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   1041篇
  免费   40篇
  国内免费   4篇
耳鼻咽喉   5篇
儿科学   56篇
妇产科学   43篇
基础医学   110篇
口腔科学   12篇
临床医学   63篇
内科学   235篇
皮肤病学   7篇
神经病学   102篇
特种医学   58篇
外科学   184篇
综合类   28篇
预防医学   33篇
眼科学   11篇
药学   42篇
  1篇
中国医学   3篇
肿瘤学   92篇
  2024年   9篇
  2023年   9篇
  2022年   16篇
  2021年   18篇
  2020年   14篇
  2019年   29篇
  2018年   26篇
  2017年   21篇
  2016年   28篇
  2015年   25篇
  2014年   29篇
  2013年   50篇
  2012年   69篇
  2011年   74篇
  2010年   31篇
  2009年   38篇
  2008年   51篇
  2007年   55篇
  2006年   51篇
  2005年   34篇
  2004年   57篇
  2003年   50篇
  2002年   41篇
  2001年   29篇
  2000年   34篇
  1999年   24篇
  1998年   6篇
  1997年   6篇
  1996年   10篇
  1995年   7篇
  1994年   6篇
  1992年   7篇
  1991年   5篇
  1990年   10篇
  1989年   11篇
  1988年   7篇
  1987年   9篇
  1986年   7篇
  1985年   16篇
  1984年   8篇
  1983年   7篇
  1982年   5篇
  1981年   5篇
  1980年   3篇
  1979年   9篇
  1977年   3篇
  1976年   3篇
  1974年   4篇
  1973年   4篇
  1971年   4篇
排序方式: 共有1085条查询结果,搜索用时 15 毫秒
61.

Background  

Esophageal cancer ranks eighth in order of cancer occurrence. Its lethality primarily stems from inability to detect the disease during the early organ-confined stage and the lack of effective therapies for advanced-stage disease. Moreover, the understanding of molecular processes involved in esophageal cancer is not complete, hampering the development of efficient diagnostics and therapy. Efforts made by the scientific community to improve the survival rate of esophageal cancer have resulted in a wealth of scattered information that is difficult to find and not easily amendable to data-mining. To reduce this gap and to complement available cancer related bioinformatic resources, we have developed a comprehensive database (Dragon Database of Genes Implicated in Esophageal Cancer) with esophageal cancer related information, as an integrated knowledge database aimed at representing a gateway to esophageal cancer related data.  相似文献   
62.
Previous results have shown that salmon calcitonin (sCT), a peptide in rat brain and pituitary gland, inhibits basal and TRH-stimulated PRL release and reduces PRL mRNA levels in isolated anterior pituitary cells of adult rats in culture. Rat milk contains a variety of neuropeptides and hormones, some of which are absorbed in bioactive form to exert endocrine influences in the developing offspring. The present studies were undertaken to investigate whether a CT-like peptide is present in rat milk. Circulating PRL levels in neonatal rats are low, and there is an abrupt increase in the basal secretion of this hormone at weaning. A second objective was to examine whether CT plays a role in the regulation of PRL secretion in neonatal animals. A sensitive and specific RIA for sCT was developed and used to assay rat milk on various days of lactation for sCT-like immunoreactivity. sCT-like activity was present in the water-soluble (infranatant) fraction of milk throughout lactation in concentrations as high as 1589 pg/ml. There were no statistically significant differences in immunoreactive levels of the peptide in milk samples from different days of lactation. sCT-like immunoreactivity in rat milk infranatant coeluted with synthetic sCT on reverse phase HPLC, and these HPLC fractions inhibited basal PRL release when added to cultures of anterior pituitary cells. This inhibition of PRL release by the sCT-immunoreactive HPLC fractions was comparable to that exerted by equivalent concentrations of synthetic sCT. Newborn rats were injected sc with 10 microliters normal rabbit serum or anti-sCT serum from the day of birth until postpartum day 10. The rats were killed on day 11, and their sera were analyzed for PRL. Anti-sCT-injected rats showed a significant increase in serum PRL levels compared to those in untreated or normal serum-treated rats. These results demonstrate that a CT-like peptide, which is a potent inhibitor of PRL release, is present in rat milk throughout lactation, and that passive immunization with a highly specific anti-sCT serum leads to an increase in serum PRL levels in neonatal rats. CT, possibly of milk origin, may be a physiologically relevant PRL-inhibiting factor during the neonatal period.  相似文献   
63.
