全文获取类型
收费全文 | 21441篇 |
免费 | 2054篇 |
国内免费 | 3581篇 |
出版年
2024年 | 58篇 |
2023年 | 263篇 |
2022年 | 608篇 |
2021年 | 985篇 |
2020年 | 771篇 |
2019年 | 977篇 |
2018年 | 930篇 |
2017年 | 721篇 |
2016年 | 935篇 |
2015年 | 1373篇 |
2014年 | 1705篇 |
2013年 | 1686篇 |
2012年 | 2136篇 |
2011年 | 1923篇 |
2010年 | 1250篇 |
2009年 | 1151篇 |
2008年 | 1383篇 |
2007年 | 1221篇 |
2006年 | 1183篇 |
2005年 | 947篇 |
2004年 | 812篇 |
2003年 | 789篇 |
2002年 | 599篇 |
2001年 | 321篇 |
2000年 | 305篇 |
1999年 | 288篇 |
1998年 | 212篇 |
1997年 | 170篇 |
1996年 | 150篇 |
1995年 | 116篇 |
1994年 | 118篇 |
1993年 | 77篇 |
1992年 | 98篇 |
1991年 | 78篇 |
1990年 | 74篇 |
1989年 | 66篇 |
1988年 | 45篇 |
1987年 | 38篇 |
1986年 | 37篇 |
1985年 | 48篇 |
1984年 | 53篇 |
1983年 | 37篇 |
1982年 | 38篇 |
1981年 | 43篇 |
1980年 | 24篇 |
1979年 | 26篇 |
1978年 | 23篇 |
1977年 | 24篇 |
1975年 | 23篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Marie Salomonsson Bo Carlsson Johan Hggblad 《The Journal of steroid biochemistry and molecular biology》1994,50(5-6):313-318
It is generally accepted that the Kd for hormone binding to estrogen receptors in extracts ranges between 0.1–1 nM and that binding displays positive cooperativity due to formation of homodimers. After carefully optimizing assay procedures, to diminish ligand depletion phenomena and to fully control recoveries, we find a single class of non-interacting high affinity hormone binding sites with a Kd of approx. 10 pM. Ligand depletion was avoided by decreasing receptor concentrations to 5–8 pM. We were therefore obliged to employ radioiodinated estradiol as a probe as the specific radioactivity of tritiated estradiol was too low to maintain the accuracy of the binding assay. Human estrogen receptor extracted from the MCF7 cell line and recombinantly produced (in yeast) wild-type human receptor have identical equilibrium hormone binding characteristics. 相似文献
102.
采用光亲和技术检测了血管活性肠多肽(VIP)与核苷酸之间的相互作用,发现VIP可以特异性结合同位素标记的GTP,还发现未标记的GTP以及其它三磷酸核苷抑制这种结合,这意味着VIP与上述三磷酸核苷之间的结合是一种典型的可逆性的结合反应.发现低浓度的GDP,GMP不但不抑制VIP与同位素标记GTP的结合反应,反而增强这种结合.联系到其它研究者关于GTP影响VIP与其受体结合反应的结果,可认为VIP能可逆性地连接一种三磷酸核苷,这种连接受反应系统中不同核苷酸比例影响,通过这种连接来调节VIP与其受体之间的反应. 相似文献
103.
沈阳西部污灌水中有机污染物的分析刘海玲,张丽珊,姚家彪,于殿臣,朱岩,可夫,姜萍(中国科学院沈阳应用生态研究所,110015)AnalysisofOrganicPollutantsinIrrigatedsewageInWesternShenyang.... 相似文献
104.
