全文获取类型
收费全文 | 24539篇 |
免费 | 60篇 |
国内免费 | 103篇 |
专业分类
系统科学 | 82篇 |
丛书文集 | 219篇 |
教育与普及 | 91篇 |
理论与方法论 | 71篇 |
现状及发展 | 10840篇 |
研究方法 | 984篇 |
综合类 | 12097篇 |
自然研究 | 318篇 |
出版年
2012年 | 303篇 |
2011年 | 604篇 |
2009年 | 144篇 |
2008年 | 382篇 |
2007年 | 440篇 |
2006年 | 406篇 |
2005年 | 436篇 |
2004年 | 475篇 |
2003年 | 431篇 |
2002年 | 424篇 |
2001年 | 766篇 |
2000年 | 775篇 |
1999年 | 536篇 |
1994年 | 326篇 |
1992年 | 460篇 |
1991年 | 379篇 |
1990年 | 442篇 |
1989年 | 397篇 |
1988年 | 396篇 |
1987年 | 424篇 |
1986年 | 428篇 |
1985年 | 526篇 |
1984年 | 390篇 |
1983年 | 372篇 |
1982年 | 314篇 |
1981年 | 314篇 |
1980年 | 366篇 |
1979年 | 758篇 |
1978年 | 642篇 |
1977年 | 566篇 |
1976年 | 475篇 |
1975年 | 531篇 |
1974年 | 648篇 |
1973年 | 562篇 |
1972年 | 599篇 |
1971年 | 768篇 |
1970年 | 853篇 |
1969年 | 714篇 |
1968年 | 733篇 |
1967年 | 631篇 |
1966年 | 594篇 |
1965年 | 427篇 |
1964年 | 158篇 |
1959年 | 233篇 |
1958年 | 427篇 |
1957年 | 320篇 |
1956年 | 250篇 |
1955年 | 246篇 |
1954年 | 245篇 |
1948年 | 218篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
181.
B. Lejczak H. Starzemska P. Mastalerz 《Cellular and molecular life sciences : CMLS》1981,37(5):461-462
Summary Analogues of glutamic acid, -methylglutamic acid and glutamine in which the -or -COOH groups are replaced by PO3H2 or P(O)(OH3)OH functions competitively inhibit rat liver glutamine synthetase. The K1 values are comparable to or lower than KM for L-glutamate.This study was supported by grant R.1.9. 相似文献
182.
R. Lenzhofer C. Cerni I. Fröhlich J. Prager H. Pointner 《Cellular and molecular life sciences : CMLS》1981,37(9):1015-1017
Summary The influence of somatostatin on tumor cell growth was studied in vivo in mice (sarcoma 180 ascites tumor and Lewis lung tumor) and in vitro on nontransformed and polyoma-transformed cell lines. 4 or 20 g/100 g of cyclic somatostatin and 4 g/100 g of linear protamin Zn-bound somatostatin were injected s.c. twice daily in the in vivo study. Cyclic somatostatin (1, 4 or 10 g/ml) was added twice daily to the cell cultures. Somatostatin administration influenced neither the survival of animals nor the growth rate of cultured cell lines. *** DIRECT SUPPORT *** A2025117 00011 相似文献
183.
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
184.
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
185.
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
186.
H. Takeuchi T. Morimasa M. Matsumoto 《Cellular and molecular life sciences : CMLS》1977,33(7):938-939
Summary Several peptides were separated from-chymotrypsin-treated physalaemin by high voltage paper electrophoresis, and inhibition of the excitability of a molluscan giant neurone (tonically autoactive neurone) by the tripeptide, Lys-Phe-Tyr, was demonstrated.We thank Dr Sadaaki Iwanaga of Osaka University and Dr Atsuo Inoue of Daiichi Pharmaceutical CO for their helpful advice and the donation of the tripeptide (Lys-Phe-Tyr). 相似文献
187.
For the identification of a peptidyl principle inducing sexual agglutination in the yeast, 2 supposed hexapeptides (1a, b) were synthesized by the conventional method. The 1a (H-Arg-Gly-Pro-Phe-Pro-Ile-OH) revealed complete identity with the natural peptide in TLC, MS and biological property on agglutination. The 1b showed the sexual agglutinability in the same degree as 1a, though distinct differences were observed in the chemical data. Both 1a and 1b had a strong bitter taste. 相似文献
188.
In vivo studies indicated that the primary effects of E. coli endotoxin on hepatic clearance of sulfobromophthalein were at the excretory level. Newborns were more sensitive to the LPS than older animals. 相似文献
189.
190.
Summary Pronase and -chymotrypsin digested the major glycoprotein in the human and mouse red cell membranes and in SDS gel electrophoresis the glycoprotein disappeared accompanied by the appearance of a new band of lower mol.wt. However in the membranes of sheep, rat and rabbit, no digestion was demonstrated. The effects of pronase on anion permeability were almost identical for human and animal erythrocytes. 相似文献