全文获取类型
收费全文 | 34837篇 |
免费 | 3623篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 206篇 |
儿科学 | 1124篇 |
妇产科学 | 967篇 |
基础医学 | 4904篇 |
口腔科学 | 705篇 |
临床医学 | 4166篇 |
内科学 | 6278篇 |
皮肤病学 | 548篇 |
神经病学 | 3029篇 |
特种医学 | 1492篇 |
外国民族医学 | 3篇 |
外科学 | 4435篇 |
综合类 | 763篇 |
一般理论 | 43篇 |
预防医学 | 4261篇 |
眼科学 | 887篇 |
药学 | 2612篇 |
中国医学 | 45篇 |
肿瘤学 | 2021篇 |
出版年
2022年 | 270篇 |
2021年 | 612篇 |
2020年 | 327篇 |
2019年 | 575篇 |
2018年 | 606篇 |
2017年 | 465篇 |
2016年 | 517篇 |
2015年 | 549篇 |
2014年 | 762篇 |
2013年 | 1146篇 |
2012年 | 1632篇 |
2011年 | 1597篇 |
2010年 | 948篇 |
2009年 | 850篇 |
2008年 | 1456篇 |
2007年 | 1540篇 |
2006年 | 1538篇 |
2005年 | 1471篇 |
2004年 | 1433篇 |
2003年 | 1343篇 |
2002年 | 1279篇 |
2001年 | 1189篇 |
2000年 | 1202篇 |
1999年 | 1036篇 |
1998年 | 443篇 |
1997年 | 403篇 |
1996年 | 383篇 |
1995年 | 319篇 |
1994年 | 353篇 |
1993年 | 338篇 |
1992年 | 822篇 |
1991年 | 783篇 |
1990年 | 774篇 |
1989年 | 677篇 |
1988年 | 695篇 |
1987年 | 655篇 |
1986年 | 605篇 |
1985年 | 662篇 |
1984年 | 538篇 |
1983年 | 421篇 |
1982年 | 268篇 |
1981年 | 289篇 |
1980年 | 260篇 |
1979年 | 464篇 |
1978年 | 345篇 |
1977年 | 260篇 |
1976年 | 280篇 |
1974年 | 285篇 |
1973年 | 261篇 |
1972年 | 268篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Roscoe Taylor Jeff Bazelmans Robert Golec Simon Oakes 《Australian and New Zealand journal of public health》1995,19(5):455-459
Abstract: To investigate the distribution of blood lead levels in a sample of Victorian children, and to compare current levels with those from a similar survey in 1979, blood was tested for lead in 252 children (123 under five years) attending Royal Children's Hospital as outpatients and having venepuncture blood samples for medical reasons. Blood lead levels were determined by graphite furnace atomic absorption spectrophotometer. The mean blood lead level was 0.26 μmol/L (5.4 μg/dL). In the under-five age group, the mean was 0.28 μmol/L (5.7 μg/dL). Only 1.6 per cent of this group exceeded the National Health and Medical Research Council action level of 0.72 μmol/L (15 μg/dL). Levels in this age group have declined significantly since 1979, when the mean was 0.54 μmol/L (11.1 μg/dL) and 12.9 per cent exceeded 0.72 μmol/L (15 μg/dL). Average blood lead levels have halved since 1979, with likely contributing factors being reduced exposure from lead in diet, reduced access to lead in paint and reduced lead in ambient air. Children with elevated levels had identifiable risk factors such as pica or exposure to lead-based paint, suggesting the need for ongoing public health action to prevent exposure in these groups. 相似文献
92.
The effect of cigarette smoking on ovarian function and early pregnancy outcome of in vitro fertilization treatment 总被引:3,自引:0,他引:3
A retrospective analysis of the results of the first attempt at in vitro fertilization (IVF) treatment in 447 couples was performed by chart review. In 124 couples the female partners smoked cigarettes, and in 236 couples they did not. A total of 69 pregnancies (19.2%) were achieved, 50 in nonsmokers (21.2% per cycle), and 19 in smokers (15.3% per cycle). There were no significant differences in these cycles between the two groups in peak estradiol level achieved, the number of eggs retrieved, fertilization rate, or implantation rate. The incidence of spontaneous abortion was higher in smokers (42.1%) than in nonsmokers (18.9%). Consequently, the delivery rate per cycle of IVF was significantly lower in the smoking group (11 of 124, 9.6%) than in the nonsmokers (40 of 236, 17.0%). There was no effect when only the husband was a smoker. From these data, smoking appears to significantly reduce the chances of successful pregnancy after IVF treatment. 相似文献
93.
