全文获取类型
收费全文 | 3723篇 |
免费 | 284篇 |
专业分类
4007篇 |
出版年
2022年 | 34篇 |
2021年 | 38篇 |
2020年 | 35篇 |
2019年 | 27篇 |
2018年 | 58篇 |
2017年 | 37篇 |
2016年 | 81篇 |
2015年 | 124篇 |
2014年 | 117篇 |
2013年 | 205篇 |
2012年 | 252篇 |
2011年 | 236篇 |
2010年 | 165篇 |
2009年 | 175篇 |
2008年 | 203篇 |
2007年 | 182篇 |
2006年 | 172篇 |
2005年 | 196篇 |
2004年 | 183篇 |
2003年 | 169篇 |
2002年 | 159篇 |
2001年 | 30篇 |
2000年 | 41篇 |
1999年 | 46篇 |
1998年 | 63篇 |
1997年 | 39篇 |
1996年 | 38篇 |
1995年 | 44篇 |
1994年 | 40篇 |
1993年 | 42篇 |
1992年 | 41篇 |
1991年 | 30篇 |
1990年 | 15篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 20篇 |
1985年 | 27篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 27篇 |
1981年 | 28篇 |
1980年 | 29篇 |
1979年 | 29篇 |
1978年 | 34篇 |
1977年 | 21篇 |
1976年 | 19篇 |
1974年 | 15篇 |
1973年 | 18篇 |
1970年 | 14篇 |
1957年 | 16篇 |
排序方式: 共有4007条查询结果,搜索用时 0 毫秒
121.
122.
E. Stresemann G. Mauersberger H. E. Wolters Richard Heyder und Kurt Maass 《Journal of Ornithology》1956,97(4):441-443
Ohne Zusammenfassung 相似文献
123.
124.
125.
126.
Age‐related deterioration of motor function in male and female 5xFAD mice from 3 to 16 months of age
Timothy P. O'Leary Hector M. Mantolino Kurt R. Stover Richard E. Brown 《Genes, Brain & Behavior》2020,19(3)
Alzheimer's disease (AD) is a neurodegenerative disorder that leads to age‐related cognitive and sensori‐motor dysfunction. There is an increased understanding that motor dysfunction contributes to overall AD severity, and a need to ameliorate these impairments. The 5xFAD mouse develops the neuropathology, cognitive and motor impairments observed in AD, and thus may be a valuable animal model to study motor deficits in AD. Therefore, we assessed age‐related changes in motor ability of male and female 5xFAD mice from 3 to 16 months of age, using a battery of behavioral tests. At 9‐10 months, 5xFAD mice showed reduced body weight, reduced rearing in the open‐field and impaired performance on the rotarod compared to wild‐type controls. At 12‐13 months, 5xFAD mice showed reduced locomotor activity on the open‐field, and impaired balance on the balance beam. At 15‐16 months, impairments were also seen in grip strength. Although sex differences were observed at specific ages, the development of motor dysfunction was similar in male and female mice. Given the 5xFAD mouse is commonly on a C57BL/6 × SJL hybrid background, a subset of mice may be homozygous recessive for the Dysf im mutant allele, which leads to muscular weakness in SJL mice and may exacerbate motor dysfunction. We found small effects of Dysf im on motor function, suggesting that Dysf im contributes little to motor dysfunction in 5xFAD mice. We conclude that the 5xFAD mouse may be a useful model to study mechanisms that produce motor dysfunction in AD, and to assess the efficacy of therapeutics on ameliorating motor impairment. 相似文献
127.
Patricia M. LoRusso Kurt Schalper Jeffrey Sosman 《Pigment cell & melanoma research》2020,33(3):390-402
Targeted therapy directed against oncogenic BRAF mutations and immune checkpoint inhibitors have transformed melanoma therapy over the past decade and prominently improved patient outcomes. However, not all patients will respond to targeted therapy or immunotherapy and many relapse after initially responding to treatment. This unmet need presents two major challenges. First, can we elucidate novel oncogenic drivers to provide new therapeutic targets? Second, can we identify patients who are most likely to respond to current therapeutic strategies in order to both more accurately select populations and avoid undue drug exposure in patients unlikely to respond? In an effort to evaluate the current state of the field with respect to these questions, we provide an overview of some common oncogenic mutations in patients with metastatic melanoma and ongoing efforts to therapeutically target these populations, as well as a discussion of biomarkers for response to immune checkpoint inhibitors—including tumor programmed death ligand 1 expression and the future use of neoantigens as a means of truly personalized therapy. This information is becoming important in treatment decision making and provides the framework for a treatment algorithm based on the current landscape in metastatic melanoma. 相似文献
128.
Enrique Murillo Attila Agócs Veronika Nagy Sándor Balázs Király Tibor Kurtán Eunice Molinar Toribio Johant Lakey-Beitia József Deli 《Chirality》2020,32(5):579-587
Two new carotenoids, sapotexanthin 5,6-epoxide and sapotexanthin 5,8-epoxide, have been isolated from the ripe fruits of red mamey (Pouteria sapota). Sapotexanthin 5,6-epoxide was also prepared by partial synthesis via epoxidation of sapotexanthin, and the (5R,6S) and (5S,6R) stereoisomers were identified by high-performance liquid chromatography–electronic circular dichroism (HPLC-ECD) analysis. Spectroscopic data of the natural and semisynthetic derivatives obtained by acid-catalyzed rearrangement of cryptocapsin 5,8-epoxide stereoisomers were compared for structural elucidation. 相似文献
129.
Trigonostemons G and H, two novel dimeric dinorditerpenoids, were isolated from the stem barks of Trigonostemon chinensis. Their planar structures and relative configurations were established by extensive analysis of spectroscopic data. Trigonostemons G and H possess a homodimeric biaryl skeleton obtained from two rearranged chiral nonracemic abietane-type dinorditerpenes through an axially chiral biaryl 11,11′-linkage. Torsional scan and computation of the transition states were carried out to estimate the rotational energy barrier, and the axial chirality (aS) was determined by time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. The positive n-π* ECD transitions of the isolated carbonyl chromophore above 300 nm could be used to determine the central chirality of trigonostemon G independently by ECD calculations of the diastereomers. 相似文献
130.