全文获取类型
收费全文 | 28932篇 |
免费 | 82篇 |
国内免费 | 159篇 |
专业分类
系统科学 | 139篇 |
丛书文集 | 499篇 |
教育与普及 | 42篇 |
理论与方法论 | 100篇 |
现状及发展 | 13472篇 |
研究方法 | 1292篇 |
综合类 | 13228篇 |
自然研究 | 401篇 |
出版年
2013年 | 272篇 |
2012年 | 420篇 |
2011年 | 817篇 |
2010年 | 170篇 |
2008年 | 526篇 |
2007年 | 585篇 |
2006年 | 583篇 |
2005年 | 537篇 |
2004年 | 541篇 |
2003年 | 500篇 |
2002年 | 504篇 |
2001年 | 936篇 |
2000年 | 865篇 |
1999年 | 616篇 |
1992年 | 596篇 |
1991年 | 414篇 |
1990年 | 486篇 |
1989年 | 494篇 |
1988年 | 460篇 |
1987年 | 546篇 |
1986年 | 474篇 |
1985年 | 596篇 |
1984年 | 484篇 |
1983年 | 364篇 |
1982年 | 340篇 |
1981年 | 370篇 |
1980年 | 462篇 |
1979年 | 889篇 |
1978年 | 757篇 |
1977年 | 740篇 |
1976年 | 611篇 |
1975年 | 632篇 |
1974年 | 845篇 |
1973年 | 756篇 |
1972年 | 779篇 |
1971年 | 840篇 |
1970年 | 1074篇 |
1969年 | 814篇 |
1968年 | 820篇 |
1967年 | 795篇 |
1966年 | 681篇 |
1965年 | 472篇 |
1964年 | 156篇 |
1959年 | 249篇 |
1958年 | 440篇 |
1957年 | 292篇 |
1956年 | 259篇 |
1955年 | 246篇 |
1954年 | 239篇 |
1948年 | 162篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
M. J. Kelly 《Cellular and molecular life sciences : CMLS》1981,37(8):889-890
Summary The relaxant effects of isoprenaline on rabbit isolated renal artery and aorta were compared. The results suggest that although isoprenaline acts on -adrenoceptors in the aorta it stimulates dopamine receptors in the renal artery. 相似文献
192.
R. L. Tyson C. -j. Chang J. L. McLaughlin Y. Aynehchi J. M. Cassady 《Cellular and molecular life sciences : CMLS》1981,37(5):441-442
Summary A novel sesquiterpene lactone, 9--hydroxyparthenolide (1) was isolated from a chloroform extract ofAnvillea garcini that was collected in Iran. The structure of1 was assigned on the basis of high field NMR decoupling experiments and other spectroscopic evidence. This -methylene lactone has shown significant activity in both the 9KB cell culture and P388 mouse leukemia test systems.The authors acknowledge the support of contract No. N01-CM-97296 from the National Cancer Institute and the use of the Purdue University Biochemical Magnetic Resonance Laboratory (NIH grant No. RR01077). This is paper 16 in the series Potential Antitumor Agents. 相似文献
193.
Y. Kakiuchi G. M. Hughes T. Arai M. Horimoto Y. Kikuchi T. Koyama 《Cellular and molecular life sciences : CMLS》1981,37(4):376-377
Summary A needle type of colloid osmometer has been devised with special attachments which made it useable with 3-l samples. It has been used in oncometry of fresh water teleosts to give the following results: 5.1±1.0 mm Hg for goldfish, 5.2±0.71 mm Hg for carp, and 14.3±0.75 mm Hg for eel.This study was supported in part by Research Grant 387036 from the Ministry of Education of Japan.invited to National Institute of Physiological Sciences, Okazaki, Japan. 相似文献
194.
Summary Autoradiographic, stereological and histological studies have been carried out to determine the origin of muscle fibre splitting which supposedly occurs during muscle hypertrophy. The results obtained clearly indicate that the supposedly split fibres are a transient response probably derived from satellite cells and are not derived from pre-existing fibres by true splitting. Similarly, increases in muscle fibre size are not achieved by recruitment of satellite structures as indicated by lack of myonuclear recruitment.Acknowledgment. This work was carried out with the aid of a grant from the Medical Research Council of Great Britain. The authors are grateful for the excellent technical assistance of Miss H. Caulton, M.J. Wild and M. Fenner. 相似文献
195.
Summary Thymidylate synthetase (methylenetetrahydrofolate: 2-deoxyuridine-5-monophosphate C-methyltransferase; EC 2.1.1.45) from neonatal mouse liver has been purified 714-fold by affinity chromatography on aminohexylsepharose bound 10-methyl-5,8-dideazafolate.Supported by grant CA22754, awarded by the National Cancer Institute, DHEW. 相似文献
196.
Summary Growth-promoting alpha-globulin (GPAG), a specific serum protein complex which induces mitotic activity in continually replicating metazoan cells in vitro, was shown in this study to support growth of astrocytes and mesenchymal cells as well as process formation of nerve cells isolated from cerebral hemispheres of chick embryos. 相似文献
197.
T. Ohhashi T. Miyazawa T. Azuma M. Sakaguchi 《Cellular and molecular life sciences : CMLS》1981,37(4):377-378
Summary The conduction velocity of peristaltic movements of the canine ureter was measured under anaesthesia with a new type of diameter gauge using an image sensor. The peristaltic velocity was 34.1±6.2 mm/sec in 10 experiments. Noradrenaline at a low dosage of 1 g/kg i.v. reduced the resting diameter, increased the conduction velocity to 47–56 mm/sec, and approximately doubled the frequency of contraction. The application of acetylcholine also caused an increase in both frequency and conduction velocity (42–46 mm/sec). A plot of the conduction velocity against the mean period of peristaltic contraction was hyperbolic in shape. 相似文献
198.
Summary -Galactosidase activity in intact cells of 21 species ofStreptomyces was measured using ONPG hydrolysis, without addition of a permeabilizing agent. Differences in the induction efficiency of ONPG-hydrolytic activity by lactose or galactose, which could have taxonomic implications, were observed among the species. 相似文献
199.
J. M. Saavedra 《Cellular and molecular life sciences : CMLS》1981,37(9):1002-1003
Summary Adult spontaneously hypertensive rats (SHR) are less sensitive to painful stimuli than their normotensive controls, Wistar-Kyoto (WKY) rats. This difference can be eliminated by the specific opiate antagonist, naloxone, and by the -adrenergic blocking agent, propranol.Acknowledgment. The author wishes to thank Miss R. L. Holcomb for her editorial assistance. 相似文献
200.
Summary A simple device is described, which permits us to quantify several parameters of spontaneous behaviour of small animals. Using this device with mice we obtained statistically satisfactory results, showing a strong genetic influence on the behavioural characteristics tested.We wish to thank Mr R. Laplace for technical help, Mr J. P. Arnould for electronic work as well as I.N.S.E.R.M.-SCR 3. 相似文献