全文获取类型
收费全文 | 674016篇 |
免费 | 81786篇 |
国内免费 | 312篇 |
出版年
2018年 | 5794篇 |
2016年 | 7687篇 |
2015年 | 10828篇 |
2014年 | 12604篇 |
2013年 | 18258篇 |
2012年 | 20271篇 |
2011年 | 20657篇 |
2010年 | 13962篇 |
2009年 | 12725篇 |
2008年 | 18174篇 |
2007年 | 18932篇 |
2006年 | 17601篇 |
2005年 | 17059篇 |
2004年 | 16770篇 |
2003年 | 16528篇 |
2002年 | 16069篇 |
2001年 | 30122篇 |
2000年 | 30345篇 |
1999年 | 24199篇 |
1998年 | 8700篇 |
1997年 | 9234篇 |
1996年 | 8761篇 |
1995年 | 8315篇 |
1994年 | 8204篇 |
1993年 | 8286篇 |
1992年 | 20730篇 |
1991年 | 20231篇 |
1990年 | 19648篇 |
1989年 | 19197篇 |
1988年 | 17726篇 |
1987年 | 17125篇 |
1986年 | 15784篇 |
1985年 | 15899篇 |
1984年 | 13256篇 |
1983年 | 11563篇 |
1982年 | 8960篇 |
1981年 | 7995篇 |
1980年 | 7697篇 |
1979年 | 12912篇 |
1978年 | 10113篇 |
1977年 | 9295篇 |
1976年 | 8692篇 |
1975年 | 9509篇 |
1974年 | 10102篇 |
1973年 | 10110篇 |
1972年 | 9193篇 |
1971年 | 8531篇 |
1970年 | 7170篇 |
1969年 | 6949篇 |
1968年 | 6234篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Fossil plants of the Chingandzha flora were studied from volcanogenic sediments of the Chingandzha and Rond formations on
the northern coast of the Sea of Okhotsk. It was concluded that all platanaceous leaves earlier described in this flora as
different taxa belong to one highly variable species, Pseudoprotophyllum cordatum Samyl. emend. Shczepetov et Golovneva. 相似文献
982.
The combination of alpha interferon and vinblastine has been reported to yield a response rate of 30-40% in previously untreated patients with metastatic renal cell carcinoma. This combination was given to nine patients with advanced metastatic renal carcinoma after they failed or relapsed on alpha-interferon alone, to attempt to evaluate the role of vinblastine in this combination. Neither complete nor partial response was observed. Two patients had disease stabilization for two and seven months. Our preliminary results suggest that vinblastine did not add to the efficacy of interferon in this group of patients. 相似文献
983.
984.
B P Sharonov I V Churilova 《Biochemical and biophysical research communications》1992,189(2):1129-1135
Bovine superoxide dismutase (SOD) was inactivated during incubation with phorbol myristate acetate-stimulated neutrophils. In addition, stimulated neutrophils were able to disrupt the SOD structure. Inactivation and structural damage were dependent on the action of hypochlorous acid, an oxidant generated by the myeloperoxidase-hydrogen peroxide-chloride system of neutrophils. Incubation of SOD with stimulated neutrophils lead to long-wavelength fluorescence (ex, 350 nm; em, 450 nm) and the appearance of new structural forms with other isoelectric points. These additional forms possess catalytic activity. Generation of catalytically active new forms of SOD demonstrates the inaccessibility of the active centre of SOD to hypochlorite and may be a reason for the successful application of SOD during anti-inflammatory therapy. 相似文献
985.
986.
987.
Phytochrome A regulates red-light induction of phototropic enhancement in Arabidopsis. 总被引:20,自引:5,他引:15
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Phytochrome A (phyA) and phytochrome B photoreceptors have distinct roles in the regulation of plant growth and development. Studies using specific photomorphogenic mutants and transgenic plants overexpressing phytochrome have supported an evolving picture in which phyA and phytochrome B are responsive to continuous far-red and red light, respectively. Photomorphogenic mutants of Arabidopsis thaliana that had been selected for their inability to respond to continuous irradiance conditions were tested for their ability to carry out red-light-induced enhancement of phototropism, which is an inductive phytochrome response. We conclude that phyA is the primary photoreceptor regulating this response and provide evidence suggesting that a common regulatory domain in the phyA polypeptide functions for both high-irradiance and inductive phytochrome responses. 相似文献
988.
Socioeconomic, demographic and environmental determinants of infant mortality in Nepal 总被引:1,自引:0,他引:1
The Nepal Fertility and Family Planning Survey of 1986 demonstrated that demographic variables, previous birth interval and survival of preceding child, still predominated as determinants of infant mortality, particularly in rural areas of Nepal. However, in urban Nepal, where the level of socioeconomic development is higher, an environmental variable, along with previous birth interval and survival of preceding child emerges as important in determining infant mortality. Separate policy measures for child survival prospects in rural and urban Nepal are suggested. 相似文献
989.
990.