全文获取类型
收费全文 | 11511篇 |
免费 | 829篇 |
国内免费 | 834篇 |
出版年
2024年 | 21篇 |
2023年 | 159篇 |
2022年 | 401篇 |
2021年 | 700篇 |
2020年 | 405篇 |
2019年 | 514篇 |
2018年 | 458篇 |
2017年 | 335篇 |
2016年 | 491篇 |
2015年 | 757篇 |
2014年 | 875篇 |
2013年 | 859篇 |
2012年 | 1103篇 |
2011年 | 896篇 |
2010年 | 533篇 |
2009年 | 498篇 |
2008年 | 541篇 |
2007年 | 512篇 |
2006年 | 410篇 |
2005年 | 390篇 |
2004年 | 305篇 |
2003年 | 272篇 |
2002年 | 208篇 |
2001年 | 209篇 |
2000年 | 157篇 |
1999年 | 175篇 |
1998年 | 104篇 |
1997年 | 120篇 |
1996年 | 111篇 |
1995年 | 103篇 |
1994年 | 109篇 |
1993年 | 67篇 |
1992年 | 70篇 |
1991年 | 85篇 |
1990年 | 57篇 |
1989年 | 44篇 |
1988年 | 27篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 24篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Ultrastructural observation of mesophyll cells and temporal expression profiles of the genes involved in transitory starch metabolism in flag leaves of wheat after anthesis 下载免费PDF全文
992.
微藻的闪光效应可以大幅提高微藻的光效率,提高微藻产量。通过在传统的板式光生物反应器中加入斜挡板以增强微藻的闪光效应。以小球藻为模型藻种,考察了新型板式光生物反应器内不同光强和不同进口流速对小球藻生长速率和光效率的影响。结果表明,当进口流速为0.16 m/s时,随着光强的提高,小球藻的细胞浓度逐渐增加,光效率逐渐降低;在500μmol/(m2·s)的光强条件下,小球藻细胞浓度和光效率均随着进口流速的提高而增加。新型板式光生物反应器内小球藻的细胞浓度比传统板式光生物反应器提高了39.23%,表明在传统板式光生物反应器内加入斜挡板可有效增强微藻的闪光效应。 相似文献
993.
994.
Zhen Liang Shiqi Li Xin Xu Xianglai Xu Xiao Wang Jian Wu Yi Zhu Zhenghui Hu Yiwei Lin Yeqing Mao Hong Chen Jindan Luo Ben Liu Xiangyi Zheng Liping Xie 《Molecules and cells》2015,38(2):130-137
MicroRNAs (miRNAs) are small, endogenous RNAs that play important gene-regulatory roles by binding to the imperfectly complementary sequences at the 3′-UTR of mRNAs and directing their gene expression. Here, we first discovered that miR-576-3p was down-regulated in human bladder cancer cell lines compared with the non-malignant cell line. To better characterize the role of miR-576-3p in bladder cancer cells, we over-expressed or down-regulated miR-576-3p in bladder cancer cells by transfecting with chemically synthesized mimic or inhibitor. The overexpression of miR-576-3p remarkably inhibited cell proliferation via G1-phase arrest, and decreased both mRNA and protein levels of cyclin D1 which played a key role in G1/S phase transition. The knock-down of miR-576-3p significantly promoted the proliferation of bladder cancer cells by accelerating the progression of cell cycle and increased the expression of cyclin D1. Moreover, the dual-luciferase reporter assays indicated that miR-576-3p could directly target cyclin D1 through binding its 3′-UTR. All the results demonstrated that miR-576-3p might be a novel suppressor of bladder cancer cell proliferation through targeting cyclin D1. 相似文献
995.
996.
Helicobacter pylori (H. pylori) infection has been associated with gastric disorders. The situation of H. pylori infection in China—where a high prevalence of H. pylori infection, a high incidence of gastric cancer, and widespread resistance to clarithromycin, metronidazole, and levofloxacin exist—is quite different from that in Western countries. In order for Chinese clinicians to better manage H. pylori infection, a Chinese Study Group on H. pylori published four consensus reports regarding the management of H. pylori infection in China between 1999 and 2012. The eradication rate with standard triple therapy was <80% in most areas of China. Bismuth is available in China, and bismuth‐containing quadruple therapy has been shown to produce a high eradication rate; thus, bismuth quadruple therapy could be recommended both as an initial and as a rescue therapy in China. There is no advantage of sequential therapy over triple therapy in Chinese patients, but the efficacy of concomitant therapy must be studied further. This review introduces the epidemiology, diagnosis, indicators, and therapies for the eradication of H. pylori in China in recent years. 相似文献
997.
998.
For at least the past two decades, eco‐industrial parks (EIPs) have been promoted as policy and commercial instruments for achieving industrial sustainable development. Yet, few EIPs have seen successful operational implementation, especially if they begin as standard industrial parks. Rapid economic growth, commensurate with increasing environmental damage in China, has resulted in officials’ further pursuing EIP policy as a significant element of the broader circular economy and ecological modernization efforts. This article examines the barriers for EIP development from industrial park senior manager perspectives. Using resource dependence theory and the resource‐based view as theoretical lenses, we investigate the external and internal barriers for EIP development in 51 Chinese industrial parks. A number of barriers are identified and grouped through a factor analysis. Cluster analysis is utilized to help categorize and evaluate the perceived levels of barriers and hardships experienced by various senior officials that manage the EIPs. It is found that few respondents encounter no significant barriers. Barriers related to technological development and capacity building are the most prevalent. These results highlight the relative importance of various activities that may be necessary by policy makers and other stakeholders to overcome the barriers. For example, cooperation in developing technological solutions for EIPs seems to be a major thrust that should be pursued by EIP development stakeholders. Other policy and managerial insights based on the general findings of this study are also presented. 相似文献
999.
Kai Meng Qiutang Zeng Qinghua Lu Yingzhong Lin Bangwei Wu Kunwu Yu Zhaoqiang Dong Jianwei Zhang Meng Chai Yuyang Liu Qingwei Ji Yujie Zhou 《Molecular medicine (Cambridge, Mass.)》2015,21(1):143-153
Valsartan has a protective effect against hypertension and atherosclerosis in humans and experimental animal models. This study aimed to determine the effect of prolonged treatment with angiotensin II (Ang II) on atherosclerosis and the effect of valsartan on the activity of CD4+ T lymphocyte subsets. The results showed that prolonged treatment (8 wks) with exogenous Ang II resulted in an increased atherosclerotic plaque size and a switch of stable-to-unstable plaque via modulating on CD4+ T lymphocyte activity, including an increase in the T helper cell type 1 (Th1) and Th17 cells and a decrease in Th2 and regulatory T (Treg) cells. In contrast, valsartan treatment efficiently reversed the imbalance in CD4+ T lymphocyte activity, ameliorated atherosclerosis and elicited a stable plaque phenotype in addition to controlling blood pressure. In addition, treatment with anti-interleukin (IL)-5 monoclonal antibodies weakened the antiatherosclerotic effects of valsartan without affecting blood pressure. 相似文献
1000.