94.
Lynn R. Sorbara Zhichun Tang Alessandro Cama Jinru Xia Esther Schenker Ronald A. Kohanski Leonid Poretsky Elizabeth Koller Simeon I. Taylor Andrea Dunaif 《Metabolism: clinical and experimental》1994,43(12)
Women with polycystic ovary syndrome (PCOS) are markedly insulin-resistant, but the molecular mechanisms of these changes and their relationship to the hyperandrogenic state remain to be clarified. Mutations have recently been identified in the insulin receptor gene of patients with extreme forms of insulin resistance associated with hyperandrogenism (eg, type A insulin resistance), and these mutations account for the insulin resistance in such patients. We performed this study to determine whether mutations in the coding portion of the insulin receptor gene were responsible for insulin resistance in PCOS. Insulin binding studies using cultured skin fibroblasts of three obese (body mass index > 27 kg/m2) women with PCOS (ie, mild hyperandrogenemia and chronic anovulation of unknown etiology) and documented insulin resistance showed no apprarent abnormalities in either the number or affinity of insulin binding sites. Direct sequencing of all 22 exons of the insulin receptor gene from two of the women with PCOS did not reveal any mutations. Furthermore, both alleles of the gene were expressed at equal levels. In a third insulin-resistant PCOS woman, there was no evidence for a mutation in the coding portion of the insulin receptor gene as determined by denaturing gradient gel electrophoresis (DGGE). We conclude that the insulin resistance in these PCOS women was caused by a defect extrinsic to the insulin receptor. 相似文献
95.
C van Kerckhove L Luyrink J Taylor H Melin-Aldana K Balakrishnan W Maksymowych M Elma D Lovell E Choi D N Glass 《The Journal of rheumatology》1991,18(6):874-879
To further investigate a clinical impression that patients with early onset pauciarticular juvenile rheumatoid arthritis (EOPA-JRA) who carry HLA-DQw1 have more severe arthritis, we subtyped HLA-DQw1 in American midwestern patients with EOPA-JRA. The HLA-DQA1*0101 subtype was present in 10 of 19 patients who developed persistent polyarticular erosive disease compared with 18 of 92 healthy controls (chi 2 = 9.13, p = 0.003, RR = 4.6), and occurred more frequently in this polyarticular group than in patients without polyarticular erosive disease (chi 2 = 4.11, p = 0.040, RR = 3.0). The presence of HLA-DQA1*0101 was significantly lower in patients with chronic iridocyclitis than in patients without chronic iridocyclitis (chi 2 = 7.07, p = 0.008, RR = 0.21). In HLA-DQA1*0101 positive patients, DNA sequences of the beta-1 domain of the HLA-DQ alpha and HLA-DQ beta genes (HLA-DQA1*0101, HLA-DQB1*0501 and HLA-DQB1*0503) were identical to those in controls. In this midwestern EOPA-JRA population, HLA-DQA1*0101 or genes in linkage disequilibrium with it, are associated with a cohort of patients with EOPA-JRA with distinct clinical characteristics. 相似文献
96.
Two patients with acutely thrombosed femorofemoral bypass grafts are presented. Recombinant human tissue-type plasminogen activator (rt-PA) was used successfully in thrombolysis of the occluded grafts. Utilizing a new technique the grafts were punctured directly and bolus doses of rt-PA administered. 相似文献
97.