Two experiments were designed to evaluate the responsiveness of beef heifers to superstimulatory treatments administered during the first follicular wave. Heifers were examined daily (Experiment 1) or twice daily (Experiment 2) by ultrasonography to determine the status of follicular wave development and the day of initiation of superstimulatory treatment. Heifers in both experiments were superstimulated with a total dose of 10 ml Folltropin (equivalent to 200 mg of NIH-FSH-P1), divided into 10 equal intramuscular injections over 5 days. On the last day of treatment, heifers received 500 mug of cloprostenol after each injection of Folltropin to induce luteolysis. In the respective groups, superstimulatory treatments were initiated on Day -1, Day 0 (day of ovulation) or Day +1 for Experiment 1, and on Day -1, Day 0, Day +1 or Day +2 for Experiment 2. In Experiment 1, the number of ovulations in each ovary was assessed by ultrasonography and by counting the number of corpora lutea (CL) in each ovary at slaughter. The correlation between both techniques for assessing ovulatory response was high (r= 0.98; P< 0.0001), and there was no significant difference in the mean number of ovulations detected by ultrasound (5.7+/-1.1) versus the mean number of CL counted at slaughter (6.2+/-1.2). In Experiment 1, the mean (+/- SEM) number of CL counted at slaughter in heifers treated on Day -1 (9.4+/-3.8) and Day 0 (7.3+/-1.6) was higher (P< 0.05) than that of heifers treated on Day +1 (0.7+/-0.3). The mean number of follicles >/=7 mm in diameter on the last day of treatment was also higher (P<0.05) in the Day -1 group compared with the Day +1 group; the Day 0 group was intermediate. In Experiment 2, the mean number of ovulations was higher (P< 0.05) in the Day 0 group (18.4+/-3.4) than the Day -1 (9.5+/-2.3), Day +1 (6.7+/-2.2) or Day +2 (6.5+/-2.3) groups. Heifers in the Day -1, and Day 0 groups had more (P< 0.05) follicles >/=7 mm at the end of treatment compared with heifers in the Day +1 or the Day +2 group. The stated hypothesis was supported: exogenous FSH treatment initiated at the time of wave emergence, near the expected time of the endogenous wave-eliciting FSH surge, has a positive effect on the superstimulatory response. A higher superstimulatory response was elicited when treatments were initiated on the day of, or the day before, wave emergence compared with that of later treatments. 相似文献
105.
A study was performed to investigate possible interactions by magnetic fields (MF) with the processes of initiation and promotion of chemically induced preneoplastic lesions in rat liver. Male Sprague-Dawley rats were subjected to a 70% partial hepatectomy followed after 24 h by i.p. injection of diethylnitrosamine (DENA) as a tumour initiator. Starting one week after the DENA-treatment phenobarbital (PB) was given to promote growth of enzymatically altered foci of liver cells. MF was applied immediately after the partial hepatectomy and continued until sacrifice after 12 weeks of PB exposure. Homogenous horizontal AC magnetic fields with a frequency of 50 Hz and flux densities of 0.5 μT or 0.5 mT were used. The rats coexposed with MF and DENA plus PB did not gain weight as much as the rats exposed to the chemical agents only. The MF-exposure also resulted in a slight reduction in size and numbers of the focal lesions. The results suggest an interaction of MF with the processes of chemical carcinogenesis either as a result of stress or depending on effects on the proliferation of preneoplastic cells. © 1993 Wiley-Liss, Inc. 相似文献
106.
观察了hFPIL6/2对6.5Gyγ线照射NIH小鼠第10天造血功能恢复的影响。结果表明:照射小鼠连续4d给予hFPIL6/2250μg·kg-1·d-1,其脾重、CFU-8、骨髓有核细胞数及CM-CFU分别比对照组增加59.0%、278.5%、57.9%和138.2%,统计学处理均有显著差异;对此四项指标的改善也明显优于25μg组。另外,250μg剂量组小鼠外周血象30d的动态观察结果表明,hFPIL6/2不但能明显提高红细胞和血红蛋白的最低值,而且能使血小板的恢复提前。提示hFPIL6/2在促进血小板生成和促进红系造血方面可能具有良好的应用前景。 相似文献
107.