64.
65.
The purpose of this study was to apply photoacoustic imaging (PAI), a relatively new imaging method, to non-invasively map neurovascular dynamics in salivary glands. Dynamic PAI with co-registered ultrasound (US) was performed in mice to monitor salivary gland hemodynamics in response to exogenous muscarinic receptor stimulation (pilocarpine) and blockade (atropine). Pilocarpine increased salivary gland oxygen saturation (%sO2) within minutes after administration, which was abrogated by atropine. A significant correlation was observed between change in %sO2 measured by PAI and saliva secretion. PAI is a novel imaging method that can be used for functional assessment of neurovascular dynamics in salivary glands.  相似文献   
66.
Metabolism and elimination of rhodamine 123 in the rat   总被引:1,自引:0,他引:1  
Summary Little is known of the pharmacology of rhodamine 123 (RH-123), an agent reported to have carcinoma-selective experimental antitumor activity. Accordingly, using a high-performance liquid chromatographic assay system with fluorescence detection, we examined the plasma decay and the biliary and urinary elimination of parent drug and metabolites in female Sprague-Dawley rats receiving RH-123 at an intravenous dose (5 mg/kg) equivalent to the therapeutic dose used in murine tumor models. Following drug administration to unconscious animals, plasma levels of drug-associated fluorescence fell in a triphasic manner (t1/2, 15 min; t1/2, 1 h; t1/2, 4.7 h). In plasma, unchanged drug predominated but lower levels of the deacylated metabolite rhodamine 110 (RH-110) and two unknowns were also detectable throughout the study. Drug fluorescence was recovered extensively in both urine and bile. In unconscious animals with ureteral cannulae, urinary excretion (11.4% of the dose in 6 h) occurred predominantly as unchanged RH-123 (97% of the total), with low levels of RH-110 (2.4%) and two unknowns (<0.6% combined) also being present. Similarly dosed conscious animals (without surgical intervention) housed in metabolic cages showed a comparable pattern of urinary excretion, with 11.9% of the drug dose being recovered in 6 h and 21.9%, by 48 h. Biliary drug elimination accounted for 8% of the delivered dose in 6 h in unconscious animals and for 11% by 36 h in conscious animals fitted with biliary cannulae. In contrast to urinary excretion, in which unchanged drug predominated, only 50% of the fluorescence recovered in bile was attributable to RH-123. The remainder was due to a number of products that were detectable throughout the study. Of these, one present at significant levels was identified as a glucuronide conjugate of RH-123, based on the liberation of parent drug when the purified metabolite was incubated with -glucuronidase or hydrolyzed with 1 N hydrochloric acid. Further studies with a radiolabeled form of RH-123 are necessary to establish the identity of the remaining unknowns disclosed in this work.This work was supported in part by research grants CA 44890 (T.W.S.) and CA 37082 (M.I.) from the National Cancer Institute, National Institutes of Health, United States Public Health Service  相似文献   
67.
A novel, sensitive, stability-indicating HPLC method has been developed for the quantitative estimation of Tolperisone-related impurities in both bulk drugs and pharmaceutical dosage forms. Effective chromatographic separation was achieved on a C18 stationary phase with a simple mobile phase combination delivered in a simple gradient programme, and quantitation was by ultraviolet detection at 254 nm. The mobile phase consisted of a buffer and acetonitrile delivered at a flow rate 1.0 ml/min. The buffer consisted of 0.01 M potassium dihydrogen phosphate with the pH adjusted to 8.0 by using diethylamine. In the developed HPLC method, the resolution between Tolperisone and its four potential impurities was found to be greater than 2.0. Regression analysis showed an R value (correlation coefficient) of greater than 0.999 for the Tolperisone impurities. This method was capable of detecting all four impurities of Tolperisone at a level of 0.19 μg/mL with respect to the test concentration of 1000 μg/mL for a 10 µl injection volume. The tablets were subjected to the stress conditions of hydrolysis, oxidation, photolysis, and thermal degradation. Considerable degradation was found to occur in base hydrolysis, water hydrolysis, and oxidation. The stress samples were assayed against a qualified reference standard and the mass balance was found to be close to 100%. The established method was validated and found to be linear, accurate, precise, specific, robust, and rugged.  相似文献   
68.
