全文获取类型
收费全文 | 14279篇 |
免费 | 1472篇 |
国内免费 | 2374篇 |
专业分类
18125篇 |
出版年
2024年 | 55篇 |
2023年 | 276篇 |
2022年 | 517篇 |
2021年 | 744篇 |
2020年 | 539篇 |
2019年 | 754篇 |
2018年 | 679篇 |
2017年 | 554篇 |
2016年 | 704篇 |
2015年 | 960篇 |
2014年 | 1164篇 |
2013年 | 1206篇 |
2012年 | 1417篇 |
2011年 | 1303篇 |
2010年 | 843篇 |
2009年 | 760篇 |
2008年 | 874篇 |
2007年 | 773篇 |
2006年 | 684篇 |
2005年 | 582篇 |
2004年 | 500篇 |
2003年 | 428篇 |
2002年 | 383篇 |
2001年 | 229篇 |
2000年 | 189篇 |
1999年 | 166篇 |
1998年 | 123篇 |
1997年 | 97篇 |
1996年 | 80篇 |
1995年 | 48篇 |
1994年 | 59篇 |
1993年 | 37篇 |
1992年 | 49篇 |
1991年 | 43篇 |
1990年 | 53篇 |
1989年 | 33篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 30篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1983年 | 21篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 7篇 |
1979年 | 17篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Complete larval development of Crangon hakodatei Rathbun isdescribed, based on material hatched in the laboratory fromovigerous females. The species has six zoeal stages and onepostlarval stage. The morphological characters of the larvaland postlarval stages are described with illustrative figuresand compared with those of two congeneric species. The zoealstages of C. hakodatei can be distinguished from those of otherCrangon species in the number of segments of the antennule peduncle,the number of setae on the antennal scale and basis of the maxillipeds,and the stages of appearance of pereiopods. The first zoealstage in the seven species of Crangon are compared and an annotatedkey for distinguishing them is also provided. 相似文献
43.
固定化酵母细胞生产1,6-二磷酸果糖研究 总被引:2,自引:0,他引:2
本文研究了固定化酵母细胞制备果糖1,6二磷酸(FDP)的方法及其生产。用卡拉胶包埋方法固定化酿酒酵母(Sacchromyces cerevisae),对含葡萄糖1.0M,磷酸盐0.8M的糖磷液,pH6.5,在37℃下进行磷酸化反应。反复分批转化20天以上,可达到平均产FDPH_427.58mg/ml,最高为59.94mg/ml。用100ml固定化细胞生物反应器连续运转309h,稀释速率D=0.097h~(-1),平均产FDPH_4 21.51mg/ml。20L反应器连续运转,生产能力达到1.7g/h.L。用层析方法制备FDPNa_3结晶粉,提取收率为72.08%,制备质量达到或超过了国内外同类产品的质量要求。 相似文献
44.
鹅掌楸雌配子体败育对生殖的影响 总被引:12,自引:0,他引:12
胚珠和雌配子体败育是限制鹅掌楸生殖成功的一个重要因素。中国东部和西部鹅掌楸种群在雌配子体发育的各阶段上的败育程度有差异,以西部种群的发育较好。西部分布区较合适的生境促进了胚囊的发育,一定温度和湿度的环境可以活化珠心细胞输送营养物质供给雌配子体发育,提高受精和结籽的能力 相似文献
45.
水稻叶片对模拟酸雨伤害的生理反应 总被引:4,自引:0,他引:4
水稻暴露于pH2.5~4.2的模拟酸雨中2个月后测定表明:叶片叶绿素含量下降,细胞液离子外渗率增加,气孔阻抗增高,蒸腾速率降低。不同叶位的水稻叶片对模拟酸雨的敏感性不同,杂交稻(汕优63)对模拟酸雨的敏感性较粳稻(中粳864)高 相似文献
46.
探讨了研制的具有谷胱甘肽过氧化物酶活力的含硒抗体酶(GPX-abzyme)对于受损心肌线粒体的保护作用,利用牛的心肌线粒体为实验材料,通过线粒体的膨胀度、脂质过氧化物含量、CCO活力变化及电镜观察等几个方面证明GPX-abzyme能抵抗XO/HX系统产生的自由基的损伤作用,ESR研究也表明GPX-abzyme能明显降低XO/HX损伤系统中的自由基含量。 相似文献
47.
木瓜蛋白酶PPAⅢ自水解作用 总被引:1,自引:0,他引:1
木瓜蛋白酶PPAⅢ自水解作用王秀艳,周慧,葛玉斌,李惟(吉林大学分子生物学系,长春130023)PPAⅢ、papain、pepsine、stembromelain等都属于以Cys-SH为活性中心的酶,同种分子之间存在着一种相互切割的趋势,称为酶自水解... 相似文献
48.
Laminin and Neuropeptide Y Are Increased by Synapsin Transfection in Cultured NG108-15 Neuroblastoma/Glioma Hybrid Cells 总被引:2,自引:0,他引:2
† Gabriel Fried Hui Quan Han ‡Björn Meister ‡Tomas Hökfelt Paul Greengard 《Journal of neurochemistry》1995,64(6):2674-2680
Abstract: We have investigated the presence and expression of laminin and neuropeptide Y (NPY) in several NG108-15 cell lines transfected with synapsin Ib, IIa, or IIb. The content of laminin, a basal membrane glycoprotein that promotes adhesion and induces neurite outgrowth and neuronal differentiation, was increased in all transfected cell lines examined. In cells that were chemically differentiated with prostaglandin E1 plus 3-isobutyl-1-methylxanthine, laminin levels were increased even further. The content of NPY, suggested to be a neurotransmitter/neuromodulator in peripheral sympathetic neurons as well as in central neurons, was also increased in all transfected cell lines examined. Immunohistochemical analysis combined with confocal laser microscopy showed that NPY staining was granular and very often enriched in neuritic varicosities. The distribution and the staining pattern of NPY were consistent with storage of NPY in large dense-cored vesicles. The results indicate that, in differentiated neurons, the synapsins increase the levels of a neuropeptide transmitter stored in large dense-cored vesicles and of an extracellular matrix protein associated with neuronal maturation. 相似文献
49.
Thermotolerance in cultures of Chlorella zofingiensis was induced by heat shock treatment at supraoptimal temperatures (40and
45 °C for 30 min). Thermotolerance was assayed by two methods: the survival of the cells at 70 °C and the growth of diluted
cultures at 35 and 45 °C. A culture without heat shock treatment was unable to grow at 45 °C. According to eletrophoretic
analyses, the synthesis of proteins of 95, 73, 60, 43 and 27 kDa was induced by heat shock treatment. The large molecular
weight proteins (95, 73, 60 and43 kDa) were present in non-heat treated cells, but the heat shock treatment increased their
quantity in cells. The synthesis of a low molecular weight protein (27 kDa) was induced by heat shock treatment. The induced
thermotolerance could be inhibited by the presence of an 80S ribosomal translation inhibitor, cycloheximide(CHI). The first
12 amino acid residues from the N-terminus of the27 kDa heat shock induced protein are Val-Glu-Trp-Try-Gly-Pro-Asn-Arg-Ala-Lys-Phe-Leu.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献