首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10467篇
  免费   831篇
  国内免费   707篇
  12005篇
  2024年   24篇
  2023年   152篇
  2022年   357篇
  2021年   577篇
  2020年   377篇
  2019年   440篇
  2018年   482篇
  2017年   369篇
  2016年   440篇
  2015年   638篇
  2014年   705篇
  2013年   802篇
  2012年   984篇
  2011年   866篇
  2010年   486篇
  2009年   426篇
  2008年   572篇
  2007年   476篇
  2006年   416篇
  2005年   352篇
  2004年   269篇
  2003年   250篇
  2002年   184篇
  2001年   172篇
  2000年   146篇
  1999年   152篇
  1998年   91篇
  1997年   94篇
  1996年   93篇
  1995年   77篇
  1994年   85篇
  1993年   64篇
  1992年   58篇
  1991年   74篇
  1990年   59篇
  1989年   42篇
  1988年   32篇
  1987年   17篇
  1986年   22篇
  1985年   18篇
  1984年   17篇
  1983年   20篇
  1982年   8篇
  1980年   3篇
  1978年   2篇
  1975年   2篇
  1973年   2篇
  1971年   3篇
  1968年   2篇
  1966年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
将编码人 94个氨基酸的前列腺分泌蛋白 ( PSP94) c DNA与酵母整合载体 p PICZαA重组 ,构建的重组质粒线性化后转染酵母细胞 GS1 1 5,获得了 PSP94在酵母细胞中遗传性稳定表达酵母工程细胞 .诱导后的培养物中 ,rh PSP94表达量约为 0 .9mg/L,分子量约 1 6.5k D.培养上清经离子交换层析纯化后 ,目的蛋白的纯度为 92 % .体外在人前列腺癌细胞上活性分析表明 ,rh PSP94以1 0 0μg/L ,对该细胞的抑制率 2 0 .4% ;单纯新型 TNF,以 1 0 3 U/ml,抑制率 2 9.8% ;rh PSP94和新型 TNF以上述同样剂量联合应用 ,抑制率为 86.3% .提示 PSP94在体外对抗前列腺癌细胞有杀伤作用 ,但不明显 ;PSP94与新型 TNF联合应用 ,可使抑制率明显提高 ,可能 PSP94与新型 TNF有协同抗前列腺癌的作用 .  相似文献   
992.
993.
994.
Rice straw burning has accompanied paddy management for millennia, introducing black carbon (BC) into soil as the residue of incomplete combustion. This study examined the contribution of BC to soil organic matter and the rate at which it accumulates in paddy soils as a result of prolonged paddy management. Soil depth profiles were sampled along a chronosequence of 0–2000 years of rice–wheat rotation systems and adjacent non‐paddy systems (50–700 years) in the Bay of Hangzhou (Zhejiang province, China). The soil BC content and its degree of condensation were assessed using benzene‐polycarboxylic acids (BPCAs) as geochemical markers. The results showed that despite regular long term BC input, BC only contributed 7–11% of total soil organic carbon (SOC) in the topsoil horizons. Nevertheless, along with SOC, paddy soils accumulated BC with increasing duration of management until 297 years to reach a steady‐state of 13 t BC ha?1. This was 1.8 times more than in non‐paddy soils. The fate of BC in paddy soils (0–1 m) could be modeled revealing an average annual input of 44 kg ha?1 yr?1, and a mean residence time of 303 years. The subsoils contributed at least 50% to overall BC stocks, which likely derived from periods prior to land embankment and episodic burial of ancient topsoil, as also indicated by BPCA pattern changes. We conclude that there is a significant but limited accumulation of C in charred forms upon prolonged paddy management. The final contribution of BC to total SOC in paddy soils was similar to that in other aerobic ecosystems of the world.  相似文献   
995.
Objective: Lymph node metastasis leads to high mortality rates of oral squamous cell carcinoma (OSCC). However, it is still controversial to define clinically negative neck (cN0) and positive neck (cN1-3).

Methods: We retrieved candidate biomarkers identified by proteomic analysis in OSCC from published works of literature. In training stage, immunohistochemistry (IHC) analysis was used to determine the expression of proteins and logistic regression models with stepwise variable selection were used to identify potential factors that might affect lymph node metastasis and life status. Furthermore, the prediction model was validated in validating stage.

