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   5862篇
  免费   425篇
  国内免费   35篇
耳鼻咽喉   61篇
儿科学   181篇
妇产科学   134篇
基础医学   713篇
口腔科学   211篇
临床医学   455篇
内科学   1357篇
皮肤病学   147篇
神经病学   248篇
特种医学   111篇
外国民族医学   7篇
外科学   882篇
综合类   221篇
一般理论   3篇
预防医学   477篇
眼科学   110篇
药学   568篇
中国医学   73篇
肿瘤学   363篇
  2023年   81篇
  2022年   51篇
  2021年   339篇
  2020年   174篇
  2019年   235篇
  2018年   228篇
  2017年   184篇
  2016年   245篇
  2015年   233篇
  2014年   283篇
  2013年   339篇
  2012年   493篇
  2011年   547篇
  2010年   284篇
  2009年   227篇
  2008年   338篇
  2007年   256篇
  2006年   288篇
  2005年   267篇
  2004年   218篇
  2003年   181篇
  2002年   164篇
  2001年   40篇
  2000年   50篇
  1999年   48篇
  1998年   40篇
  1997年   24篇
  1996年   27篇
  1995年   28篇
  1994年   22篇
  1993年   22篇
  1992年   24篇
  1991年   17篇
  1990年   27篇
  1989年   29篇
  1988年   20篇
  1987年   31篇
  1986年   20篇
  1985年   11篇
  1984年   12篇
  1983年   15篇
  1982年   16篇
  1981年   12篇
  1980年   9篇
  1979年   13篇
  1977年   11篇
  1975年   8篇
  1972年   7篇
  1971年   8篇
  1970年   13篇
排序方式: 共有6322条查询结果,搜索用时 328 毫秒
41.
In the present work genomic DNAs from nine primary breast cancers and transformed human breast epithelial cell lines obtained by treatment of MCF 10F, a spontaneously immortalized human breast epithelial cell line, with benzo(a)pyrene (BP) or 7,12 dimethyl benz(a)anthracene (DMBA), were used for genomic scanning. The treatment of MCF 10F with BP gave rise to different clones designated BP1 and BP1E, the latter being a tumorigenic cell line. Treatment with DMBA gave rise to D3 and D3-1 clones. The clones D3-1 and BP1 have been transfected with the plasmid pH06T1 containing the mutated c-Ha-ras oncogene resulting in the D3-1Tras and BP1T-ras cell lines, that are highly tumorigenic in SCID mice. Genomic DNA are separately hybridized to two different probes representing different families of human endogenous retrovirus like sequences (RTLV-H and HERV-K LTR). The technique of genomic scanning allows the mapping of each tumor or cell line and comparison with its counterpart obtained from the adjacent normal tissue of the same patient or with the untreated MCF 10F cells. DNA changes such as deletions, amplifications and/or rearrangements were detected in 5 of the tumor pairs studied. We have identified genomic alterations that involved amplification of a 10 kb band in the transformed cell lines. The cell lines D3-1Tras and BP1T-ras show, in addition, the presence of a second band of 4.5 kb in size. A third band of 500 bp size was found in clones D3-1 and BP1E that have a more aggressive behavior in vitro than their precursors D3 and BP1 cells respectively. In conclusion the present report indicates that genomic scanning detects DNA aberrations in primary primary tumors and in human breast epithelial cells transformed with chemical carcinogens and/or oncogene transfection that are not present in their normal counterpart. These results further indicate that detection of endogenous retrovirus elements may help in genome mapping and can be a useful tool for detecting genomic changes in the preliminary screening of DNA extracted from primary breast cancer and transformed cells.  相似文献   
42.
Fifty four patients presenting by huge splenomegaly were admitted to Tropical Medicine Department, El-Minia University Hospital. Tissue biopsy revealed pure bilharziasis due to S. hematobium in 10 (19%) cases, liver cirrhosis in 23 (42%), mixed schistosomiasis and cirrhosis in 8 (15%), hepatoma in 3 (6%), lymphoma in 6 (11%) and hematological diseases in the form of chronic myeloid leukemia in 2 (3.5%) and thalassemia major in 2 (3.5%) cases. The sensitivity and specificity of abdominal ultrasonography was 100% and 97% in cases of schistosomiasis, 100% and 100% in cases of hepatoma, 87% and 100% in cases of liver cirrhosis, 33% and 100% in cases of lymphoma respectively. There was a positive significant correlation between endoscopic variceal grading, portal vein diameter, splenic vein diameter, size of the spleen and the grading of the portal tract thickenings. The pathological and ultrasonographic diagnosis was the same in 38 (70%) cases. Splenogram was characteristic but not diagnostic in cases of schistosomiasis and liver cirrhosis. It was diagnostic and similar to peripheral blood picture in the 2 cases of chronic myeloid leukemia and was normal in cases of thalassemia major. Splenic aspiration was able to diagnose all cases of lymphomas. It can be considered as a useful adjunct to the usual diagnostic procedures, both in staging and follow up, especially in cases presenting only by splenomegaly.  相似文献   
43.
