全文获取类型
收费全文 | 8991篇 |
免费 | 637篇 |
国内免费 | 467篇 |
专业分类
10095篇 |
出版年
2024年 | 10篇 |
2023年 | 81篇 |
2022年 | 190篇 |
2021年 | 324篇 |
2020年 | 231篇 |
2019年 | 265篇 |
2018年 | 282篇 |
2017年 | 231篇 |
2016年 | 320篇 |
2015年 | 461篇 |
2014年 | 578篇 |
2013年 | 638篇 |
2012年 | 739篇 |
2011年 | 703篇 |
2010年 | 413篇 |
2009年 | 371篇 |
2008年 | 424篇 |
2007年 | 416篇 |
2006年 | 367篇 |
2005年 | 359篇 |
2004年 | 292篇 |
2003年 | 299篇 |
2002年 | 241篇 |
2001年 | 195篇 |
2000年 | 193篇 |
1999年 | 162篇 |
1998年 | 108篇 |
1997年 | 102篇 |
1996年 | 104篇 |
1995年 | 101篇 |
1994年 | 78篇 |
1993年 | 78篇 |
1992年 | 127篇 |
1991年 | 101篇 |
1990年 | 72篇 |
1989年 | 72篇 |
1988年 | 66篇 |
1987年 | 49篇 |
1986年 | 41篇 |
1985年 | 53篇 |
1984年 | 33篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1971年 | 7篇 |
1970年 | 7篇 |
1966年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
921.
Background
Aortocaval fistula (AV) in rat is a unique model of volume-overload congestive heart failure and cardiac hypertrophy. Living donor kidney transplantation is regarded as beneficial to allograft recipients and not particularly detrimental to the donors. Impact of AV on animals with mild renal dysfunction is not fully understood. In this study, we explored the effects of AV in unilateral nephrectomized (UNX) rats.Methods
Adult male Sprague-Dawley (SD) rats were divided into Sham (n = 10), UNX (right kidney remove, n = 10), AV (AV established between the levels of renal arteries and iliac bifurcation, n = 18) and UNX+AV (AV at one week after UNX, n = 22), respectively. Renal outcome was measured by glomerular filtration rate, effective renal plasma flow, fractional excretion of sodium, albuminuria, plasma creatinine, and cystatin C. Focal glomerulosclerosis (FGS) incidence was evaluated by renal histology. Cardiac function was measured by echocardiography and hemodynamic measurements.Results
UNX alone induced compensatory left kidney enlargement, increased plasma creatinine and cystatin C levels, and slightly reduced glomerular filtration rate and increased FGS. AV induced significant cardiac enlargement and hypertrophy and reduced cardiac function and increased FGS, these changes were aggravated in UNX+AV rats.Conclusions
Although UNX only induces minor renal dysfunction, additional chronic volume overload placement during the adaptation phase of the remaining kidney is associated with aggravated cardiac dysfunction and remodeling in UNX rats, suggesting special medical care is required for UNX or congenital monokidney subjects in case of chronic volume overload as in the case of pregnancy and hyperthyroidism to prevent further adverse cardiorenal events in these individuals. 相似文献922.
Marker-assisted selection of YY supermales from a genetically improved farmed tilapia-derived strain 总被引:1,自引:0,他引:1
正DEAR EDITOR,Genetically improved farmed tilapia (GIFT) and GIFT-derived strains account for the majority of farmed tilapia worldwide. As male tilapias grow much faster than females, they are often considered more desirable in the aquacultural industry. Sex reversal of females to males using the male sex hormone17-α-methyltestosterone (MT) is generally used to induce phenotypic males during large-scale production of all male fingerlings. However, the widespread use of large quantities 相似文献
923.
Tang Gang-liang Li Xiang-yi Lin Li-sha Gu Zhu-yu Zeng Fan-jiang 《Journal of Plant Growth Regulation》2019,38(3):980-991
Journal of Plant Growth Regulation - Constituting the last stage of leaf development, leaf senescence is a complicated process that involves many senescence-associated genes, and numerous factors... 相似文献
924.
