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   60546篇
  免费   5041篇
  国内免费   144篇
耳鼻咽喉   678篇
儿科学   1583篇
妇产科学   1221篇
基础医学   8022篇
口腔科学   1254篇
临床医学   6790篇
内科学   12355篇
皮肤病学   1014篇
神经病学   6690篇
特种医学   2904篇
外国民族医学   4篇
外科学   8559篇
综合类   824篇
一般理论   41篇
预防医学   4982篇
眼科学   1400篇
药学   3851篇
  2篇
中国医学   58篇
肿瘤学   3499篇
  2021年   984篇
  2020年   552篇
  2019年   870篇
  2018年   1008篇
  2017年   816篇
  2016年   936篇
  2015年   1027篇
  2014年   1413篇
  2013年   2143篇
  2012年   3119篇
  2011年   3210篇
  2010年   1850篇
  2009年   1691篇
  2008年   2884篇
  2007年   3076篇
  2006年   2924篇
  2005年   2811篇
  2004年   2679篇
  2003年   2445篇
  2002年   2411篇
  2001年   1677篇
  2000年   1665篇
  1999年   1505篇
  1998年   673篇
  1997年   622篇
  1996年   546篇
  1995年   527篇
  1994年   450篇
  1993年   386篇
  1992年   1203篇
  1991年   1203篇
  1990年   1139篇
  1989年   1122篇
  1988年   925篇
  1987年   1054篇
  1986年   975篇
  1985年   977篇
  1984年   784篇
  1983年   638篇
  1982年   414篇
  1981年   378篇
  1980年   382篇
  1979年   715篇
  1978年   537篇
  1977年   466篇
  1976年   466篇
  1975年   412篇
  1974年   540篇
  1973年   470篇
  1972年   397篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This study compared the biomechanics of two methods of joint preparation for ankle fusion with internal fixation. In the first method, the articular cartilage of the ankle joint was removed leaving the joint contour intact. In the second method, parallel flat saw cuts were used to prepare the joint surface for fusion. The specimens were loaded submaximally in a cyclic repetitive fashion before they were loaded to failure. Increasing joint motion occurred as the number of cycles increased. The difference between the two specimen types was not statistically significant during the repetitive tests or when loaded to failure. These results demonstrate both techniques of joint preparation studied are useful and biomechanically sound.  相似文献   
992.
PURPOSE: To determine the efficacy of combination fludarabine and mitoxantrone (FN) in untreated stages III and IV low-grade lymphoma. The major end point was to estimate progression-free survival (PFS) in all eligible patients. PATIENTS AND METHODS: Seventy-eight eligible patients were registered. Chemotherapy courses were administered every 4 weeks with mitoxantrone 10 mg/m2 on day 1 and fludarabine 25 mg/m2 on days 1, 2, and 3 for a total of six to eight cycles. Pneumocystis carinii prophylaxis was required. RESULTS: Seventy-three patients (94%) attained an objective response. Complete remission was demonstrated in 34 patients (44%) and partial remission was demonstrated in 39 patients (50%). With a median follow-up time of 5.5 years, the median PFS was 32 months, with a 4-year PFS rate of 38%. Median survival has not been reached and 88% of all patients are alive at 4 years. The application of the International Prognostic Index and serologic staging showed significant differences in PFS in all risk groups, whereas overall survival was markedly worse for the highest-risk group in either prognostic model. Three prior Southwest Oncology Group trials using a regimen of cyclophosphamide, doxorubicin, vincristine, and prednisone or a combination of prednisone, vincristine, methotrexate, cytarabine, cyclophosphamide, etoposide, nitrogen mustard, vincristine, procarbazine, and prednisone in similar patient populations demonstrated comparable clinical outcome, although the 4-year survival for FN was better. FN was well tolerated, but mild to severe reversible myelosuppression was noted. Other complications were rare. CONCLUSION: FN is an effective, safe chemotherapy combination for patients with advanced-stage, low-grade lymphoma. Clinical outcomes were comparable to prior published data using anthracycline-based regimens.  相似文献   
993.
