全文获取类型
收费全文 | 7996篇 |
免费 | 470篇 |
国内免费 | 76篇 |
专业分类
耳鼻咽喉 | 84篇 |
儿科学 | 144篇 |
妇产科学 | 190篇 |
基础医学 | 1250篇 |
口腔科学 | 720篇 |
临床医学 | 631篇 |
内科学 | 1342篇 |
皮肤病学 | 175篇 |
神经病学 | 565篇 |
特种医学 | 322篇 |
外科学 | 676篇 |
综合类 | 331篇 |
一般理论 | 1篇 |
预防医学 | 860篇 |
眼科学 | 88篇 |
药学 | 687篇 |
3篇 | |
中国医学 | 156篇 |
肿瘤学 | 317篇 |
出版年
2023年 | 58篇 |
2022年 | 126篇 |
2021年 | 214篇 |
2020年 | 160篇 |
2019年 | 191篇 |
2018年 | 243篇 |
2017年 | 185篇 |
2016年 | 204篇 |
2015年 | 236篇 |
2014年 | 341篇 |
2013年 | 382篇 |
2012年 | 583篇 |
2011年 | 645篇 |
2010年 | 357篇 |
2009年 | 299篇 |
2008年 | 493篇 |
2007年 | 509篇 |
2006年 | 395篇 |
2005年 | 397篇 |
2004年 | 292篇 |
2003年 | 253篇 |
2002年 | 199篇 |
2001年 | 166篇 |
2000年 | 155篇 |
1999年 | 137篇 |
1998年 | 77篇 |
1997年 | 75篇 |
1996年 | 62篇 |
1995年 | 52篇 |
1994年 | 55篇 |
1993年 | 45篇 |
1992年 | 57篇 |
1991年 | 51篇 |
1990年 | 55篇 |
1989年 | 39篇 |
1988年 | 47篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 38篇 |
1984年 | 29篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1959年 | 41篇 |
1958年 | 66篇 |
1957年 | 75篇 |
1956年 | 73篇 |
1955年 | 83篇 |
1954年 | 51篇 |
排序方式: 共有8542条查询结果,搜索用时 343 毫秒
51.
The CTLA-4 gene region of chromosome 2q33 is linked to, and associated with, type 1 diabetes. Belgian Diabetes Registry 总被引:8,自引:1,他引:8
Nistico L; Buzzetti R; Pritchard LE; Van der Auwera B; Giovannini C; Bosi E; Larrad MT; Rios MS; Chow CC; Cockram CS; Jacobs K; Mijovic C; Bain SC; Barnett AH; Vandewalle CL; Schuit F; Gorus FK; Tosi R; Pozzilli P; Todd JA 《Human molecular genetics》1996,5(7):1075-1080
Susceptibility to autoimmune insulin-dependent (type 1) diabetes mellitus
is determined by a combination of environmental and genetic factors, which
include variation in MHC genes on chromosome 6p21 (IDDM1) and the insulin
gene on chromosome 11p15 (IDDM2). However, linkage to IDDM1 and IDDM2
cannot explain the clustering of type 1 diabetes in families, and a role
for other genes is inferred. In the present report we describe linkage and
association of type 1 diabetes to the CTLA-4 gene (cytotoxic T lymphocyte
associated-4) on chromosome 2q33 (designated IDDM12). CTLA-4 is a strong
candidate gene for T cell- mediated autoimmune disease because it encodes a
T cell receptor that mediates T cell apoptosis and is a vital negative
regulator of T cell activation. In addition, we provide supporting evidence
that CTLA-4 is associated with susceptibility to Graves' disease, another
organ- specific autoimmune disease.
相似文献
52.
MICHÈLE COUTARD MARY OSBORNE-PELLEGRIN 《International journal of experimental pathology》1996,77(2):53-62
Microscopic aneurysmal-like structures (ALS) develop spontaneously in the convoluted rat testicular artery and have been previously proposed as a model relevant to cerebral aneurysms. The effect of defects in connective tissue fibres on ALS formation was investigated by microscopy using two approaches: (i) the study of the effect of β-aminopropionitrile (BAPN), an inhibitor of the cross-linking of elastic and collagen fibres, on the incidence, size and morphology of ALS in spontaneously hypertensive rats (SHR) and their normotensive controls (WKY). The straight spermatic artery was studied for comparison. (ii) The determination of the incidence of spontaneous ALS in Brown Norway (BN) and Long Evans (LE) rats which are highly susceptible (BN) or resistant (LE) to the spontaneous rupture of the arterial internal elastic lamina. (i) BAPN increased the number and size of ALS in SHR and WKY rats and had no effect on the straight spermatic artery and (ii) ALS were more numerous and of greater size in BN than in LE rats. Taken together, these results show that defective connective tissue fibres may favour the formation and induce the enlargement of aneurysmal-like structures. By analogy, these data suggest that a lack of connective tissue fibre integrity may be of importance in cerebral aneurysm formation and development. 相似文献
53.
