全文获取类型
收费全文 | 2900篇 |
免费 | 177篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 64篇 |
儿科学 | 148篇 |
妇产科学 | 53篇 |
基础医学 | 283篇 |
口腔科学 | 47篇 |
临床医学 | 196篇 |
内科学 | 683篇 |
皮肤病学 | 47篇 |
神经病学 | 149篇 |
特种医学 | 211篇 |
外国民族医学 | 1篇 |
外科学 | 445篇 |
综合类 | 75篇 |
预防医学 | 123篇 |
眼科学 | 117篇 |
药学 | 149篇 |
中国医学 | 6篇 |
肿瘤学 | 286篇 |
出版年
2023年 | 18篇 |
2022年 | 34篇 |
2021年 | 111篇 |
2020年 | 51篇 |
2019年 | 90篇 |
2018年 | 112篇 |
2017年 | 61篇 |
2016年 | 75篇 |
2015年 | 80篇 |
2014年 | 128篇 |
2013年 | 154篇 |
2012年 | 204篇 |
2011年 | 180篇 |
2010年 | 123篇 |
2009年 | 129篇 |
2008年 | 171篇 |
2007年 | 146篇 |
2006年 | 114篇 |
2005年 | 105篇 |
2004年 | 85篇 |
2003年 | 66篇 |
2002年 | 53篇 |
2001年 | 43篇 |
2000年 | 42篇 |
1999年 | 49篇 |
1998年 | 43篇 |
1997年 | 40篇 |
1996年 | 46篇 |
1995年 | 44篇 |
1994年 | 34篇 |
1993年 | 26篇 |
1992年 | 35篇 |
1991年 | 28篇 |
1990年 | 28篇 |
1989年 | 37篇 |
1988年 | 41篇 |
1987年 | 32篇 |
1986年 | 24篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 13篇 |
1976年 | 13篇 |
1972年 | 6篇 |
1970年 | 7篇 |
1968年 | 6篇 |
排序方式: 共有3083条查询结果,搜索用时 15 毫秒
21.
Lu W Parikh PJ El Naqa IM Nystrom MM Hubenschmidt JP Wahab SH Mutic S Singh AK Christensen GE Bradley JD Low DA 《Medical physics》2005,32(4):890-901
We have developed a four-dimensional computed tomography (4D CT) technique for mapping breathing motion in radiotherapy treatment planning. A multislice CT scanner (1.5 mm slices) operated in ciné mode was used to acquire 12 contiguous slices in each couch position for 15 consecutive scans (0.5 s rotation, 0.25 s between scans) while the patient underwent simultaneous quantitative spirometry measurements to provide a sorting metric. The spirometry-sorted scans were used to reconstruct a 4D data set. A critical factor for 4D CT is quantifying the reconstructed data set quality which we measure by correlating the metric used relative to internal-object motion. For this study, the internal air content within the lung was used as a surrogate for internal motion measurements. Thresholding and image morphological operations were applied to delineate the air-containing tissues (lungs, trachea) from each CT slice. The Hounsfield values were converted to the internal air content (V). The relationship between the air content and spirometer-measured tidal volume (v) was found to be quite linear throughout the lungs and was used to estimate the overall accuracy and precision of tidal volume-sorted 4D CT. Inspection of the CT-scan air content as a function of tidal volume showed excellent correlations (typically r>0.99) throughout the lung volume. Because of the discovered linear relationship, the ratio of internal air content to tidal volume was indicative of the fraction of air change in each couch position. Theoretically, due to air density differences within the lung and in room, the sum of these ratios would equal 1.11. For 12 patients, the mean value was 1.08 +/- 0.06, indicating the high quality of spirometry-based image sorting. The residual of a first-order fit between v and V was used to estimate the process precision. For all patients, the precision was better than 8%, with a mean value of 5.1% +/- 1.9%. This quantitative analysis highlights the value of using spirometry as the metric in sorting CT scans. The 4D reconstruction provides the CT data required to measure the three-dimensional trajectory of tumor and lung tissue during free breathing. 相似文献
22.
