全文获取类型
收费全文 | 502192篇 |
免费 | 59595篇 |
国内免费 | 230篇 |
出版年
2018年 | 4426篇 |
2017年 | 4307篇 |
2016年 | 6037篇 |
2015年 | 8873篇 |
2014年 | 10167篇 |
2013年 | 15079篇 |
2012年 | 16504篇 |
2011年 | 16981篇 |
2010年 | 11425篇 |
2009年 | 10769篇 |
2008年 | 15096篇 |
2007年 | 15531篇 |
2006年 | 14517篇 |
2005年 | 14145篇 |
2004年 | 13803篇 |
2003年 | 13428篇 |
2002年 | 13045篇 |
2001年 | 20728篇 |
2000年 | 20730篇 |
1999年 | 16642篇 |
1998年 | 6492篇 |
1997年 | 6735篇 |
1996年 | 6433篇 |
1995年 | 6216篇 |
1994年 | 6095篇 |
1993年 | 6257篇 |
1992年 | 14238篇 |
1991年 | 14042篇 |
1990年 | 13414篇 |
1989年 | 13402篇 |
1988年 | 12186篇 |
1987年 | 11908篇 |
1986年 | 11073篇 |
1985年 | 11171篇 |
1984年 | 9576篇 |
1983年 | 8221篇 |
1982年 | 6705篇 |
1981年 | 6113篇 |
1980年 | 5850篇 |
1979年 | 8827篇 |
1978年 | 7294篇 |
1977年 | 6728篇 |
1976年 | 6418篇 |
1975年 | 6861篇 |
1974年 | 7038篇 |
1973年 | 6800篇 |
1972年 | 6025篇 |
1971年 | 5588篇 |
1970年 | 4741篇 |
1969年 | 4543篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Characteristics of morphology and number of melanomacrophage centers (MMCs) in the liver and spleen of the roach Rutilus rutilus and the amount of pigments in MMCs during the Haff disease outbreak and the death of fish in Lake Kotokel in relation to these parameters in the roach from Lake Baikal are described. Pathological changes in the microvasculature and parenchyma in the liver of the roach from Lake Kotokel were found. The area of melanomacrophage centers in the liver of the roach from this lake was significantly smaller, whereas the number and size of these centers in the spleen was significantly larger than in the roaches from Lake Baikal. Among the pigments studied, the strongest response to the content of this toxin in the water body was shown by hemosiderin. An increase in its amount in the spleen MMCs testifies to an enhanced degradation of erythrocytes and iron release, which may be caused by the damage of cells of the erythrocyte lineage by the toxin. 相似文献
2.
3.
4.
5.
Richard John Wheeler 《Molecular biology of the cell》2015,26(22):3898-3903
Tools to analyze cyclical cellular processes, particularly the cell cycle, are of broad value for cell biology. Cell cycle synchronization and live-cell time-lapse observation are widely used to analyze these processes but are not available for many systems. Simple mathematical methods built on the ergodic principle are a well-established, widely applicable, and powerful alternative analysis approach, although they are less widely used. These methods extract data about the dynamics of a cyclical process from a single time-point “snapshot” of a population of cells progressing through the cycle asynchronously. Here, I demonstrate application of these simple mathematical methods to analysis of basic cyclical processes—cycles including a division event, cell populations undergoing unicellular aging, and cell cycles with multiple fission (schizogony)—as well as recent advances that allow detailed mapping of the cell cycle from continuously changing properties of the cell such as size and DNA content. This includes examples using existing data from mammalian, yeast, and unicellular eukaryotic parasite cell biology. Through the ongoing advances in high-throughput cell analysis by light microscopy, electron microscopy, and flow cytometry, these mathematical methods are becoming ever more important and are a powerful complementary method to traditional synchronization and time-lapse cell cycle analysis methods. 相似文献
6.
7.
Charles A. Kunos Jeffrey M. Fabien John P. Shanahan Christine Collen Thierry Gevaert Kenneth Poels Robbe Van den Begin Benedikt Engels Mark De Ridder 《Journal of visualized experiments : JoVE》2015,(100)
Physicians considering stereotactic ablative body radiation therapy (SBRT) for the treatment of extracranial cancer targets must be aware of the sizeable risks for normal tissue injury and the hazards of physical tumor miss. A first-of-its-kind SBRT platform achieves high-precision ablative radiation treatment through a combination of versatile real-time imaging solutions and sophisticated tumor tracking capabilities. It uses dual-diagnostic kV x-ray units for stereoscopic open-loop feedback of cancer target intrafraction movement occurring as a consequence of respiratory motions and heartbeat. Image-guided feedback drives a gimbaled radiation accelerator (maximum 15 x 15 cm field size) capable of real-time ±4 cm pan-and-tilt action. Robot-driven ±60° pivots of an integrated ±185° rotational gantry allow for coplanar and non-coplanar accelerator beam set-up angles, ultimately permitting unique treatment degrees of freedom. State-of-the-art software aids real-time six dimensional positioning, ensuring irradiation of cancer targets with sub-millimeter accuracy (0.4 mm at isocenter). Use of these features enables treating physicians to steer radiation dose to cancer tumor targets while simultaneously reducing radiation dose to normal tissues. By adding respiration correlated computed tomography (CT) and 2-[18F] fluoro-2-deoxy-ᴅ-glucose (18F-FDG) positron emission tomography (PET) images into the planning system for enhanced tumor target contouring, the likelihood of physical tumor miss becomes substantially less1. In this article, we describe new radiation plans for the treatment of moving lung tumors. 相似文献
8.
Ronac Mamtani James D. Lewis Frank I. Scott Tariq Ahmad David S. Goldberg Jashodeep Datta Yu-Xiao Yang Ben Boursi 《PLoS medicine》2016,13(4)
BackgroundSeveral prior studies have found an association between statin use and reduced risk of colorectal cancer. We hypothesized that these findings may be due to systematic bias and examined the independent association of colorectal cancer risk with statin use, serum cholesterol, and change in cholesterol concentration.ConclusionsAlthough the risk of colorectal cancer was lower in statin users versus nonusers, no difference was observed among those who continued versus discontinued statin therapy, suggesting the potential for indication bias. The association between decreased serum cholesterol and colorectal cancer risk suggests a cholesterol-lowering effect of undiagnosed malignancy. Clinical judgment should be used when considering causes of cholesterol reduction in patients, including those on statin therapy. 相似文献
9.
Joyce S. F. D. de Almeida Teobaldo R. Cuya Guizado Ana P. Guimarães Teodorico C. Ramalho Arlan S. Gonçalves Martijn C. de Koning 《Journal of biomolecular structure & dynamics》2016,34(12):2632-2642
In the present work, we performed docking and molecular dynamics simulations studies on two groups of long-tailored oximes designed as peripheral site binders of acetylcholinesterase (AChE) and potential penetrators on the blood brain barrier. Our studies permitted to determine how the tails anchor in the peripheral site of sarin-inhibited human AChE, and which aminoacids are important to their stabilization. Also the energy values obtained in the docking studies corroborated quite well with the experimental results obtained before for these oximes. 相似文献
10.