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   20680篇
  免费   1393篇
  国内免费   56篇
耳鼻咽喉   126篇
儿科学   441篇
妇产科学   282篇
基础医学   2760篇
口腔科学   332篇
临床医学   2588篇
内科学   3624篇
皮肤病学   203篇
神经病学   1828篇
特种医学   716篇
外科学   2857篇
综合类   238篇
一般理论   28篇
预防医学   2689篇
眼科学   432篇
药学   1607篇
中国医学   35篇
肿瘤学   1343篇
  2024年   20篇
  2023年   140篇
  2022年   240篇
  2021年   487篇
  2020年   309篇
  2019年   439篇
  2018年   519篇
  2017年   396篇
  2016年   435篇
  2015年   587篇
  2014年   750篇
  2013年   978篇
  2012年   1642篇
  2011年   1672篇
  2010年   953篇
  2009年   890篇
  2008年   1459篇
  2007年   1603篇
  2006年   1454篇
  2005年   1451篇
  2004年   1421篇
  2003年   1338篇
  2002年   1156篇
  2001年   149篇
  2000年   109篇
  1999年   165篇
  1998年   224篇
  1997年   152篇
  1996年   132篇
  1995年   104篇
  1994年   113篇
  1993年   88篇
  1992年   53篇
  1991年   49篇
  1990年   36篇
  1989年   38篇
  1988年   23篇
  1987年   34篇
  1986年   32篇
  1985年   33篇
  1984年   25篇
  1983年   34篇
  1982年   28篇
  1981年   29篇
  1980年   26篇
  1979年   10篇
  1978年   14篇
  1977年   11篇
  1976年   20篇
  1972年   7篇
排序方式: 共有10000条查询结果,搜索用时 2 毫秒
991.
10% of patch-tested patients have a positive reaction to gold. Most lack clinical symptoms, but allergic contact dermatitis (ACD) to gold is increasing. In this study, 77 dermatological outpatients were divided into 3 groups depending on epicutaneous patch test outcomes: a group positive to gold (EPI+), a group negative to gold (EPI−), and a group with irritant reactions to gold (EPI-IR). Lymphocytes were stimulated in vitro with gold sodium thiosulfate. Proliferation was assessed using the lymphocyte transformation test (LTT), and cytokine secretion was assessed using a multibead array (Luminex®; Linco Research Inc., St. Charles, MO, USA), in order to evaluate whether an in vitro method with high diagnostic accuracy could be devised. The EPI+ group showed a significantly increased secretion of interferon (IFN)-γ, interleukin (IL)-2, and IL-13 and also showed a significantly higher stimulation indexes for LTT, compared to the other 2 subject groups. Sensitivity and specificity were calculated for all methods individually and combined, but IFN-γ assessment alone was the most accurate method for identifying ACD to gold, with sensitivity and specificity of 81.8% and 82.1%, respectively. This method also identified 87.5% of the EPI-IR subjects as non-allergic. Therefore, assessment of secretion of IFN-γ should be a valuable complement to patch test for diagnosing gold allergy.  相似文献   
992.
Pregnancy outcomes and community health: the POUCH study of preterm birth   总被引:1,自引:0,他引:1  
In light of the social/ethnic disparity in preterm delivery (PTD) rates, the Pregnancy Outcomes and Community Health (POUCH) Study takes a broad view of the determinants of PTD by attempting to link underlying biological and psychosocial factors. The relationships between placental pathology, maternal biomarkers, and antecedent psychosocial factors are evaluated in three hypothesised pathways of PTD – one characterised primarily by infection, one by maternal vascular disease, and one by premature elevations in corticotropin releasing hormone in the absence of histological evidence of placental pathology. Within each pathway, an emphasis is placed on understanding the roles of stress and of maternal serum alpha-fetoprotein, an early biomarker associated with PTD. The POUCH Study enrols pregnant women from five Michigan communities. Information about these women and their environments is gathered through detailed interviews and collection of biological samples including hair, urine, saliva, blood, vaginal fluid, and vaginal smear at 15–26 weeks of gestation. We have chosen to focus on the second trimester – a time when pathological processes may have evolved to a detectable stage, but generally before the onset of biological changes that accompany labour. This focus is consistent with the long-range goal of early detection/intervention and prevention of PTD.  相似文献   
993.
