全文获取类型
收费全文 | 4444篇 |
免费 | 265篇 |
国内免费 | 215篇 |
出版年
2024年 | 8篇 |
2023年 | 87篇 |
2022年 | 134篇 |
2021年 | 154篇 |
2020年 | 139篇 |
2019年 | 205篇 |
2018年 | 182篇 |
2017年 | 111篇 |
2016年 | 161篇 |
2015年 | 163篇 |
2014年 | 324篇 |
2013年 | 306篇 |
2012年 | 215篇 |
2011年 | 309篇 |
2010年 | 188篇 |
2009年 | 230篇 |
2008年 | 203篇 |
2007年 | 234篇 |
2006年 | 217篇 |
2005年 | 202篇 |
2004年 | 170篇 |
2003年 | 132篇 |
2002年 | 133篇 |
2001年 | 63篇 |
2000年 | 100篇 |
1999年 | 65篇 |
1998年 | 53篇 |
1997年 | 63篇 |
1996年 | 44篇 |
1995年 | 43篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 25篇 |
1991年 | 22篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1975年 | 14篇 |
1973年 | 5篇 |
排序方式: 共有4924条查询结果,搜索用时 15 毫秒
21.
借助于5'和3'末端删切后重建的IL-2R a链基因调控区次级克隆,在体外合成有放射性同位素参入的反意义RNA探针与总RNA进行液相杂交,结果表明TPA或PHA分别活化的T细胞在IL-2R a链表达过程中都在不同程度上有选择地利用了调控区内分别为-58(5')和+1(3')位两个转录起始点中3'转录起始点。热休克使PHA活化细胞更明显地利用+1位点。PHA诱导Jurkat细胞表达IL-2RamRNA斑点杂交证实,Jurkat细胞在活化16小时表达IL-2Ra基本达到高峰,至24小时已明显下降。根据这一规律提取PHA诱导活化15小时的Jurkat细胞S100和NE,进行有关结合蛋白的研究,初步结果显示磷酸纤维素柱的KCI洗脱组分中存在着DNA结合蛋白,有关结合蛋白性质的研究正在进行中。 相似文献
22.
Induction of accessory cell function of human alveolar macrophages by inhalation of human natural interleukin-2 总被引:1,自引:0,他引:1
Gernot Zissel Walter E. Aulitzky J. Lorenz Christoph Huber J. Müller-Quernheim 《Cancer immunology, immunotherapy : CII》1996,42(2):122-126
Accessory function allows antigen-presenting cells to produce sufficient secondary signals for optimum T cell proliferation
and interleukin-2 (IL-2) production. Alveolar macrophages are inferior accessory cells compared to monocytes (PBM). We report
here that the accessory index (AI) of alveolar macrophages and PBM of patients with lung metastases of solid tumors treated
with inhalations of human natural IL-2 (hnIL-2) increased following its administration (P<0.005). The accessory index was significantly elevated from baseline values after 2 weeks of inhalation of 300 000 IU hnIL-2/day
(8.2±10.2 compared to 1.1±1; P<0.001). The inhalation of 150 000 IU also induced increases in the index (AI = 2.3±1.9), however, without reaching statistical
significance. In addition at 300 000 IU IL-2/day a significant increase in the accessory index was observed for PBM (4±2.5;
P<0.05). The indices of PBM and alveolar macrophages prior to inhalation showed a significant negative correlation with the
age of the patients (r
s = – 0.5; r
s = – 0.8, respectively; P<0.03 for all comparisons). Our data demonstrate that the inhalational application of hnIL-2 enhances the accessory function
of alveolar macrophages and, to lesser extent, the accessory index of PBM, indicating the occurrence of pharmacological immunostimulation.
Received: 16 August 1995 / Accepted: 4 January 1996 相似文献
23.
Maria Claudia Gonzalez Deniselle Susana L. Gonzalez Gerardo G. Piroli Analia E. Lima Alejandro F. De Nicola 《Cellular and molecular neurobiology》1996,16(1):61-72
Summary 1. Wobbler mice suffer an autosomal recessive mutation producing severe motoneuron degeneration and dense astrogliosis, with
increased levels of glial fibrillary acidic protein (GFAP) in the spinal cord and brain stem. They have been considered animal
models of amyotrophic lateral sclerosis and infantile spinal muscular atrophy.
