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   8797篇
  免费   403篇
  国内免费   80篇
耳鼻咽喉   50篇
儿科学   251篇
妇产科学   129篇
基础医学   940篇
口腔科学   212篇
临床医学   516篇
内科学   2505篇
皮肤病学   133篇
神经病学   787篇
特种医学   388篇
外科学   1619篇
综合类   21篇
预防医学   168篇
眼科学   103篇
药学   445篇
中国医学   17篇
肿瘤学   996篇
  2023年   55篇
  2022年   79篇
  2021年   205篇
  2020年   109篇
  2019年   185篇
  2018年   205篇
  2017年   188篇
  2016年   243篇
  2015年   211篇
  2014年   327篇
  2013年   345篇
  2012年   548篇
  2011年   594篇
  2010年   378篇
  2009年   302篇
  2008年   484篇
  2007年   515篇
  2006年   529篇
  2005年   582篇
  2004年   563篇
  2003年   494篇
  2002年   508篇
  2001年   142篇
  2000年   147篇
  1999年   165篇
  1998年   106篇
  1997年   82篇
  1996年   71篇
  1995年   63篇
  1994年   60篇
  1993年   49篇
  1992年   71篇
  1991年   65篇
  1990年   73篇
  1989年   81篇
  1988年   56篇
  1987年   43篇
  1986年   36篇
  1985年   30篇
  1984年   27篇
  1983年   23篇
  1982年   30篇
  1981年   21篇
  1980年   16篇
  1979年   22篇
  1978年   16篇
  1977年   25篇
  1976年   15篇
  1974年   14篇
  1967年   15篇
排序方式: 共有9280条查询结果,搜索用时 15 毫秒
91.
A phase I study ofN 4-behenoyl-1-β-d-arabinofuranosylcytosine (BHAC) was conducted in 66 patients, 41 with solid tumors and 25 with hematological malignancies. The patients received either a 2-h single intravenous (i.v.) drip infusion (Schedule 1) or consecutive daily 2-h i.v. infusions (Schedule 2). In Schedule 1 the daily dose was initiated with 1.5 mg kg?1 which was escalated up to 7 mg kg?1. Side-effects were mild, and included nausea, vomiting, epilation, and hot flushes. Because of the presence of the solvent vehicle, HCO-60 and in consideration of the mechanism of action of BHAC, the dose escalation was stopped at 7 mg kg?1. In Schedule 2, the daily dose was started with 1.5 mg kg?1 which was escalated up to 8 mg kg?1 and given for 2–16 days. Myelosuppression was found to be dose-limiting toxicity. The maximum tolerated dose (MTD) in patients with non-hematological solid tumors was assumed to be 5 mg kg?1 daily × 5 days. The plasma disappearance curve of BHAC looked biphasic, and when 4 mg kg?1 of BHAC were administered the half-lives of the initial phase (t 1/2α) and the second phase (t 1/2β) were calculated as 0.798 and 5.76 h respectively. In Schedule 2 complete remission was observed in 5 out of 21 patients with acute leukemia, one partial remission in Hodgkin’s disease, and one 1-B response (Karnofsky) in thyroid papillary adenocarcinoma.  相似文献   
92.
93.
The present study was designed to determine potential associations between the brain damage induced by hypoxic-ischemic (HI) insult and spatial learning impairment in an eight-arm radial maze task. We first determined the pathological outcomes after 2, 5, 9, and 17 weeks of recovery following the HI insult. The results show that the brain damage progressed from 2 up to 17 weeks of recovery. To clarify the time course of the brain damage changes, we investigated the histological changes of the same individual with magnetic resonance imaging (MRI) after 5, 9, and 57 weeks of recovery following the HI insult. The MRI changes were similar to the histological changes, and the brain damages were exacerbated in the contralateral hemisphere after 57 weeks of recovery following the HI insult. To investigate whether alteration in brain function was correlated with MRI and histological changes, the rats were made to find their way through an eight-arm radial maze was performed at either 7th or 16th weeks of recovery. According to the results, the spatial learning impairments of rats in the maze starting at 16 weeks of recovery were more severe than those at 7 weeks of recovery, indicating that the impairments were progressive and depended on the degree of brain damage. The results of the present study are the first demonstration that the evolutional and specific brain damage following the HI insult is slowly and progressively exacerbated to the contralateral hemisphere and rats who experience the HI are at risk for showing a late impairment of brain function.  相似文献   
94.
95.
Vascular Ehlers–Danlos syndrome (vEDS) is a hereditary connective tissue disorder (HCTD) characterized by arterial dissection/aneurysm/rupture, sigmoid colon rupture, or uterine rupture. Diagnosis is confirmed by detecting heterozygous variants in COL3A1. This is the largest Asian case series and the first to apply an amplification-based next-generation sequencing through custom panels of causative genes for HCTDs, including a specific method of evaluating copy number variations. Among 429 patients with suspected HCTDs analyzed, 101 were suspected to have vEDS, and 33 of them (32.4%) were found to have COL3A1 variants. Two patients with a clinical diagnosis of Loeys–Dietz syndrome and/or familial thoracic aortic aneurysm and dissection were also found to have COL3A1 variants. Twenty cases (57.1%) had missense variants leading to glycine (Gly) substitutions in the triple helical domain, one (2.9%) had a missense variant leading to non-Gly substitution in this domain, eight (22.9%) had splice site alterations, three (8.6%) had nonsense variants, two (5.7%) had in-frame deletions, and one (2.9%) had a multi-exon deletion, including two deceased patients analyzed with formalin-fixed and paraffin-embedded samples. This is a clinically useful system to detect a wide spectrum of variants from various types of samples.  相似文献   
96.
