全文获取类型
收费全文 | 4059篇 |
免费 | 371篇 |
国内免费 | 3篇 |
出版年
2023年 | 19篇 |
2022年 | 56篇 |
2021年 | 91篇 |
2020年 | 58篇 |
2019年 | 77篇 |
2018年 | 85篇 |
2017年 | 90篇 |
2016年 | 101篇 |
2015年 | 197篇 |
2014年 | 192篇 |
2013年 | 224篇 |
2012年 | 333篇 |
2011年 | 278篇 |
2010年 | 161篇 |
2009年 | 137篇 |
2008年 | 223篇 |
2007年 | 191篇 |
2006年 | 167篇 |
2005年 | 178篇 |
2004年 | 163篇 |
2003年 | 176篇 |
2002年 | 160篇 |
2001年 | 72篇 |
2000年 | 46篇 |
1999年 | 58篇 |
1998年 | 48篇 |
1997年 | 48篇 |
1996年 | 32篇 |
1995年 | 38篇 |
1994年 | 30篇 |
1993年 | 39篇 |
1992年 | 56篇 |
1991年 | 39篇 |
1990年 | 32篇 |
1989年 | 42篇 |
1988年 | 34篇 |
1987年 | 47篇 |
1986年 | 35篇 |
1985年 | 28篇 |
1984年 | 37篇 |
1983年 | 41篇 |
1982年 | 16篇 |
1981年 | 27篇 |
1980年 | 22篇 |
1979年 | 25篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1973年 | 19篇 |
1972年 | 16篇 |
1971年 | 16篇 |
排序方式: 共有4433条查询结果,搜索用时 15 毫秒
61.
Avraham Geier Rachel Beery Michal Haimsohn Rina Hemi Zvi Malik Avraham Karasik 《In vitro cellular & developmental biology. Animal》1994,30(12):867-874
Summary The ability of epidermal growth factor (EGF), insulinlike growth factor-1 (IGF-1), insulin, 12-O-tetradecanoylphorbol-13-acetate
(TPA), and aurintricarboxylic acid (ATA) to protect the human breast cancer cell line MDA-231 from death induced by the anticancer
drug adriamycin was investigated. Cell death was induced in the MDA-231 cells either by a short-time exposure to a high dose
of adriamycin (2 μg · ml−1 · 1 h−1) and further culturing in the absence of the drug, or by continuous exposure to a low dose of adriamycin (0.3μg/ml). Cell death was evaluated after 48 h of incubation by several techniques (trypan blue dye exclusion, lactic dehydrogenase
activity, cellular ATP content, transmission electron microscopy, and DNA fragmentation). EGF, TPA, and ATA, each at an optimal
concentration of 20 ng/ml, 5 ng/ml, and 100μg/ml respectively, substantially enhanced survival of cells exposed either to a high or low dose of adriamycin. Neither IGF-1
nor insulin, each at concentrations of 20 ng/ml, had an effect on cell survival. The three survival factors enhanced protein
synthesis in the untreated cells and attenuated the continuous decrease in protein synthesis in the adriamycin-treated cells.
Moreover, the three survival factors protected the MDA-231 cells from death in the absence of protein synthesis (cycloheximide
30μg/ml). These results suggest that EGF, TPA, and ATA promote survival of adriamycin pretreated cells by at least two mechanisms:
enhancement of protein synthesis and by a protein synthesis independent process, probably a posttranslational modification
effect. 相似文献
62.
Sally Badawi Feda E. Mohamed Divya Saro Varghese Bassam R. Ali 《Traffic (Copenhagen, Denmark)》2023,24(8):312-333
Endoplasmic reticulum-associated protein degradation (ERAD) is a stringent quality control mechanism through which misfolded, unassembled and some native proteins are targeted for degradation to maintain appropriate cellular and organelle homeostasis. Several in vitro and in vivo ERAD-related studies have provided mechanistic insights into ERAD pathway activation and its consequent events; however, a majority of these have investigated the effect of ERAD substrates and their consequent diseases affecting the degradation process. In this review, we present all reported human single-gene disorders caused by genetic variation in genes that encode ERAD components rather than their substrates. Additionally, after extensive literature survey, we present various genetically manipulated higher cellular and mammalian animal models that lack specific components involved in various stages of the ERAD pathway. 相似文献
63.
