全文获取类型
收费全文 | 2851篇 |
免费 | 185篇 |
国内免费 | 1篇 |
专业分类
3037篇 |
出版年
2022年 | 12篇 |
2021年 | 38篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 40篇 |
2017年 | 28篇 |
2016年 | 46篇 |
2015年 | 90篇 |
2014年 | 101篇 |
2013年 | 134篇 |
2012年 | 155篇 |
2011年 | 174篇 |
2010年 | 100篇 |
2009年 | 102篇 |
2008年 | 147篇 |
2007年 | 163篇 |
2006年 | 147篇 |
2005年 | 147篇 |
2004年 | 142篇 |
2003年 | 142篇 |
2002年 | 128篇 |
2001年 | 106篇 |
2000年 | 86篇 |
1999年 | 72篇 |
1998年 | 25篇 |
1997年 | 28篇 |
1996年 | 28篇 |
1995年 | 18篇 |
1994年 | 14篇 |
1993年 | 19篇 |
1992年 | 61篇 |
1991年 | 41篇 |
1990年 | 35篇 |
1989年 | 41篇 |
1988年 | 31篇 |
1987年 | 39篇 |
1986年 | 34篇 |
1985年 | 49篇 |
1984年 | 30篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 24篇 |
1978年 | 10篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 12篇 |
1972年 | 13篇 |
1971年 | 11篇 |
排序方式: 共有3037条查询结果,搜索用时 15 毫秒
111.
Huang XP Kagami N Inoue H Kojima M Kimura T Makabe O Suzuki K Takahashi K 《The Journal of biological chemistry》2000,275(34):26607-26614
Aspergillopepsin II from Aspergillus niger var. macrosporus is a non-pepsin type or pepstatin-insensitive acid proteinase. To identify the catalytic residues of the enzyme, all acidic residues that are conserved in the homologous proteinases of family A4 were replaced with Asn, Gln, or Ala using site-directed mutagenesis. The wild-type and mutant pro-enzymes were heterologously expressed in Escherichia coli and refolded in vitro. The wild-type pro-enzyme was shown to be processed into a two-chain active enzyme under acidic conditions. Most of the recombinant mutant pro-enzymes showed significant activity under acidic conditions because of autocatalytic activation except for the D123N, D123A, E219Q, and E219A mutants. The D123A, E219Q, and E219A mutants showed neither enzymatic activity nor autoprocessing activity under acidic conditions. The circular dichroism spectra of the mutant pro- and mature enzymes were essentially the same as those of the wild-type pro- and mature enzyme, respectively, indicating that the mutant pro-enzymes were correctly folded. In addition, two single and one double mutant pro-enzyme, D123E, E219D, and D123E/E219D, did not show enzymatic activity under acidic conditions. Taken together, Glu-219 and Asp-123 are deduced to be the catalytic residues of aspergillopepsin II. 相似文献
112.
113.
Kazuyuki Nakamura Hirofumi Kodera Tenpei Akita Masaaki Shiina Mitsuhiro Kato Hideki Hoshino Hiroshi Terashima Hitoshi Osaka Shinichi Nakamura Jun Tohyama Tatsuro Kumada Tomonori Furukawa Satomi Iwata Takashi Shiihara Masaya Kubota Satoko Miyatake Eriko Koshimizu Kiyomi Nishiyama Mitsuko Nakashima Yoshinori Tsurusaki Noriko Miyake Kiyoshi Hayasaka Kazuhiro Ogata Atsuo Fukuda Naomichi Matsumoto Hirotomo Saitsu 《American journal of human genetics》2013
114.
Masashi Kato Mayuko Y. Kumasaka Shoko Ohnuma Akio Furuta Yoko Kato Hossain U. Shekhar Michiyo Kojima Yasuko Koike Nguyen Dinh Thang Nobutaka Ohgami Thuy Bich Ly Xiaofang Jia Husna Yetti Hisao Naito Gaku Ichihara Ichiro Yajima 《PloS one》2013,8(6)
Health risk for well drinking water is a worldwide problem. Our recent studies showed increased toxicity by exposure to barium alone (≤700 µg/L) and coexposure to barium (137 µg/L) and arsenic (225 µg/L). The present edition of WHO health-based guidelines for drinking water revised in 2011 has maintained the values of arsenic (10 µg/L) and barium (700 µg/L), but not elements such as manganese, iron and zinc. Nevertheless, there have been very few studies on barium in drinking water and human samples. This study showed significant correlations between levels of arsenic and barium, but not its homologous elements (magnesium, calcium and strontium), in urine, toenail and hair samples obtained from residents of Jessore, Bangladesh. Significant correlation between levels of arsenic and barium in well drinking water and levels in human urine, toenail and hair samples were also observed. Based on these results, a high-performance and low-cost adsorbent composed of a hydrotalcite-like compound for barium and arsenic was developed. The adsorbent reduced levels of barium and arsenic from well water in Bangladesh and Vietnam to <7 µg/L within 1 min. Thus, we have showed levels of arsenic and barium in humans and propose a novel remediation system. 相似文献
115.
