全文获取类型
收费全文 | 30684篇 |
免费 | 68篇 |
国内免费 | 107篇 |
专业分类
系统科学 | 117篇 |
丛书文集 | 419篇 |
教育与普及 | 86篇 |
理论与方法论 | 115篇 |
现状及发展 | 14539篇 |
研究方法 | 1102篇 |
综合类 | 14168篇 |
自然研究 | 313篇 |
出版年
2013年 | 148篇 |
2012年 | 335篇 |
2011年 | 631篇 |
2008年 | 428篇 |
2007年 | 468篇 |
2006年 | 483篇 |
2005年 | 491篇 |
2004年 | 607篇 |
2003年 | 493篇 |
2002年 | 478篇 |
2001年 | 802篇 |
2000年 | 819篇 |
1999年 | 553篇 |
1994年 | 366篇 |
1992年 | 493篇 |
1991年 | 401篇 |
1990年 | 459篇 |
1989年 | 427篇 |
1988年 | 415篇 |
1987年 | 463篇 |
1986年 | 512篇 |
1985年 | 627篇 |
1984年 | 420篇 |
1983年 | 434篇 |
1982年 | 376篇 |
1981年 | 391篇 |
1980年 | 413篇 |
1979年 | 983篇 |
1978年 | 820篇 |
1977年 | 759篇 |
1976年 | 597篇 |
1975年 | 717篇 |
1974年 | 953篇 |
1973年 | 804篇 |
1972年 | 837篇 |
1971年 | 1046篇 |
1970年 | 1231篇 |
1969年 | 992篇 |
1968年 | 1005篇 |
1967年 | 927篇 |
1966年 | 786篇 |
1965年 | 613篇 |
1964年 | 229篇 |
1959年 | 340篇 |
1958年 | 600篇 |
1957年 | 454篇 |
1956年 | 371篇 |
1955年 | 362篇 |
1954年 | 366篇 |
1948年 | 273篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
Summary In a group of 5 women taking oral contraceptives, the concentration of polymorphonuclear leucocytes along the gingival margin and the activities of cathepsin D, -glucuronidase and elastase were found to increase significantly during the intermenstrual phases.Supported by grant 3.604.075 of the Swiss National Fund for scientific Research. The authors thank Dr M. Baggiolini and Prof. A. Linder for the helpful advices. 相似文献
242.
C Radanyi G Redeuilh E Eigenmann M C Lebeau N Massol C Secco E E Baulieu H Richard-Foy 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,288(2):255-258
The antibodies against estrogen receptor were obtained after injecting Rabbits with a cytoplasmic receptor fraction isolated from Calf uterus. The estrogen receptor was partially proteolysed by the action of trypsin and subsequently purified by affinity chromatography (purification 4,000 to 10,000 fold, to a purity of 5-20%). The affinity of the antibody for the proteolysed receptor is KD approximately 1 nM and serum titres have reached values of approximately 50 nM. The values remained constant after the third injection. Preliminary results indicate that the antibody has approximately the same affinity for "native" cytoplasmic estrogen receptor from Calf uterus, as well as for the "trypsinized" forms of estrogen receptor isolated from Calf uterine cytosol and Hen oviduct nuclei. 相似文献
243.
A Nu?ez-Roldan A Arnaiz-Villena G Nu?ez-Ollero 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,288(23):1719-1720
In 10 sibships of haemophilic A patients, every one including 1 haemophilic brother with an antibody to factor VIII and 1 haemophilic brother without antibody, pattern of HLA segregation was analysed. All sibships were HLA haploidentical or different and not HLA identical. This fact suggested a linkage between the major histocompatibility complex and an "Ir" gene to factor VIII. 相似文献
244.
Summary The active calcium transport along the small intestine of adult rat was shown to exhibit daily rhythmic variations of considerable amplitude. Both the light-dark cycle and the time of food presentation acted as synchronizers of the rhythm observed.This work has been supported by Polish Academy of Sciences within the project MR II.1.1.6. 相似文献
245.
Streptozotocin diabetic rats were infertile as a result of decreased Leydig cell function of the testes. The major changes found were: decreased number of Leydig cells and their spontaneous secretion of testosterone. No change in the receptors to LH on the Leydig cells was observed. LH was found to be obligatory for the regulation of Leydig cell function and fertility. 相似文献
246.
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
247.
Using an automated system for the analysis of amylase, the release of this enzyme was compared in superfused parotid gland segments from control and reserpine treated rats. Stimulant-evoked amylase release was delayed and of smaller magnitude in the glands of the treated animals and a reduction of the transmembrane K+ gradient caused a smaller and short lasting reduction in Ach-evoked release of amylase in the glands from these animals. 相似文献
248.
Summary The D-galactose specific lectin fromViscum album L. reacts with serum proteins that contain the corresponding D-galactopyranosyl residues. By affinity chromatography of human serum on lectin-sepharose IgM, 2-macroglobulin, haptoglobin and -lipoprotein were quantitatively retained. Only parts of IgA, IgG and transferrin were retarded. The other serum proteins are unbounded as albumin, 1A– and 1C. 相似文献
249.
A. Matsuo H. Nozaki H. Kataoka M. Nakayama S. Hayashi 《Cellular and molecular life sciences : CMLS》1979,35(10):1279-1280
Summary A new enantiomeric sesquiterpene alcohol named (–)-maalian-5-ol was isolated from the liverwort, and the structure and absolute configuration was determined to be the stereostructureI by chemical and spectral evidence.The authors express their gratitude to Dr H. Inoue, National Science Museum, for identification of the liverwort, and Prof. T. Tokoroyama, Osaka City University, for sending of the data of (–)--maaliene and (+)-selina-5,11-diene. Thanks are also due to the Ministry of Education for financial support of this work. 相似文献
250.
Three acidic polysaccharide (AP) fractions and the prostaglandin-like substances (PLS) isolated from P. acnes were investigated regarding their chemotactic activities on polymorphonuclear leukocytes. Both AP's and PLS induced a significant chemotatic response, which suggests their involvement in inflammatory acne vulgaris. 相似文献