全文获取类型
收费全文 | 24636篇 |
免费 | 137篇 |
国内免费 | 95篇 |
专业分类
系统科学 | 150篇 |
丛书文集 | 187篇 |
教育与普及 | 41篇 |
理论与方法论 | 124篇 |
现状及发展 | 10108篇 |
研究方法 | 1157篇 |
综合类 | 12662篇 |
自然研究 | 439篇 |
出版年
2016年 | 129篇 |
2013年 | 259篇 |
2012年 | 394篇 |
2011年 | 837篇 |
2010年 | 194篇 |
2008年 | 455篇 |
2007年 | 514篇 |
2006年 | 511篇 |
2005年 | 480篇 |
2004年 | 567篇 |
2003年 | 441篇 |
2002年 | 441篇 |
2001年 | 910篇 |
2000年 | 880篇 |
1999年 | 543篇 |
1992年 | 438篇 |
1991年 | 379篇 |
1990年 | 399篇 |
1989年 | 401篇 |
1988年 | 378篇 |
1987年 | 380篇 |
1986年 | 393篇 |
1985年 | 447篇 |
1984年 | 384篇 |
1983年 | 326篇 |
1982年 | 290篇 |
1981年 | 298篇 |
1980年 | 330篇 |
1979年 | 782篇 |
1978年 | 620篇 |
1977年 | 586篇 |
1976年 | 430篇 |
1975年 | 507篇 |
1974年 | 736篇 |
1973年 | 597篇 |
1972年 | 632篇 |
1971年 | 735篇 |
1970年 | 904篇 |
1969年 | 665篇 |
1968年 | 666篇 |
1967年 | 627篇 |
1966年 | 603篇 |
1965年 | 439篇 |
1959年 | 188篇 |
1958年 | 329篇 |
1957年 | 230篇 |
1956年 | 173篇 |
1955年 | 164篇 |
1954年 | 179篇 |
1948年 | 141篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
D. Lewinson M. Rosenberg M. R. Warburg 《Cellular and molecular life sciences : CMLS》1984,40(9):956-958
Summary Two types of mitochondria-rich cells (MRC) are described ultrastructurally in the gill epithelium of salamander larva. They resemble MRC found in larval ventral epidermis. Histochemical localization of carbonic anhydrase indicated numerous positive reacting cells, most of them flask-shaped. Morphological and functional similarities to fish chloride cells are discussed. 相似文献
132.
The cold dark interstellar Taurus Molecular Cloud One (TMC-1) is a rich source of acetylenic and polyacetylenic molecular species. As well as linear closed-shell molecules (H(C triple bond C)nCN) and symmetric rotors (CH3C triple bond CH, CH3C triple bond CCN), several radicals (C triple bond CH, C triple bond CCN, (C triple bond C2H) have also been identified, many of which had not been studied previously in the laboratory. Whether the observed abundances can be understood in terms of purely gas-phase ion-molecule chemical schemes, which produce reasonable agreement for the simplest polyatomic species, is unclear; alternative models involving the particulate interstellar grains as catalysts or sources have also been suggested. We now report the detection in TMC-1 of a new molecule, tricarbon monoxide (C3O), whose pure rotational spectrum has only very recently been studied in the laboratory. As C3O is the first known interstellar carbon chain molecule to contain oxygen, its existence places an important new constraint on chemical schemes for cold interstellar clouds. In fact, the observed abundance of tricarbon monoxide fits quite well into our model of galactochemistry. 相似文献
133.
134.
T. T. Yen J. A. Allan D. V. Pearson J. M. Acton 《Cellular and molecular life sciences : CMLS》1978,34(12):1542-1543
Summary Treating VY/WfL-A
vy
/a mice with 5-androstan-17-one, a mammalian glucose-6-phosphate dehydrogenase inhibitor, prevented the mice from becoming obese. The weight difference between treated and controlA
vy
/a mice was mainly due to a decreased accumulation of triacylglycerol. The compound did not suppress appetite, had no detectable toxicity and did not affect the lipogenesis rates in the liver and carcass. The weight-controlling effect of 5-androstan-17-one inA
vy
/a mice was reversible upon withdrawal of treatment.The authors wish to thank Mr W.R. Gibson and Drs C.G. Culbertson and P.N. Harris for performing the pathological examinations. 相似文献
135.
Summary The secondary disease in PF1 strain combination depends upon the immune status of both partners. It is most clearly expressed if both donors and recipients are immunologically crippled by thymectomy and irradiation. Conspicuous reduction in the immune potential of parental parabionts induced by thymectomy and irradiation displayed their marked incidence of parabiotic death. 相似文献
136.
H. Kemona J. Prokopowicz N. Wotosowicz 《Cellular and molecular life sciences : CMLS》1978,34(2):257-257
Summary It has been shown that there is a higher count of blood platelets and thrombopoietic activity of plasma in women than men. 相似文献
137.
C. N. Powell 《Cellular and molecular life sciences : CMLS》1978,34(11):1450-1451
Summary 9 groups of 6 female rats were used in an experiment using fraction 3 ofTrypanosoma rhodesiense. 500 g gave 100% immunoprotection and 1000 and 1500 g gave 66% immunoprotection when challenged with 5×102
T. brucei. 2 groups of 10 female rats were tested for a short period inoculation immune response. In this, 750 g of fraction 3 ofT. rhodesiense gave 70% immunoprotection when challenged withT. brucei.I thank the University of Zambia for support; Dr M. A. Q. Awan, Mazabuka, Zambia, forT. rhodesiense andT. brucei; Prof. J. W. Kibukamusoke, Dr O. Okong'o and Dr W. W. Anokbonggo for advice; Mr L. Nyaliti for technical help. 相似文献
138.
N. Michajlovskij V. Štrbák O. Földes 《Cellular and molecular life sciences : CMLS》1978,34(3):409-410
Summary The administration of thiocyanate to rats caused a significant increase of serum free thyroxine fraction, which coincided with the significant decrease of TSH level. The other components (AFT4, T4, T3) in serum at this time were decreased or unchanged. The finding suggests the role of free thyroxine fraction in feed-back regulation of TSH secretion.Acknowledgment. We thank Dr A. Parlow and the NIAMDD, Rat Pituitary Hormone Distribution Program, for material for rat TSH immunoassay; Dr J. Nauman (Inst. Postgrad. Med., Warsaw, Poland) for T3 antibody, and to Ing. J. Sadlo, Mrs M. t'astná and Miss R Fajkoová for technical assistance. 相似文献
139.
Summary The cytoplasm of the restrictive form of the amycelial mutant ofNeurospora crassa, growing on sucrosemedium, contains paracrystalline, microfilamentous inclusions and mitochondria with internal membranous whorls lacking in acetate-grown cultures.The support of the Fonds national suisse de la recherche scientifique is gratefully acknowledged. 相似文献
140.
D. K. Bhatt 《Cellular and molecular life sciences : CMLS》1978,34(12):1549-1550
Summary Phenylketonuric squirrels have shown marked inhibition of alkaline phosphatatase in the olfactory lobes and cerebral hemispheres, whereas the Na+-K+-ATPase remained less altered. In the pathogenesis of phenylketonuria inhibition of alkaline phosphatase at the level of Blood-Brain Barrier (BBB), leads transport system to impaired functioning.This work was done in the Department of Zoology, University of Udaipur, Udaipur-313001, India. 相似文献