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   649篇
  免费   24篇
  国内免费   1篇
耳鼻咽喉   16篇
儿科学   13篇
妇产科学   3篇
基础医学   56篇
口腔科学   3篇
临床医学   46篇
内科学   206篇
皮肤病学   10篇
神经病学   41篇
特种医学   39篇
外科学   102篇
综合类   5篇
预防医学   63篇
眼科学   26篇
药学   14篇
中国医学   1篇
肿瘤学   30篇
  2023年   6篇
  2022年   12篇
  2021年   27篇
  2020年   10篇
  2019年   13篇
  2018年   7篇
  2017年   13篇
  2016年   17篇
  2015年   11篇
  2014年   12篇
  2013年   8篇
  2012年   23篇
  2011年   26篇
  2010年   19篇
  2009年   12篇
  2008年   32篇
  2007年   24篇
  2006年   20篇
  2005年   19篇
  2004年   28篇
  2003年   38篇
  2002年   28篇
  2001年   23篇
  2000年   24篇
  1999年   18篇
  1998年   3篇
  1997年   4篇
  1996年   3篇
  1995年   3篇
  1994年   5篇
  1993年   3篇
  1992年   15篇
  1991年   18篇
  1990年   15篇
  1989年   15篇
  1988年   20篇
  1987年   17篇
  1986年   17篇
  1985年   8篇
  1984年   5篇
  1983年   4篇
  1981年   4篇
  1977年   9篇
  1976年   3篇
  1971年   2篇
  1970年   5篇
  1969年   3篇
  1968年   4篇
  1967年   2篇
  1965年   2篇
排序方式: 共有674条查询结果,搜索用时 15 毫秒
21.
Locus coeruleus neurons are strongly coupled during early postnatal development, and it has been proposed that these neurons are linked by extraordinarily abundant gap junctions consisting of connexin32 (Cx32) and connexin26 (Cx26), and that those same connexins abundantly link neurons to astrocytes. Based on the controversial nature of those claims, immunofluorescence imaging and freeze-fracture replica immunogold labeling were used to re-investigate the abundance and connexin composition of neuronal and glial gap junctions in developing and adult rat and mouse locus coeruleus. In early postnatal development, connexin36 (Cx36) and connexin43 (Cx43) immunofluorescent puncta were densely distributed in the locus coeruleus, whereas Cx32 and Cx26 were not detected. By freeze-fracture replica immunogold labeling, Cx36 was found in ultrastructurally-defined neuronal gap junctions, whereas Cx32 and Cx26 were not detected in neurons and only rarely detected in glia. In 28-day postnatal (adult) rat locus coeruleus, immunofluorescence labeling for Cx26 was always co-localized with the glial gap junction marker Cx43; Cx32 was associated with the oligodendrocyte marker 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase); and Cx36 was never co-localized with Cx26, Cx32 or Cx43. Ultrastructurally, Cx36 was localized to gap junctions between neurons, whereas Cx32 was detected only in oligodendrocyte gap junctions; and Cx26 was found only rarely in astrocyte junctions but abundantly in pia mater. Thus, in developing and adult locus coeruleus, neuronal gap junctions contain Cx36 but do not contain detectable Cx32 or Cx26, suggesting that the locus coeruleus has the same cell-type specificity of connexin expression as observed ultrastructurally in other regions of the CNS. Moreover, in both developing and adult locus coeruleus, no evidence was found for gap junctions or connexins linking neurons with astrocytes or oligodendrocytes, indicating that neurons in this nucleus are not linked to the pan-glial syncytium by Cx32- or Cx26-containing gap junctions or by abundant free connexons composed of those connexins.  相似文献   
22.
The aim of this study was to elucidate the clinical usefulness of scatter correction with an artificial neural network (ANN) in 99mTc and 123I dual-isotope SPECT. METHODS: Two algorithms for ANN scatter correction were tested: ANN-10 and ANN-3 employing 10 and 3 energy windows for data acquisition, respectively. Three patients underwent myocardial or brain SPECT with one of the following combinations of radiopharmaceuticals administered: 99mTc-tetrofosmin and 123I-metaiodobenzylguanidine (MIBG), 99mTc-methoxyisobutylisonitrile (MIBI) and 123I-beta-methyl-paraiodophenyl-pentadecanoic acid (BMIPP), or 99mTc-ethyl-cistainate dimmer (ECD) and 123I-iomazenil. The patients were also referred for single-isotope imaging incorporating conventional triple-energy window (TEW) scatter correction. Crosstalk- and scatter-corrected 99mTc- and 123I-SPECT images in dual-isotope acquisition with ANN were compared with those in single-isotope acquisition. RESULTS: The ANN method well separated 123I and 99mTc primary photons. Although ANN-10 yielded images of poor quality, ANN-3 offered comparable image quality with the single-isotope scan without significant increase of acquisition time. CONCLUSION: The proposed method is clinically useful because it provides various combinations of information without anatomical misregistration with one acquisition.  相似文献   
23.
We report a case with the inconsistency that the red blood cells lacked both A- and B-antigens while the serum showed reactivity with control B-red cells but not with A-red cells. A- and B-antigens were examined by serological blood typing and immunohistochemical staining, and DNA analyses were performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), DNA sequencing, and hot-stop PCR. A-antigens were demonstrable in the nail of the subject by serological study and immunostaining. DNA analyses showed that the nail retained a small amount of A-allele comparing to that of O-allele. Those genomic analyses of ABO genes were useful for demonstration of A allele in the nail of an individual with the absence of A antigen on red blood cells and the corresponding antibody in serum.  相似文献   
24.