Evidence of human papilloma virus (HPV) infection was sought in 50 patients with cervical intraepithelial neoplasia (CIN) and 50 controls. Cytologic, colposcopic and histopathological examinations were carried out in each one of them. Cytological evidence of HPV infection was found in 13 cases and two controls. Colposcopic evidence was found in 33 (66%) cases and 17 (34%) controls and histopathological evidence in 35 (70%) patients and 14 (28%) controls. These differences were statistically significant. Colposcopy proved to be a good method of diagnosing HPV infection with a sensitivity of 86% and specificity of 80% compared to histopathologic diagnosis.  相似文献   
69.
PURPOSE: To evaluate the efficacy and toxicity of combination and sequential dose-dense chemotherapy with doxorubicin and docetaxel (Taxotere; Rh?ne-Poulenc Rorer, Collegeville, PA) as primary chemotherapy of breast cancer. PATIENTS AND METHODS: Patients with newly diagnosed stage II or noninflammatory stage III breast cancer were randomly assigned to receive the same total doses of doxorubicin and docetaxel over a 12-week period before definitive surgery. Patients in arm A received sequential therapy with doxorubicin 75 mg/m(2) every 2 weeks for three cycles followed by docetaxel 100 mg/m(2) every 2 weeks for three cycles. Patients in arm B received combination therapy with doxorubicin 56 mg/m(2) plus docetaxel 75 mg/m(2) every 3 weeks for four cycles. Granulocyte colony-stimulating factor was administered on days 2 to 12 of each cycle in both groups. RESULTS: Forty patients were entered onto the trial. Pretreatment tumor size averaged 5.7 cm with clinically positive axillary lymph nodes in 23 patients (57%). As expected, myelosuppression was severe in both groups; however, >/= 80% of planned dose-intensity was delivered. Hand-foot syndrome was more common after sequential therapy. Clinical responses were similar in both groups, with an overall response rate of 87%, including 20% clinical complete remissions. Pathologic complete remission or residual in situ disease only was confirmed in five patients (12.8%). Patients who received sequential therapy had fewer positive lymph nodes (mean, 2.17 v 4.81; P <.037) at definitive surgery. CONCLUSION: Primary chemotherapy with doxorubicin and docetaxel is well tolerated and highly active. A sequential treatment schedule increases toxicity but may result in more substantial lymph node clearance than combination therapy.  相似文献   
70.
Image analysis was used to investigate the prognostic significance of immunostaining for oestrogen receptor (ER), p53 tumour-suppressor protein and tumour cell proliferation (MIB-1) in a random cohort of 200 primary breast cancer patients with between 4 and 7 years of clinical follow-up. Image measurements of the percentage of immunopositive cancer cell nuclei (% positive nuclear area) were recorded for the above tumour features for each patient. Assessment of relative risk using Cox's univariate analysis indicated that tumour size, number of cancer-involved nodes, MIB-1 and ER % positive nuclear area were significantly associated with breast cancer disease outcome, i.e., relapse-free survival and overall survival. In multivariate analysis, tumour size, number of involved nodes, ER and MIB-1 % positive nuclear area were retained as independent predictors of prognosis, depending on the image measurement cut-point used. A prognostic model, which can be used without reference to nodal involvement, was constructed for tumour size, ER cut-point of 30% positive nuclear area and MIB-1 cut-point of 10% positive nuclear area. Kaplan-Meier analysis of this image-based prognostic index identified 4 risk groups with predicted 5-year overall survival rates of 93%, 83%, 76.7% and 61.5%. We conclude that image measurements of ER and proliferative rate can be combined with tumour size to construct a prognostic index which reliably predicts disease outcome in primary breast cancer without knowledge of the nodal status of the patient.  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