全文获取类型
收费全文 | 71214篇 |
免费 | 4496篇 |
国内免费 | 271篇 |
专业分类
耳鼻咽喉 | 1111篇 |
儿科学 | 2026篇 |
妇产科学 | 1328篇 |
基础医学 | 7925篇 |
口腔科学 | 1455篇 |
临床医学 | 7005篇 |
内科学 | 14768篇 |
皮肤病学 | 1113篇 |
神经病学 | 6905篇 |
特种医学 | 2493篇 |
外国民族医学 | 5篇 |
外科学 | 12391篇 |
综合类 | 848篇 |
一般理论 | 94篇 |
预防医学 | 5932篇 |
眼科学 | 1379篇 |
药学 | 4546篇 |
中国医学 | 111篇 |
肿瘤学 | 4546篇 |
出版年
2023年 | 352篇 |
2022年 | 555篇 |
2021年 | 1771篇 |
2020年 | 928篇 |
2019年 | 1550篇 |
2018年 | 1816篇 |
2017年 | 1308篇 |
2016年 | 1343篇 |
2015年 | 1479篇 |
2014年 | 2278篇 |
2013年 | 3208篇 |
2012年 | 4858篇 |
2011年 | 5042篇 |
2010年 | 2761篇 |
2009年 | 2450篇 |
2008年 | 4451篇 |
2007年 | 4713篇 |
2006年 | 4571篇 |
2005年 | 4547篇 |
2004年 | 4290篇 |
2003年 | 3952篇 |
2002年 | 3670篇 |
2001年 | 561篇 |
2000年 | 486篇 |
1999年 | 635篇 |
1998年 | 743篇 |
1997年 | 668篇 |
1996年 | 593篇 |
1995年 | 522篇 |
1994年 | 511篇 |
1993年 | 430篇 |
1992年 | 380篇 |
1991年 | 378篇 |
1990年 | 311篇 |
1989年 | 290篇 |
1988年 | 288篇 |
1987年 | 269篇 |
1986年 | 281篇 |
1985年 | 369篇 |
1984年 | 444篇 |
1983年 | 371篇 |
1982年 | 536篇 |
1981年 | 497篇 |
1980年 | 458篇 |
1979年 | 212篇 |
1978年 | 281篇 |
1977年 | 268篇 |
1976年 | 212篇 |
1975年 | 223篇 |
1973年 | 187篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
In vivo voltammetry at chronically implanted carbon paste electrodes in unrestrained rats is a particularly useful technique for evaluating neurochemical changes during spontaneous behaviour, or behaviour under experimental control. A 3 peak signal is observed in the striatum; most recently the consensus view has attributed these peaks to ascorbic acid (AA), uric acid (UA) and homovanillic acid (HVA) in ascending order of oxidation potential. We have used a pharmacological approach, combined with in vivo dialysis, to further elucidate the nature of the contributing species. Allopurinol, an inhibitor of xanthine oxidase, and thus of uric acid production, has previously been reported to abolish peak 2. We now report, using dialysis, that it selectively depletes UA in the extracellular fluid (ECF). Pargyline, a monoamine oxidase inhibitor, reduces peak 3 transiently (max. 60%) as expected, however it results in a more sustained reduction in ECF HVA (max. 100%). It also increases peak 1 (max. 75%) and decreases peak 2 (max. 40%), although changes in ECF AA and UA measured by dialysis and HPLC are minimal. Pargyline does however reduce ECF 5-hydroxyindoleacetic acid by 65%. We conclude that, using linear sweep voltammetry at chronically implanted paste electrodes: (a) one or more substances in addition to AA can contribute to peak 1; dopamine can do so in some situations; (b) 5-hydroxyindoleacetic acid, as well as UA, contributes to peak 2; its contribution is about one third that of the latter; and (c) one or more substances in addition to HVA can contribute to peak 3. 3-Methoxytyramine can do so. Since this is another methylated metabolite of dopamine, this does not prevent the use of peak 3 as an index of dopamine metabolism, and may extend its usefulness to situations where monoamine oxidase is inhibited. 相似文献
143.
Stefanie Sarantopoulos Kristen E Stevenson Haesook T Kim Nazmim S Bhuiya Corey S Cutler Robert J Soiffer Joseph H Antin Jerome Ritz 《Clinical cancer research》2007,13(20):6107-6114
PURPOSE: Recent studies suggest that donor B cells as well as T cells contribute to immune pathology in patients with chronic graft-versus-host disease (GVHD). B-cell activating factor (BAFF) promotes survival and differentiation of activated B cells. Thus, we tested whether BAFF correlated with chronic GVHD disease activity and time of onset after allogeneic hematopoietic stem cell transplantation (HSCT). EXPERIMENTAL DESIGN: Patients who had undergone allogeneic HSCT between 1994 and 2005 for hematologic malignancies were studied. ELISA was used to measure plasma BAFF levels and flow cytometry was used to assess BAFF receptor expression on B cells in patients with or without chronic GVHD. RESULTS: In 104 patients, BAFF levels were significantly higher in patients with active chronic GVHD compared with those without disease (P = 0.02 and 0.0004, respectively). Treatment with high-dose prednisone (>or=30 mg/d) was associated with reduced BAFF levels in patients with active chronic GVHD (P = 0.0005). Serial studies in 24 patients showed that BAFF levels were high in the first 3 months after HSCT but subsequently decreased in 13 patients who never developed chronic GVHD. In contrast, BAFF levels remained elevated in 11 patients who developed chronic GVHD. Six-month BAFF levels >or=10 ng/mL were strongly associated with subsequent development of chronic GVHD (P < 0.0001). Following transplant, plasma BAFF levels correlated inversely with BAFF receptor expression on B cells (P = 0.01), suggesting that soluble BAFF affected B cells through this receptor. CONCLUSION: These results suggest that elevated BAFF levels contribute to B-cell activation in patients with active chronic GVHD. 相似文献
144.