Cyclins and cyclin-dependent kinases may reflect the status of cell proliferation in cancer tissues. The authors sought to determine whether cdc2 and cyclin D1 are expressed in breast cancer and are useful as prognostic factors. Accumulation of cdc2 and cyclin D1 proteins was examined in 88 cases of breast cancer using immunoblotting techniques and correlations with clinicopathological factors and prognoses were investigated. Cdc2 and cyclin D1 proteins were observed in 27.3% and 75.0% of breast cancers studied, respectively. The incidence of lymph node metastasis was significantly high in cdc2/cyclin D1-double positive group and low in double negative group. On the other hand, the incidence of estrogen receptor (ER) negative cases was significantly higher in the cdc2-positive/cyclin D1-negative group. Relapse-free survival times of cdc2-positive cases were significantly shorter than those of cdc2-negative cases. The relapse-free survival times of cyclin D1-positive cases also tended to be poorer than those of cyclin D1-negative cases. Multivariate analyses revealed cdc2 as the second most significant of the prognostic variables, following lymph node status. The three-year relapse-free survival rate of cdc2/cyclin D1-double positive cases was 58.9%, whereas that of cdc2/cyclin D1-double negative cases was 100%. Cdc2 and cyclin D1 represent the status of cell proliferation in breast cancer, and may be useful in breast cancer assessment.  相似文献   
97.
A quantitative analysis was made of the myelinated fibers in the lateral corticospinal tract (LCST) at the levels of the 6th cervical, 7th thoracic and 4th lumbar spinal segments in 20 patients between 19 and 90 years old, and who died of non-neurological diseases. The diameter frequency histograms of myelinated fibers of LCST showed a bimodal pattern with a sharp peak of the small myelinated fibers and broad slope of the large myelinated fibers. The ratio of small fiber to large fiber densities was significantly higher in the 6th cervical (P<0.05) and 4th lumbar segments (P<0.01) than in the 7th thoracic segments. The density of small myelinated fibers was significantly lowered with advancing age (P<0.050.001), while that of large myelinated fibers was not significantly decreased in the aged patients, although it showed a slight age-dependent declining tendency. Age-dependent decline of small fiber density was more prominent in the cervical and lumbar segments. Retraction of the axon-collaterals from large-diameter myelinated fibers, which are abundant in the cervical and lumbar segments, may contribute to the age-related diminution of the small myelinated fibers in the LCST.Part of this work was supported by grants from the Ministry of Welfare and Health of Japan, and a grant from Uehara Memorial Research Foundation  相似文献   
98.
Background: Minoxidil is an inhibitor of lysyl hydroxylase, an enzyme involved in collagen production, and decreases collagen production in vitro. We investigated the in vitro effects of minoxidil on behavior such as proliferation and migration of rabbit subconjunctival fibroblasts (SCFs). The ultrastructural effect of the drug on SCFs was also examined. Methods: Proliferation of SCFs and closure of the defect produced in monolayer cultures in the presence or absence of minoxidil was studied. The ultrastructure of SCFs treated with minoxidil was also examined. Results: Minoxidil inhibited SCF proliferation and the closure of the defect produced in monolayer cell sheets. Ultrastructural observations revealed extensive areas of irregularly dilated endoplasmic reticulum in cells treated with minoxidil, indicating the accumulation of protein, probably underhydroxylated collagen precursors, in the cisternae of endoplasmic reticulum. Conclusions: The results indicated that minoxidil attenuated cellular activities of SCFs such as proliferation and migration in vitro. The exact mechanism of the inhibitory effects of minoxidil on these cellular activities is unknown. The findings suggest that the drug might help to prevent bleb scarring after glaucoma filtering surgery.  相似文献   
99.
Technetium-99m labeled diethylenetriaminepentaacetic acid (DTPA)-galactosyl human serum albumin (GSA) has been used for hepatocellular functional evaluation. This study proposed new and simple parameters to overcome the limitations of conventional parameters, and they were applied to the clinical staging of chronic liver dysfunction. The study group consisted of 93 patients including 81 with liver dysfunction and 12 control patients. In addition to the two conventional parameters, namely, receptor index (LHL15 = liver count divided by the sum of liver and heart counts at 15 minutes) and clearance index (HH15 = heart count at 15 minutes divided by the heart count at 3 minutes), 6 new parameters for Tc-99m GSA uptake and clearance were generated. The conventional receptor index of LHL15 showed a large variation depending on the size of region of interest (ROI) over the heart. The LHL15 normalized by the ROI size (nLHL15) showed more stable data and a better separation of mild liver dysfunction. A hyperbolic relationship between the LHL15 and HH 15 changed to a linear relationship by using the nLHL15 index. The combination of the liver to heart average count ratio at 15 minutes (LH 15) and T-half (minute) of the heart count also could differentiate each stage well. In conclusion, the use of the ROI-area normalized nLHL is recommended instead of the conventional LHL15. The indices of LH15 and T-half could be alternatively used as practical parameters for clinical staging in liver function.  相似文献   
100.
A 6-year-old boy with heterotopic liver transplant underwent urgent endoscopy under general anesthesia because of bloody stool. He was taking cyclosporin as an immunosuppressant. His hepatic function was normal and no side effects of cyclosporin were observed. Preoperative blood transfusion was performed because of severe anemia. Anesthesia was induced with midazolam 2 mg, ketamine 20 mg and fentanyl 0.05 mg, and maintained with addition of midazolam and ketamine. We did not use any inhalation anesthetics to avoid postoperative hepatic dysfunction. The endoscopy was successfully performed and the postoperative course was uneventful. We conclude that preanesthetic evaluation of immunosuppressant state and the hepatic function of transplanted liver is important for anesthetic management of a patient with heterotopic liver transplant.  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