全文获取类型
收费全文 | 14605篇 |
免费 | 1375篇 |
国内免费 | 561篇 |
专业分类
耳鼻咽喉 | 86篇 |
儿科学 | 436篇 |
妇产科学 | 655篇 |
基础医学 | 4007篇 |
口腔科学 | 217篇 |
临床医学 | 1087篇 |
内科学 | 2220篇 |
皮肤病学 | 249篇 |
神经病学 | 1075篇 |
特种医学 | 146篇 |
外国民族医学 | 2篇 |
外科学 | 741篇 |
综合类 | 1438篇 |
现状与发展 | 4篇 |
一般理论 | 7篇 |
预防医学 | 1298篇 |
眼科学 | 236篇 |
药学 | 944篇 |
7篇 | |
中国医学 | 459篇 |
肿瘤学 | 1227篇 |
出版年
2024年 | 63篇 |
2023年 | 326篇 |
2022年 | 484篇 |
2021年 | 611篇 |
2020年 | 620篇 |
2019年 | 634篇 |
2018年 | 524篇 |
2017年 | 512篇 |
2016年 | 601篇 |
2015年 | 610篇 |
2014年 | 804篇 |
2013年 | 1066篇 |
2012年 | 712篇 |
2011年 | 857篇 |
2010年 | 697篇 |
2009年 | 757篇 |
2008年 | 742篇 |
2007年 | 694篇 |
2006年 | 687篇 |
2005年 | 549篇 |
2004年 | 489篇 |
2003年 | 443篇 |
2002年 | 406篇 |
2001年 | 325篇 |
2000年 | 232篇 |
1999年 | 211篇 |
1998年 | 203篇 |
1997年 | 196篇 |
1996年 | 176篇 |
1995年 | 168篇 |
1994年 | 106篇 |
1993年 | 97篇 |
1992年 | 109篇 |
1991年 | 81篇 |
1990年 | 72篇 |
1989年 | 75篇 |
1988年 | 57篇 |
1987年 | 55篇 |
1986年 | 67篇 |
1985年 | 73篇 |
1984年 | 57篇 |
1983年 | 50篇 |
1982年 | 45篇 |
1981年 | 52篇 |
1980年 | 53篇 |
1979年 | 36篇 |
1978年 | 19篇 |
1977年 | 4篇 |
1976年 | 19篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
O. B. Naumova 《Bulletin of experimental biology and medicine》1976,82(6):1858-1860
The nature of Rec+ revertants isolated previously from cultures of recombinationally defective strainEscherichia
coli K-12 AB 2463 recA13 was studied. With the aid of phage P1 vira the chromosome region of the recA gene in cells of strain JC2915F- were transduced, after which the recombination capacity of the transductants was determined by crossing with JC158Hfr cells and their resistance to ultraviolet radiation was established. Sensitivity of the transductants to suppressor phages was determined. The Rec+ revertants were shown to differ with respect to the recA gene. In some Rec+ revertants the Rec+ phenotype appeared as the result of a back mutation in this gene from rec- to rec+, whereas in other revertants the Rec+ phenotype was due to indirect suppression.Department of Biology and General Genetics, Patrice Lumumba Peoples' Friendship University, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. M. Zhdanov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 12, pp. 1487–1488, December, 1976. 相似文献
142.