2. Using Wobbler mice and normal littermates, we investigated the effects of the membrane-active steroid Lazaroid U-74389F
on the number of GFAP-expressing astrocytes and glucocorticoid receptors (GR). Lazaroids are inhibitors of oxygen radical-induced
lipid peroxidation, and proved beneficial in cases of CNS injury and ischemia.
3. Four days after pellet implantation of U-74389F into Wobbler mice, hyperplasia and hypertophy of GFAP-expressing astrocytes
were apparent in the spinal cord ventral and dorsal horn, areas showing already intense astrogliosis in untreated Wobbler
mice. In control mice, U-74389F also produced astrocyte hyperplasia and hypertophy in the dorsal horn and hyperplasia in the
ventral-lateral funiculi of the cord.
4. Givenin vivo U-74389F did not change GR in spinal cord of Wobbler or control mice, in line with the concept that it is active in membranes
but does not bind to GR. Besides, U-74390F did not compete for [3H]dexamethasone binding when addedin vitro.
5. The results suggest that stimulation of proliferation and size of GFAP-expressing astrocytes by U-74389F may be a novel
mechanism of action of this compound. The Wobbler mouse may be a valuable animal model for further pharmacological testing
of glucocorticoid and nonglucocorticoid steroids in neurodegenerative diseases. 相似文献
24.
James M. Chen Spero Manolatos Paul W. Brandt-Rauf Randall B. Murphy Regina Monaco Matthew R. Pincus 《Journal of Protein Chemistry》1996,15(6):511-518
The three-dimensional structures of theras-p21 protein and its protein inhibitor, rap-1A, have been computed bound to theras-binding domain, RBD (residues 55–131), of theraf-p74 protein, a critical target protein ofras-p21 in theras-induced mitogenic signal transduction pathway. The coordinates of RBD have been reconstructed from the stereoview of an X-ray crystal structure of this domain bound to rap-1A and have been subjected to energy minimization. The energy-minimized structures of bothras- p21 and rap-1A, obtained in previous studies, have been docked against RBD, using the stereo figure of the RBD-rap-1A complex, based on a six-step procedure. The final energy-minimized structure of rap-1A-RBD is identical to the X-ray crystal structure. Comparison of theras-p21- and rap-1A-RBD complexes reveals differences in the structures of effector domains ofras-p21 and rap-1a, including residues 32–47, a domain that directly interacts with RBD, 60–66, 96–110, involved in the interaction ofras-p21 withjun kinase (JNK) andjun protein, and 115–126, involved in the interaction of p21 with JNK. The structure of the RBD remained the same in both complexes with the exception of small deviations in its-2 binding loop (residues 63–71) and residues 89–91, also involved in binding to rap-1A. The results suggest that the binding of these two proteins to RBD may allow them to interact with other cellular target proteins such as JNK andjun. 相似文献
25.
26.
狂犬病毒“北京株”在地鼠肾传代细胞中增殖的电镜观察 总被引:3,自引:0,他引:3
用透射电子显微镜观察术,对狂犬病固定毒“北京株”在地鼠肾传代细胞(BHK21)中增殖的形态学变化进行了研究。在受感染的细胞中有大量子弹状和长杆状的病毒颗粒。大多数病毒在扩张的内质网膜上以出芽的方式发生,凸向内质网腔内并逐渐发育成子弹状和杆关的成熟病毒。含病的内质,多周围常伴有颗粒或丝状均质区域,少数病毒在细胞膜上芽生。细胞间隙中亦可见病毒。还见病毒在细胞核膜内、外层上芽生,核周围间隙中许多病毒,有 相似文献
27.
Yamazaki Masaaki; Ono Ayako; Watanabe Koji; Sasaki Kuniaki; Tashiro Hiroyuki; Nomura Toru 《DNA research》1995,2(4):187-189
Most ofthe human Not I linking clones identified to date areconsidered to be derived from CpG islands because ofthe recognitionsequence of this enzyme, and CpG islands have been reportedto be located around the 5' regions of genes. As a pilot study,we determined the complete nucleotide sequence (41,924 bp) ofa human cosmid clone (LL21NC02Q7A10) containing the marker D21S246originating from a Not I linking clone. As a result of sequenceanalysis, we successfully mapped and revealed the genomic genestructure for KIAA0002 previously reported as a cDNA clone.This gene consists of 15 exons and was shown to exist at theD21S246 locus on human chromosome 21q21.3q22.1. Theseresults demonstrated that genomic marker-anchored DNA sequencingis a useful approach for the human genome project. 相似文献
28.
