全文获取类型
收费全文 | 193511篇 |
免费 | 15462篇 |
国内免费 | 14936篇 |
专业分类
223909篇 |
出版年
2024年 | 392篇 |
2023年 | 2357篇 |
2022年 | 5196篇 |
2021年 | 8917篇 |
2020年 | 6061篇 |
2019年 | 7541篇 |
2018年 | 7345篇 |
2017年 | 5534篇 |
2016年 | 7777篇 |
2015年 | 11333篇 |
2014年 | 13428篇 |
2013年 | 14330篇 |
2012年 | 17318篇 |
2011年 | 15717篇 |
2010年 | 9906篇 |
2009年 | 8735篇 |
2008年 | 10336篇 |
2007年 | 9322篇 |
2006年 | 8212篇 |
2005年 | 6577篇 |
2004年 | 5734篇 |
2003年 | 5186篇 |
2002年 | 4554篇 |
2001年 | 3840篇 |
2000年 | 3551篇 |
1999年 | 3435篇 |
1998年 | 1973篇 |
1997年 | 2057篇 |
1996年 | 1858篇 |
1995年 | 1685篇 |
1994年 | 1633篇 |
1993年 | 1223篇 |
1992年 | 1746篇 |
1991年 | 1408篇 |
1990年 | 1064篇 |
1989年 | 982篇 |
1988年 | 820篇 |
1987年 | 727篇 |
1986年 | 635篇 |
1985年 | 649篇 |
1984年 | 367篇 |
1983年 | 340篇 |
1982年 | 240篇 |
1981年 | 197篇 |
1980年 | 164篇 |
1979年 | 190篇 |
1978年 | 129篇 |
1977年 | 121篇 |
1975年 | 114篇 |
1974年 | 126篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Abstract The diapause of two populations of Trichogramma evanescens Westwood (T. evanescens A and T. evanescens B), collected from different Iranian insect pests, was studied. T. evunescens A in the eggs of Corcyra cephalonica was easily induced to stable diapause with constant 8°C, 15 % and fluctuating temperature (11–23) C -11C. T. evanescens B could not be induced to diapause with the same temperatural regime and host. The experiments showed that the host of maternal generations and the ability of avoiding super-parasitism may play an important role in intraspecific variation of T. evunescens in diapause induction. 相似文献
52.
Several products derived from processed maca hypocotyls (Lepidium peruvianum Chacón, previously known asL. meyenii Walp.) were surveyed for glucosinolate content and quantified by HPLC analysis. These included pills, capsules, flour, liquor, tonic and mayonnaise. Different plant organs such as fresh hypocotyls and leaves, seeds, dry hypocotyls, and sprouts were also included in the survey. The most abundant glucosinolates detected in fresh and dry hypocotyls and leaves were the aromatic glucosinolates, benzylglucosinolate (glucotropaeolin) and p-methoxybenzylglucosinolate. Maca seeds and sprouts differed in profile from hypocotyls and leaves due to the modification of benzylglucosinolate. No glucosinolates were detected in liquor and tonic, while mayonnaise had only trace amounts of those glucosinolates. It had instead allylglucosinolate (sinigrin), which is an aliphatic glucosinolate. The pills, capsules and flour had the same glucosinolates as those observed in hypocotyls, but in variable amounts. The richest sources of glucosinolates were seeds, fresh hypocotyls and sprouts, in that order. 相似文献
53.
Embryos of most fish develop externally and are exposed to an aquatic environment full of potential pathogens, whereas they have little or only limited ability to mount an efficient and protective response. How fish embryos survive pathogenic attacks remains poorly defined. Here we demonstrate that the maternal immunization of female zebrafish with formalin-killed Aeromonas hydrophila causes a significant increase in C3 and Bf contents in the mother, a corresponding rise in the offspring, and induces a remarkable increase in the hemolytic activities in both the mother and offspring. In addition, the embryos derived from the immunized mother are significantly more tolerant to A. hydrophila challenge than those from the unimmunized fish, and blocking C3 and Bf activities by injection of the antibodies against C3 and Bf into the embryos render them more susceptible to A. hydrophila. These results clearly show that the protection of zebrafish embryos against A. hydrophila can be achieved by the maternally-transferred immunity of the complement system operating via the alternative pathway. This appears to be the first report providing in vivo evidences for the protective role of the alternative complement components in the early embryos of zebrafish, paving the way for insights into the in vivo function of other maternally-transferred factors in fish. 相似文献
54.
55.
56.
57.
58.
The chemiluminescence (CL) of bis(2,4,6‐trichlorophyenyl) oxalate with hydrogen peroxide in the present of cationic surfactant and gold nanoparticles was studied. The CL emission was obviously enhanced in the presence of surfactant at a suitable concentration, with a synergetic catalysis effect exhibited. Different sizes of gold nanoparticles (15 and 50 nm) showed different effects on CL intensity. Mechanisms of the CL reaction and sensitization effect are discussed. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
59.
60.
Mohanty Madhumita Jena; Ye Maian; Li Xingli; Rossi Noreen F. 《American journal of physiology. Cell physiology》2001,281(2):C555
Hypotonicswelling increases the intracellular Ca2+ concentration([Ca2+]i) in vascular smooth muscle cells(VSMC). The source of this Ca2+ is not clear. To study thesource of increase in [Ca2+]i in response tohypotonic swelling, we measured [Ca2+]i infura 2-loaded cultured VSMC (A7r5 cells). Hypotonic swelling produced a40.7-nM increase in [Ca2+]i that was notinhibited by EGTA but was inhibited by 1 µM thapsigargin. Priordepletion of inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ stores with vasopressin did not inhibit the increasein [Ca2+]i in response to hypotonic swelling.Exposure of 45Ca2+-loaded intracellular storesto hypotonic swelling in permeabilized VSMC produced an increase in45Ca2+ efflux, which was inhibited by 1 µMthapsigargin but not by 50 µg/ml heparin, 50 µM ruthenium red, or25 µM thio-NADP. Thus hypotonic swelling of VSMC causes a release ofCa2+ from the intracellular stores from a novel sitedistinct from the IP3-, ryanodine-, and nicotinic acidadenine dinucleotide phosphate-sensitive stores. 相似文献