全文获取类型
收费全文 | 31592篇 |
免费 | 15994篇 |
国内免费 | 71篇 |
出版年
2023年 | 62篇 |
2022年 | 179篇 |
2021年 | 575篇 |
2020年 | 2291篇 |
2019年 | 3846篇 |
2018年 | 3977篇 |
2017年 | 4257篇 |
2016年 | 4281篇 |
2015年 | 4352篇 |
2014年 | 3985篇 |
2013年 | 4510篇 |
2012年 | 2290篇 |
2011年 | 1956篇 |
2010年 | 3372篇 |
2009年 | 2084篇 |
2008年 | 1039篇 |
2007年 | 579篇 |
2006年 | 539篇 |
2005年 | 544篇 |
2004年 | 543篇 |
2003年 | 452篇 |
2002年 | 456篇 |
2001年 | 313篇 |
2000年 | 221篇 |
1999年 | 177篇 |
1998年 | 56篇 |
1997年 | 51篇 |
1996年 | 41篇 |
1995年 | 43篇 |
1994年 | 40篇 |
1993年 | 44篇 |
1992年 | 37篇 |
1991年 | 33篇 |
1990年 | 36篇 |
1989年 | 35篇 |
1988年 | 20篇 |
1987年 | 21篇 |
1986年 | 20篇 |
1985年 | 29篇 |
1984年 | 29篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1967年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
Alba M. Franco‐Pereira Jacobo de Uña‐Álvarez 《Biometrical journal. Biometrische Zeitschrift》2013,55(1):52-67
In this paper, we introduce a new estimator of a percentile residual life function with censored data under a monotonicity constraint. Specifically, it is assumed that the percentile residual life is a decreasing function. This assumption is useful when estimating the percentile residual life of units, which degenerate with age. We establish a law of the iterated logarithm for the proposed estimator, and its ‐equivalence to the unrestricted estimator. The asymptotic normal distribution of the estimator and its strong approximation to a Gaussian process are also established. We investigate the finite sample performance of the monotone estimator in an extensive simulation study. Finally, data from a clinical trial in primary biliary cirrhosis of the liver are analyzed with the proposed methods. One of the conclusions of our work is that the restricted estimator may be much more efficient than the unrestricted one. 相似文献
995.
996.
Salma Kloula Ben Ghorbal Abdelwaheb Chatti Mohamed Marwan Sethom Lobna Maalej Mouadh Mihoub Sana Kefacha Moncef Feki Ahmed Landoulsi Abdennaceur Hassen 《Current microbiology》2013,67(1):112-117
The changes in lipid composition enable the micro-organisms to maintain membrane functions in the face of environmental fluctuations. The relationship between membrane fatty acid composition and UV-C stress was determined for mid-exponential phase and stationary phase Pseudomonas aeruginosa. The total lipids were obtained by dichloromethane/methanol (3:1) and were quantified by GC. The TLC analysis of phospholipids showed the presence of three major fractions phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. Significant modifications, as manifested by an increase of UFA, were obtained. Interestingly, this microorganism showed a remarkable capacity for recovery from the stressful effects of UV-C. 相似文献
997.
Yohsuke Ohba Eriko Kage‐Nakadai Naoko H Tomioka Nozomu Kono Rieko Imae Asuka Inoue Junken Aoki Naotada Ishihara Shohei Mitani Hiroyuki Arai 《The EMBO journal》2013,32(9):1265-1279
Glycerol‐3‐phosphate acyltransferase (GPAT) is involved in the first step in glycerolipid synthesis and is localized in both the endoplasmic reticulum (ER) and mitochondria. To clarify the functional differences between ER‐GPAT and mitochondrial (Mt)‐GPAT, we generated both GPAT mutants in C. elegans and demonstrated that Mt‐GPAT is essential for mitochondrial fusion. Mutation of Mt‐GPAT caused excessive mitochondrial fragmentation. The defect was rescued by injection of lysophosphatidic acid (LPA), a direct product of GPAT, and by inhibition of LPA acyltransferase, both of which lead to accumulation of LPA in the cells. Mitochondrial fragmentation in Mt‐GPAT mutants was also rescued by inhibition of mitochondrial fission protein DRP‐1 and by overexpression of mitochondrial fusion protein FZO‐1/mitofusin, suggesting that the fusion/fission balance is affected by Mt‐GPAT depletion. Mitochondrial fragmentation was also observed in Mt‐GPAT‐depleted HeLa cells. A mitochondrial fusion assay using HeLa cells revealed that Mt‐GPAT depletion impaired mitochondrial fusion process. We postulate from these results that LPA produced by Mt‐GPAT functions not only as a precursor for glycerolipid synthesis but also as an essential factor of mitochondrial fusion. 相似文献
998.
999.
1000.
Ole J Hamming Ewa Terczyńska‐Dyla Gabrielle Vieyres Ronald Dijkman Sanne E Jørgensen Hashaam Akhtar Piotr Siupka Thomas Pietschmann Volker Thiel Rune Hartmann 《The EMBO journal》2013,32(23):3055-3065
The IFNL4 gene is a recently discovered type III interferon, which in a significant fraction of the human population harbours a frameshift mutation abolishing the IFNλ4 ORF. The expression of IFNλ4 is correlated with both poor spontaneous clearance of hepatitis C virus (HCV) and poor response to treatment with type I interferon. Here, we show that the IFNL4 gene encodes an active type III interferon, named IFNλ4, which signals through the IFNλR1 and IL‐10R2 receptor chains. Recombinant IFNλ4 is antiviral against both HCV and coronaviruses at levels comparable to IFNλ3. However, the secretion of IFNλ4 is impaired compared to that of IFNλ3, and this impairment is not due to a weak signal peptide, which was previously believed. We found that IFNλ4 gets N‐linked glycosylated and that this glycosylation is required for secretion. Nevertheless, this glycosylation is not required for activity. Together, these findings result in the paradox that IFNλ4 is strongly antiviral but a disadvantage during HCV infection. 相似文献