全文获取类型
收费全文 | 21044篇 |
免费 | 34篇 |
国内免费 | 74篇 |
专业分类
系统科学 | 81篇 |
丛书文集 | 171篇 |
教育与普及 | 55篇 |
理论与方法论 | 64篇 |
现状及发展 | 8878篇 |
研究方法 | 941篇 |
综合类 | 10650篇 |
自然研究 | 312篇 |
出版年
2013年 | 120篇 |
2012年 | 293篇 |
2011年 | 609篇 |
2010年 | 135篇 |
2008年 | 327篇 |
2007年 | 402篇 |
2006年 | 351篇 |
2005年 | 404篇 |
2004年 | 384篇 |
2003年 | 365篇 |
2002年 | 368篇 |
2001年 | 694篇 |
2000年 | 705篇 |
1999年 | 489篇 |
1994年 | 312篇 |
1992年 | 447篇 |
1991年 | 353篇 |
1990年 | 396篇 |
1989年 | 357篇 |
1988年 | 358篇 |
1987年 | 369篇 |
1986年 | 338篇 |
1985年 | 478篇 |
1984年 | 345篇 |
1983年 | 298篇 |
1982年 | 288篇 |
1981年 | 260篇 |
1980年 | 290篇 |
1979年 | 682篇 |
1978年 | 528篇 |
1977年 | 480篇 |
1976年 | 417篇 |
1975年 | 458篇 |
1974年 | 494篇 |
1973年 | 462篇 |
1972年 | 531篇 |
1971年 | 567篇 |
1970年 | 694篇 |
1969年 | 565篇 |
1968年 | 581篇 |
1967年 | 536篇 |
1966年 | 519篇 |
1965年 | 336篇 |
1959年 | 174篇 |
1958年 | 317篇 |
1957年 | 211篇 |
1956年 | 175篇 |
1955年 | 152篇 |
1954年 | 141篇 |
1948年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A El Abed M Valens Y Langlois B Kerdelhue 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,285(16):1483-1486
In a sensitive strain of Rat (Sprague-Dawley) a deregulation of the secretion of some pituitary hormones was noted in the female during induction of mammary tumors by dimethylbenzanthracene administration. The deregulation occurred quickly and depended on the stage of the estrous cycle. It mainly consists of hyposecretion of gonadotropins. TSH and GH and of hypersecretion of prolactin. 相似文献
993.
M T Bluet-Pajot C Schaub 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(23):1707-1710
The authors investigated basal levels of plasma immunoreactive growth-hormone in the rat (R-GH) after administration of 3 different anesthetic drugs: urethan, chloral hydrate and gamma-hdroxy-butyrate (GHB). Lowest R-GH concentrations (5 +/- 3 ng/ml) are observed after urethan; they are significantly higher (15 +/- 4 ng/ml) after chloral hydrate but this anesthetic also causes hyperglycemia (210 +/- 30 mg/100 ml). Normal blood glucose levels are observed under GHB narco-analgesia which elicits a clear-cut R-GH secretory episode (70 +/- 5 ng/ml); basal values (12 +/- 3 ng/ml) are maintained for several hours thereafter. 相似文献
994.
B Font C Vial D Goldschmidt D C Gautheron 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,288(3):367-340
Restoration of blood flow after 15 or 45 min. of ischemia induced an immediate recovery of phosphocreatine level and adenylate energy charge whereas ATP and total adenine nucleotides remained significantly below their normal values. These results prove that oxidative phosphorylations are not impaired but that a pool of myocardial adenine nucleotides is lost during ischemia which cannot be restored shortly after reperfusion. The significance of energy charge as a regulatory parameter in the myocardium is discussed. 相似文献
995.
This paper reviews research that makes use of one of the most popular forecasting methods applied in accounting: time-series analysis using the Box-Jenkins methodology. It organizes the research in the area, surveys recent applications of time-series analysis in accounting, and discusses the potential for the methodology in addressing future research issues. The emphasis is on those aspects of the accounting system that possibly cause difficulties in applying time-series methods in accounting. 相似文献
996.
B No?l-Courtey E Heinen 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,285(4):385-387
Chick embryo nerve cells from the lumbo-sacral spinal cord have been isolated by trypsinisation and cultivated in Rose chambers on polylysine-L as a substrate. The cells are analysed by scanning electron microscopy. The mode of adherence of these cells to the substrate and the modifications of the surface of the neuroblasts during their transformation into neurocytes are studied. 相似文献
997.
998.
999.
A new diagram for discriminating a forecasting technique's history with respect to the two types of turning-point errors, missed turns and false signals is presented. This diagram extends Theil's original prediction-realization (P-R) presentation so that each of the four quadrants and the axes locates a distinct type of forecasting error or correct forecast, thus reducing much of the former ambiguity. This improvement is accomplished without the loss of any information. 相似文献
1000.