全文获取类型
收费全文 | 33444篇 |
免费 | 1237篇 |
国内免费 | 4篇 |
出版年
2023年 | 241篇 |
2022年 | 224篇 |
2021年 | 495篇 |
2020年 | 400篇 |
2019年 | 395篇 |
2018年 | 521篇 |
2017年 | 485篇 |
2016年 | 681篇 |
2015年 | 1053篇 |
2014年 | 1153篇 |
2013年 | 1868篇 |
2012年 | 1617篇 |
2011年 | 1487篇 |
2010年 | 1017篇 |
2009年 | 1093篇 |
2008年 | 1226篇 |
2007年 | 1145篇 |
2006年 | 1051篇 |
2005年 | 977篇 |
2004年 | 871篇 |
2003年 | 770篇 |
2002年 | 771篇 |
2001年 | 270篇 |
2000年 | 207篇 |
1999年 | 264篇 |
1998年 | 231篇 |
1997年 | 207篇 |
1996年 | 256篇 |
1995年 | 235篇 |
1994年 | 208篇 |
1993年 | 295篇 |
1992年 | 271篇 |
1991年 | 276篇 |
1990年 | 291篇 |
1989年 | 429篇 |
1988年 | 394篇 |
1987年 | 491篇 |
1986年 | 420篇 |
1985年 | 441篇 |
1984年 | 387篇 |
1983年 | 286篇 |
1982年 | 332篇 |
1981年 | 357篇 |
1980年 | 343篇 |
1979年 | 335篇 |
1978年 | 382篇 |
1977年 | 427篇 |
1976年 | 444篇 |
1975年 | 472篇 |
1974年 | 317篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Dr. Ambrosius Ábrahám 《Cell and tissue research》1929,9(4):694-696
Ohne Zusammenfassung
Mit 2 Textabbildungen 相似文献
72.
Prof. Dr. J. von Gelei 《Zoomorphology》1930,18(4):786-798
Ohne Zusammenfassung 相似文献
73.
74.
75.
Three experiments were performed to study the influence of challenging incentives on feedback-assisted heart rate reduction for coronary-prone (Type A) and non-coronary-prone (Type B) males. In the first experiment, when subjects were given a competitive instructional set, Type As were significantly more successful relative to Type Bs in reducing their heart rate; with a noncompetitive set, Type Bs were significantly more successful than were Type As. In the second experiment, when told that heart rate reduction was a scarce ability, Type As reduced heart rate significantly better than did Type Bs; when told that heart rate reduction was a common ability, Type Bs achieved significantly greater heart rate reduction than did Type As. In the third experiment, when heart rate reduction was described as being instrumental to time-urgency (i.e., getting more done in less time), Type As reduced heart rate significantly bettern than did Type Bs; when heart rate reduction was described as being instrumental to relaxation, Type Bs were significantly better able to reduce heart rate. In all three studies, the incentives had no effect on heart rate when feedback was not provided. The results are discussed as support for the notion that Type A behavioral pattern characteristics can be exploited to reduce Type A symptoms. Implications for how coronary-prone individuals may be challenged to modify symptoms within the clinical setting are discussed. 相似文献
76.
Dr. H. Eidmann 《Zoomorphology》1924,2(3-4):567-610
77.
Samples of microphytobenthos from the Tagus estuary were analysed for photosynthetic pigments by spectrophotometry and High
Performance Liquid Chromatography (HPLC). Chlorophyll a values obtained with HPLC and spectrophotometry methods presented a highly significant positive correlation for both spectrophotometric
methods used (with and without the correction for pheopigments), but this relationship depended on the type of sediment. We
concluded that spectrophotometric methods give reliable Chl-a values, being suited for routine analysis, when a vast number of replicates is needed. However, for the correct estimation
of pheopigments, HPLC analysis is indispensable. In the literature, Chl-a estimations are expressed per content (μg g−1) or concentration (mg m−2). We discuss the influence of sediment type on the results depending on the type of unit used, and propose a simple conversion
factor based on sediment water content. 相似文献
78.
79.
Dr. Karl Bauer 《Plant Systematics and Evolution》1890,40(5):188-191
Ohne Zusammenfassung 相似文献
80.
Dr. L. Simonkai 《Plant Systematics and Evolution》1888,38(10):341-345