全文获取类型
收费全文 | 3088篇 |
免费 | 185篇 |
专业分类
3273篇 |
出版年
2022年 | 11篇 |
2021年 | 23篇 |
2020年 | 18篇 |
2019年 | 31篇 |
2018年 | 39篇 |
2017年 | 31篇 |
2016年 | 55篇 |
2015年 | 78篇 |
2014年 | 81篇 |
2013年 | 275篇 |
2012年 | 189篇 |
2011年 | 195篇 |
2010年 | 100篇 |
2009年 | 122篇 |
2008年 | 171篇 |
2007年 | 160篇 |
2006年 | 164篇 |
2005年 | 160篇 |
2004年 | 168篇 |
2003年 | 171篇 |
2002年 | 167篇 |
2001年 | 51篇 |
2000年 | 58篇 |
1999年 | 47篇 |
1998年 | 44篇 |
1997年 | 38篇 |
1996年 | 41篇 |
1995年 | 40篇 |
1994年 | 33篇 |
1993年 | 35篇 |
1992年 | 48篇 |
1991年 | 41篇 |
1990年 | 21篇 |
1989年 | 41篇 |
1988年 | 24篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1985年 | 17篇 |
1984年 | 25篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 28篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1973年 | 11篇 |
1971年 | 9篇 |
1969年 | 12篇 |
1966年 | 9篇 |
排序方式: 共有3273条查询结果,搜索用时 15 毫秒
891.
Oncostatin M (OSM), which is predominantly expressed in bone marrow, is a member of the interleukin-6 family of cytokines, and appears to play important roles in hematopoiesis and the development of the liver. Recently, specific beta subunit of OSM receptor (OSMRbeta) was isolated from LO cells originated from aorta-gonad-mesonephros (AGM) region. In this study, we performed in situ hybridization to explore the expression pattern of OSMRbeta during murine embryogenesis, postnatal development, and in adult tissues. At 11.5 days postcoitum (dpc), the expression of OSMRbeta was first detected in aortic endothelial cells of the AGM region. At 14.5dpc, its gene expression was clearly observed in the primordia of some organs, including liver, thymus, choroid plexus, and limb, and persisted into postnatal mice. After birth, its gene expression became detectable in the other organs, such as lymph node, bone, heart, kidney, small intestine, nasal cavity, and lung. 相似文献
892.
Xudong Chen Tsuyoshi Fujita Satoshi Ohnishi Minoru Fujii Yong Geng 《Journal of Industrial Ecology》2012,16(1):129-141
Innovative waste recycling through industrial processes such as industrial and urban symbiosis has long been practiced and recently received much attention in the field of industrial ecology, with researchers making efforts to identify key contributing factors to successful industrial symbiosis. By analyzing 88 sample recycling projects in 23 eco‐towns in Japan, this article focuses on the factors of project scale, recycling boundary, and types of waste in relationship to environmental benefits and operational performance. The results showed that larger eco‐towns achieved more savings of virgin materials and higher stability in operation. Large‐scale projects tended to locate closer to the users of recycled products than did small‐scale projects. For treating similar types of waste, projects producing recycled products for special users (e.g., feedstock to a blast furnace for iron production) tended to locate closer to the users than those not producing for special users. The type of waste had a strong effect on the savings of virgin materials and recycling boundaries, while local factors had significant impacts on operational performance. The results also showed that agglomeration did not significantly contribute to the environmental benefits or operational performance of eco‐town projects. Another finding was that national agencies were helpful for facilitating cross‐prefecture transportation and long‐distance transaction of wastes. Implications of the findings are also discussed. 相似文献
893.
Koichiro Ichimura Ekaterina Bubenshchikova Rebecca Powell Yayoi Fukuyo Tomomi Nakamura Uyen Tran Shoji Oda Minoru Tanaka Oliver Wessely Hidetake Kurihara Tatsuo Sakai Tomoko Obara 《PloS one》2012,7(9)
The glomerulus of the vertebrate kidney links the vasculature to the excretory system and produces the primary urine. It is a component of every single nephron in the complex mammalian metanephros and also in the primitive pronephros of fish and amphibian larvae. This systematic work highlights the benefits of using teleost models to understand the pronephric glomerulus development. The morphological processes forming the pronephric glomerulus are astoundingly different between medaka and zebrafish. (1) The glomerular primordium of medaka - unlike the one of zebrafish - exhibits a C-shaped epithelial layer. (2) The C-shaped primordium contains a characteristic balloon-like capillary, which is subsequently divided into several smaller capillaries. (3) In zebrafish, the bilateral pair of pronephric glomeruli is fused at the midline to form a glomerulus, while in medaka the two parts remain unmerged due to the interposition of the interglomerular mesangium. (4) Throughout pronephric development the interglomerular mesangial cells exhibit numerous cytoplasmic granules, which are reminiscent of renin-producing (juxtaglomerular) cells in the mammalian afferent arterioles. Our systematic analysis of medaka and zebrafish demonstrates that in fish, the morphogenesis of the pronephric glomerulus is not stereotypical. These differences need be taken into account in future analyses of medaka mutants with glomerulus defects. 相似文献
894.