PURPOSE: 10-propargyl-10-deazaaminopterin (PDX) has superior antitumor efficacy in mouse xenograft models, likely attributable to increased uptake by the RFC-1 folate transporter and greater intracellular polyglutamylation. In a previous Phase I trial, stomatitis was the dose-limiting (and only clinically significant) toxicity of PDX. The recommended Phase II dose was 150 mg/m(2) i.v. every 2 weeks. Responses observed in patients with non-small cell lung cancer (NSCLC) in the Phase I trial prompted this Phase II trial. EXPERIMENTAL DESIGN: Patients had stage IIIB or IV NSCLC and either no previous chemotherapy or progression after initial response or stable disease to one previous chemotherapy regimen. Initially, PDX was administered at a dose of 150 mg/m(2) every 2 weeks. However, to decrease the frequency of stomatitis, the last 10 patients were treated at a dose of 135 mg/m(2). We planned to correlate PDX effects with folate and homocysteine levels and the expression of genes associated with folate transport and polyglutamylation. RESULTS: Thirty-nine patients were enrolled, 38 of whom were evaluable for response. Four patients had confirmed, major objective responses (10% based on intent to treat, 95% confidence interval 3-25) lasting 4, 9, 12, and 15 months. Twelve patients (31%) had stable disease. The median survival was 13.5 months. The predicted 1- and 2-year survival rates were 56 and 36%, respectively. Two patients (5%) suffered grade 4 stomatitis, and 6 (15%) had grade 3. No clinically significant myelosuppression occurred. No correlation between homocysteine or serum folate levels and severity of stomatitis was observed. Area under the curve (calculated using a limited sampling model) correlated with mucositis grade. A trend was noted between folate transporter expression and treatment effect. CONCLUSIONS: The broad applicability of this new antifolate with limited toxicity and proven efficacy in NSCLC encourage further development of this compound. Several trials are now underway combining PDX with other chemotherapeutic agents and testing its efficacy in other cancers.  相似文献   
994.
PURPOSE: To test the hypothesis that therapy of intermediate- and high-grade (excluding Burkitt lymphoblastic) lymphoma with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) could be safely dose-intensified with routine filgrastim support. PATIENTS AND METHODS: Eligible patients were those who were previously untreated and who had either bulky stage II, or stage III or IV lymphoma with working formulation histology D, E, F, G, H, or J; performance status < or = 2; and acceptable end organ function. No upper age limit was specified. Therapy was dose-intensified CHOP (CHOP-DI) with filgrastim support. Each course was repeated every 14 days for six planned courses. RESULTS: Eighty-eight eligible patients were treated with CHOP-DI and had a median follow-up of 5.1 years on this phase II study, designated Southwest Oncology Group (SWOG) 9349. The progression-free survival was 51% at 2 years and 41% at 5 years. The overall survival was 60% at 5 years. Three fatal treatment-related events occurred. One patient with myelodysplastic syndrome was reported. CONCLUSION: Treatment with CHOP-DI can be safely administered in the cooperative group setting and results in improved survival. Estimated overall survival at 5 years was 14% better than that of patients treated with standard-dose CHOP in an earlier SWOG study, although progression-free survival of 60% at 2 years-the prespecified end point-was not achieved. CHOP-DI, given every 2 weeks at escalated doses, is a strategy that should be tested in a future randomized clinical trial in lymphoma.  相似文献   
995.
PURPOSE: This phase III randomized trial evaluated survival as well as neurologic and neurocognitive function in patients with brain metastases from solid tumors receiving whole-brain radiation therapy (WBRT) with or without motexafin gadolinium (MGd). PATIENTS AND METHODS: Patients were randomly assigned to 30 Gy of WBRT +/- 5 mg/kg/d MGd. Survival and time to neurologic progression determined by a blinded events review committee (ERC) were coprimary end points. Standardized investigator neurologic assessment and neurocognitive testing were evaluated. RESULTS: Four hundred one (251 non-small-cell lung cancer) patients were enrolled. There was no significant difference by treatment arm in survival (median, 5.2 months for MGd v 4.9 months for WBRT; P =.48) or time to neurologic progression (median, 9.5 months for MGd v 8.3 months for WBRT; P =.95). Treatment with MGd improved time to neurologic progression in patients with lung cancer (median, not reached for MGd v 7.4 months for WBRT; P =.048, unadjusted). By investigator, MGd improved time to neurologic progression in all patients (median, 4.3 months for MGd v 3.8 months for WBRT; P =.018) and in lung cancer patients (median, 5.5 months for MGd v 3.7 months for WBRT; P =.025). MGd improved neurocognitive function in lung cancer patients. CONCLUSION: The overall results did not demonstrate significant differences by treatment arm for survival and ERC time to neurologic progression. Investigator neurologic assessments demonstrated an MGd treatment benefit in all patients. In lung cancer patients, ERC- and investigator-determined time to neurologic progression demonstrated an MGd treatment benefit. MGd may improve time to neurologic and neurocognitive progression in lung cancer.  相似文献   
996.
