全文获取类型
收费全文 | 16087篇 |
免费 | 41篇 |
国内免费 | 61篇 |
专业分类
系统科学 | 46篇 |
丛书文集 | 98篇 |
教育与普及 | 34篇 |
理论与方法论 | 44篇 |
现状及发展 | 7066篇 |
研究方法 | 742篇 |
综合类 | 7980篇 |
自然研究 | 179篇 |
出版年
2013年 | 137篇 |
2012年 | 264篇 |
2011年 | 415篇 |
2010年 | 104篇 |
2008年 | 254篇 |
2007年 | 309篇 |
2006年 | 285篇 |
2005年 | 300篇 |
2004年 | 306篇 |
2003年 | 276篇 |
2002年 | 275篇 |
2001年 | 525篇 |
2000年 | 473篇 |
1999年 | 348篇 |
1992年 | 317篇 |
1991年 | 238篇 |
1990年 | 267篇 |
1989年 | 243篇 |
1988年 | 257篇 |
1987年 | 275篇 |
1986年 | 207篇 |
1985年 | 325篇 |
1984年 | 245篇 |
1983年 | 213篇 |
1982年 | 218篇 |
1981年 | 181篇 |
1980年 | 225篇 |
1979年 | 536篇 |
1978年 | 409篇 |
1977年 | 385篇 |
1976年 | 350篇 |
1975年 | 397篇 |
1974年 | 437篇 |
1973年 | 416篇 |
1972年 | 448篇 |
1971年 | 478篇 |
1970年 | 605篇 |
1969年 | 477篇 |
1968年 | 507篇 |
1967年 | 467篇 |
1966年 | 444篇 |
1965年 | 296篇 |
1964年 | 86篇 |
1959年 | 142篇 |
1958年 | 265篇 |
1957年 | 177篇 |
1956年 | 155篇 |
1955年 | 140篇 |
1954年 | 123篇 |
1948年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
131.
Effects were examined of atropine, diazepam, pethidene, promethazine, scopolamine, omnopon and papaverine on basal and noradrenaline-stimulated lipolysis in rat isolated fat cells and on rat adipose tissue cyclic AMP phosphodiesterase activity. Papaverine at high concentration (1 mM) inhibited both basal and hormone-stimulated lipolysis, whereas diazepam enhanced basal lipolysis. At a 'clinical dose', omnopon increased both basal and noradrenaline-stimulated lipolysis. Adipose tissue cAMP phosphodiesterase activity was strongly inhibited by 1 mM diazepam, papaverine, promethazine and omnopon (280 microgram ml-1). Lack of enhancement of lipolysis by the established cAMP phosphodiesterase antagonist papaverine, is compatible with simultaneous inhibition also of adipose adenyl cyclase. Diazepam-stimulated lipolysis is compatible with its phosphodiesterase inhibitory activity. It is proposed that papaverine-containing omnopon may offer some survival advantages during surgical stress by facilitating a caloric supply. 相似文献
132.
A. B. Ślebodziński 《Cellular and molecular life sciences : CMLS》1979,35(4):549-550
Summary The effect of ethanol on thyroxine (T4) accumulation in the hypothalamus (H), pituitary gland (P) and cerebrospinal fluid (CSF) has been investigated in 1–15-day-old rabbits. It has been found that H or CSF serum ratios decreased with age by about 2 in the course of 13 postnatal days. Stable T4 resulted in an increase of125I-T4 in H, P and CSF. Ethanol per se caused an increase in transfer and accumulation of radiothyroxine or made the changes after loading animals with carrier T4 more pronounced. 相似文献
133.
B. Goldberg A. Stern J. Peisach W. E. Blumberg 《Cellular and molecular life sciences : CMLS》1979,35(4):488-489
Summary The low temperature EPR spectrum of a quickly reacted mixture of oxyhemoglobin and phenylhydrazine was studied. With the use of a computer, the spectral contribution of methemoglobin in the region of g=2 was subtracted. The remaining spectrum was that of an axial free radical (g=2.00, g=2.06) having the magnetic parameters of superoxide anion. In the presence of superoxide dismutase, this axial radical was not seen, confirming that superoxide anion is indeed generated by the reaction.The portion of this investigation carried out at the Albert Einstein College of Medicine was supported in part by US Public Health Service Research Grant HL-93399 from the Heart and Lung Institute and by National Institute Contract Nol-CP-55606 to J.P. This is communication No. 378 from the Joan and Lester Avnet Institute of Molecular Biology.Predoctoral fellow in the Medical Scientist Training Program (United States Public Health Service Grant 5-TO-5-GM 01669-12) at the New York University School of Medicine.Recipient of a grant-in-aid from the New York Heart Association. 相似文献
134.
135.
B. A. Battelle E. A. Kravitz H. Stieve 《Cellular and molecular life sciences : CMLS》1979,35(6):778-780
Summary Radiochemical precursor compounds for neurotransmitters were incubated withLimulus ventral nerve photoreceptor preparations. Octopamine was preferentially synthesized by a photoreceptor rich fraction of the nerve, acetylcholine was made by a photoreceptor poor fraction, and -aminobutyric acid was made about equally well in both fractions. The possibility that the ventral nerve photoreceptor cells serve a neurosecretory function in the adultLimulus is discussed.From the Neurobiology Course, Marine Biological Laboratory, Woods Hole, Mass. The Neurobiology Course is supported by grants from the Grass, Sloan and Sandoz Foundation and from Merck, Sharp and Dohme Research Institute. 相似文献
136.
Zusammenfassung Verabreichung von Isoprotenerol, eines -adrenergen Agonisten, induziert einen signifikant höheren Anstieg der Aktivität der Serotonin-N-Acetyltransferase in der Epiphyse von spontan hypertensiven, im Vergleich mit normotensiven, Rattenmännchen. Derselbe Unterschied wurde auch bei Weibchen beobachtet, jedoch liegen die Aktivitätswerte bei spontan hypertensiven Männchen allgemein höher. Die durch Isoprotenerol erhöhte Induktion der Serotonin-N-Acetyltransferase erzeugt hinsichtlich der Catecholamine in den Pinealozyten von spontan hypertensiven Ratten eine veränderte Reaktivität der Achse -Rezeptor-Adenylzyklasesystem-Serotonin-N-Acetyl transferase. 相似文献
137.
Summary The extra-DNA body was found, for the first time, in oocytes of an insect with telotrophic ovary. Dispersion of this body is accompanied by an enormous increase of nuclear volume and production of multiple nucleoli. It is suggested that the extra-DNA contains a huge mass of nucleolus organizers.This research was supported in part by funds from the Cytobiology Committee of the Polish Academy of Science. 相似文献
138.
P. Pani A. Sanna M. I. Brigaglia A. Columbano L. Congiu 《Cellular and molecular life sciences : CMLS》1976,32(11):1449-1451
Summary Acute toxicity induced by DMN was partially prevented by previously administering methyl mercuric chloride (MMC), a chemical inhibitor of the drug metabolizing enzyme system (DMES). We have studied the early changes occurring during the course of DMN-intoxication, namely disaggregation of polysomal profiles and necrosis, evaluated morphologically and by the release of S-GPT.This work was supported by Consiglio Nazionale delle Ricerche, Roma, Italy. 相似文献
139.
Summary The serum activities of aspartate aminotransferase, alanine aminotransferase, -hydroxybutyrate dehydrogenase and creatine phosphokinase have been measured in the African elephant. In general, the values were broadly comparable with those of man except that alanine aminotransferase was much lower and creatine phosphokinase higher. No variation due to age, sex, season or location was observed. 相似文献
140.