Paul G. McGuire Helen M. Walker-Caprioglio Sally A. Little Linda J. McGuffee 《In vitro cellular & developmental biology. Animal》1993,29(2):135-139
Summary The structure and function of vascular smooth muscle cells have been extensively investigated with the aid of in vitro culture
techniques. The majority of studies have utilized aortic tissue as the source of cells. We present here a method for isolating
and culturing smooth muscle cells of the rat superior mesenteric artery, an elasto-muscular vessel that is structurally and
functionally different from the aorta. Cells were isolated from partially digested explants and characterized by immunochemical
and biochemical techniques. Unlike cultured fibroblasts, the cultured cells stained positive for smooth muscle specific actin.
The cells also produced laminin and type IV collagen in culture. This method provides a means for the isolation of large numbers
of viable smooth muscle cells from the superior mesenteric artery which can be propagated in culture for in vitro study. 相似文献
64.
65.
Dr. Sally Hughes-Schrader 《Chromosoma》1959,10(1-6):268-277
Summary A wide diversity in chromosome complement is found in two species of phasmids of the primitive group Prisopini—Prisopus ariadne
Hebard and Prisopus berosus
Westwood.
P. ariadne has a diploid male complement of 28, comprising 13 pairs of relatively large mediokinetic autosomes and Neo XY sex chromosomes.
P. berosus, 2n =49, has relatively small autosomes most of which are mediokinetic, and retains the XO—XX sex mechanism. Chromosomal polymorphism in this species is suggested by the presence of an unequal pair of autosomes and a structural differentiation in the X in one of two males studied.The relative amount of DNA per nucleus in male germ cells (Peulgen cytophotometry) shows a significant difference in total chromosomal content between the complements of the two species.These data are discussed with reference to the cytotaxonomy of phasmids.Supported in part by research grant G-4370 from the National Institutes of Health, Public Health Service. 相似文献
66.
Sally Cole 《American anthropologist》2003,105(2):414-416
Feminine Matters: Women's Religious Practices in. Portuguese Town. Lena Gemzöe. Berlin: Walter de Gruyter, 2000. 273 pp. 相似文献
67.
Ved Malik Mark B. Watson Russell L. Malmberg 《Journal of plant biochemistry and biotechnology.》1996,5(2):109-112
A partial cDNA clone encoding ornithine decarboxylase (ODC) has been isolated and sequenced from Nicotiana tabaccum. This 961 by long cDNA contained an open reading frame in only one of the six possible frames. Sequence comparisons have shown it to be very similar with other ODCs, and most similar to that from Datura. The present sequence is a partial sequence containing only 3′ half of the cDNA. 相似文献
68.
Sally Gregory Kohlstedt 《Journal of the history of biology》1995,28(1):151-166
Mary P. Winsor,Reading the shape of Nature: Comparative zoology at the Agassiz Museum (Chacago: University of Chicago Press, 1991); Ronald Rainger,An Agenda for Antiquty: Henry Fairfield Osborn and Vertedrate Paleontology at the American Meseum of Natural History, 1890–1935 (Tuscaloosa: University of Aladama Press, 1991). 相似文献
69.
Cotton ovules collected during late September with prevalent night cool temperature (15°C), cultured at 30°C/15°C i.e. cycling temperatures in Beasley and Ting medium had very few epidermal cells showing bulging. Supplementing cultures with guaianolide derivative I (E-13 methyldehydrocostus lactone) promoted fibre initiation. At—1 day preanthesis (DPA), IAA oxidase activity declined in guaianolide-treated cultures but increased during the elongation phase and was enhanced during the secondary wall thickening phase. However, o-diphenol oxidase activity was adversely affected during the fibre initiation phase. The activities of all the other enzymes studied viz. acid invertase, phenylalanine ammonia lyase, -glucosidase and IAA oxidase increased, except -galactosidase, during the later phase in comparison with the controls. The present study indicates that guaianolide derivative I triggers early initiation and promotes fibre elongation by regulatin o-diphenols and IAA-oxidation levels, which in turn check wall loosening. Considerable enhancement in the soluble acid invertase activity by this compound suggests its role in apoplastic sucrose hydrolysis, thereby preventing its accumulation.Abbreviations DPA
days pre anthesis
- DAC
days after culturing
- DAA
days after anthesis 相似文献
70.
Zfy1 is a mouse Y chromosomal gene encoding a zincfinger protein which is thought to have some function during spermatogenesis. Here we show that, when introduced into tissue culture cells, Zfy1 is targeted to the nucleus. Two independent signals are present within the protein for nuclear localization. This nuclear Zfy1 protein is able to bind strongly to DNA-cellulose and, using site-selection assays, we have identified specific Zfy1 DNA binding sites. Taken together these results suggest that Zfy1 is a nuclear-located sequence-specific DNA binding protein which functions during spermatogenesis. 相似文献