全文获取类型
收费全文 | 17290篇 |
免费 | 892篇 |
国内免费 | 109篇 |
专业分类
耳鼻咽喉 | 120篇 |
儿科学 | 247篇 |
妇产科学 | 143篇 |
基础医学 | 2255篇 |
口腔科学 | 401篇 |
临床医学 | 1048篇 |
内科学 | 4217篇 |
皮肤病学 | 285篇 |
神经病学 | 1364篇 |
特种医学 | 982篇 |
外科学 | 2627篇 |
综合类 | 67篇 |
预防医学 | 585篇 |
眼科学 | 441篇 |
药学 | 1262篇 |
中国医学 | 56篇 |
肿瘤学 | 2191篇 |
出版年
2023年 | 105篇 |
2022年 | 225篇 |
2021年 | 409篇 |
2020年 | 196篇 |
2019年 | 273篇 |
2018年 | 320篇 |
2017年 | 299篇 |
2016年 | 363篇 |
2015年 | 390篇 |
2014年 | 534篇 |
2013年 | 631篇 |
2012年 | 946篇 |
2011年 | 1073篇 |
2010年 | 623篇 |
2009年 | 526篇 |
2008年 | 924篇 |
2007年 | 1008篇 |
2006年 | 999篇 |
2005年 | 1047篇 |
2004年 | 1003篇 |
2003年 | 948篇 |
2002年 | 1005篇 |
2001年 | 360篇 |
2000年 | 354篇 |
1999年 | 368篇 |
1998年 | 290篇 |
1997年 | 218篇 |
1996年 | 229篇 |
1995年 | 190篇 |
1994年 | 168篇 |
1993年 | 161篇 |
1992年 | 227篇 |
1991年 | 239篇 |
1990年 | 223篇 |
1989年 | 206篇 |
1988年 | 176篇 |
1987年 | 157篇 |
1986年 | 149篇 |
1985年 | 115篇 |
1984年 | 95篇 |
1983年 | 65篇 |
1982年 | 61篇 |
1981年 | 45篇 |
1980年 | 33篇 |
1979年 | 57篇 |
1978年 | 48篇 |
1977年 | 37篇 |
1976年 | 30篇 |
1975年 | 20篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The extent of restriction fragment length polymorphism in genes for the arginine deiminase enzyme among 28 species of mycoplasmas was assessed by Southern blot analysis of DNA digested with EcoRI or TaqI nuclease probed with a 725-bp internal fragment of the arginine deiminase gene from Mycoplasma arginini. The results indicated unexpected heterogeneity among species of a single genus. 相似文献
92.
Iwasaki M Kobayashi K Suzuki H Anan K Ohno S Geng Z Li G Inoko H 《Tissue antigens》2000,56(2):136-142
Genetic polymorphism in the ABO blood group gene of Han, Kazak and Uygur populations inhabiting the most northwestern part of China was investigated using polymerase chain reaction-based techniques. The present study enrolled 43 healthy unrelated Han, 37 Kazak and 59 Uygur volunteers. The allele in A1 blood group is distinguished A0101 and A0102 in difference of nucleotide position 467. The A0101 allele is more frequent in Caucasian and the A0102 allele is characteristic in Mongoloid. It must be notable that A0201 in the A2 group (with a single base deletion at nucleotides 1059 to 1061) which was characteristic of Caucasian was observed in Kazak and Uygur populations but not in Han. Further, 00201 (with no nucleotide deletion at 261 and three nucleotide differences), which is frequent in different races including Caucasian except for Mongoloid, was detected also in Kazak and Uygur populations. The frequencies of B0101 in Kazak, Uygur and Han were comparable to those of other Asian populations but higher than those of Caucasian populations. Collectively, these results reveal that the allele frequencies of Kazak and Uygur at the ABO blood group locus are an intermediate between those of Mongoloid and Caucasian, suggesting the admixed feature of Kazak and Uygur with Mongoloid and Caucasian. 相似文献
93.
Sensitive and rapid detection of herpes simplex virus and varicella-zoster virus DNA by loop-mediated isothermal amplification 总被引:5,自引:0,他引:5
Loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method in which reagents react rapidly and efficiently, with a high specificity, under isothermal conditions. We used a LAMP assay for the detection of herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and varicella-zoster virus (VZV). The virus specificities of primers were confirmed by using 50 HSV-1, 50 HSV-2, and 8 VZV strains. The assay was performed for 45 min at 65 degrees C. The LAMP assay had a 10-fold higher sensitivity than a PCR assay. An analysis of nucleotide sequence variations in the target and primer regions used for the LAMP assay indicated that 3 of 50 HSV-1 strains had single nucleotide polymorphisms. No HSV-2 or VZV strains had nucleotide polymorphisms. Regardless of the sequence variation, there were no differences in sensitivity with the HSV-1-specific LAMP assay. To evaluate the application of the LAMP assay for clinical diagnosis, we tested clinical samples from 40 genital herpes patients and 20 ocular herpes patients. With the LAMP assay, 41 samples with DNA extraction and 26 direct samples without DNA extraction were identified as positive for HSV-1 or HSV-2, although 37 samples with DNA extraction and just one without DNA extraction were positive by a PCR assay. Thus, the LAMP assay was less influenced than the PCR assay by the presence of inhibitory substances in clinical samples. These observations indicate that the LAMP assay is very useful for the diagnosis of HSV-1, HSV-2, and VZV infections. 相似文献
94.
