全文获取类型
收费全文 | 10305篇 |
免费 | 963篇 |
国内免费 | 1297篇 |
出版年
2024年 | 56篇 |
2023年 | 243篇 |
2022年 | 494篇 |
2021年 | 752篇 |
2020年 | 549篇 |
2019年 | 599篇 |
2018年 | 552篇 |
2017年 | 417篇 |
2016年 | 575篇 |
2015年 | 729篇 |
2014年 | 930篇 |
2013年 | 901篇 |
2012年 | 1057篇 |
2011年 | 884篇 |
2010年 | 490篇 |
2009年 | 493篇 |
2008年 | 502篇 |
2007年 | 450篇 |
2006年 | 325篇 |
2005年 | 287篇 |
2004年 | 247篇 |
2003年 | 157篇 |
2002年 | 178篇 |
2001年 | 79篇 |
2000年 | 85篇 |
1999年 | 67篇 |
1998年 | 51篇 |
1997年 | 47篇 |
1996年 | 34篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 23篇 |
1992年 | 29篇 |
1991年 | 31篇 |
1990年 | 31篇 |
1989年 | 33篇 |
1988年 | 14篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1977年 | 5篇 |
1973年 | 3篇 |
1966年 | 2篇 |
1962年 | 2篇 |
1950年 | 2篇 |
1940年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
小鼠精母细胞联会复合体RNA组分的电镜研究 总被引:1,自引:1,他引:0
本文运用常规染色和Bernhard染色方法对切片标本中小鼠粗线期精母细胞联会复合体(SC)的超微结构和电镜细胞化学特点进行了研究。经常规染色后,可见SC由侧生组分(LE)、中央组分(CE)和L-C纤维组成;SC宽约210nm,LE宽约60nm,中央间隔区宽约90nm。在Bernhard染色标本中,SC的LE、CE和L-C纤维着色较深,说明其中含有RNA;SC各结构组分的宽度和形态特点与常规染色标本中的基本一致。本文讨论了SC中存在有RNA等问题。 相似文献
22.
23.
利用我们研制的厌氧培养皿及管,共检验了39份牙髓炎及牙周炎标本,分离出厌氧菌59株,标本中厌氧菌分离的阳性率为100%。其中类杆菌28株,消化链球菌9株,消化球菌7株,韦荣氏球菌5株,真杆菌2株,梭形杆菌8株。在类杆菌中产黑素类杆菌21株,占类杆菌总数的75%。结果表明使用厌氧培养皿及管研究厌氧菌简便、有效、经济,适于基层单位应用。 相似文献
24.
蚕豆根端细胞核中微核仁的研究 总被引:1,自引:0,他引:1
以蚕豆(Vicia faba)根端分生组织细胞为材料研究了微核仁的超微结构和细胞化学特点。结果表明;微核仁是直径0.3—0.5μm 的卵圆形或球形结构。常规染色时,微核仁与集缩染色质的电子密度相仿,但两者之间在结构上没有任何联系。细胞化学研究指出,微核仁含有 RNA 和蛋白质,其结构成分主要是与核仁颗粒组分十分相似的 RNP 颗粒。报道了植物细胞核中微核仁发生于核仁的过程并对微核仁的本质和功能进行了讨论。 相似文献
25.
Summary P-protein and the changes it undergoes after wounding of sieve tubes of secondary phloem in one- to two-year old shoots ofHevea brasiliensis has been studied using electron microscopy. The P-protein in the form of tubules with a diameter of 8–9 nm and a lumen of 2–2.5 nm occurred in differentiating sieve elements and appeared as compact bodies which consisted of small aggregates of the tubules. As the sieve elements matured, these P-protein bodies dispersed with a disaggregation of the tubules before they turned into striated fibrils, 10–11 nm in diameter. In wounding experiments, as the mature sieve elements collapsed after cutting, their striated P-protein converted into tubules. These tubules were the same in ultrastructure as the tubules in differentiating sieve elements and they often were arranged in crystalline aggregates. 相似文献
26.
27.
