全文获取类型
收费全文 | 17756篇 |
免费 | 1497篇 |
国内免费 | 4479篇 |
出版年
2024年 | 119篇 |
2023年 | 435篇 |
2022年 | 521篇 |
2021年 | 544篇 |
2020年 | 538篇 |
2019年 | 535篇 |
2018年 | 374篇 |
2017年 | 447篇 |
2016年 | 479篇 |
2015年 | 580篇 |
2014年 | 1071篇 |
2013年 | 771篇 |
2012年 | 982篇 |
2011年 | 1194篇 |
2010年 | 921篇 |
2009年 | 1094篇 |
2008年 | 1309篇 |
2007年 | 967篇 |
2006年 | 884篇 |
2005年 | 926篇 |
2004年 | 901篇 |
2003年 | 770篇 |
2002年 | 800篇 |
2001年 | 794篇 |
2000年 | 696篇 |
1999年 | 609篇 |
1998年 | 486篇 |
1997年 | 459篇 |
1996年 | 509篇 |
1995年 | 481篇 |
1994年 | 436篇 |
1993年 | 370篇 |
1992年 | 354篇 |
1991年 | 321篇 |
1990年 | 306篇 |
1989年 | 240篇 |
1988年 | 114篇 |
1987年 | 88篇 |
1986年 | 63篇 |
1985年 | 124篇 |
1984年 | 33篇 |
1983年 | 33篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 4篇 |
1966年 | 2篇 |
1963年 | 2篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1950年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
992.
993.
994.
995.
胸腺细胞在胸腺外凋亡的形态学证据 总被引:1,自引:0,他引:1
In vitro thymus explants culture designed in this paper can mimic the thymic microenvironment as it were in vivo. Theoretically, thymus explants are cut off free from blood stream. So if some developing or developed thymocytes had the inclination to migrate into the periphery, they would only be accumulated in the blood vessels within thymus explants. After 3-day's culture, under transmission electron microscope we observed the migrating thymocytes accumulated in the blood vessels of C57BL/6 mice thymus explants, and these thymocytes were occurring apoptosis at different stage. To our knowledge, this findings offers the first morphological evidence that thymocytes do not necessarily die inside the thymus in situ, and that having acquired the death signals thymocytes can migrate into the blood stream and die quickly outside the thymus. But this is not to say that we deny the intrathymic death hypothesis. On the contrary, we found the number of thymocytes occurring in situ apoptosis on the surfaces of stromal cells is far more than that of migrating into the blood vessels. So, our proposal is that there are two sites for thymocytes apoptosis, some die inside the thymus and the others die outside the thymus. 相似文献
996.
鼠白细胞介素12(mIL—12)在昆虫细胞中的表达 总被引:1,自引:0,他引:1
Since human IL-12 is species-specific in its functions and elicits little biological responses from mouse lymphocytes, it is necessary to express recombinant murine IL-12 for the usage in studying the effects of this cytokine in various rodent models. Thereby, we can investigate the role of IL-12 in immune response in vivo and evaluate its potential clinical utility. Thus, we firstly constructed two expression vectors, pVL1393-mp40 and pVL1393-mp35. They were used to co-transfect the insect cells(Sf9) separately with linearized polyhedrosis virus genomic DNA. Two kinds of recombinant viruses AcNPV-mp40 and AcNPV-mp35 were visually screened out, and mp40 and mp35 were co-expressed in the insect cells co-infected by AcNPV-mp40 and AcNPV-mp35. The results of real-time Biomolecular Interaction Analysis (BIA) and Northern blot demonstrated that the recombinant mIL-12 was expressed successfully in the insect cells. The molecular weights of recombinant mp40 and mp35 were 40 KDa and 22 KDa on SDS-PAGE under reducing conditions, respectively. The apparent molecular weight of recombinant mIL-12 is 80 KDa under non-reducing conditions of Western blot. Biological activity of the recombinant product was detected in conditional medium using antibody-capture bioassay. The expression level of recombinant mIL-12 was about 10-15 micrograms/10(6) cells, as compared with the calibration curve of mIL-12. 相似文献
997.
天花粉收白诱发白血病细胞K562凋亡的研究 总被引:8,自引:1,他引:7
Trichosanthin (TCS), an eukaryotic ribosome-inactivating protein isolated from the root tuber of Trichosanthes plant, has various biological activities including abortion induction, antitumor, and anti-HIV. In this study, cultured human leukemia K562 cells treated with trichosanthin were examined. Analysis of the cells by single laser flow cytometry showed the sub-G1 peak. DNA extracted from these cells formed a characteristic "ladder" on agarose gel electrophoresis. Under electromicroscope, typical morphological changes of apoptosis were also observed. From all of these findings, we concluded that trichosanthin was able to induce apoptosis in K562 cells. 相似文献
998.
电融合方法建立抗结核杆菌单克隆抗体细胞株 总被引:1,自引:0,他引:1
By using the electrofusion tecndque, the fusion of NSI myeloma cells with spleen cells of BALB / c mouse immunized with five species of mycobacteria was caaced cuL With the ophmal electrofUSion condihons, we obtained a high fuSion efficiency of l.75 hybrid cell clones per 105 spleen cells. ELISA was used for screening secrehng anhmycobacteria McAb hybrid cells. After cloning, 22 stable hybrid cells'lines were selected, and 8 of them had been studied. 相似文献
999.
用酶标免疫检测法研究了根瘤菌4012a菌株细胞分裂素发酵的适宜培养基和培养条件。结果表明,其最佳培养基为(g/L):葡萄糖10.0,(NH4)2SO41.0,K2HPO4·3H2O0.6,MgSO4·7H2O0.1,CaCl2·2H2O0.4,FeCI3·6H2O0.04,Na2MoO4·2H2O0.1mg/L,泛酸钙100μg/L,腺漂吟200mg/L。该菌株在150r/min的旋转摇床上27℃振荡培养96h,发酵液中细胞分裂素产量可达908μg/L,生物活性(萝卜子叶扩大法)为1mg/L激动素当量。 相似文献
1000.