全文获取类型
收费全文 | 17526篇 |
免费 | 1278篇 |
国内免费 | 1157篇 |
专业分类
耳鼻咽喉 | 83篇 |
儿科学 | 120篇 |
妇产科学 | 132篇 |
基础医学 | 3260篇 |
口腔科学 | 212篇 |
临床医学 | 699篇 |
内科学 | 1883篇 |
皮肤病学 | 207篇 |
神经病学 | 1776篇 |
特种医学 | 358篇 |
外国民族医学 | 5篇 |
外科学 | 732篇 |
综合类 | 4617篇 |
现状与发展 | 4篇 |
预防医学 | 738篇 |
眼科学 | 194篇 |
药学 | 2584篇 |
中国医学 | 1275篇 |
肿瘤学 | 1082篇 |
出版年
2024年 | 26篇 |
2023年 | 93篇 |
2022年 | 219篇 |
2021年 | 276篇 |
2020年 | 311篇 |
2019年 | 290篇 |
2018年 | 268篇 |
2017年 | 460篇 |
2016年 | 486篇 |
2015年 | 548篇 |
2014年 | 832篇 |
2013年 | 1077篇 |
2012年 | 1002篇 |
2011年 | 1199篇 |
2010年 | 1008篇 |
2009年 | 935篇 |
2008年 | 1012篇 |
2007年 | 1043篇 |
2006年 | 1029篇 |
2005年 | 827篇 |
2004年 | 803篇 |
2003年 | 716篇 |
2002年 | 609篇 |
2001年 | 526篇 |
2000年 | 474篇 |
1999年 | 418篇 |
1998年 | 323篇 |
1997年 | 279篇 |
1996年 | 307篇 |
1995年 | 279篇 |
1994年 | 254篇 |
1993年 | 247篇 |
1992年 | 210篇 |
1991年 | 162篇 |
1990年 | 150篇 |
1989年 | 128篇 |
1988年 | 129篇 |
1987年 | 106篇 |
1986年 | 97篇 |
1985年 | 128篇 |
1984年 | 122篇 |
1983年 | 57篇 |
1982年 | 98篇 |
1981年 | 93篇 |
1980年 | 62篇 |
1979年 | 45篇 |
1978年 | 44篇 |
1977年 | 34篇 |
1976年 | 33篇 |
1970年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Eduard I Dedkov Mathew T Thomas Milan Sonka Fuxing Yang Thomas W Chittenden John M Rhodes Michael Simons Erik L Ritman Robert J Tomanek 《Developmental dynamics》2007,236(7):2004-2010
Syndecan-4 and its cytoplasmic binding partner, synectin, are known to play a role in FGF-2 signaling and vascular growth. To determine their roles in coronary artery/arteriolar formation and growth, we compared syndecan-4 and synectin null mice with their wild-type counterparts. Image analysis of arterioles visualized by smooth muscle alpha-actin immunostaining revealed that synectin (-/-) mice had lower arteriolar length and volume densities than wild-type mice. As shown by electron microscopic analysis, arterioles from the two did not differ in morphology, including their endothelial cell junctions, and the organization and distribution of smooth muscle. Using micro-computer tomography, we found that the size and branching patterns of coronary arteries (diameters > 50 microm) were similar for the two groups, a finding that indicates that the growth of arteries is not influenced by a loss of synectin. Syndecan-4 null male mice also had lower arteriolar length densities than their gender wild-type controls. However, female syndecan-4 null mice were characterized by higher arteriolar length and volume densities than their gender-matched wild-type controls. Thus, we conclude that both synectin and syndecan-4 play a role in arteriolar development, a finding that is consistent with previous evidence that FGF-2 plays a role in coronary arterial growth. Moreover, our data reveal that gender influences the arteriolar growth response to syndecan-4 but not to synectin. 相似文献
93.
