全文获取类型
收费全文 | 126248篇 |
免费 | 3111篇 |
国内免费 | 2699篇 |
专业分类
132058篇 |
出版年
2024年 | 69篇 |
2023年 | 395篇 |
2022年 | 937篇 |
2021年 | 1638篇 |
2020年 | 1040篇 |
2019年 | 1255篇 |
2018年 | 12739篇 |
2017年 | 11277篇 |
2016年 | 8587篇 |
2015年 | 2593篇 |
2014年 | 2633篇 |
2013年 | 2826篇 |
2012年 | 7179篇 |
2011年 | 15318篇 |
2010年 | 13494篇 |
2009年 | 9517篇 |
2008年 | 11305篇 |
2007年 | 12708篇 |
2006年 | 1599篇 |
2005年 | 1634篇 |
2004年 | 1958篇 |
2003年 | 1859篇 |
2002年 | 1505篇 |
2001年 | 931篇 |
2000年 | 838篇 |
1999年 | 678篇 |
1998年 | 394篇 |
1997年 | 359篇 |
1996年 | 368篇 |
1995年 | 333篇 |
1994年 | 332篇 |
1993年 | 245篇 |
1992年 | 371篇 |
1991年 | 307篇 |
1990年 | 313篇 |
1989年 | 264篇 |
1988年 | 206篇 |
1987年 | 184篇 |
1986年 | 152篇 |
1985年 | 134篇 |
1984年 | 128篇 |
1983年 | 112篇 |
1982年 | 79篇 |
1981年 | 61篇 |
1979年 | 75篇 |
1978年 | 55篇 |
1977年 | 53篇 |
1975年 | 64篇 |
1972年 | 287篇 |
1971年 | 310篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
251.
Ana O. Fagundes Maira R. Aguiar Claudia S. Aguiar Giselli Scaini Monique U. Sachet Nayara M. Bernhardt Gislaine T. Rezin Samira S. Valvassori João Quevedo Emilio L. Streck 《Neurochemical research》2010,35(11):1675-1680
Methylphenidate is commonly used for the treatment of attention deficit/hyperactivity disorder. There are still few works
regarding the effects of methylphenidate on brain energy metabolism. Thus, in the present study we evaluated the effect of
chronic administration of methylphenidate on the activities of mitochondrial respiratory chain complexes I and III in the
brain of young rats. The effect of acute administration of methylphenidate on mitochondrial respiratory chain complexes I,
II, III and IV in the brain of young rats was also investigated. For acute administration, a single injection of methylphenidate
was given to rats on postnatal day 25. For chronic administration, methylphenidate injections were given starting at postnatal
day 25 once daily for 28 days. Our results showed that complexes I and III were not affected by chronic administration of
methylphenidate. Moreover, the acute administration of methylphenidate decreased complex I activity in cerebellum and prefrontal
cortex, whereas complexes II, III and IV were not altered. 相似文献
252.
Shenghe Huang Ruijie Liu Yiding Niu Agula Hasi 《Russian Journal of Plant Physiology》2010,57(4):568-573
253.
Patient management in Idiopathic Pulmonary Fibrosis (IPF) is largely based on societal guidelines and recommendations. A recent update by the American Thoracic Society (ATS), European Respiratory Society (ERS), Japanese Respiratory Society (JRS) and Latin American Thoracic Association (ALAT) provided updated guidance on the diagnosis and management of IPF, along with recommendations on pharmacologic and non-pharmacologic approaches to patient management. The treatment guidance is based on GRADE criteria, which rates the quality of evidence according to previously published methodology. Here we discuss how to interpret the recent guideline updates and the implications of this guidance for clinical practice. In addition we discuss the assessment and recommendations for a number of pharmacological agents that have been the focus of clinical trials over the past years. Although no single pharmacological agent was recommended by the guidelines committee, we discuss how since then, more recent data have resulted in the approval of pirfenidone in Europe, and preliminary negative findings regarding the safety of a triple therapy regimen consisting of prednisone, azathioprine and N-acetylcysteine have raised the question of whether it is no longer a treatment option. As clinicians, we must interpret the available guidance and recommendations as we consider each individual patient and as we discuss the available clinical data and the patient’s own preferences in our approach to the management of this disease. 相似文献
254.
Laura Kay Ilse S. Pienaar Ruwini Cooray Gary Black Meera Soundararajan 《Molecular neurobiology》2018,55(9):7352-7365
The Miro GTPases represent an unusual subgroup of the Ras superfamily and have recently emerged as important mediators of mitochondrial dynamics and for maintaining neuronal health. It is now well-established that these enzymes act as essential components of a Ca2+-sensitive motor complex, facilitating the transport of mitochondria along microtubules in several cell types, including dopaminergic neurons. The Miros appear to be critical for both anterograde and retrograde mitochondrial transport in axons and dendrites, both of which are considered essential for neuronal health. Furthermore, the Miros may be significantly involved in the development of several serious pathological processes, including the development of neurodegenerative and psychiatric disorders. In this review, we discuss the molecular structure and known mitochondrial functions of the Miro GTPases in humans and other organisms, in the context of neurodegenerative disease. Finally, we consider the potential human Miros hold as novel therapeutic targets for the treatment of such disease. 相似文献
255.
