全文获取类型
收费全文 | 48917篇 |
免费 | 18068篇 |
国内免费 | 12篇 |
出版年
2022年 | 260篇 |
2021年 | 726篇 |
2020年 | 2375篇 |
2019年 | 3946篇 |
2018年 | 4124篇 |
2017年 | 4350篇 |
2016年 | 4562篇 |
2015年 | 4787篇 |
2014年 | 4547篇 |
2013年 | 5134篇 |
2012年 | 3149篇 |
2011年 | 2908篇 |
2010年 | 3932篇 |
2009年 | 2652篇 |
2008年 | 1853篇 |
2007年 | 1334篇 |
2006年 | 1225篇 |
2005年 | 1220篇 |
2004年 | 1245篇 |
2003年 | 1162篇 |
2002年 | 1093篇 |
2001年 | 801篇 |
2000年 | 775篇 |
1999年 | 645篇 |
1998年 | 287篇 |
1997年 | 272篇 |
1996年 | 252篇 |
1995年 | 239篇 |
1994年 | 238篇 |
1993年 | 232篇 |
1992年 | 421篇 |
1991年 | 411篇 |
1990年 | 397篇 |
1989年 | 366篇 |
1988年 | 337篇 |
1987年 | 314篇 |
1986年 | 267篇 |
1985年 | 285篇 |
1984年 | 245篇 |
1983年 | 241篇 |
1982年 | 185篇 |
1981年 | 184篇 |
1979年 | 240篇 |
1978年 | 206篇 |
1977年 | 196篇 |
1976年 | 190篇 |
1975年 | 185篇 |
1974年 | 178篇 |
1973年 | 194篇 |
1972年 | 181篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
Julian Johnson 《The Western journal of medicine》1956,85(3):147-151
The best opportunities at present for improving the results in the treatment of patients with cancer of the lung are by way of (a) utilizing the information obtained on routine x-ray examination of the chest, (b) decreasing the delay between the time of the first symptoms and the time the patient consults a physician, and (c) decreasing the delay between the time the patient first consults a physician and the time the cancer is surgically removed.The medical profession must increase its index of suspicion of cancer of the lung and persist in efforts to make a diagnosis when lung cancer is suspected.Exploratory thoracotomy should be used in suspicious cases when the diagnosis cannot be established by other methods. 相似文献
122.
Jian‐Yong Guo Yong‐Sheng Wang Tian Chen Xiao‐Xu Jiang Ping Wu Tao Geng Zhong‐Hua Pan Meng‐Ke Shang Cheng‐Xiang Hou Kun Gao Xi‐Jie Guo 《Insect Science》2020,27(3):449-462
Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a major pathogen of the economic insect silkworm, Bombyx mori. Virus‐encoded microRNAs (miRNAs) have been proven to play important roles in host–pathogen interactions. In this study we identified a BmCPV‐derived miRNA‐like 21 nt small RNA, BmCPV‐miR‐1, from the small RNA deep sequencing of BmCPV‐infected silkworm larvae by stem‐loop quantitative real‐time PCR (qPCR) and investigated its functions with qPCR and lentiviral expression systems. Bombyx mori inhibitor of apoptosis protein (BmIAP) gene was predicted by both target prediction software miRanda and Targetscan to be one of its target genes with a binding site for BmCPV‐miR‐1 at the 5′ untranslated region. It was found that the expression of BmCPV‐miR‐1 and its target gene BmIAP were both up‐regulated in BmCPV‐infected larvae. At the same time, it was confirmed that BmCPV‐miR‐1 could up‐regulate the expression of BmIAP gene in HEK293T cells with lentiviral expression systems and in BmN cells by transfecting mimics. Furthermore, BmCPV‐miR‐1 mimics could up‐regulate the expression level of BmIAP gene in midgut and fat body in the silkworm. In the midgut of BmCPV‐infected larvae, BmCPV‐miR‐1 mimics could be further up‐regulated and inhibitors could lower the virus‐mediated expression of BmIAP gene. With the viral genomic RNA segments S1 and S10 as indicators, BmCPV‐miR‐1 mimics could up‐regulate and inhibitors down‐regulate their replication in the infected silkworm. These results implied that BmCPV‐miR‐1 could inhibit cell apoptosis in the infected silkworm through up‐regulating BmIAP expression, providing the virus with a better cell circumstance for its replication. 相似文献
123.
Changes in total body calcium balance with exercise in the rat 总被引:2,自引:0,他引:2
LeBlanc A. D.; Evans H. J.; Johnson P. C.; Jhingran S. 《Journal of applied physiology》1983,55(1):201-204
124.
