全文获取类型
收费全文 | 2385篇 |
免费 | 111篇 |
专业分类
2496篇 |
出版年
2021年 | 13篇 |
2020年 | 15篇 |
2019年 | 27篇 |
2018年 | 30篇 |
2017年 | 22篇 |
2016年 | 38篇 |
2015年 | 56篇 |
2014年 | 59篇 |
2013年 | 250篇 |
2012年 | 156篇 |
2011年 | 156篇 |
2010年 | 82篇 |
2009年 | 106篇 |
2008年 | 148篇 |
2007年 | 129篇 |
2006年 | 135篇 |
2005年 | 130篇 |
2004年 | 146篇 |
2003年 | 142篇 |
2002年 | 134篇 |
2001年 | 22篇 |
2000年 | 26篇 |
1999年 | 27篇 |
1998年 | 29篇 |
1997年 | 33篇 |
1996年 | 27篇 |
1995年 | 32篇 |
1994年 | 30篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 13篇 |
1990年 | 8篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 23篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1966年 | 5篇 |
排序方式: 共有2496条查询结果,搜索用时 15 毫秒
31.
32.
Takashi Kajitani Mimi Tamamori-Adachi Hiroko Okinaga Minoru Chikamori Masayoshi Iizuka Tomoki Okazaki 《Biochemical and biophysical research communications》2011,(3):375
Elevated parathyroid hormone-related protein (PTHrP) is responsible for humoral hypercalcemia of malignancy (HHM), which is of clinical significance in treatment of terminal patients with malignancies. Steroid hormones were known to cause suppression of PTHrP expression. However, detailed studies linking multiple steroid hormones to PTHrP expression are lacking. Here we studied PTHrP expression in response to steroid hormones in four cell lines with excessive PTHrP production. Our study established that steroid hormones negatively regulate PTHrP expression. Vitamin D receptor, estrogen receptor α, glucocorticoid receptor, and progesterone receptor, were required for repression of PTHrP expression by the cognate ligands. A notable exception was the androgen receptor, which was dispensable for suppression of PTHrP expression in androgen-treated cells. We propose a pathway(s) involving nuclear receptors to suppress PTHrP expression. 相似文献
33.
Zhipeng Wang Yuhei Nishimura Yasuhito Shimada Noriko Umemoto Minoru Hirano Liqing Zang Takehiko Oka Chikara Sakamoto Junya Kuroyanagi Toshio Tanaka 《Gene》2009
Beta adrenergic receptors (β-ARs) are members of the G-protein-coupled receptor superfamily and mediate various physiological processes in many species. The expression patterns and functions of β-ARs in zebrafish are, however, largely unknown. We have identified zebrafish β-AR orthologs, which we have designated as adrb1, adrb2a, adrb2b, adrb3a and adrb3b. adrb1 was found to be expressed in the heart and brain. Expression of adrb2a predominated in the brain and skin, whereas adrb2b was found to be highly expressed in muscle, pancreas and liver. Both adrb3a and adrb3b were exclusively expressed in blood. Knock-down of these β-ARs by morpholino oligonucleotides revealed a functional importance of adrb2a in pigmentation. Expression of atp5a1 and atp5b, genes that encode subunits of F1F0-ATPase, which is known to be involved in pigmentation, was significantly increased by knock-down of adrb2a. Our data suggest that adrb2a may regulate pigmentation, partly by modulating F1F0-ATPase. 相似文献
34.
Identification of the mouse H-ficolin gene as a pseudogene and orthology between mouse ficolins A/B and human L-/M-ficolins 总被引:8,自引:0,他引:8
Ficolin is a collagenous lectin which plays a crucial role in innate immunity. Three and two ficolins have been identified in human and mice, respectively. To identify the mouse homologue of human H-ficolin and to elucidate the orthology between mouse ficolins A/B and human L-/M-ficolins, the gene structures were explored. The mouse homologue of the H-ficolin gene was identified as a pseudogene on chromosome 4. The mouse ficolin A gene was located far from the ficolin B gene on chromosome 2, whereas the human L-ficolin and M-ficolin genes were close in the region homologous to the ficolin B locus. Together with the exon-intron structures and the phylogenetic tree, these results suggest that ficolin B is the mouse orthologue of M-ficolin and that the genes encoding serum-type ficolins, ficolin A and L-ficolin, were generated independently from the ficolin B/M-ficolin lineage each in mice and primates. 相似文献
35.
