全文获取类型
收费全文 | 5807篇 |
免费 | 347篇 |
国内免费 | 1篇 |
出版年
2022年 | 33篇 |
2021年 | 66篇 |
2019年 | 41篇 |
2018年 | 59篇 |
2017年 | 59篇 |
2016年 | 84篇 |
2015年 | 127篇 |
2014年 | 202篇 |
2013年 | 263篇 |
2012年 | 263篇 |
2011年 | 294篇 |
2010年 | 150篇 |
2009年 | 142篇 |
2008年 | 255篇 |
2007年 | 261篇 |
2006年 | 253篇 |
2005年 | 281篇 |
2004年 | 232篇 |
2003年 | 240篇 |
2002年 | 265篇 |
2001年 | 234篇 |
2000年 | 248篇 |
1999年 | 180篇 |
1998年 | 97篇 |
1997年 | 58篇 |
1996年 | 51篇 |
1995年 | 55篇 |
1994年 | 54篇 |
1993年 | 52篇 |
1992年 | 122篇 |
1991年 | 136篇 |
1990年 | 105篇 |
1989年 | 106篇 |
1988年 | 122篇 |
1987年 | 99篇 |
1986年 | 91篇 |
1985年 | 85篇 |
1984年 | 60篇 |
1983年 | 63篇 |
1982年 | 45篇 |
1980年 | 35篇 |
1979年 | 49篇 |
1978年 | 43篇 |
1977年 | 27篇 |
1976年 | 30篇 |
1975年 | 35篇 |
1974年 | 31篇 |
1973年 | 35篇 |
1971年 | 34篇 |
1970年 | 29篇 |
排序方式: 共有6155条查询结果,搜索用时 46 毫秒
991.
Thyroglobulin regulates follicular function and heterogeneity by suppressing thyroid-specific gene expression. 总被引:1,自引:0,他引:1
992.
Benthic moss pillars in Antarctic lakes 总被引:2,自引:0,他引:2
Unique pillar-like colonies of aquatic mosses, rising from cyanobacterial and algal mats, have been discovered in some freshwater
lakes in the vicinity of Syowa Station (69°00′S, 39°35′E), continental Antarctica. These moss pillars are about 40 cm in diameter
and up to 60 cm high and occur at the lake bottoms mainly between 3 and 5 m depth. The primary component is a species of Leptobryum, a genus unknown in the continental Antarctic terrestrial bryoflora and as an aquatic genus elsewhere in the world. Bryum pseudotriquetrum is often an associated species. In longitudinal section the pillars reveal several whitish layers formed by mineral sediment
and dead cyanobacteria. It is speculated that the biomass of aquatic mosses at the bottom of many Antarctic lakes is considerably
greater than that previously estimated.
Accepted: 11 April 1999 相似文献
993.
Hiroaki Harayama Masafumi Koide Koji Obata Akio Iio Masato Iida Nahomi Matsuda Robert E. Akins Mitsuhiro Yokota Rocky S. Tuan Hidehiko Saito 《Journal of cellular physiology》1998,177(2):289-298
An accelerated weight gain is noted in the heart of Ca-deficient, hypertensive chick embryos maintained in a shell-less culture in vitro. We previously observed that the Ca handling property of cardiomyocytes isolated from the shell-less embryo is altered, i.e., faster Ca uptake, suggesting a requirement for adequate Ca supply and/or proper Ca handling in embryonic cardiac development. In this study, we have examined the function of Ca on cardiomyocytes by analyzing the effects of (1) various Ca concentration in the culture medium (NCa, 1.8 mmol/L; HCa, 2.8 mmol/L; LCa, 0.9 mmol/L), and (2) various modulators of Ca handling on cell proliferation and phenotype regulation in chick embryonic cardiomyocytes. The analytical parameters included cell number, DNA content, expression of cell cycle–specific and cardiomyocyte-specific proteins, and creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) enzyme activities. Cell number and total DNA were significantly larger (P < 0.01) in LCa cultures compared with those in NCa. The level of LDH was elevated (P < 0.01), but that of CPK was lowered in LCa. Expression of the G1-S–specific protein PCNA was raised, but that of the contractile proteins myosin and tropomyosin was substantially suppressed in LCa; in HCa, the cells did not proliferate as well, whereas the level of contractile proteins was higher. Thapsigargin, a sarcoplasmic reticulum (SR)-specific, Ca-ATPase inhibitor, simulated the effects of LCa by enhancing cell proliferation and lowering the expression of tropomyosin. These results suggest that culturing in low Ca concentration and inhibition of SR Ca pumping enhance myocardial cell proliferation and suppress sarcomeric protein expression, perhaps by inducing cellular de-differentiation. The in vitro effects of medium Ca concentration and Ca handling modulators on cardiomyocytes also suggest that the in vivo cardiomegaly of the SL embryos is a direct result of Ca-deficiency, and that Ca is important in the phenotype regulation of cardiomyocytes. J. Cell. Physiol. 177:289–298, 1998. © 1998 Wiley-Liss, Inc. 相似文献
994.