Zhang?Lijuan Jifu?Liu Hao?Zhang Shanshan?Wu Lingyun?Huang Dacheng?He Xueyuan?XiaoEmail author 《中国科学C辑(英文版)》2005,48(6):641-647
There are multiple reports of autoimmune response in patients with lung cancer. To investigate whether a novel autoantibody
is present in patients with lung cancer and evaluate its clinical diagnostic and prognostic value, sera from 10 patients with
lung cancer and 10 normal individuals were analyzed using immunofluorescence and Western blotting. It was found that one serum
sample from the patients with squamous carcinoma gave a fine speckled pattern staining in nucleus and had a high titer antinuclear
autoantibody which could recognize 31 kD of nuclear protein isolated from both cancer cells and normal cells. The same patient’s
serum was further used to immunoprecipitate the target antigen. The protein bands were excised from the SDS-PAGE gels and
were analyzed with a Qstar Pulser I Quadrupole time-flight mass spectrometer, and the 31 kD target antigen was identified
as U1-AsnRNP. To test the prevalence of anti-U1-AsnRNP antibody, sera from 93 patients including 36 squmaous carcinomas (SCC),
26 adenocarcinomas (Ad), and 31 small cell carcinomas (SCLC) were screened by Western blotting. The results demonstrated that
anti-U1-A snRNP antibody was present in 50% of SCC sera, 26.9% of Ad sera and 54.8% of SCLC sera. In this paper, we report
for the first time that anti-U1-AsnRNP antibody could be detected in the patients with lung cancer. 相似文献
256.
Marcus Clauss Jan Adamczewski Reinhold R. Hofmann 《European Journal of Wildlife Research》2010,56(2):181-185
The intraruminal papillation pattern indicates the degree of rumen contents stratification and is related to the feeding niche
of a ruminant. Muskoxen (Ovibos moschatus) display a variety of morphophysiological adaptations typical for grazers. We investigated the intraruminal papillation of
22 free-ranging muskoxen from five different months by comparing the surface enlargement factor both between seasons and between
individual rumen regions. The seasonal pattern of rumen papillation indicated a distinct seasonality in food quality. The
intraruminal papillation indicated a moderate degree of rumen contents stratification typical for intermediate feeders. The
nutritional ecology of muskoxen is characterised by specific morphophysiological adaptations to a grass-dominated diet that
nevertheless allow extensive seasonal use of browse forage. 相似文献
257.
258.
259.
In this contribution, a simple, rapid, colorimeteric and selective assay for lysine was achieved by a controllable end-to-end assembly of gold nanorods (AuNRs) in the presence of Eu(3+) and lysine. This one-pot end-to-end assembly of 11-mercaptoundecanoic acid (MUA) modified AuNRs was occurred in Britton-Robinson buffer of pH 6.0, which involves the coordination binding between Eu(3+) and COO(-) groups as well as the electrostatic interaction of the COO(-) groups of MUA with the -NH(3)(+) group of lysine. As monitored by absorption spectra, scanning electron microscopic (SEM) images and dynamic light scattering (DLS) measurement, the end-to-end chain assembly results in large red-shift in the longitudinal plasmon resonance absorption (LPRA), giving red-to-blue color change of AuNRs. Importantly, it was found that the red-shift of LPRA is linearly proportional to the concentrations of lysine in the range of 5.0×10(-6)-1.0×10(-3)M with the limit of detection (LOD) being 1.6×10(-6)M (3σ/k). This red-shift of LPRA is highly selective, making it possible to develop a rapid, selective and visual assay for lysine in food samples. 相似文献
260.
Systems biology and its potential role in radiobiology 总被引:1,自引:0,他引:1
Feinendegen L Hahnfeldt P Schadt EE Stumpf M Voit EO 《Radiation and environmental biophysics》2008,47(1):5-23
About a century ago, Conrad Röentgen discovered X-rays, and Henri Becquerel discovered a new phenomenon, which Marie and Pierre Curie later coined as radio-activity. Since their seminal work, we have learned much about the physical properties of radiation and its effects on living matter. Alas, the more we discover, the more we appreciate the complexity of the biological processes that are triggered by radiation exposure and eventually lead (or do not lead) to disease. Equipped with modern biological methods of high-throughput experimentation, imaging, and vastly increased computational prowess, we are now entering an era where we can piece some of the multifold aspects of radiation exposure and its sequelae together, and develop a more systemic understanding of radiogenic effects such as radio-carcinogenesis than has been possible in the past. It is evident from the complexity of even the known processes that such an understanding can only be gained if it is supported by mathematical models. At this point, the construction of comprehensive models is hampered both by technical inadequacies and a paucity of appropriate data. Nonetheless, some initial steps have been taken already and the generally increased interest in systems biology may be expected to speed up future progress. In this context, we discuss in this article examples of relatively small, yet very useful models that elucidate selected aspects of the effects of exposure to ionizing radiation and may shine a light on the path before us. 相似文献