全文获取类型
收费全文 | 24818篇 |
免费 | 70篇 |
国内免费 | 57篇 |
专业分类
系统科学 | 271篇 |
丛书文集 | 493篇 |
教育与普及 | 45篇 |
理论与方法论 | 112篇 |
现状及发展 | 10925篇 |
研究方法 | 1032篇 |
综合类 | 11644篇 |
自然研究 | 423篇 |
出版年
2013年 | 162篇 |
2012年 | 363篇 |
2011年 | 792篇 |
2010年 | 153篇 |
2008年 | 410篇 |
2007年 | 440篇 |
2006年 | 482篇 |
2005年 | 471篇 |
2004年 | 451篇 |
2003年 | 444篇 |
2002年 | 368篇 |
2001年 | 736篇 |
2000年 | 730篇 |
1999年 | 436篇 |
1992年 | 430篇 |
1991年 | 381篇 |
1990年 | 410篇 |
1989年 | 340篇 |
1988年 | 382篇 |
1987年 | 390篇 |
1986年 | 355篇 |
1985年 | 502篇 |
1984年 | 383篇 |
1983年 | 312篇 |
1982年 | 262篇 |
1981年 | 267篇 |
1980年 | 365篇 |
1979年 | 756篇 |
1978年 | 641篇 |
1977年 | 626篇 |
1976年 | 485篇 |
1975年 | 557篇 |
1974年 | 742篇 |
1973年 | 639篇 |
1972年 | 671篇 |
1971年 | 759篇 |
1970年 | 999篇 |
1969年 | 801篇 |
1968年 | 674篇 |
1967年 | 733篇 |
1966年 | 653篇 |
1965年 | 483篇 |
1964年 | 129篇 |
1959年 | 270篇 |
1958年 | 410篇 |
1957年 | 310篇 |
1956年 | 269篇 |
1955年 | 242篇 |
1954年 | 269篇 |
1948年 | 181篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
922.
Antibodies reacting with 3,5,3',5' tetraiodo-l-tyrosyl-l-tyrosine (I2Tyr-I2Tyr) were elicited in rabbits by immunization with an oxidized yeast conjugate coupled with I2Tyr-I2Tyr. Ion-exchange chromatography was used to purify immunoglobulins, in order to improve the specificity in measurement of I2Tyr-I2Tyr level in patient serum. IgG binding capacity versus I2Tyr-I2Tyr was considerably increased after immunoglobulin purification. 相似文献
923.
Glutamine synthetase (GS) of human liver was recognized with a polyclonal antibody to pig brain GS, but failed to stain with an antibody against rat liver GS. Using the latter antibody GS of human liver was shown to be localized within small rings of 1 to 3 hepatocytes surrounding the terminal hepatic venules. This pattern was analogous to that seen in rat and mouse liver. 相似文献
924.
Summary Three phylogenetically diverse microorganisms methylated several different chloro- and nitro-substituted benzenethiols to yield the corresponding methylthiobenzenes. These products were identified by gas chromatography-mass spectrometry. In several cases large percentages of the methylthio products were released by intact cells into the medium, suggesting that microbial methylation of xenobiotic thiols may be a significant biotransformation in many ecosystems.Acknowledgments. This investigation was supported by research grant ES 02639 from the National Institute for Environmental Health Sciences, and an equipment grant (RR07013) from the Biomedical Research Support grant program. Division of Research Resource, NIH. We thank Steve Hawthorne for assistance in performing GC-MS analyses. 相似文献
925.
926.
R. E. Lee Jr E. H. Bryant J. G. Baust 《Cellular and molecular life sciences : CMLS》1985,41(9):1191-1192
Summary After 7 days of space flight house flies,Musca domestica, exhibited similar longevity, but a reduction in reproductive output as compared to earthbound controls. This reduction was not observed in later generations. These data suggest that space flight directly alters the rate of ovarian development, but that this effect is not genetically transmitted.Acknowledgment. We thank Todd E. Nelson, student participant in the Space Shuttle Student Involvement Project, John T. Jackson, NASA/Johnson Space Center, and James R. Peterson, Honeywell, Inc. for providing us with the flies and information related to the in-flight experiments. 相似文献
927.
Summary The decomposition of the toxic and environmentally hazardous 2378-TCDD by gamma irradiation was studied and successfully used to decontaminatge laboratory wastes containing small quantities of this chemically and biological stable compound. The method makes use of gamma irradiation from a commercial60cobalt facility at high dose levels (100 kGy) to break down the compound into notoxic products. Irradiation also decomposed 2378-TCDD in contaminated soil from the Seveso accident. 相似文献
928.
Summary The distribution of substance P-like immunoreactivity was studied in the thoracic dorsal root ganglia of the frogRana esculenta by immunohistochemistry. Substance P-like immunoreactivity was contained in approximately 50% of primary sensory neurons. The immunoreactive fibers arising from the cell bodies are collected in small bundles within the ganglia neuropil before entering the central and peripheral roots. 相似文献
929.
930.
The Con A-Sepharose affinity chromatography of glycoproteins was even more effective at 4 degrees C than that at room temperature (26-28 degrees C) in the presence of sodium dodecyl sulfate (SDS). Application of this methodology to the separation of several glycoproteins from SDS-solubilized membrane proteins in rat cerebellum, including a glycoprotein characteristic of the Purkinje cells, was successful. 相似文献