全文获取类型
收费全文 | 5297篇 |
免费 | 319篇 |
国内免费 | 54篇 |
专业分类
耳鼻咽喉 | 51篇 |
儿科学 | 92篇 |
妇产科学 | 276篇 |
基础医学 | 556篇 |
口腔科学 | 91篇 |
临床医学 | 565篇 |
内科学 | 1186篇 |
皮肤病学 | 59篇 |
神经病学 | 409篇 |
特种医学 | 132篇 |
外科学 | 667篇 |
综合类 | 101篇 |
一般理论 | 2篇 |
预防医学 | 241篇 |
眼科学 | 299篇 |
药学 | 453篇 |
中国医学 | 28篇 |
肿瘤学 | 462篇 |
出版年
2023年 | 25篇 |
2022年 | 71篇 |
2021年 | 153篇 |
2020年 | 60篇 |
2019年 | 117篇 |
2018年 | 161篇 |
2017年 | 99篇 |
2016年 | 117篇 |
2015年 | 161篇 |
2014年 | 199篇 |
2013年 | 253篇 |
2012年 | 407篇 |
2011年 | 373篇 |
2010年 | 288篇 |
2009年 | 214篇 |
2008年 | 305篇 |
2007年 | 323篇 |
2006年 | 318篇 |
2005年 | 274篇 |
2004年 | 238篇 |
2003年 | 200篇 |
2002年 | 175篇 |
2001年 | 164篇 |
2000年 | 158篇 |
1999年 | 131篇 |
1998年 | 27篇 |
1997年 | 36篇 |
1996年 | 25篇 |
1995年 | 23篇 |
1994年 | 25篇 |
1993年 | 12篇 |
1992年 | 79篇 |
1991年 | 56篇 |
1990年 | 66篇 |
1989年 | 40篇 |
1988年 | 27篇 |
1987年 | 39篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 9篇 |
1975年 | 10篇 |
1973年 | 8篇 |
1972年 | 12篇 |
1971年 | 8篇 |
排序方式: 共有5670条查询结果,搜索用时 31 毫秒
41.
We previously reported that proper dilution of sera that contain IgG monoclonal proteins (M-proteins) is necessary for accurate quantitation of serum albumin and M-protein concentrations separated by serum protein electrophoresis (SPE) using the Beckman PARAGON agarose electrophoresis system. We now report the significance of pre-electrophoretic serum dilution for M-protein quantitation of sera from patients with IgA and IgM monoclonal gammopathy. We measured M-proteins by SPE in 82 serum samples from 29 patients with IgA and 72 samples from 23 patients with IgM monodonal gammopathy. The serum M-protein concentrations (mean +/- SD) at 1:5, 1:10, and 1:20 dilutions (v/v) for all samples of both types were 49.7 +/- 12.9, 49.1 +/- 13.1, and 47.8 +/- 13.0 g/L, respectively. Thirty-two (20.8%) of 154 sera showed varying degrees of increase in M-protein concentrations with serum dilutions higher than 1:5; only 8 (5.2%) showed an increase 3 SDs. By SPE, the M-protein concentration (mean +/- SD) of these 8 sera at 1:5, 1:10, and 1:20 dilutions were 52.6 +/- 7.8, 57.1 +/- 7.2, and 57.6 +/- 7.1 g/L, respectively; the albumin concentrations (mean +/- SD) were 41.4 +/- 4.4, 37.9 +/- 3.8, and 37.1 +/- 2.9 g/L, respectively. The corresponding albumin concentration (mean +/- SD) was 36.8 +/- 3.7 g/L, assayed by the bromcresol green dye-binding method. These 8 samples were obtained from 3 patients, 2 with IgM kappa and 1 with IgA lambda monoclonal gammopathy. On the electrophoresis membranes, the M-protein bands of these 8 samples were narrow, thin, and dense; upon scanning, they appeared taller and thinner than the corresponding albumin bands. The samples of this subset contained relatively high concentrations of M-protein and total serum protein. We conclude that a pre-electrophoretic dilution of 1:5 (v/v) is adequate for most sera with IgA or IgM M-proteins. However, 1:10 or 1:20 dilution is occasionally required for a subset of sera with IgA or IgM M-proteins that show an unusually thin, narrow, and dense M-protein band and have high total serum protein content. 相似文献
42.
