全文获取类型
收费全文 | 5597篇 |
免费 | 497篇 |
国内免费 | 1篇 |
出版年
2023年 | 23篇 |
2022年 | 61篇 |
2021年 | 155篇 |
2020年 | 73篇 |
2019年 | 113篇 |
2018年 | 132篇 |
2017年 | 108篇 |
2016年 | 186篇 |
2015年 | 301篇 |
2014年 | 347篇 |
2013年 | 399篇 |
2012年 | 496篇 |
2011年 | 467篇 |
2010年 | 267篇 |
2009年 | 261篇 |
2008年 | 355篇 |
2007年 | 336篇 |
2006年 | 303篇 |
2005年 | 268篇 |
2004年 | 239篇 |
2003年 | 197篇 |
2002年 | 212篇 |
2001年 | 61篇 |
2000年 | 36篇 |
1999年 | 53篇 |
1998年 | 60篇 |
1997年 | 43篇 |
1996年 | 33篇 |
1995年 | 38篇 |
1994年 | 27篇 |
1993年 | 29篇 |
1992年 | 30篇 |
1991年 | 35篇 |
1990年 | 32篇 |
1989年 | 20篇 |
1988年 | 25篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1974年 | 10篇 |
1973年 | 17篇 |
排序方式: 共有6095条查询结果,搜索用时 187 毫秒
991.
Rebecca M Williams Andrea Flesken-Nikitin Lora Hedrick Ellenson Denise C Connolly Thomas C Hamilton Alexander Yu Nikitin Warren R Zipfel 《Translational oncology》2010,3(3):181-194
Ovarian cancer remains the most frequently lethal of the gynecologic cancers owing to the late detection of this disease. Here, by using human specimens and three mouse models of ovarian cancer, we tested the feasibility of nonlinear imaging approaches, the multiphoton microscopy (MPM) and second harmonic generation (SHG) to serve as complementary tools for ovarian cancer diagnosis. We demonstrate that MPM/SHG of intrinsic tissue emissions allows visualization of unfixed, unsectioned, and unstained tissues at a resolution comparable to that of routinely processed histologic sections. In addition to permitting discrimination between normal and neoplastic tissues according to pathological criteria, the method facilitates morphometric assessment of specimens and detection of very early cellular changes in the ovarian surface epithelium. A red shift in cellular intrinsic fluorescence and collagen structural alterations have been identified as additional cancer-associated changes that are indiscernible by conventional pathologic techniques. Importantly, the feasibility of in vivo laparoscopic MPM/SHG is demonstrated by using a “stick” objective lens. Intravital detection of neoplastic lesions has been further facilitated by low-magnification identification of an indicator for cathepsin activity followed by MPM laparoscopic imaging. Taken together, these results demonstrate that MPM may be translatable to clinical settings as an endoscopic approach suitable for high-resolution optical biopsies as well as a pathology tool for rapid initial assessment of ovarian cancer samples. 相似文献
992.
Britta Denise Hardesty Christopher W. Dick James L. Hamrick Bernd Degen Stephen P. Hubbell Eldredge Bermingham 《Tropical plant biology》2010,3(1):28-39
This study aimed to assess the population genetic structure of a widespread Neotropical tree species, Simarouba amara, at local, regional and continental spatial scales. We used five microsatellite loci to examine genetic variation in 14 natural populations (N?=?478 individuals) of this vertebrate-dispersed rain forest tree species in Panama, Ecuador, and French Guiana. Estimates of genetic differentiation (F st and R st) were significant among all but one population pair and global differentiation was moderate (F st?=?0.25, R st?=?0.33) with 94% of genetic variation ascribed to differences among three main geographic regions (Central America, Western Ecuador, Amazon basin). There was no evidence of isolation by distance within regions. Allele-size mutations contributed significantly (R ST > F ST) to the divergences between cis- and trans-Andean populations, highlighting the role of the northern Andean cordilleras as an important geographic barrier for this species. 相似文献
993.
Lorena Da Rós Gonçalves Márcia Regina Soares Fábio C.S. Nogueira Carlos Garcia Danielle Resende Camisasca Gilberto Domont Alfredo C.R. Feitosa Denise de Abreu Pereira Russolina B. Zingali Gilda Alves 《Journal of Proteomics》2010,73(7):1334-1341
Chronic periodontal disease is a chronic inflammatory process affecting tooth supporting tissues in the presence of pathogenic bacterial biofilm. There is some evidence for changes in the protein composition of whole saliva from chronic periodontitis patients, but there have been no studies using a proteomic approach. Hence, the aim of this study was to compare the protein profiles of unstimulated whole saliva from patients with periodontitis and healthy subjects by two complementary approaches (2D-gel electrophoresis and liquid chromatography). Protein spots of interest were analyzed by MALDI-TOF-TOF, and the data was complemented by an ESI-Q-TOF experiment. The analyses revealed that subjects with periodontal disease have increased amounts of blood proteins (serum albumin and hemoglobin) and immunoglobulin, and they have a lower abundance of cystatin compared to the control group. A higher number of protein spots were observed in the periodontitis group, of which most were identified as alpha-amylase. This higher number of alpha-amylase variants seems to be caused by hydrolysis by cysteine proteases under such inflammatory conditions. This approach gives novel insights into alterations of salivary protein in presence of periodontal inflammation and may contribute to the improvement of periodontal diagnosis. 相似文献
994.
