全文获取类型
收费全文 | 3000篇 |
免费 | 195篇 |
出版年
2022年 | 25篇 |
2021年 | 29篇 |
2020年 | 22篇 |
2019年 | 39篇 |
2018年 | 42篇 |
2017年 | 45篇 |
2016年 | 59篇 |
2015年 | 102篇 |
2014年 | 106篇 |
2013年 | 167篇 |
2012年 | 220篇 |
2011年 | 187篇 |
2010年 | 137篇 |
2009年 | 121篇 |
2008年 | 216篇 |
2007年 | 234篇 |
2006年 | 204篇 |
2005年 | 185篇 |
2004年 | 189篇 |
2003年 | 188篇 |
2002年 | 188篇 |
2001年 | 41篇 |
2000年 | 41篇 |
1999年 | 31篇 |
1998年 | 31篇 |
1997年 | 21篇 |
1996年 | 30篇 |
1995年 | 29篇 |
1994年 | 27篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 17篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1971年 | 4篇 |
排序方式: 共有3195条查询结果,搜索用时 31 毫秒
941.
942.
Latitudinal gradient of species diversity: multi-scale variability in rocky intertidal sessile assemblages along the Northwestern Pacific coast 总被引:2,自引:0,他引:2
Takehiro Okuda Takashi Noda Tomoko Yamamoto Norihiko Ito Masahiro Nakaoka 《Population Ecology》2004,46(2):159-170
This study examined the latitudinal gradient of species diversity of rocky intertidal sessile assemblages on the slopes of rocks along the Northwestern Pacific coast of Japan, located between 31°N and 43°N, by explicitly incorporating an hierarchical spatial scale into the monitoring design. The specific questions were to examine: (1) whether there is a latitudinal gradient of regional diversity, (2) how spatial components of the regional diversity (local diversity and turnover diversity) vary with latitude depending on spatial scale, and (3) whether the latitudinal gradient differs between different measures of species diversity, i.e. species richness and Simpsons diversity index. We measured coverage and the presence or absence of all sessile organisms in a total of 150 census plots established at five shores in each of six regions. The results showed that there were clear latitudinal gradients in regional species richness and in species turnover among shores. However, these patterns were not reflected in smaller-scale local species richness. For Simpsons diversity index, there was no evidence of latitudinal clines either in regional diversity or in spatial components. These results suggest that relative abundance of common species does not vary along latitude, while the number of rare species increases with decreasing latitude.
An erratum to this article can be found at 相似文献
An erratum to this article can be found at 相似文献
943.
944.
Identification of the Tslc1 gene,a mouse orthologue of the human tumor suppressor TSLC1 gene 总被引:3,自引:0,他引:3
Fukami T Satoh H Fujita E Maruyama T Fukuhara H Kuramochi M Takamoto S Momoi T Murakami Y 《Gene》2002,295(1):7-12
We have recently identified the TSLC1 gene as a novel tumor suppressor in human non-small lung cancer on chromosome 11q23.2. TSLC1 encodes a membrane glycoprotein showing significant homology with immunoglobulin superfamily molecules. Here, we report the isolation of a mouse orthologous gene, Tslc1. The Tslc1 cDNA contains a single open reading frame of 1335 bp encoding a putative protein of 445 amino acids, and its expression was detected in all tissues examined. The Tslc1 gene is mapped on mouse chromosome 9, a synteny of human chromosome 11q, and is composed of ten exons, the exon-intron junctions being highly conserved between human and mouse. The predicted amino acids of mouse Tslc1 display 98% identity with that of human TSLC1. Furthermore, data base analysis indicates that the amino acid sequences corresponding to the cytoplasmic domain of Tslc1 are identical in five mammals and highly conserved in vertebrates, suggesting an important role of Tslc1 in normal cell-cell interaction. 相似文献
945.
Sato N Uragami Y Nishizaki T Takahashi Y Sazaki G Sugimoto K Nonaka T Masai E Fukuda M Senda T 《Journal of molecular biology》2002,321(4):621-636
BphC derived from Pseudomonas sp. strain KKS102 is an extradiol-cleaving catecholic dioxygenase. This enzyme contains a non-heme iron atom and plays an important role in degrading biphenyl/polychlorinated biphenyls (PCBs) in the microbe. To elucidate detailed structures of BphC reaction intermediates, crystal structures of the substrate-free form, the BphC-substrate complex, and the BphC-substrate-NO (nitric oxide) complex were determined. These crystal structures revealed (1) the binding site of the O(2) molecule in the coordination sphere and (2) conformational changes of His194 during the catalytic reaction. On the basis of these findings, we propose a catalytic mechanism for the extradiol-cleaving catecholic dioxygenase in which His194 seems to play three distinct roles. At the early stage of the catalytic reaction, His194 appears to act as a catalytic base, which likely deprotonates the hydroxyl group of the substrate. At the next stage, the protonated His194 seems to stabilize a negative charge on the O2 molecule located in the hydrophobic O2-binding cavity. Finally, protonated His194 seems to function as a proton donor, whose existence has been proposed. 相似文献
946.