Qian BF El-Salhy M Melgar S Hammarström ML Danielsson A 《Clinical and experimental immunology》2000,120(3):424-433
Neuroendocrine peptides have a variety of physiological functions in the gastrointestinal tract. This study was carried out to investigate the impact of IL-2 deficiency on the neuroendocrine system in normal colon, and the neuroendocrine changes during colonic inflammation. Mice with homozygous disrupted IL-2 gene (IL-2-/-) spontaneously developed a bowel disease with similarities to human ulcerative colitis. Different types of colonic endocrine cells and myenteric nerves were analysed in the IL-2-/- mice using immunomorphometry. The neuropeptide contents in the colonic tissues were determined by radioimmunoassay. Age-matched healthy IL-2+/- and IL-2+/+ mice served as controls and the colonic IL-2 levels were compared between these two groups of mice by ELISA. Our data showed that less than half the amount of IL-2 was synthesized in the colon of IL-2+/- mice compared with the IL-2+/+ wild-type mice. Two major differences in the neuroendocrine colon were found between the mice with an intact and disrupted IL-2 gene. One was age-related. The frequencies of various endocrine cells and myenteric nerves increased with age in the IL-2+/+ mice. However, no such increases were seen in the mice with a disrupted IL-2 gene. Instead, the volume densities of enteroglucagon, serotonin cells and substance P (SP), vasoactive intestinal polypeptide (VIP) and total myenteric nerves were lower in the older IL-2+/- and IL-2-/- mice compared with the wild type. The other was disease-related. Polypeptide YY (PYY) cells and tissue levels of PYY, SP and VIP were significantly decreased in the IL-2-/- mice during the course of bowel inflammation compared with the healthy IL-2+/- and IL-2+/+ controls. These findings indicate that colonic neuroendocrine alterations did occur in the mice with a disrupted IL-2 gene and diminished local IL-2 level, suggesting a role of IL-2 in the regulation of the neuroendocrine system and a prevalent interaction between the immune and neuroendocrine systems in normal colon. On the other hand, there were some changes that seemed to correlate with the bowel inflammatory process. They might be associated with the impaired function in inflamed gut and contribute to the development and/or prolongation of disease. 相似文献
94.
William Walker Craig W. Roberts James M. Brewer James Alexander 《European journal of immunology》1995,25(5):1426-1430
These studies describe the production of specific antibodies in human peripheral blood lymphocyte-reconstituted severe-combined immunodeficient (PBL-SCID) mice following vaccination with antigen from the protozoan parasite Toxoplasma gondii. To determine the effect of previous exposure of the lymphocyte donor to antigen, human-PBL-SCID animals were created by transferring peripheral blood lymphocytes from either a single T. gondii-seronegative or a single seropositive donor. These reconstituted animals were subsequently inoculated with T. gondii soluble tachyzoite antigen (STAg) entrapped within non-ionic surfactant vesicles as an immunological adjuvant. Animals were bled at pre-determined time points post-vaccination and the expression of human anti-STAg antibodies in the plasma determined by enzyme-linked immunosorbent assay. Human antibodies specific for STAg were readily inducible in both groups of reconstituted animals, although the pattern of isotype production differed markedly between groups. The response in animals reconstituted with lymphocytes from the T. gondii-seronegative donor consisted primarily of IgM and subsequently of IgG (predominantly IgG1). In animals reconstituted with lymphocytes from the seropositive donor, no parasite-specific IgM could be demonstrated. The detectable response to STAg consisted entirely of human antibodies of the IgG isotype (IgG1), indicative of a memory-type response. These results mimicked exactly the antibody responses that would be expected had the lymphocyte donors been directly challenged with either the antigen or the live infectious agent, demonstrating that the immune system within these animals is functional and reproducible with regard to both the primary and secondary responses of the human donors. 相似文献
95.
Seung Yong Park Hisashi Arase Keisuke Wakizaka Nakami Hirayama Shigehiro Masaki So-Ichiro Sato Jeffrey V. Ravetch Takashi Saito 《European journal of immunology》1995,25(7):2107-2110
The function of the Fc receptors γ chain (FcRγ) for the expression of the T cell receptor (TCR) complex and for T cell development, especially for T cells localized in epithelia, was investigated by analyzing FcRγ-deficient mice. In wildtype mice, CD8αα+β?TCRαβ+ T cells of intestinal intraepithelial lymphocytes (i-IEL) utilized CD3ζ homodimers and ζ-FcRγ heterodimers, whereas CD8α α+β?TCRγδ+ i-IEL used ζ-FcRγ and FcRγ homodimers in the TCR complex. On the other hand, these T cells in FcRγ-deficient mice contained only ζ homodimers. The surface expression of the TCR complex was reduced in CD8αα+β?i-IEL and dendritic epidermal T cells (DETC) in these mice, whereas the development of these T cells was normal. The degree of reduction appeared to depend on the expression level of FcRγ. In contrast to these populations, TCRγδ+ intraepithelial T cells in reproductive organs (r-IEL) were dramatically decreased, suggesting that the development of r-IEL is FcRγ-dependent, probably due to the predominant usage of FcRγ homodimers in the TCR complex. These results indicate that the FcRγ chain contributes differently to the TCR expression and to the development of T cells localized in epithelia. 相似文献
96.
Joan C. Rener 《Methods in Cell Science》1985,9(3):187-189
Summary Hybridoma cell lines grown as ascites tumors in pristane primed mice will frequently yield milligram quantities of monoclonal antibody per milliliter of ascites fluid. Ascites production is an excellent method for the research scientist to generate high titer antibody with minimal effort. Through commercial production, gram to kilogram quantities can be achieved. 相似文献
97.
