全文获取类型
收费全文 | 4328篇 |
免费 | 254篇 |
国内免费 | 11篇 |
专业分类
4593篇 |
出版年
2023年 | 12篇 |
2022年 | 23篇 |
2021年 | 55篇 |
2020年 | 28篇 |
2019年 | 25篇 |
2018年 | 51篇 |
2017年 | 38篇 |
2016年 | 79篇 |
2015年 | 134篇 |
2014年 | 157篇 |
2013年 | 257篇 |
2012年 | 279篇 |
2011年 | 292篇 |
2010年 | 162篇 |
2009年 | 175篇 |
2008年 | 282篇 |
2007年 | 284篇 |
2006年 | 283篇 |
2005年 | 288篇 |
2004年 | 326篇 |
2003年 | 271篇 |
2002年 | 248篇 |
2001年 | 63篇 |
2000年 | 54篇 |
1999年 | 63篇 |
1998年 | 61篇 |
1997年 | 45篇 |
1996年 | 33篇 |
1995年 | 35篇 |
1994年 | 35篇 |
1993年 | 38篇 |
1992年 | 33篇 |
1991年 | 34篇 |
1990年 | 29篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 16篇 |
1986年 | 31篇 |
1985年 | 21篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1975年 | 9篇 |
1973年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有4593条查询结果,搜索用时 0 毫秒
101.
Staphylococcus E-46, which exhibits high virulence in mice mainly due to resistance to phagocytosis, gradually lost its virulence during growth in artificial media [Heart-Infusion (HI) slants]. Staphylococcus E-46 is coagulase-negative and DNase-positive, and has a capsule-like structure, and the less-virulent derivative (LVD) strain seemed not to be changed in this respect. The bacteria which had been exposed to HI slants for more than one year (= LVD strain) became more sensitive to phagocytosis by mouse peritoneal macrophages than bacteria which were kept in a lyophilized state. The chemiluminescent response of macrophages to the LVD strain was remarkably higher than that to the original Staphylococcus E-46. When the LVD or the sera for opsonization were heated, the chemiluminescence to the LVD was as low as that to the original Staphylococcus E-46. Polyacrylamide gel electrophoresis of sonication-released membrane protein from the LVD strain showed a unique band with a molecular weight of about 40,000. The factor concerned with the virulence of Staphylococcus E-46 is discussed based on these results. 相似文献
102.
Heitaroh Iwata Toshio Matsuda Sadaaki Maeda Akemichi Baba 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,583(2):159-166
The effect of ascorbic acid on microsomal thiamine diphosphate activity in rat brain was examined. Ascorbic acid at 0.02–0.1 mM increased the thiamine diphosphate activity by 20–600% and produced a significant amount of lipid peroxide, which was measured with thiobarbiturate under the same conditions as the enzyme. A lag period of about 10 min was observed in the process of stimulation of enzyme activity by ascorbic acid. The stimulation of enzyme activity and the lipid peroxidation induced by ascorbic acid were blocked by metal-binding compounds (EDTA, α,α′-dipyridyl, o-phenanthroline) and an antioxidant (N,N′-diphenyl p-phenylenediamine). GSH significantly enhanced the stimulation of enzyme activity and formation of lipid peroxide by 0.02–0.05 mM ascorbic acid. The effect of GSH was due in part to maintenance of the concentration of ascorbic acid in the medium, since GSH could convert dehydroascorbic acid, an oxidized form of ascorbic acid, to ascorbic acid. 相似文献
103.
Sadako Iwata Kunio Tochikubo Keijiro Kato Takanori Hirata Shozo Kotani Kunio Yagi 《Microbiology and immunology》1976,20(2):123-129
Enzyme(s) capable of decomposing N-acetylglucosaminyl ribitol teichoic acid prepared from the cell wall of Staphylococcus aureus FDA 209 P was obtained from the culture supernatant of a gram-negative, rod-shaped, spore-forming soil bacterium. Properties of the bacterium were very similar to those of Bacillus circulans. 相似文献
104.
Kanavillil Nandakumar Hideki Obika Tatsuya Shinozaki Toshihiko Ooie Akihiro Utsumi Tetsuo Yano 《Biofouling》2013,29(2):123-127
The impact of pulsed laser irradiation on the marine biofilm forming bacterium Pseudoalteromonas carrageenovora was investigated in the laboratory by monitoring mortality and the post-irradiation growth pattern. The impact of laser irradiation on bacterial mortality increased with the duration of irradiation. Laser irradiation at 532 nm (0.1 J cm m 2 ) for 15 min resulted in a 53% cell mortality immediately after irradiation. However, the impact after a period of 5 h (delayed impact) was more severe. The growth pattern of irradiated samples showed a prolonged lag phase compared to the reference, due to a reduction in total viable counts (TVC) in the irradiated samples. Nucleic acid staining is suggested to be a promising technique for monitoring laser inflicted bacterial mortality. Thus, the results suggest that laser irradiation could be considered as an alternative technique to reduce the number of biofilm forming bacteria and thereby biofilm formation on hard surfaces. 相似文献
105.
106.
107.
Limnology - The in-stream processing of nutrients plays an important role in the fluvial nutrient transport from lands to the ocean, but few empirical studies have addressed the temporal dynamics... 相似文献
108.
Zhihua Liu John S. Kimball Nicholas C. Parazoo Ashley P. Ballantyne Wen J. Wang Nima Madani Caleb G. Pan Jennifer D. Watts Rolf H. Reichle Oliver Sonnentag Philip Marsh Miriam Hurkuck Manuel Helbig William L. Quinton Donatella Zona Masahito Ueyama Hideki Kobayashi Eugnie S. Euskirchen 《Global Change Biology》2020,26(2):682-696
Arctic and boreal ecosystems play an important role in the global carbon (C) budget, and whether they act as a future net C sink or source depends on climate and environmental change. Here, we used complementary in situ measurements, model simulations, and satellite observations to investigate the net carbon dioxide (CO2) seasonal cycle and its climatic and environmental controls across Alaska and northwestern Canada during the anomalously warm winter to spring conditions of 2015 and 2016 (relative to 2010–2014). In the warm spring, we found that photosynthesis was enhanced more than respiration, leading to greater CO2 uptake. However, photosynthetic enhancement from spring warming was partially offset by greater ecosystem respiration during the preceding anomalously warm winter, resulting in nearly neutral effects on the annual net CO2 balance. Eddy covariance CO2 flux measurements showed that air temperature has a primary influence on net CO2 exchange in winter and spring, while soil moisture has a primary control on net CO2 exchange in the fall. The net CO2 exchange was generally more moisture limited in the boreal region than in the Arctic tundra. Our analysis indicates complex seasonal interactions of underlying C cycle processes in response to changing climate and hydrology that may not manifest in changes in net annual CO2 exchange. Therefore, a better understanding of the seasonal response of C cycle processes may provide important insights for predicting future carbon–climate feedbacks and their consequences on atmospheric CO2 dynamics in the northern high latitudes. 相似文献
109.
Mori Hideki Masaki Takashi Tsunamoto Yoshihiro Naoe Shoji 《Journal of plant research》2020,133(2):193-203
Journal of Plant Research - Lianas have a huge influence on forest structure and function. However, it is unclear how the surrounding environment affects the establishment of liana seedlings in... 相似文献