Tseng CJ Chen SF Liou SI Lu SC Chen JM Sun CF Chang SD Cheng PJ Liou JD Chu DC 《Annals of clinical and laboratory science》2004,34(2):154-158
Clinical features of Peutz-Jeghers syndrome (PJS), an autosomal dominant disorder, include clusters of melanotic spots on the lips and limbs, polyposis of the gastrointestinal (GI) tract, and propensity to develop neoplasms of the GI tract, ovaries, testes, and other sites. We report twin sisters with PJS who were found to be homozygous, based on analyses of 9 DNA markers containing short tandem repeats (STR). Aberrant expression of a putative tumor suppressor gene, STK11, which encodes a serine threonine kinase, has been suggested as the etiologic factor in PJS. In both of the twin sisters with PJS, mRNA analyses by RT-PCR demonstrated a complete lack of STK11 gene expression. These results provide direct evidence that STK11 gene expression is abnormal in PJS. Detecting abnormal expression of the STK11 gene may serve as a molecular approach to the diagnosis of PJS and may facilitate genotype-phenotype correlations in PJS patients. 相似文献
43.
Comparison of different PCR approaches for characterization of Burkholderia (Pseudomonas) cepacia isolates. 总被引:1,自引:2,他引:1
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
P Y Liu Z Y Shi Y J Lau B S Hu J M Shyr W S Tsai Y H Lin C Y Tseng 《Journal of clinical microbiology》1995,33(12):3304-3307
In this study, we evaluated three PCR methods for epidemiological typing of Burkholderia (Pseudomonas) cepacia--PCR-ribotyping, arbitrarily primed PCR (AP-PCR) and enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR)--and compared them with pulsed-field gel electrophoresis. The analysis was performed with 31 isolates of B. cepacia, comprising 23 epidemiologically unrelated isolates and 8 isolates collected from the same patient during two episodes of bacteremia. Pulsed-field gel electrophoresis, ERIC-PCR, and AP-PCR identified 23 distinct types among the 23 unrelated isolates, while PCR-ribotyping only identified 12 strain types, even after AluI digestion of the amplification products. Among the eight isolates collected from the same patient, all typing techniques revealed two clones of strains. The day-to-day reproducibilities of PCR-ribotyping and ERIC-PCR were good, while greater day-to-day variations were noted in the fingerprints obtained by AP-PCR. We conclude that all three PCR techniques are useful for rapid epidemiological typing of B. cepacia, but ERIC-PCR seems to be more reproducible and discriminative. 相似文献
44.
A time-dependent loss of retrograde transport ability in distally axotomized rubrospinal neurons 总被引:1,自引:0,他引:1
Studies on the effect of axotomy on adult intrinsic central projection neurons have generally assumed that the severed proximal axonal stumps were still capable of retrogradely transporting tracer at varying times after injury. Failure of transport was interpreted as neuronal death, which is at odds with current understanding that central projection neurons survive distal axotomy. We used lumbar spinal cord-projecting rubrospinal neurons of the rat as a model to evaluate the ability of injured neurons to transport tracer retrogradely at different times after distal axotomy. We examined only the caudal part of the red nucleus, since rubrospinal neurons are concentrated here. In control animals, tracer applied to the rubrospinal tract at the T10 vertebral level labeled ventrolateral rubral neurons, while C3 application marked all rubral neurons. From 3 days after a T10 axotomy and tracer application, most ventrolateral neurons were no longer labeled by another tracer application at the C3 vertebral level via an axonal cut. The phenomenon was not caused by tracer toxicity, since a T10 tractotomy without tracer application also prevented these axotomized neurons from being labeled when treated similarly. Thus, neuronal retrograde transport capability was seriously retarded 3 days after a distal axotomy. Loss of retrograde transport may merely suggest that a mechanism no longer in service has been switched off, or perhaps it may insulate injured neurons from the effect of lesion site-derived factors. Using this property, we were able to localize cervical spinal cord-projecting rubrospinal neurons in the caudal red nucleus. Results show that although they concentrate in the dorsomedial region, some neurons were found to extend into the ventrolateral part of the nucleus. 相似文献
45.
