全文获取类型
收费全文 | 5253篇 |
免费 | 563篇 |
国内免费 | 812篇 |
专业分类
6628篇 |
出版年
2024年 | 22篇 |
2023年 | 94篇 |
2022年 | 203篇 |
2021年 | 321篇 |
2020年 | 243篇 |
2019年 | 316篇 |
2018年 | 236篇 |
2017年 | 207篇 |
2016年 | 233篇 |
2015年 | 354篇 |
2014年 | 421篇 |
2013年 | 429篇 |
2012年 | 516篇 |
2011年 | 498篇 |
2010年 | 305篇 |
2009年 | 248篇 |
2008年 | 311篇 |
2007年 | 223篇 |
2006年 | 221篇 |
2005年 | 178篇 |
2004年 | 152篇 |
2003年 | 152篇 |
2002年 | 178篇 |
2001年 | 98篇 |
2000年 | 95篇 |
1999年 | 74篇 |
1998年 | 69篇 |
1997年 | 36篇 |
1996年 | 47篇 |
1995年 | 30篇 |
1994年 | 28篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
排序方式: 共有6628条查询结果,搜索用时 8 毫秒
991.
对皖南和赣北早奥陶世早特马道克期的Staurograptus重新研究表明,该属具有原始枝末端正分推迟、分支级数缩减和笔石枝密度降低的演化趋势,而代表不同演化阶段的三个种类,即Staurograptus dichotomus Emmons,S.apertus Ruedemann和S.hyperboreus Obut et Sobolevskaya,构成了该属基本的系统发育谱系。种群分析进一步显示,其主要性状变异范围尽管较宽但趋于正态分布的S.dichotomus,可能包含了除S.apertus和S.hyperboreus之外的所有已知Staurograptus的异名种类。 相似文献
992.
目的:观察滋肾骨康丸治疗骨质疏松症的临床疗效,并对该药的作用机理进行探讨。方法:将60例病人随机分为治疗组(滋肾骨康丸组)及对照组(西药组),根据2组骨密度、骨痛、中医证候结果及临床总体疗效为指标进行比较。结果:治疗组治疗后总有效率为95.8%,对照组治疗后总有效率为75.3%,差异有统计学意义(P〈0.01);2组治疗前后骨密度无显著性差异(P〉0.05);治疗组治疗后骨痛有效率为92.5%。优于对照组的7313%(P〈0.05);治疗后治疗组中医证候有效率为100%,明显优于对照组的53.3%(P〈0.01)。结论:滋肾骨康丸能显著改善骨痛、肾虚证候,总体改善临床症状,具有较好的治疗作用,值得进一步推广。 相似文献
993.
Genetic studies in mice and humans have revealed a pivotal function for transforming growth factor-beta (TGF-β) in vascular development and maintenance of vascular homeostasis. Mice deficient for various TGF-β signaling components develop an embryonic lethality due to vascular defects. In patients, mutations in TGF-β receptors have been linked to vascular dysplasia like Hereditary Hemorrhagic Telangiectasia (HHT) and pulmonary arterial hypertension (PAH). Besides indirect effects by regulating the expression of angiogenic regulators, TGF-β also has potent direct effects on endothelial cell growth and migration, and we have proposed that TGF-β regulates the activation state of the endothelium via two opposing type I receptor/Smad pathways, activin receptor-like kinase (ALK)1 and ALK5. TGF-β is also critical for the differentiation of mural precursors into pericytes and smooth muscle cells. Furthermore, defective paracrine TGF-β signaling between endothelial and neighboring mural cells may be responsible for a leaky vessel phenotype that is characteristic of HHT. In this review, we discuss our current understanding of the TGF-β signaling pathway and its regulation of endothelial and vascular smooth muscle cell function. 相似文献
994.
995.
996.
Intake of cruciferous vegetable is inversely associated with the risk of several cancer types. Isothiocyanates (ITCs) are believed to be important constituents contributing to these cancer-preventive effects. Although several mechanisms, including induction of apoptosis, have been proposed for the anti-carcinogenesis activities of ITCs, detailed upstream triggering events are still not fully understood. Identification of ITC binding targets in cellular proteins is crucial for not only mechanistic studies but also future drug screening and design. In this review, we summarize recent progress in discovery of ITC protein targets from a technical perspective. The advantages and limitations of each method are discussed to facilitate future studies on target discovery of ITCs and perhaps other compounds. 相似文献
997.
998.
Autophagy mediated CoCrMo particle-induced peri-implant osteolysis by promoting osteoblast apoptosis
Zhenheng Wang Naicheng Liu Kang Liu Gang Zhou Jingjing Gan Zhenzhen Wang Tongguo Shi Wei He Lintao Wang Ting Guo Nirong Bao Rui Wang Zhen Huang Jiangning Chen Lei Dong Jianning Zhao Junfeng Zhang 《Autophagy》2015,11(12):2358-2369
Wear particle-induced osteolysis is the leading cause of aseptic loosening, which is the most common reason for THA (total hip arthroplasty) failure and revision surgery. Although existing studies suggest that osteoblast apoptosis induced by wear debris is involved in aseptic loosening, the underlying mechanism linking wear particles to osteoblast apoptosis remains almost totally unknown. In the present study, we investigated the effect of autophagy on osteoblast apoptosis induced by CoCrMo metal particles (CoPs) in vitro and in a calvarial resorption animal model. Our study demonstrated that CoPs stimulated autophagy in osteoblasts and PIO (particle-induced osteolysis) animal models. Both autophagy inhibitor 3-MA (3-methyladenine) and siRNA of Atg5 could dramatically reduce CoPs-induced apoptosis in osteoblasts. Further, inhibition of autophagy with 3-MA ameliorated the severity of osteolysis in PIO animal models. Moreover, 3-MA also prevented osteoblast apoptosis in an antiautophagic way when tested in PIO model. Collectively, these results suggest that autophagy plays a key role in CoPs-induced osteolysis and that targeting autophagy-related pathways may represent a potential therapeutic approach for treating particle-induced peri-implant osteolysis. 相似文献
999.
1000.
Zhang Zhen Zhang Yu Zhang Shanying Wang Lifeng Liang Xiaoyu Wang Xinquan Wu Huiyi Zou Haotian Zhang Chenghui Wang Meng 《Journal of Plant Growth Regulation》2022,41(6):2232-2245
Journal of Plant Growth Regulation - Mulberry (Morus alba L.) leaf, a “source of both medicine and food”, contains antioxidant ingredients such as flavonoids, alkaloids and polyphenols.... 相似文献