Genetic variability of hepatitis C virus in chronically infected patients with viral breakthrough during interferon-ribavirin therapy 总被引:4,自引:0,他引:4
Vuillermoz I Khattab E Sablon E Ottevaere I Durantel D Vieux C Trepo C Zoulim F 《Journal of medical virology》2004,74(1):41-53
Little is known about hepatitis C virus (HCV) breakthrough during antiviral therapy, although it would help in understanding HCV resistance to current antiviral treatments. To analyse the implication of virological factors and the vigour of humoral immune responses in this phenomenon, we studied nine chronic hepatitis C patients with a viral breakthrough during IFN/ribavirin combination therapy, as well as five responders and five non-responders. The IRES and regions coding for the capsid protein, the PePHD domain of envelope glycoprotein E2 and the NS5A and 5B proteins were amplified by RT-PCR before treatment, before and during breakthrough, and after treatment. The major variant sequence was obtained by direct sequencing. The heterogeneity of quasispecies was studied by SSCP in all patients and sequencing after cloning in seven genotype 1b-infected patients. Humoral responses against HCV epitopes were also analysed. The major sequences of IRES, PePHD, and NS5B remained stable during treatment, regardless of the treatment response. However, the capsid protein and the regions flanking PePHD showed sequence variations in breakthrough patients, although no specific mutation was identified. The variable V3 region of NS5A, but not the PKR-binding domain and the ISDR, seemed to be associated with differences in response to treatment. The analysis of HCV quasispecies revealed no characteristic pattern during treatment in breakthrough patients, whose HCV genome profiles looked most similar to that of non-responders. The humoral response was similar between groups. In conclusion, viral breakthrough does not seem to be due to selection of resistant strains with signature mutations. 相似文献
143.
Melotte C Debrock S D'Hooghe T Fryns JP Vermeesch JR 《Human reproduction (Oxford, England)》2004,19(12):2777-2783
BACKGROUND: While preimplantation genetic diagnosis (PGD) is well established for carriers of reciprocal terminal translocations, reports on PGD for insertional translocation carriers are lacking. Here, we report on the PGD of an insertional translocation carrier with karyotype 46,XX,ins(14;2)(q21;q31q35). Due to the possibility of crossovers within the inserted region, rather than a single probe, four probes are required for proper embryo selection. METHODS: Probes were generated for PGD using fluorescence in situ hybridization and two PGD cycles. RESULTS: Analysis of 10 embryos revealed four embryos to be normal diploid. Two embryos were consistent with 3:1 segregation of the theoretical quadrivalent and one was consistent with 2:2 or 1:1 segregation. Furthermore, one embryo was mosaic abnormal and one remained without diagnosis. CONCLUSIONS: With increased acceptance of PGD, it is likely that more carriers of complex translocations will enter PGD programmes. The present results suggest that a careful genetic work-up of complex translocations is essential for proper embryo selection. While theoretical modelling may predict that quadrivalents will form during the meiosis of insertional translocations, experimental proof for the occurrence of quadrivalents is still lacking and more research on the meiotic process of both female and male insertional translocation carriers is warranted. 相似文献
144.
Strohl KP 《Respiratory physiology & neurobiology》2003,135(2-3):179-185
The episodic waxing and waning of ventilation is a fundamental event in sleep apnea syndromes. Post-hypoxic frequency decline (PHFD) and periodic breathing (PB) are evoked by brief hypoxic exposures in unanaesthetized and unrestrained inbred C57BL/6J mice, but not in A/J mice; and expression of PHFD differs not only among these mice strains but in among rat strains as well. These observations along with the current literature on genetic factors that operate on ventilatory behavior at rest and with chemosensory drive lead to the hypothesis that genetic factors infer some proportion of risk for the ventilatory instability observed in human sleep apnea syndromes. 相似文献
145.
应用两轮荧光原位杂交进行人类植入前胚胎染色体嵌合型的研究 总被引:1,自引:0,他引:1
目的应用2轮荧光原位杂交技术(fluorescence in situ hybridization,FISH)对人类植入前胚胎染色体嵌合型的发生机制和影响因素进行初步研究。方法选择体外受精与胚胎移植(in vitro fertilization-embryo transplantation,IVF-ET)治疗周期中不适于胚胎移植和冷冻的正常受精胚胎为研究对象,固定后进行2轮FISH,分析13、16、18、21、22、X、Y等7条染色体组成。结果51个胚胎中正常胚胎14个(27.5%),嵌合型16个(31.4%),无规律分裂12个(23.5%),异常非嵌合型9个(17.6%)。5~8细胞期胚胎中嵌合型胚胎的比例显著高于≤4细胞期胚胎(40.0%比12.5%)。非整倍体胚胎的比率在≥35岁组为57.1%,显著高于<35岁组(23.3%)。结论胚胎染色体嵌合型是植入前胚胎的常见现象,可能是影响IVF成功率的重要因素,而应用2轮FISH技术可有效地进行常见染色体异常的筛查。 相似文献
146.