44.
Following systemic administration of the noradrenaline (NA) neurotoxin, DSP4 (50 mg/kg), rats were found to be retarded in the rate at which they acquired the "right-turn" running response in a modified T-maze choice situation, as measured by the total number of errors per session and median latency to reach the goal box. Desipramine (DMI, 20 mg/kg), injected 30 min before DSP4 blocked the acquisition retardation. DSP4 was found to have a short-lasting effect upon spontaneous motor activity, while food and water intake recovery was complete within 7 days of the injection. Both the NA-accumulation data and endogenous NA concentrations indicated profound NA, but not 5-hydroxytryptamine (5-HT) and dopamine (DA), depletions in the cortex, hippocampus and cerebellum. These data seem to confirm the role of the locus coeruleus-noradrenaline (LC-NA) system in an instrumental learning situation.  相似文献   
45.
46.
47.
BACKGROUND AND PURPOSE: Single agent mitomycin c (MMC) has been shown to improve the outcome of radiotherapy in single institution trials. In order to confirm these findings in a broader worldwide setting, the International Atomic Energy Agency (IAEA) initiated a multicentre trial randomising between radiotherapy alone versus radiotherapy plus MMC. MATERIAL AND METHODS: Patients with advanced head and neck cancer were treated with primary curative radiotherapy (66 Gy in 33 fractions with five fractions per week) +/-a single injection (15 mg/m(2)) of MMC at the end of the first week of radiotherapy. Stratification parameters were tumour localization, T-stage, N-stage, and institution. A total of 558 patients were recruited in the trial from February 1996 to December 1999. Insufficient accrual and reporting led to the exclusion of three centres. The final study population consisted of 478 patients from seven centres. Patients had stage III (n=223) or stage IV (n=255) squamous cell carcinoma of the oral cavity (n=230), oropharynx (n=140), hypopharynx (n=65) or larynx (n=43). Prognostic factors like age, gender, site, size, differentiation and stage were well balanced between the two arms. RESULTS: The haematological side effects of MMC were very modest (<5% grade 3-4) and did not require any specific interventions. Furthermore, MMC did not enhance the incidence or severity of acute and late radiation side effects. Confluent mucositis and dry skin desquamation was common, occurring in 56% and 62% of patients, respectively. The overall 3-year primary locoregional tumour control, disease-specific and overall survival rates were 19, 36 and 30%, respectively. Gender, haemoglobin drop, tumour site, tumour and nodal stage were significant parameters for loco-regional tumour control. There was no significant effect of MMC on locoregional control or survival, except for the 161 N0 patients, where MMC resulted in a better loco-regional control (3-year estimate 16% vs. 29%, P=0.01). CONCLUSIONS: The study did not show any major influence of MMC on loco-regional tumour control, survival or morbidity after primary radiotherapy in stage III-IV head and neck cancer except in N0 patients where loco-regional control was significantly improved.  相似文献   
48.
49.
Glomus vagale are rare vascular tumours of the paraganglion cells of the vagus nerve, and they usually occur in the carotid space. Tumours can be familial, multicentric, malignant but rarely hormonally active. A rare case is reported of glomus vagale presenting as a supraclavicular mass.  相似文献   
50.
Acanthamoeba is an opportunistic protozoan pathogen and known to be one of the most ubiquitous organisms, play a vital role in ecosystem, and recognized to cause blinding keratitis and rare but fatal granulomatous encephalitis involving the central nervous system with a very poor prognosis. This is due to limited availability of effective anti-Acanthamoeba drugs. The objective of the present study was to determine the efficacy of methanolic plants crude extracts on the viability and biological properties of Acanthamoeba castellanii (T4 genotype) and its cytotoxic effects on human corneal epithelial cells (HCEC). Using HCEC, it was observed that Acanthamoeba exhibited binding (>90 %) and cytotoxicity (>80 %) to host cells. However, plant crude extracts remarkably inhibited more than 70 and 60 % of Acanthamoeba binding and cytotoxicity to HCEC, respectively. It was further established that crude extracts (ranging from 0.1 to 1.5 mg/ml) exhibited amoebicidal effects, i.e., >50 % of trophozoites were killed/reduced at maximum dose (1.5 mg/ml) within 1 h incubation. However, the residual subpopulation remained static over longer incubations. Furthermore, growth assay demonstrated crude extracts inhibited >50 % Acanthamoeba numbers up to 7 days. Our results confirmed that plant crude extracts has inhibitory effects on Acanthamoeba growth and viability. Overall, these findings revealed that tested plant extracts is inhibitory to Acanthamoeba properties associated with pathogenesis. To the best of our knowledge, our findings demonstrated for the first time that selected methanol plant crude extracts exhibits inhibitory effects on biological properties of Acanthamoeba without any toxic effects on HCEC cells in vitro.  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