Smoking and female infertility: a systematic review and meta-analysis 总被引:11,自引:10,他引:11
The high prevalence of smoking among women in their reproductive years
continues to be a matter of concern. The negative effects of smoking on
general health are well known, but smoking may also affect fertility. The
objective of the present study was to perform a systematic review of the
literature to determine whether there is an association between smoking and
risk of infertility in women of reproductive age, and to assess the size of
this effect. In the 12 studies used for this meta- analysis, the overall
value of the odds ratio (OR) for risk of infertility in women smokers
versus non-smokers was 1.60 [95% confidence interval (CI) 1.34-1.91].
Studies of subfertile women undergoing in-vitro fertilization (IVF)
treatment also show a reduction in fecundity among women smokers. A
meta-analysis of nine studies found an OR of 0.66 (95% CI 0.49-0.88) for
pregnancies per number of IVF- treated cycles in smokers versus
non-smokers. Despite the potential limitations of meta-analyses of
observational studies, the evidence presented in this review is compelling
because of the consistency of effect across different study designs, sample
size and types of outcome. However, continued reassurance is needed that
the calculated overall effect is not in fact due to confounding variables.
相似文献
23.
Positional cloning of the gene for X-linked retinitis pigmentosa 3: homology with the guanine-nucleotide-exchange factor RCC1 总被引:6,自引:7,他引:6
Roepman R; van Duijnhoven G; Rosenberg T; Pinckers AJ; Bleeker-Wagemakers LM; Bergen AA; Post J; Beck A; Reinhardt R; Ropers HH; Cremers FP; Berger W 《Human molecular genetics》1996,5(7):1035-1041
The gene for retinitis pigmentosa 3 (RP3), the most frequent form of X-
linked RP (XLRP), has been mapped previously to a chromosome interval of
less than 1000 kbp between the DXS1110 marker and the OTC locus at
Xp21.1-p11.4. Employing a novel technique, YAC Representation Hybridization
(YRH)', we have recently identified a small XLRP associated microdeletion
in this interval, as well as several putative exons including the 3' end of
a gene that was truncated by the deletion. cDNA library screening and
sequencing of a cosmid centromeric to the deletion has now enabled us to
identify numerous additional exons and to detect several point mutations in
patients with XLRP. The predicted gene product shows homology to RCC1, the
guanine-nucleotide- exchange factor (GEF) of the Ras-like GTPase Ran. Our
findings suggest that we have cloned the long-sought RP3 gene, and that it
may encode the GEF of a retina-specific GTP-binding protein.
相似文献
24.
Lundberg S; Rasmussen C; Berg AA; Lindblom B 《Human reproduction (Oxford, England)》1998,13(6):1490-1492
Falloposcopy is a transvaginal microendoscopic technique to explore the
human Fallopian tube from the uterotubal ostium to the fimbrial end.
Falloposcopy provides a unique possibility to visualize endotubal disease
and may be used therapeutically for removal of debris and for cutting down
filmy intraluminal adhesions. To assess the clinical performance of
falloposcopy as part of an infertility investigation, a total of 43 women
scheduled for laparoscopy as part of an investigation of infertility had a
falloposcopy performed in conjunction with the laparoscopy. All women were
investigated at Danderyd Hospital, Stockholm and Akademiska Hospital,
Uppsala, during 1995 and 1996. Images from the endosalpinx were obtained in
26 of 43 women (60.5%). In 10 women (23.3%), it was possible to obtain
images from both tubes. No images were of sufficient quality to describe
the entire tubal mucosa in detail. Falloposcopy represents a unique tool
for visualization of endotubal disease and may provide a valuable
instrument for in-vivo exploration of tubal physiology. However, certain
technical problems limit the usefulness of this method in routine clinical
practice. These technical problems have to be solved before falloposcopy
can achieve a central position in investigation and treatment of tubal
disease.
相似文献
25.