995.
C. Scott Mahan Maria Walusimbi Denise F. Johnson Christina Lancioni Edwin Charlebois Joyce Baseke Keith A. Chervenak Roy D. Mugerwa Diane V. Havlir Harriet Mayanja-Kizza Christopher C. Whalen W. Henry Boom for the Uganda-Case Western Research Collaboration 《PloS one》2010,5(2)
Background
Both HIV and TB cause a state of heightened immune activation. Immune activation in HIV is associated with progression to AIDS. Prior studies, focusing on persons with advanced HIV, have shown no decline in markers of cellular activation in response to TB therapy alone.Methodology
This prospective cohort study, composed of participants within a larger phase 3 open-label randomized controlled clinical trial, measured the impact of TB treatment on immune activation in persons with non-advanced HIV infection (CD4>350 cells/mm3) and pulmonary TB. HIV load, CD4 count, and markers of immune activation (CD38 and HLA-DR on CD4 and CD8 T cells) were measured prior to starting, during, and for 6 months after completion of standard 6 month anti-tuberculosis (TB) therapy in 38 HIV infected Ugandans with smear and culture confirmed pulmonary TB.Results
Expression of CD38, and co-expression of CD38 and HLA-DR, on CD8 cells declined significantly within 3 months of starting standard TB therapy in the absence of anti-retroviral therapy, and remained suppressed for 6 months after completion of therapy. In contrast, HIV load and CD4 count remained unchanged throughout the study period.Conclusion
TB therapy leads to measurable decreases in immune activation in persons with HIV/TB co-infection and CD4 counts >350 cells/mm3. 相似文献996.
Tamara D. Clark Denise Njama-Meya Bridget Nzarubara Catherine Maiteki-Sebuguzi Bryan Greenhouse Sarah G. Staedke Moses R. Kamya Grant Dorsey Philip J. Rosenthal 《PloS one》2010,5(7)
Background
Combination therapies are now recommended to treat uncomplicated malaria. We used a longitudinal design to assess the incidence of malaria and compare the efficacies of 3 combination regimens in Kampala, Uganda.Methodology/Principal Findings
Children aged 1–10 years were enrolled from randomly selected households in 2004–05 and 2007, and were followed at least monthly through 2008. Insecticide-treated bednets (ITNs) were provided in 2006. Children were randomized upon their first episode, and then treated for all episodes of uncomplicated malaria with amodiaquine/sulfadoxine-pyrimethamine (AQ/SP), artesunate/amodiaquine (AS/AQ), or artemether/lumefantrine (AL). Risks of parasitological failure were determined for each episode of uncomplicated malaria and clinical parameters were followed. A total of 690 children experienced 1464 episodes of malaria. 96% of these episodes were uncomplicated malaria and treated with study drugs; 94% were due to Plasmodium falciparum. The rank order of treatment efficacy was AL > AS/AQ > AQ/SP. Failure rates increased over time for AQ/SP, but not the artemisinin-based regimens. Over the 4-year course of the study the prevalence of asymptomatic parasitemia decreased from 11.8% to 1.4%, the incidence of malaria decreased from 1.55 to 0.32 per person year, and the prevalence of anemia (hemoglobin <10 gm/dL) decreased from 5.9% to 1.0%. No episodes of severe malaria (based on WHO criteria) and no deaths were seen.Conclusions/Significance
With ready access to combination therapies and distribution of ITNs, responses were excellent for artemisinin-containing regimens, severe malaria was not seen, and the incidence of malaria and prevalence of parasitemia and anemia decreased steadily over time.Trial Registration
isrctn.org ISRCTN37517549 相似文献997.
