全文获取类型
收费全文 | 60700篇 |
免费 | 4776篇 |
国内免费 | 3838篇 |
专业分类
69314篇 |
出版年
2024年 | 109篇 |
2023年 | 693篇 |
2022年 | 1674篇 |
2021年 | 2921篇 |
2020年 | 1860篇 |
2019年 | 2319篇 |
2018年 | 2186篇 |
2017年 | 1680篇 |
2016年 | 2427篇 |
2015年 | 3527篇 |
2014年 | 4174篇 |
2013年 | 4574篇 |
2012年 | 5226篇 |
2011年 | 4951篇 |
2010年 | 2925篇 |
2009年 | 2700篇 |
2008年 | 3115篇 |
2007年 | 2775篇 |
2006年 | 2403篇 |
2005年 | 2115篇 |
2004年 | 1723篇 |
2003年 | 1564篇 |
2002年 | 1324篇 |
2001年 | 1157篇 |
2000年 | 1047篇 |
1999年 | 1029篇 |
1998年 | 611篇 |
1997年 | 629篇 |
1996年 | 613篇 |
1995年 | 558篇 |
1994年 | 524篇 |
1993年 | 417篇 |
1992年 | 594篇 |
1991年 | 495篇 |
1990年 | 436篇 |
1989年 | 315篇 |
1988年 | 286篇 |
1987年 | 239篇 |
1986年 | 175篇 |
1985年 | 218篇 |
1984年 | 138篇 |
1983年 | 119篇 |
1982年 | 96篇 |
1981年 | 67篇 |
1980年 | 59篇 |
1979年 | 74篇 |
1978年 | 67篇 |
1977年 | 46篇 |
1976年 | 48篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
Xi Jiang Jingyin Yue Huimei Lu Neil Campbell Qifeng Yang Shijie Lan Bruce G. Haffty Changji Yuan Zhiyuan Shen 《International journal of biological sciences》2013,9(1):67-77
Filamin-A cross-links actin filaments into dynamic orthogonal networks, and interacts with an array of proteins of diverse cellular functions. Because several filamin-A interaction partners are implicated in signaling of cell mobility regulation, we tested the hypothesis that filamin-A plays a role in cancer metastasis. Using four pairs of filamin-A proficient and deficient isogenic cell lines, we found that filamin-A deficiency in cancer cells significantly reduces their migration and invasion. Using a xenograft tumor model with subcutaneous and intracardiac injections of tumor cells, we found that the filamin-A deficiency causes significant reduction of lung, splenic and systemic metastasis in nude mice. We evaluated the expression of filamin-A in breast cancer tissues by immunohistochemical staining, and found that low levels of filamin-A expression in cancer cells of the tumor tissues are associated with a better distant metastasis-free survival than those with normal levels of filamin-A. These data not only validate filamin-A as a prognostic marker for cancer metastasis, but also suggest that inhibition of filamin-A in cancer cells may reduce metastasis and that filamin-A can be used as a therapeutic target for filamin-A positive cancer. 相似文献
133.
Bing Xu Shaolin Wang Yan Jiang Linlin Yang Ping Li Caixia Xie 《Animal biotechnology》2013,24(4):217-225
Grass carp, Ctenopharyngodon idellus (Valenciennes, 1844), is an economically important species widely cultured in the world, but its genome research resources are largely lacking. The objectives of this study were to construct normalized cDNA libraries for efficient EST analysis, to generate ESTs from these libraries, and to identify EST-related molecular markers such as microsatellites and single nucleotide polymorphisms (SNPs) for genetic analysis of this species. A total of 6,269 ESTs were generated representing 4,815 unique sequences, from which 105 putative microsatellites and 5,228 SNPs were identified. These genome resources provide the material basis for future genetic and functional analyses in this species. 相似文献
134.
Rice stripe virus (RSV) is the type member of the genus Tenuivirus. RSV has four single-stranded RNAs and causes severe disease in rice fields in different parts of China. To date, no reports have described how RSV spreads within host plants or the viral and/or host factor(s) required for tenuivirus movement. We investigated functions of six RSV-encoded proteins using trans-complementation experiments and biolistic bombardment. We demonstrate that NSvc4, encoded by RSV RNA4, supports the intercellular trafficking of a movement-deficient Potato virus X in Nicotiana benthamiana leaves. We also determined that upon biolistic bombardment or agroinfiltration, NSvc4:enhanced green fluorescent protein (eGFP) fusion proteins localize predominantly near or within the walls of onion and tobacco epidermal cells. In addition, the NSvc4:eGFP fusion protein can move from initially bombarded cells to neighboring cells in Nicotiana benthamiana leaves. Immunocytochemistry using tissue sections from RSV-infected rice leaves and an RSV NSvc4-specific antibody showed that the NSvc4 protein accumulated in walls of RSV-infected leaf cells. Gel retardation assays revealed that the NSvc4 protein interacts with single-stranded RNA in vitro, a common feature of many reported plant viral movement proteins (MPs). RSV NSvc4 failed to interact with the RSV nucleocapsid protein using yeast two-hybrid assays. Taken together, our data indicate that RSV NSvc4 is likely an MP of the virus. This is the first report describing a tenuivirus MP. 相似文献
135.
136.
137.
Antiviral flavonoids from the root bark of Morus alba L 总被引:7,自引:0,他引:7
A prenylated flavonoid, moralbanone, along with seven known compounds kuwanon S, mulberroside C, cyclomorusin, eudraflavone B hydroperoxide, oxydihydromorusin, leachianone G and alpha-acetyl-amyrin were isolated from the root bark of Morus alba L. Leachianone G showed potent antiviral activity (IC(50) = 1.6 microg/ml), whereas mulberroside C showed weak activity (IC(50) = 75.4 microg/ml) against herpes simplex type 1 virus (HSV-1). Their structures were elucidated by spectroscopic methods. 相似文献
138.
Cryptochrome blue light photoreceptors share sequence similarity to photolyases, flavoproteins that mediate light-dependent DNA repair. However, cryptochromes lack photolyase activity and are characterized by distinguishing C-terminal domains. Here we show that the signaling mechanism of Arabidopsis cryptochrome is mediated through the C terminus. On fusion with beta-glucuronidase (GUS), both the Arabidopsis CRY1 C-terminal domain (CCT1) and the CRY2 C-terminal domain (CCT2) mediate a constitutive light response. This constitutive photomorphogenic (COP) phenotype was not observed for mutants of cct1 corresponding to previously described cry1 alleles. We propose that the C-terminal domain of Arabidopsis cryptochrome is maintained in an inactive state in the dark. Irradiation with blue light relieves this repression, presumably through an intra- or intermolecular redox reaction mediated through the flavin bound to the N-terminal photolyase-like domain. 相似文献
139.
140.