Outcomes of unrelated umbilical cord blood transplantation for X-linked adrenoleukodystrophy. 总被引:1,自引:0,他引:1
Donald Beam Michele D Poe James M Provenzale Paul Szabolcs Paul L Martin Vinod Prasad Suhag Parikh Tim Driscoll Srini Mukundan Joanne Kurtzberg Maria L Escolar 《Biology of blood and marrow transplantation》2007,13(6):665-674
Adrenoleukodystrophy (ALD) is an X-linked disorder caused by a defect in the metabolism of long chain fatty acids leading to demyelination, neurodegeneration, and death. The disease typically presents in young boys and adolescent boys. Allogeneic bone marrow transplantation has been used to halt progression of the disease. However, many patients lack suitable HLA- matched related donors and must rely on unmatched donors for a source of stem cells. The purpose of this study was to evaluate outcomes of unrelated donor umbilical cord blood transplantation after chemotherapy-based myeloablative conditioning and retrospectively determine if baseline studies correlate and help predict outcome. Between November 22, 1996, and November 3, 2005, 12 boys with X-linked ALD who lacked HL- matched related donors were referred to Duke University Medical Center for transplantation. These children were conditioned with myeloablative therapy including busulfan, cyclophosphamide, and antithymocyte globulin before receiving umbilical cord-blood transplants from unrelated donors. Baseline studies of neurophysiologic, neuroimaging, and neurodevelopmental status were performed and patients were subsequently evaluated for survival, engraftment, graft-versus-host disease, and neurodevelopmental outcomes. A substudy evaluated whether baseline neuroimaging and neurophysiologic studies correlated with cognitive and motor function and if these studies were predictive of posttransplantation outcomes. The umbilical cord blood grafts had normal levels of very long chain fatty acids. They delivered a median of 6.98 x 10(7) nucleated cells per kilogram of recipient body weight and were discordant for up to 4 of 6 HLA markers. Neutrophil engraftment occurred at a median of 22.9 days after transplantation. Three patients had grade II-IV acute graft-versus-host disease; 2 had extensive chronic graft-versus-host disease. Cumulative incidence of overall survival of the group at 6 months is 66.7% (95% confidence interval 39.9-93.3%). Median follow-up was 3.3 years (range 12 days to 6.3 years). As previously reported with bone marrow transplantation, symptomatic patients faired poorly with lower survival and rapid deterioration of neurologic function. This study included 3 patients transplanted at a very young age (2.6-3.5 years) before the onset of clinical symptoms who continue to develop at a normal rate for 3-5 years posttransplant. Although baseline Loes scores correlated with cognitive and motor outcome, neurophysiologic studies failed to show statistically significant differences. Transplantation of boys with X-linked ALD using partial HLA-matched umbilical cord blood yields similar results to those previously reported after bone marrow transplantation. Superior outcomes were seen in neurologically asymptomatic boys less than 3.5 years of age at the time of transplantation. Baseline Loes scores were a strong predictor of cognitive and motor outcome. 相似文献
26.
Comparison of the human and mouse genes encoding the telomeric protein, TRF1: chromosomal localization, expression and conserved protein domains 总被引:11,自引:0,他引:11
27.
High level of unequal meiotic crossovers at the origin of the 22q11. 2 and 7q11.23 deletions 总被引:5,自引:3,他引:5
Baumer A; Dutly F; Balmer D; Riegel M; Tukel T; Krajewska-Walasek M; Schinzel AA 《Human molecular genetics》1998,7(5):887-894
Interstitial chromosomal deletions at 22q11.2 and 7q11.23 are detected in
the vast majority of patients affected by CATCH 22 syndromes and the
Williams-Beuren syndrome, respectively. In a group of 15 Williams- Beuren
patients, we have shown previously that a large number of 7q11.23 deletions
occur in association with an interchromosomal rearrangement, indicative of
an unequal crossing-over event between the two homologous chromosomes 7. In
this study, we show that a similar mechanism also underlies the formation
of the 22q11.2 deletions associated with CATCH 22. In eight out of 10
families with a proband affected by CATCH 22, we were able to show that a
meiotic recombination had occurred at the critical deleted region based on
segregation analysis of grandparental haplotypes. The incidences of
crossovers observed between the closest informative markers, proximal and
distal to the deletion, were compared with the expected recombination
frequencies between the markers. A significant number of recombination
events occur at the breakpoint of deletions in CATCH 22 patients (P =
2.99x10(-7)). The segregation analysis of haplotypes in three- generation
families was also performed on an extended number of Williams-Beuren cases
(22 cases in all). The statistically significant occurrence of meiotic
crossovers (P = 4.45x10(-9)) further supports the previous findings. Thus,
unequal meiotic crossover events appear to play a relevant role in the
formation of the two interstitial deletions. The recurrence risk for
healthy parents in cases where such meiotic recombinations can be
demonstrated is probably negligible. Such a finding is in agreement with
the predominantly sporadic occurrence of the 22q11.2 and 7q11. 23
deletions. No parent-of-origin bias was observed in the two groups of
patients with regard to the origin of the deletion and to the occurrence of
inter- versus intrachromosomal rearrangements.