Design of a New Energy‐Harvesting Electrochromic Window Based on an Organic Polymeric Dye,a Cobalt Couple,and PProDOT‐Me2 下载免费PDF全文
A new design for an energy‐harvesting electrochromic window (EH‐ECW) based on the fusion of two technologies, organic electrochromic windows and dye‐sensitized solar cells (DSSCs), is presented. Unlike other power‐generating smart windows, such as photoelectrochromic devices that are passive and only contain two states (i.e., a closed‐circuit colored state and an open‐circuit bleaching state), EH‐ECW allows active tuning of the transmittance by varying the applied potential and it functions as a photovoltaic cell based on a DSSC. The resulting device demonstrates a fast switching rate of 1 s in both the bleaching and coloring processes through the use of an electrochromic polymer as a counter electrode layer. To increase the transmittance of the device, a cobalt redox couple and a light‐colored, yet efficient, organic dye are used. The organic dye contains a polymeric structure that contributes to the high cyclic stability. The device exhibits a power conversion efficiency (PCE) of 4.5% (100 mW cm‐2) under AM 1.5 irradiation, a change in transmittance of 34% upon applied potential, and shows only 3% degradation in the PCE after 5000 cycles. 相似文献
36.
Aoki KF Ueda N Yamaguchi A Kanehisa M Akutsu T Mamitsuka H 《Bioinformatics (Oxford, England)》2004,20(Z1):i6-14
MOTIVATION: The study of carbohydrate sugar chains, or glycans, has been one of slow progress mainly due to the difficulty in establishing standard methods for analyzing their structures and biosynthesis. Glycans are generally tree structures that are more complex than linear DNA or protein sequences, and evidence shows that patterns in glycans may be present that spread across siblings and into further regions that are not limited by the edges in the actual tree structure itself. Current models were not able to capture such patterns. RESULTS: We have applied a new probabilistic model, called probabilistic sibling-dependent tree Markov model (PSTMM), which is able to inherently capture such complex patterns of glycans. Not only is the ability to capture such patterns important in itself, but this also implies that PSTMM is capable of performing multiple tree structure alignments efficiently. We prove through experimentation on actual glycan data that this new model is extremely useful for gaining insight into the hidden, complex patterns of glycans, which are so crucial for the development and functioning of higher level organisms. Furthermore, we also show that this model can be additionally utilized as an innovative approach to multiple tree alignment, which has not been applied to glycan chains before. This extension on the usage of PSTMM may be a major step forward for not only the structural analysis of glycans, but it may consequently prove useful for discovering clues into their function. 相似文献
37.
Matsuda K Miura T Kaiya H Maruyama K Shimakura S Uchiyama M Kangawa K Shioda S 《Peptides》2006,27(9):2321-2325
Our recent research has indicated that intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) administration of n-octanoic acid-modified ghrelin (acyl ghrelin) stimulates food intake and locomotor activity in the goldfish. The manner in which peripherally administered acyl ghrelin regulates food intake, however, remains unclear. In contrast to acyl ghrelin, non-acylated ghrelin (des-acyl ghrelin) does not exert an orexigenic action or induce hypermotility. To this extent, the biological role of des-acyl ghrelin in fish is unknown. Given the possible involvement of afferent pathways in mediating the effects of acyl ghrelin, as is known to occur in rodents, we examined the effect of capsaicin, a neurotoxin which destroys primary sensory (vagal and splanchnic) afferents, on the orexigenic activity induced by i.p.-injected acyl ghrelin. Pretreatment with i.p.-injected capsaicin (0.16 micromol/g body weight (BW)) cancelled the orexigenic action of i.p.-injected acyl ghrelin (8 pmol/g BW), although i.p.-injected capsaicin alone did not affect food intake. The effect of des-acyl ghrelin on the orexigenic action of acyl ghrelin in the goldfish was also investigated. The i.c.v. and i.p. injection of des-acyl ghrelin at doses 3-10 times higher than that of acyl ghrelin suppressed the orexigenic action of i.c.v.- and i.p.-injected acyl ghrelin (doses of 1 and 8 pmol/g BW). In contrast, injection of des-acyl ghrelin alone did not show any inhibitory effect on food intake. These results suggest that, as is seen in rodents, circulating acyl ghrelin derived from peripheral tissues acts via primary sensory afferent pathways on feeding centers in the brain. The results also show that des-acyl ghrelin inhibits acyl ghrelin-induced orexigenic activity in goldfish. 相似文献
38.