Purpose

Studies comparing laparoscopic (LIHR) vs. open inguinal hernia repair (OIHR) have shown similar recurrence rates but have disagreed on perioperative outcomes and costs. The aim of this study is to compare laparoscopic vs. open outcomes and costs.

Methods

The National Surgical Quality Improvement Program (NSQIP) was used to compare durations of surgery, anesthesia time, and length of stay (LOS). The University HealthSystem Consortium (UHC) was used to review the cost and complications between approaches. Patients were matched on demographics, year of procedure and surgical approach between datasets for statistical analysis.

Results

A sample of 5468 patients undergoing OIHR (N = 4,693) or LIHR (N = 775) was selected from UHC from 2008–2011. An identical number of patients from NSQIP were matched to those from UHC resulting in a total of 10,936 records. LIHR patients had shorter duration of wait from admission to operation (p < 0.05). Conversely, LIHR patients had longer operating time (p < 0.05), duration of anesthesia (p < 0.05), and time in the operating room (p < 0.05).Overall complication rate was higher in open (3.1 vs. 1.8 %, p < 0.05). Cost favored open over LIHR ($4360 vs $5105). The cost discrepancy mainly stemmed from LIHR supplies ($1448 vs. $340; p < 0.05) and OR services ($1380 vs. $1080; p < 0.05).

