全文获取类型
收费全文 | 19232篇 |
免费 | 48篇 |
国内免费 | 114篇 |
专业分类
系统科学 | 90篇 |
丛书文集 | 254篇 |
教育与普及 | 96篇 |
理论与方法论 | 79篇 |
现状及发展 | 8055篇 |
研究方法 | 925篇 |
综合类 | 9594篇 |
自然研究 | 301篇 |
出版年
2013年 | 124篇 |
2012年 | 319篇 |
2011年 | 622篇 |
2010年 | 148篇 |
2009年 | 158篇 |
2008年 | 401篇 |
2007年 | 416篇 |
2006年 | 389篇 |
2005年 | 444篇 |
2004年 | 451篇 |
2003年 | 365篇 |
2002年 | 337篇 |
2001年 | 631篇 |
2000年 | 583篇 |
1999年 | 419篇 |
1992年 | 354篇 |
1991年 | 273篇 |
1990年 | 300篇 |
1989年 | 272篇 |
1988年 | 289篇 |
1987年 | 281篇 |
1986年 | 265篇 |
1985年 | 388篇 |
1984年 | 305篇 |
1983年 | 218篇 |
1982年 | 232篇 |
1981年 | 207篇 |
1980年 | 250篇 |
1979年 | 555篇 |
1978年 | 439篇 |
1977年 | 407篇 |
1976年 | 365篇 |
1975年 | 392篇 |
1974年 | 484篇 |
1973年 | 472篇 |
1972年 | 454篇 |
1971年 | 545篇 |
1970年 | 655篇 |
1969年 | 552篇 |
1968年 | 568篇 |
1967年 | 522篇 |
1966年 | 466篇 |
1965年 | 340篇 |
1959年 | 191篇 |
1958年 | 332篇 |
1957年 | 227篇 |
1956年 | 211篇 |
1955年 | 168篇 |
1954年 | 201篇 |
1948年 | 146篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
61.
Summary Behavioral arousal and fright responses ofHalichoeres bivittatus occurred in aquaria to a moving shadow and a tap stimulus. Arousal was characterized by changes in the beat of pectoral fins, dorsal fin erection and eye movements, whereas in fright, adduction of pectoral and dorsal fins and rapid forward movement occurred. Serial stimulus presentation caused the fright response to be replaced by arousal which habituated in that the proportion of behavioral components exhibited decreased during the process.P.R. Laming was in receipt of a Royal Society travel grant for assistance in the expenses of this work, for which he is duly grateful. We are grateful to Nick Zinkowski, Culebra for the loan of minnow traps. 相似文献
62.
F. M. Goñi J. M. Valpuesta M. C. Barbero E. Rial J. I. G. Gurtubay J. M. Macarulla 《Cellular and molecular life sciences : CMLS》1984,40(2):193-195
Summary The solubilizing effect of Triton X-100 on beef heart submitochondrial particles (ETPH) has been studied under various physiological conditions. Coupled, uncoupled and azide-inhibited ETPH particles have been studied. Quantitative and qualitative differences are found in the proteins solubilized by the detergent from ETPH particles under the various conditions tested.Acknowledgments: This work was supported in part by a grant from a Spanish Comisión Asesora para la Investigación Cientifica y Técnica. M.C. Barbero was recipient of a scholarship from the Basque Government. 相似文献
63.
E. Umapathy 《Cellular and molecular life sciences : CMLS》1984,40(12):1431-1433
Summary Administration of estradiol-17 elicited differential responses on accessory sex glands of rats. In caput epididymis, the estrogen treatment led to an accumulation of glycerides and phospholipids while in cauda epididymis, there was no significant change. However, in seminal vesicles, depletion of phospholipids was observed In prostate, the treatment, resulted in an accumulation of glycerides.Part of Ph.D. Thesis. Umapathy, E., Thesis. University of Madras, India, 1977. 相似文献
64.
D Viala E Freton 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1980,291(6):573-576
In curarized Rabbits whose cervico-thoracic cord has been isolated through C2 and Th12 transections, a pharmacological activation (nialamide-DOPA) disclosed distinct rhythmic efferent activities, locomotor-like bursts in forelimb muscle nerves and "respiratory" discharges in the phrenic nerves: they originate respectively from a cervico-thoracic locomotion generator and from a "respiration" generator; these spinal generators appear to be interconnected with each other. 相似文献
65.
At ambient temperatures (Ta) of both 8 and 22 degrees C, intraventricular administration of TRH (10-80 microgram) produced a dose-dependent hypothermia in rats. The hypothermia was due to both decreased metabolic heat production and cutaneous vasodilatation. In contrast, at 30 degrees C Ta, TRH increased metabolic heat production (due to behavioral excitation) and led to hyperthermia. 相似文献
66.
Summary The C-terminal amino acid sequences of human and of porcine antithrombin III have been determined as Gly-Arg-Val-Ala-Asn-Pro-Cys-Val-Lys and Gly-Arg-Val-Ala-Asn-Pro-Cys, respectively. These sequences are highly homologous with the C-terminal sequence of human -1-proteinase inhibitor. 相似文献
67.
Summary 2-Halogeno-ethanols change the active site structure of -chymotrypsin more rapidly and effectively than ethanol, 1-propanol and urea, probably before producing an extensive conformation change. 相似文献
68.
Summary The concentrations of testosterone (T) and 5-dihydrotestosterone were measured in fluid collected from the rete testis of immature and adult rats. The results indicate that adult levels of T are attained in the seminiferous tubules much earlier than in the peripheral circulation.This work was performed at the Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts, USA and supported by the National Institutes of Health through grants HD12641 and HD12642. We thank Dr B.V. Caldwell for antiserum to testosterone. 相似文献
69.
D. Sabourault Françoise Bauché Y. Giudicelli J. Nordmann R. Nordmann 《Cellular and molecular life sciences : CMLS》1981,37(3):227-229
Summary After 3 weeks of continuous ethanol intoxication by inhalation, the maximal number and affinity of the -and -receptors of rat heart were unchanged. These data indicate that adrenergic receptor disturbances are not involved in the mechanism of chronic ethanol-induced triglyceride deposition in the heart.Acknowledgments. This work was supported by grants from the Institut National de la Santé et de la Recherche Médicale. We wish to thank Mr M. Clément for skilled technical assistance in performing chronic ethanol inhalation treatments. 相似文献
70.
E. Knecht J. Renau-Piqueras J. Hernández-Yago S. Grisolía 《Cellular and molecular life sciences : CMLS》1981,37(5):456-457
Summary Protein from resting or phytohemagglutinin-stimulated human peripheral blood T-lymphocytes, pulse-labeled in vitro for 1 h with3H-leucine, had a half-life of 30 h. 相似文献