全文获取类型
收费全文 | 55750篇 |
免费 | 5178篇 |
国内免费 | 31篇 |
专业分类
60959篇 |
出版年
2022年 | 395篇 |
2021年 | 851篇 |
2020年 | 493篇 |
2019年 | 615篇 |
2018年 | 768篇 |
2017年 | 686篇 |
2016年 | 1148篇 |
2015年 | 1904篇 |
2014年 | 2113篇 |
2013年 | 2780篇 |
2012年 | 3515篇 |
2011年 | 3581篇 |
2010年 | 2294篇 |
2009年 | 2057篇 |
2008年 | 2892篇 |
2007年 | 3057篇 |
2006年 | 2968篇 |
2005年 | 2799篇 |
2004年 | 2714篇 |
2003年 | 2618篇 |
2002年 | 2474篇 |
2001年 | 760篇 |
2000年 | 633篇 |
1999年 | 764篇 |
1998年 | 803篇 |
1997年 | 615篇 |
1996年 | 541篇 |
1995年 | 506篇 |
1994年 | 481篇 |
1993年 | 501篇 |
1992年 | 595篇 |
1991年 | 522篇 |
1990年 | 515篇 |
1989年 | 483篇 |
1988年 | 470篇 |
1987年 | 423篇 |
1986年 | 419篇 |
1985年 | 474篇 |
1984年 | 524篇 |
1983年 | 443篇 |
1982年 | 529篇 |
1981年 | 538篇 |
1980年 | 445篇 |
1979年 | 399篇 |
1978年 | 415篇 |
1977年 | 340篇 |
1976年 | 390篇 |
1975年 | 291篇 |
1974年 | 339篇 |
1973年 | 331篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
Breast microcysts are considered to be a normal findings in the adult female breast without any increased risk of developing carcinomatous change. Breast cysts fluid contains steroid but not studies have been reported on the ability of breast microcysts to metabolise steroid hormones. It was, therefore, the aim of this study to identify the metabolites formed on incubation of radiolabelled testosterone with microcysts. In all instances dihydrotestosterone and androstenedione were formed. Oestrogens were not identified. Tis study, therefore, provides evidence for th presence of 5-alpha-reductase and 17-oxidoreductase enzyme systems in breast microcysts. 相似文献
53.
James A. Wanner 《American journal of physical anthropology》1977,47(1):99-102
An analysis of the anterior patellar groove of the human femur shows considerable variation in its medial and lateral spects. The groove itself, measured by the angle it encloses, shows considerably less variation than its individual components. The suggested functional relationship between bicondylar angle and lateral elevation of the patellar groove does not obtain for this sample. 相似文献
54.
55.
56.
57.
The Escherichia coli dnaW mutation is an allele of the adk gene 总被引:3,自引:0,他引:3
Joan M. Henson Aleksandra Blinkowa James R. Walker 《Molecular & general genetics : MGG》1982,186(4):488-492
Summary A dnaW mutant, isolated on the basis of inability to effect conjugal DNA transfer at high temperature, has been shown by complementation and enzyme assay to be defective in the adk (adenylate kinase; EC 2.7.4.3) locus. The adk mutant, known to have reduced ATP concentration at the nonpermissive temperature (Cousin and Belaich 1966), was used to demonstrate a donor energy requirement for stable aggregate formation and for chromosome transfer in conjugation. 相似文献
58.
59.
James E. Boggan Julian T. Hoff Edwin B. Boldrey William M. Wara 《The Western journal of medicine》1980,133(2):108-114
Thirty cases of intraspinal neoplasms occurring during the first two decades of life are reviewed. Histologic examination showed 13 of these to be astrocytomas, 6 neuroblastomas, 5 sarcomas, 3 ependymomas, 2 neurofibromas and 1 a schwannoma. Orthopedic deformities developed or worsened in 60 percent of patients surviving longer than a year after diagnosis. In five patients some form of endocrine deficiency developed after irradiation. For treatment of radiosensitive extradural malignant lesions, biopsy followed by irradiation is advocated. 相似文献
60.