Miodrag ?oli? Vesna Ili? Milo? D. Pavlovi? Takuya Tamatani Masayuki Miyasaka 《Clinical & developmental immunology》1996,5(1):37-51
The effects of monoclonal antibodies (mAbs) to cell-surface molecules, divalent cations,
and various cell-signaling and metabolic inhibitors on the binding of thymocytes to rat
thymic dendritic cells (TDC) were studied using a rosette assay. It was found that TDC/thymocyte adhesion was stronger and faster at 37°C than at 4°C. Flow cytometric analysis demonstrated that bound thymocytes were predominantly CD4+CD8+ and CD4+CD8-, but in comparison to the phenotype of whole thymocytes, they were enriched in the mature
TCRαβhi subset. The binding of thymocytes to TDC at 37°C was almost completely
dependent on Ca2+ and Mg2+ and partly on an intact cytoskeleton and calmodulin-dependent
protein kinase. The adhesion was independent of new protein synthesis and the activities of protein kinases A and C, tyrosine kinases, as well as phosphotyrosine protein phosphatases. The TDC/thymocyte adhesion at 37°C was partly blocked by anti-LFA-1
(WT.1), anti-CD18 (WT.3), and anti-ICAM-1 (1A29) mAb. MAbs to class II MHC (OX-3 and OX-6), CD4 (W3/25), CD8 (OX-8), and αβTCR (R73) stimulated the adhesion via an LFA-1-dependent pathway, whereas an anti-CD45 mAb (G3C5) stimulated the rosette formation
independently of LFA-1. MAbs to CD2 (OX-34), CD11b (ED7), CD11b/c (OX-42), and class I MHC (OX-18) were without significant effects on the adhesion process. 相似文献
95.
Kitaichi N Kotake S Morohashi T Onoé K Ohno S Taylor AW 《Journal of leukocyte biology》2002,72(6):1117-1121
To evaluate the potential role of NK1.1 (CD161c) cells in autoimmune uveoretinitis, we treated experimental autoimmune uveoretinitis (EAU)-susceptible mice with anti-CD161c antibodies (PK136) to deplete natural killer (NK) cells. Injection of anti-CD161c antibodies deleted NK cells from the peripheral blood of EAU-susceptible mice. The T cell proliferative response against the ocular autoantigen K2 was not suppressed in mice treated with anti-CD161c antibody when compared with T cells from control mice. Although mice treated with anti-CD161c developed EAU, the clinical severity on days 17 and 19 after induction of EAU was significantly mild in anti-CD161c-treated mice compared with control mice. In addition, the histopathological severity of EAU was significantly milder in mice treated with anti-CD161c antibodies than controls 21 days after induction of EAU. Our results indicate that the severity of EAU is augmented by NK1.1(+) NK cells. 相似文献
96.
An invasion-independent pathway of blood-borne metastasis: a new murine mammary tumor model
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sugino T Kusakabe T Hoshi N Yamaguchi T Kawaguchi T Goodison S Sekimata M Homma Y Suzuki T 《The American journal of pathology》2002,160(6):1973-1980
It is generally believed that active invasion by cancer cells is essential to the metastatic process. In this report, we describe a murine mammary tumor (MCH66) model of metastasis that does not require invasion into the vascular wall of both the primary tumor and the target organ, in this case, the lung. The process involves intravasation of tumor nests surrounded by sinusoidal blood vessels, followed by intravascular tumor growth in the lung, without penetration of the vascular wall during the process. Comparative studies using a nonmetastatic MCH66 clone (MCH66C8) and another highly invasive metastatic cell line (MCH416) suggested that high angiogenic activity and sinusoidal remodeling of tumor blood vessels were prerequisites for MCH66 metastasis. Differential cDNA analysis identified several genes that were overexpressed by MCH66, including genes for the angiogenesis factor pleiotrophin, and extracellular matrix-associated molecules that may modulate the microenvironment toward neovascularization. Our analyses suggest that tumor angiogenesis plays a role in the induction of invasion-independent metastasis. This model should prove useful in screening and development of new therapeutic agents for cancer metastasis. 相似文献
97.