Conclusion

This study demonstrates the LOS and perioperative outcomes were superior in the LIHR group; however, the overall cost was higher due to the supplies. Advancement in technology, surgeons’ skill level and preference of supplies are all factors in decreasing the overall cost of LIHR.
  相似文献   
25.
PurposeTo investigate differences in outcomes of uterine artery embolization (UAE) for leiomyoma when performed during different phases of the menstrual cycle.Materials and MethodsIn this single-institution retrospective analysis, 111 premenopausal patients (median [range] age, 44 [33–52] years) undergoing UAE for symptomatic leiomyoma between June 2014 and February 2020 were included. Twenty-one patients underwent UAE in the menstrual phase (the early follicular phase), 27 in the late follicular phase, and 63 in the luteal phase. Baseline characteristics and technical and peri-procedural outcomes were compared among groups. Leiomyoma infarction on contrast-enhanced magnetic resonance imaging 1 week after UAE and 4-month outcomes, including changes in the Uterine Fibroid Symptom and Quality of Life questionnaire scores, the volume reduction rates of the uterus and largest leiomyoma, follicle stimulating hormone values, adverse events, and amenorrhea, were compared among groups.ResultsA 4-month follow-up was completed for all patients. No significant differences were observed among groups in baseline characteristics or technical and peri-procedural outcomes. There were no significant differences in the multivariate-adjusted 1-week infarction rates of all leiomyoma volumes (P = .161) or multivariate-adjusted 4-month outcomes, including changes in the Uterine Fibroid Symptom and Quality of Life questionnaire symptoms and total scores (P = .864 and P = .798, respectively), the volume reduction rates of the uterus and the largest leiomyoma (P = .865 and P = .965, respectively), and follicle stimulating hormone values (P = .186) among the groups. No significant differences were noted in the 4-month adverse events (P = .260) or amenorrhea (P = .793) among the groups.ConclusionsThe present study demonstrated no significant differences in the outcomes of UAE for leiomyoma when performed during different phases of the menstrual cycle.  相似文献   
26.
27.
Summary We have proposed the systolic pressure-volume area (PVA) as a measure of the total mechanical energy generated by ventricular contraction, and we found a closely linear correlation between PVA and cardiac oxygen consumption (VO 2). Although the force-time integral (FTI) has long been considered to be the most reliable correlate of cardiac oxygen consumption (VO 2), we have already shown that VO 2 remained constant although FTI was changed while PVA was kept constant in the excised, cross-circulated dog left ventricle. This means that PVA is superior to FTI as a predictor of VO 2. In the present study, we studied whether a linear addition of FTI to PVA could improve the prediction of VO 2 from PVA in isovolumic and ejecting contractions with different afterload pressures in the same type of dog left ventricle preparation. Although left ventricular VO 2 was always closely correlated with either PVA (r=0.967, mean after z-transformation) or FTI (mean r=0.925), multiple regression analysis indicated that PVA alone accounted for as much as 94% (mean) of the variance of VO 2 and that FTI linearly added to PVA accounted for an additional few percent of the variance (statistically significant in less than half the cases). We conclude that the addition of FTI to PVA does not improve the predictability of VO 2 from PVA in ordinary contractions.  相似文献   
28.
Ribozyme-directed cleavage of mutant mRNAs appears to be a potentially effective therapeutic measure for dominantly inherited diseases. We previously demonstrated that two ribozymes targeted to the P23H mutation in rhodopsin slow photoreceptor degeneration in transgenic rats for up to 3 months of age when injected before significant degeneration at postnatal day (P) 15. We now have explored whether ribozyme rescue persists at older ages, and whether ribozymes are effective when injected later in the degeneration after significant photoreceptor cell loss. Recombinant adeno-associated virus (rAAV) vectors incorporating a proximal bovine rod opsin promoter were used to transfer either hairpin or hammerhead ribozyme genes to photoreceptors. For the study of long-term survival, rAAV was administered by subretinal injection at P15, and the rats were allowed to live up to 8 months of age. For the study of late-stage gene transfer, rAAV was administered at P30 or P45, when 40-45% of the photoreceptors already had degenerated. Eyes were examined functionally by the electroretinogram and structurally by morphometric analysis. When injected at P15, expression of either ribozyme markedly slowed the rate of photoreceptor degeneration for at least 8 months and resulted in significantly greater electroretinogram amplitudes at least up to P180. When injected at P30 or P45, virtually the same number of photoreceptors survived at P130 as when injected at P15. Ribozyme rescue appears to be a potentially effective, long-term therapy for autosomal dominant retinal degeneration and is highly effective even when the gene transfer is done after significant photoreceptor cell loss.  相似文献   
29.
The recently discovered connexin29 (Cx29) was reported to be present in the central and peripheral nervous systems (CNS and PNS), and its mRNA was found in particular abundance in peripheral nerve. The expression and localization of Cx29 protein in sciatic nerve were investigated using an antibody against Cx29. The antibody recognized Cx29 in HeLa cells transfected with Cx29 cDNA, while nontransfected HeLa cells were devoid of Cx29. Immunoblotting of sciatic nerve homogenate revealed monomeric and possibly higher molecular weight forms of Cx29. These were distinguished from connexin32 (Cx32), which also is expressed in peripheral nerve. Double immunofluorescence labelling for Cx29 and Cx32 revealed only partial colocalization of the two connexins, with codistribution at intermittent, conical-shaped striations along nerve fibers. By freeze-fracture replica immunogold labelling (FRIL), Cx32 was found in gap junctions in the outermost layers of myelin, whereas Cx29-immunogold labelling was found only in the innermost layer of myelin in close association with hexagonally arranged intramembrane particle (IMP) 'rosettes' and gap junction-like clusters of IMPs. Although both Cx32 and Cx29 were detected in myelin of normal mice, only Cx29 was present in Schwann cell membranes in Cx32 knockout mice. The results confirm that Cx29 is a second connexin expressed in Schwann cells of sciatic nerve. In addition, Cx29 is present in distinctive IMP arrays in the inner most layer of myelin, adjacent to internodal axonal plasma membranes, where this connexin may have previously unrecognized functions.  相似文献   
30.
PURPOSE: The purpose of this study was to determine the physiological responses of elderly women to a well-rounded exercise program performed in water (WEX). METHODS: The participants (60-75 yr of age) were randomly divided into a training (TR) group (N = 15) and a control group (N = 15). The TR group participated in a 12-wk supervised WEX program, 70 min x day(-1), 3 d x wk(-1). The WEX consisted of 20 min of warm-up and stretching exercise, 10 min of resistance exercise, 30 min of endurance-type exercise (walking and dancing), and 10 min of cool-down exercise. RESULTS: The WEX led to an increase (P < 0.05) in peak VO2 (12%) and VO2 at lactate threshold (20%). Muscular strength evaluated by a hydraulic resistance machine increased significantly at resistance dial setting 8 (slow) for knee extension (8%), knee flexion (13%), chest press (7%) and pull (11%), shoulder press (4%) and pull (6%), and back extension (6%). Vertical jump (9%), side-stepping agility (22%), trunk extension (11%), and FEV1.0 (7%) also increased significantly. There was a significant decrease in skin-fold thickness (-8%), low-density lipoprotein (LDL) cholesterol (-17%), and total cholesterol (-11%). There were no significant changes in these variables in the control group. CONCLUSION: These results indicate that WEX elicits significant improvements in cardiorespiratory fitness, muscular strength, body fat, and total cholesterol in older adult women. Water-based exercise appears to be a very safe and beneficial mode of exercise that can be performed as part of a well-rounded exercise program.  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