Tanaka M Sagawa S Hoshi J Shimoma F Yasue K Ubukata M Ikemoto T Hase Y Takahashi M Sasase T Ueda N Matsushita M Inaba T 《Bioorganic & medicinal chemistry》2006,14(17):5781-5794
Conformationally restricted 3-anilino-4-(3-indolyl)maleimide derivatives were designed and synthesized aiming at discovery of novel protein kinase Cbeta (PKCbeta)-selective inhibitors possessing oral bioavailability. Among them, compounds having a fused five-membered ring at the indole 1,2-position inhibited PKCbeta2 with IC50 of nM-order and showed good oral bioavailability. One of the most potent compounds was found to be PKCbeta-selective over other 6 isozymes and exhibited ameliorative effects in a rat diabetic retinopathy model via oral route. 相似文献
39.
Kenji Kanaji Minoru Okuma Fumitaka Ushikubi Haruto Uchino 《Prostaglandins, leukotrienes, and essential fatty acids》1988,31(3):155-161
Lipoxygenase activities were estimated in washed platelets (intact platelets) and their subcellular fractions obtained from 7 patients with deficient platelet lipoxygenase activities and 9 normal subjects. From sonicated platelet preparations, 12,000 g supernatant (F-I), cytosol (F-II) and microsomal fractions (F-III) were prepared by differential centrifugation. When 12-hydroxyeicosatetraenoic acid (12-HETE) produced by the incubation of arachidonic acid with intact platelets or each of their subcellular fractions from normal subjects was measured by reversed-phase high-performance liquid chromatography analysis, the lipoxygenase activities of F-I, F-II and F-III were 87%, 31% and 17%, respectively, of the enzyme activity of intact platelets. One of the patients showed no detectable lipoxygenase activity in any preparation, while the other patients showed reduced enzyme activities in all preparations. The addition of CaCl2 significantly increased 12-HETE synthesis solely by F-I from these patients. In most of these patients, contrary to normal subjects, it appeared that the lipoxygenase activity was not fully expressed in intact platelets, since the F-I produced more 12-HETE than the intact platelets. 相似文献
40.
Nakahara Y Watanabe M Fujita A Kanamori Y Tanaka D Iwata K Furuki T Sakurai M Kikawada T Okuda T 《Journal of insect physiology》2008,54(8):1220-1225
Strategies to combat desiccation are critical for organisms living in arid and semi-arid areas. Larvae of the Australian chironomid Paraborniella tonnoiri resist desiccation by reducing water loss. In contrast, larvae of the African species Polypedilum vanderplanki can withstand almost complete dehydration, referred to as anhydrobiosis. For successful anhydrobiosis, the dehydration rate of P. vanderplanki larvae has to be controlled. Here, we desiccated larvae by exposing them to different drying regimes, each progressing from high to low relative humidity, and examined survival after rehydration. In larvae of P. vanderplanki, reactions following desiccation can be categorized as follows: (I) no recovery at all (direct death), (II) dying by unrepairable damages after rehydration (delayed death), and (III) full recovery (successful anhydrobiosis). Initial conditions of desiccation severely affected survival following rehydration, i.e. P. vanderplanki preferred 100% relative humidity where body water content decreased slightly. In subsequent conditions, unfavorable dehydration rate, such as more than 0.7 mg water lost per day, resulted in markedly decreased survival rate of rehydrated larvae. Slow dehydration may be required for the synthesis and distribution of essential molecules for anhydrobiosis. Larvae desiccated at or above maximum tolerable rates sometimes showed temporary recovery but died soon after. 相似文献