One hundred twelve peripheral blood specimens were tested for the presence of cytomegalovirus (CMV) by the tube culture indirect immunoperoxidase (TC-IPA) procedure, the shell vial assay [shell vials were pre- and postinoculation treated with medium containing 2 of 10% fetal bovine serum (FBS) or 100 micrograms% cortisol] (SV-IFA), and conventional (MRC-5) tube cultures (TC-CPE). CMV was detected in 25 (22%) of the 112 specimens tested by at least one of these methods. The detection/isolation of CMV among the 25 positive specimens in shell vials maintained with 2% FBS, 100 micrograms% cortisol + 2% FBS, and 10% FBS was 36, 44, and 52%, respectively. Detection/isolation of the virus from blood by TC-IPA and TC-CPE was 52% and 76%, respectively. A significantly greater CMV detection rate occurred using TC-CPE compared to SV-IFA treated with medium supplemented with an FBS concentration of 2% (P = .0132), but not medium containing the higher serum supplement or the glucocorticoid (P greater than .05). Differences in the identification of a CMV viremia were observed by IPA, SV-IFA, and TC-CPE methodologies on a patient-to-patient basis, denoting the necessity of incorporating each methodology into the CMV screening panel. Demographic analysis of 82 AIDS patients showed a CMV viremia prevalence of 9% (2/28) in intravenous drug users, 57% (27/47) in homosexual patients, and 22% (2/9) in heterosexual and transfusion patients. Overnight (24 hr) storage of whole blood at 4 or 24 degrees C, respectively, reduced CMV recovery by 40% and 65%, when tested by TC-CPE.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
46.
Pin-Nan Cheng Ru-Hsueh Wang I-Chin Wu Jaw-Ching Wu Kuo-Chih Tseng Kung-Chia Young Ting-Tsung Chang 《Journal of clinical virology》2007,38(1):44-48
BACKGROUND: Hepatitis E virus infection (HEV) remains unclear in institutionalized psychiatric patients. OBJECTIVES: To investigate the prevalence and risk factors of HEV infection in a psychiatric institution in Taiwan. STUDY DESIGN: A total of 754 patients with psychiatric disorders were enrolled in the study. Clinical features, review of patient charts, and interviews with families were recorded for analysis. Antibody to HEV was tested using a commercial enzyme-linked immunosorbent assays. RESULTS: The prevalence of HEV infection in institutionalized patients was as high as 14.5%. Males had higher prevalence than females. It was also found prevalence increased significantly by age group. When compared with patients 30 years old or less, those in the 31-40 year old age group had an odds ratio of 4.89 [95% confidence interval (CI), 1.15-20.82], 41-50 years old of 6.30 (95% CI, 1.48-26.83), and 50 years or older of 6.20 (95% CI, 1.44-26.74). In multivariate logistic regression analysis, age and male gender were the independent risk factors. CONCLUSIONS: Institutionalized psychiatric patients had higher prevalence of HEV infection. In addition, there was an age-related increase in exposure to HEV with males that had a higher HEV seropositivity. 相似文献
47.
Han-Thing Tseng Lin-Tee Hsiue Chen-Chi M. Ma Hong-Bing Tsai 《Macromolecular chemistry and physics.》1996,197(7):2155-2164
Four series of copolyesters, namely BB6-DMT, BB5-DMT, BB6-DMI and BB5-DMI series, were prepared by melt polycondensation of dimethyl 4,4′-bibenzoate (BB) with a dimethyl phthalate (DMT: dimethyl terephthalate or DMI: dimethyl isophthalate) and an alkanediol (1,6-hexanediol or 1,5-pentanediol). The homopolyesters poly(hexamethylene 4,4′-bibenzoate) (BB6) and poly(pentamethylene 4,4′-bibenzoate) (BB5) exhibit a smectic phase. The thermotropic liquid crystalline and crystalline properties of the copolyesters are significantly influenced by the presence of the non-mesogenic rigid phthalate unit. All BB6-DMT copolyesters remain crystalline. As x, the molar fraction of the phthalate units in the diacid units, ≧ 0.7 the mesophase of the BB6-DMT copolyesters is destroyed completely. For BB5-DMT copolyesters, the mesophase disappears as x ≧ 0.4, and the copolyesters become amorphous as 0.5 ≦ x ≦ 0.8. The mesophase and the crystallinity of the BB6-DMI copolyesters are destroyed completely as x > 0.5. The BB5-DMI copolyesters lose the mesophase as x ≧ 0.3, and become amorphous as x ≧ 0.4. The results indicate that the non-linear isophthalate unit destroys mesophase and crystallinity of the copolyesters to a greater extent than the para-linked terephthalate unit. 相似文献
48.