54.
55.
We present the results of the Vicker's hardness test and the use of near-infrared Raman spectroscopy (RS) to measure in vitro the degree of conversion (DC) of a bis(phenol)-A-glycidyl-dimethacrylate-based composite resin, photoactivated by both a halogen lamp (power density=478 mW/cm(2); 8-mm diameter spot) and an argon laser (power density=625 mW/cm(2); 7-mm diameter spot). The degree of conversion was estimated by analyzing the relative intensities between the aromatic C=C stretching Raman mode at 1610 cm(-1) and the methacrylate C=C stretching Raman mode (1640 cm(-1)) on top and bottom surfaces. For the hardness evaluation, the samples were embedded in polyester resin and three indentations with a 50-g load for 10 s were made on the top surface. The higher relative DC values achieved by the photoactivation of a composite resin by the argon laser suggest a better biocompatibility in the bottom surface. The correlation test showed that the higher Vicker's hardness number (VHN) values were associated with higher DC values. The derivative analysis showed a greater curing rate from 5 to 20 s of exposure. The comparison of VHN and DC values with both light sources at each curing time showed that a small change in conversion is related to a large change in hardness. Raman spectroscopy is more sensitive to changes in the first stages of curing reaction than later ones, and the Vicker's hardness assay is more sensitive to changes in the last stages. 相似文献
56.
Characterization of melanocyte stimulating hormone receptor variant alleles in twins with red hair 总被引:7,自引:3,他引:7
The association between MSHR coding region variation and hair colour in
humans has been examined by genotyping 25 red haired and 62 non-red
Caucasians, all of whom were 12 years of age and members of a twin pair
study. Twelve amino acid substitutions were seen at 11 different sites,
nine of these being newly described MSHR variants. The previously reported
Val92Met allele shows no association with hair colour, but the three
alleles Arg151Cys, Arg160Trp and Asp294His were associated with red hair
and one Val60Leu variant was most frequent in fair/blonde and light brown
hair colours. Variant MSHR genotypes are associated with lighter skin types
and red hair (P < 0.001). However, comparison of the MSHR genotypes in
dizygotic twin pairs discordant for red hair colour indicates that the MSHR
gene cannot be solely responsible for the red hair phenotype, since five of
13 pairs tested had both haplotypes identical by state (with three of the
five having both identical by descent). Rather, it is likely that
additional modifier genes exist, making variance in the MSHR gene necessary
but not always sufficient, for red hair production.
相似文献
57.
Gil LH Alves FP Zieler H Salcedo JM Durlacher RR Cunha RP Tada MS Camargo LM Camargo EP Pereira-da-Silva LH 《Journal of medical entomology》2003,40(5):636-641
Studies on seasonal anopheline fauna variation were performed in two distinct settlements in the State of Rond?nia, Brazil: one at the Madeira River banks (Portuchuelo) with stable native Amazonian population; the other at an inland lumber-extracting farm (Urupá) in dry land, in which adults are mostly migrants. During a 6-yr period (1994-2000), 8,638 adult anophelines were collected: 2,684 in Urupá and 5,954 in Portuchuelo. Anopheles darlingi represented >95% of total mosquitoes caught. Dissection of 4,424 A. darlingi females yielded a very low sporozoite infection index below 0.1%. Oocysts were found in both localities in approximately 0.1% of dissected mosquitoes. Determination of the hour biting rates disclosed seasonal variations in both localities. However, in Portuchuelo, mosquito density peaked at the acme of the rainy season, whereas at Urupá it peaked in the dry season. The increase in mosquito density and incidence of malaria cases were coincident. The high mosquito densities observed in the riverine settlement of Portochuelo sector B, which permits evaluation in > 10,000 mosquitoes' bites/person/year, could explain, in spite of the low mosquito's infection index, the previously described development of natural immunity in the local population that is not observed in the dry land agroindustrial settlement of Urupá. 相似文献
58.
