全文获取类型
收费全文 | 11455篇 |
免费 | 839篇 |
国内免费 | 30篇 |
专业分类
耳鼻咽喉 | 81篇 |
儿科学 | 360篇 |
妇产科学 | 218篇 |
基础医学 | 1899篇 |
口腔科学 | 261篇 |
临床医学 | 1092篇 |
内科学 | 2042篇 |
皮肤病学 | 332篇 |
神经病学 | 1557篇 |
特种医学 | 448篇 |
外科学 | 979篇 |
综合类 | 63篇 |
一般理论 | 4篇 |
预防医学 | 841篇 |
眼科学 | 349篇 |
药学 | 761篇 |
中国医学 | 16篇 |
肿瘤学 | 1021篇 |
出版年
2024年 | 19篇 |
2023年 | 106篇 |
2022年 | 172篇 |
2021年 | 285篇 |
2020年 | 222篇 |
2019年 | 256篇 |
2018年 | 305篇 |
2017年 | 273篇 |
2016年 | 376篇 |
2015年 | 402篇 |
2014年 | 492篇 |
2013年 | 648篇 |
2012年 | 913篇 |
2011年 | 924篇 |
2010年 | 526篇 |
2009年 | 519篇 |
2008年 | 830篇 |
2007年 | 797篇 |
2006年 | 748篇 |
2005年 | 720篇 |
2004年 | 618篇 |
2003年 | 574篇 |
2002年 | 535篇 |
2001年 | 96篇 |
2000年 | 76篇 |
1999年 | 92篇 |
1998年 | 111篇 |
1997年 | 110篇 |
1996年 | 89篇 |
1995年 | 70篇 |
1994年 | 47篇 |
1993年 | 44篇 |
1992年 | 37篇 |
1991年 | 32篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 19篇 |
1987年 | 10篇 |
1986年 | 25篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 16篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Construction and characterization of Listeria monocytogenes mutants with in-frame deletions in the response regulator genes identified in the genome sequence
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Two-component systems are widely distributed in prokaryotes where they control gene expression in response to diverse stimuli. To study the role of the sixteen putative two-component systems of Listeria monocytogenes systematically, in frame deletions were introduced into 15 out of the 16 response regulator genes and the resulting mutants were characterized. With one exception the deletion of the individual response regulator genes has only minor effects on in vitro and in vivo growth of the bacteria. The mutant carrying a deletion in the ortholog of the Bacillus subtilis response regulator gene degU showed a clearly reduced virulence in mice, indicating that DegU is involved in the regulation of virulence-associated genes. 相似文献
52.
Schmidt KL Larsen E Bangsbøll S Meinertz H Carlsen E Andersen AN 《Human reproduction (Oxford, England)》2004,19(12):2806-2810
BACKGROUND: Many male cancer survivors experience fertility problems due to antineoplastic treatment. We report the fertility outcome in 67 couples referred to assisted reproduction treatment (ART) because of male factor infertility due to cancer. METHODS: This was a retrospective study assessing the following parameters: diagnosis, cancer treatment, type of fertility treatment and type of sperm used, number of pregnancies and pregnancy outcome. RESULTS: Testicular cancer and lymphomas were the most prevalent diagnoses. Adjuvant treatment with chemo- and/or radiation therapy had been given to 90% of the men. Semen was cryopreserved in 82% of the men prior to treatment. Following antineoplastic treatment, 43% of the men had motile spermatozoa in the ejaculate, but 57% were azoospermic. A total of 151 ART cycles were performed [55 intra-uterine insemination (IUI), 82 ICSI and 14 ICSI-frozen embryo replacement (FER)]. The clinical pregnancy rate per cycle was 14.8% after IUI, 38.6% after ICSI and 25% after ICSI-FER. The corresponding delivery rates were 11.1, 30.5 and 21%. Cryopreserved semen was used in 58% of the pregnancies. The delivery rate per cycle was similar after use of fresh or cryopreserved spermatozoa. CONCLUSIONS: Male cancer survivors have a good chance of fathering a child by using either fresh ejaculated sperm or cryopreserved sperm. 相似文献
53.
54.
