全文获取类型
收费全文 | 3515篇 |
免费 | 294篇 |
国内免费 | 2篇 |
专业分类
3811篇 |
出版年
2023年 | 24篇 |
2022年 | 44篇 |
2021年 | 94篇 |
2020年 | 76篇 |
2019年 | 65篇 |
2018年 | 110篇 |
2017年 | 81篇 |
2016年 | 157篇 |
2015年 | 190篇 |
2014年 | 201篇 |
2013年 | 250篇 |
2012年 | 303篇 |
2011年 | 261篇 |
2010年 | 182篇 |
2009年 | 135篇 |
2008年 | 214篇 |
2007年 | 209篇 |
2006年 | 166篇 |
2005年 | 162篇 |
2004年 | 143篇 |
2003年 | 134篇 |
2002年 | 115篇 |
2001年 | 43篇 |
2000年 | 27篇 |
1999年 | 40篇 |
1998年 | 25篇 |
1997年 | 29篇 |
1996年 | 28篇 |
1995年 | 27篇 |
1994年 | 21篇 |
1993年 | 28篇 |
1992年 | 26篇 |
1991年 | 15篇 |
1990年 | 21篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1973年 | 5篇 |
1970年 | 7篇 |
1958年 | 3篇 |
1944年 | 3篇 |
排序方式: 共有3811条查询结果,搜索用时 0 毫秒
1.
2.
R.E. Jonkers B. Oosterhuis R.J.M. Ten Berge C.J. Van Boxtel 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,233(1):249-255
A relatively simple assay with improved reliability and sensitivity for measuring levels of 6-mercaptopurine in human plasma is presented. After extraction of the compound and the added internal standard with phenyl mercury acetate, samples were separated by ion-pair reversed-phase high-performance liquid chromatography. On-line the analytes were oxidized to fluorescent products and detected in a flow-fluorimeter. The within-day coefficient of variation was 3.8% at a concentration of 25 ng/ml. The lower detection limit was 2 ng/ml when 1.0 ml of plasma was used. Mercaptopurine concentration versus time curves of two subjects after a single oral dose of azathioprine are shown. 相似文献
3.
4.
First appearing in 2000, and with 20,000 copies sold as it entered its sixth printing in 2004, Richard Trudgen's Why Warriors Lie down and Die is a minor publishing phenomenon. Although scholarly forums have generally ignored the book, Christian media outlets, the popular press and neo‐conservative political activists have enthusiastically received and promoted it. An examination of the merits of Why Warriors Lie down and Die suggests that its popularity is only partly explained by original observations or insights on the part of the author. The most important explanation, and implication, of the book's remarkable take‐up lies in the opportune way in which it corresponds with now ascendant neo‐conservative political perspectives on indigenous policy. 相似文献
5.
6.
Kate Jolly 《BMJ (Clinical research ed.)》1991,303(6804):716-717
7.
Controlled generation of reactive oxygen species orchestrates numerous physiological signaling events (Finkel, T. (2011) Signal transduction by reactive oxygen species. J. Cell Biol. 194, 7–15). A major cellular target of reactive oxygen species is the thiol side chain (RSH) of Cys, which may assume a wide range of oxidation states (i.e. −2 to +4). Within this context, Cys sulfenic (Cys-SOH) and sulfinic (Cys-SO2H) acids have emerged as important mechanisms for regulation of protein function. Although this area has been under investigation for over a decade, the scope and biological role of sulfenic/sulfinic acid modifications have been recently expanded with the introduction of new tools for monitoring cysteine oxidation in vitro and directly in cells. This minireview discusses selected recent examples of protein sulfenylation and sulfinylation from the literature, highlighting the role of these post-translational modifications in cell signaling. 相似文献
8.
Jason L. Schamber James S. Sedinger David H. Ward Kate R. Hagmeier 《Journal of Field Ornithology》2007,78(1):74-82
ABSTRACT. Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups. 相似文献
9.
10.
Frits Th. M. Spieksma Joop F. den Tonkelaar 《International journal of biometeorology》1986,30(4):351-358
Four-hourly volumetric measurements of airborne grass-pollen concentrations at Leiden, near the west coast of the Netherlands, were analyzed according to wet-versus-dry meteorological conditions in the pollen source area, and according to the distance of the over-land advection to the pollen sampler. Airborne pollen concentrations appear to be low when the source surface is wet by past or present rain, fog, or dew; and high when the source area is dry. Air adverted over long over-land distances from dry source areas contains much pollen, especially in the afternoon, due to pollen release and decreasing air turbulence. High nightly pollen concentrations are observed after a warm and dry day with much pollen release in distant source areas when the nocturnal meteorological conditions stimulate concentration of pollen grains into the lower layers of the atmosphere.Presented at the Sixth International Palynological Conference, 26 August – 1 September 1984, Calgary, Canada. 相似文献