Salmonella type III secretion-associated protein InvE controls translocation of effector proteins into host cells
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Salmonella enterica encodes a type III secretion system (TTSS) within a pathogenicity island located at centisome 63 (SPI-1), which is essential for its pathogenicity. This system mediates the transfer of a battery of bacterial proteins into the host cell with the capacity to modulate cellular functions. The transfer process is dependent on the function of protein translocases SipB, SipC, and SipD. We report here that Salmonella protein InvE, which is also encoded within SPI-1, is essential for the translocation of bacterial proteins into host cells. An S. enterica serovar Typhimurium mutant carrying a loss-of-function mutation in invE shows reduced secretion of SipB, SipC, and SipD while exhibiting increased secretion of other TTSS effector proteins. We also demonstrate that InvE interacts with a protein complex formed by SipB, SipC, and their cognate chaperone, SicA. We propose that InvE controls protein translocation by regulating the function of the Sip protein translocases. 相似文献
947.
The ClpXP ATP-Dependent Protease Regulates Flagellum Synthesis in Salmonella enterica Serovar Typhimurium 总被引:6,自引:0,他引:6
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
948.
Nishioka T Sakumi K Miura T Tahara K Horie H Kadoya T Nakabeppu Y 《Journal of biochemistry》2002,131(5):653-661
In this study, we established rat 3Y1 embryo cell lines expressing FosB and DeltaFosB as fusion proteins (ER-FosB, ER-DeltaFosB) with the ligand-binding domain of human estrogen receptor (ER). The binding of estrogen to the fusion proteins resulted in their nuclear translocation. After estrogen administration, exponentially growing cells expressing ER-DeltaFosB, and to a lesser extent ER-FosB, underwent morphological alteration from the flat fibroblastic shape to an extended bipolar shape, and ceased proliferating. Such morphological alteration was also induced in quiescent cells expressing ER-DeltaFosB and ER-FosB after one round of cell division triggered by estrogen administration. The cells expressing ER-DeltaFosB changed shape frequently, and the content of F-actin in the cytoplasm detected by binding of Alexa 488-phalloidin significantly decreased after the morphological alteration. By two-dimensional gel electrophoresis analysis of cellular proteins from the cells expressing ER-DeltaFosB, we identified several proteins whose expression either increased or decreased after estrogen administration. Two of these proteins were identified from their amino acid sequences as novel processed form of galectin-1. 相似文献
949.
To overcome obstacles to target site selection, we recently created a novel hybrid ribozyme that could access any chosen site by the recruitment of intracellular RNA helicases [Warashina et al. (2001) Proc. Natl. Acad. Sci. USA 98, 5572-5577; Kawasaki et al. (2002) Nat. Biotech. 20, 376-380]. We also demonstrated previously that pol III-driven maxizymes with two substrate-binding arms that were directed against two different sites within a target mRNA formed very active heterodimers in vivo [Kuwabara, et al. (2000) Trends Biotechnol. 18, 462-468; Tanabe et al. (2001) Nature 406, 473-474]. Despite the complicated dimerization process, all the maxizymes that we tested in cultured cells had greater catalytic activity than the parental ribozymes. To investigate the action of maxizymes in cells, we designed a specific maxizyme with two substrate-binding arms that was directed against endogenously expressed LTR-luciferase chimeric mRNA, where LTR refers to the long terminal repeat of HIV-1. One substrate-binding arm of the maxizyme was designed to bind to a site within HIV-1 TAR RNA that is known to form a stable stem structure that normally prevents binding of a ribozyme. The other substrate-binding arm was directed against a relatively accessible site within the luciferase gene. As expected, the conventional ribozyme failed to cleave the TAR region in vivo because of the latter's stable secondary structure. However, to our surprise, the maxizyme cleaved the TAR region within the stem with high efficiency in vivo. The enhanced cleavage in vivo by the maxizyme might have resulted from an entropically favorable, intramolecular, second binding process that occurred during the breathing of the stem structure of the target mRNA. Importantly, our data suggest that this maxizyme technology might be used as an alternative approach to the recruitment of RNA helicases in cleaving sites previously found to be inaccessible. 相似文献
950.
An abnormal handling of renal magnesium has been suggested to cause salt-sensitive hypertension. The filtered magnesium is first reabsorbed in the proximal tubule. Amiloride has been shown to enhance renal magnesium conservation, but the regulatory mechanisms are unknown yet. High-salt (8% NaCl) diet decreased serum magnesium concentration, while increased urinary magnesium in Dahl salt-sensitive (DS) rat. Furthermore, the expression of nitric oxide synthase type 3 and nitric oxide (NO) content were decreased in high-salt loaded DS rat. In isolated proximal tubule cells, amiloride (0.1 mM) increased intracellular free magnesium concentration ([Mg(2+)](i)). However, the net [Mg(2+)](i) increase in the high-salt loaded DS rat was smaller than other groups. NOR1 (0.1 mM), a NO donor, restored the increase of [Mg(2+)](i) to the same level of other groups. On the contrary, L-NMMA (0.1 mM), an inhibitor of NO production, inhibited the increase of [Mg(2+)](i) in all groups. These results suggest that intracellular NO has an important role to up-regulate amiloride-elicited magnesium influx. 相似文献