全文获取类型
收费全文 | 25542篇 |
免费 | 1880篇 |
国内免费 | 4篇 |
出版年
2023年 | 237篇 |
2022年 | 195篇 |
2021年 | 601篇 |
2020年 | 471篇 |
2019年 | 518篇 |
2018年 | 966篇 |
2017年 | 794篇 |
2016年 | 986篇 |
2015年 | 1103篇 |
2014年 | 1221篇 |
2013年 | 1707篇 |
2012年 | 2032篇 |
2011年 | 2113篇 |
2010年 | 1231篇 |
2009年 | 960篇 |
2008年 | 1529篇 |
2007年 | 1462篇 |
2006年 | 1383篇 |
2005年 | 1070篇 |
2004年 | 1037篇 |
2003年 | 940篇 |
2002年 | 833篇 |
2001年 | 600篇 |
2000年 | 668篇 |
1999年 | 411篇 |
1998年 | 219篇 |
1997年 | 155篇 |
1996年 | 143篇 |
1995年 | 133篇 |
1994年 | 119篇 |
1993年 | 114篇 |
1992年 | 150篇 |
1991年 | 141篇 |
1990年 | 108篇 |
1989年 | 88篇 |
1988年 | 88篇 |
1987年 | 74篇 |
1986年 | 65篇 |
1985年 | 71篇 |
1984年 | 65篇 |
1983年 | 49篇 |
1982年 | 60篇 |
1981年 | 49篇 |
1980年 | 43篇 |
1979年 | 51篇 |
1978年 | 43篇 |
1977年 | 31篇 |
1975年 | 38篇 |
1974年 | 31篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Carlos Rico José Luis Rico Noelia Muñoz Beatriz Gómez Iñaki Tejero 《Engineering in Life Science》2011,11(5):476-481
The effect of mixing on biogas production of a 1.5‐m3 pilot continuous stirred tank reactor (CSTR) processing screened dairy manure was evaluated. Mixing was carried out by recirculation of reactor content with a mono pump. The experiment was conducted at a controlled temperature of 37±1°C and hydraulic retention times (HRTs) of 20 and 10 days. The effect of continuous and intermittent operation of the recirculation pump on biogas production was studied. At 10 days of HRT, the results showed a minimal influence of recirculation rate on biogas production and that continuous recirculation did not improve reactor performance. At 20 days of HRT, the recirculation rate did not affect reactor performance. Combination of low solid content in feed animal slurry and long HRTs results in minimal mixing requirements for anaerobic digestion. 相似文献
32.
33.
A Casta?eyra-Perdomo M M Pérez-Delgado T González-Hernández R Ferres-Torres 《Acta anatomica》1988,131(1):13-25
We have studied the karyometric development of the nuclei of the ependymal cells and neurons of the subfornical organ and the area postrema in the male albino mouse from the 5th to the 190th postnatal day. We have found similar patterns of development in both although the area postrema showed more significant postnatal oscillations than those of the subfornical organ, suggesting a more intimate chronological relationship to gonadal development. We have furthermore analyzed the development in two experimental groups: in the one animals were castrated at birth, in the other, castration was made on the 20th postnatal day. We have found that neonatal castration produced a significant decrease of nuclear sizes; this was more evident in the subfornical organ than in the area postrema in earlier stages of development while the response was similar in both at peripuberal ages. The response to prepuberal castration was similar in both organs. 相似文献
34.
35.
M Kwiatkowska K Pop?ońska A Gosek 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》1999,37(3):219-221
Autoradiographic research with the use of 3H-leucine demonstrates that circadian rhythm of protein synthesis characteristic of manubria at the proliferative phase of spermatogenesis in Chara vulgaris disappears after symplasmic isolation of antheridium from thallus during the time preceding block of DNA endoreplication in manubria following initiation of spermiogenesis insensitive to light. 相似文献
36.
37.
Effects of ethanol and other alkanols on passive proton influx in the yeast Saccharomyces cerevisiae
Ethanol, isopropanol, propanol and butanol enhanced the passive influx of protons into deenergized cells of Saccharomyces cerevisiae. The influx followed first-order kinetics with a rate constant that increased exponentially with the alkanol concentration. The exponential enhancement constants increased with the lipid solubility of the alkanols, which indicated hydrophobic membrane regions as the target sites. While the enhancement constants were independent of pH over the range tested (3.3–5.0), the rate constants decreased linearly with increasing extracellular proton concentration, indicating the presence of an additional surface barrier against proton penetration, the effectiveness of which increased with protonation. The alkanols affected the acidification curves of energized yeast suspensions in such a way that the final pH values were linear functions of the alkanol concentrations. These results were consistent with a balance between active and passive proton movements at the final pH, the exponential enhancement constants calculated from the slopes being nearly identical with those obtained with deenergized cells. It was concluded that passive proton influx contributes to the kinetics of acidification in S. cerevisiae and that uncoupling contributes to the overall kinetics of alkanol-inhibited secondary active transport across the yeast plasma membrane. 相似文献
38.
39.
Javier Mar Arantzazu Arrospide José María Begiristain Isabel Larrañaga Elena Elosegui Juan Oliva-Moreno 《BMC neurology》2011,11(1):46
Background
Patients with acquired brain damage (ABD) have suffered a brain lesion that interrupts vital development in the physical, psychological and social spheres. Stroke and traumatic brain injury (TBI) are the two main causes. The objectives of this study were to estimate the incidence and prevalence of ABD in the population of the Basque Country and Navarre in 2008, to calculate the associated cost of the care required and finally to assess the loss in health-related quality of life. 相似文献40.
Francisco J Gálvez-Gastélum Aida A Segura-Flores María D Senties-Gomez Jose F Muñoz-Valle Juan S Armendáriz-Borunda 《Journal of biomedical science》2010,17(1):42