异质性荧光染色的巨噬细胞功能研究I.异质性荧光染色的巨噬细胞吞噬活性 总被引:1,自引:1,他引:0
利用淀粉多糖和免疫促进剂(白喉类毒素和卡介苗)诱导和活化小鼠腹腔巨噬细胞,观察了四种异质性荧光染色的巨噬细胞非特异性和特异性吞噬活性。实验证明,深蓝色和淡蓝色荧光的巨噬细胞是分化程度低的幼稚细胞,非特异性吞噬功能较弱,但在特异性吞噬过程中呈现了活跃的吞噬活性,特别是在免疫促进剂的活化下,它们的特异性吞噬功能显著增强、淡蓝绿色荧光的巨噬细胞是分化程度较高、非特异性和特异性吞噬功能最旺盛的巨噬细胞,而黄色荧光的巨噬细胞是分化程度最高、特异性吞噬功能较减退的巨噬细胞。 相似文献
108.
穴位激光照射对兔子宫类固醇激素受体的影响 总被引:1,自引:0,他引:1
对兔用He-Ne激光照射穴位,照射外生殖器,用类固醇激素受体测定法测定子宫雌二醇受体(ER)和孕酮受体(PR)含量。照射穴位后部分实验组的ER和PR浓度上升,与正常对照组相比较有显著或极显著差别(P<0.05,P<0.01),ER提高1.7-3.2倍,PR提高2.7-3.7倍。实验结果提示激光可通过类固醇激素受体浓度的提高,在受体水平上影响机体代谢。 相似文献
109.
通过对80例急性脑出血死亡组分析,发现死于脑疝的占62.5%,脑疝与一种或二种以上合并症同存者占77.5%,显著高于存活组(P<0.01).它们互为因果,加速死亡。因此,应重视早期或超早期采用简易定向锥颅脑内血肿碎吸术吸除血肿,同时注意维持生命体征稳定,加强脱水降颅压,预防、控制合并症等综合治疗。且要全面分析,相互兼顾,正确处置。这是帮助机体渡过调控障碍难关,挽救生命的有效治疗措施。 相似文献
110.
Bo Skaaning Jensen Flemming Jessen Else K. Hoffmann 《The Journal of membrane biology》1993,131(3):161-178
Summary Net Cl– uptake as well as unidirectional36Cl influx during regulatory volume increase (RVI) require external K+. Half-maximal rate of bumetanide-sensitive36Cl uptake is attained at about 3.3mm external K+. The bumetanide-sensitive K+ influx found during RVI is strongly dependent on both Na+ and Cl–. The bumetanide-sensitive unidirectional Na+ influx during RVI is dependent on K+ as well as on Cl–. The cotransporter activated during RVI in Ehrlich cells, therefore, seems to transport Na+, K+ and Cl–. In the presence of ouabain and Ba+ the stoichiometry of the bumetanide-sensitive net fluxes can be measured at 1.0 Na+, 0.8 K+, 2.0 Cl– or approximately 1 : Na, 1 : K, 2 : Cl. Under these circumstances the K+ and Cl– flux ratios (influx/efflux) for the bumetanide-sensitive component were estimated at 1.34 ±0.08 and 1.82 ± 0.15 which should be compared to the gradient for the Na+, K+, 2Cl– cotransport system at 1.75 ± 0.24.Addition of sucrose to hypertonicity causes the Ehrlich cells to shrink with no signs of RVI, whereas shrinkage with hypertonic standard medium (all extracellular ion concentrations increased) results in a RVI response towards the original cell volume. Under both conditions a bumetanide-sensitive unidirectional K+ influx is activated. During hypotonic conditions a small bumetanide-sensitive K+ influx is observed, indicating that the cotransport system is already activated.The cotransport is activated 10–15 fold by bradykinin, an agonist which stimulates phospholipase C resulting in release of internal Ca2+ and activation of protein kinase C.The anti-calmodulin drug pimozide inhibits most of the bumetanide-sensitive K+ influx during RVI. The cotransporter can be activated by the phorbol ester TPA. These results indicate that the stimulation of the Na+, K+, Cl– cotransport involves both Ca2+/calmodulin and protein kinase C. 相似文献