W. B. Weglicki I. T. Mak R. E. Stafford B. F. Dickens M. M. Cassidy T. M. Phillips 《Molecular and cellular biochemistry》1994,130(2):103-109
Dietary deficiency of magnesium (Mg) in rodents results in cardiomyopathic lesion formation. In our rat model, these lesions develop after 3 weeks on the Mg-deficient diet; significant elevation of several cytokines, IL-1, IL-6 and TNF also occurs. In probing the mechanisms of lesion formation, we obtained data supporting the participation of free radicals (Freedman AMet al.: Bioch Biophys Res Commun 1990; 170: 1102). Recently, we identified an early elevation of circulating substance P and proposed a role of neurogenic peptides during Mg-deficiency (Weglicki WB, Phillips TM: Am J Phys 1992; 262: R734). The present study was designed to evaluate the contribution of neurogenic peptides to the pathogenesis of Mg-deficiency. In the blood, substance-P and calcitonin gene related peptide (CGRP) are elevated during the first week on the diet. During the second week, circulating histamine, PGE2 and TBAR-materials were elevated and red cell glutathione was reduced, all prior to the elevation of the inflammatory cytokines during the third week. When the rats were treated with the substance P-receptor blocker [CP-96,345], the levels of substance P and CGRP remained elevated; however, increases in histamine, PGE2, TBAR-materials, and the decrease in red cell glutathione were inhibited; also, the development of cardiac lesions was inhibited significantly. These data support a central role for neurogenic peptides, especially substance P, in the development of cardiomyopathic lesions during Mg-deficiency. 相似文献
29.
A human episomal sequence (HALF1) has been identified by its ability to restore expression of hepatic functions when used to transfect a rat dedifferentiated cell line. The genomic equivalent of this human episome (gHALF1) and its flanking sequences were analyzed. HALF1 itself does not present the characteristics of a transposable element but half of its sequence corresponds to retroposons, including Alu and L1 repeats and a processed pseudogene, known to transposevia RNA intermediates. The structural characteristics of these different kinds of retroposons and their origin and evolution were analyzed. 相似文献
30.
R. Landmann U. Keilholz C. Scheibenbogen M. Brockhaus H. Gallati H. Denz M. Bargetzi C. Ludwig 《Cancer immunology, immunotherapy : CII》1994,38(2):113-118
Eleven metastatic cancer patients were studied during three different regimens of immunotherapy with interleukin-2 (IL-2) and/or interferon (IFN): group A received 4 days of IL-2 i.a. infusion (n=3), group B IFN s.c. during 5 days (n=4), followed on day 3 by 5 days of a continuous IL-2 i.v. infusion, and group C had 4 days of IL-2 i.v. infusion together with s.c. IFN on days 1 and 4 (n=4). Soluble tumor necrosis factor receptors (sTNFR) p55 and p75 and TNF concentrations in serum were analyzed before therapy and daily during 8 days of the first therapy cycle. sTNFR was measured by radioimmunoassay. sTNFR p55 increased in all patient groups from a baseline value of 5.2±0.9 ng/ml to a maximum of 13.6±1.2 ng/ml by days 3–4 (P=0.003). sTNFR p75 increased from 7.6±1.1 ng/ml to peak values of 30.1±2.6 ng/ml in groups A and B (P=0.02). In group C the sTNFR p75 response was weak (NS). In group B, the increase of both p55 and p75 occurred only after addition of IL-2 to IFN. TNF increased weakly during treatment with IFN alone (group B); it rose strongly during IL-2 and the combined treatment (groups A-C) from 8±2 pg/ml to 115±13 pg/ml (P=0.003). In group B, it reached the maximum 24 h after addition of IL-2 to IFN and decreased thereafter. there was a significant relationship between TNF and sTNFR p55 or sTNFR p75 in groups A and C, (P=0.001), but not in group B. Group C was also investigated during the third therapy cycle. The increase of sTNFR p75 was stronger (P=0.01) and that of TNF weaker than in the first cycle; the sTNFR p55 response was similar in both cycles. In conclusion sTNFR p55 and p75 are rapidly induced during IL-2 and IL-2+IFN treatment, the increase of sTNF receptors parallels or exceeds that of TNF and may influence the immunomodulatory effects of TNF during cytokine therapy. 相似文献