全文获取类型
收费全文 | 2538篇 |
免费 | 170篇 |
国内免费 | 15篇 |
专业分类
2723篇 |
出版年
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 54篇 |
2020年 | 36篇 |
2019年 | 45篇 |
2018年 | 61篇 |
2017年 | 61篇 |
2016年 | 103篇 |
2015年 | 108篇 |
2014年 | 142篇 |
2013年 | 171篇 |
2012年 | 174篇 |
2011年 | 206篇 |
2010年 | 110篇 |
2009年 | 97篇 |
2008年 | 124篇 |
2007年 | 126篇 |
2006年 | 107篇 |
2005年 | 105篇 |
2004年 | 74篇 |
2003年 | 95篇 |
2002年 | 72篇 |
2001年 | 38篇 |
2000年 | 37篇 |
1999年 | 29篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1992年 | 18篇 |
1991年 | 26篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 24篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1977年 | 11篇 |
1975年 | 18篇 |
1974年 | 17篇 |
1973年 | 14篇 |
1972年 | 18篇 |
1971年 | 14篇 |
1970年 | 10篇 |
排序方式: 共有2723条查询结果,搜索用时 0 毫秒
1.
A Ba?sset J Cotonat P Montastruc 《Comptes rendus des séances de la Société de biologie et de ses filiales》1975,169(2):444-448
The authors have studied in the dog--normal or diabetic insipidus after hypothalamic lesion--submitted to oral ingestion of ethanol the effects of a few antidiuretic drug: chlorpropamid, atromid-S, carbamazepin and carisoprodol. The carisoprodol only can reduce the diuresis and the drinking provoked by ethanol. 相似文献
2.
We isolated a recombinant H9N2 avian influenza virus (AIV) from fresh egret feces in the Ardeidae protection region of the Dongting Lake wetland area in China, and it was designated A/Egret/Hunan/1/2012(H9N2). This is the first report of isolating H9N2 AIV from wild birds in the Dongting Lake wetland. Its eight gene segments are generated by reassortment of gene segments of different AIV subtypes. These results are helpful for understanding the epidemiology and evolution of AIV in wild birds during migration. 相似文献
3.
4.
M S Ba?zhomartov S V Prozorovski? V I Vasil'eva I I Efremova M A Furman 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1979,(5):83-87
A complex of immunological cell tests with M. pneumoniae antigen (the lymphocyte blast-cell transformation test, the allergic neutrophil alteration test) was carried out in order to establish the correlation between the results of positive seroconversion and the sepcific immunological reactivity of lymphoid cells in pneumonia patients. Mycoplasmic cutireactive allergen, when used for the accelerated diagnosis of mycoplasmic pneumonia in humans, was shown to be specific and safe. Cuti-allergic tests with mycoplasmic allergen allowed to diagnose mycoplasmic pneumonia at early stages (beginning from days 5--7), which ensures the possibility of indicating etiotropic treatment to patients in due time. 相似文献
5.
Rose C. Wade Janet V. Powers Cyril Ponnamperuma 《Origins of life and evolution of the biosphere》1989,19(2):199-220
This bibliography is the seventeenth annual supplement to the comprehensive bibliography on the same subject which was published in Space Life Sci. 2(1970), 225-295; 3(1972), 293-304; 4(1973), 309-329 and in Origins of Life 5(1974), 505-527; 6(1975), 285-300; 7(1976), 75-85; 8(1977), 59-66; 9(1978), 67-74; 10(1980), 69-87; 10(1980), 379-404; 11(1981), 273-288; 12(1982), 93-118; 13(1983), 61-80; 15(1984), 55-69; 17(1987), 171-184; 17(1987), 185-206. 相似文献
6.
7.