PURPOSE: AQ4N is a novel bioreductive prodrug under clinical investigation. Preclinical evidence shows that AQ4N penetrates deeply within tumors and undergoes selective activation to form AQ4, a potent topoisomerase II inhibitor, in hypoxic regions of solid tumors. This proof-of-principle, phase I study evaluated the activation, hypoxic selectivity, and safety of AQ4N in patients with advanced solid tumors. EXPERIMENTAL DESIGN: Thirty-two patients with cancer (8 glioblastoma, 9 bladder, 8 head and neck, 6 breast, and 1 cervix) received a single 200 mg/m(2) dose of AQ4N before elective surgery. AQ4 and AQ4N levels in 95 tissues (tumor, healthy tissue) were assessed by liquid chromatography-tandem mass spectrometry. Tissue sections were also analyzed for AQ4 fluorescence using confocal microscopy, and for expression of the hypoxia-regulated glucose transporter, Glut-1. RESULTS: Activated AQ4 was detected in all tumor samples with highest levels present in glioblastoma (mean 1.2 microg/g) and head and neck (mean 0.65 microg/g) tumors; 22 of 32 patients had tumor AQ4 concentrations > or = 0.2 microg/g, levels previously shown to be active in preclinical studies. In 24 of 30 tumor samples, AQ4 was detected at higher concentrations than in adjacent normal tissue (tumor to normal ratio range 1.1-63.6); distant skin samples contained very low concentrations of AQ4 (mean 0.037 microg/g). Microscopic evaluation of tumor sections revealed that AQ4 colocalized within regions of Glut-1+ hypoxic cells. CONCLUSIONS: AQ4N was activated selectively in hypoxic regions in human solid tumors. Intratumoral concentrations of AQ4 exceeded those required for activity in animal models and support the evaluation of AQ4N as a novel tumor-targeting agent in future clinical studies.  相似文献   
994.
995.
PURPOSE: The primary aim of this study was to measure the objective tumor response rate following treatment with indisulam [E7070; N-(3-chloro-7-indolyl)-1,4-benzenedisulfonamide] as second-line therapy in patients with advanced non-small cell lung cancer. The secondary aims were to determine progression-free survival, to assess the safety and tolerability of indisulam, and to study its pharmacokinetic and pharmacodynamic profile. EXPERIMENTAL DESIGN: Patients were randomized to receive indisulam every 3 weeks either as a single i.v. dose of 700 mg/m(2) on day one (dx1) or 130 mg/m(2) given on days 1 to 5 inclusive as a daily infusion (dx5). All patients had previously received platinum-based chemotherapy. RESULTS: Forty-four patients were randomized. Only minor responses were seen. Myelosuppression, gastrointestinal symptoms, and lethargy were the most common toxicities and were more frequent in the dx1 arm. The pharmacokinetics of indisulam in each treatment schedule were adequately described using a previously developed population pharmacokinetic model and were mostly consistent with the results of the phase I program. Flow cytometric analysis of endobronchial and metastatic disease revealed a reduction in the fraction of cycling cells and an increase in apoptosis following indisulam compared with pretreatment levels. CONCLUSIONS: We conclude that, despite evidence of tumor-specific indisulam-induced apoptosis, neither of these treatment schedules has single-agent activity as second-line treatment of non-small cell lung cancer.  相似文献   
996.
3,5‐Dichloroaniline is commonly found in many compounds with pharmacological and other biological activities. [13C6]‐Aniline or its hydrochloride salt was converted in three steps to [13C6]‐3,5‐dichloroaniline, which can be incorporated in compounds of interest and used as internal standards in drug metabolism and pharmacokinetics (DMPK) studies. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
997.
998.

Introduction  

Anti-oestrogens have been the mainstay of therapy in patients with oestrogen-receptor (ER) positive breast cancer and have provided significant improvements in survival. However, their benefits are limited by tumour recurrence in a significant proportion of initially drug-responsive breast cancer patients because of acquired anti-oestrogen resistance. Relapse on such therapies clinically presents as local and/or regional recurrences, frequently with distant metastases, and the prognosis for these patients is poor. The selective ER modulator, tamoxifen, classically exerts gene inhibitory effects during the drug-responsive phase in ER-positive breast cancer cells. Paradoxically, this drug is also able to induce the expression of genes, which in the appropriate cell context may contribute to an adverse cell phenotype. Here we have investigated the effects of tamoxifen and fulvestrant treatment on invasive signalling and compared this with the direct effects of oestrogen withdrawal to mimic the action of aromatase inhibitors.  相似文献   
999.
Summary: The Caesarean section rate in consecutive years was decreased from 20.5% to 11.1% of total public deliveries (p< 0.0001). On retrospective analysis the emergency Caesarean section rate decreased from 10.9% to 6.0% (p < 0.0001) and elective Caesarean section rate from 9.6% to 5.1% (p<0.0001) in consecutive years. Interventions which have accounted for the decrease were 3-fold. Firstly, vaginal birth after Caesarean delivery was encouraged, secondly, the active management of labour and thirdly, extensive, regular peer review were introduced as unit policy. The decrease in the Caesarean section rate was not achieved at the expense of the fetus as judged by perinatal mortality rates and 5-minute Apgar scores of less than 7.  相似文献   
1000.
Summary Ninety-one cases of primary breast cancers and their nodal metastases were examined with DNA flow cytometry. No differences were found between the stemline distributions in the primary tumors and nodal metastases. At both sites stemlines clustered around a DNA index of 1.0 (33–40% of cases) and 1.8.The mean S-phase fractions were 7.9 in primary tumors versus 5.6% in nodal metastases (p = 0.02); this difference was also observed if the analysis was restricted to cases with DNA aneuploidy at both sites (10.2 versus 7.6%, p = 0.04). Our results indicate that axillary nodal ploidy and proliferation reflect primary tumor characteristics rather than displaying changes associated with selection during the lymphatic metastatic process. Lymph nodes may have a suppressive effect on the proliferation of tumor cells.  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