Liu X Beaty TH Deindl P Huang SK Lau S Sommerfeld C Fallin MD Kao WH Wahn U Nickel R 《The Journal of allergy and clinical immunology》2003,112(2):382-388
BACKGROUND: Increased total serum IgE levels are a common characteristic of atopic disorders. Six potentially functional variants, including C-590T in the IL4 gene, C-1055T and Arg130Gln in the IL13 gene, and Ile50Val, Ser478Pro, and Gln551Arg in the IL4RA gene, have been evaluated for their involvement in the control of total serum IgE levels and related atopic disorders, but the results of these studies have been inconsistent. OBJECTIVE: We examined whether these 6 variants had genotypic effects on total serum IgE levels in 823 unrelated German children from a large infant cohort, the German Multicenter Atopy Study. METHODS: Marginal effect models were used for the analyses of the repeated IgE measurements. Weighted linear regression and family-based tests of association were performed to minimize the possibility of spurious effects caused by selection bias or confounding on the basis of ethnic background. RESULTS: There are significant associations between increased total serum IgE levels and 2 variants in the IL13 gene (P <.005 and.0002 for Arg130Gln and C-1055T, respectively). These genetic effects are unlikely to be due to solely linkage disequilibrium between 2 polymorphisms, population stratification, or nonrepresentative samples. In addition, exposure to maternal smoking appears to modify the above effects on total serum IgE levels. However, no statistical association was observed between this quantitative phenotype and the other 4 variants examined. CONCLUSION: These findings suggest that variants C-1055T and Arg130Gln of the IL13 gene might play an important role on total serum IgE production in this study population. 相似文献
55.
Susanne Krmer Clio Mamalaki Ivan Horak Anneliese Schimpl Dimitris Kioussis Thomas Hünig 《European journal of immunology》1994,24(10):2317-2322
The requirement for interleukin-2 (IL-2) in repertoire selection and peripheral activation of CD8 T cells was tested in mice rendered IL-2 deficient by gene targeting and expressing a transgenic T cell receptor (TcR) (F5) specific for influenza nucleoprotein (NP) 366-374 + H-2Db. Positive selection of the transgenic F5 TcR into the CD8 compartment proceeded normally. Both in vivo and in vitro, the antigenic peptide induced depletion of immature thymocytes and proliferation of mature CD8 T cells regardless of the presence of an intact IL-2 gene. In contrast, cytotoxic T lymphocyte (CTL) activity was only generated by T cells from IL-2+ F5 transgenic mice. Exogenous IL-2 was able to fully restore the CTL response of IL-2?/? responder cells in vitro. Thus, both in vivo and in vitro, clonal expansion of CD8 T cells can proceed in the absence of IL-2, whereas in peptide-immunized F5 transgenic mice, induction of cytotoxic effector function is IL-2 dependent. 相似文献
56.
Brix S Kjaer TM Barkholt V Frøkiaer H 《International archives of allergy and immunology》2004,135(3):216-220
BACKGROUND: Microbial components in the environment are potent activators of the immune system with capacity to shift the active immune response towards priming of Th1 and/or Th2 cells. Lipopolysaccharide (LPS), a cell-wall component of Gram-negative bacteria, is extensively present in food products like cow's milk. It is not well established, however, how this presence of LPS affects oral tolerance induction. METHODS: We studied the effect of LPS contamination in a commercial preparation of the cow milk protein beta-lactoglobulin (beta-LG) on antigen-specific immune responses. IgG1/IgG2a production upon intraperitoneal immunization without adjuvant was measured, and oral tolerance induction against beta-LG after administration of either an aqueous solution or water-in-oil (w/o) emulsion of beta-LG was evaluated. RESULTS: LPS contamination of beta-LG provoked a beta-LG-specific IgG2a response, as well as an enhanced beta-LG-specific IgG1 response upon intraperitoneal immunization. Oral tolerance induction to beta-LG was induced by aqueous solutions of beta-LG with and without LPS administration. Conversely, oral administration of w/o-emulsified beta-LG prevented oral tolerance to beta-LG only when the beta-LG was contaminated with LPS. CONCLUSIONS: LPS contamination of an aqueous protein solution does not affect oral tolerance induction, whereas LPS present in emulsion prevents oral tolerance induction towards the food protein. 相似文献
57.
Spike timing reliability of neuronal responses depends on the frequency content of the input. We investigate how intrinsic properties of cortical neurons affect spike timing reliability in response to rhythmic inputs of suprathreshold mean. Analyzing reliability of conductance-based cortical model neurons on the basis of a correlation measure, we show two aspects of how ionic conductances influence spike timing reliability. First, they set the preferred frequency for spike timing reliability, which in accordance with the resonance effect of spike timing reliability is well approximated by the firing rate of a neuron in response to the DC component in the input. We demonstrate that a slow potassium current can modulate the spike timing frequency preference over a broad range of frequencies. This result is confirmed experimentally by dynamic-clamp recordings from rat prefrontal cortical neurons in vitro. Second, we provide evidence that ionic conductances also influence spike timing beyond changes in preferred frequency. Cells with the same DC firing rate exhibit more reliable spike timing at the preferred frequency and its harmonics if the slow potassium current is larger and its kinetics are faster, whereas a larger persistent sodium current impairs reliability. We predict that potassium channels are an efficient target for neuromodulators that can tune spike timing reliability to a given rhythmic input. 相似文献
58.