Hiroko Saito Fumiko Matsukawa-Usami Toshihiko Fujimori Toshiya Kimura Takahiro Ide Takaki Yamamoto Tatsuo Shibata Kenta Onoue Satoko Okayama Shigenobu Yonemura Kazuyo Misaki Yurina Soba Yasutaka Kakui Masamitsu Sato Mika Toya Masatoshi Takeichi 《Molecular biology of the cell》2021,32(20)
Motile cilia of multiciliated epithelial cells undergo synchronized beating to produce fluid flow along the luminal surface of various organs. Each motile cilium consists of an axoneme and a basal body (BB), which are linked by a “transition zone” (TZ). The axoneme exhibits a characteristic 9+2 microtubule arrangement important for ciliary motion, but how this microtubule system is generated is not yet fully understood. Here we show that calmodulin-regulated spectrin-associated protein 3 (CAMSAP3), a protein that can stabilize the minus-end of a microtubule, concentrates at multiple sites of the cilium–BB complex, including the upper region of the TZ or the axonemal basal plate (BP) where the central pair of microtubules (CP) initiates. CAMSAP3 dysfunction resulted in loss of the CP and partial distortion of the BP, as well as the failure of multicilia to undergo synchronized beating. These findings suggest that CAMSAP3 plays pivotal roles in the formation or stabilization of the CP by localizing at the basal region of the axoneme and thereby supports the coordinated motion of multicilia in airway epithelial cells. 相似文献
995.
Ryo Nakabayashi Noriko Takeda-Kamiya Yutaka Yamada Tetsuya Mori Mai Uzaki Takashi Nirasawa Kiminori Toyooka Kazuki Saito 《Plant Biotechnology》2021,38(3):305
Plants release specialized (secondary) metabolites from their roots to communicate with other organisms, including soil microorganisms. The spatial behavior of such metabolites around these roots can help us understand roles for the communication; however, currently, they are unclear because soil-based studies are complex. Here, we established a multimodal metabolomics approach using imaging mass spectrometry (IMS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to spatially assign metabolites under laboratory conditions using agar. In a case study using Catharanthus roseus, we showed that 58 nitrogen (N)-containing metabolites are released from the roots into the agar. For the metabolite assignment, we used 15N-labeled and non-labeled LC-MS/MS data, previously reported. Four metabolite ions were identified using authentic standard compounds as derived from monoterpene indole alkaloids (MIAs) such as ajmalicine, catharanthine, serpentine, and yohimbine. An alkaloid network analysis using dot products and spinglass methods characterized five clusters to which the 58 ions belong. The analysis clustered ions from the indolic skeleton-type MIAs to a cluster, suggesting that other communities may represent distinct metabolite groups. For future chemical assignments of the serpentine community, key fragmentation patterns were characterized using the 15N-labeled and non-labeled MS/MS spectra. 相似文献
996.
Yukiko Kobayashi Yohei Saito Masuo Goto Kyoko Nakagawa-Goto 《Bioorganic & medicinal chemistry letters》2017,27(12):2731-2735
In the course of our continuing studies on the 2-(benzo[b]thiophene-3′-yl)-6,8,8-triethyldesmosdumotin B (TEDB-TB) series, we designed and synthesized nine amino-TEDB-TB derivatives to improve pharmaceutical properties, identify structure activity relationships, and discover novel antitubulin agents. Among all newly synthesized amino-TEDB-TBs, the 5′- and 6′-amino derivatives, 6 and 7, exhibited significant antiproliferative activity against five human tumor cell lines, including an MDR subline overexpressing P-gp. The IC50 values of 0.50–1.01 µM were 3–6 times better than those of previously reported hydroxy-TEDB-TBs. Compounds 6 and 7 inhibited tubulin polymerization, induced both depolymerization of interphase microtubules and multiple spindle formations, and caused cell arrest at prometaphase. Among all compounds, compound 7 scored best pharmaceutically with LogP 2.11 and biologically with greater antiproliferative activity and induction of cell cycle arrest at prometaphase. 相似文献
997.
Yoshikazu Watanabe Kohei Hayashida Daisuke Saito Toshihiro Takahashi Junichi Sakai Eriko Nakata Takashi Kanda Takashi Iwai Shigeto Hirayama Hideaki Fujii Tomio Yamakawa Hiroshi Nagase 《Bioorganic & medicinal chemistry letters》2017,27(15):3495-3498
We designed and synthesized novel δ opioid receptor (DOR) agonists 3a–i with an azatricyclodecane skeleton, which was a novel structural class of DOR agonists. Among them, 3b exhibited high values of binding affinity and potent agonistic activity for the DOR that were approximately equivalent to those of 2 which bore an oxazatricyclodecane skeleton. In vitro assays using the blood-brain barrier (BBB) permeability test kit supported the idea that 3b achieved an excellent BBB permeability by converting an oxygen atom of 2 to a carbon atom (methylene group) in the core skeleton. As a result, 3b showed potent antinociceptive effects. 相似文献
998.
Masakazu Atobe Natsumi Yamakawa Yasuhiro Wada Tokuhito Goto Masashi Kawanishi Takeshi Ito Makoto Saito Masahiro Takeda Takanori Tabata Hirokazu Arai 《Bioorganic & medicinal chemistry letters》2017,27(21):4828-4831
A series of indazole derivatives were identified as Sirt 1 activators though high-throughput screening. Optimization of each substituent on the indazole ring led to the identification of compound 13. Compound 13 appeared to give the best Sirt 1 activity of the compounds tested and also showed osteogenesis activity in a cell assay. Sirt 1 activators are therefore potential candidates for the treatment of osteoporosis. 相似文献
999.
1000.