BALB/c mice are susceptible to cutaneous lelshmanlasls uponinfection with Leishmania major while C57BL/6 are not. Thereis a major promastigote surface protease (PSP or gp63) whichis available in both native and recomblnant forms, and for whichthe primary amlno acid sequence is known. Immunization withPSP has been shown to offer some protection against challengewith the live organism. Therefore, we attempted to develop apeptide vaccine with PSP peptldes. In the first experiments,recall prollferatlve responses to PSP were measured using aset of 15mer peptldes spanning the entire PSP molecule whichallowed designation of major determinant regions in BALB/c,C57BL/6, and CBA mice. Several of these determinants were promiscuousand shared almost the identical core amlno acid residues inthe different strains. Immunization with major determinant peptldeswas recalled vigorously with L. major soluble antigen as wellas with PSP. The response to peptide was almost entirely Th1as measured by a localized ELISA assay for single-cell productionof IFN-. A similar assay for IL-5, which overcomes problemsof sensitivity and inhibition by lymphoklnes produced by Th1cells, Indicates very little production of Th1 cells even byBALB/c. It was found that if a major responsive peak was examinedby recall with overlapping peptldes, the highest, central peptidegave a mainly Th1 response while the boundary, less efficientpeptldes gave more of a Th2 response. Possible reasons for thiswere discussed. These results point to the importance of selectingthe exactly appropriate peptide in considering a vacclnogenthat might protect susceptible individuals. Even the choiceof a somewhat immunogenlc peptide within the determinant envelopemight actually exacerbate infection by steering the responsein a Th2 direction. 相似文献
59.
Kirov AS Piao JZ Mathur NK Miller TR Devic S Trichter S Zaider M Soares CG LoSasso T 《Physics in medicine and biology》2005,50(13):3063-3081
The need for fast, accurate and high resolution dosimetric quality assurance in radiation therapy has been outpacing the development of new and improved 2D and 3D dosimetry techniques. This paper summarizes the efforts to create a novel and potentially very fast, 3D dosimetry method based on the observation of scintillation light from an irradiated liquid scintillator volume serving simultaneously as a phantom material and as a dose detector medium. The method, named three-dimensional scintillation dosimetry (3DSD), uses visible light images of the liquid scintillator volume at multiple angles and applies a tomographic algorithm to a series of these images to reconstruct the scintillation light emission density in each voxel of the volume. It is based on the hypothesis that with careful design and data processing, one can achieve acceptable proportionality between the local light emission density and the locally absorbed dose. The method is applied to a Ru-106 eye plaque immersed in a 16.4 cm3 liquid scintillator volume and the reconstructed 3D dose map is compared along selected profiles and planes with radiochromic film and diode measurements. The comparison indicates that the 3DSD method agrees, within 25% for most points or within approximately 2 mm distance to agreement, with the relative radiochromic film and diode dose distributions in a small (approximately 4.5 mm high and approximately 12 mm diameter) volume in the unobstructed, high gradient dose region outside the edge of the plaque. For a comparison, the reproducibility of the radiochromic film results for our measurements ranges from 10 to 15% within this volume. At present, the 3DSD method is not accurate close to the edge of the plaque, and further than approximately 10 mm (<10% central axis depth dose) from the plaque surface. Improvement strategies, considered important to provide a more accurate quick check of the dose profiles in 3D for brachytherapy applicators, are discussed. 相似文献
60.
目的:通过体外和体内方法研究β-casomorphin-7对小鼠脾脏淋巴细胞和腹腔巨噬细胞的作用.方法:利用脾细胞增殖试验和腹腔巨噬细胞中NO浓度的变化来研究体外不同的β-casomorphin-7浓度对脾脏淋巴细胞的增殖和腹腔巨噬细胞中NO浓度变化的影响,以及腹腔注射β-casomorphin-7和饮用β-casomorphin-7溶液对上述两个指标的影响.结果:体外试验表明,β-casomorphin-7在不同浓度对脾脏淋巴细胞的增殖显示了刺激和抑制的双向作用,而对NO的产生显示了明显的抑制作用(P<0.01).体内试验表明,β-casomorphin-7通过腹腔注射和饮用两种给药方式对脾淋巴细胞和腹腔巨噬细胞的作用是一致的.β-casomorphin-7显著地增强了脾淋巴细胞的增殖反应(P<0.01),且抑制了腹腔巨噬细胞NO的产生.结论:当前的试验表明,β-casomorphin-7具有免疫调节作用,且小鼠在2~3周龄时,可吸收入血发挥免疫调节作用. 相似文献