Targeting of glycoprotein I (gE) of varicella-zoster virus to the trans-Golgi network by an AYRV sequence and an acidic amino acid-rich patch in the cytosolic domain of the molecule. 总被引:10,自引:9,他引:1
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Previous studies suggested that varicella-zoster virus (VZV) envelope glycoproteins (gps) are selectively transported to the trans-Golgi network (TGN) and that the cytosolic domain of gpI (gE) targets it to the TGN. To identify targeting signals in the gpI cytosolic domain, intracellular protein trafficking was studied in transfected cells expressing chimeric proteins in which a full-length or mutated gpI cytosolic domain was fused to the gpI transmembrane domain and interleukin-2 receptor (tac) ectodomain. Expressed protein was visualized with antibodies to tac. A targeting sequence (AYRV) and a second, acidic amino acid-rich region of the gpI cytosolic domain (putative signal patch) were each sufficient to cause expressed protein to colocalize with TGN markers. This targeting was lost when the tyrosine of the AYRV sequence was replaced with glycine or lysine, when arginine was replaced with glutamic acid, or when valine was substituted with lysine. In contrast, tyrosine could be replaced by phenylalanine and valine could be substituted with leucine. Mutation of alanine to aspartic acid or deletion of alanine abolished TGN targeting. Exposure of transfected cells to antibodies to the tac ectodomain revealed that the TCN targeting of expressed tac-gpI chimeric proteins occurred as a result of selective retrieval from the plasmalemma. These data suggest that the AYRV sequence and a second signaling patch in the cytosolic domain of gpI are responsible for its targeting to the TGN. The observations also support the hypothesis that the TGN plays a critical role in the envelopment of VZV. 相似文献
28.
A study was undertaken to develop a protoplast regeneration system for pinellia. A yield of 19 29 x 105 protoplasts/g F. W. could be obtained from cell suspension cultures incubated in a digestion enzyme solution with 2% cellulase Onzuka R-10, 10% pectinase (Sigma), 0.01% pectolyase Y23. K8P and modified MS media were used to culture protoplasts in: a) liquid, b) liquid-solid double layer, or c) agarose embedded protoplast culture. The former two were conducive to colony formation from protoplast-derived cells. The frequency of cell division was about 8% after 3 days in culture. Gradually adding fresh medium of lower osmotic pressure into the medium for protoplast culture favored cell division. Calli (1–2 mm in diameter) formed after 30–40 days in culture. The calli transferred onto medium supplemented with KT (0.5 mg 1–1) and NAA (0.2 mg 1)–1) could regenerate plants after 40–50 days. Of 47 plantlets transplanted into plots, 29 flowered and were fertile.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- NAA
-naphthaleneacetic acid
- KT
kinetin
- CH
casein hydrolysate 相似文献
29.
应用SDS-聚丙烯酰胺凝胶电泳及免疫转印技术对流行性出血热患才血清中免疫合物组分进行了分析。流行性出血热循环免疫复合物经SDS-PAGE分离,考马斯亮兰染色,显色主要有7条带,分子量分别为23kD,50kD,52kD,65kD,72kD,80kD及100kD。采用该病毒特异性抗血清、单克隆抗体以及人免疫球蛋白、补体成分抗血清识别,在其特环免疫复合物中可检出特异性病毒抗在及相应的免疫球状蛋白和补体成 相似文献
30.
采用Rotofor等电聚焦和分子筛技术纯化大肠杆菌表达的重组链激酶(r—SK),其纯度为97%。比活性1×106IU/mg,回收率41%。分析所纯化的r—SK N端氨基酸顺序证实其1—15个氨基酸顺序与SK基因的核苷酸顺序所示3联密码子一致。以纯化r—SK为抗原,通过杂交瘤技术构建了分泌抗r—SK单克隆抗体(McAb)杂交瘤细胞(4D11),该McAb属IgG1亚型.特异地作用于r-SK和C组口溶血性链球菌分泌的SK。用底物显色法测定该McAb可抑制SK对纤溶酶原的激活。Western blot法证实该McAb能识别分子量为16 250Da的r—SK的CNBr裂解片段。推测SK蛋白中第71残基至第237残基间的氨基酸顺序参与SK与纤溶酶原的结合。 相似文献