全文获取类型
收费全文 | 686014篇 |
免费 | 77740篇 |
国内免费 | 292篇 |
出版年
2018年 | 6096篇 |
2016年 | 8298篇 |
2015年 | 11085篇 |
2014年 | 13135篇 |
2013年 | 18524篇 |
2012年 | 20751篇 |
2011年 | 21271篇 |
2010年 | 14481篇 |
2009年 | 13317篇 |
2008年 | 19210篇 |
2007年 | 19951篇 |
2006年 | 18676篇 |
2005年 | 18000篇 |
2004年 | 18069篇 |
2003年 | 17241篇 |
2002年 | 16921篇 |
2001年 | 28424篇 |
2000年 | 28479篇 |
1999年 | 22867篇 |
1998年 | 8368篇 |
1997年 | 8620篇 |
1996年 | 8088篇 |
1995年 | 7758篇 |
1994年 | 7615篇 |
1993年 | 7572篇 |
1992年 | 19431篇 |
1991年 | 19002篇 |
1990年 | 18616篇 |
1989年 | 18038篇 |
1988年 | 17169篇 |
1987年 | 16472篇 |
1986年 | 15107篇 |
1985年 | 15154篇 |
1984年 | 12654篇 |
1983年 | 11041篇 |
1982年 | 8609篇 |
1981年 | 7728篇 |
1980年 | 7399篇 |
1979年 | 12450篇 |
1978年 | 9607篇 |
1977年 | 8972篇 |
1976年 | 8535篇 |
1975年 | 9202篇 |
1974年 | 10204篇 |
1973年 | 10163篇 |
1972年 | 9440篇 |
1971年 | 8659篇 |
1970年 | 7552篇 |
1969年 | 7376篇 |
1968年 | 6885篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
The ECF™ lateral flow assay test is marketed to detect non-pregnancy in mares. The objectives of the present study were to determine the accuracy of the ECF test, the accuracy of the electronic reader accompanying the ECF test, and agreement between two human readers and the electronic reader. Serum samples were collected from anestrus, cycling but not inseminated, and inseminated mares, and were evaluated with the ECF™ test (EDP Biotech Company, Knoxville, TN, USA) at The Ohio State University and at the EDP Biotech Laboratory. Specificity ranged from 0.07 to 0.16, the negative predictive value ranged from 0.15 to 0.33, and accuracy ranged from 0.43 to 0.52. The electronic reader did not add improve the accuracy or predictive values of the test. Based on the electronic reader, 80.0% of the serum samples collected from the anestrus mares were false positives; Readers 1 and 2 had 60.0 and 33.3% false positives, respectively. For samples collected during the estrous cycle, 83.9% were false positives by the electronic reader, whereas Readers 1 and 2 had 43.7 and 26.4% false positives. We concluded that, regardless of whether the test strips were evaluated by a human or electronic reader, this assay was not accurate for determination of the non-pregnant mare. 相似文献
963.
964.
965.
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
966.
In the experiments on redox potential measurement for a series of identical samples of purified and presettled water it was found that the response to ultraviolet irradiation varies appreciably within a few days after treatment, including stepwise changes. In a few hours after exposure, leading to a higher content of reactive oxygen species as compared with the equilibrium values, long-term changes including variations in redox potential and optical system parameters are recorded in water and diluted aqueous media. We propose a heuristic organization model of the water-gas system with an increased content of reactive oxygen species. 相似文献
967.
968.
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
969.
970.