PURPOSE: In this single institution Phase II trial, we evaluated the efficacy of the vitamin D analogue, 1alpha-OH-D(2), in patients with advanced hormone-refractory prostate cancer. Experimental Design: The patients initially received 1alpha-OH-D(2) at 12.5 micro g p.o. every day, which was dose adjusted for hypercalcemia. Given the cytostatic nature of the drug, the primary study end point was progression-free survival for a minimum of 6 months. The secondary end point was further characterization of drug toxicity. RESULTS: A total of 26 patients was enrolled. Using the intent-to-treat population, stable disease was seen for an average of 19.2 weeks (median 12 weeks, range 3-108 weeks). Twenty patients were evaluable for response. The one patient that achieved disease stabilization for >2 years elected to come off-study because of patient preference. His last disease evaluation showed no evidence of progression. No objective responses were seen. Previous and ongoing clinical observations strongly imply that PSA could be a misleading surrogate marker for clinical effect with this type of drug. Therefore, prostate-specific antigen was not used as a marker for disease response. Toxicity was as expected with mild hypercalcemia and associated symptoms like constipation and prerenal azotemia seen in some patients. Six (30%) evaluable patients experienced stable disease for >6 months, suggesting possible cytostatic activity. CONCLUSION: The results of this and other trials suggest further clinical investigation in this disease with vitamin D analogues alone or in combination with other agents, such as chemotherapy, should be pursued.  相似文献   
997.
998.
The authors hypothesized that nitric oxide is induced by a brief period of ischemia/reperfusion (ischemic preconditioning, IPC) on postoperative day (POD) 1, and that this released nitric oxide is responsible for initiating a delayed microvascular protection against a prolonged period of ischemia in skeletal muscle on POD day 2. The cremaster muscle of male Sprague-Dawley rats underwent 4 hr of ischemia, and then 60 min of reperfusion. IPC consisted of 45 min of ischemia but was done 24 hr before the prolonged ischemia. Local intraarterial infusion of sodium nitroprusside (SNP, a donor of nitric oxide) or Nw-nitro-L-arginine (L-NA, a nonselective nitric oxide synthase antagonist) were also given 24 hr before prolonged ischemia. Arteriole diameters and capillary perfusion were measured using intravital microscopy. Four groups were compared: 1) control; 2) IPC; 3) SNP + sham IPC; and 4) L-NA + IPC. Four hours of ischemia followed by reperfusion created a significant vasoconstriction and capillary no-reflow in the microcirculation of cremaster muscles. These alterations were largely prevented by IPC. Local intraarterial infusion of SNP without IPC created a similar microvascular protection to that induced by IPC alone. In contrast, intraarterial infusion of L-NA prior to IPC eliminated the IPC-induced microvascular protection. In conclusion, in late preconditioning, nitric oxide contributes to the initiation of a delayed microvascular protection against prolonged ischemia in skeletal muscle.  相似文献   
999.
1000.
PURPOSE: The purpose of this study was to determine the frequency and overall contribution of specific gene amplification events in the formation of Barrett's adenocarcinomas. The relationship of gene amplification to clinical-pathological variables and its potential usefulness as a marker for early cancer detection were also examined. EXPERIMENTAL DESIGN: We used quantitative PCR and Southern blot analysis to screen 87 cases of Barrett's adenocarcinoma for the presence or absence of 13 distinct gene amplification events. Gene amplification was then examined for correlation with other amplification events and clinical variables (survival, stage, nodal involvement, tumor invasion, smoking history, and gender). Additionally, 22 specimens of Barrett's with high-grade dysplasia (HGD) were examined for the presence of gene amplification. RESULTS: One or more amplification events were present in 50 of 87 (57%) adenocarcinomas. The ERBB2 gene was amplified in 19 of 87 (21.8%), CCNE1 in 11 of 87 (12.6%), GATA4 in 9 of 87 (10.3%), KRAS in 9 of 87 (10.3%), EGFR in 7 of 87 (8.0%), CCND1 in 6 of 87 (6.8%), HNF3alpha in 5 of 87 (5.7%), PIK3CA in 5 of 87 (5.7%), C-MYC in 4 of 87 (4.6%), DYRK2 in 2 of 87 (2.3%), and AIB1, AKT1, and IGF1R were amplified in 0 of 87 (0%) of the tumors. CCND1 amplification was found to correlate negatively with survival (P < 0.05). In addition, the ERBB2 amplicon positively correlated (P < 0.05) with GATA4 amplification. Increased copy number of the ERBB2 (1 of 22), GATA4 (1 of 22), KRAS (2 of 22), C-MYC (1 of 22), CCNE1 (2 of 22), and CCND1 (2 of 22) genes was also observed in one or more Barrett's adenocarcinomas with HGD. CONCLUSIONS: The high frequency of gene amplification in esophageal adenocarcinomas and HGD indicates the important role of these events in esophageal adenocarcinoma development. Additionally, these results underscore the possible usefulness of early detection approaches and chemotherapeutic strategies (ErbB2 and cyclin D1) targeted against amplified gene products.  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