116.
117.
Porcine polymorphonuclear leukocyte NADPH-cytochrome c reductase generates superoxide in the presence of cytochrome b559 and phospholipid 总被引:1,自引:0,他引:1
F Sakane H Kojima K Takahashi J Koyama 《Biochemical and biophysical research communications》1987,147(1):71-77
NADPH-cytochrome c reductase and cytochrome b559 were purified from the membrane fraction of phorbol myristate acetate-stimulated porcine polymorphonuclear leukocytes. The highly purified reductase oxidized NADPH and generated superoxide when combined with partially purified cytochrome b559 in the presence of phosphatidylcholine. In the same system, but under the anaerobic condition, the reductase was found to reduce cytochrome b559. 相似文献
118.
The common yellow butterfly Eurema hecabe is widely distributed in East Asia, and is one of the most burdensome species for taxonomists due to the numerous geographic
and seasonal wing colour patterns. Moreover, within this species, individuals with a yellow wing fringe that occur in temperate
regions of Japan (Y type) proved to be biologically different from others that occur widely in subtropical regions of Japan
and all over East Asia (B type). To unveil the genetic variation within and between the two types, a total of 50 butterflies
collected at 18 geographic localities in East Asia were examined for nucleotide sequence variation of three mitochondrial
regions: cytochrome c oxidase subunit I (COI), cytochrome c oxidase subunit III (COIII) and NADH dehydrogenase subunit 5 (ND5). In addition, they were also examined for infection status
with the endosymbiotic bacteria Wolbachia. The three mitochondrial sequences consistently showed that (i) Y type and B type were highly divergent, (ii) nucleotide
variation within B type was very small although sampled from a geographically wide range, and (iii) a weak association existed
between mitochondrial DNA haplotypes and Wolbachia infection status. 相似文献
119.
Taiji Kawakatsu Graziana Taramino Jun-Ichi Itoh Justin Allen Yutaka Sato Soon-Kwan Hong Ryan Yule Nobuhiro Nagasawa Mikiko Kojima Makoto Kusaba Hitoshi Sakakibara Hajime Sakai Yasuo Nagato 《The Plant journal : for cell and molecular biology》2009,58(6):1028-1040
Most aerial parts of the plant body are products of the continuous activity of the shoot apical meristem (SAM). Leaves are the major component of the aerial plant body, and their temporal and spatial distribution mainly determines shoot architecture. Here we report the identification of the rice gene PLASTOCHRON3 ( PLA3 )/ GOLIATH ( GO ) that regulates various developmental processes including the rate of leaf initiation (the plastochron). PLA3 / GO encodes a glutamate carboxypeptidase, which is thought to catabolize small acidic peptides and produce small signaling molecules. pla3 exhibits similar phenotypes to pla1 and pla2 – a shortened plastochron, precocious leaf maturation and rachis branch-to-shoot conversion in the reproductive phase. However, in contrast to pla1 and pla2 , pla3 showed pleiotropic phenotypes including enlarged embryo, seed vivipary, defects in SAM maintenance and aberrant leaf morphology. Consistent with these pleiotropic phenotypes, PLA3 is expressed in the whole plant body, and is involved in plant hormone homeostasis. Double mutant analysis revealed that PLA1 , PLA2 and PLA3 are regulated independently but function redundantly. Our results suggest that PLA3 modulates various signaling pathways associated with a number of developmental processes. 相似文献
120.
Efficient apoptotic cell engulfment is important for both tissue homeostasis and immune response in mammals. In the present study, we report that Beclin 1 (a regulator of autophagy) is required for apoptotic cell engulfment. The engulfment process was largely abolished in Beclin 1 knock-out cells, and Beclin 1 knockdown significantly decreased apoptotic cell internalization in macrophage and fibroblast cell lines. Beclin 1 was recruited to the early phagocytic cup along with the generation of phosphatidylinositol 3-phosphate and Rac1, which regulates actin dynamics in lamellipodia. No lamellipodia were formed in Beclin 1 knock-out cells, and Beclin 1 knockdown completely inhibited the promotion of engulfment by ectopic expression of Rac1. Beclin 1 was co-immunoprecipitated with Rac1. These data indicate that Beclin 1 coordinates actin dynamics and membrane phospholipid synthesis to promote efficient apoptotic cell engulfment. 相似文献