Zhang H Yamamoto T Nanba E Kitamura Y Terada T Akaboshi S Yuasa I Ohtani K Nakamoto S Takeshita K Ohno K 《American journal of medical genetics》1999,82(5):368-370
A Japanese patient with tuberous sclerosis (TSC), who manifested with multiple lung cysts and pneumothorax, is described. All exons of two TSC genes, TSC1 and TSC2, in peripheral blood leukocytes from the patient were analyzed by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). A novel T-to-G transition was found in exon 19 of TSC2 at nucleotide position 2168. This mutation caused an amino acid change, L717R. There was no such mutation in any other family members or in 100 normal Japanese. An automated sequencer-assisted quantitative analysis of normal and mutated SSCP-bands revealed no loss of heterozygosity (LOH) in the lung cyst tissue of the patient. 相似文献
98.
The patterns of DNA degradation in frozen, methanol-fixed, and formalin-fixed tissues were investigated by high-performance liquid chromatography (HPLC). The chromatograms all yielded one major peak with or without several extra minor peaks representing molecular weights of preserved genomic DNA. The most characteristic differences were in the retention times of the major peaks, with the earliest major peak occurring in the formalin-fixed tissues, and followed by the methanol-fixed, and frozen tissue samples, in that order. This means that the molecular weight of the DNA from formalin-fixed tissue is much shortened than that recovered from methanol-fixed tissue and frozen tissue. The results also indicated that a small amount of higher molecular weight DNA is still preserved in formalin-fixed tissues. To improve the amplification efficiency of polymerase chain reaction (PCR) analysis of formalin-fixed material, we isolated the higher molecular weight DNA from formalin-fixed, paraffin-embedded tissue from four different organs and compared the amplification efficiencies with those of the crude DNA extract. We used eight sets of oligonucleotide primers producing 262 to 989 base pair (bp) fragments of beta-globin. The results showed that the PCR amplification analyses were more efficient with the isolated higher molecular weight DNA than with the crude DNA extract. Our study demonstrated that not all the DNA in formalin-fixed, paraffin-embedded tissue samples is totally degraded but that a small amount of higher molecular weight DNA persists. The feasibility of molecular diagnosis using formalin-fixed material can be improved by isolating the preserved higher molecular weight DNA by HPLC. 相似文献
99.
Otsuka Y Ito M Yamaguchi M Saito S Uesu K Kasai K Abiko Y Mega J 《Mechanisms of ageing and development》2002,123(6):663-674
It is well known that Down syndrome (DS) is a premature ageing syndrome. Periodontal disease in individuals with DS develops rapidly and extensively in a relatively younger age bracket compared with that in healthy controls. The mechanisms involved in the periodontal inflammatory processes in DS patients are not fully understood. In the present study, the non-inflamed gingival fibroblasts isolated from seven patients with DS (DGF) and seven healthy controls (NDGF) were stimulated with lipopolysaccharide (LPS) derived from Actinobacillus actinomycetemcomitans (A. a.). We measured the level of prostaglandin E2 (PGE2) production by DGF and NDGF by radioimmunoassay, and also measured the mRNA expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) by using the real-time PCR method. We found the higher levels of LPS-stimulated COX-2 mRNA expression and PGE2 production in DGF when compared with those in NDGF. This study may indicate that overexpression of LPS-stimulated COX-2 induced a greater ability of DGF to produce PGE2, and that these phenomena may be responsible for the severer periodontal disease in DS patients. 相似文献
100.
Preparation of a protein micro-array using a photo-reactive polymer for a cell-adhesion assay 总被引:4,自引:0,他引:4
A protein micro-array, called a "cell chip" was constructed by using a photo-reactive polymer for a cell-adhesion assay. Various amounts of albumin or fibronectin were covalently immobilized on a polystyrene dish using a micro-spotter with a dip pen. First, poly(acrylic acid) carrying azidophenyl groups was synthesized as the photo-reactive polymer. Secondly, the aqueous solution of a photo-reactive polymer (several nanoliters) was cast using the dip pen of the micro-spotter and dried in air. Subsequently, aqueous solutions of proteins were cast on the same place using the micro-spotter. After drying, the dish was irradiated with ultraviolet light. Finally, the immobilization was confirmed by staining with a dye. The immobilization was stable even after washing with Tween-20. The protein-immobilized area depended on the manipulation of the micro-spotter and the size of the dip pen. Subsequently, cell adhesion on the photo-immobilized protein micro-array was investigated. The adhesion behavior of cells depended on the kind of immobilized proteins and the kind of cells. The protein micro-array will be useful for cell diagnosis and for the selection of biomaterials to regulate cell behavior. 相似文献