相似文献
28.
29.
Ko-Jiunn Liu Vandana S. Parikh Philip W. Tucker Byung S. Kim 《European journal of immunology》1994,24(11):2755-2760
A BCL1 immunoglobulin (Ig) transfectant, expressing wild-type surface (s)IgM with the TEPC-15 idiotype (T15-Id) and anti-phosphorylcholine (PC) specificity, was previously shown to present PC-conjugated hen egg-white lysozyme (PC-HEL) to a HEL-specific T cell hybridoma at a lower antigen (Ag) concentration than that required for native HEL. Two variant Ig transfectants, expressing T15-Id sIgM with substitutions either in the entire spacer, transmembrane (TM) domain and cytoplasmic tail (B186 variant) or in the NH2-terminal third of TM domain only (TM2 variant), failed to display this sIgM-mediated, enhanced presentation of PC-HEL at low concentrations. However, prolonged treatment with anti-T15-Id monoclonal antibody (mAb) led to a reduction of surface expression of the T15-Id sIgM in the wild-type and TM2 variant, but not in the B186 variant sIgM transfectants. Treatment with anti-T15-Id mAb also resulted in an increased intracellular accumulation of T15-Id sIgM in the wild-type transfectant, but not in the B186 variant. Subcellular fractionation analysis revealed that the ligands bound to the T15-Id sIgM are not efficiently transported to the dense lysosomal compartments in both B186 and TM2 transfectants, as compared to the wild-type sIgM transfectant. A significant increase in tyrosine phosphorylation after cross-linking of the T15-Id sIgM was observed only in the wild-type sIgM transfectant. These results suggest that, while the NH2-terminal third of the TM region is not involved in the process responsible for the ligand-induced reduction of surface expression of sIgM, it appears to be essential for subsequent transport of sIgM/ligand complexes to the lysosomal compartments, as well as efficient activation of tyrosine kinases. These results strongly suggest that sIg-mediated enhancement of specific antigen presentation reflects the ability of sIg to efficiently transport antigen to the lysosomal compartments, and possibly the activation of protein tyrosine kinases. 相似文献
30.
Anna Vassiliou Catherine H. Martin Sheryl T. Homa Jesse Stone Andrew Dawkins Mariya N. Genkova Helen Skyla Dela Roca Sejal Parikh Jinal Patel Tet Yap Aideen P. Killeen 《Andrologia》2021,53(2):e13938
Seminal oxidative stress (OS) is a major contributing factor to male infertility. Semen analysis cannot identify reactive oxygen species (ROS), which can be measured using a chemiluminescence assay. Measurement of redox potential provides a more comprehensive assessment of OS, although the test has yet to be fully validated. This study aimed to validate the MiOXsys analyser for measuring static oxidation–reduction potential (sORP). Results demonstrated that duplicate measurements must be taken, sensors must be batch tested, and sockets should be regularly changed to avoid inconsistency in measurement. Measurement of sORP using MiOXsys exhibited good reproducibility across different operators (p = 0.469), analysers (p = 0.963) and days (p = 0.942). It is not affected by mechanical agitation (p = 0.522) or snap freezing and thawing (p = 0.823). The stability of sORP over time requires further verification, particularly in samples with high initial sORP. Measurement is temperature sensitive between 2 and 37°C, significantly increasing with increasing temperature (p = 0.0004). MiOXsys is a more stable assay for assessing OS than chemiluminescence methods and permits greater flexibility for sample handling. MiOXsys could be implemented to complement semen analysis as part of routine diagnostic testing for male infertility and may be useful in identifying contributing factors to idiopathic infertility. 相似文献