J E Taylor R A MacTier I S Henderson J J Belch W K Stewart 《Peritoneal dialysis international》1992,12(2):221-226
OBJECTIVE: To determine the effect of subcutaneous erythropoietin treatment on dialysis efficiency in continuous ambulatory peritoneal dialysis (CAPD) patients. DESIGN: Dialysis efficiency, platelet and white cell aggregation, and red cell deformability were measured monthly for six months in nine anaemic CAPD patients treated with erythropoietin, and on a single occasion in seven control CAPD patients with intrinsically high haemoglobin concentrations. SETTING: Renal dialysis unit. PATIENTS: Nine patients stable on CAPD for a minimum of six months and with haemoglobin concentrations less than 8.5 g/dl were treated with erythropoietin. Seven CAPD patients matched for age and renal function, with haemoglobins greater than 9.0 g/dl served as controls. RESULTS: Daily peritoneal clearances and net ultrafiltration volumes were unchanged when haematocrit increased from 25.0 +/- 2.2% to 36.5 +/- 3.5%. Spontaneous whole blood platelet aggregation was significantly increased from week twelve (pre-treatment aggregation 46 +/- 23%; 12 weeks: 67 +/- 19%, p less than 0.05; 16 weeks: 64 +/- 19%, p less than 0.01; 20 weeks: 71 +/- 16%, p less than 0.01; 24 weeks: 73 +/- 10%, p less than 0.01). CONCLUSIONS: The increase in haematocrit and platelet aggregation associated with erythropoietin treatment did not affect peritoneal clearances or ultrafiltration capacity. 相似文献
98.
R. Grant Steen Suzanne A. Gronemeyer Peter B. Kingsley Wilbum E. Reddick James S. Langston June S. Taylor 《Journal of magnetic resonance imaging : JMRI》1994,4(5):681-691
Precise and accurate inversion-recovery (PAIR) magnetic resonance (MR) measurements of T1 were obtained in eight brain regions and cerebrospinal fluid of 26 healthy volunteers. Accuracy of the technique was assessed by measuring T1 in small fluid volumes with the PAIR technique and with two independent spectroscopic techniques. The mean difference between T1 measured with PAIR and with the two spectroscopic techniques was 3.1% ± 1.3. The precision (reproducibility) of measurements with the PAIR technique was excellent. The coefficient of variation (CV) across 16 measurements in a head phantom was 2.0%, compared with a CV of 2.7% across 45 separate measurements in a single subject. The within-subject CV was 1.8% ± 0.6 in white matter and 1.4% ± 1.0 in basal ganglia. The between-subject CV in 26 healthy volunteers was 3.6% ± 0.6 in white matter and 4.1% ± 1.9 in basal ganglia. Comparison between a patient with an active recurrent brain tumor and an agematched patient with an inactive brain tumor showed that T1 was significantly elevated throughout the brain of the active-tumor patient, especially in white matter tracts, even though no tumor or edema was detected in the white matter on standard MR images. Comparisons between five brain tumor patients and four healthy volunteers of similar age showed that T1 was significantly and substantially elevated throughout the white matter tracts and in the caudate nucleus, putamen, and thalamus. These results are consistent with the hypothesis that white matter tracts are selectively vulnerable to edema and that T1 increases in white matter are a sensitive indicator of patient status or tumor aggressiveness. 相似文献
99.
The genomic structures of spirochete species are not well characterized, and genetic studies on these organisms have been hampered by lack of a genetic exchange mechanism in these bacteria. In view of these observations, pulsed-field gel electrophoresis was used to examine the genomes of Leptospira species. Live cells, prepared in agarose plugs, were lysed in situ, and the DNA was analyzed under different electrophoretic conditions. Pulsed-field gel electrophoresis of DNA digested with infrequently cutting restriction enzymes showed that the genome of Leptospira interrogans serovar canicola is approximately 3.1 Mb, while that of the saprophytic L. biflexa serovar patoc I is 3.5 Mb. DNA forms of approximately 2,000 and 350 kb which were present in samples from L. interrogans serovars were not readily detected in nonpathogenic serovars. Three distinct populations, designated type alpha, beta, and gamma, of L. interrogans DNA molecules were further analyzed with two-dimensional gel electrophoresis. Evidence suggested that two of these DNA forms, type alpha and gamma, were linear structures. Pulsed-field gel electrophoresis has proven to be a valuable tool with which to size bacterial genomes and to take the first steps toward characterization of a form of leptospiral DNA which behaves as a linear molecule and which may be related to the virulence of L. interrogans. 相似文献
100.
This article describes how genetic components of disease susceptibility can be evaluated in case-control studies, where cases and controls are sampled independently from the population at large. Subjects are assumed unrelated, in contrast to studies of familial aggregation and linkage. The logistic model can be used to test collapsibility over phenotypes or genotypes, and to estimate interactions between environmental and genetic factors. Such interactions provide an example of a context where non-hierarchical models make sense biologically. Also, if the exposure and genetic categories occur independently and the disease is rare, then analyses based only on cases are valid, and offer better precision for estimating gene-environment interactions than those based on the full data. 相似文献