C. Robert Cloninger 《American journal of medical genetics. Part A》1994,54(2):83-92
Despite extensive genomic scans, linkage studies of multiplex pedigrees have been unable to produce replicable evidence of genes predisposing to schizophrenia. This indicates that it is unlikely that a single gene accounts for a majority of cases of schizophrenia, even in multiplex pedigrees. It is most likely that schizophrenia is caused by the nonlinear interaction of multiple genetic and environmental factors influencing brain development and function. This conclusion has strong implications for the design of linkage and association studies. Recently designed linkage studies involve several improvements to deal with extensive locus heterogeneity and multiplicative interaction. These improvements include much larger samples of pedigrees, systematic ascertainment and sequential extension rules, and standardized procedures at multiple sites to facilitate collaboration and replication. Future improvements are likely to require advances in the assessment of clinical and neurobiological variability in multiplex pedigrees, more systematic environmental assessment, and advances in analytic methods to deal with multiplicative interaction. Rather than focusing only on schizophrenia as one or more discrete disorders, future linkage efforts should also consider the etiology of individual clinical syndromes or dimensional components of risk that interact to cause the complex pattern of syndromal comorbidity observed within schizophrenics and their families. © 1994 Wiley-Liss, Inc. 相似文献
147.
The purpose of this study was to establish the range of total serum IgE in a healthy population lacking personal and family history of allergy, as well as the influence of genetic factors (family history of allergy), environmental factors (degree of air pollution), age, and sex on the serum IgE levels. Using a commercial enzyme immunoassay (Phadezym IgE Prist) the mean serum level of IgE was determined in 363 non-atopic children from 0 to 12 years of age. The geometric mean of serum IgE increased according to age, indicating a positive correlation between both. Higher mean values of serum IgE were found for children with a family history of allergy, than for children without (27.82 and 14.49 U/ml respectively). The percentage of variation due to age was about 94.5% in children with no family history of allergy. The mean value of serum IgE increased with the degree of air pollution in the living area (15.49 U/ml in non-polluted areas, 20.78 U/ml in very polluted areas). However, the influence of air pollution was smaller than the influence of family history on the mean values of serum IgE. The mean value of serum IgE was not modified by sex. 相似文献
148.
The study of individuals at "high" risk for developing psychiatric disorders is useful in confirming that a biological trait marker identified in patient populations is also present in genetically susceptible individuals who have never been ill, and predicts the future onset of illness. We outline a systematic method for deciding which variables to choose and how many individuals are required in order for a study to have sufficient power. We demonstrate how these decisions depend on the assumptions that can be made with regard to the mode of inheritance of the biological trait, the relationship of the biological trait to illness, and the magnitude of the mean difference observed between patients and controls. We also quantify the increased power of studying offspring of two affected parents rather than offspring of one affected parent. 相似文献
149.
A combined segregation, linkage, and association analysis using the program COMBIN was performed on the simulated pedigree data prepared for the Second Genetic Analysis Workshop. The model used in COMBIN is described and the presented results illustrate its effectiveness in the analysis of such data. Linkage analysis was performed and maps for each linkage group are presented. 相似文献
150.
A model for concordance in a binary measure that does not rely on the assumption of an underlying latent liability dichotomized about a threshold has been demonstrated for twin pairs [Hannah et al, 1983]. It is extended here to pedigrees of arbitrary structure by making an assumption that is, for small incidence rates, almost equivalent to postulating that relative risks are multiplicative. The model is applied to the workshop data to determine the extent to which the known structure of the simulated models can be recovered. 相似文献