M. Jalkanen H. Larjava J. Heino T. Vihersaari J. Peltonen R. Penttinen 《Immunology letters》1982,4(5):259-261
In the present work we demonstrate that non-activated, cultured rat peritoneal macrophages deplete arginine from their culture medium and that the use of this medium in fibroblast cultures may lead to decreased synthesis of collagen by fibroblasts. 相似文献
98.
Spleen cells from a Lewis rat immunized with affinity-purified B10 anti-(T,G)-A-L antibody were fused with the non-secreting murine hybridoma SP2/0. Cell lines secreting monoclonal antibodies specific for mu- and kappa-chains, as well as an idiotope on anti-(T,G)-A-L antibodies, were isolated and characterized. The anti-mu and -kappa antibodies, are true anti-isotypes, reacting with sera from all strains of mice tested. The anti-idiotope antibodies recognize a determinant on antibodies binding a GT-containing epitope. The proportion of anti-GAT antibody bearing the idiotope varies markedly in different murine strains. A 1000-fold higher level of antibody from Igha mice than from Ighb and Ighe mice is required to give an equivalent inhibition of the idiotope-anti-idiotope reaction. Analysis of monoclonal antibodies expressing the idiotope indicates that the affinity of binding between idiotope and anti-idiotope can vary by as much as two orders of magnitude. Immunoadsorbants prepared with anti-idiotope antibody bind suppressor factor secreted by a GAT-specific T-cell hybridoma. 相似文献
99.
Calorie restriction (CR) extends the life span of various species through mechanisms that are as yet unclear. Recently, we have reported that mitochondrion-mediated apoptosis was enhanced in alphaMUPA transgenic mice that spontaneously eat less and live longer compared with their wild-type (WT) control mice. To understand the molecular mechanisms underlying the increased apoptosis, we compared alphaMUPA and WT mice for parameters associated with SOD2 (MnSOD), a mitochondrial antioxidant enzyme that converts superoxide radicals into H(2)O(2) and is also known to inhibit apoptosis. The SOD2-related parameters included the levels of SOD2 mRNA, immunoreactivity and enzymatic activity in the liver, lipid oxidation and aconitase activity in isolated liver mitochondria, and the sensitivity of the mice to paraquat, an agent that elicits oxidative stress. In addition, we compared the mice for the levels of SOD2 mRNA after treatment with bacterial lipopolysaccharides (LPS), and for the DNA binding activity of NFkappaB as a marker for the inflammatory state. We extended SOD2 determination to the colon, where we also examined the formation of pre-neoplastic aberrant crypt foci (ACF) following treatment with dimethylhydrazine (DMH), a colonic organotypic carcinogen. Overall, alphaMUPA mice showed reduced basal levels of SOD2 gene expression and activity concomitantly with reduced lipid oxidation, increased aconitase activity and enhanced paraquat sensitivity, while maintaining the capacity to produce high levels of SOD2 in response to the inflammatory stimulus. alphaMUPA mice also showed increased resistance to DMH-induced pre-neoplasia. Collectively, these data are consistent with a model, in which an optimal fine-tuning of SOD2 throughout a long-term regimen of reduced eating could contribute to longevity, at least in the alphaMUPA mice. 相似文献
100.
We examined the interaction of the albino locus with the maternal environment on the behavioral development of two coisogenic strains of mice. Subjects of the pigmented C57BL/6 strain (=B6+/+) and of the albino C57BL/6c2J strain (=B6c/c) were either fostered by a mother of their own strain or cross-fostered at birth to an F1 hybrid dam. They were compared for the amount and daily distribution of activity displayed during 48 h in a seminatural device at weaning and when 75 days old. Food hoarding in the nest and food consumption at the food-search place were also recorded in adult subjects. When animals were fostered by a mother of their own strain, albino mice were more active and less nocturnal than pigmented mice at both ages. They hoarded less food in the nest and ate more at the food-search place. Most of these differences disappeared when both strains were fostered by an F1 dam. The amount of activity displayed during 48 h increased between 21 and 75 days of age. This increase was affected by cross-fostering to an F1 dam in B6c/c mice only. The developmental pattern of daily distribution of activity was changed by F1 dams in B6+/+ mice only. Whereas these influences of F1 dams produced subjects resembling the mother's phenotypic score, maternal effects on hoarding behavior in B6c/c mice produced subjects which did not resemble their foster mother. The results are discussed in terms of different possible ways of hereditary transmission of behavior and some methodological consequences are emphasized. 相似文献