Normal endothelin 1/2 levels and their correlation with age were evaluated. For clinical application of the endothelin 1/2 RIA test, optimum storage conditions were investigated. Plasma endothelin 1/2 (ET) levels were measured in 36 healthy blood donors, mostly males, of mean age 36 +/- 8 years, subdivided into three age groups: 17-30, 31-40 and above 40 years old. The mean normal ET levels in the three age groups, and corresponding standard deviations, were: 0.58 +/- 0.19, 0.62 +/- 0.31, and 0.80 +/- 0.28 fmol/ml, respectively. The mean ET level for the whole normal population was 0.66 +/- 0.28 fmol/ml. Only differences between mean ET levels for the first and last groups were statistically significant (p < 0.05). Differences between mean ET levels in smokers (53% of total population) and non-smokers, women and men, irrespective of age, were found not to be statistically significant. At this stage of our work, we conclude that other factors than age alone play a role in enhancing ET levels above the age of 41 years. In our study of optimum storage conditions for endothelin 1/2, we found that after one week of storage at -24 degrees C the mean level of ET measured in frozen plasma dropped to 85% of the initial activity, while after the same period the respective decrease in ET activity in frozen extracts was 49%. Over the next two weeks, ET levels in plasma and extracts dropped to 57% and 32% of "zero time" activities, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
8.
Rafael Navarro-González Cyril Ponnamperuma Raj K. Khanna 《Origins of life and evolution of the biosphere》1991,21(5-6):359-374
Cometary nuclei have been exposed to high levels of ionizing radiation since their formation. We present here some results of a computer model calculation of the effect of ionizing radiation on cometary material. The external (cosmic rays) and internal (embedded radionuclides) contributions in the processing of cometary nuclei are considered. As a first approximation we have used the available kinetic data of the liquid water system to model the radiation effects in a frozen cometary environment. Out data suggest that massive radiation chemical processing due to cosmic rays may have taken place only in the outer layers of comets. The internal contribution of radionuclides to the radiation processing of comet cores seems to be modest. Therefore, comets could be carriers of intact homochiral biomolecules.Part of this work was carried out during a leave at the Laboratory of Chemical Evolution. 相似文献
9.
Chromosome condensation activity in the cytoplasm of anucleate and nucleate fragments of mouse oocytes 总被引:3,自引:0,他引:3
The activity of maturation promoting factor (MPF) which causes chromosome condensation and subsequent oocyte maturation was investigated in mouse oocytes using polyethylene-glycol-mediated cell fusion technique. Fully grown oocytes were bisected at germinal vesicle (GV) stage or shortly after germinal vesicle breakdown (GVBD) into anucleate and nucleate fragments. After 2-3 or 15-17 hr of culture these fragments were fused with interphase blastomeres from two-cell embryos. It was found that almost all the anucleate oocyte fragments cultured for a short term (2-3 hr), regardless of whether they were produced at GV stage or after GVBD, induced premature chromosome condensation in the blastomere nuclei, whereas only about 20% of those cultured for a long term (15-17 hr) could do so. On the other hand, the nucleate fragments always retain the cytoplasmic activity to induce chromosome condensation. Thus we suggested that the MPF initially could appear in mouse oocytes independently of the GV, that the mixing of GV material with the oocyte cytoplasm following GVBD had no effect on the activity of MPF in anucleate fragments, and that oocyte chromosomes or some components associated with them could play a significant role in maintaining the MPF activity. 相似文献
10.
By means of the transmissive and scanning electron microscopy methods and radioautography, structure of mucous membrane of the stomach and duodenum has been studied under experimentally induced duodenal ulcers before and after vagotomy during various time. The vagotomy results in accelerated healing of the ulcer defect. This is connected with an increased proliferative activity in the crypta cells, however, this is accompanied with deceleration of their differentiation. Under the duodenal ulcers the amount of chief and parietal cells increases in the gastric mucous membrane, this depends on gastrostasis produced by stenosis of the pylorus. At vagotomy the amount of the chief and parietal cells in the fundal glands of the mucous membrane decreases; this is accompanied with a lowered secretory activity. 相似文献