全文获取类型
收费全文 | 334803篇 |
免费 | 37377篇 |
国内免费 | 190篇 |
专业分类
372370篇 |
出版年
2018年 | 2858篇 |
2017年 | 2722篇 |
2016年 | 3910篇 |
2015年 | 5377篇 |
2014年 | 6293篇 |
2013年 | 8829篇 |
2012年 | 10081篇 |
2011年 | 10061篇 |
2010年 | 6856篇 |
2009年 | 6208篇 |
2008年 | 8933篇 |
2007年 | 9380篇 |
2006年 | 8673篇 |
2005年 | 8346篇 |
2004年 | 8064篇 |
2003年 | 7833篇 |
2002年 | 7819篇 |
2001年 | 18187篇 |
2000年 | 18412篇 |
1999年 | 14131篇 |
1998年 | 4250篇 |
1997年 | 4517篇 |
1996年 | 4315篇 |
1995年 | 4015篇 |
1994年 | 3952篇 |
1993年 | 3786篇 |
1992年 | 11506篇 |
1991年 | 11155篇 |
1990年 | 10710篇 |
1989年 | 10277篇 |
1988年 | 9516篇 |
1987年 | 8872篇 |
1986年 | 8107篇 |
1985年 | 7994篇 |
1984年 | 6418篇 |
1983年 | 5608篇 |
1982年 | 4118篇 |
1981年 | 3622篇 |
1980年 | 3368篇 |
1979年 | 6131篇 |
1978年 | 4595篇 |
1977年 | 4155篇 |
1976年 | 3784篇 |
1975年 | 4349篇 |
1974年 | 4524篇 |
1973年 | 4407篇 |
1972年 | 4112篇 |
1971年 | 3520篇 |
1970年 | 3183篇 |
1969年 | 2993篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
T N Ul'masov M K Gulov K A Aliev V M Andrianov E S Piruzian 《Molekuliarnaia genetika, mikrobiologiia i virusologiia》1989,(8):17-20
The fragments of cotton Gossipium hirsutum c.v. 108-f chloroplast genome were cloned in Escherichia coli cells. The cloned psbA and rbcL genes have been selected using the heterologous probes from spinach. The preliminary attempts to clone the complete psbA gene in pUC19 vector failed, probably, due to the toxicity of its product to Escherichia coli cells, and its 5'- and 3'-ends were cloned separately. Reconstruction experiments revealed that while the complete psbA gene was unable to be stably inherited by Escherichia coli cells, its structural part lacking the promoter region could be readily cloned in the bacterial cells. 相似文献
992.
Isolation and characterization of eceriferum (cer) mutants induced by T-DNA insertions in Arabidopsis thaliana 总被引:2,自引:0,他引:2
Thirteen Arabidopsis thaliana mutants with deviating epicuticular wax layers (i.e., cer mutants) were isolated by screening 13 000 transformed lines produced by the seed transformation method. After crossing the 13 mutants to some of the previously known cer mutant lines, 12 of our mutants mapped to 6 of the 21 known complementation groups (cer1 through cer4 as well as cer6 and cer10), while the other mutant corresponded to a previously unknown locus, cer21. Mutant phenotypes of 6 of the 13 mutant lines were caused by T-DNA insertions within cer genes. We also analyzed the chemical composition of the epicuticular wax layers of the cer mutants isolated in this study relative to that of Arabidopsis wild-type plants. Our results suggest that the five genes we tagged regulate different steps in wax biosynthesis, i.e., the decarbonylation of fatty aldehydes to alkanes, the elongation of hexacosanoic acid to octacosanoic acid, the reduction of fatty aldehydes to primary alcohols and the production of free aldehydes, while an insertion in the fifth gene causes an alteration in the chain length distribution of the different classes of wax compounds. 相似文献
993.
994.
995.
996.
The level of urine selenium in healthy adult population, 230 persons, was examined. Persons were selected regarding sex, ages, and smoking habits. No differences versus these observations have been found. For a total, group values are 16.96 Se nmol/creatinine mmol, SD=5.44. It is possible from a single-void specimen to express daily excretion of selenium. 相似文献
997.
Administration of high-dose Antide to ovariectomized monkeys results in rapid, prolonged, and reversible inhibition of gonadotropin secretion. The present study examined whether similar long-term control would be manifested in the menstrual cycle of intact primates. Antide administration at a dose of either 3.0 or 18.0 mg/kg induced rapid suppression of bioassayable LH concentrations, precipitating a concurrent fall in serum progesterone concentrations from 7.9 +/- 3.6 and 5.8 +/- 1.0 ng/ml (mean +/- SEM) on the day of injection to 0.6 +/- 0.2 and 0.5 +/- 0.1 ng/ml by 2 days post-treatment, respectively. This Antide-induced luteolysis was accompanied by the premature onset of menses within 3 days. The next menses following Antide administration was delayed. Ultimately, folliculogenesis culminating in normal follicular-phase estradiol production, ovulation, and subsequent normal luteal-phase progesterone production did occur in all treated monkeys. Menses resumed 54 +/- 9 and 75 +/- 13 days after treatment with 3.0 and 18.0 mg/kg Antide, respectively. No allergic cutaneous or peripheral reactions were seen, even at the highest dose of Antide. Thus, the long duration of action of high-dose Antide reported earlier in ovariectomized monkeys is also demonstrated in intact primates. These findings, along with the apparent absence of histamine-release effects even at high doses, suggest that Antide is a GnRH antagonist deserving clinical evaluation. 相似文献
998.
999.
1000.