Tseng YW Scholz JP Schöner G Hotchkiss L 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2003,149(3):276-288
Given the number of muscles and joints of the arm, more ways are available to produce an identical hand movement when pointing
to a target than are strictly necessary. How the nervous system manages these abundant degrees of freedom was the focus of
this study of pointing to targets of low and high indices of difficulty (ID). Two essential features of movement synergies
were examined. The first reflects the preferred relations among the outputs of each movement element and was studied through
principal component analysis. The second feature of synergy reflects the flexibility of those relationships evidenced by the
use of multiple, goal-equivalent solutions to joint coordination. This second feature, which is the main focus of this report,
was studied using the uncontrolled manifold approach. Motor abundance was defined operationally as the component of variance
of joint combinations that left unchanged the value of important performance variables (goal-equivalent variability, GEV).
This variance component was contrasted with the component of variance leading to a change in the value of these variables
(non-goal-equivalent variability, NGEV). The difference between GEV and NGEV was evaluated with respect to the performance
variables movement extent, movement direction, and path of the arm's center of mass. More than 90% of the variance of joint
motions across the pointing trial were accounted for by one principal component, indicating a consistent temporal coupling
among most joint motions in a single functional synergy. The flexible nature of this synergy was revealed by the variability
analysis. All subjects had significantly higher GEV than NGEV for most of the movement path. Thus, variable patterns of joint
coordination did not represent noise but the use of equivalent coordinative solutions related to stabilizing important performance
variables. Higher GEV than NGEV was present regardless of the task's ID. One exception was at the time of peak velocity, leading
to poorer control of movement extent than movement direction. Increasing the task's ID led to an overall reduction of joint
configuraion variance, particularly GEV. These results support earlier work indicating that the use of goal-equivalent solutions
to joint coordination is a common feature of the control of this and many other motor tasks. Functionally important performance
variables appear to be controlled through flexible but task-specific coordination among the motor elements
Electronic Publication 相似文献
49.
Wide-field specular microscopy, slit-lamp examination, and pachometry were performed on 22 successful hard contact lens wearers and 22 controls matched for age, race, sex, and refractive error. A minimum of 600 cells per control and 1200 per contact lens wearer were manually digitized from the specular photomicrographs. Frequency distributions of cell areas were compared between the two groups using the parameters of mean, median, standard deviation, coefficient of variation, skewness and kurtosis. Slit-lamp examination was normal and there was no significant difference in corneal thickness between the patient group and the control group. Comparison of mean, median, and standard deviation also revealed no significant difference, but skewness (P less than .001), kurtosis (P less than .001) and coefficient of variation (P less than .004) were greater in the hard contact lens wear group. Hard contact lens wearing time correlated with increasing pleomorphism (P less than .05). Specular microscopy also revealed morphologic changes including deep stromal striae, intra- and extracellular "blackout" areas, and clustering of extremely small and large cells. The possible relationship between endothelial hypoxia and structural stromal changes are discussed. 相似文献
50.
Chen Du Megan Chong Hueh Zan Min Jung Cho Jenifer I. Fenton Pao Ying Hsiao Richard Hsiao Laura Keaver Chang-Chi Lai HeeSoon Lee Mary-Jon Ludy Wan Shen Winnie Chee Siew Swee Jyothi Thrivikraman Kuo-Wei Tseng Wei-Chin Tseng Stephen Doak Sara Yi Ling Folk Robin M. Tucker 《Nutrients》2021,13(2)
Background: The coronavirus disease 2019 (COVID-19) pandemic has increased the already high levels of stress that higher education students experience. Stress influences health behaviors, including those related to dietary behaviors, alcohol, and sleep; yet the effects of stress can be mitigated by resilience. To date, past research studying the connections between dietary behaviors, alcohol misuse, sleep, and resilience commonly investigated singular relationships between two of the constructs. The aim of the current study was to explore the relationships between these constructs in a more holistic manner using mediation and moderation analyses. Methods: Higher education students from China, Ireland, Malaysia, South Korea, Taiwan, the Netherlands, and the United States were enrolled in a cross-sectional study from April to May 2020, which was during the beginning of the COVID-19 pandemic for most participants. An online survey, using validated tools, was distributed to assess perceived stress, dietary behaviors, alcohol misuse, sleep quality and duration, and resilience. Results: 2254 students completed the study. Results indicated that sleep quality mediated the relationship between perceived stress and dietary behaviors as well as the relationship between perceived stress and alcohol misuse. Further, increased resilience reduced the strength of the relationship between perceived stress and dietary behaviors but not alcohol misuse. Conclusion: Based on these results, higher education students are likely to benefit from sleep education and resilience training, especially during stressful events. 相似文献