Guo T Gu H Hobbs DW Busler DE Rokosz LL 《Bioorganic & medicinal chemistry letters》2007,17(6):1718-1721
Melanin concentrating hormone (MCH) plays an important role in the regulation of food intake and energy balance in mammals. MCH-1 receptor (MCH1R) deficient mice are lean and resistant to diet-induced obesity. As such, MCH1R antagonists are believed to have potential as possible treatments for obesity. The discovery of a novel class of tetralin ureas as potent MCH1R antagonists is described herein. 相似文献
925.
Jolly C Thoison O Martin MT Dumontet V Gilbert A Pfeiffer B Léonce S Sévenet T Guéritte F Litaudon M 《Phytochemistry》2008,69(2):533-540
In the course of an automated screening for small molecules presenting cytotoxic activity, eight new cyclophanes named kermadecins A-H (1-8), have been isolated from the bark of a New Caledonian plant, Kermadecia elliptica, Proteaceae. A LC/APCI-MS study performed on kermadecins A, B and C, provided a reliable method for the detection of other analogues existing in small quantities in the extract. This led to the isolation of five other members of this chemical series. The structures were elucidated by extensive mono- and bi-dimensional spectroscopy and mass spectrometry. The cytotoxic activity of four of them was evaluated on various cell lines. 相似文献
926.
This is the first report of Harpellales (Zygomycota) from Mexico, including herein only the endosymbiotic species of gut fungi in the digestive tracts or shed exuviae of Plecopteran and Ephemeropteran nymphs. Four new species are described: Allantomyces zopilotei, Bojamyces olmecensis, Gauthier-omyces viviparus and Graminella ophiuroidea. Among previously known Harpellales, Lancisporomyces nemouridarum and Zygopolaris ephemeridarum are southern range extremes and new records for Mexico. All species are illustrated and discussed relating to biogeographic implications of the new reports from Mexico, as well as the particular environmental circumstances of the Harpellales in the tropics. 相似文献
927.
骨质疏松等中老年的常见病和多发病也呈年轻化发展,如何进行有效的骨状况诊断,拥有一台可以信赖的、可以方便地应用的骨测量仪器显得更为重要。超声波骨测量技术是使用范围比较广泛的一种,本文对超声波测量法的最新发展进行了阐述。 相似文献
928.
929.
930.
Local delivery of IL-12 and GM-CSF to advanced primary tumors results in T- and NK-cell-dependent cure of disseminated disease
in a murine spontaneous lung metastasis model. Post-therapy functional dynamics of cytotoxic T- and NK-cells were analyzed
in primary and metastatic tumors to determine the specific roles of each subset in tumor eradication. Time-dependent depletion
of CD8+ T and NK-cells demonstrated that CD8+ T-cells were critical to eradication of metastatic tumors within 3 days of treatment,
but not later. In contrast, NK-cells were found to be essential to tumor regression for at least 10 days after cytokine delivery.
Analysis of tumor-infiltrating lymphocyte populations in post-therapy primary tumors demonstrated that treatment resulted
in the activation of tumor-associated CD8+ T-cells within 24 h as determined by IFNγ and perforin production. T-cell activity
peaked between days 1 and 3 and subsided rapidly thereafter. Activation was not accompanied with an increase in cell numbers
suggesting that treatment mobilized pre-existing T-effector/memory cells without inducing proliferation. In contrast, therapy
resulted in a ≥3-fold enhancement of both the quantity and the cytotoxic activity of NK-cells in primary and metastatic tumors
on day 3 post-therapy. NK-cell activity was also transient and subsided to pre-therapy levels by day 5. Depletion of CD4+
and CD8+ T-cells prior to treatment completely abrogated NK-cell infiltration into primary and metastatic tumors demonstrating
the strict dependence of NK-cell recruitment on pre-existing T-effector/memory cells. Treatment failed to induce significant
NK-cell infiltration in IFNγ-knockout mice establishing the central role of IFNγ in NK-cell chemotaxis to tumors. These data
show that transient activation of tumor-associated T-effector/memory and NK-cells, but not long-term CD8+ T-cell responses,
are critical to suppression of metastatic disease in this model; and reveal a novel role for pre-existing adaptive T-cell
immunity in the recruitment of innate effectors to tumors.
This work was supported by NIH/NCI grant R01-CA100656-01A1 to N.K.E. 相似文献