Jyri Seppla Matti Melanen Ilmo Menp Sirkka Koskela Jyrki Tenhunen Marja‐Riitta Hiltunen 《Journal of Industrial Ecology》2005,9(4):117-130
The concept of eco-efficiency is commonly referred to as a business link to sustainable development. In this article, ecoefficiency is examined at a regional level as an approach to promoting the competitiveness of economic activities in the Finnish Kymenlaakso region and mitigating their harmful impacts on the environment. The aim is to develop appropriate indicators for monitoring changes in the eco-efficiency of the region. A starting point is to produce indicators for the environmental and economic dimensions of regional development and use them for measuring regional eco-efficiency. The environmental impact indicators are based on a life-cycle assessment method, producing different types of environmental impact indicators: pressure indicators (e.g., emissions of CO2 ), impact category indicators (e.g., CO2 equivalents in the case of climate change), and a total impact indicator (aggregating different impact category indicator results into a single value). Environmental impact indicators based on direct material input, total material input, and total material requirement of the Kymenlaakso region are also assessed. The economic indicators used are the gross domestic product, the value added, and the output of the main economic sectors of Kymenlaakso. In the eco-efficiency assessment, the economic and environmental impact indicators are monitored in the same graph. In a few cases eco-efficiency ratios can also be calculated (the economic indicators are divided by the environmental indicators). Output (= value added + intermediate consumption) is used as an economic indicator related to the environmental impact indicators, which also cover the upstream processes of the region's activities. In the article, we also discuss the strengths and weaknesses of using the different environmental impact indicators. 相似文献
125.
126.
Oscar Fernandez‐Capetillo 《EMBO reports》2010,11(1):32-36
Ageing is an unavoidable corollary to being alive; the most intuitive interpretation of ageing being that it is the consequence of progressive body degeneration. In agreement with this, current models propose that ageing occurs through a stepwise accumulation of DNA damage, which ultimately limits the regenerative capacity of tissues. On the other hand, there is increasing evidence that fetal distress can influence the development of disease in adult life, a phenomenon known as ‘intrauterine programming’. The extent to which an intrauterine exposure to DNA damage can compromise lifespan remains unclear. My group has recently generated a murine model of a human syndrome linked to defective DNA repair and observed that these animals age prematurely, but the accumulation of DNA damage is restricted mostly to the embryonic period. Here, I discuss the implications of this finding and propose that ageing can be influenced by fetal distress. 相似文献
127.
128.
A SENSITIVE RADIOIMMUNOASSAY FOR 7S NERVE GROWTH FACTOR ANTIGENS IN SERUM AND TISSUES 总被引:12,自引:4,他引:8
A radioimmunoassay was developed which can measure accurately concentrations of mouse 7S nerve growth factor antigens (NGFA) as low as 3·0 ng/ml in serum or tissue homogenates. Extremely large amounts of presumed nerve growth factor were found in the submaxillary gland; but considerable quantities were also present in mouse serum, kidney, adrenal gland and vas deferens. Heart, spleen, liver and muscle contained less of the presumed nerve growth factor, and only small amounts were recovered from brain. Rat adrenal gland and serum from rats, guinea pigs and man contained much less immunologically reactive material. The level of presumed nerve growth factor in the mouse heart was highest at birth and decreased slowly during maturation. In the mouse submaxillary gland the content of presumed nerve growth factor increased rapidly after 2 weeks of postnatal age, with higher levels found in male animals. Destruction with 6-hydroxydopamine of the sympathetic nerves in the hearts of newborn or adult mice did not significantly alter the amount of presumed nerve growth factor recovered in the heart. 相似文献
129.
130.
Yanyan Han Elfriede Eppinger Ingrid G. Schuster Luise U. Weigand Xiaoling Liang Elisabeth Kremmer Christian Peschel Angela M. Krackhardt 《The Journal of biological chemistry》2009,284(48):33409-33417
The formin protein formin-like 1 (FMNL1) is highly restrictedly expressed in hematopoietic lineage-derived cells and has been previously identified as a tumor-associated antigen. However, function and regulation of FMNL1 are not well defined. We have identified a novel splice variant (FMNL1γ) containing an intron retention at the C terminus affecting the diaphanous autoinhibitory domain (DAD). FMNL1γ is specifically located at the cell membrane and cortex in diverse cell lines. Similar localization of FMNL1 was observed for a mutant lacking the DAD domain (FMNL1ΔDAD), indicating that deregulation of autoinhibition is effective in FMNL1γ. Expression of both FMNL1γ and FMNL1ΔDAD induces polarized nonapoptotic blebbing that is dependent on N-terminal myristoylation of FMNL1 but independent of Src and ROCK activity. Thus, our results describe N-myristoylation as a regulative mechanism of FMNL1 responsible for membrane trafficking potentially involved in a diversity of polarized processes of hematopoietic lineage-derived cells. 相似文献