Results: We screened eight highly expressed proteins related to lymph node metastasis in OSCC and found that the expression levels of SOD2, BST2, CAD, ITGB6, and PRDX4 were significantly elevated in patients with lymph node metastasis compared to the patients without lymph node metastasis. Furthermore, in training and validating stages, the prediction model base on the combination of CAD, SOD2 expression levels, and histopathologic grade was developed and validated in patients with OSCC.

Conclusions: Our findings showed that the developed model well predicts the lymph node metastasis and life status in patients with OSCC, independent of TNM stage.  相似文献   

996.
Biomechanics and Modeling in Mechanobiology - Spinal cord injury (SCI) is a global problem that brings a heavy burden to both patients and society. Recent investigations indicated degenerative...  相似文献   
997.
Al-Odaini  Najwa  Wei  Jin-ying  Zheng  Yan-qing  Zheng  Dong-yan  Khader  Jazeer A.  Cao  Cun-wei 《Mycopathologia》2022,187(2-3):291-298

Tinea nigra is a superficial fungal infection usually caused by Hortaea werneckii (H. werneckii). We report a special case of tinea nigra in an immunocompetent child who developed a unilateral, rapidly growing pigmented lesion on her palm. Interestingly, Curvularia lunata (C. lunata) was isolated from the lesion scrapes and was identified by both morphological features and molecular biology methods. The lesion was completely cleared by topical naftifine hydrochloride and ketoconazole cream. We present—to the best of our knowledge—the first case of tinea nigra where the causative pathogen was identified as C. lunata. We therefore provide a brief literature review of previously reported cases of tinea nigra to broaden the knowledge of the potential causative pathogens. The etiology, demography, clinical features, diagnostic methods, and treatment of the reviewed cases are summarized and analyzed.

  相似文献   
998.
999.
Many factors may affect reproduction of animal-pollinated species. In this study, the effects of pollen limitation, attractive traits (flower number, plant height and flower width) and flowering phenological traits (flowering onset, duration and synchrony) on female reproduction, as well as the patterns of variation in fruit and seed production within plants, were investigated in Paeonia ostii “Feng Dan” over two flowering seasons (2018 and 2019). Fruit set was very high (90%), and pollen supplementation did not increase fruit and seed production in either year, indicating no pollen limitation. Fruit set, ovule number per fruit and mean individual seed weight per fruit were not affected by any of the six attractive and phenological traits in either year, whereas seed number per fruit was related to the three attractive traits in one or both years. Seed number per plant was positively affected by the three attractive traits and best explained by flower number in both years, but the effect of each of the three phenological traits on seed number per plant differed between years. Within plants, the fruit set, ovule number, seed set and seed number per fruit declined from early- to late-opening flowers, presumably because of resource preemption, but the mean individual seed weight did not vary across the flowering sequence. Our study shows that attractive traits of Paeonia ostii “Feng Dan” are more important than flowering phenological traits in the prediction of total seed production per plant.  相似文献   
1000.
Deregulation of tripartite motif (TRIM) family proteins contribute to multiple biological processes such as neurodegeneration, development, inflammation, cell survival, apoptosis, and carcinogenesis. However, the biological function and molecular mechanism of TRIM family proteins in osteosarcoma chemoresistance remain unclear. In the current study, we found the protein expression of TRIM10 was markedly overexpressed in cisplatin resistance's osteosarcoma tissues and TRIM10 overexpression was inversely correlated with osteosarcoma patient survival. Furthermore, overexpression of TRIM10 confers cisplatin resistance on osteosarcoma cells; however, repressing TRIM10 sensitized osteosarcoma cell lines to cisplatin cytotoxicity in vitro. Mechanically, TRIM10 upregulated the nuclear levels of p65, thereby activating canonical NF-κB signaling. Taken together, our results suggest that TRIM10 contributed to cisplatin resistance in osteosarcoma cells, and targeting the TRIM10/p65 axis may represent a promising strategy to enhance cisplatin response in osteosarcoma patients with chemoresistance.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号