Margaret Sullivan Pepe Ziding Feng Gary Longton Joseph Koopmeiners 《Statistics in medicine》2009,28(5):762-779
Development of a disease screening biomarker involves several phases. In phase 2 its sensitivity and specificity is compared with established thresholds for minimally acceptable performance. Since we anticipate that most candidate markers will not prove to be useful and availability of specimens and funding is limited, early termination of a study is appropriate, if accumulating data indicate that the marker is inadequate. Yet, for markers that complete phase 2, we seek estimates of sensitivity and specificity to proceed with the design of subsequent phase 3 studies. We suggest early stopping criteria and estimation procedures that adjust for bias caused by the early termination option. An important aspect of our approach is to focus on properties of estimates conditional on reaching full study enrollment. We propose the conditional‐UMVUE and contrast it with other estimates, including naïve estimators, the well‐studied unconditional‐UMVUE and the mean and median Whitehead‐adjusted estimators. The conditional‐UMVUE appears to be a very good choice. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
145.
Joseph G Rajendran Ajay K Gopal Darrel R Fisher Larry D Durack Ted A Gooley Oliver W Press 《Journal of nuclear medicine》2008,49(5):837-844
Myeloablative radioimmunotherapy using (131)I-tositumomab (anti-CD20) monoclonal antibodies is an effective therapy for B-cell non-Hodgkin's lymphoma. The amount of radioactivity for radioimmunotherapy may be determined by several methods, including those based on whole-body retention and on dose to a limiting normal organ. The goal of each approach is to deliver maximal myeloablative amounts of radioactivity within the tolerance of critical normal organs. METHODS: Records of 100 consecutive patients who underwent biodistribution and dosimetry evaluation after tracer infusion of (131)I-tositumomab before radioimmunotherapy were reviewed. We assessed organ and tissue activities over time by serial gamma-camera imaging to calculate radiation-absorbed doses. Organ volumes were determined from CT scans for organ-specific dosimetry. These dose estimates helped us to determine therapy on the basis of projected dose to the critical normal organ receiving a maximum tolerable radiation dose. We compared organ-specific dosimetry for treatment planning with the whole-body dose-assessment method by retrospectively analyzing the differences in projected organ-absorbed doses and their ratios. RESULTS: Mean organ doses per unit of administered activity (mGy/MBq) estimated by both methods were 0.33 for liver and 0.33 for lungs by the whole-body method and 1.52 for liver and 1.74 for lungs by the organ-specific method (P=0.0001). The median differences between methods were 0.92 mGy/MBq (range, 0.36-2.2 mGy/MBq) for lungs, 0.82 mGy/MBq (range, 0.28-1.67 mGy/MBq) for liver, and -0.01 mGy/MBq (range, -0.18-0.16 mGy/MBq) for whole body. The median ratios of the treatment activities based on limiting normal-organ dose were 5.12 (range, 2.33-10.01) for lungs, 4.14 (range, 2.16-6.67) for liver, and 0.94 (range, 0.79-1.22) for whole body. We found substantial differences between the dose estimated by the 2 methods for liver and lungs (P=0.0001). CONCLUSION: Dosimetry based on whole-body retention will underestimate the organ doses, and a preferable approach is to evaluate organ-specific doses by accounting for actual radionuclide biodistribution. Myeloablative treatments based on the latter approach allow administration of the maximum amount of radioactivity while minimizing toxicity. 相似文献
146.
In the differential clinical diagnosis of mammary neoplasms, adenocarcinoma can safely be excluded only after biopsy and microscopic study.In a series of 177 cases of mammary cancer treated by surgery with x-ray therapy, 30.4 per cent of the patients are alive three years or more after treatment; 18 per cent five years or longer.Only one of every four patients presents herself with a lesion still within the breast. Exclusive of Group I this results in a cure in 86.1 per cent in Group II and 15.4 per cent in Group III. The mortality rate then increases five and one-half times as spread occurs beyond the breast.The results of irradiation therapy for curative purposes in recurrent or metastatic mammary adenocarcinoma are poor.
Stage | Patients Treated | Per Cent Cures |
I | 1 | 100.0 |
II and IIa | 40 | 86.1 |
III and IIIa | 130 | 15.4 |