全文获取类型
收费全文 | 3513篇 |
免费 | 232篇 |
国内免费 | 3篇 |
专业分类
3748篇 |
出版年
2023年 | 13篇 |
2022年 | 33篇 |
2021年 | 56篇 |
2020年 | 32篇 |
2019年 | 38篇 |
2018年 | 46篇 |
2017年 | 41篇 |
2016年 | 71篇 |
2015年 | 114篇 |
2014年 | 131篇 |
2013年 | 225篇 |
2012年 | 200篇 |
2011年 | 223篇 |
2010年 | 112篇 |
2009年 | 125篇 |
2008年 | 206篇 |
2007年 | 206篇 |
2006年 | 204篇 |
2005年 | 212篇 |
2004年 | 228篇 |
2003年 | 196篇 |
2002年 | 180篇 |
2001年 | 64篇 |
2000年 | 60篇 |
1999年 | 70篇 |
1998年 | 45篇 |
1997年 | 37篇 |
1996年 | 23篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 31篇 |
1992年 | 37篇 |
1991年 | 46篇 |
1990年 | 43篇 |
1989年 | 31篇 |
1988年 | 31篇 |
1987年 | 31篇 |
1986年 | 16篇 |
1985年 | 24篇 |
1984年 | 28篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 31篇 |
1978年 | 16篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1973年 | 8篇 |
排序方式: 共有3748条查询结果,搜索用时 15 毫秒
941.
942.
Early life stages of Artedidraco skottsbergi and A. shackletoni were collected off Adélie Land. The morphology and pigmentation pattern of nine larvae and juveniles of A. skottsbergi between 17.2 and 21.4 mm in standard length (SL), and of two juveniles of A. shackletoni measuring 25.1 mm SL were described. A. skottsbergi was characterized by a heavily pigmented body, except for the caudal peduncle, with distinctively dense pigmentation on the
ventrolateral half of the body and caudal section (17.2–17.9 mm SL). Furthermore, they had no pigmentation on the pectoral
fin base until they attained 21.4 mm SL. Juvenile A. shackletoni had a heavily pigmented body except for the ventral side of the abdomen and the anal fin base. The proximal part of the dorsal
fin and most of the anal fin were covered with melanophores. Although knowledge of larval and juvenile Artedidraco species is limited, the distribution of melanophores on the fins, pectoral fin base and caudal peduncle at each developmental
stage may be useful for species identification. 相似文献
943.
944.
It is known that plasma serine and threonine concentrations are elevated in rats chronically fed an essential amino acid deficient
diet, but the underlying mechanisms including related gene expressions or serine and threonine concentrations in liver remained
to be elucidated. We fed rats lysine or valine deficient diet for 4 weeks and examined the mRNA expressions of serine synthesising
(3-phosphoglycerate dehydrogenase, PHGDH) and serine/threonine degrading enzymes (serine dehydratase, SDS) in the liver. Dietary
deficiency induced marked elevation of hepatic serine and threonine levels associated with enhancement of PHGDH mRNA expression
and repression of SDS mRNA expression. Increases in plasma serine and threonine levels due to essential amino acid deficiency
in diet were caused by marked increases in hepatic serine and threonine levels. Proteolytic responses to the amino acid deficiency
may be lessened by storing amino radicals as serine and inducing anorexia through elevation of threonine. 相似文献
945.
Multi-walled carbon nanotubes (MWCNTs) were synthesized on platinum plate electrodes by the chemical vapor deposition (CVD) method. From the results of X-ray photoelectron spectroscopy and voltammetric investigation, the iron nanoparticles used as a catalyst for the MWCNT synthesis were enclosed with MWCNTs. The MWCNTs synthesized on the Pt plate (MWCNTs/Pt) electrode were immediately immersed into solutions of d-fructose dehydrogenase (FDH) to immobilize the enzyme onto the MWCNTs/Pt electrode surfaces. After the FDH was immobilized onto the MWCNTs/Pt electrode, a well-defined catalytic oxidation current based on FDH was observed from ca. -0.15V (versus Ag/AgCl/sat'd KCl), which was close to the redox potential of heme c as a prosthetic group of FDH. From an analysis of a plot of the catalytic current versus substrate, the calibration range for the fructose concentration was up to ca. 40mmoldm(-3), and the apparent Michaelis-Menten constant was evaluated to be 11+/-1mmoldm(-3). 相似文献
946.
Tomoharu Iino Yasuhiro Sasaki Makoto Bamba Morihiro Mitsuya Akio Ohno Kenji Kamata Hideka Hosaka Hiroko Maruki Mayumi Futamura Riki Yoshimoto Sumika Ohyama Kaori Sasaki Masato Chiba Norikazu Ohtake Yasufumi Nagata Jun-ichi Eiki Teruyuki Nishimura 《Bioorganic & medicinal chemistry letters》2009,19(19):5531-5538
We describe design, syntheses and structure–activity relationships of a novel class of 4,6-disubstituted quinazoline glucokinase activators. Prototype quinazoline leads (4 and 5) were designed based on the X-ray analyses of the previous 2-aminobenzamide lead classes. Modifications of the quinazoline leads led to the identification of a potent GK activator (21d). 相似文献
947.
948.
949.
Ko Miyoshi Kyosuke Kasahara Ikuko Miyazaki Masato Asanuma 《Biochemical and biophysical research communications》2009,388(4):757-873
The molecular mechanisms underlying the therapeutic effects of lithium, a first-line antimanic mood stabilizer, have not yet been fully elucidated. Treatment of the algae Chlamydomonas reinhardtii with lithium has been shown to induce elongation of their flagella, which are analogous structures to vertebrate cilia. In the mouse brain, adenylyl cyclase 3 (AC3) and certain neuropeptide receptors colocalize to the primary cilium of neuronal cells, suggesting a chemosensory function for the primary cilium in the nervous system. Here we show that lithium treatment elongates primary cilia in the mouse brain and in cultured cells. Brain sections from mice chronically fed with Li2CO3 were subjected to immunofluorescence study. Primary cilia carrying both AC3 and the receptor for melanin-concentrating hormone (MCH) were elongated in the dorsal striatum and nucleus accumbens of lithium-fed mice, as compared to those of control animals. Moreover, lithium-treated NIH3T3 cells and cultured striatal neurons exhibited elongation of the primary cilia. The present results provide initial evidence that a psychotropic agent can affect ciliary length in the central nervous system, and furthermore suggest that lithium exerts its therapeutic effects via the upregulation of cilia-mediated MCH sensing. These findings thus contribute novel insights into the pathophysiology of bipolar mood disorder and other psychiatric diseases. 相似文献
950.