全文获取类型
收费全文 | 88292篇 |
免费 | 8207篇 |
国内免费 | 48篇 |
专业分类
96547篇 |
出版年
2022年 | 818篇 |
2021年 | 1494篇 |
2020年 | 1044篇 |
2019年 | 1201篇 |
2018年 | 1658篇 |
2017年 | 1436篇 |
2016年 | 2349篇 |
2015年 | 3621篇 |
2014年 | 3570篇 |
2013年 | 4599篇 |
2012年 | 5335篇 |
2011年 | 4851篇 |
2010年 | 3125篇 |
2009年 | 2965篇 |
2008年 | 3785篇 |
2007年 | 3773篇 |
2006年 | 3416篇 |
2005年 | 3688篇 |
2004年 | 3573篇 |
2003年 | 2986篇 |
2002年 | 2634篇 |
2001年 | 2495篇 |
2000年 | 2430篇 |
1999年 | 2172篇 |
1998年 | 1084篇 |
1997年 | 1020篇 |
1996年 | 1043篇 |
1995年 | 909篇 |
1994年 | 874篇 |
1993年 | 854篇 |
1992年 | 1775篇 |
1991年 | 1430篇 |
1990年 | 1392篇 |
1989年 | 1376篇 |
1988年 | 1285篇 |
1987年 | 1174篇 |
1986年 | 1139篇 |
1985年 | 1202篇 |
1984年 | 1021篇 |
1983年 | 791篇 |
1982年 | 630篇 |
1981年 | 586篇 |
1980年 | 531篇 |
1979年 | 760篇 |
1978年 | 649篇 |
1977年 | 494篇 |
1976年 | 441篇 |
1975年 | 466篇 |
1974年 | 548篇 |
1973年 | 512篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
E. L. García Diez J. L. Labajo Salazar F. de Pablo Dávila 《International journal of biometeorology》1993,37(4):194-199
The present paper offers data on the effect of certain meteorological parameters on the outbreak of forest fires in Galicia (Spain). In a day-to-day analysis, the values of the stability of the air column and the saturation deficit at the lower levels are related to the number of fires occurring in the following 24 h. 相似文献
143.
144.
145.
M J Bussemakers A van Bokhoven J J van Groningen F M Debruyne J A Schalken 《Biochemical and biophysical research communications》1992,182(1):318-324
Differential hybridization analysis revealed two cDNA clones, pBUS19 and pBUS30, to be overexpressed in progressionally advanced rat prostatic tumors. Northern blot analysis suggested the clones to be related although no homology in nucleotide sequence could be shown. Isolation and characterization of a pBUS19-related clone, pJG116, and computer-assisted database comparison showed that all three clones could be mapped within a rat-specific endogenous retrovirus. The importance of overexpression of retroviral sequences in advanced prostatic cancer remains unclear. 相似文献
146.
J. P. van der Walt 《Antonie van Leeuwenhoek》1992,62(4):247-250
The Lipomycetaceae (Endomycetales) are known from the generaDipodascopsis, Lipomyces andZygozyma with budding anamorphic states inMyxozyma. The family is easily recognized culturally and physiologically but is phenotypically and ecologically extremely diverse. This natural taxon is phylogenetically distinct from the Saccharomycetaceae, but probably related to the Dipodascaceae. The possible evolution of the lipomycetaceous anamorphs is discussed. 相似文献
147.
Cytokine production in a model of wound healing: the appearance of MIP-1, MIP-2, cachectin/TNF and IL-1 总被引:9,自引:1,他引:8
T J Fahey B Sherry K J Tracey S van Deventer W G Jones J P Minei S Morgello G T Shires A Cerami 《Cytokine》1990,2(2):92-99
Macrophages are essential for normal wound repair and many of their effects on healing wounds are likely to be mediated by the secretion of cytokines. This study examines the appearance of messenger RNA (mRNA) for cachectin/tumor necrosis factor (TNF), IL 1, and macrophage inflammatory proteins 1 and 2 (MIP-1 and MIP-2), as well as the mature peptides, in a model of wound healing using wound chambers. RNA for all four cytokines can be detected in wound inflammatory cells by polymerase chain reaction amplification throughout the first 7 days. Cachectin/TNF and IL 1 protein levels peaked on the first day after wound chamber implantation, and MIP-1 and MIP-2 were detected only on day 3. The data suggest that these cytokines participate in the early inflammatory response to wounding. 相似文献
148.
Phenology, morphology, life history and responses to different temperature and photoperiod conditions were studied in Japanese Stypocaulon durum (Ruprecht) Okamura. Erect thalli of the species were collected year-round, but the mature thalli forming either uniloc-ular sporangia or two different types of plurilocular structures (evidently gametangia) on separate thalli were found only in winter. ln culture, an isomorphic life history is suggested for the species, alternating between a sporophyte forming unilocular sporangia and gam-etophytes forming plurilocular macro- (female) and micro- (male) gametangia. Contents of unilocular sporangia were not released, but germinated in situ, developing into erect thalli forming plurilocular gametangia. Macrogametangia released aplanogametes (oospores), but male gametangia appeared to be non-functional, although flagellated cells were once formed in the loc-uli. This is the first report of plurilocular gametangia in the species. Although the species grew well and matured under considerably lower temperature conditions than European Stypocaulon scoparium (L.) Sauvageau, its temperature requirements showed similarity to northwestern Atlantic Stypocaulon species. This supports the notion that northwestern Atlantic Stypocaulon is conspecific with S. durum. 相似文献
149.
150.
C A Gobatto M A de Mello C Y Sibuya J R de Azevedo L A dos Santos E Kokubun 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2001,130(1):21-27
The higher concentration during exercise at which lactate entry in blood equals its removal is known as 'maximal lactate steady state' (MLSS) and is considered an important indicator of endurance exercise capacity. The aim of the present study was to determine MLSS in rats during swimming exercise. Adult male Wistar rats, which were adapted to water for 3 weeks, were used. After this, the animals were separated at random into groups and submitted once a week to swimming sessions of 20 min, supporting loads of 5, 6, 7, 8, 9 or 10% of body wt. for 6 consecutive weeks. Blood lactate was determined every 5 min to find the MLSS. Sedentary animals presented MLSS with overloads of 5 and 6% at 5.5 mmol/l blood lactate. There was a significant (P<0.05) increase in blood lactate with the other loads. In another set of experiments, rats of the same strain, sex and age were submitted daily to 60 min of swimming with an 8% body wt. overload, 5 days/week, for 9 weeks. The rats were then submitted to a swimming session of 20 min with an 8% body wt. overload and blood lactate was determined before the beginning of the session and after 10 and 20 min of exercise. Sedentary rats submitted to the same acute exercise protocol were used as a control. Physical training did not alter the MLSS value (P<0.05) but shifted it to a higher exercise intensity (8% body wt. overload). Taken together these results indicate that MLSS measured in rats in the conditions of the present study was reproducible and seemed to be independent of the physical condition of the animals. 相似文献