全文获取类型
收费全文 | 455633篇 |
免费 | 49903篇 |
国内免费 | 310篇 |
出版年
2018年 | 4276篇 |
2017年 | 4269篇 |
2016年 | 5846篇 |
2015年 | 7984篇 |
2014年 | 9232篇 |
2013年 | 13357篇 |
2012年 | 15117篇 |
2011年 | 15108篇 |
2010年 | 10016篇 |
2009年 | 9095篇 |
2008年 | 13489篇 |
2007年 | 13706篇 |
2006年 | 13193篇 |
2005年 | 12483篇 |
2004年 | 12343篇 |
2003年 | 11824篇 |
2002年 | 11656篇 |
2001年 | 20204篇 |
2000年 | 20423篇 |
1999年 | 16567篇 |
1998年 | 5934篇 |
1997年 | 6108篇 |
1996年 | 5900篇 |
1995年 | 5377篇 |
1994年 | 5509篇 |
1993年 | 5356篇 |
1992年 | 13614篇 |
1991年 | 13038篇 |
1990年 | 12928篇 |
1989年 | 12844篇 |
1988年 | 11720篇 |
1987年 | 11132篇 |
1986年 | 10351篇 |
1985年 | 10354篇 |
1984年 | 8440篇 |
1983年 | 7375篇 |
1982年 | 5657篇 |
1981年 | 5029篇 |
1980年 | 4818篇 |
1979年 | 8100篇 |
1978年 | 6271篇 |
1977年 | 5545篇 |
1976年 | 5365篇 |
1975年 | 5855篇 |
1974年 | 6092篇 |
1973年 | 6006篇 |
1972年 | 5480篇 |
1971年 | 4860篇 |
1970年 | 4263篇 |
1969年 | 3992篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
T. R. FRASIER T. RASTOGI M. W. BROWN P. K. HAMILTON S. D. KRAUS B. N. WHITE 《Molecular ecology resources》2006,6(4):1025-1029
A North Atlantic right whale (Eubalaena glacialis) genomic library was developed and screened with a (GATA)8 probe to identify tetranucleotide microsatellite loci. Sixteen characterized loci were polymorphic in North Atlantic and/or South Atlantic (Eubalaena australis) right whales, 12 being polymorphic in E. glacialis, and 15 in E. australis. Fourteen of these were combined with 21 other previously identified loci for a suite of 35 loci which can be used to increase resolution of genetic analyses of these species. Multiplex reactions were developed for genotyping samples at these loci, providing a method that is rapid, reliable and cost‐effective. 相似文献
992.
Tobias Consmüller Antonius Rohlmann Daniel Weinland Claudia Druschel Georg N. Duda William R. Taylor 《PloS one》2012,7(11)
The importance of functional parameters for evaluating the severity of low back pain is gaining clinical recognition, with evidence suggesting that the angular velocity of lordosis is critical for identification of musculoskeletal deficits. However, there is a lack of data regarding the range of functional kinematics (RoKs), particularly which include the changing shape and curvature of the spine. We address this deficit by characterising the angular velocity of lordosis throughout the thoracolumbar spine according to age and gender. The velocity of lumbar back shape changes was measured using Epionics SPINE during maximum flexion and extension activities in 429 asymptomatic volunteers. The difference between maximum positive and negative velocities represented the RoKs. The mean RoKs for flexion decreased with age; 114°/s (20–35 years), 100°/s (36–50 years) and 83°/s (51–75 years). For extension, the corresponding mean RoKs were 73°/s, 57°/s and 47°/s. ANCOVA analyses revealed that age and gender had the largest influence on the RoKs (p<0.05). The Epionics SPINE system allows the rapid assessment of functional kinematics in the lumbar spine. The results of this study now serve as normative data for comparison to patients with spinal pathology or after surgical treatment. 相似文献
993.
The multivariate phenetic approach to the classification of Salmo spp. samples from Serbia and adjacent regions of western Balkans for 22 continuous external morphological characters suggests the occurrence of the following distinct stocks: West Danubian (Crno Osoje Stream and upper Zeta River) Salmo taleri , marble trout Salmo marmoratus (Trebuščica River), hatchery-reared Atlantic Salmo trutta , Mlava River drainage (Mlava and Krupaja rivers and Buk Stream) trout Salmo cf. trutta , Velika Morava River system (Godljevača, Bela and Resava rivers) trout S. cf. trutta , Ohrid Lake belvica Salmo ohridana and Aegean coastal drainage Salmo macedonicus (Božica River). In contrast to the phenetic similarity, the phylogenetic reconstruction places the Lake Ohrid belvica as part of an unresolved polytomy with other trout groups. Salmo cf. trutta in the Mlava River appears to form the basal group for the trout species in the region. The position of marble trout implies its independent and more recent origin from the West Danubian trout stock. 相似文献
994.
Acquisition of Resistance to Extended-Spectrum Cephalosporins by Salmonella enterica subsp. enterica Serovar Newport and Escherichia coli in the Turkey Poult Intestinal Tract 下载免费PDF全文
995.
996.
997.
998.
999.
The free carboxyl group of hypermodified nucleosides N6-methyl-N6-(threoninocarbonyl)adenosine (mt6A37) and 3-(3-amino-3-carboxypropyl)uridine (acp3U20:1) in tRNAmMet (yellow lupine), and N6-(threoninocarbonyl)adenosine (t6A37) in tRNAiMet (yellow lupine) can be converted quantitatively and under very mild conditions into the respective anilides in a reaction with aniline and a water-soluble carbodiimide. The tRNA reactions proceed with rates very similar to that reported previously for t6A nucleoside. Detailed analysis of the products of tRNA modification with [3H]aniline on tRNA (chromatography on BD-DEAE-cellulose), oligonucleotide (polyacrylamide gel electrophoresis) and nucleoside (HPLC on Aminex A6) levels clearly indicates that only the hypermodified nucleoside residues undergo the reaction. The site of modification is confirmed for mono-modified (at mt6A37) and bis-modified (at mt6A37 and acp3U20:1) tRNAmMet, and for mono-modified (at t6A37) tRNAiMet by sequence analysis using 5'end 32P-labeled tRNAs. The modification procedure seems to be universally applicable for all hypermodified nucleosides bearing a free carboxyl group and for different amine reagents designed for the studies on tRNA function. 相似文献
1000.
Abstract.The stimuli and mechanisms mediating host location and host choice by the bee mite, Varroa jacobsoni (Oudemans), are currently unknown. It is shown that Varroa can use single clean‐air puffs and bee‐odour plumes in a wind tunnel as directional cues. Varroa turned nearly straight upwind in response to single 0.1‐s puffs of clean air directed at 90° to the their anterior‐posterior axis. They turned significantly further to their left side (104°) than to their right (76°), but showed no difference in latency to initiation of the turns (means of 63.3 ms vs. 62.6 ms, respectively). They also followed bee‐odour plumes in a wind tunnel. When released in odour and control plumes mid‐way between the plume's origin and the downwind end of the tunnel, mites responding to bee‐odour walked upwind in, or along the edge of, the odour plume with 38% making contact with the odour delivery tube; mites in clean air did not walk upwind along the air stream, and none made contact with the air delivery tube. Walking speeds were not different between the bee‐odour and control groups (0.28 vs. 0.29 cm s–1 ); there were also no differences in the turning rates (96.85 vs. 97.16 deg s–1 and 388.08 vs. 379.18 deg cm–1 , respectively). Under all conditions, mites walked in a zigzag fashion. 相似文献