Sato Y Morita R Katsuma S Nishimura M Tanaka A Kusaba M 《The Plant journal : for cell and molecular biology》2009,57(1):120-131
Yellowing, which is related to the degradation of chlorophyll and chlorophyll–protein complexes, is a notable phenomenon during leaf senescence. NON-YELLOW COLORING1 ( NYC1 ) in rice encodes a membrane-localized short-chain dehydrogenase/reductase (SDR) that is thought to represent a chlorophyll b reductase necessary for catalyzing the first step of chlorophyll b degradation. Analysis of the nyc1 mutant, which shows the stay-green phenotype, revealed that chlorophyll b degradation is required for the degradation of light-harvesting complex II and thylakoid grana in leaf senescence. Phylogenetic analysis further revealed the existence of NYC1-LIKE (NOL) as the most closely related protein to NYC1. In the present paper, the nol mutant in rice was also found to show a stay-green phenotype very similar to that of the nyc1 mutant, i.e. the degradation of chlorophyll b was severely inhibited and light-harvesting complex II was selectively retained during senescence, resulting in the retention of thylakoid grana even at a late stage of senescence. The nyc1 nol double mutant did not show prominent enhancement of inhibition of chlorophyll degradation. NOL was localized on the stromal side of the thylakoid membrane despite the lack of a transmembrane domain. Immunoprecipitation analysis revealed that NOL and NYC1 interact physically in vitro . These observations suggest that NOL and NYC1 are co-localized in the thylakoid membrane and act in the form of a complex as a chlorophyll b reductase in rice. 相似文献
895.
896.
Hiroyuki Takamatsu Yoshie Tani Mitoshi Akiyama Yoshihiro Nakata Tomio Segawa 《Journal of neurochemistry》1991,56(4):1452-1454
The characteristics of the carbohydrate chain on the rat cerebral cortical substance P (SP) receptor were studied. We examined the effects of pretreatment with three lectins (concanavalin A, wheat germ agglutinin, lens culinaris agglutinin) on the [3H]SP binding activities. Each lectin can bind to the specific carbohydrate chain. Among these lectins, only concanavalin A inhibited specific [3H]SP binding by reducing the affinity of the binding sites. The inhibitory action of concanavalin A was dose-dependent and diminished by the addition of alpha-methyl-D-mannoside. The present results suggest that the rat cortical SP receptor has either a biantennary complex-type or a high mannose-type of carbohydrate chain, and that the carbohydrate chain is implicated in the SP binding activity of the SP receptor system. 相似文献
897.
898.
Keiko Taguchi Ikuo Hirano Tohru Itoh Minoru Tanaka Atsushi Miyajima Akira Suzuki Hozumi Motohashi Masayuki Yamamoto 《Molecular and cellular biology》2014,34(5):900-913
Keap1-Nrf2 system plays a central role in the stress response. While Keap1 ubiquitinates Nrf2 for degradation under unstressed conditions, this Keap1 activity is abrogated in response to oxidative or electrophilic stresses, leading to Nrf2 stabilization and coordinated activation of cytoprotective genes. We recently found that nuclear accumulation of Nrf2 is significantly increased by simultaneous deletion of Pten and Keap1, resulting in the stronger activation of Nrf2 target genes. To clarify the impact of the cross talk between the Keap1-Nrf2 and Pten–phosphatidylinositide 3-kinase–Akt pathways on the liver pathophysiology, in this study we have conducted closer analysis of liver-specific Pten::Keap1 double-mutant mice (Pten::Keap1-Alb mice). The Pten::Keap1-Alb mice were lethal by 1 month after birth and displayed severe hepatomegaly with abnormal expansion of ductal structures comprising cholangiocytes in a Nrf2-dependent manner. Long-term observation of Pten::Keap1-Alb::Nrf2+/− mice revealed that the Nrf2-heterozygous mice survived beyond 1 month but developed polycystic liver fibrosis by 6 months. Gsk3 directing the Keap1-independent degradation of Nrf2 was heavily phosphorylated and consequently inactivated by the double deletion of Pten and Keap1 genes. Thus, liver-specific disruption of Keap1 and Pten augments Nrf2 activity through inactivation of Keap1-dependent and -independent degradation of Nrf2 and establishes the Nrf2-dependent molecular network promoting the hepatomegaly and cholangiocyte expansion. 相似文献
899.
Muta Naoki Umezawa Yu Yamaguchi Akira Suzaki Hirokazu Wada Minoru Nakata Hideaki Kawamoto Kazuaki Matsuoka Kazumi 《Limnology》2020,21(3):341-356
Limnology - In the seasonally hypoxic semi-enclosed Omura Bay, Japan, regression equations estimating year-round nutrient [NO3 + NO2, NH4, PO4, Si(OH)4] concentrations in pore water... 相似文献
900.
Tadahiko Kajiwara Akikazu Hatanaka Yuzo Inouye Minoru Ohno 《Bioscience, biotechnology, and biochemistry》2013,77(3):409-413
The diethylamine-catalyzed aldol condensation of E-2-hexenal yielded a mixture of 2-E,4-E,6-E- (IV-a) and 2-E,4-Z,6-E-4-ethyldeca-2,4,6-triene-1-al (IV-b). Structual and geometrical elucidation of both alcohols were made by means of spectral evidence as well as by the catalytic hydrogenation leading to the same 4-ethyldecanol (VI). The “b-peak substance” detected in the leaf alcohol reaction products was proved to be identical with 4-ethyldecanol (VI). The treatment of the trienal containing the central Z-double bond with sodium under the leaf alcohol reaction condition failed to afford ethyl-propyl-benzyl alcohol, but gave 4-ethyldecanol (VI). This result safely excludes the operation of the previously suspected valence tautomerism (Cope rearrangement) in the leaf alcohol reaction, and accounts for the pathway of the formation of (VI). 相似文献