Nelly Buron Mathieu Porceddu Magali Brabant Diana Desgué Cindy Racoeur Myriam Lassalle Christine Péchoux Pierre Rustin Etienne Jacotot Annie Borgne-Sanchez 《PloS one》2010,5(3)
Current limitations of chemotherapy include toxicity on healthy tissues and multidrug resistance of malignant cells. A number of recent anti-cancer strategies aim at targeting the mitochondrial apoptotic machinery to induce tumor cell death. In this study, we set up protocols to purify functional mitochondria from various human cell lines to analyze the effect of peptidic and xenobiotic compounds described to harbour either Bcl-2 inhibition properties or toxic effects related to mitochondria. Mitochondrial inner and outer membrane permeabilization were systematically investigated in cancer cell mitochondria versus non-cancerous mitochondria. The truncated (t-) Bid protein, synthetic BH3 peptides from Bim and Bak, and the small molecule ABT-737 induced a tumor-specific and OMP-restricted mitochondrio-toxicity, while compounds like HA-14.1, YC-137, Chelerythrine, Gossypol, TW-37 or EM20-25 did not. We found that ABT-737 can induce the Bax-dependent release of apoptotic proteins (cytochrome c, Smac/Diablo and Omi/HtrA2 but not AIF) from various but not all cancer cell mitochondria. Furthermore, ABT-737 addition to isolated cancer cell mitochondria induced oligomerization of Bax and/or Bak monomers already inserted in the mitochondrial membrane. Finally immunoprecipatations indicated that ABT-737 induces Bax, Bak and Bim desequestration from Bcl-2 and Bcl-xL but not from Mcl-1L. This study investigates for the first time the mechanism of action of ABT-737 as a single agent on isolated cancer cell mitochondria. Hence, this method based on MOMP (mitochondrial outer membrane permeabilization) is an interesting screening tool, tailored for identifying Bcl-2 antagonists with selective toxicity profile against cancer cell mitochondria but devoid of toxicity against healthy mitochondria. 相似文献
998.
Background
Leber''s hereditary optic neuropathy (LHON) is a maternally inherited disorder with point mutations in mitochondrial DNA which result in loss of vision in young adults. The majority of mutations reported to date are within the genes encoding the subunits of the mitochondrial NADH-quinone oxidoreductase, complex I. Establishment of animal models of LHON should help elucidate mechanism of the disease and could be utilized for possible development of therapeutic strategies.Methodology/Principal Findings
We established a rat model which involves injection of rotenone-loaded microspheres into the optic layer of the rat superior colliculus. The animals exhibited the most common features of LHON. Visual loss was observed within 2 weeks of rotenone administration with no apparent effect on retinal ganglion cells. Death of retinal ganglion cells occurred at a later stage. Using our rat model, we investigated the effect of the yeast alternative NADH dehydrogenase, Ndi1. We were able to achieve efficient expression of the Ndi1 protein in the mitochondria of all regions of retinal ganglion cells and axons by delivering the NDI1 gene into the optical layer of the superior colliculus. Remarkably, even after the vision of the rats was severely impaired, treatment of the animals with the NDI1 gene led to a complete restoration of the vision to the normal level. Control groups that received either empty vector or the GFP gene had no effects.Conclusions/Significance
The present study reports successful manifestation of LHON-like symptoms in rats and demonstrates the potential of the NDI1 gene therapy on mitochondrial optic neuropathies. Our results indicate a window of opportunity for the gene therapy to be applied successfully after the onset of the disease symptoms. 相似文献999.
Shan Deng Xiaojun Yang Heini Lassus Shun Liang Sippy Kaur Qunrui Ye Chunsheng Li Li-Ping Wang Katherine F. Roby Sandra Orsulic Denise C. Connolly Youcheng Zhang Kathleen Montone Ralf Bützow George Coukos Lin Zhang 《PloS one》2010,5(4)
Aldehyde dehydrogenase isoform 1 (ALDH1) has been proved useful for the identification of cancer stem cells. However, our knowledge of the expression and activity of ALDH1 in common epithelial cancers and their corresponding normal tissues is still largely absent. Therefore, we characterized ALDH1 expression in 24 types of normal tissues and a large collection of epithelial tumor specimens (six cancer types, n = 792) by immunohistochemical staining. Using the ALDEFUOR assay, ALDH1 activity was also examined in 16 primary tumor specimens and 43 established epithelial cancer cell lines. In addition, an ovarian cancer transgenic mouse model and 7 murine ovarian cancer cell lines were analyzed. We found that the expression levels and patterns of ALDH1 in epithelial cancers are remarkably distinct, and they correlate with their corresponding normal tissues. ALDH1 protein expression levels are positively correlated with ALDH1 enzymatic activity measured by ALDEFLUOR assay. Long-term in vitro culture doesn''t significantly affect ALDH1 activity in epithelial tumor cells. Consistent with research on other cancers, we found that high ALDH1 expression is significantly associated with poor clinical outcomes in serous ovarian cancer patients (n = 439, p = 0.0036). Finally, ALDHbr tumor cells exhibit cancer stem cell properties and are resistant to chemotherapy. As a novel cancer stem cell marker, ALDH1 can be used for tumors whose corresponding normal tissues express ALDH1 in relatively restricted or limited levels such as breast, lung, ovarian or colon cancer. 相似文献
1000.