Döpper S Wilflingseder D Prodinger WM Stiegler G Speth C Dierich MP Stoiber H 《European journal of immunology》2003,33(8):2098-2107
Resting CD4(+) T cells in the lymphoid tissue (LT) are essential producers of virions at the beginning of HIV infection in vivo. We previously developed a model that allowed in vitro infection of non-prestimulated T lymphocytes in the presence of autologous B lymphocytes and complement. In this study, we try to clarify the mechanism(s) responsible for virus transmission in unstimulated autologous B cell/T cell co-cultures. Ex vivo analyses of patient plasma samples revealed that HIV was opsonized. Flow cytometry showed that opsonized virus preferentially bound to complement receptor (CR)-2 on B lymphocytes in primary B cell/T cell co-cultures. As indicated by cytokine measurements and transwell experiments, soluble factors seemed to play a minor role in enabling infection. Rather, direct interaction between B and T lymphocytes and direct binding of opsonized virus to CR2 on B cells turned out to be essential for productive infection. Antibodies blocking cell-cell adhesion inhibited p24 antigen production. An anti-CR2 antibody blocking C3d-CR2 binding also significantly reduced viral replication. Since the infection of unstimulated T cells by opsonized primary HIV isolates in the presence of B cells was highly efficient independent of the tropism of the virus, this mechanism may be critical in the pathogenesis of HIV. 相似文献
59.
Lymphocyte transformation and production of a human mononuclear leucocyte chemotactic factor in patients with Hodgkin''s disease
下载免费PDF全文
![点击此处可从《Clinical and experimental immunology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
H. Rühl W. Vogt Gudrun Bochert Susanne Schmidt H. Schaoua Renate Moelle 《Clinical and experimental immunology》1974,17(3):407-415
Human peripheral lymphocytes stimulated in vitro with phytohaemagglutinin (PHA) produce a factor with chemotactic activity for homologous monocytes. The production of this factor and lymphocyte transformation was investigated in patients with Hodgkin's disease. It has been found that the PHA response as measured by incorporation of [3H]thymidine was markedly depressed in patients when compared to the response of normal lymphocytes. In contrast, the production of the chemotactic factor was not significantly depressed in patients with Hodgkin's disease. 相似文献
60.
Interaction of Angiotensin with Disseminated Intravascular Coagulation: A Possible Mechanism in the Genesis of Acute Renal Failure
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)
Alan N. Whitaker Ian Bunce Peter Nicoll Susanne V. Dowling 《The American journal of pathology》1973,72(1):1-12
Because of the importance of the renin-angiotensin system in renal homeostatic mechanisms, the effect of angiotensin administration upon disseminated intravascular coagulation has been studied in rabbits. An infusion of angiotensin II (0.1 μg/kg/min for 2 hours) produced neither histologic abnormalities in the kidneys nor an elevation of creatinine. After an infusion of thrombin (2.0 units/kg/min for 2 hours) only 3 of 10 rabbits, when sacrified 24 hours later, showed histologic lesions comprised of occasional fibrin thrombi and foci of tubular necrosis. Creatinine levels did not rise. In contrast, the combination of angiotensin and thrombin resulted in renal lesions in 12 of 14 animals. Four had frank cortical necrosis, while combinations of tubular necrosis, glomerular thrombosis and segmental glomerular infarction occurred in the others, together with elevated creatinine levels. Blockade of α-adrenoreceptors with phenoxybenzamine in 12 animals did not prevent either these histologic changes or creatinine elevation, showing that the effect of angiotensin was independent of α-adrenoreceptor stimulation. The synergistic interaction between angiotensin and disseminated intravascular coagulation was not explained by differences in the consumption of plasma fibrinogen but apparently was due to localization of fibrin thrombi within glomerular capillaries by the vasomotor actions of angiotensin, as has previously been shown to occur with α-adrenoreceptor simulation. Such a mechanism might contribute to renal glomerular deposition of fibrin in acute ischemic renal failure. 相似文献