bulk and interfaces of the perovskite layer with electron–hole transport layers. Overall, by incorporation of 1.0% into the MAPbI3 layer, a maximum power conversion efficiency of 15.28% was recorded for perovskite-based solar cells, higher than the 12.17% for the control devices. The developed method not only improved the PV performance of devices but also boosted the stability behavior of solar cells due to the passivated domain boundaries and enhanced hydrophobicity in the CdCl2-based devices.

With the increase in the importance of using green energy sources to meet the world''s energy demands, attempts have been made to push perovskite solar cell technology toward industrialization all around the world.  相似文献   
9.
Myxoinflammatory fibroblastic sarcoma (MIFS) is an uncommon soft tissue sarcoma. We present two cases of MIFS: A known case of Hodgkin‘s lymphoma presented with hand mass; a recurrence of MIFS with a history of chronic lymphocytic leukemia.  相似文献   
10.
Correction for ‘Synthesis and characterization of AFe2O4 (A: Ni, Co, Mg)–silica nanocomposites and their application for the removal of dibenzothiophene (DBT) by an adsorption process: kinetics, isotherms and experimental design’ by Fahimeh Vafaee et al., RSC Adv., 2021, 11, 22661–22676, https://doi.org/10.1039/D1RA02780H.

The authors regret an error in Fig. 4 where a section of the XRD for 4(a) and (b) is identical.Open in a separate windowFig. 4(a) The XRD pattern of sample 3 after adsorption of DBT. (b) The XRD pattern of sample 3 before adsorption of DBT.The authors have repeated the experiment and provided new data for Fig. 4. An independent expert has viewed the new data and has concluded that it is consistent with the discussions and conclusions presented. The correct Fig. 4 is shown below:The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.  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