全文获取类型
收费全文 | 376739篇 |
免费 | 44520篇 |
国内免费 | 520篇 |
专业分类
421779篇 |
出版年
2018年 | 3220篇 |
2017年 | 3061篇 |
2016年 | 4161篇 |
2015年 | 5364篇 |
2014年 | 6601篇 |
2013年 | 8867篇 |
2012年 | 10193篇 |
2011年 | 10362篇 |
2010年 | 6841篇 |
2009年 | 6605篇 |
2008年 | 9166篇 |
2007年 | 9339篇 |
2006年 | 9148篇 |
2005年 | 8718篇 |
2004年 | 8542篇 |
2003年 | 8405篇 |
2002年 | 8153篇 |
2001年 | 23754篇 |
2000年 | 23728篇 |
1999年 | 18157篇 |
1998年 | 5086篇 |
1997年 | 5476篇 |
1996年 | 5032篇 |
1995年 | 4562篇 |
1994年 | 4461篇 |
1993年 | 4489篇 |
1992年 | 13645篇 |
1991年 | 13440篇 |
1990年 | 12560篇 |
1989年 | 12430篇 |
1988年 | 11482篇 |
1987年 | 10491篇 |
1986年 | 9484篇 |
1985年 | 9325篇 |
1984年 | 7241篇 |
1983年 | 6341篇 |
1982年 | 4545篇 |
1981年 | 3947篇 |
1980年 | 3735篇 |
1979年 | 6668篇 |
1978年 | 5160篇 |
1977年 | 4686篇 |
1976年 | 4142篇 |
1975年 | 4673篇 |
1974年 | 4891篇 |
1973年 | 4854篇 |
1972年 | 4290篇 |
1971年 | 3998篇 |
1970年 | 3466篇 |
1969年 | 3321篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
902.
T M Zheltikova V M Berzhets A D Petrova-Nikitina A Kh Kanchurin 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1986,(6):80-83
The acarological+ study of dust samples from the homes of allergic patients and normal persons in Moscow mite antigens were detected, respectively, in 66.7% and 38.1% of homes. The indirect mast cell degranulation test and the brain gliacyte volume change test in white rats gave similar results. The occurrence of Dermatophagoides pteronyssinus was approximately twice as great of D. farinae, and the numerical prevalence of the former species over the latter one was 1.3-fold. Dermatophagoides mites occurred in the homes of allergic patients 1.8-2.3 times as frequently as in the homes of normal persons. 相似文献
903.
904.
Summary The rhizosphere microflora of arecanut palm under continuous application of organic manures and inorganic fertilizers was
studied. The nutrients applied are 100 g N, 40 g P2O5 and 140 g K2O/palm/year in the form of organics and inorganics. The application of organic manure increased the microbial population.
The increase in microbial population was observed between the rhizosphere samples collected at 0–30cm and 30–60 cm depths.
The surface cultivation of soil increased the microbial population.Trichoderma sp. andAspergillus sp. dominated in therhizosphere of arecanut palm.
Contribution No. 208. Central Plantation Crops Research Institute, Vittal-574243, Karnataka, India. 相似文献
905.
Auromomycin and macromomycin from the organism Streptomyces macromomyceticus have been crystallized. The X-ray diffraction pattern of crystals of each molecule is consistent with space group P21212 with cell parameters for auromomycin, and for macromomycin. Diffraction analysis of auromomycin is in progress. 相似文献
906.
907.
S A Magder G T Daughters J Hung E L Alderman N B Ingels 《European journal of applied physiology and occupational physiology》1987,56(4):467-473
The purpose of this study was to measure the changes and rates of adaptation of left ventricular volumes at the onset of exercise. Eight asymptomatic subjects, in whom intramyocardial markers had been implanted 3-6 years previously during aortocoronary bypass surgery, exercised in the supine position at a constant workload of 73.6 W for 5 min. Six also exercised first at 16.4 W, and then against a workload which progressively increased by 8.2 W every 15 s. Cardiac volumes were measured by computer assisted analysis of the motion of the implanted markers. In the constant workload test, cardiac output increased rapidly from 5.7 +/- 1 min-1 to 10.3 +/- 1.9 1 min-1 by 2 min and then increased more slowly to 10.8 +/- 2.0 1 min-1 by 5 min. The cardiac output increase was mainly due to an increase in heart rate from 68 +/- 12 beats min-1 to 120 +/- 16 beats min-1 with minimal changes in stroke volume. The time constant for the early increase in cardiac output was 45s and for heart rate, 35s. With progressively increasing workloads, there was an almost linear increase of heart rate and cardiac output, but these increased at a slower rate than during the early phase of the constant load exercise test. In conclusion: rapid changes in cardiac output during supine exercise were produced by changes in heart rate; changes in stroke volume provided minor adjustments to cardiac output; the end-diastolic volume was almost constant. 相似文献
908.
W I Gudim T G Sukiasowa W S Iwanowa N A Gorbunowa G I Kosinez 《Folia haematologica (Leipzig, Germany : 1928)》1987,114(6):834-844
Fraction F1 with a MW of 5.10(3)-5.10(4), which had been isolated from the blood serum of blood donors as controls and patients at the terminal stage of chronic kidney insufficiency, specifically inhibited the erythropoiesis of test animals at the stage sensitive to erythropoietin and morphologically distinguishable cells of the bone-marrow. In uremia, protein concentration was twice higher in comparison to the normal one. The inhibiting effect of fraction F1 from the serum of patients is caused by the enlargement of level of physiological inhibitors and unspecific toxins of the cell proliferation. Those data characterising the factor detected in the fraction F1 of normal serum together with the erythrocytic chalon are discussed. 相似文献
909.
The presence of 3H-orotic acid in the cytoplasmic receptor fraction isolated in our laboratory, the sensitivity of this fraction to treatment with RNAases accompanied by a shift of the absorption peak of the receptor preparation towards the long-wave region as well as the use of the absorption filter technique point to the existence of ternary thyroxine-thyroxine-binding protein-RNA complex in the cytoplasm. It was found that the cytoplasmic hormone-receptor complex of thyroxine is a genetically active form which can interact with the nuclei and modify the activity of chromatin. The role of RNA in these interactions is discussed. 相似文献
910.